Rear - double wishbone / multilink

[eurofan]

hi guys, i've wiki-ed this but i don't think i fully understand this...

what's the difference between double wishbone and multilink? is one a subset of the other? if there is a difference, which one is better?

the australian brochure says that the euro has a double wishbone rear suspension but i think the US brochure says that the acura TSX has a multilink rear suspension. i don't think honda/acura would have a different setup for the TSX vs the Euro, right?

thanks

[JohnL]

hi guys, i've wiki-ed this but i don't think i fully understand this...

what's the difference between double wishbone and multilink? is one a subset of the other? if there is a difference, which one is better?

the australian brochure says that the euro has a double wishbone rear suspension but i think the US brochure says that the acura TSX has a multilink rear suspension. i don't think honda/acura would have a different setup for the TSX vs the Euro, right?

thanks

What could be descibed as a 'multi link' suspension might basically be a 'strut' type suspension without an upper 'wishbone', but several lower linkages that more or less do a similar job as a lower wishbone, though won't be the same in detail. This won't be the Acura set up though, which will be the same as or in principle the same as the Honda badged rear suspension.

If you look at the rear lower wishbones on most purpose built racing cars you'll note that they aren't really a wishbone as such (not like the upper wishbone that genreally is a real wishbone link), but a 'multi linkage' of some description, though these rear suspensions are typically reffered to as 'double wishbone' for convenience (and they are very similar). I would think nearly all rear 'double wishbone' rear suspensions would be somewhat similar to this in principle.

The front suspension on our racing car will typically have true wishbones upper and lower, or at least a linkage(s) that will be geometrically the same as a wishbone, if not mechanically identical.

The Honda rear 'double wishbone' suspension is a fairly unique design, not really a double wishbone in the classic sense nor in the 'convenient' sense. At the bottom it looks somewhat similar to a strut type multi link or our racing car's multi linkage, but not quite. At the top it has a kind of 'half wishbone' that is really only a lateral link with no ability to locate the suspension upright in a longitudinal direction.

Resistance to the upright 'rotating' (especially under braking forces) is taken care of by the lower forward suspension arm (a type of 'radius rod'), which is flexibly mounted to the chassis at it's leading end, but attached to the upright solidly by two vertically spaced apart bolts and two bushings (that allow some limited movement inward but not rotationally, which is difficult to describe but easy to understand if I could point to things). As such the upper link only has to deal with lateral loadings, so is only a single arm that has no longitudinal bracing.

In fact the upper 'half wishbone' needs some degree of longitudinal freedom because due the nature of the manner in which the 'radius rod' locates the upright longitudinallly and rotationally, as the suspension rises and falls in bump and rebound the upright moves in an arc centred on the forward radius rod chassis attachment. If the upper linkage were not free longitudinally then the suspension would bind up in bump and rebound.

Hope that helps.

[eurofan]

wow, you know your stuff. thanks for the response :thumbsup:

[JohnL]

wow, you know your stuff. thanks for the response :thumbsup:
Eurofan, please read it again I edited just this moment.

[eurofan]

i just read your edit. "...our racing car..."?? are you pro? any details?

thanks again for your comments :thumbsup:

[JohnL]

i just read your edit. "...our racing car..."?? are you pro? any details?

thanks again for your comments :thumbsup:

Sorry to confuse, I meant 'our' hypothetical racecar because I'd already talked about racing cars above that, just referring back to the example. I used to race karts, which are very real racers, and very real racing!

[EUR003act]

i think this backs up johnL's explanation:

*Euroaccord13 Edit*

From satoauto - acura information and discussion
Posted by Colin Sato in Tech Talk, Wednesday November 20th 1996

There are many different approaches to suspension design, however the two types that are most common in passenger cars are: McPherson Struts, and Double Wishbones.

With a McPherson strut, a control arm is used to support the suspension at the bottom and a spring-over-shock as the suspensions upper mounting point. The advantage to this type of suspension is the ease and low cost of manufacture. The problem here is the “shock absorber” not only damps the spring action, but must also act as the steering pivot and must absorb acceleration and braking forces as well. Perhaps more important, is the loss of tire contact with the road as the wheel moves in a big arc in response to road irregularities. ( see diagram) Less tire on the road means less traction available for acceleration, braking and turning!

Acura’s racing inspired suspension uses “wishbones” or “A” shaped control arms to support the suspension at both the top and the bottom. (see diagram) This sophisticated design frees the shock absorber to perform its primary duty of damping spring action without having to absorb driving forces. This also means that each tires contact patch is consistent, providing more traction for accelerating, turning and braking.

We achieve a smoother ride AND better handling - in every car in our lineup, from the Integra to the NSX! Truly “Precision Crafted Performance”

[JohnL]

i think this backs up johnL's explanation:

There are many different approaches to suspension design, however the two types that are most common in passenger cars are: McPherson Struts, and Double Wishbones.

