986 Forum - The Community for Porsche Boxster & Cayman Owners

986 Forum - The Community for Porsche Boxster & Cayman Owners (http://986forum.com/forums/index.php)
-   Boxster General Discussions (http://986forum.com/forums/forumdisplay.php?f=5)
-   -   tire moving on rim at the track (http://986forum.com/forums/showthread.php?t=76247)

NewArt 09-20-2019 03:49 PM

tire moving on rim at the track
 
So, I'd heard of this; someone had posted here on the forum. Curious, I marked my track wheels with new tires (RE-71R) before a 2-day event. This is the right rear
wheel after 2 days:

http://986forum.com/forums/uploads02...1569023379.jpg

piper6909 09-20-2019 05:31 PM

That's mind-blowing. The question is, was it the acceleration or braking that did it? If that's a pick of the right tire, it would be braking. If it's the left tire, then it would be acceleration.

NewArt 09-20-2019 06:09 PM

Actually. I think it’s the left rear. I get my hands mixed up! ��

maytag 09-20-2019 06:19 PM

Here's a recent thread about it. You'll see I wasn't convinced, until I experienced it in dramatic fashion.

https://r.tapatalk.com/shareLink/topic?url=http%3A%2F%2F986Forum%2Ecom%2Fforums%2Fs howthread%2Ephp%3Ft%3D73341&share_tid=73341&share_ fid=31135&share_type=t&link_source=app

You can see my marks on the sidewalls, which lined up with the valve stems at the beginning of the day. https://uploads.tapatalk-cdn.com/201...5292f76e4a.jpghttps://uploads.tapatalk-cdn.com/201...1600ce14b3.jpg

Sent from my SM-G970U using Tapatalk

rexcramer 09-20-2019 06:23 PM

The original pic doesn't look like all that much of a shift. I remember other posts' showing +/-6" IIRC from track days. I would imagine the rears show far more of a shift than the fronts?

EDIT: Maytag looks about right.

piper6909 09-20-2019 06:34 PM

Quote:

Originally Posted by NewArt (Post 603583)
Actually. I think it’s the left rear. I get my hands mixed up! ��

Then it must be happening during acceleration. I was expecting the opposite. I didn't think they had enough torque to do that.

But then again, it looks like all 4 tires moved, so it has to be during braking. Are you sure it came from the left (driver's) side?

piper6909 09-20-2019 06:41 PM

Quote:

Originally Posted by maytag (Post 603584)
Here's a recent thread about it. You'll see I wasn't convinced, until I experienced it in dramatic fashion.

https://r.tapatalk.com/shareLink/topic?url=http%3A%2F%2F986Forum%2Ecom%2Fforums%2Fs howthread%2Ephp%3Ft%3D73341&share_tid=73341&share_ fid=31135&share_type=t&link_source=app

You can see my marks on the sidewalls, which lined up with the valve stems at the beginning of the day. https://uploads.tapatalk-cdn.com/201...5292f76e4a.jpghttps://uploads.tapatalk-cdn.com/201...1600ce14b3.jpg

Sent from my SM-G970U using Tapatalk

I noticed each pair of tires rotated in opposite directions. Is one pair fronts and one pair rears?

NewArt 09-21-2019 04:33 AM

Quote:

Originally Posted by rexcramer (Post 603585)
The original pic doesn't look like all that much of a shift. I remember other posts' showing +/-6" IIRC from track days. I would imagine the rears show far more of a shift than the fronts?

EDIT: Maytag looks about right.

Yeah, I thought that the previous post was an anomaly, but I now see that this is common for track tires. Maytag’s pictures bowled me over! The movement of my tires is negligible in comparison. :eek:

maytag 09-21-2019 06:33 AM

Quote:

Originally Posted by NewArt (Post 603599)
Yeah, I thought that the previous post was an anomaly, but I now see that this is common for track tires. Maytag’s pictures bowled me over! The movement of my tires is negligible in comparison. :eek:

The guys at the track that day told me that's very common. I'd have never believed it, had it not happened to me.

And piper, as for what tire is what in my photos, I don't recall now. But I'd think it only makes sense that the rears spin under power (so the wheel turns "forward" in the tire) and the fronts under braking (so the tire turns "forward" on the wheel).

Dunno.

