Jcbarr25

How can I tell if my lowering bolts are damaged/need replacement? I was checking the front suspension today and saw that the driver side rubber part of the lowering bolt had shifted toward the wheel (the bushing is slanted now). It is still attached to the bolt and it is not broken. I was reviewing some used parts for sell and it seems that the lowering bolt bushing will do that over time. I am assuming it is from the friction and movement of the LCA on the rubber part.

So yeah. How can I tell if I need replacement? Should I continue using until I hear metal to metal sound? Until the bushing part totally separates from the bolt? Given that aftermarket bolts are poor quality, i most likely be purchasing either used leaf springs with lowering bolts in good condition or brand new leaf springs.

Part of why I was inspecting my front suspension is because I had brake vibrations under hard braking. Vibrations does not happen all the time and at normal braking. Could this be a cause for my vibration under hard braking?

cgladish

i just replaced all 4 leveling bolts. the fronts iones ( 1 had the pad about half way still mounted, the other one, the pad was completely gone ), were pointed out to me when, i had a new engine installed.
i bought a set of 4, expecting to just replace them all. my local shop felt that, the rear ones were still ok.
he did notice though, that the transaxle mounts needed replacing. it was during this replacement that,
when they dropped the rear suspension, both rear leveling bolts were found to be broken. you could not tell their condition in a static position, since where the bolts were broken where they passed through the leaf spring. based on their condition,
it would appear that they were broken for a while. the condition of all of these ( transaxle mount & leveling bolts ),
had the rear suspension feel, like it had minimal shocks. also felt a little loose in the corners.
this was all dealt with last week and, so far, all feels fine.

d.medic

Can I ask where you ordered them from? I thought you couldn't just order the bolts .

cgladish

[QUOTE=d.medic;1602908251]Can I ask where you ordered them from? I thought you couldn't just order the bolts .
i got these on amazon ( platinum performance parts, eibach pro-kit, lowering hardware kit #38126.510 )
below is the pdf for the instructions. not sure how the compare to the stock units.
they look like exact replacement for the front bolts. the rear ones we took out though, looked like the pad was twice as thick, as the front ones. i still used the new for replacement as, the original ones had the bolt broken on each one.
it's only been since friday but, all seems to be working.


d2686.pdf

PCMusicGuy

The slant they develop is normal. That happens well within the first 20k miles or so. I have a spare set of stockers from some 2008 springs with 25k miles on them and they have the slant. Mine at 75k miles didn't look any different than those.
At 160k miles, however, one of them was completely falling apart. You could certainly tell they were all dried out. I just replaced my springs and lowering bolts as part of an all new suspension refresh so they should be good for a while now.
You can get OEM like bolts from here:
Corvette Central

That said, the vibration under hard braking would not be due to those lowering bolts. I would check the easy stuff first, e.g. tires/wheels balanced properly and rotors not warped and within spec. After that, I would check the hub/bearing assembly and upper/lower ball joints for play. What is the mileage on the car?

Jcbarr25

I have 35K miles. Only 1 lowering bolt has the slant. Maybe they will remain good for a while more like you are saying.

cmonkey713

The OP's original question was "How can I tell if my lowering bolts are damaged or need replacing". It is a rare case where the bolts are damaged except as a result of a crash where the lower suspension is damaged. To my knowledge these bolts do not "wear out" from normal use. You can check them by putting the car on jack stands and compressing the transverse spring with a floor jack enough to look at the bottom contact surface and the outside of the cushion. In most cases you can do a visual on the outside of the rubber cushion to check for damage. I would be surprised if you find any damage. Sure you can replace them without too much trouble if you want to lower the car more than the OEM bolts will allow. There are Youtube videos on how to to it.

cgladish

my front ones appear to have 'aged out'. one had the pad about halfway still attached. the other pad was completely gone.
the rears ones though both had broken studs. as you mentioned above, they may have broke after the transaxle mounts became worn out.

