Best tire size: 74 2500M

[Renaldo]

Guys, my tires are nearly ready for replacement and I'm wondering about optimum size.

Currently, I've got 206/60/14s all around. I think the factory delivered size was 185/60/14.

The 205s are a little harder to find where I come from.

Do you think I should stick with the 205s? Is there some benefit to going to either a wider or narrower tire? Any other good options?

Your thoughts?

Ron

Edited by Renaldo on Friday 21st December 18:28

[bluezeeland]

My thoughts are that orginals are 185/82(full height)/14, which are hard to find/expensive, but working very well (got michelin' VXY on mine) on handling and so on.

[DavidY]

On 14" Rims M' series cars were fitted with 185s 82 profile, the Turbo cars were fitted with 195/70s

[Renaldo]

So, do you think a lower profile (the "60" for example) may not be the best for overall performance?

Sounds like the factory choice, was a higher (taller) sidewall than that.

Ron

[bluezeeland]

er, yes, and er, yes....

[DavidY]

Ideally a 205 should be on a 7J rim, this makes best use of the sideways and stops so much movement laterally of the tyre on the rim. Most M's had 6J rims, so a 185 or 195 will be a better fit. Don't put on 185/70's though as they are too small, and just don't look right.

[Renaldo]

Thanks guys.

Actually, the 185 and 195s are somewhat more available where I am. Don't know about the 82 sidewall, but the 70 should be available.

Just to confirm (and to repeat): you'd recommend the 195/70/14 is a better choice overall, than the wider, lower profile I'm using now?

Ron

[DavidY]

Given the choice I would go for 195/70s

[Renaldo]

David, thanks for the advice!

Ron

[TA14]

Renaldo said:

Just to confirm (and to repeat): you'd recommend the 195/70/14 is a better choice overall, than the wider, lower profile I'm using now?

Given what you've said above I'd go with what David has recommended (195/70/14)
The 6" rim will tend to float across the tyre foot print laterally with the 205 tyre.

Now if you splash out on some 16 x 7 rims then you can fit 205/55/16 all round and have great tyre availability but that's quite an initial outlay.

[Renaldo]

Jonathan, thanks for weighing in. Bigger wheels may be in my future too. But for now, glad you've confirmed the 195/70s are a good choice.

Ron

[TA14]

And given this time of year maybe good for a winter tyre fitment.

Merry Christmas.

[GAjon]

A lot Depends on what you intend to do with the car.

205 x 60 x 14's are fine for normal road use and arn't that bad on track, not the best but not bad.

Davidy is correct about the fact they are a bit to wide for the rims, but its not critical.

I ran them for a bit a long time ago (before major mods), but my main decision driver was I thought they looked better, bear in mind a 205 tyre was a wide tyre in 1980.

[RCK974X]

Renaldo - in case you didn't know, a low profile tyre is actually smaller than full profile, so your speedo reading will be affected. (80 or 82 is a full profile tyre)

One tyre size measure is 'turns per mile' and here is an example -

tyre [turns per mile]

185x14 [817] (which is 80 profile)
205/60x14 [877]
185/70x14 [894]
195/60x14 [898]
185/60x14 [917]

So it's worth asking you tyre supplier about this to make sure your speedo isn't affected too much. I just hate speeding tickets !

[Renaldo]

Andy, my speedo is definitely out of wack -- due, I imagine, to the 205/60s.

So, if I understand correctly,that problem will be partly addressed with the move to, say, a 195/70?

Ron

[phillpot]

this might come in useful

[RCK974X]

That looks like a good link, I'll keep that !!

Also good tyre suppliers should have turns per mile info in their manufacturers data catalogue.

There is a calculation, but it isn't always dead right due to manufacturing differences (how much side wall distorts etc) but here it is -

tyre Specs are WDT/ASR-WHS

Where:
WDT = Thread width in mm
ASR = Aspect Ratio ratio (number)
WHS = Wheel size inches
then:

Rolling Diameter = 3.14159 x [(WDT x ASR/1270) + WHS]
i.e dia of wheel + two hieghts of tyre......
turns per mile = 63360/Rolling dia

63360 = inches per mile but 65261 works better (3% derate for tyre wall)

Edited by RCK974X on Friday 21st December 21:36

[phillpot]

RCK974X said:

That looks like a good link, I'll keep that !!

But no blaming me if you buy the wrong tyres

[DavidY]

If you getting down to the nitty gritty then there is the 8mm of tread to consider against 2mm of a worn out tyre. makes a difference to the rolling circumference!

[Renaldo]

Guys, just to give you an idea, here are a couple of photos of my car with the 205s...