tyre size info help please

[bigdawg]

ok well, YES i have googled this and YES i have spent the last 2-3 hours trying desparatley to understand tyres more :rolleyes: but all i have seemed to have done is learn more irrelevant things that have just made me ask more questions :Grrr

originally all i wanted to know, is the difference in speed/performance/safety between 2 sets of tyres

Tyre A - 235/45/ZR17 (fronts) | 255/40/ZR17 94W (rears)

Tyre B - 225/35/ZR17 82Y (fronts) | 255/40/ZR17 94Y (rears)

now a few more additional questions if anyone has the wisdom?!

- does the "Y" mean they can perform at higher speeds (i think 186)
- On Tyre B fronts, isn\'t "82Y" (assuming the 82 is load capacity) too low? shouldnt it be around the mid 90\'s?
- is it better to have a lower "profile" than a larger one?
- and lastly, the "Z" in "ZR" is the speed rating (150mph+) but so is the "Y" in the "94Y" (186mph) :confused:


thanks in advance guys - i just want to make sure i understand this all as it is a very crucial safety aspect