tyre/rim size compatibility

Submitted: Friday, Feb 03, 2006 at 10:07
ThreadID: 30375 Views:4446 Replies:2 FollowUps:2
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Hi all,
I'm in the market for some new rubber and was checking out the BFG website which has a tyre size guide. For the AT's it states that 235/70/16's should run on a minimum rim width of 6", optimum of 7", and maximum of 8". For 235/85/16's it is 6, 6.5 and 7 which is also what they recommend for the 235/75/15's. I do not understand why there is an inch difference in the recommended maximum rim width between the 70's and the 85's which are the same width just different profiles.
Now I'm worried because I'm currently running the 85's on 8" Sunraysias. Is this dangerous?
Also if this is the case, it seems I'll need wider tyres than I have but they already stick out from the vehicle about 10-15mm and I really don't want to put flares on my standard 80 series and change it's looks (I know, beauty is in the eye of the beholder) which means I'll need to change the wheels as well.
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Reply By: Vivid Adventures - Friday, Feb 03, 2006 at 10:30

Friday, Feb 03, 2006 at 10:30
It's surprising that someone would fit tyres to a rim that didn't support them!

Usually tyre jockeys get this right.

It's the tread width, not the wheel width that is the same BTW.

Ciao for now
AnswerID: 152691

Follow Up By: Member - Bware - Friday, Feb 03, 2006 at 11:27

Friday, Feb 03, 2006 at 11:27
Hi Vivid,
Yeah, I bought these tyres on these rims 2nd hand. I assumed they would have matched.
FollowupID: 406428

Reply By: desert - Friday, Feb 03, 2006 at 11:21

Friday, Feb 03, 2006 at 11:21
The 85 section tyre has more flex in the sidewall, which allows it to flex out to the wider rim. But a 7 inch rim is ideal for it as it will allow correct shoulder contact with the road, has less offset past the hub and is the most "fitable" rim for most tyres that you buy in remote places. In comparison, few tyres are carried that fit an 8 inch rim. Apart from the main city centres.
AnswerID: 152703

Follow Up By: Member - Bware - Friday, Feb 03, 2006 at 11:42

Friday, Feb 03, 2006 at 11:42
Good points Desert. Maybe I'll invest in a set of 7" rims.
FollowupID: 406429

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