CSG and RCE tag-team suspension Q&A thread! Ask us anything!

[Dezoris]

this is a perfect place and time.

So Turbowski and I will be doing our install video on the Ohlins Road and Track. I know Mike does not like it but suspending that for a moment understand the build goal is a near perfect street car that has little compromise for the track. It needs to be almost OEM on the street or better not raising any red flags to casual drivers or the hard core. But when on track can do 80% of what a track prepped car can achieve without changing much of anything.

Impossible right? Thats the goal.

so the road and track on paper is one of the better kits for this purpose. Yes its not double or triple adjustable but it doesnt need to be for a street car.

So onto the questions, pre load do you really want to play with it?
Ride height, they recommend 20mm front 15mm in rear I think it is too much for our area. Would a 15mm 10mm or less hurt that much.
How long to let settle before corner balancing and final alignment?
Damper settings, typically firmer in front than rear?

[solidONE]

I would assume Ohlins will include instructions on how to set the preload, no?

[Dimman]

Do you guys have any thoughts on working/teaching about the concept of 'frequency' into more ordinary suspension discussions?

I understand it is something that you need to sort out for each car, but ballpark figures for average weight models with stock springs could be used as the baseline. (Stock Imprezaru F/R 5kg/5kg Relative Stiffness 60/70 CPM* vs Modded FRZ 4.5kg/6.3kg RS 106/111 CPM)

It would introduce the concept of 'relative stiffness' to readers so new-to-suspension people could start to develop a better/more accurate understanding than just quoting F/R spring rates, since it takes spring rate, mass and motion ratio into a single figure.



*Cycles Per Minute. Or Hertz could be used.

[Dezoris]

Originally Posted by solidONE

I would assume Ohlins will include instructions on how to set the preload, no?

they do but I guess the question is why is adjustable if there's only one way to really do it?

[solidONE]

Originally Posted by Dezoris

they do but I guess the question is why is adjustable if there's only one way to really do it?

They come with the adjustable threaded 'sock' for ride height adjustment, right? I'm sure you can raise or drop the preload a bit to suit your needs. Upping the preload will obviously increase the effective spring rate by a tad if you plan on carrying more equipment on the car (stereo system, fat girlfriend, etc) or lower the preload if you want to lighten the car. If your anal about it, I'm sure you can get spec sheet of the springs from Ohlins. 5mm of preload = xxx lbs/in, 15mm of preload = xxy lbs/in, etc. etc.

Just curious, does the instruction also tell you to measure the sag of the suspension and to adjust according to that. I suppose you can do that if you are, again, anal about your suspension. [/points to self]

[Racecomp Engineering]

Originally Posted by Dezoris

this is a perfect place and time.

So Turbowski and I will be doing our install video on the Ohlins Road and Track. I know Mike does not like it but suspending that for a moment understand the build goal is a near perfect street car that has little compromise for the track. It needs to be almost OEM on the street or better not raising any red flags to casual drivers or the hard core. But when on track can do 80% of what a track prepped car can achieve without changing much of anything.

Impossible right? Thats the goal.

so the road and track on paper is one of the better kits for this purpose. Yes its not double or triple adjustable but it doesnt need to be for a street car.

So onto the questions, pre load do you really want to play with it?
Ride height, they recommend 20mm front 15mm in rear I think it is too much for our area. Would a 15mm 10mm or less hurt that much.
How long to let settle before corner balancing and final alignment?
Damper settings, typically firmer in front than rear?

Ohlins will work well for you.

I don't recommend playing with preload. Just get it snug...a few mm. It doesn't change things as much as people think unless you really go to town. It has zero effect on spring rate, which is a common misconception.

15mm drop front and 10mm drop rear would be fine.

Should settle within a day. Drive it carefully.

Damper settings front vs rear...don't think about it in those terms. The front and rear damper do not have the same valving for Ohlins so click 5 on the front is not click 5 on the rear. Same neighborhood maybe. You need to find a setting that is firm enough that the car isn't bouncy but soft enough so that it doesn't crash over bumps. Do your best to separate the front and rear of the car in your head.

Originally Posted by Dezoris

they do but I guess the question is why is adjustable if there's only one way to really do it?

Makes it easier to take apart for one, and if anyone ever uses different than standard springs.

- Andy

[Racecomp Engineering]

Originally Posted by Dimman

Do you guys have any thoughts on working/teaching about the concept of 'frequency' into more ordinary suspension discussions?

I understand it is something that you need to sort out for each car, but ballpark figures for average weight models with stock springs could be used as the baseline. (Stock Imprezaru F/R 5kg/5kg Relative Stiffness 60/70 CPM* vs Modded FRZ 4.5kg/6.3kg RS 106/111 CPM)

It would introduce the concept of 'relative stiffness' to readers so new-to-suspension people could start to develop a better/more accurate understanding than just quoting F/R spring rates, since it takes spring rate, mass and motion ratio into a single figure.



*Cycles Per Minute. Or Hertz could be used.

