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Old 10-03-2006, 02:08 PM   #1
chimchimm5
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Default So is this what slip angle is?

So is this what tread block deformation during with nonzero slip angle is?

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Old 10-03-2006, 08:57 PM   #2
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Don't know the answer to your question... but that looks mighty familiar. Those outside corners of my tires are all torn up (looks like terry cloth)... I'd be interested in knowing as well.
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Old 10-04-2006, 08:27 AM   #3
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I don't see any deformation just wear patterns. Seem like it could be camber and toe in, anyone? You're not using those tires enough..
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Old 10-04-2006, 09:21 AM   #4
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Yeah, looks like normal wear to me.

Slip angle doesn't have anything to do (directly) with tire wear patterns. http://en.wikipedia.org/wiki/Slip_angle If you're cornering hard with excessive slip angles, then yeah, your tires will wear strangely.

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Old 10-04-2006, 09:27 AM   #5
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The scalloped edges look like tread block deformation during cornering.

It also looks like you've got the pressures too high. The wear should come to the top of the arrow.

Excessive slip angle usually shows up as lines across the tread, as the tires slide over the asphalt and it acts like 10 grit sandpaper.
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Old 10-04-2006, 01:32 PM   #6
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Quote:
Originally Posted by fliz View Post
The scalloped edges look like tread block deformation during cornering.

It also looks like you've got the pressures too high. The wear should come to the top of the arrow.

Excessive slip angle usually shows up as lines across the tread, as the tires slide over the asphalt and it acts like 10 grit sandpaper.
"top of the arrow"? Which arrow?

As for the PSI, I chose this PSI based on pyrometer readings (inside, middle, outside). This is the PSI that gave me more even tire temps. I think the tread block below the scalloped portion is sidewall, although it may not look that way in the picture.

I use different PSI for autox obviously. I think the scalloping came from the autox.
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Old 10-04-2006, 01:36 PM   #7
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"top of the arrow"? Which arrow?

As for the PSI, I chose this PSI based on pyrometer readings (inside, middle, outside). This is the PSI that gave me more even tire temps. I think the tread block below the scalloped portion is sidewall, although it may not look that way in the picture.

I use different PSI for autox obviously. I think the scalloping came from the autox.
The little triangle that is at the edge between the sidewall and treads.

Scalloping can develop if you understeer a lot in autox and the side wall doesn't start where you're saying. It's at the base of that triangle is not even further down.

My current tires are worned to the letters, to give you an idea. Falkens 615s.
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Old 10-04-2006, 01:53 PM   #8
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Originally Posted by Mind View Post
Don't know the answer to your question... but that looks mighty familiar. Those outside corners of my tires are all torn up (looks like terry cloth)... I'd be interested in knowing as well.
If you're on a stock alignment, it's probably because of the nasty camber gain you get during cornering.
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Old 10-04-2006, 02:22 PM   #9
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Originally Posted by WRX11 View Post
The little triangle that is at the edge between the sidewall and treads.

Scalloping can develop if you understeer a lot in autox and the side wall doesn't start where you're saying. It's at the base of that triangle is not even further down.

My current tires are worned to the letters, to give you an idea. Falkens 615s.
Yeah, I understeered a lot. I purposely held off on suspension mods until I could get one autox in using stock, so it was my first venture into truly knowing where the limits of the car is... and so yeah, I ended up understeering as I discovered that limit.

I'll let out some air from my tires to see. Currently I'm at 37 front, 35 rear (215/45/17).

Since, I have added front and rear sway bars to help with the camber loss and will be gettng a negative front camber alignment soon.
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Old 10-04-2006, 03:26 PM   #10
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Yeah, I understeered a lot. I purposely held off on suspension mods until I could get one autox in using stock, so it was my first venture into truly knowing where the limits of the car is... and so yeah, I ended up understeering as I discovered that limit.

I'll let out some air from my tires to see. Currently I'm at 37 front, 35 rear (215/45/17).

