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 255/60R15 too wide for all 4 corners?

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metalmolder

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PostSubject: 255/60R15 too wide for all 4 corners?   Thu Dec 01, 2016 10:44 pm

Hello everyone!

Before I start, I have looked through the tire and wheels section of the forum and googled for a few days now for an answer and have yet to get a definitive answer. I am 80% sure that they will maybe work but I want to be at least 95% sure before I drop big bucks on a set of tires. I'm sorry if this has been answered before but I'm going to go ahead and ask...

I recently purchased this set of nice 9C1 steel wheels and center caps. the tires on the rims are toast and will need replacing, or maybe a smoke show is in order?



I want to put some nice wide rubber on all corners for that stocky square look. I have found Cooper Cobra radial GT's with the raised white letter in a 255/60R15 for a reasonable price and from what I've read the tires should fit the rim with just a little sidewall bulge (9 somtin" tire on 7" rim). but will this particular combo fit all around? I'm ok with some slight rub at full lock in the front but if there's serious fender/frame interference front or rear then I'll consider a narrower 235/70R15.

Thanks!
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Fred Kiehl

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PostSubject: Re: 255/60R15 too wide for all 4 corners?   Fri Dec 02, 2016 9:17 am

I have 255/60/15s on the rear of my 91 OCC and they do not rub anywhere. It is even lowered 2 inches. The fronts should be OK at stock height as well. I just put 225/60/17s on the front, and about a 3 inch drop on the front with spindles and springs. This pushes the tire out about 3/8 of and inch as well. They are squeaky tight, and I may go to 215/60/17s. The 255s are about 1 inch shorter than the stock tires, so you will need an adjustment in your speedometer gear on a 91-93, or computer reprogram for the 94-96 (I cannot determine the year from your picture). The speed difference is about 3-5 MPH. If you installed a stock Impala computer in a 94-96, it would not need any tuning, because the tires are the same as size as the Impala. The only time the fronts will have a chance of hitting is maximum lock, and sharp turning and hitting a bump at the same time.

I have heard that 275s will fit on the rear, and possibly a 295s.
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jasonlachapelle

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PostSubject: Re: 255/60R15 too wide for all 4 corners?   Fri Dec 02, 2016 9:44 am

The only place you MIGHT get some rubbing as at max deflection, against the swaybar. It will be fine in the back.
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Fred Kiehl

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PostSubject: Re: 255/60R15 too wide for all 4 corners?   Fri Dec 02, 2016 9:56 am

You could bend the steering stops a little to keep the tires from hitting the frame/anti-roll bar. Since you are using the wider tire, and it will not affect the turning radius any more than the tires.
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Andebe

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PostSubject: Re: 255/60R15 too wide for all 4 corners?   Fri Dec 02, 2016 10:00 am

From my experience,I think your all good. The side bulge shouldnt be an issue,unless you drive it in the winter. First cold snap,might give the illusion that your tires,are flatter than they actually are. I think its a good looking set up. Enjoy your smoke show... Twisted Evil
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metalmolder

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PostSubject: Re: 255/60R15 too wide for all 4 corners?   Fri Dec 02, 2016 11:24 am

Thanks for the input everyone! I'm glad I can run the wider ties. It's a 95 so it'll need some reprograming for the speedometer but I plan on sending out the ecm for tuning this winter so I'll have that done at that time. Otherwise I plan on running stock hight so that should help my clearance.
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jasonlachapelle

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PostSubject: Re: 255/60R15 too wide for all 4 corners?   Fri Dec 02, 2016 11:44 am

Hopefully your car is on winter tires for the winter...

Great plan on getting your car tuned. If you don't have the cable to do load it yourself, make sure you do the most things you can at once.

If your winter tires are still 28" tall you could split the difference and get the tuner to make the tune for 27.5". You'll be just slightly over/under half the time and it should balance out.
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metalmolder

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PostSubject: Re: 255/60R15 too wide for all 4 corners?   Fri Dec 02, 2016 1:09 pm

Admittedly this wagon will become a summer driver. It already has some minor rust and I want to do what I can to prevent any further rust. I'm near Chicago and it's scary how much salt they use. Also my current plan is for a stroker LS engine and a T56 manual swap. Aiming for mid 500 whp. However those plans a few years out so in the mean time I'm just going to have some fun! Very Happy
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TheRoadmasterKing



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PostSubject: Re: 255/60R15 too wide for all 4 corners?   Fri Dec 02, 2016 1:14 pm

Here's a visual comparison of both sizes, hope this helps:
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jasonlachapelle

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PostSubject: Re: 255/60R15 too wide for all 4 corners?   Fri Dec 02, 2016 1:28 pm

metalmolder wrote:
Admittedly this wagon will become a summer driver. It already has some minor rust and I want to do what I can to prevent any further rust. I'm near Chicago and it's scary how much salt they use. Also my current plan is for a stroker LS engine and a T56 manual swap. Aiming for mid 500 whp. However those plans a few years out so in the mean time I'm just going to have some fun! Very Happy

