In the fall I bought some Y2k reproduction rims and put them on my 87 vette with 1 1/4" adaptors. I got the wheels balanced at SEARS. Everything was perfect because the sawblades I had on my car beforehand did not have the 3/4" adaptors with it which caused the ABS light to come on. Now with the new rims and adaptors, the abs light went off and it was smooth driving for several months.
Now during the winter, I installed some slotted/drilled rotors with pads from a company in which I bought them from out of California. They worked great and I followed the break in procedure and haven't had any problems for the past 2 months or so. However I took my vette in to get the wheels aligned at FIRESTONE then after that I started experiencing a bad shake on and off with the car whenever I would get up to speeds of 50mph or so. SO I then returned the car back to SEARS and have them rebalance the rims again and they said one of the rims were a little off with the weights and they corrected the problem. I then get to driving again and she feels fine. A few miles down the road, she starts to shake violently again!
I then took her to Firestone to get a second opinion on the balancing and they said the wheels were balanced correctly and that is not my issue. the guy said he took her for a spin and he couldnt even keep his hands on the s teering wheel. As he turned around and headed back to the shop, the car decides to smooth out but yet he feels a very light pulsating.
Then the store manager kept going on and on and would not STFU about the adaptors I have on my car in which he stated that he is positive 100 percent that this is what is causing my car to shake and to put the stock rims on. I told him this did not happened until after I got my car aligned at FIRESTONE. He still wouldn't STFU and made it seem like a bad thing that I got new rims for the car in which I never had a problem!
I read in a thread on the forum that someone mentioned that the drilled slotted rotors they had on their car caused the car to shake excessivly whenever they would get up to speed but not when braking. I do not feel pulsating when I brake. This only happens when I get up to speeds of 50mph or more. It then decides to smooth out on its own. This goes on, on and off at times that I cant even predict when its going to happen. Are my rotors out of balance? I have a 1 year warranty on the rotors and pads if they warp and such. I might give them a call today. Any other ideas??

 

If it is not happening on braking, but only while driving... it could be be a harmonics issue. The shake only happens when the tires are in a certain position.
But that should not be bad enough that you can't hang onto the wheel.
I don't know about adapters. I have never used them. Is is possible that they can shift while driving?

I would take the tires and wheels into someone in your area that has a Hunter road Force balance. Theya re the best at solving wheel/tire balance issues. That will eliminate the possibility of it being tires/wheels.
If they have done an alignment, I can't believe it would be a suspension issue or they would have tried to sell you the repair...

follow the link for a Hunter machine near you

http://www.gsp9700.com/pub/search/FindGSP9700.cfm

 

...this may sound perverted but check your ball joints as well as play in your wheel bearings...

 

The shop did say my RR wheel bearing has a little play in it but not enough to make it vibrate that much. Only happens on and off. Would ball joints really play a factor in this ? what about tierod ends??

 

My money is on your rotors. I read an article recently about a guy having the same problems. It turned out to be his NEW rotors. They were bad from the start. I'd have someone check their truness and balance.

 

That was what I was thinking when I read the thread the guy posted awhile back. I even mentioned it to the guys at FIRESTONE but they kept insisting its not.
The link to the thread I Was reading up on is...
http://forums.corvetteforum.com/show...on&forum_id=48

 

well put the old rims and tires on it. if the prob stops then you know it's the new rims, and you need to have em rebalanced. if it persists, your rotors may be whacked. or your alignment could just be off. mine did this when i first got it. the tires were worn all funny. drove all funky after i had it aligned but i had new rubber on the way and was not gonna drive it on new tires with bad alignment. so yea a bad alignment can and will cause this at higher speeds.

my money is on alignment.

first switch wheels

if no fix then check rotors for egg shapedness

if not then i'd have her re aligned at a better shop.

hope this helps

 

a blown shock can cause skittishness and darting on rough pavement, but your problems are too persistant for that...

Sounds like one of your tires is cupped, it makes the car feel like a wheel is off balance (becomes more noticeable the faster you go), but the tires will balance fine. Cupping may be caused by a bad shock or from the car sitting for long periods (or from the tires being underinflated).

I tend to stay away from firestone, too many horror stories.

Good luck.

 

Firestones have a bad reputation in my book for not knowing jack and doing poor quality work.

 

You should probably explain to them that those adapters were run with that exact same wheel combo for 10,000 miles through 2 sets of tires with no issues, in addition to what you've run with them. They like to point fingers at things they don't understand.

However, they aren't hub centered. So it wouldn't hurt to remove them, rotate them by one lug, then bolt them back up. You never know if the stupid tire tech got carried away and removed one and then didn't tighten it back up evenly.

Can you rotate the rims front to rear?

And, yeah, rotors can still be out of balance and not cause any vibration on braking, only runout or warping will do that. My GM rotors were cast offcenter, cut on center, then they put in a balance weight between two vanes. So the lug holes and rotor surface are all in the right place.. but the mass is still out of round.

I don't think anything in the rear will ever cause a bad shimmy or vibration in the steering. I had a blowout at 70 mph and the car still tracked straight and smooth with my hands off the wheel.

As for a blown shock, I recommend driving without one just so you know what to feel for. This is a nascar trick, apparently the only way a driver learns how to identify a dead shock. But a dead front shock won't cause a shimmy. It'll buck like a bull, but there's really no bump steer whatsoever.

And the part about the ABS sensor.... do you have the same tire diameters front and rear? I don't see how wheels would affect that.

255x50x16s and 255x45x17s have the same diameter.

 

The sawblades I had on before didnt come with the adaptors for the car. This caused the abs light to come on. If I had the 3/4 " adaptors I'm pretty sure the light wouldve gone off anyhow. My wheels were sitting too far inboard to begin with but I lived with the problem for 4 years before I decided it was time for a change. I got new rims then the adaptors.. then the light went off. I learned that improper wheel/tire diamater will cause the abs light to go on. Now that problem has been cured with the new wheels and adaptors. As for my tires.. I have 275x40x17's on all 4 corners and they were on the sawblades and are now on the y2k's.
I called up the company I purchased the rotors from and they are sending in two new front rotors and pads. This was covered under warranty. I should get them by next week, then I'll know for sure if this was the problem to begin with.

 

By guess is the repro Y2K rim is not concentric or when combined
with the new drilled rotor is not concentric. They may be difficlut
to seat properly. You had them seated ok but when
Firestone installed them, they probably used an impact gun and
got one or both of the rims on slightly cocked. I bet when you
carefully install them and hand tighen the lugs then torque them
it is ok?

Place the rim over the rotor and make sure you can't rock it, tighten
and torque the rim, then spin the tire and check for wobble.

If you cant find anyting wrong I would suspect the wheel bearing.
I had what soulds like the same problem. violent shake whould
come & go. Applying the brake and the wheel woud almost rip out
of my hand. I put on a spare bearing and it went away but yet
I couldnot feel any play in the old bearing. Go figure!