Tyre Sizes - Rough Guide Thread

mag wrote: i run 225/75/15 bfg a/t , no mods at all , fit fine , no rubbing etc

Don't think they make them in that size. Sure they aren't 215/75/15?

standard steel wheels , not sure on size !!

Busta wrote:

mag wrote: i run 225/75/15 bfg a/t , no mods at all , fit fine , no rubbing etc

Don't think they make them in that size. Sure they aren't 215/75/15?

I think Gus has some in that size on his fat boy wheels

just checked , they are 225/75/15 on standard steel rims

mag wrote: just checked , they are 225/75/15 on standard steel rims

Cool. I sit corrected! They don't do that size anymore though.

Thanks to Bosanek a tyre Wiki page is appearing in the BigJImny Wiki

Many thanks to him for contributing

Martin

Just a little query guys about Tyre pressure for a 215/75R15 A/T ... how much do you recon??
Also, bearing in mind Jimny's are really bouncy...

All tyres will have a maximum weight at a given pressure written on the side. Your vin tag will have maximum weight of each axle. Using mathematics you can get the correct pressure for the imposed load on each tyre. Alternatively you can do the chalk test where you put a line of chalk across the width of the tyre and drive froward gently to see how much chalk is left on the tyre.

11/60 wrote: All tyres will have a maximum weight at a given pressure written on the side. Your vin tag will have maximum weight of each axle. Using mathematics you can get the correct pressure for the imposed load on each tyre. Alternatively you can do the chalk test where you put a line of chalk across the width of the tyre and drive froward gently to see how much chalk is left on the tyre.

Yeah but the tag is for the standard tyre size... But I recon the chalk test might be a good option.

No. The vin tag gives the maximum permitted mass on each axle, regardless of what else you do to it be that different tyres or anything else.

Regarding the question about the correct pressure when using larger tyres, I have some contribution:

As far as I know, generally the larger the tyre is (on a same vehicle), less air pressure is needed for the same effect.

Reasons: the tyre itself is larger (stronger), the contact surface with the ground is larger, and more air is inside anyway (larger internal tyre capacity).

Theoretically, the pressure should be reduced by the same percentage by which the internal capacity of the tyre has increased (the goal is to have the same amount of air inside as with the stock tyres). Since the tyre is similar to a torus (geometrical shape), you'll need some good geometrical math skills to do an exact equation.

Regarding various tyre sizes (the point of this entire thread),

I made a comprehensive table of all "interesting" tyre sizes for Jimnys.
The table contains mathematical calculations, as well as various data and comments.
The table can also be used for Samurais.

Here is the published table:
docs.google.com/spreadsheets/d/1qwxmEIQ9...ml?gid=0&single=true

I included the link to this table in my article in BigJimniy wiki:
www.bigjimny.com/mediawiki/index.php/Imp...ain_use#1._Tyre_size

I compiled the table to the best of my knowledge and assumptions.
I invite everyone to contribute to fill the missing pieces in that table, or to correct existing ones.