P275 60 4 1/2 backspace.

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P275 60 4 1/2 backspace.

Post by 73ss on Mon May 02, 2016 7:38 pm

I see several of you have had no problems fitting a P275/60. Does anyone have them with a 4 1/2" backspace? I scored a nice set of weld draglites, 8" wide, 4 1/2" backspace. I'm looking at getting MT P275/60 drag radials to mount but am not sure about the backspace. I have checked several used tire shops for a old 275/60 to mount and see if everything fits but cannot find one. 15 inch tires are just not common anymore. I currently have a 4 inch backspace, P235/70. Plenty of room with that setup. Thanks for any help.
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Re: P275 60 4 1/2 backspace.

Post by Joe73 on Mon May 02, 2016 8:27 pm

I've been searching the same thing. I have some 15x10 4 1/2" backspace centerlines and they wont work on my car. I'll be going with some 15x8.5 with 4 7/8" backspace.

The 275/60 drag radials are usually 28" wide with an 11 inch section width. The section width is what you have to be careful about.

It will be close the wheel well but you will have plenty of room on the frame side. It might work. Those 275/60 usually have a 9" tread. So if your able to put your rim on the car without a tire, put a block of wood under the rim and lower the car, you can measure how far the rim edge will be from the wheel well. Since the 275 has the 11" section, you will need 1 1/2 inches from the edge of the rim to the wheel well. And then at least another 1/2 inch for clearance. So 2 inches from the edge of the rim to the wheel well and you should be good.
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Re: P275 60 4 1/2 backspace.

Post by 73ss on Mon May 02, 2016 8:55 pm

Great idea Joe. I'll try that. I was more concerned with the frame side. I have about 2 1/2" there now with the 4" backspace, 235/70. Are you going with the 15x8.5     4 7/8" backspace with a p275? Seems like that would be cutting it close to the frame?
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Re: P275 60 4 1/2 backspace.

Post by Limey SE on Mon May 02, 2016 8:56 pm

73ss wrote:I see several of you have had no problems fitting a P275/60. Does anyone have them with a 4 1/2" backspace? I scored a nice set of weld draglites, 8" wide, 4 1/2" backspace. I'm looking at getting MT P275/60 drag radials to mount but am not sure about the backspace. I have checked several used tire shops for a old 275/60 to mount and see if everything fits but cannot find one. 15 inch tires are just not common anymore. I currently have a 4 inch backspace, P235/70. Plenty of room with that setup. Thanks for any help.

Get With John Murtaugh aka Dynchel he is in Mentor Ohio and works at a tire shop he just put 295/50 on the back and Might have a 275/60 around fer ya if you give him some notice

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Re: P275 60 4 1/2 backspace.

Post by Limey SE on Mon May 02, 2016 8:57 pm

if needed you already know the tire width I can measure my 8.5 with a 235/60 on if need be

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Re: P275 60 4 1/2 backspace.

Post by 73ss on Mon May 02, 2016 9:19 pm

Thanks Limey!!  I'm in the mentor area once a month or so for work.
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Re: P275 60 4 1/2 backspace.

Post by Limey SE on Mon May 02, 2016 9:32 pm

if on Facebook look him up prob faster than here

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Re: P275 60 4 1/2 backspace.

Post by alowerlevel on Mon May 02, 2016 11:13 pm

Yep 275/60s on a 15x8 w/4.5"bs will fit with room to spare.  I had 275 DRs on my '73 for a bit as rollers, and now have the regular 275s off my 67 on it, lemme see if I have any pics......


Found some pics of it with the old BFG DRs on it (which are wider than the regular 275 BFGs)



Crap cell shot of inside of tire to frame


Will just clear stock fenderlips
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Re: P275 60 4 1/2 backspace.

Post by bracketchev1221 on Tue May 03, 2016 7:40 am

A 4.5" bs wheel will work for an 8" wheel. If you want to use a 10" rim the bs will have to be 5.5 to keep the wheel in the same location.
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Re: P275 60 4 1/2 backspace.

Post by SSTOOLMAN on Tue May 03, 2016 10:20 am

My 275/60's w/8" 4.5"BS fit great.
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Re: P275 60 4 1/2 backspace.

