175/55 R15 would be a very low tyre for a 4/4. You may be better off with 185/65 R15 would only be a few millimetres lower.

There is a useful tyre calculator at
http://paws.kettering.edu/~amazzei/tire_calculator.html

This will allow you to do some comparisons on proposed tyre changes. Don't forget that you may need to Re-calibrate the speedo.

Peter

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