Tire time - complicated issue

[POS]

The stock tires on my 500SL were 205/70/14s. But when AMG got ahold of it, I now have 225/50/16s. Complications are that even though the revolutions are similar, the speedo still reads too a few mph too fast at 75.

Two choices:

1) stick with the 225/50/16s because I know they don't rub, and just deal with the mph/speed issue, or
2) bump to 225/55/16s, take a gamble on the rubbing, and help solve the mph/speedo issue.

I think I'm going for the Michelin Pilot Exalto A/S. Front rubbing isn't an issue; here's a pic of the rear:


Anyone got any suggestions or thoughts?

[suginami]

The stance of your car is dead nuts perfect. The combination of it being lowered with the bigger tires and low profie tires looks sweeeet.

[Bill Wood]

Take a look at the Tire Size Calculator we have in the DIY Wiki.

The 225 50 16's are 1.7% shorter than the stock 205 70 14's. That means at 75mph your speedo will read 76.3mph.

The 225 55 16's are 1.8% taller than the stock size so at 75mph your speedo will read 73.7mph.

[POS]

Using the tire calculator at http://www.miata.net/garage/tirecalc.html, I get the opposite results.

225 50 16s are 1.7% too fast, meaning 60 is really 59
225 55 16s are 1.8% too slow, meaning 60 is really 61.1

[eagle-co94]

Have you considered a 235 50 16? It's darn near perfect for speedo correction. Availability is an issue though. Tire Rack and Discount Tire don't carry that size...but edgeracing does: http://edgeracing.com/tires/2355016/

[Bill Wood]

Originally Posted by POS

Using the tire calculator at http://www.miata.net/garage/tirecalc.html, I get the opposite results.

225 50 16s are 1.7% too fast, meaning 60 is really 59
225 55 16s are 1.8% too slow, meaning 60 is really 61.1

No. it is saying exactly the same thing.
The 225 50 16's are shorter by 1.7% so that means they turn more revolutions to travel the same distance as the stock tires. This means that the speedo will read HIGHER than you are actually traveling. At at 75mph your speedo will read 76.3mph as I said.

[POS]

Oh, yeah, you're completely right. You are saying the same thing. Thanks!

[kutza]

I suggest, Leave the 225/50 on there, you really not going to correct the problem with going with a 225-55 tire, just the other end of the speedo error. In plus sizing, there is a margin of error it is (+/- 3%) and you are well within that. Also if you go taller in tire height, techinally your gearing will change, losing bottom end touque, and gaining top end speed.

[POS]

I saw a w210 with the 18" Monoblocks on it today in a parking lot, and thought - I wonder if I can get those in 17"s. Maybe I'll just do that so things don't get complicated.

[Lexxani]

I'd go with the 55 series, you'r loosing a little tread height. I do not believe you'd encounter any rubbing issues as it is a shorter tire. Good choice on the Pilot Exalto A/S. . .I ended up purchasing a set for my ES ( I was looking for Energy MXV4's, but thoes are discontinued in my size) and I have been quite pleased in ride quality and wet pavement handling, only thing I wish was a little more trade life, but thats the trade off when you buy premium tires. . .

[Lexxani]

wow, i mistakenly read "60" series. . my post should read stay with the "50" series. . .