13" x 7" wheels - tyre size confusion

[YellowPeril]

Hi All

 

I am hoping someone can advise on tyre size….and yes, I have checked the search facility 😬

 

Originally I had 15” 10-spoke anthracite wheels with 195/45/15 CR500 tyres.

I bought a second-hand set of 13” minilite style wheels and fitted Yokohama A021Rs. The 185/70/13s would not fit under the cycle wings so no cheap tyres from George Polley for me 😔 – I fitted 185/60/13s instead.

 

From the recent Caterham autojumble I picked up a couple more minilites. Assuming my current wheels were 6” or 6.5” wide I bought two 7” wheels as I ‘thought’ I wanted to put a slightly wider tyre on the rear. I now realise that my existing minilites are 7”.

 

So my questions…

1) Are 185s OK on 7” rims? They have seemed fine for a year but I am yet to drive the car in a more spirited manner on track.

2) Given that the original 15” wheels only had 195 tyres fitted is there any advantage to fitting 205s on the 13” rear wheels?

 

The benefit of the 185/60/13 tyres is that they are so similar in diameter to the 195/45/15s so I can switch between the two sets without having to change ride heights or speedo calibration, plus if front and rear tyres match I can carry a legal spare when touring.

 

I am keen to find out whether the choices are just down to preference or whether there is good reason to run one size instead of the other. The car is an R300 K-series with a fairly standard 160bhp. All help gratefully received.

 

[Steve Campbell]

Both of my friends run R300s and both are using 185's front and rear (and have done for years).

 

I think wider on the back is generally only for when you are heading towards or north of 200bhp ?

[YellowPeril]

Steve - thanks for the reassurance. I don't suppose you might be able to find out what width wheels they are using please?

 

I think the 185s are fine for the car, but when enquiring about getting a couple more tyres, the tyre fitters suggested that 7" wheels might be too wide.

[Phil B]

Hi,

Try looking at this link, quite a well written article and with a couple of useful tools to compare tyre/rim width compatibility ranges.

 

http://www.carbibles.com/tyre_bible_pg4.html

 

Phil

[blade_runner]

I have K&N minators, 6" on the front with 185/60/R13, and 7" on the rear with 205/60R13 with Soft Yoko 48's and the balence on the car is nice, but then my car is lighter then most.

[YellowPeril]

Thanks All.

 

This is really helpful: http://www.carbibles.com/tyre_bible_pg4.html

 

Seems that I might be measuring the wheels incorrectly. They have no markings so I simply measured the external width. The wheels I have might in fact be 6" or 6.5" if I measure from the internal rim so the 185s may just be fine.

 

[Benedict.]

Something else to bear in mind is that manufacturers seem to measure the tyres from different points ( ) or use different length millimetres ❗

Here's a photo I took of a 175 width CR500 next to a 185 width Yoko A021R.

It was even more noticeable in the flesh rubber that the CR500 was wider than the Yoko.

Unless I'm missing something