Tire wear gurus: what's happening here?

If anybody can help with some solid input/advice on this I'd really appreciate it. Ran into a situation running a couple of trackdays @ Mid-O this week while shaking down my racebike where the rear tire was wearing oddly; first impression was that this was rebound tearing, but stiffening the rebound 2 and then 4 clicks over different sessions to slow it down did nothing to change the wear. Also tried taking 2 clicks off compression.

Current setup and rubber is as follows: 2011 ZX10r, Bridgestone 003 race, med 'V' front and med rear, sag @ 30/39, forks dropped 5 mm, shock raised 5 mm (Ohlins 30 mil front/TTX rear, 120 spring, 245 lbs rider). Hot pressure set @ 28 rear, which worked perfectly on my previous racebike (CBR1k). Front tire looked minty after 200 track miles, no issues with turn-in on the front. Rear wants to run wide on exit throttle, will most likely shim the shock in the future to address this. Will also be switching to R-10s for racing, but wanted to get use to the bike on tires I know. Also, the suspension was set up by a reputable shop before I took the bike out.

Photo 1: rear tire after three sessions. Dry, hot track.



Photos 2 and 3: rear tire after a full day.





No issues with the tire spinning up excessively, and other then wanting to run wide it gripped when needed. Always ran with warmers, so I don't suspect cold-tearing to be a factor but maybe I'm off.

If anyone can point me in the right direction, I'd appreciate it. Thanks in advance for any help :up:

 

I remember Dave Moss covering this exact situation in one of his videos. Good luck finding it though...

 

I'd try dropping pressure a bit and making sure that you are not whacking the throttle on corner exit but rolling it on.

 

try upping the compression 2 clicks at a time
looks like the rear is a bit soft and overloading the tyre

any more then 6 clicks added, then add a full turn of spring preload instead

cheers.joe.

 

Whoahh if anything I'd say too much spring

 

Looks like the rear is hopping.

This kind of looks like it, that same intermittent wear pattern back and forth, in this case he said it was rebounding too slow

http://www.youtube.com/watch?v=XUNL_KtT0Qg&feature=related

 

Doesn't look like a pressure problem. I remember hearing Dave Moss saying that if it "oscillates" it's a hydraulic suspension problem. Heres the full video, I'm sure it addresses that problem.

http://www.onthethrottle.com/howto/dave-moss-unsprung-tire-wear/

 

That makes perfect sense; instead of rebounding too fast like I initally thought and adjusted for, it's actually rebounding too slowly and I should have adjusted it in the opposite direction to loosen it up (it seems).

Thanks for all the input guys - and if anyone else has suggestions I'd like to hear them :up:

 

Problem found, the physics is mind boggling!

Good luck with finding the solution, I love these threads btw as I'm trying to learn tire reading too.

 

Speeding up the rebound might have helped your trouble finishing a corner as well.

Rebound too slow, holds the rear down/choppers out the front and you run wide.

Maybe.

 

We qualified a virtually bone stock 2011 ZX-10R at mid-oh last weekend for the superbike race. One of the biggest improvements we made was the rear spring rate....that bike takes a TON of spring. We ended up running a 700 (between a 120 and 125 Ohlins) and could have gone more....our rider was around 190.

Also, was your TTX revalved for that much spring?

BTW...mid oh eats tires. Not sure of your pace, but a whole day on a set there is pretty darn good.

If you added 4 clicks of rebound on the ttx....that is a HUGE change....and also probably the wrong direction IMO.

 

How is the track surface? Irregular and bumpy?

Did you change tire brand? Or Shock?

You can tell the leading edge is sharp and the trailing edge is rounded... This changes on the sides...

If I am not mistaken it is a rebound issue... I would say less rebound would help...

Now as for the irregular pattern... it seems like the compression is also a bit stiff, not allowing the tire to move easily... It seems to be tearing because it is the suspension is pushing against the road, when it should be compressing... I would say less compression as well...

How is the spring rate related to rider wight? How much sag do you have on the rear?

http://www.onthethrottle.com/howto/dave-moss-unsprung-tire-wear/

Luis


Go back to usual tire pressure...

 

Sounds like there is a ton of good suspension thoughts here.

I'd like to also say, on tracks with quite a bit of grip I have had the same tipe of tire wear from too soft of a compound. harder tire worked great and suspension was dialed, put on a new tire one compound softer and had the same results that you are showing after 20 laps... Just a thought. Check with other riders on the same tire and compound before you start clicking away.

 

I agree with this assessment. Rebound is too slow, meaning the tire is having to work like suspension and compress to absorb the bumps. Would try taking a few clicks out of shock rebound, should clear up with a few more sessions.

 

I would add that the tire probably won't fully clear up all that much, even if you do make a change in the right direction. Just something to note when you fiddle with the clickers and go out for another 10 laps. It's going to be really hard to see an improvement on the same tire.

 

You should see me on the SV - it's like a polar bear riding a rollerblade I tell ya.

That seems to be what's happening - thanks :up:

Shock was set up @ Ohlins in NC; I'll find out if they valved to suit the spring. I saw a few folks getting their tires chewed up, but it was the wear pattern on these that concerned me. Only ran 39's, first time on this bike and I'm still trying to get used to it - plus I wasn't confident with where it was ending up on corner exits. For example I'd come out of T1 on the throttle and the bike kept wanting to drift out into the grass.

Question if you don't mind - were you guys running any additional spacer on the rear shock?



Kiggy - yeah, I'm going to back out the rebound next time out with a fresh rear and see what's happening from there.

 

I will try and get you more info this weekend on where our exact setup ended up. Stiffer rear spring may help your corner exit...if it is infact squatting too much on corner exit.

More rear preload and/or ride height can help also. Try adding preload and see if it gets better....if it improves your exit line, but you start to lose grip, then back off some preload and add ride height. make sense?

Also, where are your clickers at on the TTX?

 

Was the traction control on?

 

I know you said 2011 10R, but is there any chance the bearings are shot or something installed incorrectly?