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Which is the better design and why?
ED, EF, DA etc. single arm front LCA + castor rod
OR
EG, DC, EK etc. A arm front LCA
Which do you think is better and why?
What are the pro's & con's of each design?
I'm biased and don't like late model strut based front suspension from Honda.
where does DC2R fit into this?
Quote:
Originally Posted by yourfather
thereQuote:
Originally Posted by Bludger
Macpherson strut with A arm LCA. It is the awesome. Didn't vote because there wasn't an option for me :p.
I voted radius rods because they are easily replaced with a spherical and can be adjusted for castor in a much wider range without binding than the EG/DC arms with 2 bushings. I am also biased because I've owned 3 DA's :D
In terms of performance they will be very similar. I can't back this up but I believe the EG/DC suspension is mounted higher on the chassis than the DA so you can get the centre of gravity (CG) lower without running out of suspension travel. When your tyre is lowered to the guard (tiny gap) you have maybe 2cm of space between the upper control arm and the fender wall. Not good...
With no radius rod you probably don't need a very big front cross-member. I've never seen a EG/DC front cross-member but I imagine it is smaller than the DA's. Moving weight closer to the CG is always a good thing.
A likely possibility is that the EG/DC lower A-arm is cheaper to produce and they simply want to save money. They've (and any other business you can name) done it before; DC5 Macpherson Struts a perfect example. Another is the new Civics with their terrible rear suspension. Money money money.
yeah, just cos you have a dc5:p:thumbdwn::wave:Quote:
Originally Posted by chargeR
Honda torsion beam FTL, as well as every other manufacturer....Quote:
Originally Posted by string
good point about moving weight rearward to center, never thought of that, and no, eg/ek/dc's don't have a front cross-member at all.
Any of the SLA ('double wishbone') front suspensions will in principle be superior to the Mac Strut. Having said this, a sensibly modded Mac Strut will be superior to a poorly modded (or designed) SLA suspension, but all else being equal the SLA will be better out of the box (typically, but the Devil is in the detail), and have more scope for improvement, especially for a FWD car.Quote:
Originally Posted by chargeR
Mac Struts are a very compromised design, but do have advantages in that they are compact (easier to package into the chassis due to lack of upper wishbone), they are robust, they are lightweight, and they are relatively cheap to make.
Did I say they were cheap?
On the other hand Mac Struts don't change camber enough with suspension motion (which makes them very sensitive to body roll causing substantial unwanted camber change relative to the road surface), the caster angle unavoidably changes with suspension motion, the damper is subject to quite substantial internal loadings that are the result of lateral forces and braking forces being reacted within the damper body (between the piston and the damper tube wall).
This latter problem isn't an issue for SLA suspensions because all forces (other than vertical ones which the damper is well suited to dealing with) are reacted through the upper part of the suspension 'upright' (aka 'knuckle' etc) and in the upper wishbone (not in the damper), but with a Mac Strut the damper body and rod are forced to act as if they were the suspension upright....
Mac Struts are not well suited to wider tyres due to the limited camber change, and tend to require excessive static neg camber angles to compensate for this (more so with wider rubber), but this causes other problems...
Even with substantial static neg camber this does not really make up for the geometric deficiencies of a Mac Strut, just alleviates them somewhat by maximising the lateral grip of the outside front contact patch (i.e. pre existing static neg camber helping to keep the OF wheel near vertical when cornering hard) at the expense of the inside front contact patch, which ends up being very small with a very substantial dynamic camber causing the tyre to be running on it's very inner edge.
Sure, Porsche use Mac Struts on the 911, but on these cars not much is really asked of the front end, all (most of) the lateral and longitudinal traction action occurs at the back end due to the heavily rearward weight bias and the need for rear traction dictating a relatively very roll stiff front end that unloads the inside front wheel very substantially when cornering (thus the dynamic camber angle and grip of the IF is laregely irrelevant...).
Now for a FWD car we need to keep the inside front contact patch planted heavily on the ground (i.e. low front roll stiffness relative to rear roll stiffness) and presented as 'squarely' to the road as we can manage in order to maximise it's grip in order to minimise understeer and maximise traction exiting corners. This is not acheived if we allow the IF to lean over at drunken angles with only it's inner edge in road contact, yet this is what we are more or less forced to do when setting up a Mac Strut for 'high performance' applications.
