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?

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?

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?

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

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.

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.

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.

Totally unrelated question; you dont still have drag radials on the rear do you?

Just FYI Tires flat spot more easily when they are cold. Kind of like cheese to a grater

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.

Good to know, didn't really think about that. I'm sure this won't be the last set of tires I destroy.

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.

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.

Put them on the rear. Lift your big toe.

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.

What I want to know is....... what brakes did you put on? :giggle:

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 :giggle: 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 :D

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.

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.

I recall you saying the same thing about road racing not one year ago...

Just sayin ;)

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.

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.

:rofl:

Do it for science and the community. God bless you!

Videos!!

In for video as well... :D Glad that it appeared to help.

If I can find someone to work the camera I'll get it on video.

Too far away for me... Anyone else? Haha

I'll be cam bitch tomorrow if you want to meet up a bit earlier.

Sounds good to me.

You don't need a proportioning valve, you need more practice. In Spec Miata brake pads are free but the remainder of the brake system must remain stock. The Miata system is extremely capable in stock configuration with racing pads. It is all about brake modulation, threshold breaking is not simply a matter of jumping on the brakes as hard as you can. If you brake that way you are going to lock up all the time. You need to learn modulation, standing a car on its nose is not the fastest way around the track, or the most efficient way to brake.

Enjoy the practice, there is nothing better than driving on a closed course!!!

It seems to work a little different with turbo miatas. We carry a lot more speed into corners whereas a spec miata is exercising its ability to fly around the track hitting the brakes as little as possible.

Also he now has wilwood 4 pot calipers up front and still the stockers in the rear. He needs RX7 rears now with a prop valve for some super awesomeness :)

Yeah, what this guy said.

That is true, didn't realize the brake upgrade. But it is still about modulation, a proportioning valve will help but you still can't stand the car on its nose during breaking.. Giving up a little entrance speed to maximize exit speed will always result in faster lap times.

Agreed. Try doing that with 300+ horsepower though ;)

That's when tune, throttle modulation and brake modulation come into play. Not to mention tires, suspension setup, weight distribution on the car ect ect ect. Neither the brakes or the throttle should ever be treated as on off switches on the race track.

It's tough with the 200hp I have with my conversion, I am sure it is even harder with FI and 300hp. But that is why they make sticky tires great brakes and tunable suspensions. Then it's just a matter of fine tuning the weakest link in any race car...the driver:skid:

Agree w/ hingstonwm. Take the rest of your tires life and practive threshold braking. If you are going to drive a fast car w/o ABS, then you need (repeat need) to be good at threshold braking. Now you have a good set of tires to practive with. Learn to recognize the onset and feel and modulate the brake pedal accordingly. Good luck and have fun.

I'm just going to toss in my :2cents: The car is absolutely insanely easy to lock up the fronts on. I like to think I have a pretty delicate foot on both the throttle and the brakes ( I have to, I live in Seattle and my car will fucking KILL YOU in the rain if you aren't careful) and Jason's car surprised the shit out of me on Saturday. The brakes are like an on/off switch. No feathering, no easing into it, it feels like nothing is happening, and suddenly about 1/64" further down you are headbutting the dash/wheel. The car needs more prop valve and less internet bench race coaching.

After giving the flat spotted tires a once over I decided that they are finished. Any additional burnouts will push them through the cords.

As for practicing threshold braking, that's the idea, hence how I did this to begin with.

and threshold braking will only serve to mislead you by sliding on the flat spots again.

I forgot to mention, those tires aren't on the car any longer.

Whatever, dude. I had to run a race once where initial braking was perfect but as momentum slowed and the brakes became more efficient they would lock up. This was due to heat checking in the rotors. Anyway, in order to run the race I had to roll off the brakes at just the right time to keep the wheels rolling and not locking up. This was accomplished through BRAKE MODULATION.

If you are locking up the tires, you are to heavy on the pedal...period, or there is a problem with the set up of the system, a brake bias valve will not fix this. Rear brakes will help the car stop but the majority of the braking is up front where the weight shifts to during braking. Changing balance will allow you to dial in the best performance, but it wont keep tires from locking up, that is the job of the loose nut behind the wheel. If they are that much of an on/off switch there may be an issue with the brakes. Calipers, pads, rotors, lines, who knows but there may be a mechanical issue. Tires have a finite amount of grip. If you are using the grip for braking, then you have less grip left to initiate turn in and to carry momentum through the corner.

