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

[Racecomp Engineering]

I know that WRC tarmac rally cars were mostly running spring frequencies lower than 2 Hz, at least in the early-mid 2000s. I think some right around there but most were softer. That was with shocks a couple steps above anything we're talking about here and also sticky tires. Current/recent Group N cars (again with extremely good shocks) are around 2 Hz on tarmac. Meaning...you should probably be aiming a little lower than that.

2 Hz for a BRZ front suspension is around 6 kg/mm springs.

Suspension travel is also very important on these types of roads...we really liked our Ohlins in terms of valving but wanted more travel. If you're going to run relatively soft springs it becomes even more important.

- Andrew

[marco_mc22]

Originally Posted by Racecomp Engineering

I know that WRC tarmac rally cars were mostly running spring frequencies lower than 2 Hz, at least in the early-mid 2000s. I think some right around there but most were softer. That was with shocks a couple steps above anything we're talking about here and also sticky tires. Current/recent Group N cars (again with extremely good shocks) are around 2 Hz on tarmac. Meaning...you should probably be aiming a little lower than that.

2 Hz for a BRZ front suspension is around 6 kg/mm springs.

Suspension travel is also very important on these types of roads...we really liked our Ohlins in terms of valving but wanted more travel. If you're going to run relatively soft springs it becomes even more important.

- Andrew

How about frequency bias on tarmac?

[Racecomp Engineering]

Originally Posted by marco_mc22

How about frequency bias on tarmac?

Generally less rear biased on tarmac than it is on gravel...but dependent on car, driver, and team.

- Andrew

[Lucky21]

Does anyone have any experience regarding tein endura pro plus shocks and how do they compre to bilstein b6/b8?

[bradsm87]

Do you guys know of any good coilovers that have at least 115mm total stroke both front and rear? Not just ones intended for rally but rather ones that can still go low and just have lots of extension travel. Obviously helper springs would be needed to make it work.

I'd really like suspension that works well driving hard on bad roads and also to keep all tyres on the ground when entering driveways on an angle.

[Racecomp Engineering]

Originally Posted by bradsm87

Do you guys know of any good coilovers that have at least 115mm total stroke both front and rear? Not just ones intended for rally but rather ones that can still go low and just have lots of extension travel. Obviously helper springs would be needed to make it work.

I'd really like suspension that works well driving hard on bad roads and also to keep all tyres on the ground when entering driveways on an angle.

Our RCE coilovers (and most KW coilovers) have 142mm total shock travel up front and 108mm in the rear. With the motion ratio that rear is about the same 142mm wheel travel as the front. Bumpstops take up part of that travel.

- Andrew

[marco_mc22]

Originally Posted by Racecomp Engineering

Our RCE coilovers (and most KW coilovers) have 142mm total shock travel up front and 108mm in the rear. With the motion ratio that rear is about the same 142mm wheel travel as the front. Bumpstops take up part of that travel.

- Andrew

Do you know bump to droop ratio relative to let’s say 20mm of lowering? Assuming stock mounts and rear arms used of course.

[Racecomp Engineering]

Roughly 60/40 bump to droop.

- Andrew

[marco_mc22]

Just out of curiosity, does your Tarmac 3 based on 3 ways CS has different numbers due to their hybrid construction? If I’m not wrong they’re monotube on bump side and twin tube on the droop one? Also, their lowering top hats should shift everything allowing lowered heights keeping the same ratio right?

[Racecomp Engineering]

Originally Posted by marco_mc22

Just out of curiosity, does your Tarmac 3 based on 3 ways CS has different numbers due to their hybrid construction? If I’m not wrong they’re monotube on bump side and twin tube on the droop one? Also, their lowering top hats should shift everything allowing lowered heights keeping the same ratio right?

Our Tarmac 3s are unfortunately no longer available right now.

Yes lowering top mounts would shift the bump/droop ratio towards bump a little more at the same ride height.

- Andrew

[bradsm87]

Originally Posted by Racecomp Engineering

Our RCE coilovers (and most KW coilovers) have 142mm total shock travel up front and 108mm in the rear. With the motion ratio that rear is about the same 142mm wheel travel as the front. Bumpstops take up part of that travel.

- Andrew

That's great. HKS Hipermax S only have 87mm front stroke and 106mm rear stroke according to their spec page. I feel this would be annoying on bad roads and angled driveway entries.

[Racecomp Engineering]

Originally Posted by bradsm87

That's great. HKS Hipermax S only have 87mm front stroke and 106mm rear stroke according to their spec page. I feel this would be annoying on bad roads and angled driveway entries.

That would not work for me either.

- Andrew

[Tatsu333]

Originally Posted by Racecomp Engineering

Our RCE coilovers (and most KW coilovers) have 142mm total shock travel up front and 108mm in the rear. With the motion ratio that rear is about the same 142mm wheel travel as the front. Bumpstops take up part of that travel.

- Andrew

I'm trying to get my head around why the KW/ST coilovers (and presumably the RCE SS1's, though I don't know that for sure) that use the front lowering camber plates have shorter main spring free lengths in the front (170mm vs. 200mm) than those that don't. It seems counterintuitive to me.

If it were just a matter of limiting bump travel, that could be addressed with having the spec for the minimum lower perch position being changed a corresponding amount to match the change in upper perch height, no?

Thinking about it some more while typing this, I suspect it may have something to do with keeping the extension / droop travel of the dampers within range for a given ride height, but that only makes sense if those top mounts result in the damping rod being more extended at rest vs. the stock top mounts for a given ride height, and I can't imagine it would be a 30mm difference (though that magnitude of change in spring length is likely "just because" that's the next shorter step they produce).

Am I on the right track here, or do you have any other input / explanation / theory for why the shorter springs would be used in this application?

[marco_mc22]

They're stiffer, less sag under weight keeping the same preload.
They also use weaker helpers up front, 3-60-80 instead of 10-60-80, basically 3nm vs 10nm, well, I've never understood why honestly...hopefully Andrew will enlighten us ahah