That's a great plan for a different car. You're better off getting a non-rusty one from down south with a blown engine/trans.
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metalmolder

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PostSubject: Re: 255/60R15 too wide for all 4 corners?   Fri Dec 02, 2016 2:08 pm

jasonlachapelle wrote:
metalmolder wrote:
Admittedly this wagon will become a summer driver. It already has some minor rust and I want to do what I can to prevent any further rust. I'm near Chicago and it's scary how much salt they use. Also my current plan is for a stroker LS engine and a T56 manual swap. Aiming for mid 500 whp. However those plans a few years out so in the mean time I'm just going to have some fun! Very Happy

That's a great plan for a different car.  You're better off getting a non-rusty one from down south with a blown engine/trans.  

You are 100% correct, that's what I should do. But I got this one for a great deal and the rust is isolated to two small areas the body. The frame is solid and rust free which (I feel) Is more important. If funds are flowing a bit more freely in the future then I'll absolutely buy a rust free southern car but for now I play the cards I was dealt.

I'm just happy to be in wagon after all!
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RedandBlack

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PostSubject: Re: 255/60R15 too wide for all 4 corners?   Fri Dec 02, 2016 3:00 pm

Fixed a rusty Northern car.

Wouldn't do it again.

Still love it to death, though.
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SF SoBay

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PostSubject: Re: 255/60R15 too wide for all 4 corners?   Mon Dec 12, 2016 12:12 am

I recently replaced 275/35 20inch Boss wheels with US Mag wheels “Big Slot” 17 x 8 and Nitto 255/50 17 tires.
The right rear wheel has little clearance between the skirt and the sidewall.
In right hand turns there was contact at the right rear with the new wheel.  
Dr. DeWalt removed about 3/16” from the inside of the skirt and eliminated the problem.  

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Fred Kiehl

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PostSubject: Re: 255/60R15 too wide for all 4 corners?   Mon Dec 12, 2016 6:38 am

That could have been caused by the offset of the new wheels.
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TheRoadmasterKing



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PostSubject: Re: 255/60R15 too wide for all 4 corners?   Mon Dec 12, 2016 6:51 am

Hey Fred I have a question. What does wheel offset mean? I've looked it up but it still confuses me. When I look up wheels on SummitRacng when I'm bored and have nothing else to do I always look for a 15x7 wheel, 5x5 bolt pattern, and 0.00mm offset. What happens if there is an offset?
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Fred Kiehl

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PostSubject: Re: 255/60R15 too wide for all 4 corners?   Mon Dec 12, 2016 7:30 am

There should be a positive offset to your wheels. About a quarter to half inch offset (offset 6mm/backspace 121mm). It means that the mounting flange for the wheel is not centered between the inside and outside of the tire seat flanges. In the case of the B body wheels, the mounting flange is about a half inch to the outside of the centerline of the wheel. If you go here: http://www.rimsntires.com/specspro.jsp you can play around with the numbers. You can use a wider rim, up to 9 inches in some instances, as long as your offset is correct. Just make sure the tires do not hit the body, and have a little room for suspension slop. The example above may have been cured by shifting the body instead of cutting the wheel opening flange.

To use wider rims and larger tires, make sure your body is centered on the frame. First measure the distance between the body and frame on both sides. If there is a discrepancy, you can loosen all of the body mounts, and pry the body toward the smaller side until the measurements are the same. then retighten the body mounts.
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SF SoBay

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PostSubject: Re: 255/60R15 too wide for all 4 corners?   Mon Dec 12, 2016 12:16 pm

The 20 inch wheels had a backspace of 3.75 " the 17 inch wheels had a backspace of 4.5" and no offset.
My odometer turned over 73 years last week and with two back issues this summer shifting the body vs some cutting, the choice was made.
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Fred Kiehl

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PostSubject: Re: 255/60R15 too wide for all 4 corners?   Mon Dec 12, 2016 12:45 pm

You forgot the rim width. That must be included in the calculation. The "no offset" will cause the wheel to extend further out into the wheelwell. There is no way to change a "no offset" wheel's position in the wheelwell toward the inside. That is why some offset is necessary to make the tire fit properly. A 1/2 inch positive offset would have fit without modification.
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SF SoBay

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PostSubject: Re: 255/60R15 too wide for all 4 corners?   Mon Dec 12, 2016 4:53 pm

The new 17" rims are 8" width as noted, and the 20" rims were also 8" in width. Had the body been centered on its frame, it's likely that there would have been sufficient clearance. I was limited in the configuration for the wheel style I chose and the application for the RMW was noted by the vendor. The Nitto tires are the 455's as one of the choices you had recommended. This brought me to 17" rims and the whole result is very satisfactory. Great tires, some reviews comment on traction concerns in the wet. So far I'm loving them.
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RedandBlack

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PostSubject: Re: 255/60R15 too wide for all 4 corners?   Tue Dec 13, 2016 9:38 pm

Looks good.

Needs to be lowered though.
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