951, 944, 968 racers. Question about toe settings??
05-06-2010, 07:53 AM
#61
Race Car
The germans think you shouldn't use the longer pins on the a-arms, he said that the camber changes are minimal due to the angle of the mcpherson and they found the effect of the steering arm joints much bigger. Now, what do I know? I do know they race theirs on the ring and hockenheim a lot. Their spring rate suggestions work very well for me. I'll email you some correspondence for your info.
www.shark-motorsport.de
www.shark-motorsport.de
05-06-2010, 10:17 AM
#62
Drifting
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Camber gain ?? under compression ? engineered for 15" wheel and tire its beneficial to give half of it up when running 18's ...
I have +60mm ball joint's and the bump steer / toe curve looks pretty good without any bump steer kit as yet .. it looks like it will toe in a little under compression as i believe they are supposed to .
but I'm just saying "looks " when i measure it I will perhaps end up with a small steering end spacer..
I have +60mm ball joint's and the bump steer / toe curve looks pretty good without any bump steer kit as yet .. it looks like it will toe in a little under compression as i believe they are supposed to .
but I'm just saying "looks " when i measure it I will perhaps end up with a small steering end spacer..
05-06-2010, 08:48 PM
#63
Rennlist Member
Thread Starter
I've worked with some Germans who didn't know their butt from a hole in the ground. They are correct about needing to address bump steer, but it is mainly introduced when you change the angle of the lower control arm without addressing the steering rack. So you should be changing both the end link and ball joint pin length together. If you lower the car and don't address the angle of the LCA, you'll also bind up the ball joint, and eventually break the control arm. Not addressing it also means you'll be giving up camber gain. Not to mention that you are moving your roll center further away from your CG.
with but I'm probably going to try these pins anyway. Can't hurt.
05-06-2010, 11:03 PM
#65
Race Car
Sent you a PM about the German engineers. As well as someone you know who can corraborate what I said. The only reason I mentioned it was the post that seemed to imply that that automatically made it good/right/whatever.
05-06-2010, 11:46 PM
#66
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Those plane tickets are looking better all the time, huh Pat? 
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Larry Herman
2016 Ford Transit Connect Titanium LWB
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Larry Herman
2016 Ford Transit Connect Titanium LWB
2018 Tesla Model 3 - Electricity can be fun!
Retired Club Racer & National PCA Instructor
Past Flames:
1994 RS America Club Racer
2004 GT3 Track Car
1984 911 Carrera Club Racer
1974 914/4 2.0 Track Car
CLICK HERE to see some of my ancient racing videos.
05-07-2010, 12:44 AM
#67
Sent you a PM about the German engineers. As well as someone you know who can corraborate what I said. The only reason I mentioned it was the post that seemed to imply that that automatically made it good/right/whatever.[/QUOTE]
Just to clarify, I didn't try to imply that. I don't know enough about it. All I know is that it works for me and my car which is using the A-arms (re)build by them, their rear axle and their suggested spring rates and suspension set up and shortly their dry-sump system ;-)
So I just gave my suggestion based on what I've experienced so far. No trying to offend or be a smart ***.
H
Just to clarify, I didn't try to imply that. I don't know enough about it. All I know is that it works for me and my car which is using the A-arms (re)build by them, their rear axle and their suggested spring rates and suspension set up and shortly their dry-sump system ;-)
So I just gave my suggestion based on what I've experienced so far. No trying to offend or be a smart ***.
H
Last edited by HJK; 05-07-2010 at 01:04 AM.
05-07-2010, 01:40 AM
#68
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I just did some measurements on my set up and ran them post my german ring rat guru.
at some stage i herd a "little bit of bump steer is ok" so as it was in the right direction i thought it would be ok any how i have since learnt that a little bit is 1 or 2 mm toe change per inch of travel not 1 or 2 degree . so the set up on mine gains a drastic 32mm of toe over 3" of travel ...using +65 ball joint pins (similar to Pat)
So I concur the arm and steering rod parallel is how it should basically be .. so I'll get started on some adjustable bump steer kits now ...
at some stage i herd a "little bit of bump steer is ok" so as it was in the right direction i thought it would be ok any how i have since learnt that a little bit is 1 or 2 mm toe change per inch of travel not 1 or 2 degree . so the set up on mine gains a drastic 32mm of toe over 3" of travel ...using +65 ball joint pins (similar to Pat)
So I concur the arm and steering rod parallel is how it should basically be .. so I'll get started on some adjustable bump steer kits now ...