When trying to get the most out of a Mac Strut design, we can't really make a silk purse out of a pig's ear (Mac Strut = pig's ear), at best we can make a purse that looks a lot less pig's ear-like than it actually is...
Note that for all purpose designed modern race cars (not racers made out of modded road cars), SLA is the suspension of choice at every corner of every car...
LOL
was waiting for your post:thumbsup::p
but you didn't make much comment of the two suspension designs compared in this thread:(
Where is the AH suspension systems Bau?
Where?
Not saying I'd vote for it but its something to consider.
Would be nice to have the A arms with radius rods.
I guess that is possible by getting hold of one of the many brands of traction bars.
*rubs Torsion Bars*
I couldn't let that statement stand. I just don't like Mac Struts, they aren't 'nice' engineering. If it weren't nearly impossible to design a beam axle with a low enough roll centre, a front beam axle might even be a better bet than a Mac Strut.Quote:
Originally Posted by Bludger
That's because I'm not all that familiar with the detail of these different suspensions.Quote:
Originally Posted by Bludger
I have to assume that one basic design is similar to that of my CB7 Accord, in having a radius rod forming the forward part of the lower 'wishbone', and the other is like that in my nephew's EG Civic, having a lower control arm rigidly attached to and in front of another substantial forging, these two forged components forming the lower 'wishbone'??
If so then as a matter of principle I prefer the radius rod design because the radius rod is loaded only in tension / compression and as a result is reasonably light (less unsprung mass, always good). On the other hand the heavier forged leading arm of the EG Civic style wishbone (from memory) seems to be largely loaded in 'bend', and relies upon it's rigidity in bend to resist deflection of the wishbone (which will be most highly loaded under heavy braking).
This is because the second forging is shaped to allow clearance of the tyre when the inside wheel is turned to it's fullest extent. To make a steel component rigid in bend requires it to be rather substantially massive, or of a rather substanially proportioned hollow section. I suspect that despite it's size, this forging possibly won't be stiff enough to give as high a resistance to deflection as the radius rod probably will...
The problem is that it's hard to package a simple and lightweight radius rod behind the LCA because it will interfere with the amount of steering lock that is possible when the inside wheel is turned, i.e. before it's been steered all that far the inside front wheel will come into contact with a straight radius rod located behind the LCA because the inside wheel needs to turn much more than then outside wheel (because of Ackermann geometry).
The only ways to avoid this are to minimise the Ackermann geometry, minimise steering lock (and thus maximise the turning circle), to attach the radius rod to the LCA half way along it's length instead of nearer the outer end of the LCA (which will massively increase loadings on both the LCA and the radius rod), to reduce the distance between the points at which the LCA and radius rod attaches to the chassis (which will increase loadings on the radius rod), or most practically to use a substantially robust forging shaped to clear the fully turned inside wheel as a substitute for a radius rod.
When using a lightweight straight radius rod, it's easier for steering clearance if the radius rod is located in front of the LCA. The only downside is that a substantially rigid location must be provided for the attachment of the front ends of the radius rods, meaning that a more robust front cross member must be fitted.
Great post! "You must spread some Reputation around before giving it to JohnL again." ;). It is good to read an accurate comment on the Macpherson strut suspension not simply the "New hondas have Mcstrut suspension so they are automatically crap" mentality that seems to be prevalent.Quote:
Originally Posted by JohnL
DC5 front suspension works okay despite being Mcpherson strut and a quite poorly designed one at that. Care to come to the track to compare the relative merits of each suspension architecture? :pQuote:
Originally Posted by Bludger
I agree totally, Macpherson struts are just a cost cutting thing.Quote:
Originally Posted by JohnL
Interesting points you pointed out there John, my assumptions have always been that the A arms were a better design from Honda solely because they just appeared to be more beefier and stronger than the counterpart. Taking into consideration the forces applied to the LCA's when accelerating & braking, I still would have thought that the A arms would be able to handle the forward/rearward forces better. But I think someone with your background would have a more credible point of view than one coming from me. So I'll take your word for it that the Radius rod design is better.
