This past weekend (actually only on Sunday) I experienced some small chunking on my Falken tires.
I have a 2k2 Civic Si completely stock and I mounted Azenis tires on 15x6 stock wheels so I run pretty high pressures 48f/40r cold. After a couple of runs the pressures go up to 50-52f/42r (there was a difference in lf and rf because there were twice as many right hand turns.) But, by about the third run I noticed some chunking on the tires - nothing extremely serious but enough to alarm me. They were also overheathing a lot which is probably because of the pressures and outside temp (CA) but it seems I cannot go any lower (15x6 wheel does not like that.) On the fifth run I was particularly careful to be smooth. The tires temps did not go down.
Are there any ways to avoid chunking? What are your suggestions?

Thanks

 

Woah...tires pressures waaaay to high for Azenis. That might explain why they are looking bad, although I have not heard of Azenis chunking either on the track or autox.

If you overdrive the car, heat the tires too much and have too much air pressure, I'm sure it could happen.

Next time, on 15x6 rims, try running high 30's in the front and about 30 in the rear. Adjust pressures accordingly, less in the rear for better rotation, but no more than 40 in the front. And adjust pressures when the tires are warm, because Falken's gain about 4lbs when hot.

 

Out of curiosity, how does this car handle stickier tires with the stock suspension? I have heard that they are a rollover hazard with the stock suspension and R compounds, was wondering if your experiences (with Azenis)would refute/back up that claim? I test drove that car, and found that there was a lot of body roll with the POS stock Michellins, but nothing to get all that alarmed over.


[Modified by madhatter, 1:14 PM 10/14/2002]

 

Were they actually chunking, or just picking up bits of rubber from the track? Where was the chunking occuring on the tires (center, left, right, all the way over, full circumfrence, etc)? Those tire pressures sound way high.

As for stickies on a stock car... the Azenis has nowhere near the grip of true R compouds, so should not be an issue. Also, the few incidents I have heard about occurred while autocrossing (not track days), where the transitions tend to be more violent (quick slaloms/lane changes seem to be the common theme).

 

focus driver rolled with azenis. so it is possible.
as for the pressures, i run mine at 30-40f and 36r and mine don't roll. i'm on stock suspension too, although my car is lighter than an the new civic
-spenc

 

Not really. If the chunking had been around the center, then too much pressure would have been the culprit (and reducing it a bit might solve the problem).

Did this occur on all four tires? Or left side only? Or front only?

The left side tires should get hotter than the right (most tracks run counter-clockwise and have more right handers). I have to start my LF tire 2-3psi lower than the RF.

If it happened only on the fronts, it could be explained by entering corners too hot and giving too much steering input. The Si's tendancy to push makes this easy to do.

If it happened only on the rears, well, I've never seen that.

 

This is my idea on why the Azenis chunk. Take a balloon (1/2 inflated) and dip it in some chocolate. Let it harden. And then blow it up some more. The balloon inflating will try to make the chocolate expand too, but since it's not as elastic as the balloon will develop cracks in the chocolate coating.

I think the same applies to Azenis. Too much air pressure and it will do the same and cause chunking

 

Huh? This is a tire and it is completely made out of rubber. A lot of tires chunk on the track/autox and it has nothing to do with over-inflation, although in this case it may be that with a combination of other things (soft suspension, driving style, etc).

 

You talk of overheating.....have you tried spritzing the tread down with a spray bottle full of water after each run (or whenever they overheat). I know of quite a few people that do this, but I have no idea if it will help the chunking problem.

Out of curiosity, how much auto-x experience do you have?

 

I routinely run my azenis at either 35 front 33 rear or 34 front 32 rear [-cold- ] depending on ambient temp; could everyone note hot/cold when listing pressures, would make comparison more concise.


[Modified by bb6h22a, 1:42 PM 10/14/2002]

 

Your tire pressures are way too high. On the other hand, the Azenis squirm too much for me at 30psi. I've had good results with 35f 36r cold.

 

This works for autocross, but not for track events. Unless you want to pit every lap and have a crew member hose the tires down (Dennis was at VIR with NASA). I have no idea where Nick was running (I assumed at a track). If you are heating them enough to chunk at an autocorss, you are doing something WAY wrong.


[Modified by Crack Monkey, 2:05 PM 10/14/2002]

 

Azenis need to be cooled down between runs without a doubt (for optimal traction). But to chunk them at an autox??? I've never seen that.

 

[hijack]He was at VIR? Which group did he run? what color car? [/hijack]

I run around 37-38 cold, and I actually have some cupping in the tire. (225/45/17)


[Modified by elgorey, 5:35 PM 10/14/2002]

 

I experienced some minor rolling over on the outer edge with 37f/37r (cold). I also have 15x6" wheels. 15x7" really would be the best, because there is a lot of tire on the 205s.