Sent from my SM-G970U using Tapatalk

NewArt 09-21-2019 08:27 AM

Well, so much for precision wheel balancing! :rolleyes:

maytag 09-21-2019 08:57 AM

Quote:

Originally Posted by NewArt (Post 603617)
Well, so much for precision wheel balancing! :rolleyes:

Yup. That's exactly what I said in the other thread. Never paying to balance track tires ever again

Sent from my SM-G970U using Tapatalk

NewArt 09-21-2019 09:50 AM

So, do street tires do this in day to day driving? Anyone checked?

piper6909 09-21-2019 10:54 AM

Quote:

Originally Posted by maytag (Post 603609)
The guys at the track that day told me that's very common. I'd have never believed it, had it not happened to me.

And piper, as for what tire is what in my photos, I don't recall now. But I'd think it only makes sense that the rears spin under power (so the wheel turns "forward" in the tire) and the fronts under braking (so the tire turns "forward" on the wheel).

Dunno.

Sent from my SM-G970U using Tapatalk

If we know which side the wheels/tires came from and the direction of the rotation, we can determine if it's braking or accelerating causing it. I suspect that even an S doesn't have enough torque to cause this under acceleration.

My theory is that it's caused by breaking, and the front tires rotate more than the rears, because the fronts brake harder.

I probably won't track until next year, and if I do I probably won't drive it as hard as some people on here because I don't have the skills. So it would be great if someone would try the experiment and note which corner each tire/wheel was on. Maytag, would you be so kind? ;)

maytag 09-21-2019 12:43 PM

Quote:

Originally Posted by piper6909 (Post 603622)
If we know which side the wheels/tires came from and the direction of the rotation, we can determine if it's braking or accelerating causing it. I suspect that even an S doesn't have enough torque to cause this under acceleration.



My theory is that it's caused by breaking, and the front tires rotate more than the rears, because the fronts brake harder.



I probably won't track until next year, and if I do I probably won't drive it as hard as some people on here because I don't have the skills. So it would be great if someone would try the experiment and note which corner each tire/wheel was on. Maytag, would you be so kind? ;)

Well what I do know, is that you're looking at a rear laying flat and a front from the same side leaning against it, in both images. I just don't remember which image is left or right.

As you can see, they're rotating opposite directions on the wheels.

There's very, VERY little braking going on on the rear wheels, especially at the racetrack where brakes are usually on VERY HARD, or not at all. There is SUBSTANTIALLY more torque being applied to the rear wheels under acceleration than under braking.

Sent from my SM-G970U using Tapatalk

piper6909 09-21-2019 02:37 PM

Quote:

Originally Posted by maytag (Post 603626)
Well what I do know, is that you're looking at a rear laying flat and a front from the same side leaning against it, in both images. I just don't remember which image is left or right.

As you can see, they're rotating opposite directions on the wheels.

There's very, VERY little braking going on on the rear wheels, especially at the racetrack where brakes are usually on VERY HARD, or not at all. There is SUBSTANTIALLY more torque being applied to the rear wheels under acceleration than under braking.

Sent from my SM-G970U using Tapatalk

Ok. I didn't think they would put out that much torque to rotate the tires on the rims. You know more than I do, so I'll take your word for it.

:cheers:

piper6909 09-21-2019 02:43 PM

So, judging from the position of the valve stems, unless the rear tires rotated over 270 degrees, the top pic should be the tires from the left, correct?

Geof3 09-21-2019 10:34 PM

How in the world does this happen and not break the bead/seal? Are the tires getting hot enough to somehow soften the bead enough to allow this? That’s pretty crazy. I’ll have to mark mine next time out...

particlewave 09-22-2019 07:35 AM

I’m shocked that you guys are so shocked by this. :D
Seriously...

piper6909 09-22-2019 09:25 AM

Quote:

Originally Posted by particlewave (Post 603670)
I’m shocked that you guys are so shocked by this. :D
Seriously...

I'm shocked that you're shocked that we're shocked! :D :D :D

Seriously, I'd never think that was possible unless I saw the pics. But then again, I've never tracked.

maytag 09-22-2019 10:05 AM

Quote:

Originally Posted by particlewave (Post 603670)
I’m shocked that you guys are so shocked by this. :D

Seriously...

I know..... everyone at the racetrack was so dismissive of this, when I was surprised by it. They've seen it for so long, at such extremes, they couldn't imagine I didn't know about it.

Now I do. ;-)

Sent from my SM-G970U using Tapatalk


All times are GMT -8. The time now is 01:55 PM.

Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Content Relevant URLs by vBSEO 3.6.0
Copyright 2024 Pelican Parts, LLC - Posts may be archived for display on the Pelican Parts Website