Would love to be able to see a scientific experiment testing and deciding conclusively which is better.
Thanks
Not "crap", just compromised, and a pity considering that older Hondas were fitted with a superior / more sophisticated design, so the cruder Mac Strut represents a backward step from Honda.Quote:
Originally Posted by chargeR
It is always surprising that Mac Struts can be made to work as well as they can be made to work, but I suspect much of this is down to the ability of modern high performance tyres to overcome suspension deficiencies (up to a point).
You said it; "works okay despite being Mcpherson strut". All else being equal, if it were an equally well sorted SLA it would be better.Quote:
Originally Posted by chargeR
Who would we get to ensure that all the other pieces of string were equally long?Quote:
Originally Posted by chargeR
I think the issue is that the earlier double wishbone hondas have a great, well developed suspension design compared to most other FWD cars. The sector of the car market that FWD hondas seem to occupy is generally filled with cheap and easy Macpherson struts and torsion beams and the EGs and their like seem like a bit of an oddity. Now that Honda has begun cheaping out and blessing us with simpler and cheaper suspension structures, the performance of which the general consumer will be unable to seperate from the earlier designs, we are right to complain :).Quote:
Originally Posted by JohnL
Undoubtedly. But all cars have their flaws for performance use, but particularly production cars. And if one is forced to use a production car, who is to say whether the advantages of some of the platforms fitted with McStrut suspension will or will not outweight the disadvantage inherent in the suspension?Quote:
Originally Posted by JohnL
Why try to make the competition fair, I am already at a significant disadvantage ;).Quote:
Originally Posted by JohnL
Awesome info JohnL , what is your background?
And is this the reason why my DA Integra doesnt have the turning circle of my Wife's EG?
The really big money question is though, when I sell my DA and upgrade, is a DC2R going to be a better handling car than an EP3R Civic (my two choices)
Cheers
Chris
according to what John has just said, the radius rod design would have more ability to have a greater turning circle than the A arm.Quote:
Originally Posted by tseesinngwailo
so DA should have more than the EG.
might not be the case in practise.
Also as said, if all being equal, double wishbone setup over Macpherson struts.
so dc2r > ep3r
Sad but true. Not that Mac Struts are necessarily a bad thing for the average shopping trolley, a perfectly suitable design for such an application...Quote:
Originally Posted by Bludger
The problem is the shape of the forging, i.e. it's effectively bent, forces can't pass through it in a straight line. Any time a member has a bend in it, it needs to be much more substantial in order to adequately resist forces as they 'negotiate' that bend, i.e. any bend creates a weakness that will often require a very large increase in the mass or size of that member to match the rigidity of a straight member.Quote:
Originally Posted by Bludger
Keep in mind too that the greatest loading these members will ever see (short of a crash loading) are going to be the forces created by heavy braking. Due to being in front of the contact patch, the radius rod will 'see' this force as a tensile force attempting to stretch it, and will be able to resist such a force very easily (how much weight could hang from a bar that thick, with effectively zero stretching of that bar? quite a substantial amount I'd suggest).
Due to being behind the contact patch, the forged component of the other design will 'see' a braking force as a compression that is attempting to increase the bend which already exists in the forging. It may well be strong enough to not flex a great deal under this loading, but it will inevitably flex to some degree.
The forging may possibly be nearly as rigid under heavy braking as the radius rod, but if so then it's much heavier to achieve it (which isn't likely to be a significant issue for a road car, and only a minor one for a racer). I doubt there's actually much to choose between the two different approaches to the lower wishbone design, until braking forces start becoming very substantial...
A well designed suspension compared to most other cars period, FWD / RWD or 4WD, better than BMW for instance. Honda really pioneered this style of SLA suspension (with the very tall upright), it has been copied since.Quote:
Originally Posted by chargeR
That's the problem, Honda was competing on price against other more or less similar cars (at least similar to those who don't appreciate or care about the finer points of Honda engineering) that had cheaper suspensions. Honda had a better suspension but this meant nothing to 99% of their potential customers.Quote:
Originally Posted by chargeR
Even the typical more 'sporting' driver has little understanding of the superiority of the SLA over the Mac Strut, which are now so ubiquitous that most expect no better. Frankly, with modern tyres at relatively moderate speeds, most of the time it would be hard to tell the difference between an SLA and a Mac Strut suspension, at least you'd be hard pressed to tell any difference on the typical test drive.
