Re: Spring & Dampers
Posted: Sun Dec 18, 2011 6:08 am
The problem with the Westfield's bushes is that they literally shear... Tear apart, leaving no rubber at all.
They are not really designed to be tightened. They do a good job of isolating vibration, but are not very good if the center element is required to turn. There is simply not enough rubber, only about 3/32". It destroys itself in a very short period of time.
Since I do use my car on long tours, and drive to and from the track for testing and timing sessions, I have found that putting the car on the ground, ballasting it and then tightening up the bushings as recommended, just results in a destroyed suspension in a very short period of time, and very dodgy handling.
One day, I just loosen everything up, and the difference was incredible. The chassis floated over bumps, and grip was much more predictable. The additional advantage is that the rear bushings started to last much longer. I can now get about 2000 miles out of a set of rears before the rubber is simply extruded from the shell.
The problem is that the thin rubber bushing, when mounted in the rear suspension, gets pulled and twisted during normal driving (part of the normal operation of the bind inducing 4 link setup). Body roll, acceleration and braking all conspire to rip the bushing apart. It can't really survive more than a few hundred miles before failure. It's worse in the early cars without the shear plates to support the rear suspension arm bolts at the chassis end. These plates can be added, by the way. Anyway, not requiring the center sleeve to rotate within the rubber greatly increases the life of the rubber element, as it is no longer being ground away between the rotating center element and the outer shell. If the rubber shears, it's no longer a bushing. It's a bolt, rattling around inside the old bushing shell.
Why I am presented with the argument about rotating elements and shear in the bushing as being good things is beyond me at this point. Lots of owners have tried rose joints in the suspensions, no rubber at all! I did that, but found that the usual binding of the 4 link was hard on the affordable rose joints. The good ones cost nearly $900 for the 10 necessary to equip the rear suspension, and I can buy a lot of rubber bushings for that. What would be problem be with allowing the bushing to rotate? Well, nothing, other than better handling, and increased bushing life. The bushing acts as a vibration damper, which is fine. It allows for some compliance in the bind prone 4 link, which is a very good thing, indeed. The bushing can rotate about the suspension bolt without damaging anything. Just make sure that the bolts are properly greased when installing the bushings. The reality is that even the best chassis only gives about 2000 miles from the rear suspension bushings. At that time, at least one pair will need replacing. One on an upper rear suspension arm, and the diagonally opposite lower arm. Shortly after that, you will replace another pair...
If you have 9000 miles on your bushings, I am sure that they are gone. Remove the suspension arms, and the rubber will fall out. If you put the car in gear, remove the rear body, and rock the chassis against the engine's compression (roll the tire, do not set the hand brake), you will see the rear axle rotate, and hear the clunk of the suspension arms. This is especially evident with the early chassis. The late chassis can hide the failure, as the rubber is trapped behind the shear plate. You have to check for loose bushings by rocking the chassis front to back.
I have had this argument with many before about the Westfield's little suspension bushings. What I know, is that they fail quickly if tightened. A failed bushing that is tight doesn't control the rear suspension at all, and it clunks and bangs around. Don't tighten them, let them rotate in the chassis, and they will last much longer, and properly locate the rear suspension arms. The reduction of static friction in the chassis will make it track and handle better in all conditions. Try it. I have put 10s of 1000s of miles on mine without problems, but with much longer bushing life, and far better handling and ride. The little Westfield bushing is not like others, as it has so little rubber. Even the factory has reduced it's torque specification for the bushing to 24 lb.ft.
The main thing to think about is bolt retention. Use new Nylocks, or castle nuts with cotter pins.
The front end bushings last longer as they are not twisted during suspension motion. However, the benefits of reduced friction (looser setup) are undeniable, and the bushings will last longer there as well. You will be surprised as to how well the W11 rides when the bushings are not clamped down.
About the anti roll bar. The chassis has lots of roll, you just are not aware as your eyes are about 28" above the road. Turn a corner, and hit the throttle. You get wheel spin, as that inside wheel has followed the body and is not really in good contact with the road. The ARB will help here, but not much. Stuck with the high roll center, your best bet is an LSD, specifically a clutch type, though a Quaife type may work. The clutch type always works.
Dampers are important as the ones supplied with the cars are so poor in quality and damping ability. The late chassis don't even have the right size dampers installed, and may have rear springs that are too stiff.
Get rid of the 2.25 dampers and springs in the front! The original design called for 1.75" dampers and 1.9" springs. This will give you an inch more front end travel (you can start with dampers half an inch longer, at least, as the hats wont be fouling the upper arms at droop. The new cars use the thicker dampers as they are available in about the right length (nearly an inch short!), and, most importantly, the right price. If you do go to another brand of damper, go with the thinner body, and teh same spring, but in 1.9" diameter. If you have an early car, you already have the small diameter dampers up front. Just keep that setup when you change them out.
In the rear, you can use anything you want. I have large diameter dampers back there, as that is what was sent by mistake.
I promise to post the proper damper lengths tomorrow.
Damper settings are to complement the driver, but there is no reason to have a damper stiffer than is necessary to control the springs/chassis. The idea is to produce grip and predictability. When doing race car or hot road car setup, we look for damper control. Sometimes, that's stiff, other times, the chassis comes out riding quite well.
One modern car that best exemplifies this is the Noble M400/Rossion Q1. Tenacious grip (over 1.1G), but the ride is actually quite compliant.
One of the most interesting things in automotive chassis development over the last decade is the improvement in dampers. It doesn't have to be stiff, and can be quite a bit faster, and easier to drive if the chassis is properly damped. Sometimes, it is not really that stiff.
One thing that I have seen, universally, with W11s here in the US is that none are at the correct ride height. They are all too low. And none have the proper toe setting in the front. Alignment shops don't do chassis setup, and can't set toe on a 1000 lb car without the driver installed.
