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Pardon me if I've asked this question before. CRS syndrome is getting pretty bad...

Most of our 124s came with 195/65-15 tires on 6.5x15 wheels. According to the Miata site tire calculator this setup has a 5.0" sidewall height, a 12.5" radius, 25" diameter, 78.5" circumference, and rotates 807 times per mile.

I see a lot of people running 205/60-15 tires on the stock wheels and the specs for this tire are 4.8" sidewall height, 12.3" radius, 24.7" diameter, and 77.6" circumference, giving 817 rotations per mile. Fine. Good. No problem.

But looking further at the tire calculator site I see that the 215/60-15 tires have specs even *closer* to those of the original tire: 5.1" sidewall height, 12.6" radius, 25.2" diameter, and 79" circumference, giving 802 rotations per mile.

So if the 215/60 tire is closer why aren't tire stores recommending it and/or people selecting it on their own? I figure there must be a reason but I'm not up on tire and wheel fitment issues. I figure that someone here will know the reason.
 

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I think the 215/60 would probably cause too much wear on the tireshoulders.

My diesel finally got new skins last Friday, and it got 195/65-15s again while the previous set were 205/60-15.

The 205/60-15 Michelins were showing some wear on the tireshoulders, not too excessive despite the alignment being right on the money at all 4 corners. They lasted about 45K miles.

The new Pirellis have a treadwear rating of 600. Will keep you updated as the miles roll on.
 

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Why would the 215/60s wear on the shoulders? Is the 6.5" wheel too narrow?
I think that is one of the reasons. I noticed with the new Pirellis on the same rims that the outside edge of the rims is now pretty much even with the outmost portion of the tire. Also, the flat portion of the outer edge of the rim is now fully exposed which was not the case with the 205s.

With the 205-60s the tire stood out a bit more. I would assume putting on 215s would do that even more and would probably cause more wear on the tireshoulders.

The other thing is that these W124s, like my previous W123s, w116s, W126s and so forth seem to do much better with tires that have a very stiff sidewall.

My W116 6.9Liter used to chew through standard tires like there was no tomorrow, always wearing extremely fast (less than 10K) at the tireshoulders. That issue was resolved simply by using better tires with very stiff sidewalls found in the better brand tire offerings. That car liked Michelins & Pirellis the best, and that's what I have observed with the W124s as well.

FWIW, the Michelins 205s lasted about 45K, which I think is pretty good for a relatively heavy car. The new Pirellis, with the higher treadwear rating of 600, should do just as well if not better. There is no noticeable increase in tire noise despite the higher treadwear rating.
 

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215/60s are a great idea, I've done it a couple of times. They are closer to original than the 205/60s that so many people do. 205/65s are fine too, if you want a little taller gearing.
 

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I don't know if this will help, but I have many years of experience cramming as much tire onto small wheels as I possibly can. SCCA Stock-class autocross requires us to use stock-sized wheels, but we can use any size tire. I've used 245s on a 7" wide wheel, and 275s on an 8.5" wide wheel. I've also seen people put 275s on a 6" wheel. :eek: It's not optimal, but it has been done. And not for the reason you'd guess. ;)

There's no hard and fast way to know how a wider section tire will wear differently on a same-sized rim, particularly when changing tire manufacturers and even tire models. One tire might respond differently to being "pinched" than another will. For instance, a lot of people claim that wide tires on narrow rims cause the tires to balloon up - that is, the tread surface becomes more rounded and less flat. This would lead one to believe that the centers, not the shoulders, would wear more. But that's not necessarily how every tire behaves.

Also, one manufacturer's 195 can be a different width (in real world measurements) than another manufacturer's, especially once mounted. My race compound Hoosier 245s are *far* wider than the 245 street tires I have for the same car. Yet DOT approved them both, both listed as 245s. Similar situations exist among street tires. I've seen guys run 195 street tires that are easily wider than 205s from a different manufacturer.

There's also availability to consider. Tire Rack lists 29 different 215-60-15 tires once you take out the one "track and competition" model. In 205-60-15, that number grows to 47. In 195-65-15, the number swells to 79.

Personally, I'd consider doing 215-60s if the tire I wanted is available in the size. It's not a massive tire on a 6.5" rim. Given a tire with a stiff enough sidewall, it would probably feel really good.
 

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Vehicle weight versus tyre width must be a consideration.

That is to say, every square inch of tread in contact with the road needs a certain ammount of weight upon it to make it grip. MB must have done the calcs at design stage. If we go wider than spec., then is there not a danger of loosing grip?

My 320ce slides all over the road currently with it's stock 205, 60, 15 tyres but then are they not famous for that even with a full tank?

Boyd :)
 

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My 95 E320 originally came with 195-65-15 when they worn out I put 205-65-15 always Michelin MXV4 until now the 3rd sets and 221KMiles on the clock no problem with it.
 

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Putting wider tyres on will not make the car loose 'grip'.
It will slightly increase rolling resistance at the most.
I have 225/40/18's on my 124 coupe and believe me, i get a hell of a lot more traction than the spec tyres and wheels.

I understand that a 'pinched' tyre will behave differently than a standard fit, but from experience a pinched tyre proves to act as a softer tyre and improves friction with the road surface, not reduce it.
 
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