Tyres: what'll work best?

[Copperbottom]

What would be the best option? 6" wide tyres on 7" wide rims or 7"wide tyres on 6" wide rims? I can't fit 7" wide tyres with 7"wide rims on my car<I'm currently using the 6" rims with 7" tyres.

Also: Dunlops,Avons or Hoosiers?

[terence]

6in tyres on the sevens,and Hoosiers,should be reasonably responsive,then of course you'll have to play with the pressures to suit.

[TEAM78]

Assuming the mass (thats mass not weight) between the 6" wide and 7" wide rims is the same and you have lots of engine torque then you should run 6" wide rims with the 7" wide tyres.
I leave you to figure why and it isnt obvious

The tyre choice is heavily dependent upon vertical loads the tyres have to experience, simply just go and test them all.

[phoenix]

Originally Posted by TEAM78

I leave you to figure why and it isnt obvious

You are right - it isn't obvious. Neither can I figure it out, so please explain!

[graham bahr]

in my experience with a saloon car on slicks best results always come from wider rim, narrower tyre combo

[Mike Holmes]

You don't say what diameter, another factor to consider is the weight of the car and availability of compounds for your chosen size?

[TEAM78]

I can see this becoming a raging debate because the tyre is quite simply a very complex thing that is still far from being fully understood now, my reasons behind my assumed guess is that firstly the vehicle isnt overtyred and therefore needing as much grip as possible, If thats the case you then need to obtain as great as tyre volume as possible along with as much of mechanical keying with the surface. As approx guesses you get as wide a tyre as possible with the softest compound as possible, then work towards harder compounds if the tyre over heats,
Given all else is sensible in profile carcuss construction etc....

Graham thats quite an interesting statement as I have always found the opposite to be true, Just goes to show that the best way to find out which tyre rim combo is best by simply testing, Its always cheapest to just go and test the combinations on a test day.
this thread is almost pointless without a huge amount more info, but I guess copperbottom wanted a couple quick fire answers.
Certainly got them now

[Copperbottom]

Well: my car weighs 850kg with driver,has 175bhp,is rwd and is probably undertyred,I've been using 6" rims with 7-21-13 Avon slicks in sprints for the last 5 years,I've now moved onto racing and found that the compound I chose was too hard so I've got to buy new tyres I tried 7" tyres on 7" rims but they foul the rear arches! .Thanks for the answers so far

[graham bahr]

Graham thats quite an interesting statement as I have always found the opposite to be true, Just goes to show that the best way to find out which tyre rim combo is best by simply testing, Its always cheapest to just go and test the combinations on a test day.

having used 195 and 200 section slicks on 7 and 8 inch rims on a 800kg saloon car and 235 section slicks on 8, 9 and 9.5 inch rims on a 950kg saloon car i found in all cases the car was better on the wider rims

[TEAM78]

i remember reading in the high performance tyre book about some guys were tyre testing and they found exactly what Graham describes but they also found everytime they widened the tyre the car went quicker again as well.

[Notso Swift]

Originally Posted by graham bahr

having used 195 and 200 section slicks on 7 and 8 inch rims on a 800kg saloon car and 235 section slicks on 8, 9 and 9.5 inch rims on a 950kg saloon car i found in all cases the car was better on the wider rims

But Copperbottom is efffectively talking about using your 9" rims with the 200 section tyres
I have never seen a tyre manufacture recommend a tyre that is actually narrower than the rim, the same yes 10% tyre wider, yes, but never more rim.