Tuning Dampners

[TeMp]

Thought was an excellent post and would like to share. Especially the part I will bold. Originally quoted from CITR by jlo.

Here (http://forums.clubrsx.com/showthread.php?t=317713&page=2) is the original thread CRSX itself.


ok first things first, EVERYONE, please remove the idea from your head that some how the laws of Physics affect RWD differntly then FWD, because they don't. Meaning, If you increase the front spring rates on a RWD car, you increase understeer... Just like FWD. So Tuning "rules" apply exactly the same to both. you'll end up with different settings between a FWD and RWD chassis, but the physics and tuning theory are the same for both. (the different settings between FWD and RWD is primairly due to static weight distribution and power delivery)
Second thing..... Shocks AKA Dampers have NO effect on the amount of weight that a car transfers in a turn, Nor do they influence where the weight that does get transfered goes (Front or rear). they DO influence how quickly the weight gets transfered, and as such they influence mostly Transitional cornering characteristics... i.e. Corner entry and exit. meaning, if your car oversteers/understeers mid corner... thats not a damper issue, but if if oversteers/understeers on corner entry and/or exit then your dampers may need some tweaking.
On to Tuning....
Since Dampers dont alter how much weight gets transfered or where it goes (Front VS Rear) whats the point in adjusting the valving??? Well, since dampers contol the speed of weight transfer, you can tweak them to force the chassis to transfer weight faster or slower on one end of the car Vs the other. How is this usefull in tuning.... Simple. Because weight transfer esentially reduces the amount of traction a car makes and Dampers control how quicky weight gets transfered, you can Tune the dampers to force the chassis to transfer weight quicker (front or rear) and force one end of the car to lose traction quicker, thus influenceing the oversteer/understeer balance of the car. So, if the car is understeering you want to either slow the rate of weight transfer at the front of the car, and/or increase the rate of weight transfer at the rear of the car. for tuning purposes... STIFFER VALVING (both bump and rebound) = Faster weight transfer.
Esentially, you end up increasing the valving on the end of the car you want to have "stick" less, and you decrease the valving on the end you want to have "stick" more.
Now, there are some other things to think about while tuning with dampers. Primairly, Increasing the valving on the nose of the car also has the side effect of increasing the responce rate of the cars steering.... meaning it will react quicker to your steering imputs. This is why people tend to feel that stiffer valving on the nose is better, simply because it "Feels" better. The car is reacting quicker to your steering imputs... and that has to be better right? Not nessisarly. See, Just because the car is initiating turns quicker, doesnt mean its acutally able to take that turn quicker (you are dialing in more understeer afterall, and understeer is slow) and as most autocrossers and road racers know... what "feels" Fast, ushually isnt. So you end up having to comprimise between chassis responce rate, and the oversteer/understeer balance if you are trying to make the car as fast as possible on track. For the street... well, most people tune to make the car "Feel" fast (which is why some people seem to feel that stiff springs and stiff valving = good handling)
Does any of this really matter for the street... probably not, because after all, tuning the car to be a tenth or so of a second faster in a turn isnt really something that you'd be able to notice on the street. but for compitition, a tenth saved per turn.... adds up quickly over the course of the track.
hopefully that sheds some light on the Tuning with Dampers issue.

[Muzz]

Great info there, good find:thumbsup: . He's spot on which you dont often see when it comes to technical suspension stuff.

Take Autosalon magazines suspension article in issue 44 for example. I found quite alot of commonly mistaken, incorect information, and they were spreading it all through the public... "stiffer springs means less weight transfer" lmfao.... and less body roll means that theres less weight being transfered..... Very incorrect information, which pisses me off to see printed in a popular magazine as fact:thumbdwn:

[Spunkymonkey]

Yes Good post :)

[supersamEK]

Take Autosalon magazines suspension article in issue 44 for example. I found quite alot of commonly mistaken, incorect information, and they were spreading it all through the public... "stiffer springs means less weight transfer" lmfao.... and less body roll means that theres less weight being transfered..... Very incorrect information, which pisses me off to see printed in a popular magazine as fact:thumbdwn:

I think in autosalon they were reffering to weight transfer that is evident and effects the cars behaviour. like i mean, obviously the weight is being transferred from side to side, but having stiffer springs means the transferring weight is being absorbed by the springs and not in the rolling of the car. therefore the car is flatter and transferring weight more evenly through each of the tyres.
they are correct but maybe could have reworded it a little better, or u may have taken it out of its context a little. casue i read the autosalon article it made sense... just my 2cents

[Muzz]

This is taken directly from the article.

