Madza tyre size???

crozmac · Post by **crozmac** » Mon Apr 23, 2007 2:00 pm

I have a '02 Mazda Bounty SDX double cab 4wd with the factory alloy mags and the factory michelin tyre's and size 235/75 R15.
What I am wanting to know is if 31" tyre's will fit??
I have seen a few bounty's with 30" and they fit easily as they are only about 10mm bigger than the factory size tyre. The 31" are about 41mm bigger and alot wider? So will these tyre fit inside the guards with no rubbing and will the miss the front bumper?
Tha alloy's are 15x7's.
Any help would be appreciated.

H2OLOVA · Post by **H2OLOVA** » Mon Apr 23, 2007 2:29 pm

best bet would be to fit some up and see. Most tyre shops would chuck a couple on to try if they thought it was gonna help sell 4 new tyres :wink:

warlord225 · Post by **warlord225** » Mon Apr 23, 2007 3:27 pm

30x9.5/15 are the same as 237/75r15 virtually.

so I would say that a 31 will fit, as its only about and inch taller

coxsy · Post by **coxsy** » Mon Apr 23, 2007 4:59 pm

hi got a mazda proceed cabplus 4x4 run 265x75 r16s on mine a little rubbing nothing major

the bad front suspension travell will be more of a pain than 31 's

crozmac · Post by **crozmac** » Mon Apr 23, 2007 8:02 pm

Would like to know definite as the tyre shop I am going to have no 31s instock and if I want them they will have to get them in.
Cozsy what width are the rims? 7s or 8s?
Thanks

coxsy · Post by **coxsy** » Mon Apr 23, 2007 8:42 pm

hi got 16x8 rims , got 16" muds as the ute came with 16" surf rims , and the slight lift the rims gives is quite handy,

crozmac · Post by **crozmac** » Wed May 02, 2007 5:39 pm

No more opinions or experiences about fitting 31's?
Would I have any WOF issues if fitting 31's?
Really want 31's but if they are going to rub or even fit or going to be a hassele maybe its not worth it.
Thanks

coxsy · Post by **coxsy** » Wed May 02, 2007 5:55 pm

are you intending to run the muds full time, drop down a size and get 30's should get past on a wof, changed the saf from 15's to 16's VTNZ don't have a problem with them when i take it for a wof your allowed to do a 5% increase in size before its certable,

crozmac · Post by **crozmac** » Wed May 02, 2007 6:23 pm

Yes I am wanting to run muds full time as I only want one set of tyre's.
Do you think they will ping me for 31's????
Just out of curiousity the 2003 the year after my truck came out with 265/70 R15 which are 31's roughly. Maybe I could bullshit my WOF guy and say that was the size my truck came with???? Opinions.
s roughly. I cant find anything out to see what else they changed to run them.

coxsy · Post by **coxsy** » Wed May 02, 2007 6:25 pm

sound like a good idea you should be good at that size then

icekayak · Post by **icekayak** » Wed May 02, 2007 7:35 pm

have a little play on this:
http://www.1010tires.com/TireSizeCalculator.asp?action=submit

According to my calculations on there they are about 6.79% off... personally with those as long as they fit inside the flares i don't think you'll have a problem with WOF (insurance is another matter thought

)

Stock Tire - 235/75R15
Search Tires Tire 1 - 31x10.50R15
28.87 in 733.29 mm
30.97 in 786.63 mm
Diameter Difference: - Diameter Difference: 6.79%

Another thought is which tyres were you planning on getting as most 31's don't measure 31" tall....
like my 31x10.5/15 groundhawgs only measure about 30" (GRRRR) and my 31x10.5 pirelle scorpions @ 25psi are 30.5" So that would put it around 5.3% (which we will round down) so would be sweet

also your tyre pressure will change the diameter...

Where abouts are you? there's a good chance someone on the forum will be local and would let you try one on your truck...

crozmac · Post by **crozmac** » Thu May 03, 2007 2:01 pm

I live in Invercargill.
The tyre's I am considering are Cooper STT the new pattern.
If this helps????
Thanks

icekayak · Post by **icekayak** » Thu May 03, 2007 3:46 pm

hmm on http://www.coopertires.com.au/tyres/stt_new_specs.htm

they list the 31X10.50R15 as 781mm (30.7") and the 235/75R15 as 739mm (29.1") which equals 5.38%...

Have a look what the actual rules are regarding the 5% but you should be sweet if its 5% diameter change (circumfrence change will have to get the real calculator out)

wjw · Post by **wjw** » Thu May 03, 2007 4:21 pm

Found my post from a while back...

It MUST be certed if the rolling diameter is 5% larger than the OE Spec.

Specs:

http://www.ltsa.govt.nz/publications/vi ... s-v2-3.pdf

Vehicle Inspection Requirements manual:

http://www.ltsa.govt.nz/publications/vi ... index.html

Has an FAQ on here thats useful

http://www.lvvta.org.nz/

you can fit any diameter wheel as long as the rolling circumference (the distance one turn of the wheel travels on the road) does not increase more than 5% over the original equipment without the need for an LVV cert. The main reason for this is that a substantially increased rolling circumference will make the speedo under-read (i.e. the speedo will read, say, 90kph when you are doing 110 kph).

Unfortunately what needs certifying isn't always in the WOF book.

The other thing to think about with ANY mods is that your insurance company may not cover you without a Cert.

crozmac · Post by **crozmac** » Thu May 03, 2007 4:57 pm

So if you are correct with the diameters there icekayak does anyone know what the actual difference the rolling circumfrence is?
If the 5.39% increase in diameter?
Thanks

wjw · Post by **wjw** » Thu May 03, 2007 5:07 pm

Circumference = 3.14 x Diameter

28.9" (235/75R15) = 90.746"
31" = 97.34" == 7.27% Increase in rolling Diameter
32" = 100.48"
33" = 103.62"
35" = 109.9"