As a racer your car changes through the course of an event. Brakes get hot and fad a little, tires get hot and lose a little grip, engines get hot when you run in a draft. My point to this is you need to adapt to the conditions, weather the conditions are those of the car or the track.

Indy cars and F1 cars have brakes so strong that they can lock the fronts at 200 mph, even with brake bias. Ever wonder why you don't see everyone in the field flat spotting tires? Brake modulation.

I was not harsh with my suggestion of practice makes perfect. I was not a dick when I said the fastest way around a track was not to stand the car on its nose in every corner. I was stating fact and did not attack you friend.

Road courses are nothing more than a bunch of drag races connected by a bunch of corners. All cars no matter how much power they have are momentum cars. The more momentum you can carry through a corner on exit the faster you will get down the straight to the next braking zone...the faster your lap times will be.

Slow in fast out is the way you go fast in any car. I know we are talking road racing here but probably the easiest example of slow in fast out to visualize is in NASCAR. How many times have you seen a guy try a dive bomb move only to slide up the track, or watch the guy he just passed drive back past him at mid corner. By slowing down you can get the car settled, change direction and get back in the power sooner, basically causing the next straight away to be longer, since you are accelerating as the other guy is still braking because he drove so deep into the corner.

I have not be an ass with my previous remarks, furthermore all I have done with this post is state racing fact, I have not attacked anyone.

As for weather I am talking out of my ass or not, you be the judge. It has been a few years since I have raced, 5 years in fact. However, the last two years I raced in a total of 38 events, and finished off the podium only 3 times. Finishing second in the points to the current T3 national champion in the SCCA both seasons. I only mention this to add credibility to my post.

If the car needs a proportioning valve then get one, but don't expect it to magically fix the front brake lock up because it, wont unless you dial all of the front out, Best regards.

I've had a few different people drive the car and I think the consensus is that the brakes are awesome. The differences that people are seeing is because they are comparing them when they are cold versus when they have some heat in them, nothing more.

I'll be putting regular pads in the fronts for street driving shortly. For now I'm just spending time putting some miles on what I have and the more I drive it the better they feel to me. The proportioning valve is something that's completely unrelated to the fronts locking up. It's just another piece of the puzzle that I feel will allow the car to stop even better and others have shared that same opinion.

The proportioning valve will help no questioning that at all. If you are using street service pads for the track that is a huge part of the problem. I have been a serious track rat in the past, I can tell you if you want to track your car you absolutely need race pads to get the most out of the car.

What I have done in the past with my street/track toys is to have a second set of pads and rotors that are dedicated for track use. The night before I go to the track I nut and bolt the car and switch out my street setup for my track setup. Factory/street pads are not designed for the abuse/temps generated at the track during spirited driving. Spend the extra money on good set of rotors and race pads for the track, you will not regret it.

:rly:

Wayne with all due respect, you carry more speed to the corner not into the corner with a turbo car. If you are trying to carry the extra speed the turbo provides you on the straight, through the corner, you are not going to be as fast.

I have thousands...yes thousands of track miles in spec miata, and driving one is not an exercise of using the brakes as little as possible. If fact, you use the brakes quite hard in a spec miata. There is just less energy/speed to bleed off when compared to a turbo miata. But this may not always be the case. Yes, a turbo car may have more acceleration, but a turbo car on street tires may not have as fast a trap speed as a SM on race tires. However, all things being equal, you will have more energy to dissipate with a turbo car before entering a corner.

As I mentioned in a previous post. Tires have a finite amount of grip. Grip is divided into traction for braking and cornering on the front tires; braking, cornering, and acceleration on the rear tires. Notice braking comes before cornering and acceleration, just like it does on the track. The more traction you use for braking the less traction you have available for cornering, and acceleration. If you get your braking done in a straight line before entering the corner you now have all the friction/grip/traction developed by the tire available for cornering/acceleration. Try to accelerate too quickly through the corner and you run out of friction/grip/traction and push out of the corner off of your line. Of course there are other factors at work, but all things being equal, the person that manages the friction/traction provided by their tires the best, will be the fastest. :beer:

That is more or less what I meant to say I think.

:bigtu::bigtu::bigtu:

I'm not questioning your track experience. Compared to mine (read:0), you obviously know more about racing on a track than I do. I spoke up because no matter how many times Jason has directly said that he probably just needed more practice, you keep regurgitating the same thing over and over again like a broken record. We all get it, modulation is the key, we aren't retarded. I do know what good brakes feel like however, and I'm of the opinion that there is simply too much brake up front given the characteristics of these brakes, and that a prop valve would help level things out. I was most likely too heavy on them, I'll give you that considering I had just come from driving my car with a completely stock 1.6 braking system.

