Rolling circumference of 10" 32r tyre
Turbo Mini Forums

does anyone know what this is, trying to configure my new dash, and have not got car with me at the moment.

Cheers

Jimbo

Team Racing

http://www.tyretraders.com/Tyrecalculator/

give that a go jim.

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

thanks buddy, that will do for now

Team Racing

let me know what you get mate, i've not done mine either!

Apparently those calculators are out by quite a bit. Best thing to do is chalk the wheel and roll it and see. There's a post about it somewhere but don't have time to search right now.

i was going to do it but havent had the chance yet. i'm going to put a rough figure in and then use a GPS to get it accurately.

my speed is done by gps, I only need this figure to get the software to get the gear display right

Team Racing

wrap a bit of string round the tyre and measure its length

Fluck me jimbo, what dash is this?!

and did you nick it off the starship enterprise

race technology thingy, I was pissed of with fitting wheel speed sensors, as they are always breaking on the migs, and I've got disk breaks which makes it even worse, this uses gps for the speed. This also means I can get lap times when I'm at track days (which don't allow beacons)

Team Racing

Rolling circumferance is different to the tyre circumferance, and is affected byt the tyre pressure and tread wear.

Demon Tweaks cataloge list these with a rolling circumferance as 1496mm

Edited by Sprocket on 1st Apr, 2008.

i did the method of rolling a wheel along thr ground aswell, worked out very accurate really

where my speed sensor is id imagin speed would be incorrect on corners tho'

David.

Any updates on this?

Is 1496mm correct?

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Easy enough to measure Paul if you have some of these already on the car. Mark the tyre and the ground, use a plum line off the body to ensure an accurate full rotation of the wheel, and roll the car forward and mark the ground again, then measure between.

Im sure you don't need me to tell you how to suck eggs

I always allow 5mm difference in calculated radius to rolling radius, it at least gets you a little closer, and working back from a 165/70x10 tyre numbers and the noted 1496 value above, confirms that 5mm difference in radius to rolling radius is pretty dam close

Edited by Sprocket on 23rd Jan, 2010.

The car still sits on the ramp without an engine :(

I've just ran a tape measure around the circumference and it comes out at 1550mm. So 1496 is certainly in the right ball park.

It looks like a 3.44 diff will give us 120 mph at 7500rpm on the A032Rs.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

2 or 3 revolutions will arguably be even more accurate as the error in getting the chalk mark back to BDC will be spread over the 3 revolutions (i.e. 5mm error on 1496 = 0.3% inaccuracy. For 3 revs 5mm error on 4488mm = 0.1% error).

Course if your speed is measured on a single wheel you'll get errors for it being inside/ outside on the bend when driving, but it won't be far out.

Yes i moved to the darkside

Instagram @jdm_brett

tires expand when going fast, thats tricky too calculate

internationally known as "big" swede

unless you have GPS

I have some figures for this, I'll dig them out

Team Racing

Cheers, need to make sure we're not running out of steam at the end of the strip.

Edited by sturgeo on 25th Jan, 2010.

anyone any wiser yet? is 1496 good to go for a 10" 32r?