05-07-2010, 02:21 AM
#69
Race Car
Sent you a PM about the German engineers. As well as someone you know who can corraborate what I said. The only reason I mentioned it was the post that seemed to imply that that automatically made it good/right/whatever.
Just to clarify, I didn't try to imply that. I don't know enough about it. All I know is that it works for me and my car which is using the A-arms (re)build by them, their rear axle and their suggested spring rates and suspension set up and shortly their dry-sump system ;-)
So I just gave my suggestion based on what I've experienced so far. No trying to offend or be a smart ***.
H
Just to clarify, I didn't try to imply that. I don't know enough about it. All I know is that it works for me and my car which is using the A-arms (re)build by them, their rear axle and their suggested spring rates and suspension set up and shortly their dry-sump system ;-)
So I just gave my suggestion based on what I've experienced so far. No trying to offend or be a smart ***.
H
Also, I finally found a picture that should pretty easily show what a BAD situation looks like. Old car. I lowered it, and relocated the inner mount point for the LCA. You can clearly see that it points down from teh crossmember to the ball joint at a pretty significant angle. The end link, however, is almost flat. I never drove the car like this (long story), but it was bad before I relocated the inner mount point, which only made it worse. Here is a situation where I was going to have to do something.
05-07-2010, 05:50 AM
#70
Rennlist Member
Thread Starter
If only to chair the UN meeting we may need soon. 
67king, thanks for that picture to illustrate the point. I need to go and check out a car on the hoist tomorrow to see what this is all about.
Just as an aside, what does the group think would be a good alternative if one were to replace our older designed suspension system (both front and rear) for something more contemporary? This is not for the car I'm dealing with now, but another project that may happen. The car can't be tubbed and tubed but imagine what else you could replace our old trailing arm Mac strut stuff with if you were doing a similar project and that was the objective.
Bring it...
67king, thanks for that picture to illustrate the point. I need to go and check out a car on the hoist tomorrow to see what this is all about.
Just as an aside, what does the group think would be a good alternative if one were to replace our older designed suspension system (both front and rear) for something more contemporary? This is not for the car I'm dealing with now, but another project that may happen. The car can't be tubbed and tubed but imagine what else you could replace our old trailing arm Mac strut stuff with if you were doing a similar project and that was the objective.
Bring it...
05-07-2010, 06:04 AM
#71
Rennlist Member
Thread Starter
I just did some measurements on my set up and ran them post my german ring rat guru.
at some stage i herd a "little bit of bump steer is ok" so as it was in the right direction i thought it would be ok any how i have since learnt that a little bit is 1 or 2 mm toe change per inch of travel not 1 or 2 degree . so the set up on mine gains a drastic 32mm of toe over 3" of travel ...using +65 ball joint pins (similar to Pat)
So I concur the arm and steering rod parallel is how it should basically be .. so I'll get started on some adjustable bump steer kits now ...
at some stage i herd a "little bit of bump steer is ok" so as it was in the right direction i thought it would be ok any how i have since learnt that a little bit is 1 or 2 mm toe change per inch of travel not 1 or 2 degree . so the set up on mine gains a drastic 32mm of toe over 3" of travel ...using +65 ball joint pins (similar to Pat)
So I concur the arm and steering rod parallel is how it should basically be .. so I'll get started on some adjustable bump steer kits now ...
05-07-2010, 06:28 AM
#72
Drifting
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it toes in the angle between the 2 is allot so i could see it coming ... i would suspect yours will be a bit less
as your pins will probably be a little less
if your worried about the pins i can turn up some shorter ones for you or ones that are fatter in the middle like i have ..
as your pins will probably be a little less
if your worried about the pins i can turn up some shorter ones for you or ones that are fatter in the middle like i have ..
05-07-2010, 11:05 AM
#73
Rennlist Member
Patrick,
Maybe you already got it, but some of the posts here seem confusing to me.
Presumably you already have pins on the arms from racers edge. They are a good quality 19mm pin and come in different lengths which you specify when you buy them so no idea what you have in terms of length. The pins are there to restore the roll centre geometry and stop binding. If you lower the car too far without restoring the angle of the arms you push the roll centre down. That increases the distance between your CoG and rollcentre and increases the roll couple. If you don't stiffen the suspension, you will get more body roll on a lowered car. How long your pins need to be depends on how far you lower the car. Conventional wisdom is to keep the arms approx parrallel to the ground.
