New 215 tires on 400E stock rims.
 

Just removed the stock 195 tires from my 92 400E, and fitted 215/60R15 tires on my 15" stock rims.

All I could say is that they fit perfectly, the stock rims are 6.5" wide, most of the 215/60R15 tires can fit 6-7" wide rims.
Actually when Michelin calculates the section width for their 215 tires, they use 6.5 rim, that means the 6.5" rims are quite normal for 215 tires.

For those who don't want to invest extra on new rims, I would strongly recommend 215 tires on stock rims.

I put Michelin Arctic Alpines on my car, though I know the performance on snow degrades with the fatter snow tires, but it definitely greatly improved my overall dry road handling, also my 400E looks much better than before.

I have 225/60s on my 15x6.5" wheels and they seem to work fine. http://www.miata.net/garage/tirecalc.html says the speedo should be within .5%. My nautical vocabulary is insufficient to fully describe the previous proper size Bridgestones.

Sixto
91 300SE
81 300SD

From the margin I have with the 215/60R15 tires, I think 6.5" rims should fit 225/60R15s without too much problems, just the speedometer will be a little bit off (2.6% slower than actual), 225/55R15 could be better.

The tolerance that I heard was +/-3%, I think even new and worn out tires may bring 2% difference.

I should mention that the stock 86-91 W126 tire size is 205/65-15, not 195/65-15 like most W124s.

Sixto
91 300SE
81 300SD

Awesome.

Carman850, do you have any before / after pictures that you could post?

Dennis,

I don't have a digital camera, but I am going to take some pictures and scan them, you have to wait for several days.

It looks very aggressive from front and rear, 215s really fill the wells much better, no change from left and right, because the section height is the same as before.

Carman850,

No rush. I'm in the same situation. No digital camera. However, I have two little kids and we go through at least a roll of film a week. Then I scan them in. It's a pain.

Don't go through the trouble just for me, but I think others will be glad to see the result too. If you post pictures, they will probably be referenced in many future threads...

Thanks.