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2009 Procharged SRT8 6.1L, Orange Julius
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Discussion Starter #1
I bought 17x4.5 front and 17x9.5 rear wheels from Race Star. So far so good. Went with Mickey Thompson Sportsman S/R 6x28R17 for the front and Mickey Thompson 305x45x17 for the rear. When the tires were mounted to the wheels, they were balanced. Had a terrible vibration. A performance shop suggested that I take the weights off the rears and that vibration is normal but nothing that would make me feel uneasy/unsafe about driving. I took the weights off the rears but I'm still getting heavy vibration (steering wheel shake) at 60mph or faster. How much of a vibration is ok and considered normal? If this is happening at 60, what happens when I get to 120?

I didn't use any spacers. I used Race star OEM lug nuts with the rubber ring. Front tires were balanced when mounted. I hand tightened all nuts and retightened them again after a test drive. Front wheels are at 48psi. Rears are at 30psi.
 

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48 psi is a lot and will make you feel everything more but really there shouldn't be much vibration at all especially in the steering wheel, if you're feeling it in the wheel then it's more likely the front tires than the rear, i also wouldn't have taken the weights off the rear tires though, that will actually cause a vibration on it's own but you'll feel that more in the seat usually rather than the wheel
 

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2009 Procharged SRT8 6.1L, Orange Julius
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Discussion Starter #3
48 psi is a lot and will make you feel everything more but really there shouldn't be much vibration at all especially in the steering wheel, if you're feeling it in the wheel then it's more likely the front tires than the rear, i also wouldn't have taken the weights off the rear tires though, that will actually cause a vibration on it's own but you'll feel that more in the seat usually rather than the wheel
I was going off of the load capacity. For the skinnies, the max load capacity is 1175 lbs @ 50psi. I figured because of the weight of our cars, esp it being heavier in the front, it should be close to that.
 

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2020 r/t scat pack 50th anniversary wide body
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try putting the car up on stands spin the tires make sure rims and tires are running true , at that time check tirod ends and wheel bearings, wont be the first time that you change one thing and any weakness with other parts show up.
 

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Discussion Starter #5
try putting the car up on stands spin the tires make sure rims and tires are running true , at that time check tirod ends and wheel bearings, wont be the first time that you change one thing and any weakness with other parts show up.
Will do. Thank you!
 

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I bought 17x4.5 front and 17x9.5 rear wheels from Race Star. So far so good. Went with Mickey Thompson Sportsman S/R 6x28R17 for the front and Mickey Thompson 305x45x17 for the rear. When the tires were mounted to the wheels, they were balanced. Had a terrible vibration. A performance shop suggested that I take the weights off the rears and that vibration is normal but nothing that would make me feel uneasy/unsafe about driving. I took the weights off the rears but I'm still getting heavy vibration (steering wheel shake) at 60mph or faster. How much of a vibration is ok and considered normal? If this is happening at 60, what happens when I get to 120?

I didn't use any spacers. I used Race star OEM lug nuts with the rubber ring. Front tires were balanced when mounted. I hand tightened all nuts and retightened them again after a test drive. Front wheels are at 48psi. Rears are at 30psi.
Have to agree with Jelli79. Front tire pressure is quite high and based on my experience with one other car just a few PSI over the factory recommended inflation pressure had the car manifesting a "wheel/tire" vibration that had me at one point convinced there was a balance problem. Thankfully I had enough presence of mind to bring the tire pressures back to factory and the vibration gone.

Now you have installed front tires that are not "factory" so you really have nothing to go on for what the factory tire pressure should be. While I want to avoid over inflation I certainly don't want to run the tires at too low a pressure either.

Experiment to see if lowering the front tire pressure helps or not. That you removed the weights on the rear wheels might cause some real tire balance vibration so this might muddy the results of lowering the front tire pressures.

To eliminate one possible and easily corrected contributor to the vibration I'd get the rear wheels balanced again and leave them alone. Drop the front tire pressures. How much to drop I'll leave to you. You want to drop the tire pressure enough to have some confidence if the vibration is still present that it is not due to too much air pressure. But at the same time you do not want to drop the tire pressures to an unsafe level.

Really you might -- I say might -- be faced with a situation in which the front tires given their size and load rating may require more pressure which can be a contributor to the vibration.

Maybe you can put on a set of stock front wheels/tires and see if this helps?
 

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2009 Procharged SRT8 6.1L, Orange Julius
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Discussion Starter #7
I appreciate the advice. I'll try lowering the pressure to see if that helps and look at the tie rod ends and wheel bearings. If nothing stops or at least minimizes the steering wheel shake, I'll put the OEM wheel set on the front and compare.
 

