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Suspension Upgrades

MGibson.MSO

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Joined
Nov 8, 2017
Messages
18
Location
Missoula
I’m waffling about potential suspension upgrades on my 2007 base model when I pull it out of storage this spring. I need to make a decision to install sway bars or not. XLR-net has a bunch of helpful posts, and I’ve picked up lots of solid information. Thanks especially to GizmoQ and Cadillac Tech for starting these very helpful threads offering a terrific foundation on the subject:

https://www.xlr-net.com/forums/cadi...or-possible-upgrade.html?highlight=Suspension

https://www.xlr-net.com/forums/cadi...waybar-parts-list-04-09-a.html?highlight=Sway

After looking at those threads and a bunch of others here and on a couple Corvette sites, I still have a few specific questions, and I thought I’d invite my fellow XLR owners to indulge in a deep dive on the subject. In the spirit of curious inquiry, I’ll pose a handful of questions.

1) Will adding sway bars to a base model throw off the ride control software? If the ride control programming in the XLR base model is different than the XLR-V, then I presume the base model’s magnetic ride control would not respond optimally to added sway bars. However, it seems like people add and upgrade sway bars all the time without worrying about the ride control programming. Does it matter?

2) Can you replace leaf spring pads and adjusters without replacing the entire spring? I figure my springs are probably good for a long, long time, but the rubber bits will eventually need to be changed out. I’ve gotten the impression that aftermarket ride height adjusters are easy to find, but pads cannot be replaced on their own. Is that correct?

3) What are the correct clamp and bushing part numbers for front sway bar 25919501 and rear sway bar 20777535? I’m leaning toward getting sway bars that mimic the stock XLR-V setup by purchasing the Corvette C6 Fe2 soft ride versions. Based on extensive internet searches, I believe that the clamps and bushings (a.k.a. insulators) are different front and rear, but it’s not entirely clear which clamp and which bushings go where. I believe the parts list thread that I referenced earlier is not entirely up-to-date, because it references sway bar, clamp and bushing combinations that have been discontinued or replaced by different part numbers. GM parts sites are vague on the subject. I should be able to get something virtually identical to a stock XLR-V setup with Corvette C6 Fe2 parts, but I can’t confidently identify the correct clamps and bushings.

I did find one online parts dealer that offers what’s advertised as stock XLR-V sway bar kits, front and rear including links, all for $400. I suspect those kits rely on new, old stock parts. I think I could get similar parts for less at GM Parts Direct, if only I knew which clamps and bushings to order. It shouldn’t be hard, but it is.

4) My dealer says my shocks appear to be in good shape after 12 years and 55,000 miles. Should I believe it? Replacing all four would cost about $2,000. How do you know when the ride quality has deteriorated?

I’m eager to see the responses to these questions. I know there are several viable approaches to suspension upgrades. With any luck, we’ll drop some new knowledge on the group that will become a useful reference. Thanks, all.




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long Tall Sally

Seasoned Member
Joined
Sep 11, 2018
Messages
891
Location
Aiken SC
My XLR/V(s)
2008 xlr dove gray
yes , no, no, yes, yes, no ,Maybe. But not in that order. HAHAHA
1. don't see how it would change the software as the ride module is the same on 06-09 all v and base. GM said in advertising that the 08 had an improved ride. The shocks show to be the same on the base and v 08-09 and corvettes. However the shock part numbers show to fit all xlr and the delco numbers at some sellers show to be the same. SO most likely the upgraded shocks replace the older ones Ride control works of the lower control arm moving up and down. the more it moves the more it controls the flow of fluid in the shocks. The sway bars will hold the car flatter In a curve so less movement in the control and less dampening needed I nthe shocks

2 Leaf spring pads are made onto the leaf spring and not replaceable yet. They glue on so no one makes one they sell but I see other materials on some of the performance corvettes so I think they are making their own. The adjuster are replaceable with the corvette ones but they sell them to lower the cars . so there is less rubber and you have to screw them out farther to match the proper ride height.

3. The clamps are the same no matter what sway bars you use. The bushings are sized internally to match the bar it is being used on. So that's why I like to find a bar on ebay with the bushings and clamps on them them already. cost 50-75 shipped for a good one with low mileage. The bars come with a part number so write it down and you can get bushings for that bar. You can also match up the size at a source like Moog and they make them for all size bars as some of the GM part numbers on the bushings are NLA. The aftermarket sources will always have them. Side note ( I had a Ferrari Daytona that the sway bar bushings were about 50.00$ each. They were the exact same as a mazda pickup for 3$ each. Get any 17mm bar off of a 06-12 corvette and it will work fine. Links are about 35 each so if you find one with links even better. I think the front bars on all xlr are the same. I will have to check on that one but you don't need a bigger front unless you go with bigger tires, drive aggressive In the turns. Also if you replace the 2000 shocks with standard corvette upgrade with simulators. Drawings of the clamps on the gm parts site do not show what they really look like they show the front and rear look alike but they don't and have different part numbers

4. WOW that one SHOCKS ME. haha get it ?? A dealer saying you don't need something? that's almost scary. Realistically depending on use the shocks should last 100k miles but they leak. as they depend on the fluid to control the ride that is the life of them when enough fluid leaks out. Also they do tend to lock up. when you car starts feeling hard a shock is locked up. I do not think there is any computer that will check the shocks
for performance. I feel the way the fluid is used inside the shocks will cause it to break down over time. Almost all performance shocks have a huge reservoir so they hold extra fluid and also cooling abilities that these do not have. As far as ride I have no idea how to tell. It changes so slight over such a period you would just get used to it. I would hate to spend 2 grand and say ,yep rides the same.