There are many ways to keep weight transfer in check and stiffer springs is one obviously. Springs with a higher rate mean that more weight is required for them to deflet, and require more load to compress the same amount as a standard spring.

Stiffer springs has no effect on the amount of weight being transfered, lateral weight transfer is a function of the track width, centre of gravity height and weight of the vehicle, longitudinal weight transfer is a function of the wheelbase, cg height and veichle weight.

They are blatantly saying stiffer springs reduce weight transfer, which is incorrect.
Springs have no effect on the amount of weight transferred laterally or longitudinally in the vehicle.

The differences in rates between the front and the rear will determine were this rate is being transferred. Stiffer rates in the front will mean that most of the weight transfer is occurring at the front. Running stiff rates at the rear will increase the weight transfer in the rear.

Spring rates have no effect on the amount of weight transfer, they can however be used to change the ratio how much of it is occurring at the front compared to the rear.
A stiffer rate at one end means more weight transfer at that end.


Springs with a higher rate mean that more weight is required for them to deflet, and require more load to compress the same amount as a standard spring.

This is a very odd weird thing to say although it is completely correct, but it shows the writer has a poor understanding.
A stiffer rate will require more load to compress the same amount, correct, but the load stays equal (assuming the fronts and rears are increased by the same factor of stiffness) hence why stiffer rates see less compression on the outer side, and less extension on the inside.

Another section taken directly from the text in the spring basics side bar.

The primary benefit of stiffer springs is that they minimise weight transfer.
This is once again blatantly incorrect, and i was shocked to be reading this in a mainstream magazine:eek: .


However body roll is not weight transfer. Body roll is caused by weight transfer
What he is saying is correct, weight transfer causes the body roll, but this is where I think the writer is confused.

Id say he’s thinking “stiffer springs reduce the body roll, so therefore stiffer springs must reduce the weight transfer”.
Actually it’s the same amount of weight being transferred, and because the springs are stiffer, they compress (on the outside) and extend (on the inside) less.

Hope that clears it up a little, feel free to ask anything, i LOVE talking suspension tech:thumbsup:

[Muzz]

Id say he’s thinking “stiffer springs reduce the body roll, so therefore stiffer springs must reduce the weight transfer”.


I should point out, (i know somone will ask) that the amount of body roll occouring does effect the amount of weight transfer (due to the movement laterally of where the cg lies between the wheels), but the amount is so very tiny it is negligible and completly disreguarded.

Say body roll was 10 degrees:eek: and the roll centre was 2" below the CG, the amount of weight transfered would be alot less than 1% of the total weight transfer occuring.

[EK4R]

ok back onto the article! lol no side-tracking.

so let me get it correct. if i want the front to 'stick' more to the road i would make it softer damper ? and vise versa?

would that mean, if i want to reduce understeer and get more traction when i accelerate i would reduce my damper hardness yes ?

[Muzz]

ok back onto the article! lol no side-tracking.

so let me get it correct. if i want the front to 'stick' more to the road i would make it softer damper ? and vise versa?

would that mean, if i want to reduce understeer and get more traction when i accelerate i would reduce my damper hardness yes ?

Yep, to get more grip in the front on corner exit acceleration, try softening the front or stiffening the rear. This will also give more front grip in corner entry.

[supersamEK]

Muzz, obviously you are passionate lol, respect. i not saying anything you are explaining is wrong. i agree.

it just seems you are trying to explain the scenario more in reference to the raw physics of whats going on, and is correct, whereas the article is aimed at handling noobs and reffering more to the reaction and dynamics of the car in this scenario.
Obviously the writer should clarify his terminology and he kind of does.. but maybe not clear enough.
The author was Charles Kha, right? He is a pretty respectable and knowledgable tech/car journalist. u should copy what you write and fire off a quick email to Autosalon and see what they have to say, could be interesting lol?