wheel size calculating

[markheaney2]

does anyone know the formula to work out how to measure the sidewall on a tyre ie a 235 45 17 tyre will have a deeper sidewall than a 205 45 17 is this true or false and if it is true what formula do you use to work out running circumference of a tyre

 

[kikkthecat]

There is a Tyre calculator Here.

And yes, a 235/45 will have a deeper sidewall than a 205/45 and hence a greater circumference.

A 235 is also wider than a 205 and it depends on the width of the wheel not the tyre as to whether it will fit or not.

 

[markheaney2]

thank you very helpful site

 

[stats007]

You don't really need a calculator to do that. The profile is a percentage of the track (width) so 205/45/17 means the sidewall is 45% of 205mm i.e 92.25mm. 235/45 you can already see will be larger in diameter - the sidewall is 105.75mm.

As mentioned - 235 on a rim designed for 205 is too much - 10% increase max is a good rule of thumb.

 

[bolide]

If you use my calculator you can compare two different sizes

http://www.bolide.co.uk/actions/info.taf?page=tyresizecalculator

Nick Froome
www.w124.co.uk

 

[mark.porthouse]

Bolide,

Nice calculator. I've been using a spreadsheet to work out what would be an acceptable space saver wheel/tyre for my W124 after the LPG tank replaces the full size spare.

I've just bought an unused Mercedes 125/80 x 17. I note that your calculator doesn't quite run narrow enough for that... (pity all those 2CV owners as well!)

Cheers,

Mark

 

[bolide]

If you're going to keep a space-saver in the back of a W124 estate you'll have to think about tethering it or bolting it down. In the event of a collision the kinetic energy of an untethered wheel & tyre would be huge - it could very easily become a lethal object

Nick Froome
www.w124.co.uk

 

[mark.porthouse]

Bolide,

Yes, absolutely! Thanks for thinking of our health and safety.

I'm thinking of strapping it on the other side of the load bay, through to metal somewhere. However, I'm waiting until I get the car back and the space saver delivered before I start figuring it out.

I'm going to put on a separate thread about the LPG conversion hopefully in the next day or two.

Mark