With a McPherson strut, a control arm is used to support the suspension at the bottom and a spring-over-shock as the suspensions upper mounting point. The advantage to this type of suspension is the ease and low cost of manufacture. The problem here is the “shock absorber” not only damps the spring action, but must also act as the steering pivot and must absorb acceleration and braking forces as well. Perhaps more important, is the loss of tire contact with the road as the wheel moves in a big arc in response to road irregularities. ( see diagram) Less tire on the road means less traction available for acceleration, braking and turning!

Acura’s racing inspired suspension uses “wishbones” or “A” shaped control arms to support the suspension at both the top and the bottom. (see diagram) This sophisticated design frees the shock absorber to perform its primary duty of damping spring action without having to absorb driving forces. This also means that each tires contact patch is consistent, providing more traction for accelerating, turning and braking.

We achieve a smoother ride AND better handling - in every car in our lineup, from the Integra to the NSX! Truly “Precision Crafted Performance”

Well, IMO this is a very simplistic and not entirely accurate explanation from the Honda marketing people (who probably don't really understand what they're talking about, not being engineers and probably not really interested).

Quote:
"The problem here is the “shock absorber” not only damps the spring action, but must also act as the steering pivot and must absorb acceleration and braking forces as well."

This isn't wrong, but it doesn't explain much. What this means is that (with Mac stuts) braking and accelerating forces (that attempt to 'rotate' the strut around the lower ball joint) are resisted internally against the piston and bore of the damper, which causes increased internal 'sticktion' inside the damper so it's effective rate is different when braking, accelerating, and not doing either. In bad cases the damper can become somewhat 'jerky' in it's operation when braking or less so when accelerating. The driver probably won't feel this, but the contact patches might. In practice it's not a big problem, but is less than ideal. This also most probably contributes to wear in the damper's bore / piston and seals.


Perhaps more important, is the loss of tire contact with the road as the wheel moves in a big arc in response to road irregularities.

This is IMO a bit misleading and incorrect. It's more like the other way around, i.e. Mac struts typically gain less increase in camber with suspension movement ("moves in a big arc", no, a lesser radius arc) than do double wishbones (though you can make double wishbone geometry such that the camber change is almost anything you want). In this sense DW suspension has a more acute arc of motion (than Mac struts), and it's with Mac struts (not DW) where the wheel moves in a lesser arc in response to road irregularities", which isn't the impression given by the Honda blurb. This is a good thing, and the primary reason to use DWs instead of Mac struts.

With double wishbones there will typically be more camber change with bump and rebound than with Mac struts which means that as the body rolls the suspension is better able to keep the wheel more vertical in the corner (despite the body roll) and give better grip because of this. With body roll Mac struts allow more pos camber to develop at the outside wheel (relative to the road surface) and more neg camber at the inside wheel (relative to road). Both these camber problems with Mac struts decrease contact patch size or at least cause uneven loading within each contact patch, and thus give poorer grip.

[EuroAccord13]

It will be good to reference your source :)


i think this backs up johnL's explanation:

There are many different approaches to suspension design, however the two types that are most common in passenger cars are: McPherson Struts, and Double Wishbones.

With a McPherson strut, a control arm is used to support the suspension at the bottom and a spring-over-shock as the suspensions upper mounting point. The advantage to this type of suspension is the ease and low cost of manufacture. The problem here is the “shock absorber” not only damps the spring action, but must also act as the steering pivot and must absorb acceleration and braking forces as well. Perhaps more important, is the loss of tire contact with the road as the wheel moves in a big arc in response to road irregularities. ( see diagram) Less tire on the road means less traction available for acceleration, braking and turning!

Acura’s racing inspired suspension uses “wishbones” or “A” shaped control arms to support the suspension at both the top and the bottom. (see diagram) This sophisticated design frees the shock absorber to perform its primary duty of damping spring action without having to absorb driving forces. This also means that each tires contact patch is consistent, providing more traction for accelerating, turning and braking.

We achieve a smoother ride AND better handling - in every car in our lineup, from the Integra to the NSX! Truly “Precision Crafted Performance”

[JohnL]

It will be good to reference your source :)

It's obviously from a Honda propoganda sheet or site, I think most of us could see that without reference. It's not as if he's trying to claim it as his own writing.

[EuroAccord13]

It's obviously from a Honda propoganda sheet or site, I think most of us could see that without reference. It's not as if he's trying to claim it as his own writing.


Yes, you are right, Most of us can see that.

We encourage referencing other people's work/images/articles in this forum.

I am in no way saying that he is claiming it to be his own but it's always good to reference other peoples' work.