Abnormal tire wear, looking for setup advice.

Hey all,

Been off the track for a while. Took the rear shock (ttx) off my r6 to get serviced and now I'm getting odd tire wear. I as a rider have not changed in weight and I did my due diligence to note the shock settings before service. I had the height/sag set previously so I'm confident those settings are right... can anyone give me some ideas on whats causing this? I've gone up/down in tire pressure and its not that. Feeling rear tire spin up when trying to throttle out of corner....
Advanced rider, .95 rear spring, 3 turns of preload in, 15/28 click IN on compression and 20/28 IN on rebound. Dunlop Ntec 0129. Any help would be appreciated.

 

What pressure(s)? What track? What track temp? Was the tire new? If not, how many laps/heat cycles/sessions?

 

Pre shock service i always ran this at 24psi..... i tried it at 22 and 26 with no results. Running at mid-o, 85 direct sun, not sure what track surface temp was. This tire has had 1 previous heat cycle (6 laps) on it before this day. The first few sessions of the day i wasnt having this issue as i was getting back up to speed. Id say after lunch, so 4th session this was starting to become an issue. Tires on warmers all day.

 

@Dblock55 24psi off the warmer or off the track?

 

Interesting, I was as mid-o yesterday and had the exact same tire wear. Mid O always destroys my tires but I rarely see anyone else with the same problem. I had started at 27 off the warmers and went all the way down to 24. No fix

 

Off the warmers.

 

You've got the same issue I have. Ive run this track many times without this issue. I would say the keyhole being repaved could be the culprit but that doesnt explain the left hand side of the tire being the same.....

 

Target pressure for the 180/60 Slick is 24psi off the track. The amount of pressure you gain from warmers to the track really depends on your pace, your bike, the track, the track temp, and the weather. For an A-group rider on a warm day on a 600 at 2pm, Id guess you are gaining ~2psi. A slower rider or a colder session will gain less pressure. So running the first two session not up to pace will work fine with 24psi off the warmers. But increasing pace and track temp later in the day will push that out of range.

Dunlop's softer rear compounds don't respond well to lower track temps, heat cycles/wear, or any mistakes in setup. And once they start to tear, you may only have 1 session to fix it. I have plenty of rear takeoffs from MA practices and races, ie tires with 10-20 laps on them. Getting a full trackday out of them with only minor tearing seems to only work on hot non-abrasive tracks. On cold or abrasive tracks, they barely survive 1 session. The 0455 and 0097 are better compounds for trackdays. They last longer and are far less susceptible to tearing. On an abrasive freshly-paved track, even the 0585 works great.

@Dblock55 There likely are things you can do to your setup to improve tires wear. But you'll want to work with someone at the track, so we don't have to guess going off of so little info. Off-hand, your rebound at 8 OUT might be too slow. I run mine much faster at 15 OUT. But I have no idea what valving you are running so that's just a guess.

 

@standmx13 Thanks so much for your input. I did go down in pressure for a session and up in another and it didnt really do much in terms of wear. I added 3 clicks IN to compression because the rear felt super soft over some of the bumps and that really wrecked the tire so i backed that out.
Overall the bike actually felt good, just initial throttle input generated some tire spin so i really had to feed it in gently. There was no one at the track there to work with... i really need to get with someone.
On another note, these are MA takeoffs, so maybe you are right that these tires just cant take a whole day? I do have a 0097 that ill try next.

 

Is it possible that the tire is too hot and under inflated? I was comparing the picture above to some pictures of “hot tear” online and it looked like the pattern was much closer to overheated rather than under heated.

 

Its not tire pressure. I thought that too after looking at pictures, which is why I changed pressures. No effect.

 

Isn't 24psi off the warmers too high for Dunlops. I remember shooting for around 20.5-21 psi off the warmers.

 

How bad was the tire when you changed pressure?
If it was bad enough no matter what it won't clean up

 

With how slow the rebound is, I’m neither surprised that adding more comp damping made the tire worse and that the tire spins easily.

Post your valving spec if there’s a sticker for it on your shock. Maybe someone will know good base setting for the clickers.

 

Oh some temp was def off. But was it the carcass temp, the compound temp or the track temp…

 

I've been off Dunrops for a few years but I recall running really low pressures HOTW....like 18 psig. Has Dunlop changed their carcass?

 

Are you sure the spring has the same preload amount? Ie measured the spring for installed preload?

 

I thought so, too. I stay between 21-23 off the warmers when I use the Dunlops.

 

For those questioning the temps. Here is the chart off of the dunlop website. Also the moto america racer i buy these tires off has the same recommendation and told me the Dunlop tech says these are off the warmers. So im going to say i have it on good authority these are right .

@noles19 It wasnt too bad when i started playing with it.
@crazymofo I hadnt done that and i should've. The only thing that couldve changed the preload is the nitrogen charge right?

 

Dunlops published pressures are "safe" recommendations. They will work for most people in most conditions. Unfortunately, that includes B group trackday riders on cold tracks and Expert racers on hot tracks. B group riders on a cold track can absolutely run 25psi off the warmers. They will lose heat and pressure when riding, resulting in 24psi off the track. An Expert racer will put more heat into the tires and will probably use 22psi off the warmers to get to 24psi off the track. Before this new website, Dunlop published "21 cold / 23 warmer". That's it. Every racer learned real fast that those numbers weren't exact, especially when 19psi warmer worked best.

I rarely talk to Dunlop at MA events about pressure off the warmers. The convo is always about off the track pressure. They are super helpful. You just gotta learn what to ask.

Heres how I find my ideal pressure(s) at an MA event. I got out for the first session with some warmer pressure, usually 21psi. I do some laps, come into hotpit, and measure the pressure. If its not 24psi, I know I need to adjust my warmer pressure by the same amount. In the second session I run that new warmer pressure. I measure track pressure again to see how much the change in ambient & track temp has affected the tire pressure. Then I know for the following day what my warmer pressure should be for morning and afternoon sessions. And after all that, sometimes 24psi off the track isn't perfect. But straying outside 23-25psi has never gone well.

crazymofo means the spring preload. You have a preload adjuster on the shock, the small 8mm hex by the spring. It's 0.5mm preload per turn. However, total preload is dependent on where the adjuster is installed, ie installed preload. If the tech that serviced the shock put the adjuster at a diff spot, changing the installed preload, your old setting of 3 turns (1.5mm) preload is now incorrect. Unfortunately, if you didn't measure the installed spring length before and after the service, you won't know if it changed.