Loose rear end when driving at highway speeds
02-19-2014, 05:28 AM
#1
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Loose rear end when driving at highway speeds
I've been trying to pin down a problem for a while now, it just ruins this car for me because I know how stable this car should feel.
When I'm driving on the highway or turning through a bend or corner, the rear end of the car feels all wonky. The best way to describe it when driving down the highway is it feels like wind is pushing the wear end of the car in multiple directions. It isn't dramatic enough to cause loss of grip, but it is not confidence inspiring at all.
Things I have done so far:
-Diff needed replacing 3k miles ago, so that was done.
-Suspension had a horrible clunk, and car felt how it does now. Shock was blown in the rear, so I replaced all 4 corners. Clunk is gone, and the car takes bumps better, but no improvement on 'loose feeling'.
-Tire pressure is OK. I was 1 psi lower on a rear tire but I topped it up at a gas station.
-Alignment performed
None of these things have made the car feel better. The suspension did make the car ride better, but it hasn't helped the wonky feeling. I'm about to replace the brakes, and the driver's front caliper is a little slow to come back after braking, which causes a bit of shaking on the highway for about 15-30 seconds until it comes back in. Think it could be a sticking caliper that causes this, even though the front one is the one sticking?
I haven't checked my mounts yet, but I'm gonna try to get it on a lift soon to take a look. Could bad diff/trans/engine mounts cause the car to feel like this? The car doesn't have a super rough/vibrating idle.
I'm kind of despondent here. I've sunk a good amount of time and money in this car, and it just isn't cooperating. Anyone have any suggestions?
When I'm driving on the highway or turning through a bend or corner, the rear end of the car feels all wonky. The best way to describe it when driving down the highway is it feels like wind is pushing the wear end of the car in multiple directions. It isn't dramatic enough to cause loss of grip, but it is not confidence inspiring at all.
Things I have done so far:
-Diff needed replacing 3k miles ago, so that was done.
-Suspension had a horrible clunk, and car felt how it does now. Shock was blown in the rear, so I replaced all 4 corners. Clunk is gone, and the car takes bumps better, but no improvement on 'loose feeling'.
-Tire pressure is OK. I was 1 psi lower on a rear tire but I topped it up at a gas station.
-Alignment performed
None of these things have made the car feel better. The suspension did make the car ride better, but it hasn't helped the wonky feeling. I'm about to replace the brakes, and the driver's front caliper is a little slow to come back after braking, which causes a bit of shaking on the highway for about 15-30 seconds until it comes back in. Think it could be a sticking caliper that causes this, even though the front one is the one sticking?
I haven't checked my mounts yet, but I'm gonna try to get it on a lift soon to take a look. Could bad diff/trans/engine mounts cause the car to feel like this? The car doesn't have a super rough/vibrating idle.
I'm kind of despondent here. I've sunk a good amount of time and money in this car, and it just isn't cooperating. Anyone have any suggestions?
02-19-2014, 05:54 AM
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02-19-2014, 05:55 AM
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You got an alignment, what were the final measurements? Alignment specs are a *very* broad range. If you have maximum spec AP1 rear toe-in (~0.67 degrees total), it can give the kind of weird rear-end-moving-around-alla-time feel. If that's the case, have them reset rear to to the minimum end of the spec range (0.33 degrees total) or less, even. I run ~0.2 degrees total.
Do you have the alignment sheet?
Do you have the alignment sheet?
02-19-2014, 05:57 AM
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You got an alignment, what were the final measurements? Alignment specs are a *very* broad range. If you have maximum spec AP1 rear toe-in (~0.67 degrees total), it can give the kind of weird rear-end-moving-around-alla-time feel. If that's the case, have them reset rear to to the minimum end of the spec range (0.33 degrees total) or less, even. I run ~0.2 degrees total.
Do you have the alignment sheet?
Do you have the alignment sheet?
