what pound springs are you track people running up front
05-12-2012, 03:04 PM
#16
Rocket Scientist
Rennlist Member
Rennlist Member
Where did you get 56% from, Tony? I'm curious. The last car I set up was 300 front and 750 rear and it feels absolutely balanced. You could very well be correct with 56%, I can't know that for sure without calculating. However, the current setup I have feels great and that's all I know for certain.
05-12-2012, 03:15 PM
#17
Rennlist Junkie Forever
That formula... using the .63 squared would be the formula if you have calculated the displacement ratio on the control arm.
The displacement ratio is the difference between how far the wheel moves, and how far the spring actually compresses.
In order to get these values, you need to get a control arm on a car, and at the angle the control arm is when the car is at rest. Then take measurements moving the control arm up 1 " and down 1"... at various points, subtract the differences, then average them out, and square the number to get the actual wheel rate percentage.
A .63 displacement ratio... just guessing here based on previous work on other cars, would at first glance appear to have the shock further inboard from the axle than it visually appears to be.
I'll put this on my to-do list this week and report back.
TonyG
The displacement ratio is the difference between how far the wheel moves, and how far the spring actually compresses.
In order to get these values, you need to get a control arm on a car, and at the angle the control arm is when the car is at rest. Then take measurements moving the control arm up 1 " and down 1"... at various points, subtract the differences, then average them out, and square the number to get the actual wheel rate percentage.
A .63 displacement ratio... just guessing here based on previous work on other cars, would at first glance appear to have the shock further inboard from the axle than it visually appears to be.
I'll put this on my to-do list this week and report back.
TonyG
Well, not correct is harsh. I can agree there may be different opinions on the subject. There are two different ways to figure spring rate, calculating and actually testing. And if you're calculating there are a lot of things to consider. I personally have not made any calculations on a car so my opinion is somewhat limited and I go by what other people have actually measured and how cars I set up feel. First off, ignore my .63^2 because that can get confusing and I just happen to remember it that way. .63^2 is roughly .40. So 40% of the spring rate is the effective wheel. On the old paragon tech, what most people used to go off of was .63. Well that site is quite old at this point and since there has been a few changes of opinion. From people who have actually calculated, they've figured from .4 to .45. At least from what I've seen. Apparently if you read the following thread, someone mentioned Porsche Motorsport tested it to be .42. I'm not sure how valid that is but it falls in line with everything else.
When I set up my first 944 forever ago, I used the old Paragon .63 and the rear was FAR too soft. The effective was most definitely not what I calculated.
Tony, which value do you use and what are your spring rates on your race car?
Dillon, this thread has everything you'll need:
https://rennlist.com/forums/944-turb...-enclosed.html
I would just suggest you don't go over 300 in front if you're driving it on the street. That's plenty stiff and the car will handle very well without knocking your teeth out. Tony has a good suggestion there.
When I set up my first 944 forever ago, I used the old Paragon .63 and the rear was FAR too soft. The effective was most definitely not what I calculated.
Tony, which value do you use and what are your spring rates on your race car?
Dillon, this thread has everything you'll need:
https://rennlist.com/forums/944-turb...-enclosed.html
I would just suggest you don't go over 300 in front if you're driving it on the street. That's plenty stiff and the car will handle very well without knocking your teeth out. Tony has a good suggestion there.
05-12-2012, 03:44 PM
#19
Rennlist Junkie Forever
Where did you get 56% from, Tony? I'm curious. The last car I set up was 300 front and 750 rear and it feels absolutely balanced. You could very well be correct with 56%, I can't know that for sure without calculating. However, the current setup I have feels great and that's all I know for certain.
Like I said above... I should really just take the measurements and get a real value.
TonyG
05-12-2012, 06:16 PM
#21
Rocket Scientist
Rennlist Member
Rennlist Member
Yeah, you bring up a very important point. We can discuss spring rate all day but one must realize they need a damper that is valved correctly for their spring rate. I mentioned this for you, Dillon.
05-12-2012, 07:19 PM
#23
Burning Brakes
I believe those shocks are meant to be used with the torsion bars in place and a lighter 200lb spring. Only solid bushing shock eyes are meant for use with out the TBs.