My experience of Hondas with SLA suspensions (other than the more sporting variants such as the various Type Rs of which I have no experience) is that while the basic suspension design is terrific, the affect is somewhat spoiled by the very soft spring / damper rates, and the tiresome understeery not very responsive set up. They are however an exceptional basis for improvement.Quote:
Originally Posted by chargeR
There are some hidden weaknesses in some, e.g. the rear anti roll bar attachments (chassis and suspension) on my CB7 are (were) unacceptably flexible and have had to be replaced with stiffer items or other wise modified.
From a performance perspective, any chassis needs to be only two things; light and rigid. A light / rigid chassis with Mac Struts may well be a better choice than a car with SLA suspension but is heavy and not so rigid. It's all a compromise, picking the best compromise is the challenge.Quote:
Originally Posted by chargeR
Chris,Quote:
Originally Posted by tseesinngwailo
My interest in chassis dynamics started when I was racing karts and also designing kart chassis (from first principles) that were in detail not quite like any other kart chassis (project abandoned due to lack of funds).
And yes, karts do have suspensions, it's just that they lack discreetly defined articulations as cars conveniently have. The laws of physics apply in exactly the same manner with karts as they do with cars (or trucks...etc), it's just that the manner in which car and kart design exploit the physics varies in detail. Other than this I'm just an amatuer who's read widely and given this sort of stuff a lot of thought...
There could be clearance issues other than the exact stlye of LCA longitudinal location.Quote:
Originally Posted by tseesinngwailo
I can't possibly say, I have no familiarity with these particular cars.Quote:
Originally Posted by tseesinngwailo
I will say that just because car A has an SLA suspension and car B has Mac Struts, it doesn't necessarily follow that car A is the better handling car, there are too many variables involved to make such a prediction. It would however IMO be reasonably safe to assume that car B has the greatest potential to be made into the best handling car, if it isn't already...
The fact that the EG has the longitudinal locating member behind the LCA in principle tends to limit how far the inside wheel can be steered, but, it also depends on just how much clearance is built into any effective 'bend' in this forging.Quote:
Originally Posted by Bludger
It also depends on the inward angle of the radius rod for the other design, and whether or not there are other unrelated clearance issues. The devil is always in the detail, but steering lock is very often limited by clearance of the tyre sidewall to other parts of the car at the inside wheel because Ackermann geometry causes the inside wheel to be steered substantially more than the outside wheel.
Chris, not forgetting lowering and Rim/Tyre size does affect handling aswell.Quote:
Originally Posted by tseesinngwailo
Thanks for the info JohnL, this is exactly why I love a forum like this, every 1000 stupid posts threads about nothing get forgotten when something as infomative as this is posted.
I am still not sure what car I will upgrade to, as I love the DC2R, but if I can stretch my budget, I want an EP3, I doubt both cars will ever be pushed to their limits.
Cheers, Chris
Autocross racing in the states was dominated by the EG/EK civics until the MX5 came along.
I suspect there's more than one Mini2 doing well now.
Those are my candidates for excellent road vehicle suspensions.
Proof mac strut can run it with SLA suspension, just not on a Camry
Nick.
PS. 98 CRVs had SLA arms like EG/EKs but don't try to take a hairpin turn in those. Proof that SLA isn't the bees knees either.
any properly set up FWD will be able to be steered through a corner by using oversteer/understeer, via the throttle.Quote:
Originally Posted by tank
Stop spreading misinformation, FWD cars are understeering pigs and cannot be driven fast :p.Quote:
Originally Posted by Bludger
Haha, agreed about the Ignis Sport. The current Swift Sport is very similar on the limit. I have driven both of them. Sometimes its not always about the ultimate laptime.Quote:
Originally Posted by tank
As for all the talk about suspensions, besides real cars, racing RC touring cars will teach you alot. I've been racing RC cars (track grip racing, none of the RC drifting nonsense) for close to a decade, and current generation RC touring cars have near infinite suspension adjustments. roll centres, anti-squat, anti-dive, camber, caster, steering ackermann, toe, camber gain, damper bump and rebound, springs,down stops, ride height, anti-roll bars all are tunable.
