What's diff. between 285/75R16 and 33x12.5x16..

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Well that's what I want to know. I don't understand the 285/75. Not sure how that reads and what dimensions it covers. Getting new tires and I want to Upsize from 31's to 33's. Also if you could help what is the best fit size wheel for a 33? I have 15x7 on truck now, but looking at getting some new rims anyways. Would a 15x8 or 16x8 work? Or do I need bigger? Or would a 15x7 Even work. When I say work I mean Work with Safety first in mind. Thanks
 

MoJ

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It's expressed in mm. 285 is the width, 75 is the height of the sidewall expressed as a percentage of the width. There's 25.4 mm in one inch. So, here we go:
285 x .75 = 213.75
213.75 / 25.4 = 8.41 = sidewall height
8.41 x 2 = 16.82
16.82 + 16 (diamter of rim) = 32.8 = height of tire

285 / 25.4 = 11.22 inches = width of tire

So, on paper, your 285/75 R16 is 32.8 X 11.22 inches


Test on Tuesday.
 

MoJ

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crappyone said:
Well that's what I want to know. I don't understand the 285/75. Not sure how that reads and what dimensions it covers. Getting new tires and I want to Upsize from 31's to 33's. Also if you could help what is the best fit size wheel for a 33? I have 15x7 on truck now, but looking at getting some new rims anyways. Would a 15x8 or 16x8 work? Or do I need bigger? Or would a 15x7 Even work. When I say work I mean Work with Safety first in mind. Thanks

Best fit wheel for a 33? Depends on if it's a 33 for a 15 inch rim or for a 16 inch rim. For the most part when it's expressed in inches (ex. 33 x 12.50 ) it's for 15 inch rim. Any rim you have mentioned will work for a 33 inch tire. IIRC, 15 inch wheels will not fit on 93-97 LC's without some modification and providing they have the correct backspacing.
 
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So could a 33x12.5x16 work on a 15x7 Wheel? Or does it have to be 16 since it says 16? Thanks mucho for replies and math lesson.
 
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A 12.5 tire is way to wide for a 7" rim. I don't think many shops would willing mount that combo together for liability reasons, that width tire on that narrow a rim presents issues with keeping the tire on the bead. In addition to that you would get akward wear on the tire because the contact patch wouldn't be flat at a desirable pressure.

I ran 11.5 tires on 7" rims on my Tacoma and you could tell that the rims were almost too narrow.

And no you can't mount a R16 tire on a 15" rim. It must be mounted on a 16" rim. R15 tires are for 15" rims, no exceptions in this case.
 

MoJ

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reffug said:
MoJ,

love the new quote in you sig............................ :D

Heh, Shotts asked what it would cost for me to remove it. :D
 

e9999

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well, many folks think that 285s are just dandy on a 7" rim too...
 
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Critter said:
A 12.5 tire is way to wide for a 7" rim. I don't think many shops would willing mount that combo together for liability reasons, that width tire on that narrow a rim presents issues with keeping the tire on the bead. In addition to that you would get akward wear on the tire because the contact patch wouldn't be flat at a desirable pressure.

I ran 11.5 tires on 7" rims on my Tacoma and you could tell that the rims were almost too narrow.

I can't belive you'd even think that a 12.5 tire be to wide for a 7" wheel. I have run a mickey thompson 32x12.5 (bias ply) and now a 31x12.5 xterrain (steel radial) on the stock toyota 15x7 wheels. They have held the bead at 5 psi. I have always mounted my own tires and a 12.5 tire mounts just fine on a 7" wheel, the tire does not show any hint of being too wide for the wheel when mounting. Even when aired up the sidewalls don't stress. The only thing is the tire looks smaller than if it was mounted on a 8" or 10" wheel. You also get tons of protection fron hitting the rim of the wheel while aired down.
I'm always paranoid about the rims on my fzj80 with the 12.5" tire on the 8" wheels, not enough sidewall sticking out to protect it. I want to go to a 13.5 or 14.5 bias ply (they bulge on the sides, it's a bias ply thing) on there.

Here's some pics of my trucks tires. I belive the xterrain was at 10psi.
 
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Critter said:
A 12.5 tire is way to wide for a 7" rim. I don't think many shops would willing mount that combo together for liability reasons, that width tire on that narrow a rim presents issues with keeping the tire on the bead.

This is wrong. Wide tire on a narrow wheel makes it harder to lose a bead. More pressure pushing on the bead. I ran 12.50's on a 7" wheel and it was great...almost like bead locks, almost.
 

e9999

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bah, these things are soft...
Asked a bit back about the side to side width of 285 MTRs on a 8" and there was less than a 1/2" difference with my 7" rims IIRC.
I doubt there is any meaningful difference in visible size...
 
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Cool. I might just keep Stock rims then. I'm not gonna have enough cash to get 5 rims and 5 33's. Was just gonna do the 4 new rims and 4 31's since my spare is a 31. Which brings me to my Next question. When I get the 33's, will the Spare still beable to Fit Underneath? ALSO, Would it matter what tire I'm mounting on a 15x7 rim? Not sure if it would just checking for future reference. Thanks a bunch and sorry for all the newbish questions.
 
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crappyone said:
When I get the 33's, will the Spare still beable to Fit Underneath? ALSO, Would it matter what tire I'm mounting on a 15x7 rim? Not sure if it would just checking for future reference.

The 33" tire will fit fine in the stock spare location, as I recall some have cramed 35" tires under there.

What do you mean by what tire? like brand or somthing?
 

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