Question on tyre profile...

[NightKids]

My car comes stock with 195/55/15 and I was wondering if it's illegal to change the profile of the tyre of the same size? The dude from Bob Jane told me I had to stick with the same profile...

The tyre I was wanting to put on are 215/45/15. Will this pass roadworthy/VicRoads?

[mugen_ctr]

will pass with flying colors, its more to do with rim size rather than tire profile

[CivicEH9]

Only problem I can see is your rolling diameter would be slightly smaller which would put your speedo out but I'm not sure if that's enough to be a legal issue
I think 215/50/15 would be better if you can get it

[DLO01]

^^^ What he said.

195/55/15 wall height is 107mm
215/45/15 wall height is 97mm
215/50/15 wall height is 107mm

[NightKids]

I read somewhere that the whole diameter cannot be more than 15mm out... can anybody clairfy?

[Oxer]

In Victoria, the rolling diameter has to be within 12mm of the factory specs either way (bigger or smaller) To be legal.

[anzai]

http://www.vicroads.vic.gov.au/NR/rdonlyres/CC48FC10-4D57-4F04-82E1-3BD72EF88340/0/VSI8.pdf

[NightKids]

Yeah i've read that, i'm a lil confused about that 15mm diameter rule which I think applies to this case...

[CivicEH9]

Yep it definitely applies.
With the 195/55/15 you have now, your diameter is 595mm
With the 205/45/15 it would be 574.5mm so the difference is more than 15mm which is where your problem is

[NightKids]

Thanks for clarifying that. What's the formula for your calculations?

[CivicEH9]

Convert rim size to millimetres = 15 x 25.4
Tyre Wall Height = width x profile
Rolling Diameter = rim size + 2 x wall height

[NightKids]

Thanks a lot! It's Maths all over again!

[CivicEH9]

No worries mate. Glad I could help

[dougie_504]

How much does this actually affect your speedo?

[CivicEH9]

Depends on how big the difference in tyre size is
In the sizes the OP was talking about 205/45/15 is 5% smaller than 195/55/15 so the speedo will read 5% too fast

[Rudy]

Just use this will give you all the answers...

http://www.1010tires.com/tiresizecalculator.asp