Lowered my car and got Nittos, now I have a thump on take off.
08-19-2004, 12:25 PM
#1
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Lowered my car and got Nittos, now I have a thump on take off. I lowered my car with BMR springs and I have HAL 12 ways on the front and stock shocks on the back. I just got Nitto DR's and when I take off at anything over half throttle I hear a thump from the rear of the car. I also noticed that my header is hitting the k-member now. It wasn't hitting before. I replaced my trans mount and drivers side motor mount with poly mounts about 6 months ago. I know that I probably need LCA relocation brackets. If I get LCA brackets will that help my problem? If not what is the problem?
08-19-2004, 03:13 PM
#2
Thump sound from rear Most likely your are hitting your bumpstocks because you lowered your car. You can check by jacking up the car from the center of the rear and take off one of the wheels. Then take a look at how close you are to the bumpstops.
Solution: Either cut the bumpstop or remove it all together. Just make sure you still have enough free play before either bottoming the rear on the frame or coil binding the springs.
As for the reloc. brackets they are more for traction than anything. If you still need a set I have a new pair for a Moser 12 Bolt.
Happy motoring,
Kevin
Solution: Either cut the bumpstop or remove it all together. Just make sure you still have enough free play before either bottoming the rear on the frame or coil binding the springs.
As for the reloc. brackets they are more for traction than anything. If you still need a set I have a new pair for a Moser 12 Bolt.
Happy motoring,
Kevin
08-19-2004, 04:36 PM
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I would strongly advise against removing the bump stop - it's there for a reason! There are two possible causes for your problem - bottoming out on the bump stop or wheel hop.
Let's start with bottoming out. Check the rear axle tubes for signs of contact with the bump stops. You will be able to see rust on the bump stop and/or a smooth spot in the rust on the axle tube. Since your car is an SS, you have aluminum spacers between the bump stops and the body. Remove the spacers and reinstall the rubber bump stops. If you're still bottoming out, which I doubt will happen, you can trim the bump stop slightly.
The other probable cause is wheel hop. Lowering the car alters the suspension geometry. After lowering my own car, the wheel hop sounded like one loud bang on hard launch. Install relocation brackets to restore proper geometry.
Let's start with bottoming out. Check the rear axle tubes for signs of contact with the bump stops. You will be able to see rust on the bump stop and/or a smooth spot in the rust on the axle tube. Since your car is an SS, you have aluminum spacers between the bump stops and the body. Remove the spacers and reinstall the rubber bump stops. If you're still bottoming out, which I doubt will happen, you can trim the bump stop slightly.
The other probable cause is wheel hop. Lowering the car alters the suspension geometry. After lowering my own car, the wheel hop sounded like one loud bang on hard launch. Install relocation brackets to restore proper geometry.
08-19-2004, 05:43 PM
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Also possible that the exhaust and axle are
interfering, or driveshaft/I-pipe, etc.; get it
up on ramps, fill the trunk with concrete or
dead bodies
and look for any close passes.
Nittos should make for more extreme axle and
suspension torque reactions. More body rise or
more body squat, depending on the rear link
geometry. Squat is where you get interference
between the rear and all the close-packed
stuff around it (and bump stops too). Maybe
have someone with a clue watch your car on
launch, or you watch someone else launch it.
If you see it squat then get a set of relocation
brackets. They gain you traction by reducing
or overcoming the axle-lift, body-squat-causing
geometry error from lowering. You should just
put them on anyway, but you can check the
interference first for possible free fixes (like
loosen, shim, jack & retighten exhaust).
interfering, or driveshaft/I-pipe, etc.; get it
up on ramps, fill the trunk with concrete or
dead bodies
and look for any close passes. Nittos should make for more extreme axle and
suspension torque reactions. More body rise or
more body squat, depending on the rear link
geometry. Squat is where you get interference
between the rear and all the close-packed
stuff around it (and bump stops too). Maybe
have someone with a clue watch your car on
launch, or you watch someone else launch it.
If you see it squat then get a set of relocation
brackets. They gain you traction by reducing
or overcoming the axle-lift, body-squat-causing
geometry error from lowering. You should just
put them on anyway, but you can check the
interference first for possible free fixes (like
loosen, shim, jack & retighten exhaust).
08-19-2004, 07:28 PM
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Cool. Thanks for the suggestions guys. I am going to check the bump stops. I think that is the likely cause. If not then I will get LCA relocation brackets.
