DSE Quad link rear suspension tuning

[67ragtp]

Im finally done with all the mods to my LS7 engine and have it tuned the way I like. The throttle response and low speed torque has really increased. So im moving to the back of the car to try and get some more plant the rear tires performance. I run the rear sway bar on the stiffest setting and currently have a 275lb springs on jri double adjustable shocks. As I accelerate out of a sweeping turn the back gets loose and skips out. The shocks are set up to dse recommendations. The rebound adjustment is 20 sweeps from full dampening, I don't know a lot about suspension tuning and was wondering is full dampening the stiffest setting? Also wondering if the springs are to stiff and how the bar plays in to the spring rate. Any suggestions on how to get it, to become more complient and grip a little better is appreciated.

Thanks Rich

[Ron Sutton]

Before you get into full bore tuning ...

a. Do you have a safe place to test?
(Meaning safe for you AND others)

b. Have you started adjusting on the shocks yet?

c. Are you prepared to change springs or bars to achieve your goals?

[67ragtp]

Before you get into full bore tuning ...

a. Do you have a safe place to test?
(Meaning safe for you AND others)

b. Have you started adjusting on the shocks yet?

c. Are you prepared to change springs or bars to achieve your goals?

a. yes

b. no

c. spring change is not a problem, would prefer to keep the bar.

[Ron Sutton]

Okie dokie, first step would be to start with baseline shock settings in the middle, go test with "just" shock adjustments & take very detailed notes every change, every "run".

You didn't say if your double adjustable shocks are compression & rebound adjustable or if both adjustments are for rebound (low speed & hi-speed piston travel).

If they are compression & rebound adjustable, do this:

a. Soften the compression on the fronts until you get the car "loose on entry" when braking & turning ... or until you run out of adjustment.

b. Stiffen the rebound on the fronts .. and see how much better the car turns "mid-corner" when you're "rolling or coasting" with no brakes or throttle. Also pay attention to what it does to the rear tire grip on corner exit. It will get looser. Note the settings when it does.

c. Stiffen the compression on the rears as long as it helps the car turn on entry & middle ... or until you run out of adjustment.

d. Soften the rebound on the rears until you get the car "loose on entry" when braking & turning ... or until you run out of adjustment.

---------------------------

Then ...

e. Stiffen the rebound on the rears to see if will provide you with more grip on corner exit. Pay attention to when it affects grip on entry & middle.

f. Soften the compression on the rears to see if will provide you with more grip on corner exit. Pay attention to when it makes the car tighter or pushy on entry & middle.

g. Stiffen the compression on the fronts until you get the car to push on entry and/or middle ... or until you run out of adjustment. You'll be able to drive in deeper & brake harder, but pay attention to the middle as it gets tighter or pushy.

h. Soften the rebound on the fronts .. and see how much better the car grips on corner exit as you roll the throttle on. Also pay attention to when the push comes back or gets worse in the middle. If it starts to push on exit ... stop.

Please do these in this order & take lots of notes. You won't be able to remember all the details accurately. I don't know any top race teams that don't use "run sheets" to keep track of changes, results, etc.

Then, post a report of each run, with all 4 shock settings, the handling results on corner entry (braking & turning), Middle (coast) & Exit (throttle roll on & steering unwind) ... and the differences from the previous run.

You'll learn first hand what changes do ... I'll guide you on what every thing means to us from what you post ... and people following along can learn & share their experiences too.

[67ragtp]

Ron,

Thanks for the advice, the shocks are only rebound adjustable high and low speed.

[Track Junky]

Taking rear bar out of it will relieve the car from getting loose. Not sure why you went to the stiffest setting. Was this also a DSE reccomendation?

And Ron's right......You wont get any faster without taking notes

[Ron Sutton]

Ok … since both adjustments are for rebound (low speed & hi-speed piston travel) do this:

a. Soften the high speed rebound on the rears until you get the car "loose on entry" when braking & turning ... or until you run out of adjustment. This will help the car turn better on entry & middle.

