Another track wheel thread... is 7" enough?

[Coralon]

I need to get some lighter 17" wheels that I can wrap in semi slicks and may have some but I am not sure if they are wide enough. I was looking at 225/45/17 RE55S for the tires but bridgestone recommend 8" rims to put them on. In experienced peoples opinions are 215's going to offer enough traction for serious cornering?

The bora is a very heavy car and for the moment at least weight reduction will be limited to the rear seat backs, spare tire etc so traction is very important but also brings into mind load ratings for semi slicks. Most seem to be lower than street tires, if 92 is the stock rating do I need that from racing rubber?

[Peter Jones]

Why not just run the stock size of tyre for that car in a semi slick?

The semi slicks are really much better than a street tyre.

If you go too wide you might not be able to get them up to temp.

I carry a lot more corner speed than a lot of more powerful cars on 10" rims and I'm only racing on 185/60/14

Just some food for thought, you don't have to go silly on the width.

[Coralon]

Thanks for the advice, thing is the 225/45/17 is the stock tire size for the 03 4motion. The wheels I am looking at are for sale here but are only 7" wide, I was mistaken about the rim size that bridgestone recommend, they say 7.5" rims not 8". So I guess the best question is thus...

Will a 225 semi slick go on a 7" rim or would I have to go down to 215's?

[Peter Jones]

There's a handy tyre (tire) size calculator at 1010tires.

Tire Size Calculator - tire & wheel plus sizing

According to that the acceptable range for a 225 is 7" - 8.5"

A 215 is 7"-8"

It's a very useful tool and will even tell you differences in speedo readings etc.

[fred27]

7" rim is ok for 225. I have used 225/50/15 on 7 X 15 and 225/50/16 on 7 X 16 for Toyo R888's for the track and is within the range that
Toyo recommends. Peter gives good advice and is right about not getting enough temperature into the tyre is you go too wide.
Also the smaller rim is lighter.

[Coralon]

Seems my googlefoo was weak earlier and your advice is well founded and backed up. Think I will stick with 225's so just need to get the rims.

Thanks very much for the help

[dylan8]

bora comes stock with a 225/45/17 on a 17x7

[Peter Jones]

bora comes stock with a 225/45/17 on a 17x7

Good point.

Mine's got the 16's on it. Never bothered looking into the bigger diameters as I do a lot of towing into paddocks and dodgy carparks with the race car on the tandem.

[dylan8]

might be a retarded comment, but being a semi slick does it make a difference? (are they more solid/square compared to normal road tyres)

[Peter Jones]

Yep, much tougher than street tyres, the Toyos have steel belts in the sidewalls and much less sidewall flex than a street tyre.

The compund is a lot softer too.

[gecko2k]

I am considering as well to buy some semis in the next few weeks. I never had 'brand new' ones. mostly only cheaper second hand ones. How long can you expect a semi slick to last? Same as a normal street tyre?

[Coralon]

No they will last much less, a few thousands km's at best and much less if you are driving them hard. But a few thousand km around a circuit is a lot of laps so you will get quite a few trips out of them. The interesting thing I am having trouble finding good information on is related to heat cycling, the effect it has etc and also shaving to reduce heat build up and tread squirm. I am sure others here will have more info relating to these important issues