235/85 tyres low PSI in sand. 7" or 8" wide wheels?

Submitted: Monday, Feb 05, 2018 at 12:12
ThreadID: 136218 Views:1091 Replies:8 FollowUps:1
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Good Morning.

I picked up some new 235/85R16 all terrains on the weekend. I've purchased them for a planned Simpson crossing in June so tyre pressures will be between 10 and 20 PSI on that journey.

I've read conflicting information regarding the 'ideal' wheel width for these tyres. I feel like some references may be for road cars that run road pressures. Here is one such example:

Min / Ideal / Max
7 inch: 195mm / 205mm or 215mm / 225mm
8 inch: 215mm / 225mm or 235mm / 245mm

http://www.tyresizecalculator.com/charts/tire-width-for-a-wheel-rim-size-chart

I've read some people say they wouldn't get in the car with a friend if they ran 235/85 tyres on 8" wide rims due to the danger of the bead coming off the wheel. I'm not sure if this was a low PSI reference.

Is there a general consensus on this? 7.5 inch wheels are another option, just not in the brand of wheels I desire.

Thank You.
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Reply By: Malcom M - Monday, Feb 05, 2018 at 12:31

Monday, Feb 05, 2018 at 12:31
Look at the manufacturers website.
All tyres have a max rim size value. That values is advised by the manufacturer.

AnswerID: 616683

Reply By: splits - Monday, Feb 05, 2018 at 12:48

Monday, Feb 05, 2018 at 12:48
Contact the tyre manufacturer.. If they don't know then nobody does. There should be a customer information number or email address on their web site. They should also be able to help with the correct pressues and how to adjust them according to load.

Tyre design is a lot more complex than it looks. I remember seeing a 235 on a six inch rim as standard equipment on an earlier 4wd, possibly as far back as the 1980s. It may have been a Pajero but I don't think they were as big or as heavily constructed as a 235/85 x 16.

There was some information on the Dunlop site about wheel widths and their effect on tyre temperature. It may still be there. As the wheel gets wider or narrower for the same size tyre, it moves the designed flex point of the sidewall either towards the bead or the tread. This has a an adverse effect on the tyre temperature.
AnswerID: 616684

Follow Up By: Sneaky Pete - Monday, Feb 05, 2018 at 14:38

Monday, Feb 05, 2018 at 14:38
Hi Looking at 235/85r16 tyres there are rated for 6-7.5 in rims on most sites . I have run on 6 in rims pressure down to 15 psi no problems through simpson canning ete etc..
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FollowupID: 888153

Reply By: rlhydn - Monday, Feb 05, 2018 at 15:10

Monday, Feb 05, 2018 at 15:10
Sneaky Pete has the numbers. Tyre manufacturers will have the min-max wheel width

I'm running 255/85/16 on 7" Toyota rims.

AnswerID: 616685

Reply By: bigden - Monday, Feb 05, 2018 at 19:59

Monday, Feb 05, 2018 at 19:59
I have run 235/85s on factory 7" rims for years now , no issues at all and down to 12psi in sand
Came from the factory with lower profile 235s on 7" rims
AnswerID: 616700

Reply By: Robin Miller - Monday, Feb 05, 2018 at 20:00

Monday, Feb 05, 2018 at 20:00
7" is best size for that tyre width.

I ran 7" trak 2 16 inch wheels with my 235/85 on GU patrols.
Robin Miller

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AnswerID: 616701

Reply By: Bob Y. - Qld - Monday, Feb 05, 2018 at 20:55

Monday, Feb 05, 2018 at 20:55
I ran 235.85R16's on both Toyota std split rims and Sunraysia copies 7" steel rims, with no dramas, on an '02 HDJ79 ute.

They are a good choice, because in an emergency you can run a mix of 235's, 265.75R16 or even 750R16, just to get home.

Bob

Seen it all, Done it all.
Can't remember most of it.

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AnswerID: 616702

Reply By: Member - shane r1 - Tuesday, Feb 06, 2018 at 07:51

Tuesday, Feb 06, 2018 at 07:51
8” spread the walls out wider and expose them to possibly more sidewall damage, and probably no other benefit, the wider rim certainly doesn’t change the tread width. IMO
Cheers
AnswerID: 616713

Reply By: BenFraser747 - Wednesday, Feb 07, 2018 at 10:49

Wednesday, Feb 07, 2018 at 10:49
Thank you for the responses. I've decided to stick with my stock 16x7 wheels for the time being. I emailed BFG and had the following response:

There is a range of rim widths which are approved for use when utilising the LT235/85R16 tyre dimension.

The range of widths are from 6.0 to 7.5 x 16. The preferred rim width is 6.50 x 16. The use of an 8.0 x 16 rim is not approved and would void any warranty. The most common fitment would be 7.0 x 16.
AnswerID: 616743

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