924Board.org

[bacook]

Who is using coilovers out there for track and autoX cars? What are the differences between the $250 and $2500 parts?

[924RACR]

I am on my ITA car. However, I'm not sure what you mean, differences between the $250 and $2500 parts? Are you referring only to the springs and adjustable spring perch setups, or are you also referring to shocks?

_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

[bacook]

I guess that's what I don't understand. From what i can tell, there are three components to this setup: the springs, perches, and shocks. Is that all there is? Are coilovers just a tunable strut that you can divverent types of shocks in?

[924RACR]

Heh heh... big whole mess... OK, first to explain the terms... coilover refers to a shock that has a spring around it - in other words, the two are co-axial. 924's do not have these on the rear from the factory, since they have torsion bars. However, it's a popular aftermarket mod, since you don't have to replace the torsion bar, which can be a PITA, and spring rates are more easily changed out without realigning the car (req'd when changing torsion bars). However, it is common to first have to re-index the torsion bars to compensate for the change in ride height due to the added spring rate.

Naturally, the front strut suspension is often considered a coilover, from the factory. What is usually done to this for performance is, in addition to replacing the shock, replace the stock spring and spring perch with a smaller-diameter higher-rate race spring and an adjustable perch.

So, I'm not sure exactly what you're considering; you may wish to go check out my website, look on the Construction page to check out my setup. I currently have adjustable spring perches up front, w/ 400lb springs and spherical bearings, camberplates, Koni yellows all around (soon to go away for true race shocks) and 30mm torsion bars in the rear... still working on finishing off a proper spherical bearing setup for the rear, as well as some solid mounts for the rear suspension.

Hope that helps.


_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

[Peter_in_AU]

so Vaughan,

when you put coil-overs on the rear do you dial-out all the "spring" from the torsion bar and have the coil-over springs take all the load or do the coil-over springs and the torsion bar work together?



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1979 924 (Gone to a better place)
1974 Lotus 7 S4 "Big Valve" Twin-cam (waiting)
1982 924 (As featured on Wikipedia)

Learn to love your multimeter and may the search be with you

[924RACR]

Depends! Some guys delete the torsion bars altogether (the GT guys), some use the smallest torsion bars they can find (the 22mm ones from the early 924), usually the more competitive Prepared guys, and some leave their stock bars in and just add "helper" type coilover springs (typical for stock classes).

Me, of course, I just use the big torsion bars, since coilovers in the rear are illegal for me.

_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

[-nick]

alot of racers just grind down the rear torsion bars to a minimal diameter so that they have a negligable affect on the spring rate. this way you still have the 'stock' torsion bar setup, but all the spring is really coming from the coilover. this is the way to do it if you want to race in PCA stock classes.

-nick

[Benski]

Vaughan is right, a coil-over just means that the spring is wrapped around the shock. But something is usually referred to as a coil-over (and not just a strut or a spring and a shock) when the ride height is adjustable.

On full-race coilovers (the kind you see for $2500), the damper is valved for competition - stiff compression and rebound - and is usually extremely adjustable.

Coilover "kits" are usually just adjustable spring perches that you can fit around your existing shocks.

Ben

[924RACR]

Yeah, sorry, guess I never really reviewed the shock setups available.

Street/sport shocks are commonly available with no adjustment, usually valved just a little bit stiffer than stock, or with only one adjustment, which will be rebound only. Examples are the commonly-used Koni yellows or some Bilsteins, which can both be rebuilt, in addition to re-valved (to change the damping rates, both compression and rebound).

Race shocks come in many flavors. Some are non-adjustable, but revalveable - Bilstein makes a 924 race shock like this, which I believe may be a left-over development from the 933 days. Actually, any true race shock will be rebuildable and revalveable.

Some are double-adjustable, meaning there is an adjustment for both compression and rebound damping. The 944/951 M030 shocks are a perfect example of this.

Then you get into the expensive shocks - no, we're not there yet! There are also triple- and quadruple-adjustable shocks, meaning different adjustments for high and low speed damping. Often though, they must be taken apart to change the settings. Why would you do this? Well, rallye or touring car are perfect examples; very stiff for tight control over small displacement low-velocity stuff, but very soft for the big hits, like smacking curbs or boulders or jumps. Wish I could put these on my car, but can't afford them and they're illegal anyway in IT!

There's also remote-reservoir shocks, which have a separate fluid reservoir which allows higher durability, due to a better heat-absorbtion capacity (from the larger volume of damping fluid) for better performance in longer races, as well as (apparently) finer tuning of damping characteristics.

Then, of course, we add in flavors such as threaded body or non, and aluminium vs. steel or whatever bodies.

Cool?


_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

[data]

When going to a coil over setup it is best to remove the rear torsion bars. If left in
place it will throw off the effective spring rate due to erratic rebound and compression.
The 1500-2500 coil over packagages will require the removal of the rear torsion bars
because being fully adjustable it would be dialed in to the springs supplied and not to
the combination of both. for track setup 400 lbs front springs are too soft a good track setup would be 600lbs front 450-500 rear springs on a 2500 lb car.

[924RACR]

What exactly do you mean, erratic rebound and compression?

_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

[Michael Kouridakis]

I noticed 2 blue paint dots on my front springs. What do they mean?

I just put Kumho Ecsta Supra 712 205/50/15's all around. Now I can really feel how soft the stock suspension is. I don't believe that my 931 has the optional performance susp package. I don't see M030 on the sticker in the trunk area.

Stiffer is better, right?

[Rick MacLaren]

Stiff is always good.

[Rick MacLaren]

Stiff is always good.

[AppleBit]

stiff for solid surfaces

not so stiff for gravel surfaces

- Jon


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