Need proof? Download and read through the X-Ray setup guide book here for a detailed rundown on chassis and suspension tuning in 1/10 scale, with much of it portable to 1/1 scale:
http://www.teamxray.com/teamxray/sho...p?file_id=6143
RC drivers at the pointy end of the field are chasing tenths of seconds, and I've learnt more about suspension tuning and geometry on the RC track than anywhere else.
Having race engineered EF, EG, EK DC2 and DC5’s I am in absolutely no doubt that the front of the DC5’s were by far the hardest to set up. Their limited suspension travel and ridiculous amounts of bump steer were difficult to overcome and hence took considerable time and effort, not to mention money. Their MacStrut design is the route of the problem but the steering arm and rack location and the centre mount steering arms are in many ways far more of an issue.
I personally like the EF style of double wishbone with its radius rods as I can easily overcome the typical Japanese car’s lack of caster. Slip the radius rods into the lath, machine up longer threads and adjust away. As mentioned in a previous post, the problem with the EF design is the lack of rigidity for the front mounts of the radius rods. Which is really difficult to fix, extending a triangulated roll cage out to the radiator support panel area is not something I would consider. Plus it is not allowed in most forms of motorsport.
The problem I find with the EK is the mounting of the front upper control arm and the one piece lower control arm. It makes adjusting caster and camber a real exercise in frustration. There are solutions but they are neither elegant nor cost effective.
That leaves the EG, which to me is the definitive Honda suspension system. With it's 2 piece lower control and upper control arm mounted pivot points it's easy to adjust for camber, caster and toe, very tolerant of height and with no real bump steer issues.
Cheers
Gary
not that I would know, but I never thought there was much difference between the ek and eg.Quote:
Originally Posted by Sydneykid
only difference was one was a one piece lca and the other was two piece.
can't adjust castor on ek and eg either.
Quote:
Originally Posted by Bludger
Take a close look at the difference in the front upper control arm inner pivot points. The EG has the bushes separate from the upper control arm, so they are much easier to adjust camber with eccentric crush tubes in the bushes. With the EK you have to replace the upper control arm and adjust camber with a sliding ball joint. Much more expensive and not legal in most forms of circuit racing.
The EG lower control arm is 2 piece, so to add caster you simply space the two pieces. The EK lower control arm is one piece, so you can't separate it. That means adding a limited amount of caster with an offset (outwards) rear bush.
I wrote an article for Hot 4's some years back on setting up EG suspension and the ability to enhance caster and camber was the catalyst. I also designed an EG caster kit for Whiteline at the same time. We ran an EG Si hatch at the Bathurst 12 Hour in 1993 for a 3rd in class, so I am rather familiar with that model.
Cheers
Gary
thank you.
in my DC2, which I believe has the same setup as the EG
How confidant and sound is the idea if I were to say add enough washers OR fabricate a set of spacers to fit in between the two piece front LCA.
What are (if any) the downfalls of this Idea???
I'm not sure if you're familiar with the many brands of traction bars available on the market. Is there any detriment to the movement of the front suspension if BOTH modifications were implemented?? (increased castor & traction Bar)
Would binding occur from the altered geometry? stress on the bushings? unwanted forces/stresses being applied to the LCA via both modifications?
YepQuote:
Originally Posted by Bludger
I have been doing that on multiple road and race cars for 17 years, is that enough confidence?.Quote:
How confidant and sound is the idea if I were to say add enough washers OR fabricate a set of spacers to fit in between the two piece front LCA.
You need to know what you are doing, you need to use the right components, such as high tensile bolts and spacers plus nylock nuts etc.Quote:
What are (if any) the downfalls of this Idea???
Whiteline used to sell the kit that I engineered containing the right components and detailed instructions, I think they still do, KCA301, it cost around $60.
Sorry, I don't know what you mean by "traction bar"?Quote:
I'm not sure if you're familiar with the many brands of traction bars available on the market. Is there any detriment to the movement of the front suspension if BOTH modifications were implemented?? (increased castor & traction Bar)
NopeQuote:
Would binding occur from the altered geometry?
