[mwritter]

I've spent hours studying the forums over the last few days as I prepare to order some new wheels and tires for my '65. Because of my Baer brakes and lowering springs, etc., I am going to have to be dead-on with tire size and backspacing. While searching, I was amazed at the number of threads asking the same questions again and again. So I began to cut-and-paste from other backspacing/wheel/tire threads into a word document for my own future reference. I also went through many emails I had from other 64/65 GTO owners on the subject.

I thought maybe if I posted all that information in one place, it would save others in my situation a lot of time. Plus, anyone else who's setup isn't mentioned can post what worked for them, and we can keep it all in one place. If anyone sees one of their posts and would like to make a clarification/correction, let me know and I will edit this original post.

Disclaimer: any gramatical errors were in the original post! I tried to proofread and clarify what I could. Here goes.


I have a 65 (but identical to 64). I have 235/45/17 on front and 255/50/17 on rear . Wheels are 17X8 with 4.5" backspacing all the way around. If I were to do it again I would go with 5" of backspacing on the rear, had to roll quarter lip slightly to fit.


I went with Torque Thrust II's on mine. 16x8 on all four corners with a 4.75 backspacing. I also went what some would consider conservative on the tire sizing. 235/60x16 in the rear to get the stock 27.1 diameter. 215/55x16 on the fronts. The additional height was not wanted, and larger tires would have hit when turning. I also added Hotchkiss lowered coils with an additional 1/2 coil removed. I have plenty of clearance on turns, and in the rear wheel wells. Just about 1/2 inch on the inside and outside.


Here's a shot of my own '64 Tempest that rolls on 17X8" rims (4-1/2" backspace) shod with 235/45-17s.


Torq Thrust IIs 17X8. 4.75" Backspacing. 235/45/17 tires all around.


I have 15X8 w/ 4.75 backspace and 275-60-15s on the rear of my 65 (same body as 64s) and they are tight - have about 1/2 inch clearance to the fenderlip and about 3/4" between the tire and frame on the inside. Tight but it doesn't rub!


I've got a newer 12 bolt (1" wider) in my 65 and went with a 15 x 8 with 5.25 backspacing for the rear. Didn't think a 275 would fit without rolling the lip so went with a 255 width.


If you have the original rear you should run P275/60R15's on a 15x8 rim with a 4 1/2" backspacing. If you are running a later year rear end you can run the same tires but use a 5" backspacing because the overall width of later rears are wider. I'm running P275/60R15's on the back of my 65 that has a later 69ish rear. I'm using a 15x8 rim with a 4 1/2" backspacing and 0ne side just touches the inside lip of the wheel opening slightly. If I had a 5" backspace they wouldn't touch at all.


I am having similar rubbing problems with 17x8 (4.5" BS) wheels on my '65 Lemans. Tires (245/45) rub on rear lower lip of the front fenders, and a little on the upper lip when the suspension compresses.


15x8" front & rear. 4.5" backspacing front - 4.75" backspacing rear. 235-60x15 front, 255-60x15 rear. (275-60x15 should work in the rear with 5" backspacing).


Boyd 16X8 with 5 1/8", 245/50-16 front and rear, and 255 may fit.


Rear Axle on my 65 GTO (from a '65 Chevelle 12-bolt) is 60 inches wide measured from the outboard edge of flange to flange. My 15x8 wheels use 5 inch backspacing to center a 275x60x15 nicely in the wheel well.


I run a set of 235/45-17s on 8" wide wheels all around on a '64 Tempest (same wheelwells as a '65). The wheels have a 4-1/2" backspace and sit a bit towards the outside of the wheelwells for a wider stance. I know 245/45-17s would fit in back, up front they would probably interfere a bit on the outer part of the inner fender near the fender lip on big bumps. I am running a stock width rear axle.


To better center the rear wheels in the wells a 5" backspace would be ideal. I think you could use a 255/40-18 and have a good fit on the 18X8" wheel with a 5" backspace. Up front if you want to use a 17X7" wheel a 4-1/2" backspace would be close to ideal, a 235/45-17 tire would be a good fit. If you decide to use a 17X8" up front you could use a 5" backspace and tuck a 245/45-17 in there.