Since, I have added front and rear sway bars to help with the camber loss and will be gettng a negative front camber alignment soon.
Don't let out air, you still have tires to use. Brake straight longer before you turn may help avoiding scalloping. Most guys I autox with have 40 psi +.
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Old 10-04-2006, 07:21 PM   #11
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Quote:
Originally Posted by WRX11 View Post
The little triangle that is at the edge between the sidewall and treads.
I think you might be interpreting the picture incorrectly... there is wear all the way down to the edge of the shoulder, through the 'arrow' region... the reason the line is there between corner tread and the flat part of the tire is from the normal driving he's done since autox.

Or maybe I'm interpreting the picture wrong, but that's what my tires look like and I know for sure that I'm getting on the corners of my tires...
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Old 10-04-2006, 08:28 PM   #12
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Ok... I've drawn all over my picture... so heres the legend:

red lines - these are the saw tooth scrub marks that I was guessing is due to my hard cornering during autox; probably during understeering
purple line - the approximate border between the patch my resting car sits on and where the tire is no longer contacting the ground (note how the tread block gaps go from the V pattern to the horizontal direction)
yellow circle - assuming this is the triangle referred to above as the "arrow"

Which would you consider is the "tire sidewall": pink, green, or blue line?

I was guessing the blue line was the "sidewall" (because of the purple line)

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Old 10-04-2006, 08:49 PM   #13
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I would say the pink is the sidewall. Your aggressive use wear pattern appears pretty good, as the wear is about to the tip of the yellow-circled arrow.

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Old 10-04-2006, 09:07 PM   #14
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My vote is pink for the sidewall.

What does one need to do in order to stay out of the red? I'm running stock alignment maxed out, -0.9 for me. I just got a WL front 22mm adj bar, but that's it as far as suspension mods up front. Is going in the 'red' inevitable w/out camber bolts/plates?
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Old 10-04-2006, 09:21 PM   #15
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So, to summarize, my red section is ok *for the tire*, because it's not sidewall.

However, it's better not do have the red area because it means the tire patch is not flat on the ground (positive camber), and thus not as good traction.

Is that right?
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Old 10-04-2006, 11:55 PM   #16
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Quote:
Originally Posted by Mind View Post
My vote is pink for the sidewall.

What does one need to do in order to stay out of the red? I'm running stock alignment maxed out, -0.9 for me. I just got a WL front 22mm adj bar, but that's it as far as suspension mods up front. Is going in the 'red' inevitable w/out camber bolts/plates?
No. The simple answer is slow down. And I'm not saying that to be a smart ass, it's seriously the right answer. On a relatively stock, camber limited car, your best bet is to strictly adhere to the "slow in, fast out" mantra to preserve your tires. I did two track weekends in my sister's '02 WRX wagon, stock suspension with the exception of a sedan rear swaybar. Alignment was courtesy of me, in the parking lot at the hotel the night before the events, adjusting the camber bolts to max out the negative camber . On a wagon that means about what you've got - somewhere around -1.0deg. With that camber, and running on RE92s, I was the fastest Subaru among the group of us who were there together (this was a few years ago, in the pre-STi days , but there were a couple other WRXs plus a turbo'd 2.5RS). There are many in the Motorsports forum who will proclaim "Thou must have -3deg camber to drive these cars fast!" but the fact of the matter is if you listen to the feedback the tires give you and don't overdrive them these cars will do just fine with stock camber.

Quote:
Originally Posted by chimchimm5 View Post
So, to summarize, my red section is ok *for the tire*, because it's not sidewall.

However, it's better not do have the red area because it means the tire patch is not flat on the ground (positive camber), and thus not as good traction.

Is that right?
Not really. If you were getting that kind of wear on the street during your normal driving then I would be concerned. However, from what you're saying, you're only wearing into the red section there during aggressive auto-x driving. The fact that you're getting to the tip of the arrow, but not beyond, means you're using every last bit of tread but not rolling onto the sidewalls. That's pretty much perfect. And really this tread wear analysis is superfluous since you've taken pyrometer readings across the face of the tires - those are what really tell the story of how the tire is working.

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Old 10-05-2006, 08:15 AM   #17
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Originally Posted by Mind View Post
I think you might be interpreting the picture incorrectly... there is wear all the way down to the edge of the shoulder, through the 'arrow' region... the reason the line is there between corner tread and the flat part of the tire is from the normal driving he's done since autox.

