Tire Squirm Is Terrifying!

Sunroof · 12-10-2003, 01:00 PM

Okay, my rear worn Dunlop Sports were just replaced. I never rotated the fronts for even wearing so my fronts are at the 50% above wear indicators and staying there.

I take the 73 out for a highway spin and its like I get hit with a 100+ cross wind with the car all over the place! My tire guy calls it "tire squirm" and only characteristic in a 911. It will take 500-1,000 miles to scrub it out, but in the interim its like driving lobsided. So, just how can one compensate for this malady?
Add more air to the rears? Buy new front tires to match?
This is really strange and perhaps even dangerous. The tie-rods, ball joints and general suspension is fine. Man this is weird!!

Regards
Bob
73.5T

Rot 911 · 12-10-2003, 01:06 PM

Your so called "tire guy" is full of crap. I suspect one of three things:

One of the tires has tread or cord separation
Lug nuts loose
Some one changed the alignment and you have way too much toe in.

Tyson Schmidt · 12-10-2003, 01:10 PM

He's not full of crap at all. UYou need to get a really hard heat cycle into them by either skid pad, or track. That'll speed up the break-in. The proper solution, though is to buy tires with stiffer sidewalls to begin with.

Wil Ferch · 12-10-2003, 01:14 PM

I second Tyson's opinion...

I replaced rear tires ( only)...Bridgestone S-02's to match the same type fronts.... and they were terrifying for the first 700-1000 miles. I was all ready to have these new tires replaced but I was urged to have patience ( which was wearing thin because I was only a few weeks ahead of my first DE for the year).

Sure enough...at 1000 miles...all went back to normal....

---Wil Ferch

vash · vash's Garage

never heard of tire squirm...

Jamie79SC · 12-10-2003, 01:19 PM

He is absolutly NOT full of crap. I thought something let loose in the suspension the first time I got up to freeway speed with a new set of rear SP8000 on my car. It really scared to poop out of me. It took about 250 miles before they settled down.

Rot 911 · 12-10-2003, 01:23 PM

Well based on the info these guys provided, I retract my full of crap statement. But, Bob, get back to us after 500 miles and lets us know what happened. Personally, I have never had a set of Dunlop Sports "squirm"

Bob's Flat-Six · Bob's Flat-Six's Garage

I put new S03's on the rear of my SC yesterday and could feel the differance from the half worn ones I replaced (went up a size to 245's).
And on the concete Fwy on the way home were they put the squiggly lines in it for traction the back tires wanted to track in the lines and it felt a little squirley until I got to better pavement.

It did'nt do that with the worn S03's So I attributed it to break in.
They just need some hot laps on them

porcupine911 · porcupine911's Garage

(tread) squirm is real. the softer the compound, and the taller the tread, the more pronounced the effect. that's why you really notice it when you get brand new tires.

imagine this is the cross-section of a tire

Code:

   /            \
  |              |
  |              |
   \____________/
    |_||_||_||_|  <-- imagine the tread blocks (softer than
                           the other structure of the tire) squirming
                           under the load of the car

   /            \ 
  |              |
  |              |
   \____________/
                       <-- now imagine the tread blocks worn away.
                               minimized squirm!

another thing to notice when getting new tires is the reduced sterring effort due to a smaller footprint (less rubber on the ground).

masraum · 12-10-2003, 02:06 PM

I believe "tire squirm" is different than the other phenomenon that you often get with new tires. With new tires the tire will often be really slick mostly due to the releasing agent to get the tires to come out of their mold.

I thought tire squirm was the term applied to what happens to the tall tire tread blocks which is why track tires are often shaved.

porcupine911 · porcupine911's Garage

Quote:

Originally posted by masraum
...
I thought tire squirm was the term applied to what happens to the tall tire tread blocks which is why track tires are often shaved.

Tires are also shaved to keep the tread blocks from chunking. This will increase the life of the tire.

See Paul Haney's book for lots of information.

arerrac · 12-10-2003, 02:10 PM

The term I have heard before is "tread squirm" not tire squirm,
Having to do with the size/depth of the NEW tred blocks as they relate to the tire and the ground. Heat cycling will improve feel as will plain old tread ware.
Wade

Jdub · 12-10-2003, 02:34 PM

Great post guys. I had never heard of this, but forewarned is now forearmed.

John

Randy Webb · 12-10-2003, 02:35 PM

Of course, it is not clear how much of the feeling is squirm of the tread, and how much is the lower adhesion in a new tire (tread to road). And some may be squirm of the sidewalls, carcass, etc. as one poster noted.

Stuff in 1st sentence will resolve, in 2nd sentence not really.

DByers · 12-10-2003, 02:42 PM

So Tyson, was that "tire squirm" we were experiencing at the track in the Stay Puff

sscates · sscates's Garage

I just put S-o3's on my 930. I was warned of the new tire syndrom from a shop in North County SD, CA. It was explained as the releasing agent as previously mentioned, not tire squirm. I was told 100 miles was when they will be normal. Hard to tell, because the P7's that came off of it were like skateboard wheels. All is well, now.

porcupine911 · porcupine911's Garage

Quote:

Originally posted by sscates
I just put S-o3's on my 930. I was warned of the new tire syndrom from a shop in North County SD, CA. It was explained as the releasing agent as previously mentioned, not tire squirm. I was told 100 miles was when they will be normal. Hard to tell, because the P7's that came off of it were like skateboard wheels. All is well, now.

Yeah, that release agent helps release the tires from the pavement allright!

geof33 · 12-10-2003, 03:02 PM

One other thing that no one else touched... Check your tire pressures. If you did not state the correct pressures then they were all installed with at least 35psi in them. Definately not correct pressures. this can cause all sorts of wierd things to happen. Even if you did specify pressures, check them anyway.

Tyson Schmidt · 12-10-2003, 03:04 PM

Quote:

Originally posted by DByers
So Tyson, was that "tire squirm" we were experiencing at the track in the Stay Puff

I believe that was just general "car squirm". Mile-high sidewalls and no swaybars make driving that car feel like drunk driving.

The tire squirm (sidewall flex) is also dependant on tire width versus rim width. If you run narrow rims with wide tires it augments the sidewall flex. Using low profile stiff sidewall tires usually makes it unnoticeable. I've felt it with some brands/models and not others in the same sizes.

The tread squirm goes away fairly quickly, and is dependant on firming up the compound by heat cycling, wearing off the sharp edges, and just shortening the treadblocks themselves. And of course burning/scrubbing off the silicone release agent.

Beethoven · 12-10-2003, 03:06 PM

What about vibration? I just put on new Bridgestone Blizzaks, and they make the car vibrate considerably bewteen 60 - 80 mph. Will that wear off too, as my tire guy says, or do they need to be rebalanced?