New snow tires and Rial rims - big problems! [Solved] - Smart Car of America Forums : Smart Car Forum

**jwight** · 11-13-2008, 02:41 PM

Need some technical expertise here (even good guesses will help). Installed the new rims/tires this afternoon, then took the car for a test run. Noticed the braking action and feel was different from the stock set up - firm pedal at first, then the pedal sank a little; not normal.

After about two blocks got the engine malfunction, ABS and brake system lights on the dash and the car lost power (limp home mode?) Got it back home, shut if off, checked for leaks around the brakes (none found) then drove it again - same results.

The wheels & tire sizes are slightly different than stock - 5 in. rims in front, 6 in. rims in rear. Stock tire size in front, the rears are 175/65 vs. 175/55 so a little taller. No TPMS sensors installed. Any ideas? This was a standard tire/wheel swap, didn't go near the braking system and I am lost. Can't get it to the Cincy smart center like this; would have to have it flatbedded down and on my dime if these new rims/tires are causing the problem. Help!

xcrew229x · 11-13-2008, 02:45 PM

Put the stockers back on. If the problem goes away, sounds as if total absence of TPMS is fatal. That would be bad.

**jwight** · 11-13-2008, 02:48 PM

Yeah, that's my next move but I've seen other posts from people running with no TPMS and all they got was the light on the dash. We'll see if anyone has a solution.

Dunerunner · 11-13-2008, 02:50 PM

Put one of the stock tires and wheel in the hatchback and try it. Wouldn't think they have to be mounted! It may have to have communications with at least one or two. Worth a try rather than re-mounting all four stocks.

**jwight** · 11-13-2008, 02:52 PM

Good idea! Thanks.

Padawan · 11-13-2008, 02:52 PM

I hate to be the bearer of bad news, but I'm 99% sure it's the incorrect rear tyre size causing your problems. The owners manual warns about this (not sure the exact wording because I'm still at the office). What is likely happening is that the computer is seeing the front wheels traveling at a different "speed" than the rears, causing the ESP and other electronic safety controls to become confused and go haywire. I'd definitly swap back to the stock setup ASAP and then order the correct rears.

It's not the TPMS.

**jwight** · 11-13-2008, 02:56 PM

This has been debated before; I'd agree, except there are folks running 16 in. and 17 in. wheels/tires with no issues (although I assume they have the TPMS installed too.) Not sure going from a 175/55 to a 175/65 at the rear would be enough to throw it off, but it may be.

Dunerunner · 11-13-2008, 02:57 PM

Ouch...Hope that isn't the problem, but could be!!

mvaldes · 11-13-2008, 03:15 PM

Sorry to hear about your problem. I have Pirelli snows (155/60 and 175/55) mouted on steel rims without the TPMS sensors. I've driven them about 800 miles now without a problem. (I don't count the TPMS light on the dash as a problem.) At least you can elimate the TPMS as the source. Probably remounting the stock rears and seeing if that cures it would tell if it's the tire size or something else.

**jwight** · 11-13-2008, 03:35 PM

Quote:

Originally Posted by mvaldes

Sorry to hear about your problem. I have Pirelli snows (155/60 and 175/55) mouted on steel rims without the TPMS sensors. I've driven them about 800 miles now without a problem. (I don't count the TPMS light on the dash as a problem.) At least you can elimate the TPMS as the source. Probably remounting the stock rears and seeing if that cures it would tell if it's the tire size or something else.

Yep, this is beginning to look like a tire size issue. Hopefully I can swap these rears for the correct size.