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C6 Corvette ZR1 & Z06General info about GM’s Corvette Supercar, LS9 Corvette Technical Info, Performance Upgrades, Suspension Setup for Street or Track
That's what I figured last year when I took it upon myself to come up with a solution. It has been in balance for over a year now. Totally changed the car.
Balanced the rotors with the wheels/tires. I balanced and road forced the new tires. Then we spun the rotors on the balancer. One was 1 oz out, the other 1/2 oz. I marked one hole on the rotor and indexed that to the rim with the lug hole by the valve stem so I can remove and replace everything back to the same spot. I also painted on lug end so everything stays the same. The key was mounting the rotor and wheel on the balancer. We used cones on both sides and I had extra studs and lug nuts that I loosely bolted together. The end result was the machine re-balanced the assembly and it showed out of balance the exact same amount that the rotor alone was out. The weight was applied toward the outer edge of the inside barrel right under the rotor edge. The spinning assembly doesn't care what or where the imbalance is, just that the entire assembly is balanced. Worked like a charm and it only cost me a $25.00 tip to the kid at the tire place I use.
you'll notice that the rotor hat on the newer rotors/cars have drilled and tapped holes, and some came with a little weight bolted to them....now if we could only find the source of those dang on weights, we could balance the rotors like we do tires and live a happy life...but so far I cannot find the published source of where to get those...I suppose one could make his weights out of alum and use thread lock on a machine screw...not sure if that would stay on if you track the car due to the brake temps but....
I don't get it. I had the car out yesterday and it was nothing but smooth the entire evening. Put it through its paces at 70, 80+ etc. No vibration, nothing.
you'll notice that the rotor hat on the newer rotors/cars have drilled and tapped holes, and some came with a little weight bolted to them....now if we could only find the source of those dang on weights, we could balance the rotors like we do tires and live a happy life...but so far I cannot find the published source of where to get those...I suppose one could make his weights out of alum and use thread lock on a machine screw...not sure if that would stay on if you track the car due to the brake temps but....
I have looked, tried calling and e mailing Brembo, looked at Ferrari, Aston and Lambo for the weights...All dead ends
mine has been cured since I tossed out the stock michelins tires (issue was come on go with those)...i run R888 on my stock rims for track use, and I had to put those back on recently for street use (waiting on new street tires for my aftermarket rims) ...0 vibrations (tested up too 85)...and those tires were balanced when new, and have 3 hpde week end and have not been rebalanced...(I was expecting them to vibrate since they are now well worn in from racing, was shocked they didn't)
I've been fighting the issue since I purchased my 2011 about 18 months ago. The car came with 6k miles and still had the original PS2 tires and CC rotors. After much trial and error, balancing, and throwing parts at it we discovered that one of the original front rotors was badly out of balance and was causing the bulk of the problem.
I now have new OEM wheels, new MPSS tires, and new AC Delco 177-1120 front rotors. Even with all of that and conventional road force balancing (by "conventional" I mean the wheel/tire only on the balancer like you would normally do) I was still getting significant vibration through the steering wheel at speeds over ~70mph. The thing that has finally solved it for me (and its still not perfect, but WAY better and very livable now) was indexing each rotor to its wheel, mounting them together, and then balancing the whole thing as an assembly.
After running across a guy on YouTube do something similar with his Ferrari wheel and CC rotor, I used a high quality wheel adapter, which effectively simulates the wheel hub, to bolt each rotor to its wheel. I marked an index point on the rotor and on the wheel so that I could re-install on the car in the same orientation. Then the helpful and patient folks at my local Discount Tire agreed to balance these assemblies on their Hunter machine for me and we ended up with 18lbs and 20lbs of road force on the fronts. Those numbers are not ideal, (would have liked to see 15lbs or less) but after test driving the car it is like night and day. It's better than anything we could accomplish with the original rotors and much better than not including the rotor in the balancing at all.
As an example, we did one iteration where we first checked road force on the new front wheels and tires. The numbers came in at a very good 7lbs and 10lbs. Then we added the original rotors and rebalanced them as assemblies. This yielded road force numbers of 24lbs on one and 73lbs (it took 4 oz to balance!!) on the other So, clearly, the rotors were having a large impact on the balance of the system. This is when I decided to purchase the new AC Delco 177-1120 replacement rotors since I knew at least one of the originals was bad. Note that even with the 73-pounder in the equation, but balanced as assemblies it was still better than using the new rotors and not balancing them as assemblies. I hope that makes sense.
A couple of notes FWIW:
- I never tried using a non-runflat tire as some others have suggested. I considered the Conti's, but ultimately went with the PSS instead. I wouldn't be surprised if the runflats, with their stiff sidewalls, magnify the issue to a degree.
- The AC Delco 177-1120 rotors that I received were marked February 2018 and they look like a newer design. Gone are the little threaded holes between the ring attachment fasteners and balancing now appears to be done by milling the edge of the rotor like you would see on a conventional iron rotor.
Anyway, I hope this helps and am happy to post up some pics that I took along the way if anyone's interested.
So I've pulled together some pics on the off chance that it helps someone down the road.
