General Tyre Size for 12" Rims?

[Pete145]

Hi everyone.

My tyres need a change. I've been running 145/70 R12s on the Mille Miglia wheels which you can buy from Ricambio (other retailers are available). They really do fill the wheel arches, though, and I do have the occasional issue with wheel arch rub if I've cornering at the right speed/road camber/acceleration. It's marginal, so I'm hoping that a set of 145/60 R12's might fix this.

I've found a useful website gives some data comparisons on all sorts of things between tyre sizes, and the lower profile will reduce the overall diameter by over an inch.

I'm aware that the speedo/odometer will be impacted, but the good news is that my speedo reads a few MpH too fast, and moving to the smaller circumference of tyre will actually fix that rather than make it worse.

Does anyone have any experience of running 145/60s before I go ahead?

 

[Noah500]

** I haven't run anything other than standard size tyres but from a quick calculation I did I think that the width is more likely to be the problem for you than the profile: the 145s are nominally 2cm wider than the standard 125s i.e. overhanging 1cm extra each side of the wheel body. If you go for 60 profile 145s, you may get more wheel arch clearance due to saving 1.3cm from tyre to wheel arch but the you will also have 1.3cm less ground clearance and the speedo will read a fair bit under than with the standard tyres. I think some people run 135s

Tyre width mm	Sidewall profile %	Sidewall height mm	Wheel diameter inches	Wheel diameter cm	Notional tyre diameter cm	Diameter difference from standard %
125​	80%​	100.0​	12​	30.48​	50.48​	0.0%​
145​	70%​	101.5​	12​	30.48​	50.78​	+0.6%​
145​	60%​	87.0​	12​	30.48​	47.88​	-5.2%​

** All 'In my opinion only'

 

[Pete145]

** I haven't run anything other than standard size tyres but from a quick calculation I did I think that the width is more likely to be the problem for you than the profile: the 145s are nominally 2cm wider than the standard 125s i.e. overhanging 1cm extra each side of the wheel body. If you go for 60 profile 145s, you may get more wheel arch clearance due to saving 1.3cm from tyre to wheel arch but the you will also have 1.3cm less ground clearance and the speedo will read a fair bit under than with the standard tyres. I think some people run 135s

Tyre width mm	Sidewall profile %	Sidewall height mm	Wheel diameter inches	Wheel diameter cm	Notional tyre diameter cm	Diameter difference from standard %
125​	80%​	100.0​	12​	30.48​	50.48​	0.0%​
145​	70%​	101.5​	12​	30.48​	50.78​	+0.6%​
145​	60%​	87.0​	12​	30.48​	47.88​	-5.2%​

** All 'In my opinion only'

Thanks for your reply. My speedo reads over, so that doesn't concern me too much. According to Ricambio these wheels can run 145-165 tyres, so I'm reluctant to drop down to 135s unless they confirm that I can. I'll drop them a note and see what they say.

 

[the hobbler]

Thanks for your reply. My speedo reads over, so that doesn't concern me too much. According to Ricambio these wheels can run 145-165 tyres, so I'm reluctant to drop down to 135s unless they confirm that I can. I'll drop them a note and see what they say.

It might help you fit slightly larger tyres if you fitted Mk1 '126' wheels---they are 4in x 12in as against the 500s which are 3-1/2in x 12in. The Mk1 126 wheels had the same 190pcd wheel-bolt pattern as the 500 (the 652cc, mk2 went over to the standard Fiat 98pcd wheel-bolt pattern)

 

[Dougal Cawley]

Pirelli now make the proper 125R12 Cinturato.

But they also make the 145/70R12 as well

125 R12 Tyres

125 R12 Tyres. The perfect classic Fiat 500 tyres are 125/80 R12 Pirelli Cinturato. Get the best 125 R12 tyres from Longstone Tyres. Call +44 (0) 1302711123.

www.longstonetyres.co.uk

They can both be fitted with inner tubes if you are not sure that your wheel is suited to being run without an inner tube.

we can also go super swanky with a set of Borrani wheels

Fiat Nuova 500 Wheels

Fiat 500 Nuova Classic Tires & Wheels. Borrani alloy rimmed wire wheels, 125SR12 Cinturato CA67 Tires for the Fiat 500 Nuova. Call +44(0)1302711123 for more info.

www.borrani.com

 

[Peppone]

I personally swapped from 155R12 (horror) to the Pirelli 125R12 Cinturato. A real change and pleasure, and Peppina looks cooler (and safer).

 

[Dougal Cawley]

I bet its miles nicer to drive.