Jcbarr25

I do not want to lower the car any lower than it currently is. i am just more concerned that the rubber bushings are slanting and wearing out. Will I hear like a metal to metal noise once they are totally gone? the rubber condition on mine seem ok a little dried out but i suppose it is corresponding to a 10 year old car.

cgladish

i wouldn't expect to hear any metallic noise. the only items in contact would be the fiberglass spring with the rubber pad or.
metal plate ( if rubber section is gone ). i had no idea of the wear until, i had the engine replace. sure it is worth doing a
visual inspection somewhat regularly. if these parts slowly wear, you may not even notice it happening.

cmonkey713

The rubber bushing will deteriorate over time. Some lubricate the contact point on the lower control arm with a silicone grease. Before lubricating be sure to throughly clean the contact area. Since you cannot get the bolts from GM anymore you are back to the aftermarket for replacement bolts.

Dano523

Life made simple.

OEM ride height adjustments look like the top left one.

The are good for a long time, but you want to change them out about every 8~10 years, depending on the mileage since the rubber on them does mash over time. Also, you can buy the after market OEM versions of the OEM's that will last the same amount of time as well.


Now on the other hand, if you have the lower type ride height adjusters like in the other one in the above photo or below, then bank that they are broken within the first year they were installed.

Hence they do not have enough cushion to them to last more than at year, so either base pad cracks, or the joint between the threaded section and base pad breaks/wears out instead.

As for when the ride height adjusters are replaced or adjusted, car needs to be 4 corner balanced so it handles correctly again.

cgladish

The top one is what was what i had removed from the rear end ( while the pad portion was ok, it was the stud portion that was broken on both). the front levelers are similar to the bottom ones, but in black. currently all for corners are the same ( black version of the white ones shown above ).

Dano523

Again, the after market lowering type ride high adjusters do not have the needed cushioning of the OEM type adjuster, so they last about a year before they have problems.

Here are the OEM type,
https://www.corvettecentral.com/c7-1...fsuspension%2f

And if you want to go a bit lower than stock, find someone with a lathe to chuck the up and remove the bottom rib section. It's going to shorten the life of them by a few years due to the reduced cushioning, but is going to hold up longer than the rest of the lowering type after market units that only last a year instead.

And again, when installing new or adjusting the ride high adjusters, you need to corner balance the car to get the weight distribution correct for all four corners.
If you just slam the car all the way down on any adjusters, car is going to be way out of corner balance, and going to effect the handling of the car greatly.

Also, keep in mind that the lower you adjust the car, the less working suspension travel you will have. On a smooth surface at speeds, not a problems since you may never bottom out the car, but on a rougher/choppy surface and bottoming out the suspension, can cause the car to unsettle/get way out of shape and kill you instead.

Simply put, although the C6 ZR1 was lowered and re-corner balanced to produce it's fastest lap times around the Nurburgring, it was still using OEM ride height adjusters.

Jcbarr25

Thanks Dano. I will order 4 of the OEM style. When you say corner balance, what do you mean? Is that done in an alignment? Or is it a separate procedure?

cpt11gs

It’s a separate procedure, and only specialty shops will be able to do it. Imagine a chair with 4 legs on a level floor. 3 points (legs) define a plane. The 4th leg needs to be exactly the same height to avoid the chair rocking. On a car, this means setting the ride height at each wheel to balance out the load on each wheel. This is done with a scale under each wheel. It takes a bit of trial and error. Most street cars don’t have adjustable ride height, so you can’t do this on most cars. Corvettes and a few other cars do have adjustable ride height, so it’s possible to do. This is much more commonly done on race cars where you need to get ever ounce of performance possible. This will affect the handling if you get it to far off. For cars that are only driven on the street, you can normally just set the ride height equal and not worry about corner weights. But if you want the best handling, it’s good to do, but can be a bit expensive.

Jcbarr25

Thanks. This is good to know.

Maicol Pregnolato

i've cutted 2 ribs on mine while stil on the car with a string saw...
the good: car is lowered
the bad... makes weird noises and when i bottom out the rear wheels rub into the arch

wish i never did it

Brickmaster

actually having owned NASCAR MODIFIEDS for many years and scales many cars , on a street car with a stock , semi rigid chassis with no triangulated roll cage, you won’t see a big deal of difference by setting cross weights. Without a cage on hard cornering , the car will have a lot of stored energy and load/unload the chassis anyway due to chassis not as ridged as a race car with a cage , so really it is almost a mook point and most drivers will not see the difference.

Keppler

I placed silicon grease between the lowering bolt pad and the lower control arm. After driving HPDE for a few years the lowering bolt pads have not slid out yet.