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2009 Procharged SRT8 6.1L, Orange Julius
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Discussion Starter #8
I lowered the psi to 42. I didn't go crazy with it but I got it up to at least 85mph on the street and there was a very minor steering wheel shake. MUCH BETTER than before lol. So that helped a lot. My car is not my daily driver so as far as storage, is it ok to leave the skinnies on the car at 42psi until track days or swap them out with the OEMs?
 

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If you are running the stock 2 piece driveshaft check the center support bearing for the rubber mounting failure. It can transmit vibrations throughout the car and the closer to total failure the worse it gets.
 

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Discussion Starter #10
If you are running the stock 2 piece driveshaft check the center support bearing for the rubber mounting failure. It can transmit vibrations throughout the car and the closer to total failure the worse it gets.
That's actually my next upgrade - drive shaft. I've been looking at parts all week. Deciding when I should bite the bullet and buy.
 

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My center bearing rubber support failed at 58,000 miles, I am so glad I discovered it when I did, you can unbolt and slide the heat shield out of the way to check it.

260152
 
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I lowered the psi to 42. I didn't go crazy with it but I got it up to at least 85mph on the street and there was a very minor steering wheel shake. MUCH BETTER than before lol. So that helped a lot. My car is not my daily driver so as far as storage, is it ok to leave the skinnies on the car at 42psi until track days or swap them out with the OEMs?
For long term storage it is advisable to inflate the tires to if not to the their max rated pressure at least close to it. (The max pressure should be on the side wall. Do not over inflate!)

For example both my Scat Pack and Hellcat were delivered to me with the tires inflated to 45psi. This is what the factory inflates the tires to for long term storage which is essentially what the car experiences waiting to be sold. 'course, the tire pressures were too high for driving but the dealer, two different dealers about 40 miles apart, couldn't be bothered to set the tires pressures to the correct and safe value.
 

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2009 Procharged SRT8 6.1L, Orange Julius
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Discussion Starter #13
My center bearing rubber support failed at 58,000 miles, I am so glad I discovered it when I did, you can unbolt and slide the heat shield out of the way to check it.

View attachment 260152
I'll definitely take a look at it since I'm upgrading it anyway. Hopefully there is some resale value in it. I probably need to go ahead and upgrade my axles too.
 

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Discussion Starter #14
For long term storage it is advisable to inflate the tires to if not to the their max rated pressure at least close to it. (The max pressure should be on the side wall. Do not over inflate!)

For example both my Scat Pack and Hellcat were delivered to me with the tires inflated to 45psi. This is what the factory inflates the tires to for long term storage which is essentially what the car experiences waiting to be sold. 'course, the tire pressures were too high for driving but the dealer, two different dealers about 40 miles apart, couldn't be bothered to set the tires pressures to the correct and safe value.
I think that was the issue. After they were mounted and balanced, I set the psi to 48 because of how heavy our cars are up front. Forgetting that heat will add pressure as well. If the max load capacity is 1175lbs/tire at 50psi, well I was definitely overinflated after driving it which I think caused the steering wheel to shake. Now that I know better, I'll do better lol I increased the psi for storage purposes and will reduce it when driving. I'm just glad I don't have to play musical chairs with my front tires because that would be annoying.
 

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Did you ever get this sorted. You shouldn't have any vibration at all from the tires if they are balances properly. Removing the weights is bad advice, find another shop.

If they get balanced properly and there is still vibration it's not the tires. There are other things that can cause vibration. Take a look at your rotors. I had substantial brake deposits that was causing vibration at freeway speeds. Changed the rotors and vibration went away. If you have brake deposits on the rotors it will be obvious. Here is what mine looked like...
261299



As for tire pressure, there is a sticker inside the driver door jam that has the recommended tire pressure, start with that tire pressure stock tires or not. I recommend you use that pressure unless the new tires have a different load rating.
 

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Discussion Starter #16
It wasn't so much the vibration like I thought, it was the steering wheel shake that was the problem with the skinnies. Once I put my stock wheels back on the front, because I thought it was a tire issue and was prepared to send them back under warranty, I had no steering wheel shake whatsoever at any speed...and I still had the 305s on the rear. No vibration, no steering shake...normal driving. So I took my skinnies to another shop to get a second opinion before they dismounted the tires. They said the tires are good and they rebalanced them for me. I haven't driven on them yet. Awaiting my one-piece carbon fiber driveshaft (5 weeks out) before I try them again. I was never going to drive on them normally anyway. I was test driving them to get comfortable with them on.
 
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