I have a 1992 Saab 900 convertible turbo. Is it Ok to have 195/60/R15 tires on the back, and 195/65/R15 tires on the front? I have a chance to get four new Pirelli tires, but they don't match. I assume it's not a big deal, that the 60 to 65 won't make a difference in driving or performance. But thought I'd ask. First-time Saab buyer.
Yes, as long as you mix as you say front/back. You can't have two different ones on the same axle. That would drive very odd indeed.
...and probably play games with the ABS as well. The 60's and 65's will have a slightly different circumference.
No, if the car has ABS, as the different rolling diameter will confuse the hell out of the ABS, regards, Tom.
I had 185/65 front 195/60 rear on my beater 9000i - the ABS was fine.
That gives you only 6.5 mm difference in diameter. Not a big deal. Uneven treadwear can cause larger difference in diameter, easily.
However, diameter difference between 195/60-15 and 195/65-15 is 19.5mm, which may start confusing ABS, especially if 195/65-15 happens to be brand new and 195/60-15 is already worn out.
If that is the case you would be in trouble when going through a tight curve wher the outside wheel turns faster than the inside wheel, the ABS should not care.
I can imagine that would be OK; the ABS would only 'look at' individual wheels to see if that wheel is locked when it should not be, not at the possibly different speeds or speed ratios of all the wheels.
-- MH '72 97 '77 96 '78 95 '79 96 '87 900T8 http://go.to/saab96
Not as much difference there. Let's compare using one tire manufacturer; Michelin Energy MXV4 Plus:
Tire size Diameter
195/65-15 24.9" 195/60-15 24.1" 185/65-15 24.5"
So using the above stats (pulled from the tirerack.com web site) the difference between 195/60 and 195/65 is 3.3%.
The difference between your 185/65 and 195/60's is half that (1.7%). The larger the difference is the more likely you are to get into trouble with the ABS computer.
You can run with the different size tires. Different footprints will result in slightly different handling. As long as you do not push to the limits of handling, you should be fine. But it is a turbo convertible - so how hard do you drive it? It would have more body flex than the hardtop. This was very noticeable the first time I drove a Saab convertible after driving the 3 door hatchback body style for years.