Wrong tyre size?

nst68 · 1 Aug 2017 at 13:39

Hi

I need to replace one of my tyres, the current size of all four is 185/65 R15

I put the reg number in to Blackcircles and it came back with 195/65 R15 :confused:

Have I been running the wrong sized tyre for years?
Is there a way to tell what size tyres I should have?

paradigm · 1 Aug 2017 at 13:44

What car?

Not that the two sizes in question would have made a massive difference either way.

nst68 · 1 Aug 2017 at 13:48

Hyundai i30

Big Spender · 1 Aug 2017 at 14:20

Your cars handbook should give you the different tyre size options for your car when you look at the tyre pressure section.

grudas · 1 Aug 2017 at 16:09

https://www.wheel-size.com/size/hyundai/i30/

andy_mk3 · 1 Aug 2017 at 16:13

Look in your handbook or on the tyre pressure sticker usually found in a door shut or fuel filler flap.

nst68 · 1 Aug 2017 at 18:14

Thanks for the help guys.

I looked in the manual and both 185 and 195 are ok, but as I've got 185's on already I guess I have to stick with them (which is a pity as the 195's are about £7-£10 cheaper!).

Phil W · 1 Aug 2017 at 18:44

Go on a tyre calculator site and see what the difference is in speed between 185 and 195. If it's tiny just go for 195.

Kenai · 1 Aug 2017 at 18:47

Phil W said:
Go on a tyre calculator site and see what the difference is in speed between 185 and 195. If it's tiny just go for 195.

For one tyre?

I don't think that's sensible advice, no matter how small the difference.

Maybe if he was replacing a pair... even then i'd be uncomfortable mixing sizes front to back

Phil W · 1 Aug 2017 at 21:13

Kenai said:
For one tyre?

I don't think that's sensible advice, no matter how small the difference.

Maybe if he was replacing a pair... even then i'd be uncomfortable mixing sizes front to back

Ah. Assumed pair. Didn't read it properly :rolleyes:

Kuros · 2 Aug 2017 at 08:50

Phil W said:
Go on a tyre calculator site and see what the difference is in speed between 185 and 195. If it's tiny just go for 195.

I thought the first part of the tyre's number is Width, so shouldn't make a difference to speed.

Still wouldn't want to replace just the one, though.

grudas · 2 Aug 2017 at 09:18

If you're changing one tyre then stay with the same size.

Otherwise I'd recommend changing in pairs unless other side is new.

Big Spender · 2 Aug 2017 at 10:13

Kuros said:
I thought the first part of the tyre's number is Width, so shouldn't make a difference to speed.

Still wouldn't want to replace just the one, though.

Thats correct, 195/65/15 would be 195mm tread width, sidewall height 65% of the tread width, 15" wheel rim.

paradigm · 2 Aug 2017 at 13:31

Kuros said:
I thought the first part of the tyre's number is Width, so shouldn't make a difference to speed.

Still wouldn't want to replace just the one, though.

Which would be a ~2% difference in circumference.