Metric Tire Sizing???

[Car Guy]

I just want to start out by saying I'm pretty well versed in tire sizing and what the numbers/letters mean. Example---195/65R15 94H

I Picked up a set of tires and it says on the sidewall---175R14....that's it. The guy I got them from said, "that's metric sizing." Maybe I've been living in a cave or just haven't come across this kind of tire sizing by chance???

Q1-What does that equal in common tire sizing terms?
-and-
Q2-I thought the example I gave was metric sizing, being that you measure it in metric?

Help me out here, I sort of feel like a bonehead on this one....


Thanks,
Car Guy

[goinbig]

All that will tell you is that the tire is 175mm wide and will fit on 14" wheels. Both are metric (measured in Millimeters--mm) For some reason it doesn't say the sidewall height...maybe someone else can help you more.

[CapriRacer]

Old tire guy to the rescue!

The aspect ratio is - are you ready - 82.

It's an old system, before they dreamed of low aspect ratios. However, there are some vehicles out there that still use this type of sizing, mostly what Europeans call "vans", kind of a small delivery truck.

Hope this helps.

[Car Guy]

So it's really 175/82R14 ??? How do you come up with the 82? Is there a way of finding this or is that just what it is for a '175' tire?

Even if you can't answer these you've helped me a bunch!

Thanks,
Car Guy

[CapriRacer]

How did I come up with 82?

It's just the aspect ratio that was used when this type of sizing was in place. Sort of a Tire guy's trivia question. EVERTHING was 82 aspect ratio - and bias ply, too!

When radials came along, the first sizes conformed to that sizing standard, untill it was discovered that you could use lower aspect ratios with radials and can some very real benefits. We've been headed downward ever since.

Hope this helps.

[Grant@Tirerack]

CapriRacer is correct, odds are if the tires still are listed as a 175r14, they are pretty old. I'd check them out before using them on the road.

[Car Guy]

Actually the tires look fairly new, don't know where the seller got them from though? The name of them are Michelin Rain Force, ever heard of them?

Thanks,
Car Guy

[CapriRacer]

They could have come via the "gray market". The gray market is where Michelin doesn't import them but they arrive here because some guy saw a good price and imported them himself.

So the obvious question is why are you interested in them? What's the vehicle they are intended for?

Last but not least.

You ought to look at the DOT number and see when they were produced.

[Car Guy]

There for nothing special, just a work car(89' Taurus) and the only reason I picked them up is they're like new and were a deal I couldn't pass up.
How can you tell by the DOT number?
Is that date of manufacturing?

Thanks,
Car Guy

[CapriRacer]

First, these tires are way too small for a Taurus. DO NOT USE THEM!!!

uh... Grant... uh..... I'm surprised Tire rack doesn't tell how to decode a DOT number.

DOT numbers, also called serial numbers, TIN (for Tire Identification Number) have between 10 to 12 digits, both numbers and letters. They will always be located adjacent to the letters "DOT", although the letters DOT may be on both sides where the TIN might only be on one of those sides.

The first 2 digits are the manufacturing plant. The second 2 are the tire size. The next 3 or 4 are a code that describes the type of tire uniquely. The last 3 or 4 are the date code in a week/week/year or week/week/year/year format.

So a TIN that ends in 349 means the tire was produced the 39th week of 1999 (or 1989 or 1979). Starting in the middle of 1999 and completed by the middle of 2000, the Date coding changed from3 digits to 4 digits. so a 3499 is 34th week of 1999.

Some obvious clues - if the TIn ends in 1, 2, 3, or 4 and the digit immediately in front is not a 0, then the tire is using the 3 digit format.

Hope this helps.

[CapriRacer]

OK, this web site won't let me edit the message I just posted, but there is an error.

349 does not decode into 39the week of 1999. It decodes into the 34 th week of 1999.

[Car Guy]

That helps alot, I knew there was someway of decoding those numbers! I'll have to look at them and figure it out. As far as being too small, the factory size is 205/70R14 and the tires I got are 175/80R14. Other than the fact that they are alot narrower, the diameter is almost identical. Is that the way(in common tire sizing) my new ones should read....175/80R14?

Thanks,
Car Guy

[CapriRacer]

You had it kind of right with the 175/82R14, but the sizing thing is more about load carrying capacity than physical dimension.

In your case the tires are equivalent to 185/70R14's in load capacity. That's 2 sizes smaller than the OE size.

Hope this helps.

[Car Guy]

Would you recommend that I use them? Like I said it's a work car and was just looking for something that would get me by for awhile.



Thanks,
Car Guy

[CapriRacer]

I think I made my recommendation about their use quite clear.

DO NOT USE THEM!

You'd be better off with the $ 100 specials, than tires that are too small.

Ever hear the story about the lady who went to the shoe store and insisted that the store sell her size 4 shoes for her size 6 feet, and then later returned the shoes because the fell apart and she twisted her ankle? At 70 mph, tire failures can cause more than a twisted ankle.

Hope this helps.