05-12-2012, 07:43 PM
#24
Rocket Scientist
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Rennlist Member
I don't think that's necessarily true, Jason. I think it may be more ideal to have spherical mounts, however, I've ran a setup like that pictured. I had it re-valved by TrueChoice for the correct spring rate and never had any problems.
05-12-2012, 08:09 PM
#26
Rocket Scientist
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Rennlist Member
I can't say for certain on that one. All I know is I left it up to the experts at TrueChoice to valve it correctly for my 550 lbs springs (no T bars). This was awhile ago, though. You're correct in that they were originally meant for helper type springs so most definitely they're going to need a re-valve for anything substantial. I don't know exactly where, though.
05-12-2012, 10:31 PM
#27
Burning Brakes
Chill brother. I'd be more inclined to followvette951s advice being that he has hands on experience with his Turbo Cup car.
Would you care to share your sources so we all have difinative figures? Also N/mm would be the correct abreviation for metric spring rates.
Because that's the way Porsche sent out their Turbo Cup Cars, right?
This kit could be an option, but Dillon is working with, most likely, original Bilstein bits and ideally would require re-valving for those springs.
Though your information may be completely correct it is also your opinion as to what you’d prefer. My post suggesting solid shock eyes without torsion bars would be more ideal for track work though not required for DD duty.
Take a deep breath man, I don’t believe we’re too far off.
Here's the valving that I collected from various sources. It's in Nm and R is for rebound and C is for compression.
944 HD INSERT FRONT - PN: 34-001042 - 1480R/1125C (NM)
944 HD 36MM SHOCK REAR - PN: 24-020527 - 2350R/1190C
944 TURBO CUP FRONT - 3800R/1500C
944 TURBO CUP REAR - 5650R/2180C
944 FIREHAWK FRONT - 6000R/1800C
944 FIREHAWK REAR - 4000R/2000C
944 HD INSERT FRONT - PN: 34-001042 - 1480R/1125C (NM)
944 HD 36MM SHOCK REAR - PN: 24-020527 - 2350R/1190C
944 TURBO CUP FRONT - 3800R/1500C
944 TURBO CUP REAR - 5650R/2180C
944 FIREHAWK FRONT - 6000R/1800C
944 FIREHAWK REAR - 4000R/2000C
Though your information may be completely correct it is also your opinion as to what you’d prefer. My post suggesting solid shock eyes without torsion bars would be more ideal for track work though not required for DD duty.
Take a deep breath man, I don’t believe we’re too far off.
05-12-2012, 11:02 PM
#28
Race Car
Thread Starter
hmm, I wonder if the rear springs would fit on the front with the coilovers I can buy off of paragon with new koni inserts. Then, I could upgrade the rear ones. Are the hypercoil springs all the same length, just different spring rates?
This tread is teaching me a lot. Keep up the good work rennlist!
This tread is teaching me a lot. Keep up the good work rennlist!
05-13-2012, 02:27 AM
#30
Rocket Scientist
Rennlist Member
Rennlist Member
Look, I think Jason is just trying to get you to take it easy a bit. You're being pretty harsh. I realize you're sure of yourself and that's fine. However, we're all here to learn a bit from each other. I'm a mechanical engineer and I still learn plenty every day about things I covered in school, I by no means know it all nor do I pretend to or slam people if they don't know. There's just no reason for it.
Back to the subject at hand. Dillon, if I were you, I would just choose a spring rate for the front and rear and try the struts the way they are. If you're not going out on the track much you can see how they feel. The way they are may not be the most ideal situation, and if they're under-valved they'll bounce more, but running them the way they are won't ruin anything. You're probably on a bit of a budget so that should be fine for now. That way you can see if you like the spring rates you chose.
Back to the subject at hand. Dillon, if I were you, I would just choose a spring rate for the front and rear and try the struts the way they are. If you're not going out on the track much you can see how they feel. The way they are may not be the most ideal situation, and if they're under-valved they'll bounce more, but running them the way they are won't ruin anything. You're probably on a bit of a budget so that should be fine for now. That way you can see if you like the spring rates you chose.