XLR rear end hops over bumps

[enviroserve1]

New to this forum. I'm learning so pls forgive the neophyte in me. My '05 XLR hops over bumps here in NY (where we hope to some day have roads as good as the Oregon Trail in 1835). Sometimes at highway speeds, even on a straight, when encountering a moderate bump, the rear end will hop to the right. In a moderate left turn especially, again at highway speeds, the hop is more of a jump. It feels like the rear end jumps two or three inches (that's only a guess based on how it feels). I replaced all 4 mag shocks with OEM mags. Tires are Goodyear Eagle RSAs (P235/50ZR18) (not run flats) at 34 PSI with about 27k on them. I've read that a lot of folks have added the rear sway bar to improve handling but it isn't clear (from the threads I've read) exactly what improvement in handling occurs with that mod. Is spring tensioning a possible factor here? Call me confused.

 

[long Tall Sally]

sway bar only keeps the car flat in turns . Does not sound like your problem. I would say a shock is locked up. You may have a loose or bad control arm bushing or a bad ball joint. Lots of things . did it do the same thing before the shocks were replaced? how long have they been on the car? I would jack it up and look for any movement in the wheel assy. Up or down in and out use a bar to make sure none of the bushings are bad. how long since an alignment? if the rear is out of align you could be getting push out of one side. Look to see that the wheels are all sitting the same in the wheel well openings. So do you feel this "jump" in the seat of your pants? only when you hit a bump?

 

[IAN]

Suspension problems

hi enviroserve

Your car is 15 years old and it perhaps needs a close suspension check up, have a Cadillac dealer who has the expertise on Mag Shocks, the suspension sensers that contribute to send the signal to the shocks could be defectives.

The suspension bushings and the front sway bar bushings has to be check also, while doing this verification have the dealer to check the front and rear spring. ( and why not the ball joints )

The wheel alignments could needs an a justement, the wear of the tires could tell.

A rear sway bar is for the driver that like to push its XLR to the limlts, if you are that type of driver why not to get sway bars.

Welcome to this site.....no, you are not a neophyte.

IAN

 

[long Tall Sally]

the rear sway bar was left off due to weight. It has nothing to do with pushing the car to the limit. I have lots of 60-80 year old owners who really like the solid feel the sway bar gives the car. You will not feel the car sway when you change lanes. when you enter an interstate cloverleaf the car remains flat. its a great improvement in ride and control for anyone . When the shocks were new and all the suspension was 100% new the computer was supposed to offset the need for sway bar. It did not work. one of the few cars built period that does not come with one. Ian likes to send everyone to the steelership where they look it over and just throw parts at it at about 150$ an hour. on the other hand a quality alignment shop knows suspension as that is what they do and will be cheaper and do a better job in 90% of the cases.

 

[IAN]

well well well

Sally.

When your type of driving is regular, the need of a rear way bars is not a need....changing frequently the road lanes too quick, it could be a need in order to keep the wheel on the road, it is a must for that type of driving.

The V is a very powerfull engine then the base XLR model and in order to keep the car on the road the rear sway bar was intalled on this perticular model, other wise the car would be unsafe to drive.

You have your opinion and I have mine, I recall on the last debate with Billstein on the differences for the B6/B8, my last post on the '' got rid of my Mag shock '' I have made, it is showing on these Billstein documents that it is exactely what I was saying since the beganning of this debate.

Keep your hand on the wheel man, your arguments were out of the road.

End of the story.

IAN

 

[redvett94]

Has the differential oil been changed? If the oil and the additive isn't changed the positraction clutches will grab going around a corner and do what your describing.

 

[enviroserve1]

Thanks for the reply. Only about 500 miles since shocks replaced. It behaved this way before replacing them. I've not aligned rear although there isn't any odd wear on the rear tires. I doubt it was aligned before I bought it (2nd owner). Car has 58k miles on it now. I can feel the steering wheel torque to the right as well. Yesterday, I let more air out of the tires (to 32 PSY), which had a minor improving effect. Alignment seems reasonable, as does an entire suspension check up.