The sway bar upgrade will not be something you can just tell has been done. 90% of your driving will be unaffected by it. But swerve to miss that ball in t he road and you will tell it. Get on or off that banked road entrance and you will tell . It just helps keep the car flat in turns and better control. The shocks are a matter of preference. Its not going to handle like a corvette unless you change all the shocks to corvette parts.
 

MGibson.MSO

Member
Joined
Nov 8, 2017
Messages
18
Location
Missoula
Thanks for the response, LTS. I’m still waffling, but my waffling is better informed. And honestly, it’s kinda fun to overthink it.

yes , no, no, yes, yes, no ,Maybe. But not in that order. HAHAHA
1. don't see how it would change the software as the ride module is the same on 06-09 all v and base. GM said in advertising that the 08 had an improved ride. The shocks show to be the same on the base and v 08-09 and corvettes. However the shock part numbers show to fit all xlr and the delco numbers at some sellers show to be the same. SO most likely the upgraded shocks replace the older ones Ride control works of the lower control arm moving up and down. the more it moves the more it controls the flow of fluid in the shocks. The sway bars will hold the car flatter In a curve so less movement in the control and less dampening needed I nthe shocks

I sort of understand, but I’m not all the way there yet. To get more technical, which is dangerous for me because I don’t know what I’m talking about, I’m questioning whether the car might be underdamped with an added sway bar. I’m thinking the sway bar would effectively add spring, but the ride control programming would anticipate the stock spring rate. With an added or a stiffer sway bar, the programmed damping wouldn’t match up with the additional spring rate the way Cadillac engineers envisioned. Of course, this is all pretty esoteric because I’m apparently the only XLR owner who’s fretting about it.

2 Leaf spring pads are made onto the leaf spring and not replaceable yet. They glue on so no one makes one they sell but I see other materials on some of the performance corvettes so I think they are making their own. The adjuster are replaceable with the corvette ones but they sell them to lower the cars . so there is less rubber and you have to screw them out farther to match the proper ride height.

Got it. If my adjuster pads are shot, I’ll buy aftermarket trim height adjusting bolts. Thanks.

3. The clamps are the same no matter what sway bars you use. The bushings are sized internally to match the bar it is being used on. So that's why I like to find a bar on ebay with the bushings and clamps on them them already. cost 50-75 shipped for a good one with low mileage. The bars come with a part number so write it down and you can get bushings for that bar. You can also match up the size at a source like Moog and they make them for all size bars as some of the GM part numbers on the bushings are NLA. The aftermarket sources will always have them. Side note ( I had a Ferrari Daytona that the sway bar bushings were about 50.00$ each. They were the exact same as a mazda pickup for 3$ each. Get any 17mm bar off of a 06-12 corvette and it will work fine. Links are about 35 each so if you find one with links even better. I think the front bars on all xlr are the same. I will have to check on that one but you don't need a bigger front unless you go with bigger tires, drive aggressive In the turns. Also if you replace the 2000 shocks with standard corvette upgrade with simulators. Drawings of the clamps on the gm parts site do not show what they really look like they show the front and rear look alike but they don't and have different part numbers

Ok. I’ve got the clamp as GM part 25933429, which agrees with the other threads.

4. WOW that one SHOCKS ME. haha get it ?? A dealer saying you don't need something? that's almost scary. Realistically depending on use the shocks should last 100k miles but they leak. as they depend on the fluid to control the ride that is the life of them when enough fluid leaks out. Also they do tend to lock up. when you car starts feeling hard a shock is locked up. I do not think there is any computer that will check the shocks
for performance. I feel the way the fluid is used inside the shocks will cause it to break down over time. Almost all performance shocks have a huge reservoir so they hold extra fluid and also cooling abilities that these do not have. As far as ride I have no idea how to tell. It changes so slight over such a period you would just get used to it. I would hate to spend 2 grand and say ,yep rides the same.

I found another thread with some great information from ccclark. He explains that the shocks can be inspected, the ride height measured and and an electrical test performed to confirm they’re functioning. Of course, now I can’t find the thread again, but when I do, I’ll update my response with the link.

The sway bar upgrade will not be something you can just tell has been done. 90% of your driving will be unaffected by it. But swerve to miss that ball in t he road and you will tell it. Get on or off that banked road entrance and you will tell . It just helps keep the car flat in turns and better control. The shocks are a matter of preference. Its not going to handle like a corvette unless you change all the shocks to corvette parts.
 
