Suspension setup

Just wondering if anyone has opinion on suspension setup and how much up travel vs. down travel is best. Is it as simple as 40% up 60% down? (just arbitrary numbers there) or do you have to know lots about shocks, spring rates, corner weight, etc... to know what I'd need.

Mark and I have been playing with various torsion bar preload settings to get a decent ride height. A bit too high and the rear end feels loose and wallowy, to low and its hitting the bump stops a lot.

Opinions?



Edited 1 time(s). Last edit at 06/18/2013 12:41PM by johnhuebbe.

On the motorcross bike, I set the sag, which is difference between full droop and suspension compressed with rider in riding position, at around 100mm, which is approximately 1/3 of the travel. This is pretty standard. I would shoot for 1/3 on the rally car also, maybe a tad more.

Mountain bikes, motocross bikes, road racing cars, formula SAE car... all set at or near 30% sag.
Though the Volvo 240s (and Escorts) in Europe seem to be at 50-60% (!?!). But that's deduced from pics of cars mid corner or accelerating. So...?

A LOT has to do with the available total wheel movement.

On bike, everything has been at least 300mm since all of youse guys were twinkles in Mommy's eyes.

Without knowing that, who can say anything about this car?

---

John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
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An argument could be made that with proper springs and damper settings, the general 30% rule should apply. If you are bottoming out, go stiffer or raise the car as a short band-aide fix. The real solution would be more travel. The reason mx bikes have 12in of travel is beacause of the surface (obviously). Pavement pounders run 2in of travel because of the smooth (sometimes) surface. They all run 30% sag though. If the track is harsher or smoother, you can change spring rates (yeah right!) or drive faster or slower.

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Robert Culbertson
An argument could be made that with proper springs and damper settings, the general 30% rule should apply. If you are bottoming out, go stiffer or raise the car as a short band-aide fix. The real solution would be more travel. The reason mx bikes have 12in of travel is beacause of the surface (obviously). Pavement pounders run 2in of travel because of the smooth (sometimes) surface. They all run 30% sag though. If the track is harsher or smoother, you can change spring rates (yeah right!) or drive faster or slower.

Current tarmac rally cars are at around 200mm/8"

---

John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.

Quote
john vanlandingham

Current tarmac rally cars are at around 200mm/8"

I should have been more specific. I was talking about roundy rounders or club (hah!) racers like SCCA.
I do agree that it does depend a lot on the surface and conditions. But, there seems to be this range that everyone runs in. Except formula un. They run practically no droop and crazy as all get out linkages+more linkages+6 shocks per corner stuff.

What spring rates are they running on tarmac rally cars? I guess more in comparison, same car, just tarmac vs gravel.
My golf runs 450 lb/in F and 350 lb/in rear for circuit racing. I have 225lb/in F and 175 lb/in R for gravel. So it's basically halved.

Quote
Robert Culbertson

Quote
john vanlandingham

Current tarmac rally cars are at around 200mm/8"

I should have been more specific. I was talking about roundy rounders or club (hah!) racers like SCCA.
I do agree that it does depend a lot on the surface and conditions. But, there seems to be this range that everyone runs in. Except formula un. They run practically no droop and crazy as all get out linkages+more linkages+6 shocks per corner stuff.

What spring rates are they running on tarmac rally cars? I guess more in comparison, same car, just tarmac vs gravel.
My golf runs 450 lb/in F and 350 lb/in rear for circuit racing. I have 225lb/in F and 175 lb/in R for gravel. So it's basically halved.

Escort and Sapphy 4x4 tarmac FRONT was around 450...for a car that weighed 1230kg

215 rear for 4x4 tarmac

Gravel: progressive front, mid stroke about 325-350 front, 195 rear on 4x4.
RWD ran same in front, around 173 in back

How much travel you have on both set ups?

---

John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.

The road racing setup is Bilstein Sports with coilover sleeves. At ride height I have about 3in of travel, including shaved bump rubbers (stock).
The gravel set is HDs that have the valving changed to who knows what (I'll be sure to check next time they come off), and set at 35% sag I think.

I just measured my car.
40% sag up front
35% sag in the rear

I think the shock only travels maybe 5". I'd have to measure what that equates to wheel travel.

I can get more or less sag in the rear easily (just remove the torsion bar housing and turn in a few degrees). The front is already maxed out at 40%. (could lower the car)

Quote
johnhuebbe
I just measured my car.
40% sag up front
35% sag in the rear

I think the shock only travels maybe 5". I'd have to measure what that equates to wheel travel.

I can get more or less sag in the rear easily (just remove the torsion bar housing and turn in a few degrees). The front is already maxed out at 40%. (could lower the car)

seen your car go, it LOOKS good but bigger question is are you happy?

What's it doing?
What are you hoping to do?

---

John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.

The asphalt oval tarck car I currently drive has 185lb up front with 1 1/4" sway bar. 185 lr and 600 rr. cars 2600lbs with me and full of fuel. I say lower the car as low as possible without bottoming out to bad and rally it. The super has ride hieght scrapers we set the front cross member 1/2" off ground racing. it equates to about 7" off ground up front in the pits. This car has major down force not f1 but lots compared to a rally car.

I switched to Swift springs in the rally car for this week. Running 200 lb up front and 175 in back. 3244 lb with spare tire,tools with out driver co driver. I upped my high speed compression and lowered my low speed compression as low as it can go. I set rebound 2 clicks from full rebound. up front. the rears are still low to mid compression with 2 clicks from full rebound. im starting with the car about 8" ride height. hoping to be in the 5" range at speed. Hopefully it isnt to bumpy up there I may have to raise the car a little.

I believe I stress I the key to speed is as low and as soft as possible asphalt and gravel as long as the conditions allow. if its to rough raise the car. I dont get and may never get why track cars run such stiff springs?

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First rally 2013
Rally car type AWD subaru
Total rallies as driver 6
Total rally cars built 2
Total rally cars caged 3
Total rally cars repaired from offs 4
Total years racing exp other then rally 19 yrs
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Quote
john vanlandingham

seen your car go, it LOOKS good but bigger question is are you happy?

What's it doing?
What are you hoping to do?

Happy, yes.

With the rear at 35%, sometimes it feels too loose or wollowie in turns. Like it needs to be a bit lower.

I'm just trying to get an idea of how the car should be properly setup. Just make sure I'm not running too high/low. Seems like it is set in the ball park of what everyone else says.

Quote
Robert Culbertson
My golf runs 450 lb/in F and 350 lb/in rear for circuit racing. I have 225lb/in F and 175 lb/in R for gravel. So it's basically halved.

Sway bars?

Quote
Iowa999

Quote
Robert Culbertson
My golf runs 450 lb/in F and 350 lb/in rear for circuit racing. I have 225lb/in F and 175 lb/in R for gravel. So it's basically halved.

Sway bars?

No bars on the car. The rear is a trailing axle, so it's already pretty stiff. It still has a bit of understeer on turn in that I would like to get rid of. I have thought about swapping springs front to back to stiffen up the rear. The weight biasis totally jacked on these cars. 66% front is a little excessive. My car needs a diet.