Part number info from the AC Delco replacement rotors:
Date stamp on box:
View of rotor/hat:
Material removed from edge of rotor (presumably for balancing):
Example of the wheel adapter/spacer that I used, which is one I happened to have on hand. In the future I will use a hubcentric version that will better approximate the actual wheel hub (should do a more precise job of centering the rotor relative to the wheel). For reference these cars have a 5x4.75" bolt pattern, 70.3mm hub bore, M12x1.5" wheel stud and, FWIW, my spacer was 1" thickness and, based on interface to the Hunter balancing machine at the tire store, I wouldn't go any less than that.
View of rotor assembled to wheel (that's one front wheel stacked on top of the other in case you get some type of optical illusion ):
View from what (would be, if installed) inboard side:
I've been fighting the issue since I purchased my 2011 about 18 months ago. The car came with 6k miles and still had the original PS2 tires and CC rotors. After much trial and error, balancing, and throwing parts at it we discovered that one of the original front rotors was badly out of balance and was causing the bulk of the problem.
I now have new OEM wheels, new MPSS tires, and new AC Delco 177-1120 front rotors. Even with all of that and conventional road force balancing (by "conventional" I mean the wheel/tire only on the balancer like you would normally do) I was still getting significant vibration through the steering wheel at speeds over ~70mph. The thing that has finally solved it for me (and its still not perfect, but WAY better and very livable now) was indexing each rotor to its wheel, mounting them together, and then balancing the whole thing as an assembly.
After running across a guy on YouTube do something similar with his Ferrari wheel and CC rotor, I used a high quality wheel adapter, which effectively simulates the wheel hub, to bolt each rotor to its wheel. I marked an index point on the rotor and on the wheel so that I could re-install on the car in the same orientation. Then the helpful and patient folks at my local Discount Tire agreed to balance these assemblies on their Hunter machine for me and we ended up with 18lbs and 20lbs of road force on the fronts. Those numbers are not ideal, (would have liked to see 15lbs or less) but after test driving the car it is like night and day. It's better than anything we could accomplish with the original rotors and much better than not including the rotor in the balancing at all.
As an example, we did one iteration where we first checked road force on the new front wheels and tires. The numbers came in at a very good 7lbs and 10lbs. Then we added the original rotors and rebalanced them as assemblies. This yielded road force numbers of 24lbs on one and 73lbs (it took 4 oz to balance!!) on the other So, clearly, the rotors were having a large impact on the balance of the system. This is when I decided to purchase the new AC Delco 177-1120 replacement rotors since I knew at least one of the originals was bad. Note that even with the 73-pounder in the equation, but balanced as assemblies it was still better than using the new rotors and not balancing them as assemblies. I hope that makes sense.
A couple of notes FWIW:
- I never tried using a non-runflat tire as some others have suggested. I considered the Conti's, but ultimately went with the PSS instead. I wouldn't be surprised if the runflats, with their stiff sidewalls, magnify the issue to a degree.
- The AC Delco 177-1120 rotors that I received were marked February 2018 and they look like a newer design. Gone are the little threaded holes between the ring attachment fasteners and balancing now appears to be done by milling the edge of the rotor like you would see on a conventional iron rotor.
Anyway, I hope this helps and am happy to post up some pics that I took along the way if anyone's interested.
Geez, I am actually in the decision making mode of selling my 08 Z06 and looking for a 2011+ ZR1. This vibration issue really concerns me. Very similar to the guide wear issue on my Z06. Why can't these cars just be right?
I agree with 71ho454, I have the c6z with grenade heads still attached. And on my c5z I bought dozens of cheap white box rotors with milled edge to balance, and NEVER had a vibration issue.
Seems like GM comes up with outstanding new Corvettes, but always there is a fatal flaw and to make it worse GM refuses to acknowledge the problem. Jerks.
I agree with 71ho454, I have the c6z with grenade heads still attached. And on my c5z I bought dozens of cheap white box rotors with milled edge to balance, and NEVER had a vibration issue.
Seems like GM comes up with outstanding new Corvettes, but always there is a fatal flaw and to make it worse GM refuses to acknowledge the problem. Jerks.
Froggy
I want a ZR1 in a bad way, but I don't want to be chasing a vibration issue like the rest of these guys/gals. I want to be out experiencing the rush of a blown LS9, instead of grinding my teeth over another C6 Corvette issue. No thanks..
I bought brand new and had this issue with all 4 rotors as GM finally admitted after 11 visits into dealer chasing this. They changed one rim, two tires, and 4 rotors and I was perfect. I am now seeing new owners of these low mileage cars having this issue. Bottom line alot of ZR1 owners back then did not put alot of miles on their cars. Some had it some didn't. But those owners didn't deal with it so any prospective buyer has to realize this. Having bought new rotors and pads they are EXPENSIVE, so add that into your purchase price. Most vibrations are the rotors. GM swapped them to the new ones back then if you didn't let up. They rode it out and stuck everyone that didn't. But some did have bad run flats that sat a lot. Some were hubs. Some were light rust on the hub surface. Some were rims. After working your way in from the tire to rim to rim runout to hub to hub runout if all is perfect then its rotors. It doesnt take much in the rim or tire to get a vibration on a 20" rim with a hard side wall. Run flats were the first thing I got rid of. After they did all of that it still vibrated. They changed rotors and pads to new design and it was totally gone.
