Track tyres - what width rims?
Discussion
I'm looking to use a 225/50-15 tyre on the rear of my car and I am having trouble decided how wider wheel I need to fit to accomodate them. Bearing in mind this is for a track car that although remaining road legal will generally trailered, and arch clearance isn't really a problem.
My understanding was a wider rim would stretch the side wall and stop it flexing offering more traction and stop it from overheating as quickly.
However looking at the following manufactures/brands Kuhmo Ecsta V70A, Yokohama A032-R & Toyo R888 they all recommend 6-8" wide wheels with Kumho suggesting that a 7" rim would be optimum. Considering nominal width of the tyre is 225/9" I'd have thought even an 8" rim would have been too narrow for optimum performance.
Any help much appreciated
My understanding was a wider rim would stretch the side wall and stop it flexing offering more traction and stop it from overheating as quickly.
However looking at the following manufactures/brands Kuhmo Ecsta V70A, Yokohama A032-R & Toyo R888 they all recommend 6-8" wide wheels with Kumho suggesting that a 7" rim would be optimum. Considering nominal width of the tyre is 225/9" I'd have thought even an 8" rim would have been too narrow for optimum performance.
Any help much appreciated
225 is the tyre size, but it doesn't mean you should use a 225 width wheel as well. I use a 245 on a 9" rim and they work fine.
Surely you want some flex in the tyre, otherwise 1) no flex = very stiff tyre = very little progression on grip (i.e. one minute it's there, the next you're in the kitty litter) ; 2) it might pop off the rim under high cornering forces as you've got no play in it; 3) stretch sidewalls only decrease grip as the tyre doesn't move to make the most of the tread. Hence the recommendation for a 6-8" wheel (both 6" & 8" are within a +/- 1" spec).
Surely you want some flex in the tyre, otherwise 1) no flex = very stiff tyre = very little progression on grip (i.e. one minute it's there, the next you're in the kitty litter) ; 2) it might pop off the rim under high cornering forces as you've got no play in it; 3) stretch sidewalls only decrease grip as the tyre doesn't move to make the most of the tread. Hence the recommendation for a 6-8" wheel (both 6" & 8" are within a +/- 1" spec).
Yeah what your saying does seem to make sense and I was originally going to go for a 7x15 wheel as they'd fit front and rear and they'd offer a weight saving over a wider rim.
However what got me thinking that I should be going for something wider was that I've been reading 'Race and Rally Car Source Book by Allan Staniforth' which is a pretty well regarded book and he suggests using a rim 1-2" wider than the tread width of the tire.
However what got me thinking that I should be going for something wider was that I've been reading 'Race and Rally Car Source Book by Allan Staniforth' which is a pretty well regarded book and he suggests using a rim 1-2" wider than the tread width of the tire.
supercharged said:
Yeah what your saying does seem to make sense and I was originally going to go for a 7x15 wheel as they'd fit front and rear and they'd offer a weight saving over a wider rim.
However what got me thinking that I should be going for something wider was that I've been reading 'Race and Rally Car Source Book by Allan Staniforth' which is a pretty well regarded book and he suggests using a rim 1-2" wider than the tread width of the tire.
However what got me thinking that I should be going for something wider was that I've been reading 'Race and Rally Car Source Book by Allan Staniforth' which is a pretty well regarded book and he suggests using a rim 1-2" wider than the tread width of the tire.
You are getting your widths mixed up, as tread width is not the same as tyre width - tyre width includes the shoulder, sidewall, & rim protector as well, tread width does not include the shoulders where the tread changes.
Tread width is normally measured up to (about) where the dimples are in the above picture, whereas tyre width is the whole lot!
Specified rim size for the 225/50-15 A048s I have on the Scimitar is 7", but that causes the tread to bow out in the centre. This might be desireable for a suspension set-up that has some camber change, but with a live axle it's not so good, so I now run them on 8".
On the wider wheels the contact patch is significantly wider at the same pressure.
On the wider wheels the contact patch is significantly wider at the same pressure.
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