However, take your driving style into account. I was pushing a lot, when this was happening. I cleaned up my line the next time out and ran 40/32, and there was no problem whatsoever. I forgot my tire guage, though, I couldn't adjust appropriately, but I bet I could've ran 37f (cold) without rollover problems.

 

"You talk of overheating.....have you tried spritzing the tread down with a spray bottle full of water after each run (or whenever they overheat). I know of quite a few people that do this, but I have no idea if it will help the chunking problem.

Out of curiosity, how much auto-x experience do you have?"

Yes. I had to spray them with water in between all runs. I was very happy with the grip. I admit the tire pressures are too high. However, that works the best on my car. Remeber this is not a 1900lb civic - this is a 2750 lb civic. Also, A BIG ISSUE IS THE NARROW rim. On 15x7 rims I run 38f/30r (cold) and adjust from there depending on concrete and/or weather.

But on 15x6 rims I get some weird reponse from the tires and I post about 1/2-1s slower times on a 50s course. At those pressures I get some sidewall flex that basically feels as if the tires are about to fall of the rims. I am not the only one running these pressures in our local club. . . There are other people running 50f/26r (cold) on similar weight cars.

As far as the experience: I used to drive a FR car and this is my first autocrossing FF car. However, in the last 2 months I have "calmed down a lot" - that is I adjusted my entry speeds and line. My times are less than 1.5s behind top guys on R tires.
I did not have enough time in between all runs to check the temps - but after 3 runs I had even temps accross all tires (although there was some disparity between left and right tires due to the design of the course - right tires were hotter and thus there was about 1.5 PSI more pressure in them which I had to adjust.)

Also, the chunking was very minor - I posted this to get responses from you guys before something worse occurs. Maybe the chunking was the wrong term. This is what happened: first there were some "blisters" that popped up and then those blisters basically fell off. I thought that was just because the tires were too hot. But a more experienced autocrosser said that that's how chunking starts.

In addition, THIS NEVER HAPPENED BEFORE. I autocross just about every weekend with various clubs.
As a sidenote: GRM 2k2 Civic Si with KDs are running 50f/50r (cold.)


[Modified by nikkotyper, 1:32 AM 10/15/2002]

 

I'm thinking that he must have been in the stock looking blue WRX. I ran around with that car for a while in Intermediate, though I don't think it ran every session with Int. I did see him line up in the Prelude for the last one, but never found him on track.

[edit] Guess george confirmed it.

sidenote - 6 sessions and i never did see Evan on track. I did have quite a bit of fun with the Camaro's though...


[Modified by JeffS, 8:13 PM 10/14/2002]

 

I've been thinking the same thing lately, too bas the stock rims are only 6", a little narrow for today's 205/50/15's.

 

I ran 30-32f and 36r (cold) with no problem.

 

hmmm I never saw him. I did get accused by another instructor of holding up a black M3. I told him i was never in front of an M3 and he said it must have been another blue WRX. I wonder if that was him?

Jeff I ended a couple sessions a few cars back from you, but we never got to really run. I lined up once behind you but then my instructor was late

 

I used to run 39f/33r according to what my pyrometer said, now with 3mm left I changed the air pressures to 41f/36r.

 

You should listen to these guys! They know what they are talking about. You dont need those rediculously high pressures!

Well I have a 2600 lbs Integra running 15x6 wheels and 40-41 lbs front and 35 or lower in the rear. There is no need to run those pressures, Azenis like lower pressures. This weekend, I beat the compitition (running Azenis) in Street tires by over one second I think, final results not yet out.

You will be happier with 40f/ less than 35 rear. Contine to adjust the rear for rotation. Reduce rear pressure for more rotation.

 

if the chunking was occuring only on the outside edge at the top of each tread block it tells me that the pressure was too high and he was over driving the tires. i had the exact same thing happen to my front tires at gingerman at the expo. each missing chunk looked like a pencil point, wide at the top and then tapered to a point. if you were to stand over top of the tire each chunk was at a slight angle, wide part at the top right and point at the bottom left.

this past weekend at VIR my car was driven in the instructor and intermediate sessions with lower pressures and less aggressivley and they look as new as when they were mounted on thursday.


[Modified by lanceh, 10:46 PM 10/14/2002]

 

OK guys. I will try lower pressures again. I do not think I was overdriving them. As I said, once I noticed the increased temps, I paid special attention to the line and braking. The runs were very smooth and the times were good. In a month or so I will be going to a local track and I will experiment a little more.

Now, in response to somebody's comment about autocross vs track tire usage. I believe that autcross taxes the tires more than a track simply because the tires have no time to cool down. On a track, every straightaway technically cools the tires (a bit). On an autocross - tires temps go up with every revolution.

 

Same here...using 30F/32R...they get real hot and real slippery about 25 mins. into a session, but other than that they are awesome for a street tire, and no noticable chunking.