I bought brand new and had this issue with all 4 rotors as GM finally admitted after 11 visits into dealer chasing this. They changed one rim, two tires, and 4 rotors and I was perfect. I am now seeing new owners of these low mileage cars having this issue. Bottom line alot of ZR1 owners back then did not put alot of miles on their cars. Some had it some didn't. But those owners didn't deal with it so any prospective buyer has to realize this. Having bought new rotors and pads they are EXPENSIVE, so add that into your purchase price. Most vibrations are the rotors. GM swapped them to the new ones back then if you didn't let up. They rode it out and stuck everyone that didn't. But some did have bad run flats that sat a lot. Some were hubs. Some were light rust on the hub surface. Some were rims. After working your way in from the tire to rim to rim runout to hub to hub runout if all is perfect then its rotors. It doesnt take much in the rim or tire to get a vibration on a 20" rim with a hard side wall. Run flats were the first thing I got rid of. After they did all of that it still vibrated. They changed rotors and pads to new design and it was totally gone.
I bought brand new and had this issue with all 4 rotors as GM finally admitted after 11 visits into dealer chasing this. They changed one rim, two tires, and 4 rotors and I was perfect. I am now seeing new owners of these low mileage cars having this issue. Bottom line alot of ZR1 owners back then did not put alot of miles on their cars. Some had it some didn't. But those owners didn't deal with it so any prospective buyer has to realize this. Having bought new rotors and pads they are EXPENSIVE, so add that into your purchase price. Most vibrations are the rotors. GM swapped them to the new ones back then if you didn't let up. They rode it out and stuck everyone that didn't. But some did have bad run flats that sat a lot. Some were hubs. Some were light rust on the hub surface. Some were rims. After working your way in from the tire to rim to rim runout to hub to hub runout if all is perfect then its rotors. It doesnt take much in the rim or tire to get a vibration on a 20" rim with a hard side wall. Run flats were the first thing I got rid of. After they did all of that it still vibrated. They changed rotors and pads to new design and it was totally gone.
Wow, that is a lot of interesting reading. I can’t even imagine having to replace 4 carbon ceramic rotors after spending $60k plus, but then again, I’m not really surprised. Fingers crossed!! Thanks for the info..
I just put my 19" Forgestars rims back on with new tires, 0 vibration. I'll also note that my stock rims with R888 with a bunch of HPDE on them did not give any signs of the vibration I had when the car was new when driving on the highway at the same speed the vibration would show up. After 6 years of ownership, I'm going to say most of my vibrations had to be stock tires (because even new rotors didn't do it back then). Seems very hit or miss and very inconclusive as to what exactly does it.
I have a 2007 C6 Z06 and I too am experiencing/chasing down a vibration. Granted my MT ET Street tires are pretty worn especially the passenger side. But at 80+mph the steering wheel vibration is absolutely ridiculous.
Changed rear hub assembly to SKF racing hubs thinking it was that. Nope.. still there. I am going to try new MT ET streets and an alignment to see if that will help. After that.. I guess rotors?
I have a 2007 C6 Z06 and I too am experiencing/chasing down a vibration. Granted my MT ET Street tires are pretty worn especially the passenger side. But at 80+mph the steering wheel vibration is absolutely ridiculous.
Changed rear hub assembly to SKF racing hubs thinking it was that. Nope.. still there. I am going to try new MT ET streets and an alignment to see if that will help. After that.. I guess rotors?
AFAIK, the CCB option wasn't offered on Z06 until 2011 so unless you've swapped your brakes to the carbon ceramics then I suspect you're off the hook on this issue and instead dealing with a more conventional balance problem (one that is probably much easier/cheaper to fix ).
Rule of thumb says that if you're feeling vibration in the steering wheel then its front end and if you're feeling it through the seat (i.e. your butt) then it's from the aft end. Based on your description my first step would be to road force balance the front wheels/tires and see if that eliminates the vibration. Here's a link to the Hunter website that will help locate a road force balancer near you https://www.hunter.com/gsp9700 If that doesn't fix it then next step would be to check the tires and wheels for damage. I've had really old tires flat-spot on me and vibrate regardless of other efforts and a damaged wheel will cause vibration. These things should show up during road force balancing, though, if an excessive amount of weight is needed to balance. Third step would be to investigate bushings and other suspension related issues. Iron rotors, though, creating a vibration is rare based on my experience. It can happen (I did get a set of bad Brembo replacement rotors once upon a time so it is possible), but it would be far down the list of concerns in my troubleshooting .
06-19-2017, 09:01 PM
So, clearly, the rotors were having a large impact on the balance of the system. This is when I decided to purchase the new AC Delco 177-1120 replacement rotors since I knew at least one of the originals was bad. Note that even with the 73-pounder in the equation, but balanced as assemblies it was still better than using the new rotors and not balancing them as assemblies. I hope that makes sense.
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