I would like to do an article on suspension frequencies.

Soon.

- Andy

[Racecomp Engineering]

Originally Posted by Calum

There's been lots of talk about the camber curve in the front, extended ball joints and tie rod ends, that sort of thing. Is there any reason to worry about the camber curve in the rear? As I understand it, the lower the ride height the more camber is gained for the same amount of tire movement. Can this upset the overall balance once the ride height is too low?

There's also been things like, 20 mm lowered ride height is the lowest we should go before bump steer becomes a worry thrown, around. I'm guessing this was referencing the front suspension. How is the rear for bump steer? Does it become a worry at any ride height?

Finally, what bushings (if any) would your guys recommend to be replaced in the car. Clearly RCE sells some bushings kits, but is there anything else that isn't included that actually benefits handling or helps prevent wheel hop.

Guys, thanks a ton for doing this!

The rear camber curve is much better than the front. You'll notice when people lower the car, the rear gains a ton and the front just a tiny bit. Ride height affects balance in many ways...changing where you are in the camber curve is just one of them (and it is notable). Yes too low and you might find yourself with a lot more understeer unless you change a few things.

Not very much bumpsteer on this chassis up front, little bit in the rear.

IMO the 20mm lowering number just plain depends on a lot of things. For springs, yes. For coilovers, much more going on and firmer springs can make certain problems less of a problem.

I'm a big fan of front control arm bushings. We have so many in the rear for our car I'm not sure where to begin. The subframe bushings are awesome. I like the camber bushings but they suck to install and adjust as everyone knows. The difference between our car with essentially everything replaced and a stock car is massive. So much more connected.

- Andy

[ayau]

How do you find the balance of lowering the car's center of gravity (lowering the car) and not destroying the factory suspension geometry? Is one more important than the other? For example, is keeping the factory suspension geometry (stock ride height) better than a lower center of gravity?

What exactly gets ruined when you lower the car too much? Can you provide some examples? Is it the fact that the front struts gain positive camber when you lower it too much?

Is there any weirdness with the wheels under compression? For example, do the rear tires toe out/in under compression?

Thanks!

[kster1]

I'm not in the market but just curious. Years ago, when I had Tein RAs on my Miata, I couldn't find anyone local (San Francisco Bay Area) to do rebuilds on them. Are there any shops in CA that rebuilds Teins now? I was very happy with the RAs but found local support to be limited from the race shops.

One reason why I went with Ohlins is because Performance Shock is nearby and they do rebuilds of them (along with Koni, Motons, Penske)...
http://performanceshock.com/index.php?main_page=product_info&cPath=1&products_ id=677

Thanks,

[forwallblakmail]

I'm looking foreward to understanding about 9 words in this entire thread.

The collaboration will be a formidable one, for sure

[solidONE]

Originally Posted by Racecomp Engineering

Ohlins will work well for you.

I don't recommend playing with preload. Just get it snug...a few mm. It doesn't change things as much as people think unless you really go to town. It has zero effect on spring rate, which is a common misconception.

- Andy

Your right, a spring's rate does not magically change when you compress them.

But, lets say we have 2 springs of equal and linear spring rates. One spring is compressed an inch the other left static. Wouldn't the compressed spring offer more effective rate then the static one at the next inch of compression?

Sorry, not here to argue. You are right, you should just go by whatever Ohlins recommends. Carry on.

[Racecomp Engineering]

Originally Posted by solidONE

My question is in regards to roll bars. I know they are there to decrease body roll, but how do roll bars effect the damping of a particular shock? Let's say you have a shock/spring combo that is close to being critically damped. Now let's say you increase the rate on the roll bar. How would this effect the way the shock is damped in relation to the spring(s) since it increases the total roll stiffness in conjunction with the spring? Alternately, would a much smaller anti-roll bar in this set up require less damping?

edit: "sway bars" not "roll bars" I meant. Mike knew what I meant... lol

Swaybars have an effect on roll damping, but it is essentially zero in ride (i.e. 2 wheel bump). When you use 4 dampers total like most cars you are making a compromise between ride and roll damping ratios.

Add another 4 dampers if you don't want to compromise at all.

- Andy

[CSG Mike]

Originally Posted by solidONE

Your right, a spring's rate does not magically change when you compress them.

But, lets say we have 2 springs of equal and linear spring rates. One spring is compressed an inch the other left static. Wouldn't the compressed spring offer more effective rate then the static one at the next inch of compression?

Sorry, not here to argue. You are right, you should just go by whatever Ohlins recommends. Carry on.

When the springs are let go, they'll both compress an equal amount, proportional to their length.

The spring constant for both springs doesn't change, and unless there are unequal forces acting on them, they will both absorb energy (compress) proportionally.

Compressing a spring 2 in vs 1 in means you have to exert twice the energy. If you want to compress it 3 in, you have to exert triple the energy. This is, of course, assuming an ideal spring, and most quality springs are pretty close to ideal for all intents and purposes.