Yes, the inner lower control arm bush is distorted, but not beyond its capability. I have had the same Mugen hardness up rubber bushes in one of the race cars since 1994. We usualy use polyurethane bushes, they wear out a little quicker but don't flex as much as rubber, so they help retain the suspension geometeryQuote:
stress on the bushings?
No more than normal.Quote:
unwanted forces/stresses being applied to the LCA via both modifications?
Cheers
Gary
thanks!Quote:
Originally Posted by Sydneykid
Looked up on Whitline website and found the EG article documents you wrote Gary:
Links:
http://whiteline.com.au/images/artic...andling_32.jpg
http://whiteline.com.au/images/artic...ndling_32b.jpg
Good reading!
Hey Gary aka Sydneykid,
> We usualy use polyurethane bushes, they wear out a little quicker but don't flex as much as rubber, so they help retain the suspension geometery
What's your opinion on the different hardness poly bushes available?
I've used 'Energy Suspension' brand and felt they were too soft, with visible oval distortion.
Most other brands are similar in durometer hardness.
Prothane is significantly harder, but I've yet to try them.
Nick.
Hi Nick, polyurethane is not like rubber, its doesn't have air bubbles trapped inside to absorb the distortion. The excess material has to go somewhere, that’s the “bulging” as you call it. So it doesn’t matter what duro polyurethane you use, there will always be “bulging” required to absorb the initial distortion when the suspension member is bolted up.Quote:
Originally Posted by nd55
What the different duro does is determine how much the bush moves under any given impact, say when the wheel hits a bump etc. That’s what’s important, not how much the bush “bulges” when you bolt it in.
Leaving aside the negative NVH effects of higher duro, if you go too high in the duro you can get tearing and the bush doesn’t last any time at all. If you go too soft in the duro then the bush will allow too much geometry change. Each bush is different in size and loading, so selecting the right duro is not a simple task.
Due to the low volumes involved, there usually isn’t much of a range of duro in the same bush part number. To further compound that R&D is expensive and the cheaper/smaller bush suppliers simply copy the larger bush manufacturers. A small number of high volume part numbers are available in multiple duros, Whiteline WRX anti lift kits being an example where there is a road duro at around 82 and a race duro at around 95.
Cheers
Gary
Hey Gary, this is the traction Bar I'm refering to for our Honda's.Quote:
Originally Posted by Sydneykid
http://i16.photobucket.com/albums/b3...actionBar7.jpg
http://www.full-race.com/catalog/ima...tion%20bar.jpg
Now that you can see what I'm talking about, kindly answer my previous questions regarding.......
Thanks:D
Quote:
Originally Posted by Bludger
Wow this is abit of a trip to see someone like this on these forums.. i got that article in magazine, and have seen the whiteline parts but never knew if the caster kit was really worth it or if it was worth the money for the changeQuote:
Originally Posted by Sydneykid
Is increasing caster a big thing in improving the cars handling? And how to whitelines camber kits go vs bigger honda companies like buddyclub and skunk2??
Wow, that's one complex system of radius rods:eek:Quote:
Originally Posted by Bludger
I'm not really sure what it is that they are trying to achieve. Perhaps reduce the longitudinal (for and aft) compliance in the lower control arm inner and rear bushes. But the addtiional of radius rods would do nothing for the lateral and vertical compliance. It maybe of some use in a drag racing environment where the elimination of longitudinal movement would be of slight benefit, limiting caster change. But it would do nothing for maintaining camber or toe, so of very little use in road and/or circuit car.
Plus I'm not a big fan of spherical bearings in road cars, they are very exposed, have no dust covers or greasing points and they look somewhat undersized for my liking. My guess is they would need cleaning and greasing regularly and replacing frequently.
A much better solution would be to replace the bushes with polyurethane and fit a caster kit. That way you have the benefits of additional caster plus the full 360 degree improvement in rigidity from the polyurethane bushes (over the standard rubber).
