Reducing inside-wheel spin
03-29-2005, 11:25 AM
#1
Thread Starter
Reducing inside-wheel spin
I'm posting this here because because it's the relevant audience.
I discovered that with the rear suspension, movement upward or downward of the A-arms is resisted by the rubber bushing in the A-arms (though I tested only the upper arm). The rubber bushing is fused (non-movable) inside the A-arm, and the brackets clamp the bushing in a fixed position when you torque down the bolts that hold the A-arm to the frame. So when you torque the bolts with the suspension loaded as per the Helms manual, the bushings are locked with the A-arm in an "up" position, so when the suspension is unloaded as for the inside wheel during cornering, or when the car is jacked up, droop is resisted by the rubber bushing. (If you were to remove the shock and the swaybar, you would see that the A-arm doesn't move freely, and any induced movement result in "twisting" of the rubber bushing.) Therefore, it seems that this resistance to droop by the bushing contributes to inside wheel lift in cornering once the wheel is past the point of where the spring is fully uncompressed (the spring will easily overcome the resistance of the bushing until the spring is unloaded).
So, one possible solution I am wondering about would be to torque the bolts when the A-arms is is a full droop position (beyond where the spring is fully extended; I guess this is feasible only with set-up's like the JRZ's with 8" springs). This way, the resistance from the bushing would be against compression, which should not be a problem from a performance perspective as it would add only a few pounds/in of compression at most, so negligible. On the other hand, the wheel would have a tendency to return to it's full droop position when unloaded, so this should help reduce inside wheel spin.
Does this make sense and should I try it? One concern might be that the bushing might deteriorate more quickly since it would be in a "twist" position when the car is on the ground (i.e. essentially all the time).
Am I insane?
Of course, the better solution would be to replace the rubber bushings with ones that actually rotate inside the sleeve.
I discovered that with the rear suspension, movement upward or downward of the A-arms is resisted by the rubber bushing in the A-arms (though I tested only the upper arm). The rubber bushing is fused (non-movable) inside the A-arm, and the brackets clamp the bushing in a fixed position when you torque down the bolts that hold the A-arm to the frame. So when you torque the bolts with the suspension loaded as per the Helms manual, the bushings are locked with the A-arm in an "up" position, so when the suspension is unloaded as for the inside wheel during cornering, or when the car is jacked up, droop is resisted by the rubber bushing. (If you were to remove the shock and the swaybar, you would see that the A-arm doesn't move freely, and any induced movement result in "twisting" of the rubber bushing.) Therefore, it seems that this resistance to droop by the bushing contributes to inside wheel lift in cornering once the wheel is past the point of where the spring is fully uncompressed (the spring will easily overcome the resistance of the bushing until the spring is unloaded).
So, one possible solution I am wondering about would be to torque the bolts when the A-arms is is a full droop position (beyond where the spring is fully extended; I guess this is feasible only with set-up's like the JRZ's with 8" springs). This way, the resistance from the bushing would be against compression, which should not be a problem from a performance perspective as it would add only a few pounds/in of compression at most, so negligible. On the other hand, the wheel would have a tendency to return to it's full droop position when unloaded, so this should help reduce inside wheel spin.
Does this make sense and should I try it? One concern might be that the bushing might deteriorate more quickly since it would be in a "twist" position when the car is on the ground (i.e. essentially all the time).
Am I insane?
Of course, the better solution would be to replace the rubber bushings with ones that actually rotate inside the sleeve.
03-29-2005, 11:51 AM
#2
I don't think the spring like qualities of that bushing have a measurable effect on the lifting of the inside wheel. I think it's the sway bar that's getting the best of you there.
Have you disconected the swaybar and raised the car with the wheel still attached? I'm bettng the weight of the wheel alone is enough to over come any preload the bushing is applying.
If the suspension drops with the sway bar disconnected and the wheel bolted up, you'll know that altering the bushing is useless. Test it out.
Have you disconected the swaybar and raised the car with the wheel still attached? I'm bettng the weight of the wheel alone is enough to over come any preload the bushing is applying.
If the suspension drops with the sway bar disconnected and the wheel bolted up, you'll know that altering the bushing is useless. Test it out.
03-29-2005, 12:09 PM
#4
Thread Starter
Yes it seems the swaybar would need to be disconnected if it is going to make any difference.
Ry, it would only matter that extra droop after the spring is fully extended.
On further thought I agree the bushing effect is negligible. Never mind .
(Now you guys with disconnected swaybars don't go running out and re-setting your bushings!
)
Ry, it would only matter that extra droop after the spring is fully extended.
On further thought I agree the bushing effect is negligible. Never mind
. (Now you guys with disconnected swaybars don't go running out and re-setting your bushings!
)
03-29-2005, 12:26 PM
#6
Thread Starter
Originally Posted by krazik,Mar 29 2005, 01:22 PM
huh?
But it's a moot point as the bushing resistance is negligible in the big picture.
03-29-2005, 01:07 PM
#7
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Too much suspension movement with too much mechanical grip. Use stiffer springs and you'll keep more weight on the back inside of the car.
Even with my 225/245 setup, I found I had a hard time keeping the back inside planted through buttonhook going CW. You have more grip than me, slightly less spring, and you don't have a kaaz to slow the wheelspin of an unloaded wheel, so I imagine it's even worse with yours. I could probably go 50-75 lb/in higher at each corner than my current 700/750 rates to cure the problem with my tires. You could probably go up another 100 lbs over that since you have more grip. The car will be more skittish and your drives to/from the track will be even worse than they already are, but you'll keep the wheels all firmly planted on the ground, even with the swaybar.
Ry and I have disagreed on this for a while. His way works, but I still think this is the better way. Karner looks like he's doing what I'm saying here (much more spring). His car was comparable to Rylan's for laptimes, kept all wheels down, and didn't slosh around on transitions (and with lesser shocks than our JRZs).
Even with my 225/245 setup, I found I had a hard time keeping the back inside planted through buttonhook going CW. You have more grip than me, slightly less spring, and you don't have a kaaz to slow the wheelspin of an unloaded wheel, so I imagine it's even worse with yours. I could probably go 50-75 lb/in higher at each corner than my current 700/750 rates to cure the problem with my tires. You could probably go up another 100 lbs over that since you have more grip. The car will be more skittish and your drives to/from the track will be even worse than they already are, but you'll keep the wheels all firmly planted on the ground, even with the swaybar.
Ry and I have disagreed on this for a while. His way works, but I still think this is the better way. Karner looks like he's doing what I'm saying here (much more spring). His car was comparable to Rylan's for laptimes, kept all wheels down, and didn't slosh around on transitions (and with lesser shocks than our JRZs).
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03-29-2005, 02:26 PM
#8
Thread Starter
So Rev, I'm expecting a lot of inside wheel spin on just about every right-hander at Sears this weekend as I can't disconnect the swaybar with my points total, and I don't know if it's worth the effort to put back the OEM intake to get back points.
I'm out of cheating bastard ideas. If you have any, please PM them to me.
I'm out of cheating bastard ideas. If you have any, please PM them to me.
03-29-2005, 04:46 PM
#10
Thread Starter
Originally Posted by krazik,Mar 29 2005, 05:09 PM
give up and run unlimited 
I'll be on RA1s
I'll be on RA1s