Once you have lowered the car and used arm pins to restore the arm angle, you have now increased the difference in angle between the tie rod and the arm which, as has been said, is what causes bump steer. The solution is to move the tie rod arm down also to reduce the angular difference between the tie rod and the arm. Ideally you want to get them parrallel which is why the length of the tie rod pin depends on where your arm is.
Getting this right really does make a big difference on track and IMO it's worth the work to get rid of as much bump steer as you can. Small improvements are quite noticeable. I used the Elephant Racing spacers originally, which is just one way of doing it, and the reduction in toe change was very good. But I still got closer to 0 toe change through the range with additional washers above the tie rod end. My tie rods and arms are pretty much dead parrallel now, and it feels much better.
BTW I did mean stiffen the front and/or soften the rear. With a square tire setup you have much larger amounts of relative front grip than the usual staggered tire arrangement gives. With staggered tires my rear sping rate was always higher than the front, 700F/900R as an example. With equal tires I find the balance is better with stiffer fronts relative to the rear. I currently use 1000F/900R, but am testing 1200F/1000R. You can correct incorrect relative spring rates to some extent with bars, but, with Tarrets at least, I bet you will end up with full stiff front bar and full soft rear with no adjustment left with your current rates.
A quick way to see the effect of any tire stagger/spring combo is to disconnet both bars and drive the car. If the relative rates front to rear are right, the car should still be reasonably neutral. I adjust spring rates to get the steer characteristics close to where I want them, ideally ending up with my bars in the middle of their range which then allows them to be used for fine adjustment to suit particular tracks and setup changes. With Tarrets that's why I end up running stiffer springs than some. Some prefer softer springs and bigger bars.
Maybe you already got it, but some of the posts here seem confusing to me.
Presumably you already have pins on the arms from racers edge. They are a good quality 19mm pin and come in different lengths which you specify when you buy them so no idea what you have in terms of length. The pins are there to restore the roll centre geometry and stop binding. If you lower the car too far without restoring the angle of the arms you push the roll centre down. That increases the distance between your CoG and rollcentre and increases the roll couple. If you don't stiffen the suspension, you will get more body roll on a lowered car. How long your pins need to be depends on how far you lower the car. Conventional wisdom is to keep the arms approx parrallel to the ground.
Once you have lowered the car and used arm pins to restore the arm angle, you have now increased the difference in angle between the tie rod and the arm which, as has been said, is what causes bump steer. The solution is to move the tie rod arm down also to reduce the angular difference between the tie rod and the arm. Ideally you want to get them parrallel which is why the length of the tie rod pin depends on where your arm is.
Getting this right really does make a big difference on track and IMO it's worth the work to get rid of as much bump steer as you can. Small improvements are quite noticeable. I used the Elephant Racing spacers originally, which is just one way of doing it, and the reduction in toe change was very good. But I still got closer to 0 toe change through the range with additional washers above the tie rod end. My tie rods and arms are pretty much dead parrallel now, and it feels much better.
BTW I did mean stiffen the front and/or soften the rear. With a square tire setup you have much larger amounts of relative front grip than the usual staggered tire arrangement gives. With staggered tires my rear sping rate was always higher than the front, 700F/900R as an example. With equal tires I find the balance is better with stiffer fronts relative to the rear. I currently use 1000F/900R, but am testing 1200F/1000R. You can correct incorrect relative spring rates to some extent with bars, but, with Tarrets at least, I bet you will end up with full stiff front bar and full soft rear with no adjustment left with your current rates.
A quick way to see the effect of any tire stagger/spring combo is to disconnet both bars and drive the car. If the relative rates front to rear are right, the car should still be reasonably neutral. I adjust spring rates to get the steer characteristics close to where I want them, ideally ending up with my bars in the middle of their range which then allows them to be used for fine adjustment to suit particular tracks and setup changes. With Tarrets that's why I end up running stiffer springs than some. Some prefer softer springs and bigger bars.
Last edited by Dubai944; 05-07-2010 at 11:43 AM.
05-07-2010, 01:42 PM
#74
Race Car
Patrick,
Maybe you already got it, but some of the posts here seem confusing to me.
Presumably you already have pins on the arms from racers edge. They are a good quality 19mm pin and come in different lengths which you specify when you buy them so no idea what you have in terms of length. The pins are there to restore the roll centre geometry and stop binding. If you lower the car too far without restoring the angle of the arms you push the roll centre down. That increases the distance between your CoG and rollcentre and increases the roll couple. If you don't stiffen the suspension, you will get more body roll on a lowered car. How long your pins need to be depends on how far you lower the car. Conventional wisdom is to keep the arms approx parrallel to the ground.