Note the settings when it does get loose & back up a step.

b. Stiffen the low speed rebound on the fronts … and see how much better the car turns "mid-corner" when you're "rolling or coasting" with no brakes or throttle.

Pay attention to what it does to the rear tire grip on corner exit. It should get less traction. Note the settings when it does.

c. Stiffen the low speed rebound on the rears until you get the car "loose on entry" when braking hard & turning ... or until you run out of adjustment. Note the settings when it does get loose & back up a step.

Pay attention to what it does to the rear tire grip on corner exit. It will get more traction. Note the settings when it does.

It “may or may not” tighten up the car mid corner. If it does, note the setting & back up some.

d. Stiffen the high speed rebound on the fronts … and see how much better the car turns "mid-corner" when you're "rolling or coasting" with no brakes or throttle.

Pay attention to what it does to the rear tire grip on corner exit. It should get less traction. Note the settings when it does.
---------------------------

Then ...

e. Stiffen the high speed rebound on the rears until you get the car "tight on entry" when braking & turning ... or until you run out of adjustment. This may make the car harder to turn on entry & middle … potentially creating a tight/pushing condition.

Note the settings when it does get too tight or pushing & back up a step.

f. Soften the low speed rebound on the fronts … and see how this makes the car harder to turn "mid-corner" when you're "rolling or coasting" with no brakes or throttle.

Pay attention to what it does to the rear tire grip on corner exit. It should get more traction. Note the settings when it does.

g. Soften the low speed rebound on the rears to see how it affects the car on entry when braking hard & turning ... this may tighten or loosen the car on entry & may not, depending on other factors Note the settings if it does change.

Pay attention to what it does to the rear tire grip on corner exit. It will have less traction. Note the settings when it does.

It “may or may ” loosen up the car mid corner. If it does, note the setting & back up some.

h. Soften the high speed rebound on the fronts … and see how this makes the car harder to turn "mid-corner" when you're "rolling or coasting".

Pay attention to what it does to the rear tire grip on corner exit. It should get more traction. Note the settings when it does.

Please do these in this order & take lots of notes. You won't be able to remember all the details accurately. I don't know any top race teams that don't use "run sheets" to keep track of changes, results, etc.

Then, post a report of each run, with all 4 shock settings, the handling results on corner entry (braking & turning), Middle (coast) & Exit (throttle roll on & steering unwind) ... and the differences from the previous run.

You'll learn first hand what changes do ... I'll guide you on what every thing means to us from what you post ... and people following along can learn & share their experiences too.

[intocarss]

That's good info ......Thanks Ron :thumbsup:

[Track Junky]

That's good info ......Thanks Ron :thumbsup:

Agreed. Ron, when I get my Penske's I'm dragging you out to the track with me. :whistling:

[Ron Sutton]

Agreed. Ron, when I get my Penske's I'm dragging you out to the track with me. :whistling:

Let's dial in the valving curves first. We need to adjust the bleeds & shim stacks to get the low speed rebound numbers where we want them for grip ... without the high speed numbers being so stiff it upsets the car over rough surfaces.

What model of Penskes are you planning to buy ?

[Matt@BOS]

Hey Rich, first thing you might want to do is soften the rear bar. It will probably make a drastic differemce one way or another. I don't remember if we've discussed your front spring rates and bar, but if you let me know I can dig up some notes and we can compare feedback. If my notes match what you're experiencing, I might be able to help a little, and at least give Ron enough info to narrow down possible solutions.

[Track Junky]

Let's dial in the valving curves first. We need to adjust the bleeds & shim stacks to get the low speed rebound numbers where we want them for grip ... without the high speed numbers being so stiff it upsets the car over rough surfaces.

What model of Penskes are you planning to buy ?

Planning on the 7500 DA's. I still need to weigh the car and calculate motion ratios before I order them. The guy that is going to build them for me is in Roseville.

[67ragtp]

Taking rear bar out of it will relieve the car from getting loose. Not sure why you went to the stiffest setting. Was this also a DSE reccomendation?

