JoeMag

I had come across these in Bruce Anderson's book a while ago and saw on another race car. They're perches that allow the spring to be screwed into and out of it to adj spring rate. ...anyone use'n them? comments?

Greg Smith

Yo no comprendo.

JoeMag

Here's another pic. See how spring can be wound up or down inside that groove? You are taking coils (probably partial coils) out of the spring. Decrease number of turns and spring rate goes up. Number of turns goes in denominator of spring rate. ie: if you take 1000# springn with 10 turns and make it 9, the rate goes up by 10/9, up to 1111#. ...these springs look to have 4 maybe 5 turns so if you can take out 0.5 turns you can change spring rate by ~10%.

Professor Helmüt Tester

NASCAR calls them 'bump rubbers'.

AudiOn19s

Interesting. I've never seen these either although Nascar does use them in a more simplified form with their "spring rubbers" that are simply inserts that are shoved inbetween the coils to do the same thing. This device seems to be a bit more complicated but appears to do the same thing.

Considering that spring rate is supposed to be the best primary method for tuning a car I'm suprised we don't see more of these types of things on the market. Then again maybe because springs themselves are soo cheap there's really no need?

Andy

JimB

I have them along with triple adjustable Motons on the 996 race car I'm selling. They are pretty trick. As I recall, every quarter turn adds something like 50 lbs of spring rate.
Jim

95m3racer

Its a clever component, has been around for quite some time.

Do you happen to know which manufacturer made yours?

Unfortunately it does have its drawbacks, but having the ability to change spring rates without disassembling the shock is definitely a big plus. The drawback is you lose compression travel. You are effectively changing the length of the spring. I think its best purpose would be to dial in a spring rate during skid pad testing for preliminary spring rate design.

Ad the other obvious drawback is you need the specific type of springs that are able to be "threaded" into the perch.

Rick DeMan

Those setups came factory stock on all GT3R thru RSR factory built race cars. They work just fine and have no drawbacks with spring length issues. Spring rate was 4 position adjustable a snap to change.

I have 6 sets available if anyone is interested....

95m3racer

Rick, what size springs are they for? Do you have springs available?

I sent you an email.

JimB

Mine are from the RSR. I couldn't see any drawbacks. They work great.

coryf

I have always heard them referred to as 'Versa' springs on the factory cars.
There are 2 downsides to using them. First is that you have a limited range of adjustment-if the softest setting is too stiff, you are out of luck. The second issue is that rate changes require you to move the spring perch. It is still quicker than a spring change, but not by much.

It is a clever design, and still very useful in some applications, but not many teams use them. I expect you could find quite a few take-offs for sale.

Rick DeMan

I would totally disagree about being not much less time....Porsche manual says for 1 increment change in spring rate move the ride height lock plate 4 turns. I've used these quite a bit and it takes less than 5 minuets to pull the wheel, adjust the spring rate, move the locking collar, reinstall the wheel, torque and fire back onto the track.

Changing a spring would take much more time.

Factory rates for the front and rear springs are as follows.
1st setting 282 N/mm
2nd 293 N/mm
3rd 317 N/mm
4th 345 N/mm

Optional rear spring available.

1st stage 317 N/mm
2nd 333 N/mm
3rd 352 N/mm
4th 375 N/mm

Rick DeMan

I do have various factory springs, some H&R springs made for the factory perches and many "Versa" spring perches. I will try to gather up what I have and get a list on here. They are all threaded for Factory Sachs shocks and will fit many others..Bilstien and Moton...etc.

coryf

You haven't seen our guys do a spring change
If you're geared up for it, spring changes can be done incredibly quick.

Still, the biggest drawback to these springs is the rates, the minimum (282N/mm) is over 1600 lbs/in. If all you work with are 1600 and up, then they are a good choice.

95m3racer

I do some issues from both a time perspective, and a performance stand point.

You will have to determine a precise ratio for what each setting on the adjuster is compared to the ride height change. This is not hard, but something you'll definitely have to keep track of, or your corner weights will be off.

Depending on the shock configuration, some springs can be swapped extremely quickly. If a shock is built to be a "quick release" (positive locking bolts, etc), but I do see where this can come in handy during initial setup. I'm also curious as to the compliance issues that might come up in dynamic conditions. The spring should still have needle bearings so it is not restricted from rotation while under compression.

A simple idea I have is to just make a solid insert in various sizes to fine tune the spring, same exact technique, it just is placed within the coils...only issue here is you can end up with a point load on a coil, which can be an issue for cyclic failures popping up. I do notice on the units above it has a flat top so the spring compresses to a point and is compressed onto a flat plane.