After bolting on some 245/45R17 rubber my 86 T-Type bump steers and follows the road ruts BAD. All the bushings are pretty new and the alignment is set to factory-type specs with 2.5-3 degress caster. Tracking is OK on flat roads but not great. This thing is so flighty around town I'm afraid to let the wife drive it. Is there anything I can do to fix this?
Big Tire Bump Steer
- Thread starter blacksix
- Start date
bmackinnon
Active Member
- Joined
- Feb 24, 2005
What's the camber set at? Tires have no effect on bump steer... which is change in toe vs. suspension travel... you probably have too much neg. camber...
novaderrik
Well-Known Member
- Joined
- May 12, 2004
i think more caster solves this problem.
mr go fast
Member
- Joined
- Aug 8, 2007
Did a chain store align the car? Did they check the steering? Is there any slack you feel in the steering wheel?
A wider tire will track the road better but will also grab the groves in the road more. Caster set higher will eliminate some of it but the problem will persist with a wider tire. You need a good alignment tech that knows what he's doing to be able to help you.
my car is similar, and it got worse with new tires (went from cheapo to good)
I'm running 16" GTA's with 245/50-16 on the front.
I went to the alignment shop with the results of my searching on here.
"Lots of caster, please." They had to send a kid out for more shims....
It seems with the extra caster, that the cross-caster (difference in caster from one side to the other) is making the car drift too much. I believe the cross caster is intended to make the car run straight on crowned roads. With lots of total caster, the cross caster works too well and the car never goes straight.
I want to get back into an alignment shop and play with reducing or eliminating the cross caster and play with toe settings. There should be a way to get the car to drive neutrally....
Some groove following is ok, but the current condition of the car is annoying....
Bob
(any alignment techs on here?)
I'm running 16" GTA's with 245/50-16 on the front.
I went to the alignment shop with the results of my searching on here.
"Lots of caster, please." They had to send a kid out for more shims....
It seems with the extra caster, that the cross-caster (difference in caster from one side to the other) is making the car drift too much. I believe the cross caster is intended to make the car run straight on crowned roads. With lots of total caster, the cross caster works too well and the car never goes straight.
I want to get back into an alignment shop and play with reducing or eliminating the cross caster and play with toe settings. There should be a way to get the car to drive neutrally....
Some groove following is ok, but the current condition of the car is annoying....
Bob
(any alignment techs on here?)
regal81455
Member
- Joined
- Oct 20, 2008
thats strange when I put on my 17's ( same size as above ) my steering was TONS better than it was stock - night and day difference in handling for me and that was with OLD components - can't wait to get this on the road with the new SPC uppers and tubular lowers + new BJ's!! wish I could be more help but something isn't making sense to me...
bmackinnon
Active Member
- Joined
- Feb 24, 2005
I used to be an alignment tech way back when I was in engineering school... I would want at least 5, preferably 6-7 deg POS caster both sides, and you want about 1/4-1/2 deg NEGATIVE camber both sides, with about 1/8 deg (if that, just a tad) less neg on the left to keep it going straight on crowned roads when you let go of the wheel... set the toe at 1/16" in both sides for a total of 1/8" IN.... that should put it as good as it's gonna' get.... and make the tires wear good 
Bob, it's the cross CAMBER that makes it go straight on roads leaning right... the caster is more a dynamic setting that affects the self centering/return to center, while the camber is static with respect to pull on a perfectly smooth road with no steering input...
Bob, it's the cross CAMBER that makes it go straight on roads leaning right... the caster is more a dynamic setting that affects the self centering/return to center, while the camber is static with respect to pull on a perfectly smooth road with no steering input...
This should help you to understand it a little better.
http://www.turbobuick.com/forums/threads/g-body-drag-car-alignment-settings.290592
http://www.turbobuick.com/forums/threads/g-body-drag-car-alignment-settings.290592
Silver Fox
Well-Known Member
- Joined
- Apr 17, 2003
Blacksix,
I fought this problem for years and ended up with the front suspension in my signature trying to eliminate the issue. Even after everything I did to it the front end, it still "tramlined" like you are talking about.
Not until I put new tires on the front of the car did the problem go away. I replaced my directional Yokohama A520's with assymetrical Vredestein Sessentas and the problem was solved.
Company website: Vredestein
Available from: Group A Wheels (Toyo Tires Kumho Sumitomo Vredestein ROH Wheels Porsche BMW Mustang GTO NSX - GroupA Wheels) and Performance Plus Tire (Custom Tires, Custom Wheels, and Parts and Accessories for your Antique, Hot Rod, and Muscle Car from Performance Plus Tire).
They have a very interesting tread pattern, and are an asymmetrical tread design so you can rotate the tires side to side.
With the Vredestein Sessentas it drives nice and straight even when the road is grooved pretty bad. The ride of my car also improved significantly with these tires.
If you haven't heard of Vredesteins, they are a Dutch tire company. They are a highly rated tire company in Europe.
So, what kind of tire did you put on the front? As cruzn57 noted above, some tires are worse than others. That might be a bigger issue than you realize. If you post the type/model of tire, perhaps someone can let you know their experience with the same tire.
Rob
Bigger tires shouldn't effect 'bump steer'. You say your car follows ruts in the road, that is also NOT caused by bump steer but is caused by having wide tires. You really notice this on a motorcycle with a wide rear tire (choppers, or so I've been told).
Bump steer only happens when the front springs are loaded (compressed) such as under braking.
If it's that bad than the allignment shop hasn't done their job properly. They should have set the caster, camber, and tow to spec and it shouldn't pull either way while suspension is loaded or unloaded.
Bump steer only happens when the front springs are loaded (compressed) such as under braking.
If it's that bad than the allignment shop hasn't done their job properly. They should have set the caster, camber, and tow to spec and it shouldn't pull either way while suspension is loaded or unloaded.
Silver Fox
Well-Known Member
- Joined
- Apr 17, 2003
