I just got some 215/45/17 Kumho mx's put on my Gram Lights. And I have been having few problems with them. Im trying to figure out if its the tire, or a bad mounting/balancing job.

Befor these I had Falken Azenis.

The first thing I have noticed is I get alot of vibration in the steering wheel. And it gets real bad over 80mph. Its a real fast rattle, so I wasnt sure if it was just the tread pattern.

Second one of my tires is losing air, after a week of driving.

And today, after filling up the the low front tire. My abs kicks in under somewhat hard breaking. On dry even pavement. I have stopped much harder on other tires and never had this problem.

Also on my way to work this morning I was going around a long turn, about 45-50, then it felt like the right front (not the tire with the leak) tire just gave out, or rolled over. Alittle scary.

Any Ideas? I purchased the tires from tire rack, and had them installed at a subaru dealership. What would I do?

Thank You
Anthony C

What tire pressure are you running?
I auto-x'd an mx's and I found the sidewall to be somewhat cushy, but that is comparing them to AO32R's which were my previous auto-x tire. It wounds like a bad mounting job for most of your issues. Wheel weights may have not been stuck/hammered on properly or just not done right. And perhaps the bead didn't seal properly or they may have cut the tire installing it (shouldn't happen as it is a fairly easy tire to install,unlike slicks or a gravel tire). Also the ABS, unless it was in rain, slippy or bumpy roads I never had my ABS come on with my MX's. I'd take them back to the dealership and tell them to check for leaks (or do it yourself with soapy water) and tell them they are not balanced properly. Also, you should get an alignment done on your car after installing new rubber.

I had a set for 20k miles. I had them up over 120 mph on multiple occasions and autocrossed them every month. No problems what so ever. I liked them. Sounds like the dealer did a crappy balancing job. Take them back to the dealer for a re-balance and possibly a re-mount of the one that's leaking.

I just got some 215/45/17 Kumho mx's put on my Gram Lights. And I have been having few problems with them. Im trying to figure out if its the tire, or a bad mounting/balancing job.

Befor these I had Falken Azenis.

The first thing I have noticed is I get alot of vibration in the steering wheel. And it gets real bad over 80mph. Its a real fast rattle, so I wasnt sure if it was just the tread pattern.

Second one of my tires is losing air, after a week of driving.

And today, after filling up the the low front tire. My abs kicks in under somewhat hard breaking. On dry even pavement. I have stopped much harder on other tires and never had this problem.

Also on my way to work this morning I was going around a long turn, about 45-50, then it felt like the right front (not the tire with the leak) tire just gave out, or rolled over. Alittle scary.

Any Ideas? I purchased the tires from tire rack, and had them installed at a subaru dealership. What would I do?

Thank You
Anthony C


...somebody borked something....are all the tires mounted in the correct orietation???
You may need more air pressure, too....40F/38R is a good place to start.

Also, if your tire is losing air and you can't find any nail/screw in the tread, check the valve stem. I was losing air out of a right tire, and I didn't find the culprit until I pushed the rubber valve stem back a little and air leaked out of it. I ran the MX's (235/45/17) with 40F/39R when I had them on my STi.

-Mike-

how many miles are on them? if they are still fresh (like under 500 miles) that will explain your perceived lower traction as compared to the old tires. They are always greasy when new.

Your vibration problems sounds like one of the wheels is out of balance.

Well the leaking air turned out to be the valve stem, Im not ure how you put a hole in an aluminium valve stem but it leaking from the threads where the cap skrews on.

They do have less than 500 miles, so I will have to order a new stem, and give them alittle time.

Are you guys running 40F/39R daily? do you go any higher for autox?

Thanks for the help!
Anthony C

that's a good pressure to start for auto-x (maybe a couple psi higher), as it will go up as the tires warm up. I've found 46psi front pressure on those tires (245/40 17 size) to be the upper limit with my setup. After that, they skip a little bit when pushed instead of sliding smoothly. That's different for everybody, though. Did you take the wheels back to the dealer and give them an earful?

Hope to see you out at Fed-ex field in a couple months.

Tighten the valve on the inside of your valve stem. It's probablly just a little loose. I had this problem once or twice with a set of aluminum valve stems.

That should fix your leak, if it doesn't take them back to the installer.

Eitherway your vibration sounds like a balance issue.

A bit OT, but do the MX's have stiff sidewalls? Someone above mentioned they felt mushy, but that was relative to a race tire.

I've autoxed mx for while and never experienced anything like that. Must be the mounting job, stem or something else.

Hope to see you out at Fed-ex field in a couple months.

If I can get the leak figured out this week, I'll hopefully be able to test them out at the Pilly region autox at ripken stadium this weekend.

Anthony C

A bit OT, but do the MX's have stiff sidewalls? Someone above mentioned they felt mushy, but that was relative to a race tire.
I would also like to know ..?

They are stiff enough for mostly everything, but...they are not as stiff as the rock-hard Azenis sports that they are sometimes compared to. They are also almost 20% lighter than the azenis...
Personally, I would have liked a slightly stiffer sidewall for autocross.