Cheers
Gary
I think these arms are marketed at those with higher than usual power who are susceptible to wheel hop or torque steer.Quote:
Originally Posted by Sydneykid
Maintaining longitudinal position helps maintain toe. Allowing the upright to move forward will pull the tie-rod forward, toeing out the wheel. The "traction bar" virtually eliminates this factor.Quote:
Originally Posted by Sydneykid
The new constraints on the suspension geometry will offer lateral compliance advantages in two ways:
1) An applied pure lateral force at the lower ball joint must partially pass through the radius rod linkage since the radius rods are not perpendicular to the control arm. The angle is quite small (20 degrees conservative approximation) so it's aid will be less than 10%.
2) The resultant force on the two-piece (effectively a rigid body) LCA can now never be purely lateral, it must always be perpendicular to the radius rod. Now you have the compliance bushing helping in a purely lateral force (which without the radius rod, could potentially load solely the inner LCA bushing).
The benefits above will be enhanced the closer the applied force is to parallel with the radius rod (engine power). The radius rods will have the least (zero) effect when the applied force is exactly perpendicular to the radius rod (i.e. the applied force is not at all constrained by the radius rod).
Without any data on the relative strengths of the compliance bushing and the inner LCA bushing, it's impossible to give any real numbers. Suffice to say, the effects on lateral compliance and therefore camber compliance, are an infinite times more than nothing.
[QUOTE]Not sure how much "higher than usual is", for circuit racing we are looking at around 300 bhp and 220 ft lbs of torque running N/A on E85. That's around double the standard power output, but of course nowwhere near the 700 + bhp the drag guys are extracting forced induction and methanol.Quote:
Originally Posted by string
All I can say is with bush upgrades and caster kits running R type tyres, we don't see any wheel hop or torque steer.
But it does nothing for the upper control arm. That's why we replace the rubber bushes in the upper control arm with polyurethane as well.Quote:
Maintaining longitudinal position helps maintain toe. Allowing the upright to move forward will pull the tie-rod forward, toeing out the wheel. The "traction bar" virtually eliminates this factor.
It is also mounted inboard, at the shock mount.Quote:
The new constraints on the suspension geometry will offer lateral compliance advantages in two ways:
1) An applied pure lateral force at the lower ball joint must partially pass through the radius rod linkage since the radius rods are not perpendicular to the control arm. The angle is quite small (20 degrees conservative approximation) so it's aid will be less than 10%.
There are 4 bushes involved, the lower control arm inner, the lower control arm rear and the 2 upper control arm bushes.Quote:
2) The resultant force on the two-piece (effectively a rigid body) LCA can now never be purely lateral, it must always be perpendicular to the radius rod. Now you have the compliance bushing helping in a purely lateral force (which without the radius rod, could potentially load solely the inner LCA bushing).
Not quite as the driveshaft is mounted above the lower control arm. As is the steering arm.Quote:
The benefits above will be enhanced the closer the applied force is to parallel with the radius rod (engine power).
Exactly, that's why they are of zero use in controlling camber.Quote:
The radius rods will have the least (zero) effect when the applied force is exactly perpendicular to the radius rod (i.e. the applied force is not at all constrained by the radius rod).
You lost me. The aftermarket traction rod would allow horizontal and verticle rotation around its attachment point to the lower control arm. Any bush compliance, and there is a lot in the standard rubber bushes when new let alone after 15 years, would result in uncontrolled changes in caster, camber and toe.Quote:
Without any data on the relative strengths of the compliance bushing and the inner LCA bushing, it's impossible to give any real numbers. Suffice to say, the effects on lateral compliance and therefore camber compliance, are an infinite times more than nothing.
My opinion, as stated above, is that the traction rod kit is pretty much wortheless unless you are drag racing and even then I would argue that there are better methods that would achieve a superior result.
So why are they made and sold? It's got more to do with the Japanese market than pure engineering. So it is worthwhile investigating the reason behind that market. Japanese workshops charge upwards of $500 per hour for mechanic’s time. That’s why Japanese aftermarket parts supplies sell 100% complete products, that come with every nut bolt screw and washer necessary, perfect thread, perfect holes etc. The workshop’s customer is not going to be very happy if he buys a $300 part that costs $1500 to fit because the mechanic spent a couple of hours searching for the right fasteners and drilling some holes. This huge disparity in the cost of parts versus the cost of labour means that solutions, to problems such as suspension geometry, have to be bolt on. Quick, easy, simple, in and out of the workshop. Plus they wouldn’t require a wheel alignment, bolt them on and drive out. All up maybe 30 minutes, say, $550 for parts and labour
The problem is this leads to unusual solutions to problems that would be better solved with other methods. Let’s take the upgraded bushes that we would typically apply in Australia where workshops labour rates are more like $80 an hour. The polyurethane bushes to fix this problem would cost less than $250 and take around 2.5 hours to fit. Add the necessary wheel alignment, you should never fit new bushes without one, and all up, say $500, parts and labour.