 

[enviroserve1]

Yeah, I did the rear diffential lube thing two years ago. Big difference, particularly when backing. Pretty sure that isn't the problem. Thanks for the idea though.

 

[long Tall Sally]

Ian when you cut and paste information learn to read when its something you know nothing about .You are wrong about the shocks and continue to be wrong. Please apologize to the community for all the wasted time on the subject and incorrect information you have posted.
here is a direct email from Bilstein on the subject that shows you are incorrect. Now end of story as you like to say . shocks are same length and do not lower the car. I just installed a set of b8 and they give the car an excellent ride just as it was when new. Customer is totally happy said he had forgotten how well the car handled when new as the ride had just gotten bad over a period of time.
[FONT=&quot]Hello Michael,[/FONT]
[FONT=&quot] [/FONT]
[FONT=&quot]As stated the B6 and B8 shocks for your Corvette/ XLR are the same lengths front and rear. I have provided the extended and collapsed dimensions below for these shocks that you can share . The difference between them is in the valving. I cannot share the valving info as it is proprietary. The Corvette/XLR uses a unique front and rear transverse leaf spring suspension which is different from the European cars that have strut style suspensions and need the longer B6(for stock springs) and shorter B8 (for lowering springs) shocks.[/FONT]
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[FONT=&quot]Mit freundlichen Grüßen / Best regards[/FONT]
[FONT=&quot] [/FONT]
[FONT=&quot]John Trexler[/FONT]
[FONT=&quot]Technical Sales and Warranty Support Expert[/FONT]
[FONT=&quot]thyssenkrupp Bilstein of America, Inc[/FONT]

 

[IAN]

B6 and B8 are not of the same length

The strut suspension is not only for the european market, that suspension concept is for the US cars makers also.

The front and rear shocks of the c6/XLR are of the same lenght that is correct, however the front and rear B8 shorters shocks, are also of the same shorter lenghts shocks for the front and rear.

The cars with the coil srings type would need some shorters springs in order to be adapted on the vehicule with the B8 shorter shocks.

The c6/XLR transversal springs are made with an adjustment bolt contrary with the cars coil springs type, that is correct and the c6/XLR have the advantage to fit the B8 shorter shocks without changing the springs, if desired,

Hans a person from the bilstein of your, area has explain it on the Thread '' got rid of my mag shocks'' and its affirmation is the same as the bilstein graphic from UK send to you lately and i have resend it to you, again, and under lined the differences on the B6/B8 for your comprehension.

IAN

 

[enviroserve1]

I appreciate the comments guys but never intended to incite a riot. I will look into rear alignment first. After 58k miles on NY roads, it can't be a bad idea in any event. While they're doing that, I'll get a read on obvious suspension specs on the rear end anyway, which will point me in a direction. I have a decent alignment shop nearby, but I'll quiz them first to make sure I'm comfortable with their skills. Thanks to Sally and Ian for the thoughts. I'll report back after some investigation.

 

[Z1.]

This is NOT my area of expertise, but I went with wider back wheels ( staggered: I think they are 315s now) and I get less wheel hop and waddle (side to side movement) on the road.

 

[IAN]

Debating yes, confrontation no thanks.

enviroserve1

Sorry for somes above posts..... they should have been debated in an other thread.

Welcome in the debate section of this site, were all members can say their experience/opinion about a perticular problem.

This way we all benefit and learn and inform the members for an now/eventual problem of their XLR.

IAN

 

[xlrlist01]

Thanks for the reply. Only about 500 miles since shocks replaced. It behaved this way before replacing them. I've not aligned rear although there isn't any odd wear on the rear tires. I doubt it was aligned before I bought it (2nd owner). Car has 58k miles on it now. I can feel the steering wheel torque to the right as well. Yesterday, I let more air out of the tires (to 32 PSY), which had a minor improving effect. Alignment seems reasonable, as does an entire suspension check up.