02-19-2014, 06:25 AM
#6
"Not out of spec" means anywhere from 0.33 to 0.67 degrees total rear toe on an AP1, and of course all the other measurements have a broad range as well (don't have the spec in front of me, but probably something like +.1 to -.75 front camber, -.5 to -1.5 for rear camber, +.15 to -.15 front toe, etc.).
When you "get an alignment", if the measurements fall into the *very* broad range of factory specs the shop won't even have to put a wrench on the car. You can still have very wonky and asymmetric alignment though! And of course you pay for a "full alignment"!
Better to know exactly what you want going in and ask for the specific alignment you want, if you want to get something for your money. And always ask for a printout of before and after measurements.
I will generally recommend that people get maximum spec negative camber all around, and minimum spec toe. This will give good ultimate lateral grip and good tire life and generally good handling behavior.
If you might track or autoX the car, you could ask that they dial in as much camber as they can get. Even at -2 camber and beyond, tire life isn't tremendously impacted as long as toe is minimized.
When you "get an alignment", if the measurements fall into the *very* broad range of factory specs the shop won't even have to put a wrench on the car. You can still have very wonky and asymmetric alignment though! And of course you pay for a "full alignment"!
Better to know exactly what you want going in and ask for the specific alignment you want, if you want to get something for your money. And always ask for a printout of before and after measurements.
I will generally recommend that people get maximum spec negative camber all around, and minimum spec toe. This will give good ultimate lateral grip and good tire life and generally good handling behavior.
If you might track or autoX the car, you could ask that they dial in as much camber as they can get. Even at -2 camber and beyond, tire life isn't tremendously impacted as long as toe is minimized.
02-19-2014, 06:28 AM
#7
when the car is up in the air there is an eyelet to check if the subframe is aligned properly. our subframe bolts have been known to come loose.
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02-19-2014, 06:28 AM
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"Not out of spec" means anywhere from 0.33 to 0.67 degrees total rear toe on an AP1, and of course all the other measurements have a broad range as well (don't have the spec in front of me, but probably something like +.1 to -.75 front camber, -.5 to -1.5 for rear camber, +.15 to -.15 front toe, etc.).
When you "get an alignment", if the measurements fall into the *very* broad range of factory specs the shop won't even have to put a wrench on the car. You can still have very wonky and asymmetric alignment though! And of course you pay for a "full alignment"!
Better to know exactly what you want going in and ask for the specific alignment you want, if you want to get something for your money. And always ask for a printout of before and after measurements.
I will generally recommend that people get maximum spec negative camber all around, and minimum spec toe. This will give good ultimate lateral grip and good tire life and generally good handling behavior.
If you might track or autoX the car, you could ask that they dial in as much camber as they can get. Even at -2 camber and beyond, tire life isn't tremendously impacted as long as toe is minimized.
When you "get an alignment", if the measurements fall into the *very* broad range of factory specs the shop won't even have to put a wrench on the car. You can still have very wonky and asymmetric alignment though! And of course you pay for a "full alignment"!
Better to know exactly what you want going in and ask for the specific alignment you want, if you want to get something for your money. And always ask for a printout of before and after measurements.
I will generally recommend that people get maximum spec negative camber all around, and minimum spec toe. This will give good ultimate lateral grip and good tire life and generally good handling behavior.
If you might track or autoX the car, you could ask that they dial in as much camber as they can get. Even at -2 camber and beyond, tire life isn't tremendously impacted as long as toe is minimized.
02-19-2014, 07:18 AM
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Originally Posted by Mr. Orange' timestamp='1392821671' post='23023061
[quote name='iamxpL' timestamp='1392820852' post='23023039']
also check the alignment of the rear subframe. also a sticking caliper good be a culprit. so check that as well.
also check the alignment of the rear subframe. also a sticking caliper good be a culprit. so check that as well.
[/quote]
I'll check that out when it is on the lift. Would something like that cause such wonky handling? It honestly feels like the whole rear of the car is shifting around, perhaps its the subframe shifting around? That's scary to think about.