Technically there is no doubt the “Australian” solution is superior, but it would never happen in Japan, $250 in bushes plus $1500 in labour to fit them is just not going to be accepted by the workshop’s customer.
Personally I would take the opportunity to build in adjustment for caster and camber while I had the front suspension apart for fitting of the bushes. So I would spend and extra $100 to $150 on the bushes and get a far superior solution.
Cheers
Gary
The traction bars have nothing to do with Japan, they're of USA origin.
I'll reply more when I'm not at work.
My post is not to imply that the bars will eliminate the problem, rather that the effect is non-zero. Reducing the deflection at either end (top or bottom in this case) will help the problem.Quote:
Originally Posted by Sydneykid
I'm not sure what you are trying to say. The radius rod could mount halfway between where it is the photo and the inner LCA bushing. The physics remains the same, just that the angle will now be less and the radius rod will receive less load during an applied lateral force.Quote:
Originally Posted by Sydneykid
As above ; reducing the "lower arm" compliance (movement of the lower ball joint) will result in less camber change, even if you leave the uppers the way they were. With a floppy LCA bushing, the upper control arm still sees the same force (once the lower bushing has fully compressed that is).Quote:
Originally Posted by Sydneykid
The steering arm and driveshaft have nothing to do with this. My statement was referring to how the radius rod will be loaded based on the direction of the tyre force. Still working in top/bottom view here.Quote:
Originally Posted by Sydneykid
... when the tyre force is in exactly the right direction. In all other directions, the radius rod will be doing something, and in one direction, the radius rod will take [almost] all of the lower arm work. Any time that the lower control arm bushings are taking less load with the radius rod attached, you have less camber compliance. Might not be much but it is not zero.Quote:
Originally Posted by Sydneykid
[QUOTE]Quote:
Originally Posted by string
Where the radius rod attaches to the LCA effectively becomes a pivot point, the further away from the tye contact patch the greater the leverage exerted on the rubber LCA inner bush.Quote:
I'm not sure what you are trying to say. The radius rod could mount halfway between where it is the photo and the inner LCA bushing. The physics remains the same, just that the angle will now be less and the radius rod will receive less load during an applied lateral force.
But uncontrolled camber change is really only an issue when cornering, ie; side load is applied via the tyre to the upper and lower control arms. Where the additional radius rod does zero and the load is shared between the upper and lower control arm bushes. Hence why ungrading those bushes will actually have an effect on camber control whereas adding radius rods will have none.Quote:
As above ; reducing the "lower arm" compliance (movement of the lower ball joint) will result in less camber change, even if you leave the uppers the way they were. With a floppy LCA bushing, the upper control arm still sees the same force (once the lower bushing has fully compressed that is).
But torque steer is actioned through the drive shaft and the steering arm. So their location most certainly has something to do with any claim that adding radius rods will decrease torque steer.Quote:
The steering arm and driveshaft have nothing to do with this. My statement was referring to how the radius rod will be loaded based on the direction of the tyre force. Still working in top/bottom view here.
I would claim the reverse, the radius rod only works in 2 directions, longitudinaly. But even then, because of the leverage factor around the pivot point, the standard rubber bushes on the control arms are still the weakest point in camber control. Hence my ascertion that they should be changed as a first priority.Quote:
... when the tyre force is in exactly the right direction. In all other directions, the radius rod will be doing something, and in one direction, the radius rod will take [almost] all of the lower arm work. Any time that the lower control arm bushings are taking less load with the radius rod attached, you have less camber compliance. Might not be much but it is not zero.
In summary, additonal radius rods are waste of time, money and effort unless you are in a drag racing environment with surplus power, lots of traction and you don't know how to change bushes.
Cheers
Gary