Hi,

What are the dimensions of the springs used on the Ohlins R/T coilover? I know they are 10kg front and 8kg rear but don't know their sizes.

 

2.5" ID x 8"L

 

Heavier spring in the back.

 

Off the shelf the DFVs have the 10k at the front....mine definitely did. Many folks swap them around and some vendors sell them with custom springs with the stiffer spring in the rear.

 

Why I would want a stiffer spring in the rear?

In fact I am thinking on a stiffer spring in the front.

 

Because that is how the stock springs are setup. Stiffer in the rear. It's due to the motion ratio of the shocks. Your car will have extra push if you run stiffer springs up front than in the rear.

 

The car is lifting both inner wheels during corners. The inner front tire temperatures are always higher than the outer one so it must be slipping during accelerations out of corners.

Even with Ohlins setup there is still much nose dive on braking, too.

I think the only way to put the inner tires back on the track is by using stiffer springs. It is clear to me a 10kgf spring is too soft for road racing.

 

You still need to keep the the rear springs about 20-30% stiffer than the fronts. My car is 9k fromt 11k rear and is very very well balanced with stock swaybars. All of these shots I'm either on the brakes or on maintenance throttle so the front is a touch lower than the rear.

 

In my car the front is higher than the rear. It was corner weighted to a 52/48 distribution.

Right now the car is well balanced but at the limit it understeers a bit.

I know that a stiffer spring on the rear will help transfer some weight to the inner front wheel.

One thing I have no idea of is the impact of a bigger rear wing on the balance of the suspension.

 

Look at where the rear strut attaches at the control arm compared to the front. The front is all the way out near the ball joint where the rear is in board almost half way up the lower control arm. Which means the amount of spring force applied in the rear at the tire is actually less than what the spring is rated for.

Here is a very quick read.
http://www.worksevo.com/Spring_Rates_1.pdf


Basic rule of thumb is higher rates in the rear.

 

Yes, as others have stated you want the stiffer springs on the rear given the suspension geometry. I have Ohlins on my car and my current spring rates are 650# F and 800# R which is considerably stiffer than the rates they came with.

If you have considerable nose dive currently with the 10k on the front Id recommend going stiffer to maybe a 12k but be sure to up your rear rates accordingly.

Also, how the f did you get your weight distribution to be 52/48 assuming you actually means front to rear? I dont see that happening unless you went to extreme lengths relocating a ton of stuff to your trunk as well as using ballast in the rear...

 

With that weight distribution, he'll need even stiffer rear springs. The 20-30% rull assumes the typical 60f/40r evo weight distribution. He has managed to move a lot of weight to rear of the car.

 

Yes, agreed. However I'm skeptical on that figure being accurate and think he may be talking side to side with driver in the car.

Ill have to look at my sheet from when I had my car on scales a couple years back but I recall the front being around 8 and change per tire and the rear in the 6 range. But anyway given a typical 60/40 distribution on say a 3000# which car seems easily on a track car non pig like SSL like my girl yields 1800 front vs 1200 rear which means you'd need to move ~250# to the rear to get to 52/48.

Now, maybe Im missing something but that seems like a tall order unless you are shedding weight and then adding ballast to the rear.

 

It was weighted with a full tank and a 154lbs mechanic on the driver seat. Also the car has the full trim and even the spare tire.

It is still a street car with some racing preparation. Still relutant on transpassing the point of no return lol

 

Im confused...so is the 52/48 side to side or front to rear? You must mean side to side, right?