Board logo

Rolling Radius
Johnmor - 30/10/05 at 08:49 PM

Does anyone know a link to calculate the rolling radius of wheel and tyre combinations,
I have just put a deposit on a Viento kit and they recomend 17" wheels with 45 series tyre. Sounds as if the ride might be a bit hard so what series tyre on 16" rims would give a similar rolling radius?

Aboardman - 30/10/05 at 08:55 PM

try this

http://gs.tolan-hoechst.com/tirecalc.htm

cidersurfer - 30/10/05 at 08:55 PM

Have a look here

Snuggs - 31/10/05 at 07:59 AM

Or here.


http://www.tyresave.co.uk/tyresize.html

smart51 - 31/10/05 at 08:17 AM

the ROLLING radius depends on the weight on the tyre and the tyre pressure. The weight of a BEC and the low tyre pressure make it hard to predict accuratly.

Syd Bridge - 31/10/05 at 09:38 AM

I would question anyone who recommends this tyre/wheel combination, for such a light and skittish car. They might 'look' fancy and fast, but are downright dangerous.

This has been discussed at length previously, after a couple of BEC's were written off in close succession.

13" wheels are lighter and cheaper, and so are the tyres, and the combination with the proper width tyre is much safer.

But, go ahead if you must, it's your life and car, just don't take anyone with you, please.

G.Man - 31/10/05 at 09:47 AM

I would view 16 as a max, but 15's much better for a larger engined car (standard fitment on a cosworth sierra so up to the job)

13's and 15's still look good, 17's are just better bling bullshit factor...

If you are buying a car for handling the last thing you need is bullshit factor..

andyd - 31/10/05 at 11:48 AM

Yep, I'll second that, go for 15". The tires will be much cheaper as most tin tops use that size these days. 13" may be "safer" but at some point the tires will be more £££'s if they aren't already. I don't buy tires often enough to compares the pricing.

ChrisGamlin - 31/10/05 at 12:31 PM

Most of the grippiest road tyres (Yoko 48s, ACB10s, Toyo R888 etc) still seem to be cheaper in 13" than 15", I guess they sell a fair proportion of those tyres into motorsport where a lot would be running 13" rims?
Although there may still be a small advantage with 13" over 15", I dont think its significant enough for most of us to notice, its only when going up to the silly sizes that it could adversely affect things to make the car harder to drive and more unpredictable.

Chris

Kowalski - 31/10/05 at 12:44 PM

quote:
Originally posted by smart51
the ROLLING radius depends on the weight on the tyre and the tyre pressure. The weight of a BEC and the low tyre pressure make it hard to predict accuratly.


Yes, the rolling radius depends on weight and pressure, and rolling radius decides your ride height

BUT

The tyre tread is a fixed length, and doesn't change, that means your gearing is tied to the tyre tread length. So, to get the speedo correct, the tyre tread length has to match the original.

G.Man - 31/10/05 at 02:07 PM

And additionally, at operating speed, rolling radius is more consistent due to the centripetal forces acting on the tyre..