Handling balance
06-16-2017, 06:46 AM
#11
I don't really agree with the LSD advice. Going from a helical diff to an aftermarket clutch diff will definitely give the car a more oversteer/high rear slip angle corner exit behavior. It's very consistent on the clutch type diff because it locks up based on torque input. The factory helical biases based on torque available at the rear wheels, so you've got to make sure you're not running into travel issues back there (I doubt it based on OP's setup).
I've gone between a factory S15 diff (basically same design as S2000 diff, same vintage, and probably same supplier) and a Cusco RS, and the RS is was definitely much more oversteer prone at pretty much any setting of lockup and preload.
I would say more toe-in would help the rear, as OP is running half OEM spec. If you want to run that little toe-in, you might need to tweak your toe arm spacers to get less bumpsteer in roll and squat, and actually measure it.
I would also ditch the urethane bushings - too much friction in the joints, which will make the car less compliant on the tiniest of bumps. They're probably one of the worst things you can do to suspension bushings IMO. They feel fine right after you install them, but a short while later the friction is through the roof.
I've gone between a factory S15 diff (basically same design as S2000 diff, same vintage, and probably same supplier) and a Cusco RS, and the RS is was definitely much more oversteer prone at pretty much any setting of lockup and preload.
I would say more toe-in would help the rear, as OP is running half OEM spec. If you want to run that little toe-in, you might need to tweak your toe arm spacers to get less bumpsteer in roll and squat, and actually measure it.
I would also ditch the urethane bushings - too much friction in the joints, which will make the car less compliant on the tiniest of bumps. They're probably one of the worst things you can do to suspension bushings IMO. They feel fine right after you install them, but a short while later the friction is through the roof.
Tyre temps may help diagnose the issue better
06-16-2017, 08:09 AM
#12
I don't really agree with the LSD advice. Going from a helical diff to an aftermarket clutch diff will definitely give the car a more oversteer/high rear slip angle corner exit behavior. It's very consistent on the clutch type diff because it locks up based on torque input. The factory helical biases based on torque available at the rear wheels, so you've got to make sure you're not running into travel issues back there (I doubt it based on OP's setup).
I've gone between a factory S15 diff (basically same design as S2000 diff, same vintage, and probably same supplier) and a Cusco RS, and the RS is was definitely much more oversteer prone at pretty much any setting of lockup and preload.
I would say more toe-in would help the rear, as OP is running half OEM spec. If you want to run that little toe-in, you might need to tweak your toe arm spacers to get less bumpsteer in roll and squat, and actually measure it.
I would also ditch the urethane bushings - too much friction in the joints, which will make the car less compliant on the tiniest of bumps. They're probably one of the worst things you can do to suspension bushings IMO. They feel fine right after you install them, but a short while later the friction is through the roof.
I've gone between a factory S15 diff (basically same design as S2000 diff, same vintage, and probably same supplier) and a Cusco RS, and the RS is was definitely much more oversteer prone at pretty much any setting of lockup and preload.
I would say more toe-in would help the rear, as OP is running half OEM spec. If you want to run that little toe-in, you might need to tweak your toe arm spacers to get less bumpsteer in roll and squat, and actually measure it.
I would also ditch the urethane bushings - too much friction in the joints, which will make the car less compliant on the tiniest of bumps. They're probably one of the worst things you can do to suspension bushings IMO. They feel fine right after you install them, but a short while later the friction is through the roof.
06-16-2017, 09:35 AM
#13
Registered User
my s2000 was oversteering and very twitchy. after some mods, my s2000 understeers and is very balanced and predictable. it is a completely different car. below are the mods in the order of importance.
1. ran LESS rear toe. don't remember the number, but i deliberately dialed out the rear toe.
2. upgraded to ap2 wheels vs ap1.
3. swift front sway bar (rear is oem)
4. CR rear wing
it looks like you have a lot of grip up front, you could try running wider wheels/tires at the back. you could try upgrading your front sway bar. you could try a rear wing depending on the speeds that you're experiencing unwanted behavior. you could also adjust the shocks, less stiff in the rear. also, lower the tire pressure in the rear depending on your readings.
good luck.
1. ran LESS rear toe. don't remember the number, but i deliberately dialed out the rear toe.
2. upgraded to ap2 wheels vs ap1.
3. swift front sway bar (rear is oem)
4. CR rear wing
it looks like you have a lot of grip up front, you could try running wider wheels/tires at the back. you could try upgrading your front sway bar. you could try a rear wing depending on the speeds that you're experiencing unwanted behavior. you could also adjust the shocks, less stiff in the rear. also, lower the tire pressure in the rear depending on your readings.
good luck.
06-22-2017, 04:33 AM
#14
Thanks all for sharing your experience. Most along the lines I was thinking. I ran 30lbs hot tyre pressure front and rear, which I arrived at after a couple of sessions. I run a moderate ride height, very slight rake to front. I don't believe I was running out of travel.
I have a tyre pyro pyro and will use it next time out to look at my camber settings. I'm also about to fit some tubular upper arms in the rear so I can adjust camber quickly. I also agree that checking rear bump steer with my current setup (eye balled) is a good idea.
I'll play with shock adjustment next time out.
I suspect a bigger aftermarket front bar and/or stiffer front springs are probably the components that will help my issue should I need to spend money to do it :-)
I'll try report back after next track day..
Cheers,
Earlysport
I have a tyre pyro pyro and will use it next time out to look at my camber settings. I'm also about to fit some tubular upper arms in the rear so I can adjust camber quickly. I also agree that checking rear bump steer with my current setup (eye balled) is a good idea.
I'll play with shock adjustment next time out.
I suspect a bigger aftermarket front bar and/or stiffer front springs are probably the components that will help my issue should I need to spend money to do it :-)
I'll try report back after next track day..
Cheers,
Earlysport
06-25-2017, 11:16 AM
#15
Could you be bottoming? TW of 60, lowered, with 10k springs and OEM bars sounds like a fair amount of grip on a relatively soft chassis.
What condition are the shocks in? The RA's are not a current Tein shock and one or more of the shocks may just be worn.
Have you checked bump steer? Again more of an issue on a softer car with its greater suspension movement and possibly changed from a shifted or slightly bent component. Roger Cadell of Aim has a story where he diagnosed a handling problem as related to bump steer and fixed it by making the car stiffer.
What condition are the shocks in? The RA's are not a current Tein shock and one or more of the shocks may just be worn.
Have you checked bump steer? Again more of an issue on a softer car with its greater suspension movement and possibly changed from a shifted or slightly bent component. Roger Cadell of Aim has a story where he diagnosed a handling problem as related to bump steer and fixed it by making the car stiffer.
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