I don't think you are talking out of your ass, or being 'harsh' in your suggestions, but I do think that you are being a' holier than thou' king of the track know it all and quite frankly I find it a little irritating. If you disagree, look at how you react to someone's differing opinion on an internet message board. You wrote a 1/2 page speech to disagree with my 4 sentence opinion.

I don't want a problem with you, it seems like you have a lot of good info to offer, and it is really great to have people like you around. Please though, tone down the preaching so you don't come off looking like a dick.

I'm running track pads on this car at the moment. That's why I am trying to get a good feel for them. I had confidence in the stock setup and as I practice I'm getting that confidence back with this setup. I will be switching to a street pad for weekend cruising and such while putting the track pads on for track events, the car isn't a daily.

I think a lot of the issue has to do with them being cold when you were driving it. Once they get a bit of heat in them they feel solid. The more time I spend driving it the better I like them. Next time we go for a drive, we'll switch cars for a bit and I'm certain you'll get a good feel for them.

stfu newb and stop being so damn mean until you have a few k posts I challenge you to a foot race

Don't want any trouble either.

Yeah, I did take exception to your bench racing coaching comment. Hence the whatever dude reply to your bench racing comment.

I have been an instructor for a different corporate events and off and on as time allows for SCCA events. It has been my experience that most drivers have very little idea what is involved in hustling a car around a track. It is much more than standing of the gas until the last possible second. I go into that in greater detail in one of my posts.

Sorry if you think my post comes across with a "know it all attitude" or preaching. That was not my intention. I have worked with many drivers in the on track setting. If it is a new experience, the track can be an intimidating place. I have found it is easiest to impart knowledge and concepts by simplifying the delivery. It was never my intention to talk down to anyone just try to make the concept easy to understand. It has been my experience that most don't get it until you simplify it. That is all I was attempting to do.

Looking back at it, my first post was pretty snide, and I owe the OP an apology. But I won't apologize for my other posts. They are more in depth as they go, and I don't feel they were condescending' or "preaching in anyway, of course that is my opinion. We also have the choice to just ignore each others post if we find we rub each other the wrong way. Not all personalities mesh well.

So, which one of you magicians can put the tread back on my tires?

If you call me out I am going to defend myself. Hopefully you are being tongue in check with the stfu comment.

How was I being mean?

Newb to the forum yeah, new the track not a chance. So if you were being tongue and cheek...cool if not. then I guess we can just tell each other to.:fawk:

Jay I can do that!

Sounds like you took a good look at the tires and deemed them unusable. I think you said they are not on the car any longer. I have not seen them but trust your instincts. Could you post a pic or two of the damage?

It is possible to get away with running flat spotted tires on the rear of the car, if they are not to severely damaged. Sometimes you can put them on the back and not even feel a vibration.

The problem with flat spots is once you have them threshold braking is lowered. This is more an issue with fronts. You probably know this from experience so I won't go into details.

Brake bias will help you get the cars braking balanced to your driving style which is what we all strive for with our cars. Sounds like we think a like as far as brakes go. I assume the 4 pots you have are the ones that are commonly available for Miatas, the ones produced by Wilwood, correct. What is the pad that you are using? Are there different pad choices for your setup? You know Hawks, Carbotechs and such? I have personally always run hawk blues. They just fit my style, and I like their predictability. Having no personal experience with your brake set up I can't offer to much advice.

Toyo has reintroduced the RA-1 for the Miata that may be a great choice for you, or it may not. They offer good predictability and can take a lot of abuse. Hoosier makes a great tire too, but they don't last as long as the RA-1, they are fast though. Trade offs right? How fast do you want to go? How much money do you want to spend.

Hope this helps get us back on topic!

(edited for one other thought) I looked back and didn't see mention of what tires you are running. Are they a street tire, an R rated dot tire, or a slick? Big brakes can overwhelm street tires pretty quickly.

The tires are off the car and the Mickey Thompsons are back on. I did have them on the back for a bit, but even after my best attempt they still are pretty bad. They are past the wear bars on the inside portion and have over half thread on the remaining portion. I'll take a photo when I get home today. I could probably switch them from side to side, but if I'm going to get them mounted and balanced I'd rather just put a good set on.

