Confused About Tyre Profile Size!

[plasmid2]

G'day,

Have been doing some research on tyres on this site as I am almost due for some new ones. The car (03 BA T) is completely stock and I plan to keep the stock 17's but I am a bit confused about tyre profile size. Currently the stock dunlops are 235/45R17. I came across a thread on here about putting on 235/55R17. What does this mean? Will this put your speedo out? Does the car sit slightly higher off the road because of the higher profile? What would be a reason to put a higher profile tyre on anyway? Also, will the gap between the tyre and the wheel arch be smaller therefore?

Apologies for all the questions.

Thanks for your time.

Cheers.

[ratter]

. Currently the stock dunlops are 235/45R17. I came across a thread on here about putting on 235/55R17. What does this mean? Will this put your speedo out?Slightly yes, it will read slower than what it is at present Does the car sit slightly higher off the road because of the higher profile?Yes it will sit half the distance of the difference in tyre height between the old and new tyres, higher What would be a reason to put a higher profile tyre on anyway? Also, will the gap between the tyre and the wheel arch be smaller therefore? yes again by half the difference in tyre heights

Tyre wear will also affect all the things you have listed also

[kramo]

I wouldn't be putting 235/55 R17. If I keep my 17's I will be getting 245/45 R17 which is what the FG's come with now. The slightly bigger overall diameter will improve your speedo accuracy too.

[winstor]

This site explains it all.

http://www.carbibles.com/tire_bible.html

[CHLAXN]

my speedo never changed going from 18's to 20's and is accurate with two different gps's

[ratter]

rim size does not affect speedo readings or gearing, it is the tyre diameter that affects them

[plasmid2]

thanks for the reply guys!

Cheers.