17x8 wheels with 4.5" backspacing WILL rub on a 65 if you have 245/45-17 tires on the front. B-man is right--a 5" backspace on the front would do the trick. I have the same tires with 4.5" backspace on the rear and there's plenty of room.


I have 17x8 on the front, 5.25" BS, 245/45-17. On the rear are 17x9.5, 5.75" BS, 275/40-17. This is a 65 Lemans, no alterations whatsoever on the wheelwells. I do have Baer brakes front and rear which push the wheel mounting flange out about 1/4," so subtract 1/4" from the backspacing numbers if you have stock brakes. This wheel combo looks and performs fantastic! I didn't think I could get so much tire in back, but a friend clued me into the correct backspacing, and it's available as a custom order on the American Racing TT2.


I ended up with 235/60/15 front, and 245/60/15 out back on rims with 4 3/4 backspacing. The fronts fit nice with no rubbing and a nice diameter, the back also looks great, nice width. If you really want all 4 the same then 235/60/15 tires are the way to go.


No rubbing at all with 9” wide 18” rims. Once had 9.5” wide rims and they JUST cleared. That is the max with a 255/45/18 tire. With 17s, you can run 8” wide with 4.75” backspacing all the way around and then be able to rotate the tires. Use 245/45 all the way around or go 50 series in the rear. Out back, a 9” wide 17” rim with 5” backspacing should be okay with a 245/45/17.


The fronts are 8" wide w/ 5" backspacing with 245/40 -8 tires (could use 4.75" b/s and would be ideal). The rears are 9" wide with 5.10" backspacing and 255/45 -18" tires. Also, rim backspacing depends on your rearend width (64-66 year width or a later on which is 1" wider) and if you have disc brakes. I am also doing a 65 GTO with 4 wheel discs & Hotchkis springs but may have to use 2" dropped front spindles to get it to sit like the Tempest. The rims are the same width but the rear rims have 5.20" backspacing.


17" Torque Thrust II's - 8" wide rims up front and 9.5" rims at rear. The rear rims are special order from AR with 5.875" backspacing and the fronts are off-the-shelf, but I had to get them backspaced further as the tires rubbed. Tires are 275's out back and 245's up front.

[Mr_GTO]

I am bowing down to you! Thanks. Great info should work with my '66 too.

[David Jones]

Will you do that for my 69? If you don't, I'll start a new "what size" thread.
I will. Promise.

[Northern Goat]

Sure. You do this AFTER I go to all the lengths to figure it out for myself. BTW, don't forget that if you use lowering spindles, you can not use more than 4.5" BS or tie rod end will touch the wheel. Great list, WTG.

[gearbanger]

Northern goat, I assume you are talking about 14" or 15" wheels on that 4.5" backspace thing?

Dude I saw your car on the protouring forum, It is unreal!!!!!!!!!!!!!!!!!!

[Northern Goat]

I am running 17's and lowering spindles, only have room for 4.5" you would have to go to a 20 or 22 to get away from this problem.

BTW, saw you ride on PT, very nice.

[bullheimer]

i have 17x8 "off the shelf"??? TT2's i like that. that's about what they told me at the store. std BS whatever the hell that was. i have 255s all around and no rubbing anywhere. all stock steering. i did have a super FAT chick ride shotgun once and my wife (her daughter) hit a dip making a left turn and it bent out my pass side fender lip, but it was a very easy fix for my body shop, he didnt even charge me as it took him five minutes. lucky me! also, my springs are original too and i'm sure they sag, so with newer ones i probably wouldnt have hit my fender. we are talking about 250 lbs minimum here, too.

i should say tho that with the 255s in front my car gets tossed around like a rag doll in the I-5 ruts. it sucks. if you search rag doll you will find my posts
and i should ALSO say that i ran air shocks in the rear and that i did get very very slight rubbing with the air down