Or maybe I'm interpreting the picture wrong, but that's what my tires look like and I know for sure that I'm getting on the corners of my tires...
Quote:
Originally Posted by chimchimm5 View Post

I think you're misinterpreting my line and your line. The line I am talking about sit just above the lettering on the sidewall.

The triangle is the end of the tread patch and if he had pushed hard, the triangle wouldn't be there, mine were gone long ago. This alos means you're using all your treads not just the flat patch of it.

On my current tires, the line I have mentioned between the top of the lettering and the botom of the tread blocks are gone. Just a little lower into the top end of the pink line.

Hopefulyl that's clearer to you.

Like Pat O says, "slow in, fast out" because you want to shave the necessary speed so you can get on the gas earlier. If you're on OEM settings, brake straight will give you better decceleration so you won't understeer as much trying to threshhold brake.
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Old 10-05-2006, 08:39 AM   #18
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Quote:
Originally Posted by Patrick Olsen View Post
No. The simple answer is slow down. And I'm not saying that to be a smart ass, it's seriously the right answer. On a relatively stock, camber limited car, your best bet is to strictly adhere to the "slow in, fast out" mantra to preserve your tires. I did two track weekends in my sister's '02 WRX wagon, stock suspension with the exception of a sedan rear swaybar. Alignment was courtesy of me, in the parking lot at the hotel the night before the events, adjusting the camber bolts to max out the negative camber . On a wagon that means about what you've got - somewhere around -1.0deg. With that camber, and running on RE92s, I was the fastest Subaru among the group of us who were there together (this was a few years ago, in the pre-STi days , but there were a couple other WRXs plus a turbo'd 2.5RS). There are many in the Motorsports forum who will proclaim "Thou must have -3deg camber to drive these cars fast!" but the fact of the matter is if you listen to the feedback the tires give you and don't overdrive them these cars will do just fine with stock camber.
No worries, not taken as a smart remark. Thanks for the tips. I know I definitely have moments where I'm entering corners too fast, and I'm glad to hear that if I modify my driving technique that I shouldn't be getting the amount of wear on my shoulders/sidewall tops as I'm seeing now. It'll be a pretty good gauge on how I'm driving.
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Old 10-05-2006, 08:42 AM   #19
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Originally Posted by WRX11 View Post
I think you're misinterpreting my line and your line. The line I am talking about sit just above the lettering on the sidewall.

The triangle is the end of the tread patch and if he had pushed hard, the triangle wouldn't be there, mine were gone long ago. This alos means you're using all your treads not just the flat patch of it.

On my current tires, the line I have mentioned between the top of the lettering and the botom of the tread blocks are gone. Just a little lower into the top end of the pink line.

Hopefulyl that's clearer to you.

Like Pat O says, "slow in, fast out" because you want to shave the necessary speed so you can get on the gas earlier. If you're on OEM settings, brake straight will give you better decceleration so you won't understeer as much trying to threshhold brake.
Sorry, I was misinterpreting your interpretation . Thanks for clearing that up. That was good advice from Pat.
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Old 10-05-2006, 01:15 PM   #20
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Oh man, I just realized the tire pictured above was my REAR tire during the autox, and I had since rotated them front/back.

The original tire that was used as the FRONT tire during the autox was this:


In this case, I definitely was rolling onto the sidewall. I had 38 psi cold and after my runs, it was 40.5psi. For the fun runs, I pumped it up to 42 psi and that (combined with better driving) produced less understeer and better times.
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Old 10-05-2006, 02:35 PM   #21
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are those goodyears F1's
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Old 10-05-2006, 02:37 PM   #22
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are those goodyears F1's
yes. on Kosei's K1 TS 17x7
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Old 10-05-2006, 02:47 PM   #23
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Slip angle is the angle at which a tire has the most traction. The higher the performance tire, the shallower the slip angle is (with exception to rally).
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Old 10-05-2006, 02:51 PM   #24
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I know this is unrelated. I'm getting F1 for my '04 wagon, what are your impressions of these tires? Are those 225's?
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Old 10-05-2006, 03:34 PM   #25
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The F1's are stock size 215/45/17 and I love them for what I bought them for: which is everything in California weather.

- commuting
- driving my family around (comfortable, not noisy)
- great dry/wet grip (no snow around here, except the mountains, but then I switch back to the RE92 on the stock wheels)
- autox worthy
- reasonable price
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