another wheel fitment Q

Fitting oversize tires, raising and lowering, suspension modifications...

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paintballrocker
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another wheel fitment Q

Post by paintballrocker »

i finally have the extra cash to get new wheels like ive been wanting. right now i have a tbarcrank/add a lead lift and 30x9.5 tire on stock wheels. the new wheels im looking at are 15x8 with 5" of backspacing. do you think i can fit these wheels with little to no rubbing?
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HenryJ
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Re: another wheel fitment Q

Post by HenryJ »

HenryJ wrote:Put a tire up on the curb and turn the wheel to where the corner of the sidewall comes closest to the rear of the front fender. Take a measurement. How much room do you have? Do the same on the other side and let us know what you find.
HenryJ wrote:The main concern will be rubbing the back of the front fender.

With the stock tires and wheels still on , I'd park with one front tire up on a curb, the turn the wheel to where it is closest to the back fender. Use a white crayon, welders pencil or something to make a mark on the tires sidewall 1" from the edge of the rim. (this is about where the bead would be on the 18" rim) Lay a yard stick across the tires side wall and measure from your mark to the closest point on the fender. You may have to have someone turn the wheel to get it to a point where everything lines up.

Ok, now you have the maximum size of the space available, and by measuring from the sidewall of the narrower tires , you have approximated the corner of the wider tire at the closest point. Take that measurement and subtract 1" for clearance, and you have the maximum sidewall.

Now if you understand how the tire sizing works you can calculate the size tire you want.

Example:

9" rim and want 9" tread width for the front . 235 (mm) comes to 9.25 inches so that size is pretty close, next we need to find which profile would give us the diameter we want.

Let's say that your measurement above was 7" minus 1" for clearance, equals 6" total sidewall. All we need now is what percentage of 9.25" comes the closest without exceeding 6".

5.55" is 60% of 9.25", So a 235-60R18 should work.

Now that the tire size has been calculated for the front what is the diameter? The sidewall is 60% of the tread width right? 5.55"

So, 5.55"+18"+5.55"=29.1"

Now since it is a 4x4 and we want a wider tire on the rear we will have to stay with that 5.5" side wall, so we figure from the reverse what percentage and tread width with a 5.55" (140mm) sidewall?

Let's try some 50's and see how wide it would be. (5.5") 140mm = 50% of 280mm which is an 11" wide tire. That might work? 280-50R18 but is that size available? 255-55R18 is the same diameter and a 315-45R18 is pretty close too.

Once you know what the max. for the front is you can play around with sizes to find the combination you want.

The calculators on the Crew Cab website are pretty handy for some quick calculations.
The problem lies in what tire sizes are common and affordable you may have to adjust down a bit to find the right combination.

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Re: another wheel fitment Q

Post by paintballrocker »

THanks HJ, I measured and have 1.5" from the closest point of the wheel to the fender edge. Is that enough clearence for a 15x8 with 5" bs?
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Re: another wheel fitment Q

Post by HenryJ »

You will lose a little over half what you have with those tires. That still leaves you almost 3/4". If you go with a little bigger tire you will lose the rest.
I'd say it sounds like they will be close , but probably work.
The extra inch of rim width does not all add into a loss of clearance as the tire side wall absorbs some of that difference. You do lose clearance, but not quite half the added width. That helps you in this case.

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Re: another wheel fitment Q

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paintballrocker wrote:THanks HJ, I measured and have 1.5" from the closest point of the wheel to the fender edge. Is that enough clearence for a 15x8 with 5" bs?
Is this the measurement with a tire angled up on a curb?
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Re: another wheel fitment Q

Post by paintballrocker »

yea the 1.5" of space is with a tire up on a curb, on flat ground i have 2"+ of space. now im gona stick with my 30x9.5's because they only have 10k on them. So HJ correct me if im misunderstanding, but with going to the 15x8 wheel with 5" BS ill lose over half of the 1.5" of clearence? if so thats fine with me. i was just afriad of it rubbing really bad
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Re: another wheel fitment Q

Post by HenryJ »

I have no doubt that you can make it rub if you try. I do know that more than a few have run 4.75" rear spacing and an 8" wheel.
You will be fine after a body lift. A mall crawler might get by without though.

My optional offroad tires on the stock wheels would rub under hard articulation. Less rearspacing and bigger tires mean you will rub more than I did, unless you get a body lift, or are a cautious driver.

I'd wager that you will rub. How bad and how much it bothers you, is up to you.

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Re: another wheel fitment Q

Post by paintballrocker »

looks like ill have to push the wheel idea back now again. my tranny just started slipping today really bad, had to limp it home
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