Post by Joe73 on Tue May 03, 2016 11:55 am

I'm really glad this thread was brought up.  I've been running tires sizes for about 2 weeks now.  And yes, the 15" tire sizes are real scarce.  The only choice I've found to fit my bill are the Mickey Thompson sportsman s/r.  They come in a 28 diam.  12.1 section with a 10.4 tread.  But that was measured on a 10 inch rim.    http://www.summitracing.com/parts/mtt-6641/overview/

So by my going with a 8.5 rim, it will narrow the section width just a bit.  I'd love to stay with an 11" tread that I've had forever but the section widths get too wide when going with radials.

I'm not really a fan of the s/r tread pattern and they are just a street tire with average "bite"

The other tire I'm looking at is a 275/60-15 Nitto555R.  Its 27.76 dia.  11" section with only a 8.5" tread although some sites say its a 9" tread.  I really like this tire because it has a tread wear rating of 100 unlike other drag radials that have a rating of "0" or "00".  It wouldnt concern automatic guys, but everything I've read says that manual cars should stick to bias ply tires.  This have to do with the "shock" of dumping the clutch as opposed to power braking or using a trans brake, both of which preload the driveline and minimize shock.

I'd like to thank "alowerlevel" for posting those pics of the 275/60 on an 8" rim.  Very helpful with my decision.  That size tire looks real good.  I just wish they made them 10" wide at least.
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Re: P275 60 4 1/2 backspace.

Post by Limey SE on Tue May 03, 2016 11:59 am

hey Silly man Joe them Turbine on the Black car had 8" wide turbines with a 275 60 on rear geezz LOL

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Re: P275 60 4 1/2 backspace.

Post by Joe73 on Tue May 03, 2016 12:36 pm

Theres no doubt that 275/60 will fit with pretty much any rim just with the proper backspace. I'm going with a 8.5" rim with 4 7/8" backspace so the tire will be centered in the wheel well. And I can go with a bigger size if I like.

The 275/60 is a good looking size tire but I'd like a little wider. At least 10" would be nice. But I'd like to stay close to the 28" diameter. I'm doing this not only for looks but moving up from my 26" diameter 50 series tires will adjust my rear gear ratio (4.10) a bit. If I remember correctly, and this is an approximation, every inch bigger in diameter decreases your effective gear ratio by one size. And most rear gears are based on a 26" tire. For example, if you have a 3.73 rear with 26" tires your good. But 3.73 with 27" tires will be like having 3.42 gears. Then 3.72 with 28" tires will be like having 3.23 gears. Thats why speedo adjustments need to be made with gear swaps and some tire diameter changes. Most tire companies list revolutions per mile with their tire sizes. I like to look at that as well cause it gives you an idea of how far off you will be.
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Re: P275 60 4 1/2 backspace.

Post by Limey SE on Tue May 03, 2016 1:09 pm

Joe73 wrote: Most tire companies list revolutions per mile with their tire sizes.  I like to look at that as well cause it gives you an idea of how far off you will be.  

http://www.g3gm.com/t1542-tire-size-calculator?highlight=tire+calculator

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Re: P275 60 4 1/2 backspace.

Post by alowerlevel on Tue May 03, 2016 5:08 pm

Joe73 wrote:Theres no doubt that 275/60 will fit with pretty much any rim just with the proper backspace.  I'm going with a 8.5" rim with 4 7/8" backspace so the tire will be centered in the wheel well.  And I can go with a bigger size if I like.  

The 275/60 is a good looking size tire but I'd like a little wider.  At least 10" would be nice.  But I'd like to stay close to the 28" diameter.  I'm doing this not only for looks but moving up from my 26" diameter 50 series tires will adjust my rear gear ratio (4.10) a bit.  If I remember correctly, and this is an approximation, every inch bigger in diameter decreases your effective gear ratio by one size.  And most rear gears are based on a 26" tire.  For example, if you have a 3.73 rear with 26" tires your good.  But 3.73 with 27" tires will be like having 3.42 gears.  Then 3.72 with 28" tires will be like having 3.23 gears.  Thats why speedo adjustments need to be made with gear swaps and some tire diameter changes.  Most tire companies list revolutions per mile with their tire sizes.  I like to look at that as well cause it gives you an idea of how far off you will be.  

M/T has a 295/55 DR, http://www.jegs.com/i/Mickey-Thompson/672/3454/10002/-1?parentProductId=3410349
I like to use this site to see what the difference will be from different wheels/tires and how they compare to your existing setup https://www.rimsntires.com/specspro.jsp
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Re: P275 60 4 1/2 backspace.

Post by 73ss on Tue May 03, 2016 5:42 pm

Thanks for all of the info. It is my understanding that a drag radial will not grow or balloon like a drag slick on the top end? alowerlevel, if that was a drag slick shown in the pic with the tape i would be worried it would grow on the top end and rub. Years ago I had MT 26x10 slicks and they would grow and rub the tail pipes on the top end. Had about 1/2 clearance sitting still.
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Re: P275 60 4 1/2 backspace.

Post by Joe73 on Tue May 03, 2016 5:53 pm

Yes, a radial will not grow. A bias ply will. I think alowerlevel's tire is a bfgoodrich drag radial.
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Re: P275 60 4 1/2 backspace.

Post by alowerlevel on Wed May 04, 2016 12:44 am

Joe73 wrote: I think alowerlevel's tire is a bfgoodrich drag radial.
Yep the ones in those pics were old BFG drag radials which are about 1/2" wider than the regular non-drag radial BFGs.

Joe73 wrote:The other tire I'm looking at is a 275/60-15 Nitto555R. .
Just an FYI, Nitto DRs tend to run on the narrow side of things.  Like a Nitto 555r in 275/60 will be about the same width as a 255 from M/T.   The 555r's still work well, but its just something to be aware of.

Heres an example (not mine) of 275/40/17 MTs vs 275/40/17 555rs


Last edited by alowerlevel on Wed May 04, 2016 1:07 am; edited 5 times in total
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Re: P275 60 4 1/2 backspace.

Post by alowerlevel on Wed May 04, 2016 12:53 am

73ss wrote:Thanks for all of the info. It is my understanding that a drag radial will not grow or balloon like a drag slick on the top end? alowerlevel, if that was a drag slick shown in the pic with the tape i would be worried it would grow on the top end and rub. Years ago I had MT 26x10 slicks and they would grow and rub the tail pipes on the top end. Had about 1/2 clearance sitting still.

The angle of the pic makes it look alittle closer to the fenderlip than it really is, there was about 3/8" of clearance there.

Yes a DR will grow some, a 275/60 wont grow as much as the larger sizes (295/65 or 315/60) but it will still have some growth.

You can see in this vid how much a 295/65 (30" tall) will grow (about 1" @ 165mph according to the description)
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Re: P275 60 4 1/2 backspace.

Post by dynchel on Wed May 04, 2016 7:08 am

295/50/15 mastercraft avenger g/t on 15/8.5 ansen sprints.
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Re: P275 60 4 1/2 backspace.

Post by alowerlevel on Wed May 04, 2016 11:55 pm

Here ya go I grabbed a couple quick shots earlier tonite of the regular BFG 275/60s on 15x8s w/4.5"bs, you can see how they are not as wide as the drag radials were.



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Re: P275 60 4 1/2 backspace.

Post by 73ss on Thu May 05, 2016 8:34 pm

Thanks for all of the input. You mount em, you bought em. That looks like a big difference between a regular TA & a DR. alowerlevel, would you be comfortable running the DR's with the clearance shown in the pic? considering a small amount of growth?
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Re: P275 60 4 1/2 backspace.

Post by alowerlevel on Thu May 05, 2016 10:50 pm

73ss wrote:Thanks for all of the input. You mount em, you bought em. That looks like a big difference between a regular TA & a DR. alowerlevel, would you be comfortable running the DR's with the clearance shown in the pic? considering a small amount of growth?

Yea I would have run them without a 2nd thought, and even if they did grow some they would also get slightly narrower as well so no worries there.
My plan is to eventually stuff 295/55s on 15x10s in there, if my measurements are right they should fit with minimal cutting to the fender lip.
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Re: P275 60 4 1/2 backspace.

Post by 73ss on Sat May 28, 2016 7:57 pm

I had a look at a 87 Buick GN today and the owner had 275/60/15 BFG drag radials on. 8" rim. 1/2 spacer, not sure of backspacing. There is enough room between the frame & tire to slide your hand in. It does rub on the top end though, just enough to clean the dirt off the frame. Owner has been running it that way for years with no problems. Those cars (G4's ?) have less room than our G3's. Car runs 9.90 et's. The owner is the guy who built my transmission.
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Re: P275 60 4 1/2 backspace.

Post by 73ss on Mon Dec 12, 2016 7:02 pm

I finally got the wheel /tires installed in Oct. Everything fit with room to spare. MT 275/60 SS Drag radials. I didn't think to take any pics. Car is up for the winter now. The car now hooks, for the most part. I haven't found the sweet spot for air pressure and I need to do some suspension tweaks.
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Re: P275 60 4 1/2 backspace.

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