And Ron's right......You wont get any faster without taking notes

To be brutally honest with you, I consider myself a pretty good wrench but when it comes to understanding suspension/handling set up, Im lost and need to learn. Im sure it wasn't a DSE recommendation, I often look at other illustrations to see what holes are being used.

Lots of rain in Jersey, as soon as I can get out I will try to get some testing documented.

Matt- Im running 550# front hyperco's front bar is set where DSE delivered it and the JRI shocks are set to there recommendation in the manual. It turns in real nice with the camber set up at negative 1.5 degrees toe in 1/16.

[intocarss]

To be brutally honest with you, I consider myself a pretty good wrench but when it comes to understanding suspension/handling set up, Im lost and need to learn. . I feel your pain! I've been "trying" to learn road course and dirt set ups (two different cars & totaly different set ups) Going straight sure is much easier LOLOL

[Track Junky]

To be brutally honest with you, I consider myself a pretty good wrench but when it comes to understanding suspension/handling set up, Im lost and need to learn. Im sure it wasn't a DSE recommendation, I often look at other illustrations to see what holes are being used.

Lots of rain in Jersey, as soon as I can get out I will try to get some testing documented.

Matt- Im running 550# front hyperco's front bar is set where DSE delivered it and the JRI shocks are set to there recommendation in the manual. It turns in real nice with the camber set up at negative 1.5 degrees toe in 1/16.

DSE gave you a recommended shock setting. If it were me I'd be using that as a baseline but the bar is definitely to tight.

[Ron Sutton]

Planning on the 7500 DA's. I still need to weigh the car and calculate motion ratios before I order them. The guy that is going to build them for me is in Roseville.

Mike is a wonderful guy to work with. We've been friends & working together for years and only 1 of 2 shock guys I work with. He & I are working on revalving a different brand of shocks for a serious PT guy currently.

If your budget will allow, I'd like to suggest you consider either the Penske 7300DA with base valve or JRI ST/08 DA with base valve. I'm guessing we're talking about 20-30% more $, but the performance difference is worth it, if you can afford it.

I'm a big proponent of racing within your budget, but at the same time, I don't like to make a purchase & then need repurchase something again to achieve my goals.

Talk to Mike about those two options, get his opinion & prices, then decide what works best for you.

P.S. Both are great shocks, but the JRI's have a tick less "stiction" and a broader range of adjustability.

[Track Junky]

Mike is a wonderful guy to work with. We've been friends & working together for years and only 1 of 2 shock guys I work with. He & I are working on revalving a different brand of shocks for a serious PT guy currently.

If your budget will allow, I'd like to suggest you consider either the Penske 7300DA with base valve or JRI ST/08 DA with base valve. I'm guessing we're talking about 20-30% more $, but the performance difference is worth it, if you can afford it.

I'm a big proponent of racing within your budget, but at the same time, I don't like to make a purchase & then need repurchase something again to achieve my goals.

Talk to Mike about those two options, get his opinion & prices, then decide what works best for you.

P.S. Both are great shocks, but the JRI's have a tick less "stiction" and a broader range of adjustability.

I'm glad you know of him. That reassures the prior recomendation. I'll look into the 7300 Da's.

Is there anybody local that you know of with a set of scales?

[Ron Sutton]

I'm glad you know of him. That reassures the prior recomendation. I'll look into the 7300 Da's.

Is there anybody local that you know of with a set of scales?

7300DA's ... with a base valve option. The basevalve is a big deal, allowing the shock to follow irregular surfaces better for more grip.

I sold my last set of wireless Intercomp scales to make a package deal. I kept my roll on scale platen, which is the bigger cost by far, but I need to buy another set of wireless Intercomp scales to go on them.

I have a long time racing buddy that will loan me his anytime. We'll need to scale your car at his shop or mine. If you really want to get trick, and learn a lot, we'll book time on a pull down rig.

[Track Junky]

Sounds great. Lets get together at your shop when you free up. It will have to be a weekend for me. PM with more details, contact info, and shop location. :thumbsup: