New tires...but now the rear end feels "loose".

[ditch68]

I just replaced the terrible tires which came on my car at purchase, a long time coming.

It came with Fuchs 7s and 8s, with 205/60/15 all the way around - the fronts weather checked weak tread BFG, the rear Big O crapola.

Well, I shod it with Goodyear Eagle GTs, 205/60/15 front, and 225/60/15 rear.

I got the tires on, and the next morning, headed out on a 200 mile drive on the freeway, and the rear end immediately felt "loose" after getting up to highway speed, it felt like a tire was going down. All tire pressures are fine at 45 PSI.

It is hard to describe - if I make a quick in lane directional change, or jerk the wheel slightly, the car turns, but then the rear follows, and feels like it makes an opposite overcorrection in the rear afterward. It seems like a long lag between the steering input, and this "wag". I have never felt anything like it.

It feels (in an overall sense) like the car is not turning in with front wheel input, but pivoting in the center, like right under me, and then the over correction follows.

At lower speeds, the car clearly has more traction in corners, but it still feels unsettled.

I don't get it. The crappy tires actually felt better, aside from the staggering lack of traction. It felt awesome before. Odd.

I am guessing I have a rear end toe in issue, but why would the new tires exaggerate this so much? Going to go with a 4 wheel alignment, I suppose. I hope the car will feel "tight" again. It is just not fun ti drive like this!

Thanks in advance,

Jeff

[Oh Haha]

Drive a few hundred miles to wear the "new" off of them and then report back.

Many of us have had the same issue with new tires.

Yes, it is very unnerving.

[Chaos Theory]

seems like tire pressure is a little high as well..

[ditch68]

Well, the shop installed the tires all at 25PSI, way low. I upped to 45, max pressure on the tires is 51. At first, I thought low pressure when I drove it home. So I checked, and saw the 25psi. Pulled into a gas station, and aired up to 45. No change whatsoever, same soupy feeling.

I have driven around 450 miles now, it still feels like this, but I am getting used to it, I guess. If that is possible?

Jeff

[James Brown]

yes sounds like the tire pressure is way high, try around 30 psi. Drive gently the first hundred miles.

[Peter Zimmermann]

45 psi????????? Are you kidding? If your car is an SC/3.2 Carrera your pressures should be 29F/34R, or 29F/36R (Carrera) - cold.

[Chaos Theory]

Originally Posted by ditch68

Well, the shop installed the tires all at 25PSI, way low. I upped to 45, max pressure on the tires is 51. At first, I thought low pressure when I drove it home. So I checked, and saw the 25psi. Pulled into a gas station, and aired up to 45. No change whatsoever, same soupy feeling.

I have driven around 450 miles now, it still feels like this, but I am getting used to it, I guess. If that is possible?

Jeff

I like to be somewhere between 29 and 31psi front and 32 to 34 rear depending on temp/road conditions etc.

I think you were running too low before, and too much now. Perhaps that loose feeling you were experiencing at the beginning was due to the 'release agent'/slipperiness of the tires initially and now they are a bit like rocks.

Try a happy medium with a bit less pressure in the front to help them 'bite' a bit more, and a bit more in the rear to handle the drivetrain/rear engine layout.

perhaps others have different ideas?

edit: Pete beat me to it.. What he said.

edit #2: I think your rolling dia is off in the rear, but I could be wrong..

[ditch68]

Yikes. Sorry. I'll air them down to 29/34. Didn't mean to give anyone a heart attack.

I'll do this immediately, thanks.

But like I said, pressure had little to do with the feel. AND, I have 450 miles on the tires.

I'll report back tomorrow, but I think it may be alignment??


Jeff

[Emission]

Full depth tread (new tires) will "squirm" more than old worn tread tires. It happens on all cars... perfectly normal.

- Mike

[Peter Zimmermann]

FYI:
Well, I shod it with Goodyear Eagle GTs, 205/60/15 front, and 225/60/15 rear. The rears are OK, but Porsche recommends 195/65 for the fronts. That said, you should be able to play with pressures a little to come up with OK balance. Goodyears are certainly not a preferred tire, many other brands perform better. 450 miles might not be enough time for them, where Bridgestones are ready for an autox at less than 200 miles.

Alignment would not have changed with tire replacement, did you examine your old tires when they were removed?

Had another thought. Many years ago a customer came into the shop and complained that his car had not felt "right" since he had tires put on. I looked at his car and immediately saw that on one side of the car the 6" wheel was on the rear, and the 7" wheel (the car had 6&7x16 rims) on that side was on the front. And one of the uni-directional tires was mounted backward. Ooops! Did you check for that (no insult intended, unless you're actually looking for it you might not see it)?

[regency]

all good advice, I'd still take the car in to get front & rear aligned and check the toe in, also front & rears.

Prior to installing my new Fuchs & Tires, I took my car in and it was Way out in every way. They aligned and corrected the toe in. On the way home, merging onto the Fwy, I could really tell the difference. Best $160. spent on the car.

Aubergine 73 911 T MFI Coupe built to E spec. with Weidman Deep - 6's Fuchs front & custom Deep 7R's on the rear.

[equality72521]

Eagle Gt's are also really hard tires.

[Chaos Theory]

Tire Pressure Sticker

saw this and thought of you

[stevie 77 930]

New tires have a way of exposing bad shocks ....

[Mike(LaCanada)]

I'm curious what tires you had before and what the treat pattern was like. I've found that the tires with the more wet tread pattern tend to have that kind of feel to them. I had a 993 convertible for some time and we went from the stock Pirelli PZERO to the Bridgstone SO-3's and the car did the exact same thing to me. Even after a lot of driving that feeling never went away.

Just my 2 cents.
Mike.

[AHartz]

I replaced just my rear tires with the Goodyear GT's and had exactly the same "loose" feeling. The traction was great, and the ride was smoother (bumps were not felt as much), but just felt like the back end was not as responsive when going side to side. I put about 1000 miles on them and no real difference.

I'm subscribing so I'll hear if there's any other suggestions. I also suspect that the new tires are showing how bad the shocks are (I don't know when the current shocks were installed).

1981 911SC Targa

[chrisgo17]

I had the same experience with Eagle GT's on the rear. Tried adjusting the pressure from 28-32. Normally run 30 PSI. Never felt that on any previous Tires. Is it possible that there is excessive Tread height, therefore flexing?







"I looked for the hole to jack in some wedge, but could not find it."

[ditch68]

Thanks for all the good advice.

Interesting that others have had difficulty with this particular tire. I had a new set on my 924S before I sold it and got the 911, and they seemed fine on that.

I suppose I am feeling what is likely a combination of the tires themselves being new, worn shocks (I am sure they need replacement) and some alignment issues.

I'll plod through all that and report back.

Oh, Chaos - I certainly deserved the sticker post!

Jeff

[kwikt 911]

It could also be tire flex from thin side walls construction. I ran into that problem with a cheapo set of tires.

[redranger]

Air pressure definitely too high, my manual says 36 rear/29 front. Check to see if your tires have a rotation arrow on the sidewall and make sure they are on the proper side of the car.