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Author Topic:   GR70X15 equals WHAT?
Davewil
unregistered
posted April 25, 2001 02:50 PM           Edit/Delete Message Reply w/Quote
I am looking for replacement tires for my 1974 Trans Am with GR70X15 tires. What is the equivalent new tire size? 235R7015???
If I want to go to a 60 Series tire what size would provide a tire of the same diameter?

THANKS

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Ryan
unregistered
posted April 25, 2001 03:22 PM           Edit/Delete Message Reply w/Quote
I don't know what size GR70X15 is, but the calculator below should help once you can indeed determine that. http://www.ring-pinion.com/RPMCalculator.html

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GregZ
unregistered
posted April 26, 2001 11:20 AM           Edit/Delete Message Reply w/Quote
I forget now, the older system of tire ratings for width /aspect ratio used some combination of letters and numbers, didn't they...?! I think yours is a 'G' width, 'R' simply for 'radial' 70 series aspect ratio and of course 15" rim.... I took a quick look at tirerack.com and for the '74 Pontiac 'Firebird' the OE tire is a P225-70R15 -no other Pontiacs listed. I'm sure they could help you with an equivalent to a 'G' series

quote:
Originally posted by Davewil:
I am looking for replacement tires for my 1974 Trans Am with GR70X15 tires. What is the equivalent new tire size? 235R7015???
If I want to go to a 60 Series tire what size would provide a tire of the same diameter?

THANKS


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DaveB
unregistered
posted April 28, 2001 02:50 AM           Edit/Delete Message Reply w/Quote
If I remember correctly I think it is a P205/70r15. G's were 205, H's were 215 and L's were 235.

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Mark
unregistered
posted May 01, 2001 02:39 PM           Edit/Delete Message Reply w/Quote
The equivalent size to the GR70-15 would be P225/70R15 - almost identical in O.D. but slightly wider O.W. than the 'G'(0.3"). The best match in 60 series would be the P265/60R15 - approx. 0.1" taller in O.D., but about 1.7" wider. You may want to check your wheels, though, the minimum width for
the P265 is 7.5". The minimum for the P225 is 6.0". While you are at it, make sure the wheels are radial approved - some early cars with bias tires at OE are not.

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