Gravel Spec vs. Tarmac Spec dampers

I'm wondering what are the differences between gravel spec and tarmac spec coilover setups is.

I figure a tarmac spring is going to be stiffer than a gravel spring. But I wonder the difference between valving and compression/rebound characteristics.

I figure a gravel coilover setup(say bilstien 40mm with 12-14" spring) is going to be great in gravel OK on tarmac. It'll let the body of the car roll a bit more.

I figure a tarmac coilover will be great on tarmac, but would suck offroad.

So if I can only afford one set, what to get. What is car going to be used for? mostly tearing it up in fields, down trails in the woods, autocrosses, hill climbs and trips to the grocery store.

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Michael LeCompte

pikespeakgtx Wrote:
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> I'm wondering what are the differences between
> gravel spec and tarmac spec coilover setups is.
>
> I figure a tarmac spring is going to be stiffer
> than a gravel spring. But I wonder the difference
> between valving and compression/rebound
> characteristics.

The GOAL is different so naturally the tools are different.
Some Froggie Injur-near at Mitsubitchy said it the clearest I've seen:
"On gravel we're chasing GRIP; on tarmac were chasing handling"
>
> I figure a gravel coilover setup(say bilstien 40mm
> with 12-14" spring) is going to be great in
> gravel OK on tarmac. It'll let the body of the car
> roll a bit more.

Yep and that's why for "Fast road" cars I deliver straight gravel rates both spring and damper. Works well, you'll feel the car settle down but still firm for bumps.
>
> I figure a tarmac coilover will be great on
> tarmac, but would suck offroad.

Actually real tarmac settings will rattle your kidneys, loosen your fillings and shake your britches around your ankles on anything short of perfectly groomed racetracks.
Can't drive too well when your pants are wrapped up in the pedals, eh.
>
> So if I can only afford one set, what to get. What
> is car going to be used for? mostly tearing it up
> in fields, down trails in the woods, autocrosses,
> hill climbs and trips to the grocery store.

Gravel spec from somebody who has a clue what to supply.
>
>

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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.

Go check out all the Ford motorsports manuals. They show the difference. But what really matters is this: A car setup for gravel is still a fucking blast to drive on tarmac. The only real thing you might want to change between the two is sway bars. Oh, and go and do a track day, just once and you'll never waste your time at an autocross again. I love the way my Merkur on JVAB stuff feels driven fast on tarmac and I never have to even consider or worry about suspension on gravel/dirt.

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Grant Hughes

john vanlandingham Wrote:
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>> > I figure a tarmac coilover will be great on
> > tarmac, but would suck offroad.
>
> Actually real tarmac settings will rattle your
> kidneys, loosen your fillings and shake your
> britches around your ankles on anything short of
> perfectly groomed racetracks.
> Can't drive too well when your pants are wrapped
> up in the pedals, eh.
>

Yes, it's true. For instance the spring rates on the Speed World Challenge road race car I'm working on are 1600 lbs front and rear! This for a car with 50/50 weight distribution and a similar weight to a Subaru rally car. Most rally springs for a Subaru are in the 200-250 lb range.

Something else to keep in mind is suspension travel. A full on road race car will have (only needs) a fraction of the suspension travel of a rally car. An ALMS GT2 car, for example, only has 50mm of ground clearance. When a Prototype car gets a flat rear tire it will pick the opposite front tire off the ground and teeter because there is virtually no droop. A tarmac rally car needs more travel (and a softer spring) than a full on circuit race car but less than a gravel rally car. It may be on tarmac but it's still a real road and it's bumpier than a circuit and they're cutting corners and there's the occasional gravel patch, etc.

"Can't drive too well when your pants are wrapped
up in the pedals, eh. "

No indeed.

JVL, what gravel setups have you made for the GTX's in the past? I remember seeing a set for a mazda on your website in some of the random pictures. What's the max spring length on those 40mm bilstein tubes which are suited for the gtx?

From talking with Bret Norgaard at bilstien they do have 50mm tubes for the GTX but seems like a little too much, having to run wider springs and cramming it all under the wheel well... Any thoughts are appreciated.

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Michael LeCompte

"Can't drive too well when your pants are wrapped
up in the pedals, eh. "

No indeed.

JVL, what gravel setups have you made for the GTX's in the past? I remember seeing a set for a mazda on your website in some of the random pictures. What's the max spring length on those 40mm bilstein tubes which are suited for the gtx?

From talking with Bret Norgaard at bilstien they do have 50mm tubes for the GTX but seems like a little too much, having to run wider springs and cramming it all under the wheel well... Any thoughts are appreciated.

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Michael LeCompte

I've got some 14" springs on my Sooper Bitchinâ„¢ suspenders. They're made for the BG chassis, though, not the BF, and I haven't installed them to see ride height, etc. yet. Stupid car's got a foot of snow over its roof and it doesn't look like it's going to leave anytime soon.


--sarge

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---** To be in compliance with the Anarchy **---
Jorden R. Kleier
Baraboo, Wisconsin, USA
1990 Mazdog Protege 4WD
1973

Sarge you have a BG chassis 4x4 gtx?

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Michael LeCompte

We have successfully run the Sooooper Bitchin things with 14" front and 18" of rear spring on Tarmac.

All we do is lower the perches till the car is at roughly factory ride height which translates to about 20-25 turns below what we run on the gravel.

4th OVERALL at rally TN last year
Top 10 OVERALL at Rally TN and Rally NY tarmac stages too


For the Golf at least--we don't make any other changes.
Springs ~250 front, ~180 rear
Swaybars--None in Front, Stock in rear...

If our little golf handles well enough to keep up with the EVOs and STIs with REAL Tarmac rally suspensions AND turbos, AND awd, I don't see any need to develop a separate "tarmac" setup

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____________________________________________________________-

One. Class -- 2WD

www.quantumrallysport.com

http://www.facebook.com/home.php?#/pages/Quantum-Rally-Sport/281129179600?ref=nf

pikespeakgtx Wrote:
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> Sarge you have a BG chassis 4x4 gtx?
>

I wish!!!

Well, I do have the front half of one. But the car I'm putting this on is a '95 escort station wagon, which so far has seen exlusive use on Tarmac (autoX and lapping days, and going to work every day.)


--sarge

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---** To be in compliance with the Anarchy **---
Jorden R. Kleier
Baraboo, Wisconsin, USA
1990 Mazdog Protege 4WD
1973

When I run tarmac with eteh nissan 240sx and SBS, I leave the spring rates alone, lower the ride height, run bigger front bar, and use a rear bar... and make sure the wheels are all pointing in the right direction.

-Martin.

... and make sure the wheels are all pointing in the right direction.

I bet that really helps.

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Michael LeCompte

I found a cool little video on youtube about WRC dampers.. Pretty basic, cool nonetheless. Check it out...

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Michael LeCompte