understeer SOS; HELP!
Thread Starter
Pro
Joined: Dec 2002
Posts: 746
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From: salem or
understeer SOS; HELP!
OK, I've done almost everthing that the forum has suggested in my suspension upgrade of a base model '97 coupe: BUT IT NO LONGER STEERS NEUTRAL. HELP!
2002 Z06 front and rear springs
2002 Z06 front and rear bars
Bilstein sports
Lowered to max allowed by factory adjustments
There are a few things I didn't do as per the forum's suggestions:
I gave up on the poly control are bushings, only installing these on the front.
I am still using Goodyear F1 runflats (stock sizes, but new rubber on the rear, old rubber on the front.)
There are a few things I did wrong:
My alignment spec was set to: The tire store mixed up my toe settings front and rear. These ended up being:
Front: -1.5 degrees camber; 1/8 toe in; caster mid 6's
Rear: -.75 degrees camber; 1/16 toe in
On my own I bumped up the rear tire pressure differential to now: 29lbs cold front; 34 lbs cold rear.
I've got a track day coming up on the 15th and the car will not turn in, it won't take a set and it understeers (pushes) quite noticably on the street tires (I will be switching to 275 and 315 hoosiers for the track).
Does anyone want to trouble shoot this with me? Thanks. sj
2002 Z06 front and rear springs
2002 Z06 front and rear bars
Bilstein sports
Lowered to max allowed by factory adjustments
There are a few things I didn't do as per the forum's suggestions:
I gave up on the poly control are bushings, only installing these on the front.
I am still using Goodyear F1 runflats (stock sizes, but new rubber on the rear, old rubber on the front.)
There are a few things I did wrong:
My alignment spec was set to: The tire store mixed up my toe settings front and rear. These ended up being:
Front: -1.5 degrees camber; 1/8 toe in; caster mid 6's
Rear: -.75 degrees camber; 1/16 toe in
On my own I bumped up the rear tire pressure differential to now: 29lbs cold front; 34 lbs cold rear.
I've got a track day coming up on the 15th and the car will not turn in, it won't take a set and it understeers (pushes) quite noticably on the street tires (I will be switching to 275 and 315 hoosiers for the track).
Does anyone want to trouble shoot this with me? Thanks. sj
Instructor
Joined: Feb 2003
Posts: 102
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Re: understeer SOS; HELP! (speedjohnson)
you said slammed to the max..........raise the rear end back up a 1/4" or so. Not to mention if the rake is increased towards the back you effectively increased the anti dive in the front by the same degree of rake change.......all those things will tighten them up. i hear this all the time from street car stuff, that they lowered it all the way, and of course it won't turn the rear roll center is way to low to have the car roll properly.
Pro
Joined: Jul 2002
Posts: 627
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From: Campbell Ca
Re: understeer SOS; HELP! (speedjohnson)
I put the same bars on but I put on Z51 shocks and notice that I am getting push as well. Is it because we are pushing the car harder into the corners because the car is flatter turning or what. :confused:
Le Mans Master
Joined: Oct 2000
Posts: 6,483
Likes: 713
From: Sausalito CA
Re: understeer SOS; HELP! (speedjohnson)
Hi...you are understeering. So the front of the car hits the wall before the rear. Old rubber up front may not be gripping.
I would suggest going back to the tire pressures assuming the aligment is now correct and everything is torques in the suspension.
Start with Ft30 Re30. Drive and note.
Then Ft30 Re25. Drive and note.
Then Ft25 Re30. Drive and note.
May also be you are running out of suspension travel.
Good hunting.
[Modified by Kenny94945, 8:15 AM 3/9/2003]
I would suggest going back to the tire pressures assuming the aligment is now correct and everything is torques in the suspension.
Start with Ft30 Re30. Drive and note.
Then Ft30 Re25. Drive and note.
Then Ft25 Re30. Drive and note.
May also be you are running out of suspension travel.
Good hunting.
[Modified by Kenny94945, 8:15 AM 3/9/2003]
Thread Starter
Pro
Joined: Dec 2002
Posts: 746
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From: salem or
Re: understeer SOS; HELP! (speedjohnson)
As suggested by 14car, I did raise up the rear approx 1/2 inch and then drove it aroung in circles. I coudn't notice any change at neutral throttle ... it still pushes. However, it does rotate easier now when you let off ... just a bit of trailing throttle oversteer.
My next step will be to widen up the front toe to near zero and see if this encourages front hook up. I suppose if this doesn't help, then I can start taking out rear negative camber.
I wonder if going to a slightly smaller front bar (Z51) would help, or if this would be overdoing it.
More suggestions? thanks! sj
My next step will be to widen up the front toe to near zero and see if this encourages front hook up. I suppose if this doesn't help, then I can start taking out rear negative camber.
I wonder if going to a slightly smaller front bar (Z51) would help, or if this would be overdoing it.