Last edited:

Fireduck69

Seasoned Member
Joined
Mar 21, 2015
Messages
309
Location
NorthEast PA
My XLR/V(s)
2007 Black XLR-V
I did find a corvette site that offers original type spring adjusters. Yes there are replaceable as I have replaced 3 of mine for being broken off.
 

long Tall Sally

Seasoned Member
Joined
Sep 11, 2018
Messages
891
Location
Aiken SC
My XLR/V(s)
2008 xlr dove gray
are you sure they are the original type with the big rubber washers? all the ones I have seen or any body else on the Vette forums have a much thinner rubber washer to allow the car to be lowered. Not stock ones. Please get me a part number on that .As far as checking the shocks. Maybe mr clark can advise the dealer as they are unaware of any way to check the operation of the shocks. They can check for a open circuit which indicates they are not working I believe but no way to check if the internals are operating to change the orifice at the proper rate and cycle for fluid travel .If he knows how to do that , he should set up a business as The vette guys also would like to know. I think the shocks like anything get worn over time and loss of fluid results In heat which in turn changes the thickness of the fluid which changes the shock rates. , You cannot check their operation by the old simple bounce test to see if they rebound. Some really good technical articles about the style shock on Gabrials site and Hy-jacker To find out how they work go to The Belstein formula one site and see how the engineers explain it.
 

long Tall Sally

Seasoned Member
Joined
Sep 11, 2018
Messages
891
Location
Aiken SC
My XLR/V(s)
2008 xlr dove gray
Oh and you are really over thinking it. I have restored forumal one cars and helped build GTP cars i nthe day. We would have a whole team just work on suspension spring rates and sway bars. The sway bar on this car will not make any differance in the shock program. If you really want todo time trials and dial it in , buy the adjustable sway bar links and I will tell you how to weight the corners of the car and set up the balance on the car. The ride height is not controlled by the shocks. It is controlled by the springs . A worn out shock will not lower the car any more than a new one will raise it. You can visually check the shocks for oil on the outside but that will not tell you if they have been cleaned before and may have leaked out more than you think. I actually weighed a few to see if it could be determined how much fluid had been lost. The new shocks actually weighed less than the old ones and out of 6 they all weighed different amounts for the same shock, so no precision in the housing design for sure. One thing to look at is the position actuators on the control arms. Make sure they are working and the arms are straight. I have seen bent arms cause all sorts of issues. If you want to firm up your ride or soften it, I can help you there. I have both electrically tricked the sending units to change voltage input tot the suspension computer to stiffen the ride and also mechanically changed the arms on the sensor to duplicate much harsher ride which in turns stiffens the car up. I will be glad to share that info . Several of the corvette guys used my system but now they just got to a conventional shock which they like better. Super great caddy system when new and working perfect which I think is for a very short time. As it gradually fails you dont realize it
 

Fireduck69

Seasoned Member
Joined
Mar 21, 2015
Messages
309
Location
NorthEast PA
My XLR/V(s)
2007 Black XLR-V

long Tall Sally

Seasoned Member
Joined
Sep 11, 2018
Messages
891
Location
Aiken SC
My XLR/V(s)
2008 xlr dove gray
cool .I did not find those before. I will get a couple sets ordered. Thanks The ones I ordered before showed the stock but shipped the lowering ones
 

MGibson.MSO

Member
Joined
Nov 8, 2017
Messages
18
Location
Missoula
are you sure they are the original type with the big rubber washers? all the ones I have seen or any body else on the Vette forums have a much thinner rubber washer to allow the car to be lowered. Not stock ones. Please get me a part number on that .As far as checking the shocks. Maybe mr clark can advise the dealer as they are unaware of any way to check the operation of the shocks. They can check for a open circuit which indicates they are not working I believe but no way to check if the internals are operating to change the orifice at the proper rate and cycle for fluid travel .If he knows how to do that , he should set up a business as The vette guys also would like to know. I think the shocks like anything get worn over time and loss of fluid results In heat which in turn changes the thickness of the fluid which changes the shock rates. , You cannot check their operation by the old simple bounce test to see if they rebound. Some really good technical articles about the style shock on Gabrials site and Hy-jacker To find out how they work go to The Belstein formula one site and see how the engineers explain it.

Yeah, I overstated the reliability of the suggested shock tests. The original source qualified the advice appropriately and noted the procedures were the best you could do to confirm shock functionality. The numerous ways they might fail is only just occurring to me. I wonder how the car’s self diagnostics work to confirm the shocks are functional. You’d think the sensors could detect when the compression and rebound rates are way out of spec, because the ride height would change too rapidly.
 

mickeytee

Seasoned Member
Joined
Apr 5, 2017
Messages
483
Location
North Atlanta
the system is not that smart. It just detects there is resistance t the shocks and "assumes" they are in working order. The system does not know if the shocks are working properly or not.
 

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