tyre sizes

Submitted: Thursday, Jul 07, 2005 at 00:45
ThreadID: 24511 Views:4987 Replies:2 FollowUps:2
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I'm sure this has been explained before, but once more for the dummies! Why are some tyre sizes listed as 31x10.5x15 and others as 235/85R16? I know the last figure is the wheel diameter. I'm presuming that some are inches and some are millimeters but is the 31 the tyre width (same with the 235)?
Secondly, I have just purchased a base model 80 series LC (93 model) with standard rims and wish to upgrade. I would ike to stay with 16 inch rims but wider and get some good rubber. I think I have read somewhere that you can't put wider 16 inch rims on due to interference with brakes or something?
ps thanks for all the advice on Troopy back seats everyone!
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Reply By: bware - Thursday, Jul 07, 2005 at 00:55

Thursday, Jul 07, 2005 at 00:55
By the way I'm Bware who posted the question.
How come everyone upgrades their rubber but drops to 15 inch wheels? I saw an add in a certain publication the other day that advertized a Hilux that had been 'lowered'; what's the world coming to?
AnswerID: 119215

Follow Up By: flappa - Thursday, Jul 07, 2005 at 09:30

Thursday, Jul 07, 2005 at 09:30
They dont much anymore.

Most people went back to 15 inch wheels because that was were the greatest variety of tyres was.

Its not now , basically , if you can get them in 15 inch , they also come in 16 inch.
FollowupID: 374364

Follow Up By: Truckster (Vic) - Thursday, Jul 07, 2005 at 10:00

Thursday, Jul 07, 2005 at 10:00
The other reason is 15inch tires are WAY cheaper...
FollowupID: 374370

Reply By: GQ_WA - Thursday, Jul 07, 2005 at 01:44

Thursday, Jul 07, 2005 at 01:44
31X10.5X16 = 31" Overall diameter, 10.5" Section width and 16" Rim diameter

235/85/16 = 235mm Section width, 85 is the Aspect ratio and 16" Rim diameter.

Aspect ratio is calculated by dividing the section height by the section width and multiplying by 100. (In this example, the sidewall will be 85% of 235)

Converting metric to inches will give you the following:
Section width:
= 235 x 0.0393701
= 9.25"

Overall diameter
= [(0.85 x 235) x 0.0393701] x 2 + 16
= 31.73" Overall diameter

The following website might be able to explain it better:

or just use the tyre calculator:

Hope this helps.

AnswerID: 119216

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