They are not really designed to be tightened. They do a good job of isolating vibration, but are not very good if the center element is required to turn. There is simply not enough rubber, only about 3/32". It destroys itself in a very short period of time.
Since I do use my car on long tours, and drive to and from the track for testing and timing sessions, I have found that putting the car on the ground, ballasting it and then tightening up the bushings as recommended, just results in a destroyed suspension in a very short period of time, and very dodgy handling.
One day, I just loosen everything up, and the difference was incredible. The chassis floated over bumps, and grip was much more predictable. The additional advantage is that the rear bushings started to last much longer. I can now get about 2000 miles out of a set of rears before the rubber is simply extruded from the shell.
The problem is that the thin rubber bushing, when mounted in the rear suspension, gets pulled and twisted during normal driving (part of the normal operation of the bind inducing 4 link setup). Body roll, acceleration and braking all conspire to rip the bushing apart. It can't really survive more than a few hundred miles before failure. It's worse in the early cars without the shear plates to support the rear suspension arm bolts at the chassis end. These plates can be added, by the way. Anyway, not requiring the center sleeve to rotate within the rubber greatly increases the life of the rubber element, as it is no longer being ground away between the rotating center element and the outer shell. If the rubber shears, it's no longer a bushing. It's a bolt, rattling around inside the old bushing shell.
Why I am presented with the argument about rotating elements and shear in the bushing as being good things is beyond me at this point. Lots of owners have tried rose joints in the suspensions, no rubber at all! I did that, but found that the usual binding of the 4 link was hard on the affordable rose joints. The good ones cost nearly $900 for the 10 necessary to equip the rear suspension, and I can buy a lot of rubber bushings for that. What would be problem be with allowing the bushing to rotate? Well, nothing, other than better handling, and increased bushing life. The bushing acts as a vibration damper, which is fine. It allows for some compliance in the bind prone 4 link, which is a very good thing, indeed. The bushing can rotate about the suspension bolt without damaging anything. Just make sure that the bolts are properly greased when installing the bushings. The reality is that even the best chassis only gives about 2000 miles from the rear suspension bushings. At that time, at least one pair will need replacing. One on an upper rear suspension arm, and the diagonally opposite lower arm. Shortly after that, you will replace another pair...
If you have 9000 miles on your bushings, I am sure that they are gone. Remove the suspension arms, and the rubber will fall out. If you put the car in gear, remove the rear body, and rock the chassis against the engine's compression (roll the tire, do not set the hand brake), you will see the rear axle rotate, and hear the clunk of the suspension arms. This is especially evident with the early chassis. The late chassis can hide the failure, as the rubber is trapped behind the shear plate. You have to check for loose bushings by rocking the chassis front to back.
I have had this argument with many before about the Westfield's little suspension bushings. What I know, is that they fail quickly if tightened. A failed bushing that is tight doesn't control the rear suspension at all, and it clunks and bangs around. Don't tighten them, let them rotate in the chassis, and they will last much longer, and properly locate the rear suspension arms. The reduction of static friction in the chassis will make it track and handle better in all conditions. Try it. I have put 10s of 1000s of miles on mine without problems, but with much longer bushing life, and far better handling and ride. The little Westfield bushing is not like others, as it has so little rubber. Even the factory has reduced it's torque specification for the bushing to 24 lb.ft.
The main thing to think about is bolt retention. Use new Nylocks, or castle nuts with cotter pins.
The front end bushings last longer as they are not twisted during suspension motion. However, the benefits of reduced friction (looser setup) are undeniable, and the bushings will last longer there as well. You will be surprised as to how well the W11 rides when the bushings are not clamped down.
About the anti roll bar. The chassis has lots of roll, you just are not aware as your eyes are about 28" above the road. Turn a corner, and hit the throttle. You get wheel spin, as that inside wheel has followed the body and is not really in good contact with the road. The ARB will help here, but not much. Stuck with the high roll center, your best bet is an LSD, specifically a clutch type, though a Quaife type may work. The clutch type always works.
Dampers are important as the ones supplied with the cars are so poor in quality and damping ability. The late chassis don't even have the right size dampers installed, and may have rear springs that are too stiff.
Get rid of the 2.25 dampers and springs in the front! The original design called for 1.75" dampers and 1.9" springs. This will give you an inch more front end travel (you can start with dampers half an inch longer, at least, as the hats wont be fouling the upper arms at droop. The new cars use the thicker dampers as they are available in about the right length (nearly an inch short!), and, most importantly, the right price. If you do go to another brand of damper, go with the thinner body, and teh same spring, but in 1.9" diameter. If you have an early car, you already have the small diameter dampers up front. Just keep that setup when you change them out.
In the rear, you can use anything you want. I have large diameter dampers back there, as that is what was sent by mistake.
I promise to post the proper damper lengths tomorrow.
Damper settings are to complement the driver, but there is no reason to have a damper stiffer than is necessary to control the springs/chassis. The idea is to produce grip and predictability. When doing race car or hot road car setup, we look for damper control. Sometimes, that's stiff, other times, the chassis comes out riding quite well.
One modern car that best exemplifies this is the Noble M400/Rossion Q1. Tenacious grip (over 1.1G), but the ride is actually quite compliant.
One of the most interesting things in automotive chassis development over the last decade is the improvement in dampers. It doesn't have to be stiff, and can be quite a bit faster, and easier to drive if the chassis is properly damped. Sometimes, it is not really that stiff.
One thing that I have seen, universally, with W11s here in the US is that none are at the correct ride height. They are all too low. And none have the proper toe setting in the front. Alignment shops don't do chassis setup, and can't set toe on a 1000 lb car without the driver installed.