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Discussion Starter #1
I have an STS V-8. It has 35K miles on it. I recently put these 20 inch Arelli rims on the car. The rims are 5X115 bolt pattern, and Im even using hub centric rings. The tires are 255-35-20. Im running about 42 psi in the front tires since they are kinda skinny......

http://i468.photobucket.com/albums/rr43/Vic_Fabuless/66b738a8.jpg

http://i468.photobucket.com/albums/rr43/Vic_Fabuless/c006c624.jpg

http://i468.photobucket.com/albums/rr43/Vic_Fabuless/59b9a1f6.jpg

My problem is that Im getting a small vibration and harshness in the front area of my car between 1o-30 mph. I feel it everytime I accellerate from a stop. The vibration is only up front, and I feel it through the brake pedal and through the floor of the car up front. Also, when Im stopping between 30 and 15 mph the brake pedal feels like its scraping something rough.

These vibration problems did not occur until I put these wheels on. Any ideas? Should I have them re-balanced?

Thanks in advance!
 

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05 Cadillac STS V6
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546 Posts
Are you feeling it more through the steering wheel? If you have a vibration/balance problem on the front wheels only, you will feel it through the steering wheel. If you have warped rotors or suspension issues, you will feel it through the brake pedal when you touch it. If you have vibration/balance problem in the rear, you will feel it through your seat and the chassis of the car.

Re-balance all 4 wheels and go from there.
 

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2008 STS - Grey/Black Northstar NAV
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My bet is on the offset of the new wheels. Did you verify the offset was the same or at least fully compatible with manf specs or OEM wheels?

Measure from your original inside wheel rim to the wheel hub. Don't measure from the tire to the hub. You can use a yard stick or something else that can easily be cut so that the horizontal stick lays on the wheels metal rim. Then measure down to the hub.

Do the same thing on the new wheels. If is more than 1/4 inch different that could easily explain the whole thing, especially the braking. That was the first clue I picked up on.
 

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Cadillac Owners Troll
2019 CT6 Sport 3.0TT,2015 Luxury ATS , 2016 ELR, and Volt
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First of all, I think your car looks great! Tire balance will not show up at such a low speed so it most likely is runout. I would jack up the front and turn the wheels by hand to see if they have any visible runout or if you feel and hear any interference--it's quite possible that you are rubbing on a caliper. It's very unlikey that alignment can cause this either. Another potential problem during tire changes is that the rotors can get warped if the wheels are over torqued. If the fronts and rears are the same size, you may want to switch them to see what happens. I also think your front pressures are too high. Look on the sidewall and see if there is a max weight rating--that will determine the correct pressure--or look up the brand and size and see what the weight rating is. Good luck!
 

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First of all, I think your car looks great! Tire balance will not show up at such a low speed so it most likely is runout. I would jack up the front and turn the wheels by hand to see if they have any visible runout or if you feel and hear any interference--it's quite possible that you are rubbing on a caliper. It's very unlikey that alignment can cause this either. Another potential problem during tire changes is that the rotors can get warped if the wheels are over torqued. If the fronts and rears are the same size, you may want to switch them to see what happens. I also think your front pressures are too high. Look on the sidewall and see if there is a max weight rating--that will determine the correct pressure--or look up the brand and size and see what the weight rating is. Good luck!
I would go with what he said except for the bit about the rotors. Our rotors slide on over the lugs which are mounted to the hub. The rotor bears no stress from wheel tightening. However that does not mean wheel lug overtightening cannot be an issue, the hub can be distorted as well.
 

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05 Cadillac STS V6
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How do the rotors have no stress? The rotor sits in between the hub and the wheel. If you crank one bolt on the wheel at 150 ft lb, and the other at 90, you are putting stress on that part of the rim, the rotor between the rim and the hub.
 

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Cadillac Owners Troll
2019 CT6 Sport 3.0TT,2015 Luxury ATS , 2016 ELR, and Volt
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I would go with what he said except for the bit about the rotors. Our rotors slide on over the lugs which are mounted to the hub. The rotor bears no stress from wheel tightening. However that does not mean wheel lug overtightening cannot be an issue, the hub can be distorted as well.
You're correct about the rotors, but as you say, the hubs in this case can get distorted taking the rotors with them. This has been a huge issue for GM and others and it took us a while to figure out what really was happening. Most high volume tire dealers are now much more carefull
when it comes to tightening the wheels.
 

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I got a new set of 20" in my storage building now because of the same situation. If you are going to run 20" with the low profile tires, learn to live with the vibration, noise and rough ride. That is the price you pay for that setup.
 

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2006 STS V8 AWD, '95 Ford Ranger
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42 PSI is an awful lot of air for a road car. Backoff to about 32PSI and see if it makes a difference.
 

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I would go with what he said except for the bit about the rotors. Our rotors slide on over the lugs which are mounted to the hub. The rotor bears no stress from wheel tightening. However that does not mean wheel lug overtightening cannot be an issue, the hub can be distorted as well.
I think that is stretching it a bit (not to intend a pun), but warping a hub by even as much as 150 ft lbs of toque would be negligible at best. More likely is the stud would break off before having anything to do with the hub/rotor deflections.
 

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Cadillac Owners Troll
2019 CT6 Sport 3.0TT,2015 Luxury ATS , 2016 ELR, and Volt
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I think that is stretching it a bit (not to intend a pun), but warping a hub by even as much as 150 ft lbs of toque would be negligible at best. More likely is the stud would break off before having anything to do with the hub/rotor deflections.
What you say certainly would sound logical, but unfortunately most of these components are designed right at the limit of performance requirements--mostly due to mass targets. The industry has replaced millions of rotors due to deformation as a result of over torquing.
 

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What you say certainly would sound logical, but unfortunately most of these components are designed right at the limit of performance requirements--mostly due to mass targets. The industry has replaced millions of rotors due to deformation as a result of over torquing.
We haven't...and the measurements taken on cars with slide on warped rotors don't bear this out. I had a 2002 Firehawk and had to machine the rotors every 6,000 miles no mater how I put the wheels on(hand tightened with a torque wrench) myself. The rotors warp due to the way they are used and the material they are made off. My rotors did not stop warping until I put a set of "cryoed" rotors on. Then I went 17,000 miles with no problems from them.

The industry does a lot of things that are unecessay,(3,000 mile oil changes come to mind).:bighead:
 

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I agree. I think it is the rotors. I have 22's on mine but no vibration yet(knock on wood), but when you upgrade to a larger rim like that you should upgrade your barkes as well to compensate. You don't have to, but it helps from problems evolving like this one.
 

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Discussion Starter #20
It not too bad... Im kinda just ignoring it. One day I will have them re-balanced. In the mean time, the vibration is not so bad.. My wife doesnt even notice it but I do because Im really critical. If I find out what it is, I will let you guys know. By the way, I re-tightened all the wheels with my torque wrench. I loosened them, the re-tightened them to 100 pounds. Vibration is still there...

I was told that the 35 series low pro tires need more psi because they are so skinny to help avoid pothole damage. I was told to run between 40 and 50 psi by someone on this site with the low pro tires. I will back them down to 35 psi and see what happens...
 
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