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tyre size ???????? conversion ?

General Tech Talk

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tyre size ???????? conversion ?

Post by dirtyGQ »

i had tyres before that were 305/70 16 what size are my new tyre is they are 33x12.5 15 in the other measurement ?
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Post by RAY185 »

this what u're looking for?

http://www.4lo.com/calc/gearmetric.htm
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Re: tyre size ???????? conversion ?

Post by RAY185 »

dirtyGQ wrote:i had tyres before that were 305/70 16 what size are my new tyre is they are 33x12.5 15 in the other measurement ?
According to that link 305/70R16 = 32.8"
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Post by saigo »

Heres another site.

http://www.1010tires.com/TireSizeCalcul ... ion=submit
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Re: tyre size ???????? conversion ?

Post by JOHNZ »

dirtyGQ wrote:i had tyres before that were 305/70 16 what size are my new tyre is they are 33x12.5 15 in the other measurement ?

305/70-16 IS ALMOST THE SAME AS 33x 12.5-15 VARIES WITH DIFFERENT BRANDS OF TYRES

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Post by -Mick- »

on the subject of size conversions what is a 7.00 r16 and a 7.50 r16 :?:

How do you figure these out :?:
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Post by dirtyGQ »

Thanks all now i know
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Post by Nev »

-Mick- wrote:on the subject of size conversions what is a 7.00 r16 and a 7.50 r16 :?:

How do you figure these out :?:
Good Question Mick..often wondered this myself. Those sizes are for split rims arent they? Im thinking they might come in 7 or 7.5 inch width and only come in one diameter...whatever size the base model cruisers and nissans with split rims had...not entirely sure tho.
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Post by Beastmavster »

This was my understanding and may be wrong. Technically it's simple..... very similar to the method for metric.



7.5" wide and 7.5" tall tyre (100% aspect) on either side of the rim = 7.5" + 7.5" = 15" + 16" rim = 31"
Most however measure 31.8" (eg 32") - think this is cos the old school is measured as the size of the carcass excluding the tread... eg your size when worn down.

eg: http://www.simextyre.com/Tyres/LS803.asp first 7.50R16 I found in google is 810 mm or 31.89"

They do vary a bit in size as per normal.

Recommended rim size for 7.50R16 is normally 5.5" to 6" wide.

Using the same calculation 7.00R16 = 30" 6.00R16= 28"


Metric goes by something similar, except your main measurement is the tread width not the sidewall height (as there is different aspect ratios). And of course it's in mm.

305/70/16 therefore is 305mm wide = 12"

Sidewall height = 12" x 70% = 8.4"

Therefore sidewall height both sides of rim = 8.4" + 8.4" = 16.8"

16.8" + 16" rim = 32.8"

Clear now?


Now someone explain to me why most 33" tyres are 32.6" I really wanna know how that works......
Last edited by Beastmavster on Thu Feb 23, 2006 6:37 pm, edited 1 time in total.
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Post by cutzook »

a 33 is nearly a 285/65 R16
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Post by -Scott- »

cutzook wrote:a 33 is nearly a 285/65 R16
285/75-16 is approximately 32.8x11.2-16

And the 33x12.5-15 vs 305/70-16; same OD and width, but different aspect ratio = different sidewall height. And the 16" tyres probably have a higher load rating.

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Post by andrew e »

anyone know what a 900x16 is in inches?
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Post by Beastmavster »

34"....
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Post by GRIMACE »

andrew e wrote:anyone know what a 900x16 is in inches?
34 :?:
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Post by -Scott- »

I expect it's 9.00x16 and not 900mm x 16. 900mm is 36", but I've never heard of tyres defined that way.

Scott
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Re: tyre size ???????? conversion ?

Post by bogged »

dirtyGQ wrote:i had tyres before that were 305/70 16 what size are my new tyre is they are 33x12.5 15 in the other measurement ?
www.google.com
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