Rim Bolt Pattern Question???

[STS2002]

I have an 05 STS 1SF that I bought used and came with the 08 STS 18 in rims (dealer thought it would give it a fresh look). Anyway....I have been battling with a vibration issue that seems to be an rim issue. I have ruled out a tire problem, because I have replaced the tires and it is still there. There is one thing i noticed about the rims and was wondering if anyone knew if this would create a big issue. The 05-07 18in rims have a a bolt pattern of 5x115 and the 08 18in rim that I have on my 05 has a bolt pattern of 5x4.5. Could this difference in bolt pattern cause a vibration???

Thank you in advance for you help.
Phil

[MOINEX]

Could it be a tire balance problem? Per dealer, the tires should be Road Force Balanced. Had it done on mine. It makes a big difference.

[STS2002]

Originally Posted by MOINEX

Could it be a tire balance problem? Per dealer, the tires should be Road Force Balanced. Had it done on mine. It makes a big difference.

Yeah...had that done like 3 times. I am at my whits end. The vibrations were coming through the front floorboard and the front seats and always between the speeds of 50-54, 60-64, and 70-74. The vibrations also have a rythym.....the vibration would come for 5 seconds and then go away for like 4 seconds and starts the cycle over and over. I have one tire and rim combination that is just terrible and creating this horrible vibration.

I took the rim to a guy who makes rims round (this rim was out of round by .0050 of an inch and they got it down to .0010 of an inch and cadillac says that the rim should be no more than .0020 out of round) and after he did that all the vibrations went away.

Then after a while they started to back a little and I took it back to the dealer to have them road forced. They couldn't get it down past 24lbs of radial force and Cadillac says it should be no more than 18lbs. So.....assuming that the rim is now perfectly round (since the rim guy took care of it) it must be a bad tire to be making this vibration.

Then I noticed the bolt patterns are different and it aroused my curiosity. In any case....the dealer is pretty much telling me that this is the way the car drives and basically there is nothing more to do. I get soooooo frustrated because I am the one driving it everyday and it happens infrequently at different temperatures, mornings, nights, so when I take it to them, they think i'm crazy. I didn't buy this car to enjoy vibrations and I don't believe that I have to settle with this.

I could just screem when I think about all the time, money and effort in trying to get this to go away. If anyone has any suggestions or went through something similar, your input would be much appreciated. I think my next step is to either take the rim back to the guy who fixed it and tell him that now the tire won't road force and the ride is bad or I attempt to spend $240 on a new tire.

Phil

[sapien]

Tire Rack and Discount Tire both list 05-07 and 08 STS as 5x115mm bolt pattern...

I was told by a wheel/tire tech that if 5x4.5" (5x114.3mm) wheels were used on a 5x115mm hub, that they would eventually fall off because the lugs won't seat perfectly.

[z06bigbird]

Originally Posted by sapien

Tire Rack and Discount Tire both list 05-07 and 08 STS as 5x115mm bolt pattern...

I was told by a wheel/tire tech that if 5x4.5" (5x114.3mm) wheels were used on a 5x115mm hub, that they would eventually fall off because the lugs won't seat perfectly.

Printed technical materials agree on the idea that the 114.3 wheels will eventually fall off.

[C&C]

0.7 mm is approximately 27.5 thousandths of an inch (this is significant). A piece of paper is approximately 3 thousandths of an inch thick, so to get an idea how far off the lugs would be setting from a correct fit, put 8 or 9 pieces of paper stacked together to see just how far off it would be.

[STS2002]

Originally Posted by z06bigbird

Printed technical materials agree on the idea that the 114.3 wheels will eventually fall off.

z06bigbird.....wow, i never would have thought that such a small difference would make such a bad outcome. Do you have a copy of that printed material....or a place where I could find that??

Thank you everyone for your input...if has been insightful!!

Phil