Tyre Size vs Rim Width

[Nuke]

OK, I have decided on BFG AT's [see thread on Noise from AT's]

Size will be 30/9.50x15 with about 2" lift. I cannot go more than this because I frequently need to go under 1.75m height restrictors (which are common in the UK)

But another question : I had thought of putting them on 15x8 rims but the tyre dealer said BFG don't recommend more than a 15x7 rim for that tyre. Also, the 15x8 rims come with less backspace (3.75" compared with 4.5" for the 15x7) which puts the wheel illegally too far out. Even the 9.5 on 4.5" backspace might be marginally illegal but I don't think it will notice. (You cannot simply buy deeper flares here). A pity : I would have liked 8" rims because I like the deep dish look.

So what is the rule about maximum rim width for tyres? What is the minimum width tyre for 8" rims ? 10.5? 11.5? Is the rule that the tyre width be at least 2" more than the rim?

Academic interest really, but interesting.

[TOOLman]

When I bought my ZJ it had stock tires (225/70R15) on 15x8 rims. That was no problem. Now I run 31x10.50's on those rims, and since the backspacing is a little less than it ought to be it puts the tires a little too far out. OTOH, I don't get any rubbing on the LCA's.

Not really an answer to your question, but I thought it might be of interest anyway.

[Chris S]

You don't want the 3.5" backspacing. Your tires will hit the flares when you flex.

The 7" rims with 4.5" backspacing should be excellent. The narrower rim keeps the bead better and is less prone to rock hits.

[Yucca-man]

You mean like these 15x7 rims? These are my old 235/75R15 BFG ATs. Since then, I put 30x9.50x15 BFG AT'ko's on the same rims.

http://home.earthlink.net/~yuccaman/dec0807a.jpg

This isn't fully stuffed, but it's getting there. One reason that the manufacturers don't recommend a 15x8 on a 9.50 tire is because it's too easy to roll a tire off the rim. Not only does the 2/3 rule (rim/tire) protect the rim from damage, it reduces the possibility of rolling off the rim.

Low-profile "performance" tires usually have a rim much closer to the tire width, but the lack of sidewall helps in that case.

[Warlock]

I guess I'll be the odd-ball. I have 30x9.50 BFG MT's mounted on 15x8 AR Tailgunner style rims. Been running that setup for at least 3 years now I believe.

Now, I will say this, a 15x7 will be a better chioce for 30x9.50's. So why did I get 15x8's, you ask? Because I planned on lifting it, and putting 33's on it, and 15x8 would be the right choice. Instead I ended up giving it to my wife, and getting another which I promptly put 33's on :D

[Nuke]

You mean like these 15x7 rims?

No, like these :-

http://www.northhantstyre.co.uk/images/wheel%20photos/US%20Wheel/97modu.jpg

I have now ordered a set of these US Wheel Modular, 15x7, 4.5" backspace, with BFG 30x9.5" AT. I like the technical look of the Modular, and would not want a "directional" type because it would restrict how you could move wheels around (unless you dont mind them turning backwards). Should get them next week. I had to order the wheel centres as well - cost extra. Aim to do a lift of 1.5" or 2"this weekend ready for them.

I found only two companies in UK that import US Wheel : Bronco in Leek, Staffs, and North Hants Tyre in Fleet, Hampshire - I am buying from North Hants.

http://www.northhantstyre.co.uk

Other makes had too little backspacing (like 3.5", to make them "generic") and US Wheel seems only option in UK for the XJ, which does not have much flare outside the stock wheels. Not that I have heard anything against US Wheel. I really wanted all-black, not chrome, but North Hants said all-black was discontinued. If the chrome starts to rust despite me polishing it I shall paint them black anyway. There is a lot of salt used on roads here in winter :(