What tires do you have? Isn't 30 psi the correct pressure? I find that too high on my X and run 28 (I'm not on run-flats). Run-flats had a higher pressures (stiffer sidewalls). I have checked the pressures with a contact-less thermometer. The temperature should be the same across the width of the tire. If the edges are the same and the middle higher, the pressure is too high, the alignment (camber) is good. If the edges are different, the middle should be set to the average and the camber checked. The tire runs hotter on the part carrying the heavier load.

 

[enviroserve1]

What tires do you have? Isn't 30 psi the correct pressure? I find that too high on my X and run 28 (I'm not on run-flats). Run-flats had a higher pressures (stiffer sidewalls). I have checked the pressures with a contact-less thermometer. The temperature should be the same across the width of the tire. If the edges are the same and the middle higher, the pressure is too high, the alignment (camber) is good. If the edges are different, the middle should be set to the average and the camber checked. The tire runs hotter on the part carrying the heavier load.

In my first post on this subject, I mentioned the tires are Goodyear Eagle RSAs (P235/50ZR18) (not run flats) at 34 PSI with about 27k on them. I really appreciate the thinking on the infrared temp test on the tires as a way of determining camber and inflation. I never heard of that before but it makes a ton of sense, so thanks for that. Since I first posted, I brought pressure down to about 31 psi and the difference is definitely perceptible. After I take a look at the tread temp, I'll have a better basis for determining whether an alignment is the way to go. By the way, there's no unusual wear on the rear tires (although I rotate every oil change or about every 8 - 9k miles with synthetic).

 

[IAN]

Tires pressure.

Hi enviro....

Too much air pressure do not make the proper ride that an XLR should give, too less air pressure could give a softer ride however the handling of the car could be not as per the OEM requirements.(30 psi )

Changing the wheels for larger and the appropiate tires, the total OEM outside diameter of the Wheel/tire must be respected, otherwise your acceleration could be dimunish or too quick with the incorrect reading of your cluster.

A fine tire shop could help you with your choice and the required air pressure is need for the new wheels/tires.

YES, the wheels/tires is also a mather of needs and choices.

IAN

 

[IAN]

Tires air pressure

HI enviro....

Too much air pressure do not make the proper ride that an XLR should give, too less air pressure could give a softer ride however the handling of the car could be not as per the OEM requirements.(30 psi )

Changing the wheels for larger and the appropiate tires, the total OEM outside of the Wheel/tire must be respected, otherwise your acceleration could be dimunish or too quick with the incorrect reading of your cluster.

A fine tire shop could help you with your choice and the required air pressure is need for the new wheels/tires.

YES, the wheels/tires is also a mather of needs and choices.

IAN

 

[enviroserve1]

It's been a while since I've been on here. Took the car to a reliable mechanic and had F & R alignment done. Waaay out of spec. Weird how there was so little uneven wear on the tires but up close, we could see a very narrow (1/2") excessive wear on inside edge of all 4 tires. Handling is much better after that. Also running at the recommended tire pressure of 30 PSI. Not getting quite as good gas mileage but small price to pay. Now looking at replacing all 4 tires. Considering summer only tires since the car rarely even sees rain, let alone snow. Suggestions? By the way, thanks to all for the suggestions and thoughts.

 

[mickeytee]

I would be a little concerned first to find out why it was out of alignment. These cars have bushings and ball joints that hold up really well . Ive seen 75,000 -100,000 miles and hardly no play or change in alignment. Just aligning it will of course help but find the reason it was out before you invest a lot in tires.

 

[Z1.]

My '05 XLR hops over bumps here in NY (where we hope to some day have roads as good as the Oregon Trail in 1835).

Democrats and Shitty roads go hand in hand.