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MikeRT4
Posts: 37
Joined: Dec 2016
Great Britain

What is the ideal ride height and rake?

#1

Dec 9th, 2016, 4:43 pm

My Ohlins dampers have finally landed, but before I fit them I wanted to discuss suspension set up. I am not interested in "slamming" the car or even in lowering it at all IF the ideal ride height is the OEM set-up.

I don't want to induce any bump steer, so I know that to avoid that, I should not lower the car anymore than 20mm on the rear, which I guess to keep the OEM 15mm rake means lowering the front by the same amount.

I have purchased some 10k rear (Eibach) springs and will be setting these up with the recommended 10mm preload, which by it's very nature reduces the available drop from the factory 14" to a maximum reduction of 13.375" (according to SBK's figures). However, I am more than happy to stick at factory ride height IF this gives the best bump curve.

So with that in mind, has anyone actually gone to the lengths of mapping the bump curve to see what the optimal ride height setting would be? Handling is far more important than looks to me.

I suspect this info is readily available on the S2ki forum, but it would be good to have a discussion here as well (plus saves me all that trawling if someone remembers seeing this info and can help me out :) ).
Mike R
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andrewhake
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#2

Dec 10th, 2016, 12:16 am

This is the type of thing that can be discussed to death but when it really comes down to it there is not really a specific answer without experimentation. it really just comes down to how you are going to use the car.

In my opinion the advantages gained from lowering the ride height outweigh nearly any other suspension change you can do to the car. Aside from the improved response time and dynamics of the car under lateral and longitudinal load, there are also pretty large aero advantages and other things. Of course you need to do this in an effective way that doesn't ruin other aspects of the car, with an appropriate spring rate and dampers to match and maybe even geometry correction. In most cases I think it is pretty generally accepted that you want to run as low as you reasonably can, given your specific limitations in terms driving surface, and so on. If you are doing rally, your ride height needs will be different than someone who only does time attack at Tsukuba Circuit.

In terms of rake I think that also comes down to driver preference and the rest of the car setup. I run the same ride height front and rear. I would guess the OEM rake (which likely varies on different models) helps the rear of the car rotate a bit better with the staggered tires. Running without rake is probably a good idea for people going to a square tire setup.

All that said, 25mm lower than stock is a great starting point without any real compromises. Especially if you also incorporate roll center adjustment into the equation. People have definitely gone through all the theory and measurements, but amazing how fast all that can change with all the other variables thrown into the mix.
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Cpt. Spock
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United States of America
#3

Jan 3rd, 2017, 2:16 pm

This is with 13k front springs and 11k rear springs. The front has factory Ohlin's recommendations (ride height/pre-load) and RCA's installed. The rear has factory Ohlin's pre-load but the bottom collar is bottomed out. As you can see, there is a significant Rake going on. Keep in mind, with stiffer springs, the ride height adjustments will be different than what is listed on Ohlin's spec sheet, which is why i had to bottom out the rear collar and still not exactly where i want to be.

The two options im currently looking at to resolve the rear ride height issue is:
-Rear RCA's
-Or there is a company making aftermarket rear lower collars for ohlins that allow you to lower your car farther than ohlin's collars.

Going off of what Andrew said, i think the "ideal ride height" is up to the driver, and can vary depending on what your needs/wants are, and modifications you have done to the car.

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TsukubaCody
Posts: 45
Joined: Nov 2016
Zimbabwe
#4

Jan 5th, 2017, 6:29 pm

Cpt. Spock wrote:This is with 13k front springs and 11k rear springs. The front has factory Ohlin's recommendations (ride height/pre-load) and RCA's installed. The rear has factory Ohlin's pre-load but the bottom collar is bottomed out. As you can see, there is a significant Rake going on. Keep in mind, with stiffer springs, the ride height adjustments will be different than what is listed on Ohlin's spec sheet, which is why i had to bottom out the rear collar and still not exactly where i want to be.

The two options im currently looking at to resolve the rear ride height issue is:
-Rear RCA's
-Or there is a company making aftermarket rear lower collars for ohlins that allow you to lower your car farther than ohlin's collars.

Going off of what Andrew said, i think the "ideal ride height" is up to the driver, and can vary depending on what your needs/wants are, and modifications you have done to the car.
Did installing RCA impact your ride height?

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Cpt. Spock
Posts: 32
Joined: Nov 2016
United States of America
#5

Jan 5th, 2017, 7:37 pm

TsukubaCody wrote:
Cpt. Spock wrote:This is with 13k front springs and 11k rear springs. The front has factory Ohlin's recommendations (ride height/pre-load) and RCA's installed. The rear has factory Ohlin's pre-load but the bottom collar is bottomed out. As you can see, there is a significant Rake going on. Keep in mind, with stiffer springs, the ride height adjustments will be different than what is listed on Ohlin's spec sheet, which is why i had to bottom out the rear collar and still not exactly where i want to be.

The two options im currently looking at to resolve the rear ride height issue is:
-Rear RCA's
-Or there is a company making aftermarket rear lower collars for ohlins that allow you to lower your car farther than ohlin's collars.

Going off of what Andrew said, i think the "ideal ride height" is up to the driver, and can vary depending on what your needs/wants are, and modifications you have done to the car.
Did installing RCA impact your ride height?
front RCA's = yes. it lowers the car depending on the rcas you buy. I dont have the rear RCA's, but that is ultimately the reason why i would buy them, is to lower the rear more since im bottomed out on the ohlins lower collar.
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andrewhake
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#6

Jan 7th, 2017, 12:04 pm

TsukubaCody wrote:
Cpt. Spock wrote:This is with 13k front springs and 11k rear springs. The front has factory Ohlin's recommendations (ride height/pre-load) and RCA's installed. The rear has factory Ohlin's pre-load but the bottom collar is bottomed out. As you can see, there is a significant Rake going on. Keep in mind, with stiffer springs, the ride height adjustments will be different than what is listed on Ohlin's spec sheet, which is why i had to bottom out the rear collar and still not exactly where i want to be.

The two options im currently looking at to resolve the rear ride height issue is:
-Rear RCA's
-Or there is a company making aftermarket rear lower collars for ohlins that allow you to lower your car farther than ohlin's collars.

Going off of what Andrew said, i think the "ideal ride height" is up to the driver, and can vary depending on what your needs/wants are, and modifications you have done to the car.
Did installing RCA impact your ride height?
The best way to think about the RCA effect on ride height is to just think of it as offsetting the knuckle/upright upwards from the bottom arm. With the knuckle offset up by 12mm or 20mm the wheel is also offset by the same amount.
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TsukubaCody
Posts: 45
Joined: Nov 2016
Zimbabwe
#7

Jan 9th, 2017, 5:36 pm

Interesting. Thanks guys!

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