More suggestions? thanks! sj
Thread Starter
Pro
Joined: Dec 2002
Posts: 746
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From: salem or
Re: understeer SOS; HELP! (Kenny94945)
Kenny's got a good point. I would hate to think that this is merely because the rubber up front is from '97 and the rubber in the rear is 2003 vinatge...
What a brain tease... Still, I should be able to get this thing to steer right with bar size, alignment, pressures etc.
What I need is an adjustable link in the rear bar... any vendors out there listening? sj
What a brain tease... Still, I should be able to get this thing to steer right with bar size, alignment, pressures etc.
What I need is an adjustable link in the rear bar... any vendors out there listening? sj
Team Owner
Joined: Oct 2001
Posts: 56,377
Likes: 79
Re: understeer SOS; HELP! (speedjohnson)
There are many guys that race very hard with the same equipment you have. Get the alingment back to stock and get new tires on the front. Also ask John Shiels about this (that is his forum name). He races a coupe.
Racer
Joined: Mar 2002
Posts: 346
Likes: 0
Re: understeer SOS; HELP! (CPT Z06)
I've got an '01 Z06, with suspension upgraded to '02 specs. I'm running Goodyear GSCS DOT tires (very fine, soon to be gone, tread, wear rating of 20, so they're pretty soft). Handling was okay, but I knew it would be better with corner weighting and alignment. Went with negative camber of 1.9 degrees up front, and negative camber of 1.3 degrees rear. Toe at .03 inches left rear, .02 inches right rear. Turn in much improved, slight push on entry, car is close to neutral at set, will oversteer some with trailing throttle. I do trail brake a bit on entry. That's just my experience, and I'm far from an expert, but I thought I'd pass it along fyi. Best of luck.
Tom T. :cheers:
Tom T. :cheers:
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Thread Starter
Pro
Joined: Dec 2002
Posts: 746
Likes: 1
From: salem or
Re: understeer SOS; HELP! (Tom T.)
Tom: Why the assymetric rear toe? Was this done intentionally, if so what is the rational? or was this misstated? What were your front toe numbers so that I can compare front/ rear? Thx for the lesson. sj
Team Owner
Joined: Oct 2001
Posts: 56,377
Likes: 79
Re: understeer SOS; HELP! (speedjohnson)
Title of this is: Different camber settings between front and rear, why???
http://forums.corvetteforum.com/zerothread?id=471185
http://forums.corvetteforum.com/zerothread?id=471185
Le Mans Master
Joined: Feb 1999
Posts: 6,269
Likes: 1
From: Richmond Ca
Re: understeer SOS; HELP! (speedjohnson)
Kenny's got a good point. I would hate to think that this is merely because the rubber up front is from '97 and the rubber in the rear is 2003 vinatge...
What a brain tease... Still, I should be able to get this thing to steer right with bar size, alignment, pressures etc.
What I need is an adjustable link in the rear bar... any vendors out there listening? sj
What a brain tease... Still, I should be able to get this thing to steer right with bar size, alignment, pressures etc.
What I need is an adjustable link in the rear bar... any vendors out there listening? sj
Pro
Joined: Jul 2002
Posts: 627
Likes: 0
From: Campbell Ca
Re: understeer SOS; HELP! (wwashing)
Your front tires are 6 or 7 years old. Time alone increases the hardness of runflat rubber and decreases their traction. Add the wear factor and you probably have a lot less traction in the front than in the rear. :cheers: [/QUOTE
I took the car out on sunday the rubber was wamed up and the car had conciderably less push. I am convinced it is the front tires and not the set-up. :cheers:
[Modified by Racer1x, 1:11 PM 3/11/2003]
I took the car out on sunday the rubber was wamed up and the car had conciderably less push. I am convinced it is the front tires and not the set-up. :cheers:
[Modified by Racer1x, 1:11 PM 3/11/2003]
Pro
Joined: Jul 2002
Posts: 627
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From: Campbell Ca
Re: understeer SOS; HELP! (Scruffy)
Try swapping the front Z06 antiroll bar with a Z51 unit. Too much resistance in the front antiroll bar will increase understeer.
Melting Slicks
Joined: Feb 2000
Posts: 2,375
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From: Pittsburgh, PA
Re: understeer SOS; HELP! (Racer1x)
Try swapping the front Z06 antiroll bar with a Z51 unit. Too much resistance in the front antiroll bar will increase understeer.
Well, then why do the Z06 cars come equiped with one. :confused:
Well, then why do the Z06 cars come equiped with one. :confused:
Team Owner
Joined: Oct 2001
Posts: 56,377
Likes: 79
Re: understeer SOS; HELP! (speedjohnson)
Sruffy:
Thanks for the suggestion. I fixed the problem (that I had created) by evening out the bushing material front to rear. thx. sj
Thanks for the suggestion. I fixed the problem (that I had created) by evening out the bushing material front to rear. thx. sj
