urquattro20Vt

So today I went for a nice drive - 300+ miles - mix of curving two lanes, some highway, a few mountain passes...

But the car just didn't feel right.

It was unstable at speed. Uneven road surface would move the car around. When passing slow moving traffic and I had to pass over the road's crown - it would hesitate then as one side got over it would dart over too fast. I felt like I was all over the road.

At first I thought tire pressures were off - double checked and they were fine (36F/44R).
Then for a while I was thinking the alignment was off. But it brakes straight and accelerates straight. And it was fine a few weeks ago.

Then I got thinking about the tires. I just put new 285/35 Michelin Pilot Super Sports on the back - replacing a previous set (which I really liked). I took me awhile to figure this out - but the way the car was handling brought me back to when I first got the car and tried some Hankook tires. They were not good. At all. It was like the car was today (but worse with the Hankooks)

The first set of Michelins was awesome but with the new rears - something has changed.

What are people's experience running new rears with old fronts (Michelin Pilot SS's up front, too)?

There's no N rating to watch, right?

I'm wondering if the half used up fronts are "stiffer" with less tread compared to the new rears with full tread depth and it's throwing the balance off?

I thought it was common to replace rears and not fronts..?

Any thoughts appreciated.

Thanks

Brandon

LexVan

How old are the fronts?

You need about 500 miles on the rears to scrub off the mold release. You might be feeling that.

urquattro20Vt

Fronts are 4 yrs/15,000 miles.
Car didn't have these issues when the whole set was new...
And after todays drive there can't be any mold release left - they got a work out! Car was just as bad at the end of the drive. And really only above 60/65.
Weird. In a bad way....

LexVan

Buy new matching fronts. Get a quality 4 wheel alignment. Does the 964 have kinematic toe? Back your rear tire pressures down to 40.

bweSteve

I agree. It's your fronts.

I drove a mix & match fronts/rears during the Michelin Driving Experience last week up at PCA Parade at the Jay Peak Autocross. And wow, I was all over the place on the mix&match.

Then drove the 2nd car with both Michelin PSC2's on the front & rear. I could really feel the difference.

Maybe some folks would not feel the difference when keeping 4 yr old rubber up front, but clearly you can.

Get new fronts to match.

=Steve

urquattro20Vt

I think that's what it is, too. Disappointing. I've driven a true mix match, and a crappy/budget non mixed set - and both were horrible. The Michelin PSS were great - a bummer I have to replace only half used fronts... :-(

bweSteve

yep, one of the few things I don't like about staggered front/rear sizing, along with the inability to rotate, and the waste of discarding fronts that still have life in them.

BUT, it is the staggered front/rear stance of our cars that gives them such sex appeal !!! and such an aggressive look & incredible to drive,... yes?!! .... so we forgive our 964 Turbo's. C'est La Vie'

My take on it... there are plenty of little rice burners out there, running crap loads of camber,.. that will buy those fronts from you at a nice little penny on the original dollar.

Put em on Craigslist. My last pair of 225 x 18's sold in a matter of days.

maverick

Did the same thing on both the 964 and 997......now I'm a firm believer in all four at the same time.....tires are the cheap part between us and the road.....not worth the few $$$ saved...maybe on your daily beater but not on a high performance machine.

Igooz

urquatt..., could it be wheel balance? Otherwise, probably a mismatch on tires. I have been driving 911Turbos consistently since 1994 and I always buy two rears - then all four - repeat. I've never had an issue.

By the way, I was back home in CO that same weekend and went for a drive on the backroads: Lyons/Nederland/Boulder/Estes area...this time of the year a lot of slow moving tourists.

urquattro20Vt

I have new 225/40 18 Super Sports on order and they should be here any day. Will let you guys know what results.

AC/911's

285/35 is taller by at least .5 inch...

urquattro20Vt

Yes they are. Not as many size choices with the Super Sports. Wish they had 295/30.....

Not uncommon to run 285/35 on the rears....
They make up for the short gearing! ha

urquattro20Vt

Ok so closing the circle (pretty much)on this one. Got the new 225/40/18 Super Sports (fronts) mounted and the issues seem to be gone. I say "seem" only because I have not had a chance to get into the mountain twisties - but on a highway drive (where the issues also occurred before) the car seemed normal. Not darting with surface irregularities or inconsistent turning behavior.

If you run Super Sports - I guess I'd recommend replacing all 4 at the same time.

If I find the car isn't handling as it should next time I do a canyon run I'll update here.

bonehead

Brandon
Any update on the handling after the front tire change?

Could you also tell me what size wheels/offsets you're running with a 285 in the back? Speedlines (or reps) I'm assuming? Is your car lowered and did you have to tweak the camber to prevent rubbing? Thanks.

urquattro20Vt

Hey Ed-
Yeah - to confirm - the new fronts cleared things up. So if you put new Super Sports on back - I have to recommend fronts, too. I run the factory 3.6 Speedlines - not reps. Can't recall offhand the ET but I'm thinking either 57 or 62? I do run a 4 or 5mm space in back because the car came with them - and it pushes the rears out just a little more to fill out the wheel wells. My car is lowered on H&Rs and I did nothing to camber or anything. That said the car had 285/35 PS2's when I bought it - but I don't think the tire size necessitates and changes to anything, frankly. No rubbing.