Hi Ron,


what do you think about the forces (velocity) rebound and compression with. Is this to stiff  or soft? I have 700 springs on front axle? in europe they sadly have no experiences.
Shocks are from ohlins lmj.
727lb corner weight 50/50 square.
roadcorse.

thanks andi

Hi Ron,


what do you think about the forces (velocity) rebound and compression with. Is this to stiff  or soft? I have 700 springs on front axle? in europe they sadly have no experiences.
Shocks are from ohlins lmj.
727lb corner weight 50/50 square.
roadcorse.

thanks andi

A few things,

First, please convert the numbers to US equivalents for me. I need pounds of force & inches per second.

Second, the compression ramp SHAPE looks OK, but I can't tell how much force is there.

Third, the the rebound ramp looks horrible.  Way too much rebound for a linear curve like you have. I suggest you have it revalved with a digressive piston on the rebound side. Again, I can't tell how much force is there.

Hi Ron,
here are the specs in Us

And the last Picture is the Rear

[red, blue & green]

First, I moved this topic here, since this is where I have all my shock information.

Second, thanks for saving me the work to convert the math.

Third, refer to Topic, Methods & Strategies to Increase Overall Grip, reply #5, section #24 of the topic.  The first image & text refer to areas of reading shock dyno graphs.

Here is that image & text.



Regarding the Dyno Graph Sheet Above:
Previously, I didn't share anything about the fourth & most important area of shock valving. That is the Zero to 1 Inch Per Second range of shock travel. That is actually the final frontier of shock tuning. That is where we find the last little bit of grip to beat our competitors. You can see why I didn't share before. Now I'm willing.

The red, blue & green circles are still accurate. Let's just add a 4th area, in between the red & blue, where we work on grip on relatively smooth surfaces. I'll refer to is as the 0-1 IPS area of shock piston travel.

So now we have 4 areas of focus on shock valving:
#1 - Zero Number, which is our tie down force
#2 - 0-1 IPS, which is our grip on relatively smooth track surfaces
#3 - 1-3 IPS, which is our grip on average track surfaces
#4 - 5-10 IPS, which is the force we see from typical race track bumps.

There could be a 5th area of focus, if you're jumping curbs on track. That would be the shock shaft & piston speeds we see above 10 IPS. 

[You'll notice in the shock graph above:]

So converting your graph to SAE numbers, that we are about, looks like this:
*All numbers are interpretive of a line graph & may be off a few pounds.

Compression Red Line:
0 IPS = 0#
.5 IPS = 25#
1 IPS = 50#
3 IPS = 80#
5 IPS = 110#
10 IPS = 155#
20 IPS = 250#

Rebound Dark Line:
0 IPS = 0#
.5 IPS = 60#
1 IPS = 120#
3 IPS = 215#
5 IPS = 295#
10 IPS = 470#
20 IPS = 800#

You asked for my feedback.  Here goes.

A. The shock is almost linear. It has a small digressive action at 1 IPS (25mm) on both sides (compression & rebound).

B. Linear is good on the compression side. Your slight digressive action at 1 IPS (25mm) on the compression side is also fine.

C. The valving forces all up & down the compression valving is good. It is similar to what we run in our shocks. My compression valving is about 30% softer than yours, but yours will work fine.

D. The almost 100% linear valving on the rebound side, in this case for a front shock with significant rebound valving is bad. Very bad. The rebound side of your valving needs to be very digressive, like the example below.



You'll notice in the shock graph above:
1. When I adjust the shock rebound valving (with a knob or dial on the shock) I am adjusting the the valving PRIMARILY 3 IPS & below.
2. No matter where I adjust the shock rebound valving (with a knob or dial on the shock) the shock valving above 3 IPS doesn't change much.
3. The Digressive action happens just after 400# of rebound. That is where the valving curve "blows off" or "kicks over" and doesn't gain much force with additional piston speed.
4. The entire range of adjustment is 575#-590# @ 5 IPS & 595#-610# @ 10 IPS. The goal of this is to prevent the front wheels from skipping over undulations from being too stiff.

Your shock rebound valving is stiff in the wrong area of usage. We want high rebound at lower speeds to increase grip. But your shock is soft on rebound down at lower shaft/piston speeds. You are giving up grip. 

What you need are Linear/Digressive pistons ... linear on compression & digressive on rebound ... to achieve much higher rebound force at 0.5 IPS (12mm) up to 3 IPS (75mm).

Whether you add high Zero number, depends on your suspension strategy.  You should read all of this thread & get back to me on here. Methods & Strategies to Increase Overall Grip

Frankly, if you only run road courses, you'll benefit (go faster) from more agressive rebound valving than shown above. That is our AutoX valving. Our Track Car valving (for road courses) looks like the graph below.

Hi Ron, thanks for the detailed answer.
I need to read it several times to understand it 🙃.
Two questions: Is my rebound generally too harsh, or is it just the curve that's bad?
If I understand correctly, I need a different curve up to IPS3 and then a linear one after that?

Will the rear axle setting remain as is? I switched from a locker to a Gleason differential this winter.

Thanks a lot.

Hi Ron, thanks for the detailed answer.
I need to read it several times to understand it 🙃.
Two questions: Is my rebound generally too harsh, or is it just the curve that's bad?
If I understand correctly, I need a different curve up to IPS3 and then a linear one after that?

Will the rear axle setting remain as is? I switched from a locker to a Gleason differential this winter.

Thanks a lot.

It is the curve that is bad. Your front rebound valving is linear. It needs to be digressive.

You don't have too much rebound.  But due to the linear curve, you have too much for bumps & not enough for tie down or grip.

Will the rear axle setting remain as is? I switched from a locker to a Gleason differential this winter.

Your rear axle valving is not bad. That's not an issue. The front is out to lunch.