Technical tire codes - help needed

[F30Msport]

Can anyone help me decipher these tire codes?

https://www.fiatforum.com/newbie-central/489146-69-fiat-500-a.html

 

[Uaglio]

Sorry - I’m accustomed to the 4 digit week and year date code that you typically see. I don’t know if those are date or other codes. Someone here will likely know.

As far as where to go to change tires, any decent tire shop should be able to handle tubed tires, as long as they are accustomed to a wide variety of wheels. A shop that occasionally does trailer, wagon or power machinery tires would be good for this. A shop that does almost exclusively tire replacements on modern cars may not have a technician familiar enough with tube setups on small wheels to work on this, or may only have tire mounting machines designed for modern cars. These wheels are so small that you may have to use old school tire levers. I’m sure one could do this at home, but tire mounting is one skill I never tried to acquire; never wanted to put in the practice required to get good at the physics of it and assumed I’d just get bloody knuckles every time!

 

[F30Msport]

Thanks! So I have another question. Are the 125r12 tires the stock size? I see people go up a size, but is there any good reason to upsize on the stock rims? And do i need to stick with tube type tires? see the pic of a rim if that helps.


also, the selling dealer is offering to put 155/70/12 tires on the rims...thoughts?

 

[the hobbler]

For a start, if you are using the stock 500 wheels, you MUST use a tube. This subject has been well and truly worked over in this Forum. The 500 (and MK1 '126') wheels do not have the tyre-rim-retaining ridge in the wheel. I would have thought 155 section tyres on a standard 3-1/2in wide 500 wheel would be far too big; you can,however get away with a '135' section tyre. The slightly bigger tyre will increase (slightly) the amount of rubber in contact with the road, and possibly, slightly reduce the engine revs for any given road speed. If you can get hold of a set. the MK1 '126' (594cc) uses the same 190mm PCD wheel-bolt pattern as the 500, but is a shade wider at 4lns, and will definately take the 135 section tyre.

 

[the hobbler]

Sorry, forgot to mention---the Pirrelli Cinturato and similar Michelin tyres, although listed as 'Tubed', can safely run with tubes in them. Somewhere in the Forum there is a copy of a manufactureres letter confirming this point. This will enable you to run radial tyres on your 500

 

[F30Msport]

So they are telling me that a 155/70/12 is smaller than the 125r12. I don't see how that is possible.

 

[LiteRye]

If My memory serves me correct the 2nd number in a tire size is a % of the width. So a 155/70/12 would be a 155mm wide tire with a 108.5mm sidewall on a 12” rim. My research lead me to find that a 125r12 tire has an 80 sidewall which would be 100mm sidewall.

 

[F30Msport]

If My memory serves me correct the 2nd number in a tire size is a % of the width. So a 155/70/12 would be a 155mm wide tire with a 108.5mm sidewall on a 12” rim. My research lead me to find that a 125r12 tire has an 80 sidewall which would be 100mm sidewall.

Thank you. That's what I am trying to figure out, the second (missing) number, which is the aspect ratio, for the 125 r12. 155 still seems way off and likely will be a no-tube off brand tire that wont even work.

 

[LiteRye]

Thank you. That's what I am trying to figure out, the second (missing) number, which is the aspect ratio, for the 125 r12. 155 still seems way off and likely will be a no-tube off brand tire that wont even work.

Not only that but I would imagine a tire that is that wide will not fit correctly

 

[varesecrazy]

If My memory serves me correct the 2nd number in a tire size is a % of the width. So a 155/70/12 would be a 155mm wide tire with a 108.5mm sidewall on a 12” rim. My research lead me to find that a 125r12 tire has an 80 sidewall which would be 100mm sidewall.

I believe its termed the Aspect Ratio

And it is the sidewall height as a proportion of the tread width (in a generalised laymans approach)

Stated as the tyre Width..
then the % Aspect
Then the rim diameter

Eg. 175/65 14 also 155/80 13 common FIAT sizing

 

[fiat500]

If an aspect ratio isn't given, maybe it's just 125 wide and 125 sidewall height?

 

[F30Msport]

So I'm getting all new tires, and leaning towards the Pirellis (125r12). Any reason to get the Michelins instead?

 

[the hobbler]

They are both first class companies with very reputable reputations---it is just that the Pirelli has been made specially for the 500.

 

[F30Msport]

5 new Pirellis and tubes are on their way!