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Old 04-05-2010, 08:56 PM   #1
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Default Flat spotted tires?

I was practicing some hard stops from 110-30 today and on one of the runs I really locked the fronts up enough to flat spot them both. Besides ordering a proportioning valve to get some rear bias and more practice, what do I do? I've been told to put them on the back and do a big smokey burnout, but I don't know if that will fix them? Toss them in the trash because they're junk? Leave them on the front until I get a feel for the new brakes? Have them shaved if I can find someone to do it? Any ideas?
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Old 04-05-2010, 09:08 PM   #2
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I've heard doing burnouts with them on the back only makes them worse. The tire rotates until the flat spot, then hops when it hits the flat spot, making it worse. At least that's how I understood it. If you can't live with the vibration, I'd say they're junk. If they have good tread and you know of a place that'll shave, that's worth a shot. What tires are they?
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Old 04-05-2010, 09:26 PM   #3
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Not sure about the burnout, with your line lock and big power I think that'd be pretty easy/fun if they dont hop like curly suggests. I'd also think that some heavy understeer would help as well. Let some air out and go take some hard corners.

Where were you practicing braking from 110?
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Old 04-05-2010, 09:45 PM   #4
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have a friend who thought this was funny to do in his clk until they flatspotted and made driving at low speeds ubearable. we tried burning them out and it helped some but not completely. wonder if the tires could be shaved like they do for race tires
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Old 04-05-2010, 09:47 PM   #5
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What tires are they?
They are RS2s. You've really got me curious about the burnout thing now. I'll give it a try just to find out for sure.

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Where were you practicing braking from 110?
You don't want to know. It was fun though, all fourth gear pulls to redline so I'm guessing it was around 110.

I guess I'll keep them on until I feel comfortable braking with this setup so I don't destroy another pair. These brakes/pads definitely grab so much harder than the stock brakes. Time to order a proportioning valve to let the backs start helping out, they don't even feel like there doing anything.
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Old 04-05-2010, 10:01 PM   #6
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Most tire shavers will not shave a used tire. They are likely junk. You can use them for more stopping practice, but when you get close to locking them up, it usually finds the flat spot and just makes it bigger.
I have an embarassingly large collection of flat spotted r comps.
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Old 04-05-2010, 10:06 PM   #7
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Totally unrelated question; you dont still have drag radials on the rear do you?
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Old 04-05-2010, 10:14 PM   #8
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Just FYI Tires flat spot more easily when they are cold. Kind of like cheese to a grater
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Old 04-05-2010, 10:53 PM   #9
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Totally unrelated question; you dont still have drag radials on the rear do you?
Not sure which pair you're referring to? I ditched the BFGs a long time ago because they were junk. The MTs I was running are waiting to be mounted on the new 6ULs sitting next to them. I plan on running them on the street and the strip. For now it's just the RS2s all the way around and that isn't really working out very good.

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Just FYI Tires flat spot more easily when they are cold. Kind of like cheese to a grater
Good to know, didn't really think about that. I'm sure this won't be the last set of tires I destroy.
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Old 04-06-2010, 12:17 AM   #10
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i flatspotted some old azenis 215s on the track and they eventually wore round after a long time. only problem is they kept locking up on the same flat spot every time I tried to threshold brake..... so if you're braking hard a lot, dump them.
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Old 04-06-2010, 12:51 AM   #11
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I mildly flatspotted my RS2s at an autox. Cold day, cold tires, cold brakes. They weren't so bad as to be trash, just annoying. I think I've done 4 track days on them since and they have maybe gotten a tiny bit better, but not much, still annoying. It will probably help if you swap the flatspotted ones to the rear and run the good ones up front.
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Old 04-06-2010, 02:04 AM   #12
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Put them on the rear. Lift your big toe.
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Old 04-06-2010, 06:31 AM   #13
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Like Matt said, the biggest problem is that once you flatspot them, they will continue to lock on the same spot and it will just get worse.

Move them to the back, and if you can't feel the flatspot from vibration enough to bug you, forget about it. As long as you haven't really trashed them, like burning through half the remaining tread or into the cords or something, they should wear round again eventually. Moving them to the back will do two things - first, it will make you much less likely to lock them again, and two, it will lessen any vibration they do cause.

If you keep locking them up, or you can feel a vibration, dump them. When flatspots are REALLY bad you can actually feel them as a high-frequency shake in the wheel that gets worse during hard cornering.

Glad you like the brakes, Jason. The prop valve will make a big difference as well - you should be able to really dial them in nicely with the Sport rears.
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Old 04-06-2010, 08:44 AM   #14
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What I want to know is....... what brakes did you put on?

I had an old set of r-comps that was was driving around on the street with because I was trying to wear them down (had bought a new set and couldn't let myself take the old ones off until they were showing cords....I don't waste rubber). So I got really good at 30mph rolling burnouts. My dumbass did it and looked back and saw all kinda cool marks and smoke....and as soon as I let off the brakes the car started vibrating like hell. Turns out I locked up both fronts and was pushing them at ~40mph or so for about 75ft Wasn't down to the cords or anything, and they eventually rouded up....only for me to finish them off with two massive 2nd gear power brakes
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Old 04-06-2010, 09:40 AM   #15
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I put the Trackspeed Engineering setup on the car with XP10/XP8 pads. Every car I've owned for the past decade has had abs besides this one. The stock brakes/pads/lines have always felt ok to me for what I did with the car, but it now has a completely different pedal feel. It's as if I'm learning to brake all over again. I think I'll practice in the rain a bit more.

There's one thing I do know for sure, every part of this car is more capable than the driver.
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Old 04-06-2010, 01:44 PM   #16
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There's one thing I do know for sure, every part of this car is more capable than the driver.
Welcome to the club. You should try out some autox this summer. Especially the rainy day ones.
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Old 04-06-2010, 02:06 PM   #17
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Welcome to the club. You should try out some autox this summer. Especially the rainy day ones.
I doubt I will ever autox again, just not my thing. Most likely I'll just try and do 1 track event each month if my schedule will allow it.
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Old 04-06-2010, 02:45 PM   #18
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I doubt I will ever autox again, just not my thing. Most likely I'll just try and do 1 track event each month if my schedule will allow it.
I recall you saying the same thing about road racing not one year ago...

Just sayin
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Old 04-06-2010, 02:51 PM   #19
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Road racing is great, someone found a way to connect all the straightaways so I don't have to go back and wait in line.
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Old 04-08-2010, 09:36 PM   #20
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In an attempt to save the tires I did a huge smokey burnout this afternoon. It actually helped out quite a bit. I'm going to do a few more and see how they feel.
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