I'm running the Carbotech XP10s on the front with the Trackspeed BBK and stock rears with XP8s for now. As for tires, I'm on street tires as I get back into driving on a track. It's been awhile so I'm starting over with the basics. Perhaps in a year or two I will go with a decent set of tires. I would rather be slow with cheap tires than slow with good tires at this point.

Can't give you an informed opinion about your brakes. I have always run hawks. Though I did borrow a set of carbotechs' in an emergency and they worked well, but I don't remember the compound.

I can appreciate that thought process on the tires. The one thing that is nice about driving street tires is they are slippery. This means that you can learn car control, and feel the car drift at slower speeds. Of course you will still be on the edge when in a drift and it can actually be harder to catch a car if it steps out a bit on street tires. But they are a great teaching tool, I always recommend driving laps on street tires if they are available.

You should track down some of the SM guys in your area and see what they have available as take-offs. Some times you can get lucky, and find good rubber for next to nothing. SM's run on 205-50-15 and a 15x7 wheel. I know your car will easily overpower the tire but they would be good to practice with.

One of the things I do with students on track days is have them run on their street rubber then send them back out on race rubber. Usually when they come back in it is like a revelation, you can see the light has come on and they really start to understand the whole traction equation. All of a sudden the car has tons of traction left after turn in and they can drive through the corner. I usually here something to the point of "I am getting (select gear of choice) 50 foot sooner out of the corner., and Im 300 rpm higher at the next braking zone".

The back to back between street and race rubber really shows the short coming of the street tires, and allows them to start sneaking up on the entrance and exit speed and gives them a feel for how stable the car can feel at a spirited pace.

How much track time do you plan to get over the summer?

One other thought, when you drive at the track try covering your speedometer and relate everything to gears and rpm. Speedometers can be a distraction on the track.

Good luck and enjoy the track time!!

I'm hoping to do at least one track day each month starting in May. Just lapping days and I'm looking into time trials. The street tires will work good because I can run them in all weather conditions and also when I go on regular drives with the locals. Hopefully I can get a good feel for the car before it ever gets out to the track so I can purely be out there improving my driving instead of fighting with the car.

Just be cautious, road racing can be hazardous to your drag racing career!!! There is something about driving a car at the limits for an extended period of time that becomes very addictive.

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um why else would a chalenge you to a foot race newb? :loser::noob: :jerkit: come on get with the program

Sorry when you got your back to the wall you kind of get protective. I guess I just don't know how to read your sense of humor.:facepalm: 7,700 post in less than 4 years, do you even have time to drive your car??:laugh:

Care to make up your mind?

For all the blabbing you did about traction circles, you neglected to mention that poor brake proportioning will lock the fronts up before the rears have used up all their traction. All the rear traction in the world doesn't help if the fronts have none. Add a bias valve and suddenly the rear brakes are actually doing something, which means you can stick it in deeper and step harder before the fronts lock up - and you can rotate the car while you're still on the brakes, and tune the way the car makes that rotation (not at all or very quickly). The suggestion that he simply needs more practice braking instead of a bias valve is laughable.

Open your world a little. Just because it's not legal in SM doesn't mean it won't make the car faster and easier to drive.

You think I don't know this? My original statement was made before I realized that he was running 4 pot wilwoods up front. So, of course a proportioning valve will help. As long as the rest of the system is free of flaws.

Blabbing huh? Okay I will not attempt to share info in the future. Do you think everyone at this forum is well versed in track driving and the concepts that I was trying to share. My fault, I wont attempt to share anymore information.

Instead of paraphrasing my post, making it look like I have done a 180 on a whim, quote all of the post, so it can be seen that once I realized I had made a mistake about his brake system, I maned up and said so.

Had he been running a factory system as I first thought. I would have stuck to my, you need more practice statement. My mistake, I corrected it though. Of course I realize that you don't make mistakes. Did you even bother to notice that I stated, I didn't realize the brake upgrade. Or are you so shit fire in hurry to throw down and start a fight that you don't care that I admitted my mistake and given the new information changed my point of view?

Given the fact that the OP is new to road course driving. I intentionally left out trail braking and car rotation. It is not exactly road course 101 in my opinion. I hope that you will agree that the art of trail braking for car rotation is a more advanced concept that a green track guy should not be trying.

The OP and I have had a good exchange. It seems I have ruffled your feathers, and in my opinion you are looking for a fight because of your paraphrased quotes. My about face was based on finding more information out about his car. My fault for not asking more questions up front and just assuming he was running stock calipers.

Fuck, anyone else want to throw down with me?:facepalm: