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Discussion Starter · #1 ·
Hi guys. I had a set of rims made for my Nova by Cragar with alot of offset. The rims are 15x8 with 5.75 inch offset so they tuck way up in my fender ( most of you know what I mean where I didnt have much room on the side of the tire towards the fender, but I had alot of room on the opposite side of the tire towards the shock). Well i put the new rims on and they work beautifully and I am able to fit 26/10/15 mickey thompson drag slicks on my stock width rear end with only a litle grinding to my shock mount and no rubbing. My question is this: Is there some way to convert 26/10/15 to a street tire size? LIke 245/60/15 or whatever. Im trying to get as close to 26/10/15 as possible because everything just fits so perfect, but I dont know how to convert the 26/10/15 into the other tire sizes (metric??).
Any help you guys can give is appreciated as always.

Rob
 

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The first # 245 is metric. divide by 25.4 (millimeters) to get inches

245/25.4 = 9.6" wide

Second # is the % of side wall height to tire width for the whole tire cross section.

BUT that's not measured inflated on a car or the tire construction (2 belts-4 belts-bias ply-radial)

Best to e-mail MT and get the spec's on your tires.

With as much offset as you have, unless the suspension is designed for it, my guess, 10,000 miles and you will be buying more new tires
 

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red65mustang said:

With as much offset as you have, unless the suspension is designed for it, my guess, 10,000 miles and you will be buying more new tires

WHY....?

What would the offset have to do with tire wear?
 

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The folks at Coker Tire were very helpful in changing my L60-15's to standard metric sizes. You can drop them an e-mail with your question and they are prompt to reply. I'd still measure though because we have found that the tread width does vary some between brands of the the same nominally sized tire. If you are cutting it close, this might matter.
 

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reply to Poncho62

Because the centerline of the street tire is so far off the centerline of the rim.

Every time he makes a left turn goes around a left curve in the road, the left rear outside tire edge is going to get way more weight load than it was designed for and scrub/wear the edge . Same for right turns, right rear outside edge.

Independent rear suspension (Corvette?, Porshe?) , big offset, no problem, it was designed to compensate for the off center tire. And the "correct" tires are $$$ to try to work with the offset wheel.

Solid axle with leafs or coils, "somethings" got to give when you turn a corner.

"Plan B" turn corners real slow......30,000 miles?

"Plan C", shorten the axles and buy wheels with less offset so the rim centerline and tire centerline are closer.
 

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Discussion Starter · #7 ·
Thanks for the reply guys. In my previous post I meant 5.75 inches of backspacing, not offset. I thought they were the same thing but I guess they are not reading from the other posts. Well thats for the conversion. Seems as either 245/60s will be the tire I need. Thanks again.
 

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4.75" backspace isn't that far from centerline on an 8" rim. Thats a +6 offset, same as the 3.75" backspace on the 6" rims they put on some at the factory.
You might get some excess wear, but I had a 5"backspace on the rear of mine with no problems for 20,000miles before I changed wheels again. Tires still looked fine. On the front, at least on the older ones, just changing from OE drum to OE 2pc disc pushes the centerline outward 1/2"... but then I think they used a 7" w/ 4" BS, 0 offset...

Time will tell.
 

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If you want to go inches to metric

divide by .0397 (a meter is 39.7")

10" wide tire/.0397 = 251 millimeters wide

for me, easiest way to remember and convert back and forth, 100 millimeters is darn close to 4"

A small caustion.

Make sure your axle bearings are in good shape if you are planning to drive alot of miles.

big wheel offset = tire wear

big wheel backspacing = axle bearing wear

by clarifying it's 5.75" back space on a 8" rim, you just moved the "way more load" to the bearings, it didn't go away.

Tires will last longer, axle bearing life "not so good"
 

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You sure about that Red?

I was always told that wheels with LESS backspacing were harder on bearings, because of the leverage caused by having the tire farther away from the bearing.

Unless I'm reading wrong, his wheels have MORE backspacing, to tuck the tires in farther.

If what you are saying is correct, then all newer vehicles, with negative offset wheels, show be h*ll on bearings.

Just checking, to help y'all out, or learn someting new.
 

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I would think either way would place undo stress on the bearings or the tires, if it is too far from stock design. But I also thought that if the rim stuck way out, it was worse for suspension/bearings than inward. That is just hearsay though, but it seems plausible, even if based soley on the idiotic look of stik-out rims ;).
Of course the wider the rim, the more backspacing you can have on some models, but offset should still stay close to the same.

I also always thoght negative offset put the rim farther out... negative being the relationship of the mounting flange to the ring, with the flange being farther inward (negative) from the outer edge of the rim... so an 8" rim with a 5.75" backspace would have a severe positive offset.

offset chart

Apparently, this is the same way the Society of Automotive Engineers defines offset... backwards from what is commonly thought. (relationship of flange to ring, rather than ring to car)
http://www.bacomatic.org/~dw/offset.htm
 

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To packratwrecker

No I'm not sure, but as yesgo's chart shows he's almost off the chart for leverage. "Somethings gotta give".

Fact is he almost doubled the backspacing from what the axle was desgned for, so I say "be careful-be safe".

I think this is probably more correct:
a small caution, with 5.75 back spacing on a 8" wheel inspect the wheels inside and outside often for stress cracks caused by hitting a nasty hole while driving around a curve.

"Plan C" was my best advice, shorten the axles and lose some back spacing.

"Plan D" can help , add a 5/8-3/4" sway bar to transfer some of the load on curves, possibly better to use rubber bushings to absorb more shock from a RR track/pothole/?.

Probably the most important cautions are: Check how your brakes react to the 10" tires, adjust the front/rear bias.
ALWAYS be aware your driving on 10" wide water skis, a bump and a slick spot on a curve, the rear end WILL BREAK LOOSE.
 

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10 x 25.4= 254(call it 255)

255 x 50% = 127.5 + 127.5= 255 / 25.4 = 10 + 15= 25"

255 x 60% = 153 + 153 = 306 / 25.4 = 12 + 15 = 27"

so if you run a 255/60/15 it is 10x27x15"
or
if you run a 255/50/15 it is 10x25x15"

Each manufacture is different but that will give you a base line.
 
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