Once you have lowered the car and used arm pins to restore the arm angle, you have now increased the difference in angle between the tie rod and the arm which, as has been said, is what causes bump steer. The solution is to move the tie rod arm down also to reduce the angular difference between the tie rod and the arm. Ideally you want to get them parrallel which is why the length of the tie rod pin depends on where your arm is.
Getting this right really does make a big difference on track and IMO it's worth the work to get rid of as much bump steer as you can. Small improvements are quite noticeable. I used the Elephant Racing spacers originally, which is just one way of doing it, and the reduction in toe change was very good. But I still got closer to 0 toe change through the range with additional washers above the tie rod end. My tie rods and arms are pretty much dead parrallel now, and it feels much better.
BTW I did mean stiffen the front and/or soften the rear. With a square tire setup you have much larger amounts of relative front grip than the usual staggered tire arrangement gives. With staggered tires my rear sping rate was always higher than the front, 700F/900R as an example. With equal tires I find the balance is better with stiffer fronts relative to the rear. I currently use 1000F/900R, but am testing 1200F/1000R. You can correct incorrect relative spring rates to some extent with bars, but, with Tarrets at least, I bet you will end up with full stiff front bar and full soft rear with no adjustment left with your current rates.
A quick way to see the effect of any tire stagger/spring combo is to disconnet both bars and drive the car. If the relative rates front to rear are right, the car should still be reasonably neutral. I adjust spring rates to get the steer characteristics close to where I want them, ideally ending up with my bars in the middle of their range which then allows them to be used for fine adjustment to suit particular tracks and setup changes. With Tarrets that's why I end up running stiffer springs than some. Some prefer softer springs and bigger bars.
Maybe you already got it, but some of the posts here seem confusing to me.
Presumably you already have pins on the arms from racers edge. They are a good quality 19mm pin and come in different lengths which you specify when you buy them so no idea what you have in terms of length. The pins are there to restore the roll centre geometry and stop binding. If you lower the car too far without restoring the angle of the arms you push the roll centre down. That increases the distance between your CoG and rollcentre and increases the roll couple. If you don't stiffen the suspension, you will get more body roll on a lowered car. How long your pins need to be depends on how far you lower the car. Conventional wisdom is to keep the arms approx parrallel to the ground.
Once you have lowered the car and used arm pins to restore the arm angle, you have now increased the difference in angle between the tie rod and the arm which, as has been said, is what causes bump steer. The solution is to move the tie rod arm down also to reduce the angular difference between the tie rod and the arm. Ideally you want to get them parrallel which is why the length of the tie rod pin depends on where your arm is.
Getting this right really does make a big difference on track and IMO it's worth the work to get rid of as much bump steer as you can. Small improvements are quite noticeable. I used the Elephant Racing spacers originally, which is just one way of doing it, and the reduction in toe change was very good. But I still got closer to 0 toe change through the range with additional washers above the tie rod end. My tie rods and arms are pretty much dead parrallel now, and it feels much better.
BTW I did mean stiffen the front and/or soften the rear. With a square tire setup you have much larger amounts of relative front grip than the usual staggered tire arrangement gives. With staggered tires my rear sping rate was always higher than the front, 700F/900R as an example. With equal tires I find the balance is better with stiffer fronts relative to the rear. I currently use 1000F/900R, but am testing 1200F/1000R. You can correct incorrect relative spring rates to some extent with bars, but, with Tarrets at least, I bet you will end up with full stiff front bar and full soft rear with no adjustment left with your current rates.
A quick way to see the effect of any tire stagger/spring combo is to disconnet both bars and drive the car. If the relative rates front to rear are right, the car should still be reasonably neutral. I adjust spring rates to get the steer characteristics close to where I want them, ideally ending up with my bars in the middle of their range which then allows them to be used for fine adjustment to suit particular tracks and setup changes. With Tarrets that's why I end up running stiffer springs than some. Some prefer softer springs and bigger bars.
05-07-2010, 03:15 PM
#75
Rennlist Member
Agreed. I used Motons also which can cope with the heavier spring rates than some shocks. So many factors affect what is the best actual spring rate for a given setup.
What I am emphasising is to get the front to rear spring rate ratio correct, rather than commenting on how stiff the setup should be. Patrick could go stiffer overall or softer overall, but I am suggesting changing the stiffness bias toward the front.
What I am emphasising is to get the front to rear spring rate ratio correct, rather than commenting on how stiff the setup should be. Patrick could go stiffer overall or softer overall, but I am suggesting changing the stiffness bias toward the front.