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Discussion Starter #1
Guys,

I´ve searched high and lo here but could not find any info on whether 15X7 TTs will work using 235´s up front. It seems that the rallys with 4.25 BS will fit based on the posts Ive read but now I´m worried since mine are 3.75 BS. I will be installing brand new stock BB springs at the same time, so I´m hoping I´ll be ok.

Any others run this combo ? Do not want rubbing issues....

Thanks!
 

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Andre,

I just responded this week to a question another Forum member PM'd me on. The issue with the TT2 is the negative offset cause by only 3.75 BS. I believe this member had only 3.50" Back Spacing. This person's car was a 1968 Camaro. Out of respect for their privacy I won't mention who they were but we had a nice conversation over PM's and I did my best to help.

Here is the deal. I wasn't born yet when the first 1968 Camaro's rolled off the assembly line in Sept of 1967. But I do know this. The 1968 Z28's had E60x15 tires. Maybe E70x15. I believe E60x15 to equate to P215/60/R15. The P235/60/R15's will rub with that backspacing. I have a 1969 Camaro w/ 15x7 Rally's and I don't have any issues with rubbing and I run P235/60/R15 all the way around. That is because of the backspacing on Rally's. I also have disc brakes on the front of my car and that could make a difference. Most if not all drum brake cars received 14x6 if they were not Z28's. Some SS's received 15x6 if I recall. Most Rally's were 15x7's.

Remember in 1968 cars were still using Bias ply tires. Bias ply tires have more of a square shoulder where as radials have a more rounded shoulder to improve handling & cornering. But the rounded shoulder also will cause tire rub as it increases the contact patch which is known as the footprint of the tire. Just because a tire is a P235/60/R15 form two different manaufactures does not mean it has the same footprint/contact patch. One could still be taller and the other wider depending on the castings/moldings & design by that manufacturer.

Please note: I was in the tire & auto service indurty from 1989-1998. Mostly as an assitant service manager or service writer. Tires were my specialty even at new car dealerships. But since I left the business in 1998 I no longer consider myself an expert in anything and I humble myself everyday when it comes to learning about old cars or new cars. That way I can still learn new things instead of being some arrogant jerk.


Here are 2 helpful links. http://www.turbinecar.com/tires.htm

Drag your mouse over the photos to see how skinny the tires were on these cars.
http://www.kelseytire.com/pages/preformancetires.html


In my humble opinion in your case, there are only two ways to avoid rubbing--especailly if it's a 1968.

1) Go to at least a 4.25" Backspacing
2) Install P215/60/R15 tires instead

Generally speaking you can get more tire in the front of a 1969 than you can a 1967 or 1968 but you can get more tire on the back of a 1967 or 1968 than you can a 1969. FWIW In 1970 GM went to a wider front tire for the Z28's & Trans Am's

P.S. Don't just take my word on this subject, ask some others as well and get their opinions.


Good Luck!!

SSG&H aka Greg
 

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Discussion Starter #3
Crap,looks like my plans of driving my car with new wheels/tires is not happening this weekend. Rims are bought, so I may have to get the springs in on Sat and then see if they have something narrower in stock for the front ties. I was hoping to have the fronts and back fairly close in width as I want to get away from the fats and skinnies look. Was planning on 255 in back with 4.5 BS (rear shocks are moved in board and rear is custom ¨9" that is about 1/2" narrower per side.)

Also have front discs if that matters.
 

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Discussion Starter #5
Jim, to clarify the fronts are 15x7 3.75 BS, I was saying that other posts seemed to indicate that the 235 would work with 4.25 BS. So what is the next widest size I can use 215 ?
 

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I have 225-50-16's on 16x7" 3.5" backspace wheels. They cleared with drums, and they clear with wilwood 12" disks. Mine are VERY short tires, 23.5" tall, that makes a difference, but my car is also very low, 12" from the fender lip to the center of the hub.

I guess do some math comparing your ride ht and tire ht to mine. BS difference is only a 1/4". and 235's are ;ess than a half inch wider tghan my 225's.

I do think the other posts you're read are reffering to an 8", 4.25" bs wheel, that would put the center of the tire in the same place as a 7", 3 3/4" bs wheel.
 

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Discussion Starter #7
Thanks for the posts, they offered to mount the tires and if it didn´t work, bring in a different size. That just keeps me waiting but what can you do. I still have my old rims and tires to drive until they get what I need. Can´t do any measuring right now as the drag springs currently in the car keep my nose right slammed.
 

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Greg from South Side Goons & Hitmen replied to me about my problem with Torq Thrusts. The 215 60 15s fit perfectly. That would be my recommendation. He is absolutely correct.
 

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Discussion Starter #9
C n C,

What was your complete combo ? Looking to see how wide you went in back
 

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Discussion Starter #10
In case anyone is interested, I ended up with 215/65/15 up front and that worked great. Kept the overall diameter the same as the 235/60's and to be honest I dont think I'd want any wider with that rim - it would stick out to far for my taste. Used 255/60's out back and that looks good also.

Thanks again for all who posted.:)
 
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