A question about springs and shocks

[A930Rocket]

I know springs and shocks need to work together for best performance. I'm looking to upgrade my springs from 500/700 to 750/850 (which is what the Spec E46 racing uses).

My 330 is all but Spec E46 car.

Without spending $3000 for MCS single action struts and shocks (which Spec E46 racing uses), what would happen if I keep using my TC Kline Koni single adjustable struts and shocks? Looking online, I can't find specs for either one.

Making a wild ass guess, I'm thinking the stiffer springs will lessen the load on the shocks, as they won't bounce as much, versus a softer spring that's going to bounce more, and create more load on the shocks.

Edit. TC Kline carries 650 front and 700 rear springs, so I'm not far off from them.

[Zeke]

Originally Posted by A930Rocket

I know springs and shocks need to work together for best performance. I'm looking to upgrade my springs from 500/700 to 750/850 (which is what the Spec E46 racing uses).

My 330 is all but Spec E46 car.

Without spending $3000 for MCS single action struts and shocks (which Spec E46 racing uses), what would happen if I keep using my TC Kline Koni single adjustable struts and shocks? Looking online, I can't find specs for either one.

Making a wild ass guess, I'm thinking the stiffer springs will lessen the load on the shocks, as they won't bounce as much, versus a softer spring that's going to bounce more, and create more load on the shocks.

Edit. TC Kline carries 650 front and 700 rear springs, so I'm not far off from them.

I think that's the essence of shock/spring mating. Using your logic I believe that you want to be in the middle. That's not in very technical terms. Why not send a PM to Bill Verburg pointing out this thread?

[908/930]

I am no expert on this but as long as your old Koni's have enough adjustment to dampen the added spring rebound it should work. I think it would be likely to bounce back more vs less, think of the effect with no shock. Can you change to thicker oil in the shock?

[A930Rocket]

I don't know if the shocks have the ability to change oil, without rebuilding them.

If I understand the set up directions correctly, they have adjustment for rebound, but not compression, like double action shocks.

[Alan A]

How much are springs? If it’s only a couple of bills it’s probably worth sucking it and seeing.

I swapped the 275s on the back of my Rumf for 350s and it’s much better all round for $150 and an hour and a half with my head in the fender arches. Next up - if it still rubs two up - is a 425.

[A930Rocket]

Springs are about $100 apiece. I also ordered for the rear, upper spring perches and lower adjustable/articulating spring perches to help facilitate corner weighting. That added $260.

I'll give them a try and see how they do at the track, weekend after next.

[aschen]

Its gonna be hard to know with out shock dynos and expertise or at least some trial and error.

I will say Koni "yellows" which I believe are what you have are often rebuilt and revalved for racing pourposes. Have a google on this used to be common to do this for some of the autocross classes, The type of people that rebuild these probably know what spring rates are advisable as well

[ted]

My type of car typically ran 600 front 400 rear springs.
In fact my car had 800 front springs when I bought it.
My new set up runs a 150 front and 300 rear springs.
The old stiff springs made the car feel like it was riding on top of the track, now it is much more confidence inspiring.

With the soft front spring is also a down bump stop and also max front shock rebound.
So much rebound the front shock rebound is dialed out when towing the car.
If the rebound were at max in the trailer the car will jack itself down and then the tie down straps would no longer be tight.

Interestingly when the front ride height was still a little high the fix was to add more front shock rebound to stop the wheelie like front raising during acceleration.
With this set up you want to avoid bouncing off tall gators.
It is a common set up on southwest tour cars.
I have a great race shop and shock guy if you want some direction.
https://www.bryansracing.com/shocks-springs
Travis the owner was an engineer at Childress racing for a decade.

The blue spring spacer is just to raise the ride height for loading in the trailer.
You can see the shock down bump stop with shims to control full compression.


Consider some Project Mu brake pads for improved modulation.

[A930Rocket]

Originally Posted by aschen

Its gonna be hard to know with out shock dynos and expertise or at least some trial and error.

I will say Koni "yellows" which I believe are what you have are often rebuilt and revalved for racing pourposes. Have a google on this used to be common to do this for some of the autocross classes, The type of people that rebuild these probably know what spring rates are advisable as well

My understanding is that the TC Kline shocks and struts are built by Koni, but to his specifications. Of course, that could be total nonsense.

The fronts are silver/chrome. The rears are yellow, but looking at the website, they are listed as E46 TC Kline Single Adjustable. They do have the Koni sports available.

I posted on the FB Spec E46 forum asking similar questions, so I'll see what they say.

Fronts.
https://www.tcklineracing.com/webdocs/Items/Details39.cfm


Rears.
https://www.tcklineracing.com/webdocs/Items/Details30.cfm

[A930Rocket]

On a different note, what would help reduce body roll?

Last time at the track, the guy behind me was in a 968 and he said my car was leaning so much, he thought the inside front wheel was going to lift.

I know it's apples to oranges, but I see some cars going around the turns flat as a pancake.

[ted]

Originally Posted by A930Rocket

On a different note, what would help reduce body roll?

Last time at the track, the guy behind me was in a 968 and he said my car was leaning so much, he thought the inside front wheel was going to lift.

I know it's apples to oranges, but I see some cars going around the turns flat as a pancake.

Big sway bars might help.

[A930Rocket]

Those are some hefty sway bar end links!

[ted]

Originally Posted by A930Rocket

Those are some hefty sway bar end links!

Current set up is heavy sway bars, light springs, max front shock rebound with bump stops.
After a few decades of racing I finally found an engineer that can dial in the car.
No more seat of the pants testing, now it's all engineered correctly before we get to the track.
Years ago at the track I would ask questions like yours and my more experienced racer mentors would simply say "you need an engineer to answer that question".
I'm thinking how are we racing these 700hp cars then without engineers? lol
In the last 5 years both my race cars are safer and faster thanks to having an engineer set them up.
Every aspect of the car, handling, brakes, whatever.

[cockerpunk]

Originally Posted by A930Rocket

On a different note, what would help reduce body roll?

first determine if body roll is actually hurting you. a lot of people in the performance car world dont understand that body roll in and of it self, is not a problem. the problem with body roll is if it leads to poor alignment, specifically in most cases, going into positive camber.

getting good pictures of your car at full cornering power, or using a tire pyrometer (which you have to be careful about cause they will lie to you), can help you decide if the body roll is indeed hurting you or not. as long as those wheels are vertical, the body could be rolled whereever you want it to be, and it will still make grip.

lifting a front wheel is less about body roll, and more about front/rear weight transfer. thats a second order effect of roll stiffness. it might indicate that you need more rear spring or bar.

remember, you always want to run as soft as possible while maintaining cornering power and balance. the goal is never to run any stiffer than you absolutely have to. softer means better ride, and that means better on tires, and over curbing. just cause some guy says something about what he saw, doesnt mean much.