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Discussion Starter · #1 ·
So, I'm getting ready for a 12,000+ mile ride cross country and of course need to start with fresh meat front & back. Pulled the wheels off today and noticed this weird wear pattern on the rear. The front isn't worn as much so it's hard to determine if it's happening to them as well. I have a theory as to why, but I really don't remember seeing this before on this bike. I have put 90,000 miles on it in the last 3-1/2 years and running Dunlop AE's for the last 2 sets (since the Michelin CIII's vibration issue). Never saw it before on the CIII's either. So, the theory I have is, more actual wear/miles while taking left hand corners because the turning radius is larger/longer compared to right hand turns that are smaller/shorter. More wear on the other side of the tire in England, Australia, etc. because everything is reversed. Sound about right, or crazy, or am I missing something important with my tire alignment/mounting/balance or something else?

Thoughts? TYIA.........


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Is the picture reversed? If not, The tire may be mounted backwards. What air pressure do you run? I have never seen that much difference from side to side wear. I would check alignment for sure. When looking at the rear of the front tire the tread usually will look like a V. The rear is usually Opposite when looking from the rear at the rear tire. /\ There should be a direction arrow on the sidewall somewhere.
 

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Discussion Starter · #3 ·
Is the picture reversed? If not, The tire may be mounted backwards. What air pressure do you run? I have never seen that much difference from side to side wear. I would check alignment for sure. When looking at the rear of the front tire the tread usually will look like a V. The rear is usually Opposite when looking from the rear at the rear tire. /\ There should be a direction arrow on the sidewall somewhere.
Lol..... EXCELLENT catch sir! Yes, the picture is reversed because when I took it, and sent it to my computer, the sprocket was on the right side, (taken from the front side), and I didn't want that to confuse the fact that the left side was being worn abnormally. (Too lazy to go back out to the shop and retake the pic, lol!)

In an effort to troubleshoot the cupping that I have experienced on almost all tires that I have run on my different bikes, Michelin, Dunlop, Metzler, ect., I recently started running the rear tire at 41-42 psi, and the front at 37-38 psi, or 2-ish psi higher than spec'd in the owner's manual. The front still cupped as bad as normal but the rear cupped a little less.

The thing that confuses me is how high up the left side the excess wear is. Not down close to the center of the tire where most of the riding is done. To be in that area, the bike has to have quite a lean to it.
 
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I mean, I run Dulop AEs and most of my riding is around town, probably take as many lefts as rights and mine haven't worn unevenly like that.

I have slight scalloping in that area by the end of tire life, but it's on both sides and a small amount of scalloping like what I have is normal and if you look at my tires, the scalloping is backwards front and rear but, so is the tread pattern (if you turned both tires so the tread pattern is facing the same way, the scalloping is on the same edges of the same treads, I'll refrain from trying to say leading or trailing edge of tread because I always confuse myself looking at them). It's little triangle scallops but they are subtle (can't hear noise caused by them or feel it).

But anyway, my wear is even on both sides. I would only imagine wear like that based on turning left or right would be because of making a lot more left turns than right, I don't think that left turns being slightly wider/longer than right turns (in America) would make that much of a difference. I currently have almost 14,000 miles on my tires (Dunlop AE, rear is MT90-16 or 130/90-16 and front is MH90-21 or 80/90-21). You can't even really see the scalloping in the pics of the rear, you can see it a little on the front from where I rolled through cat litter and as you can see, they're subtle. For full accuracy, DL makes both tires in both sizes and these are currently MH90 front and 130/90 rear, even though MT and 130 is the "same width", there are some subtle differences between the two (MT has a 74 load rating and 130 has a 73 if I remember right, also one of them has a marginally wider overall width because it has slightly more sidewall bulge, but I can't remember exact details, though I have run both an MT and a 130 rear and they wore the same on my machine).

A side note, that rear tire is multi-compound (softer outsides, harder middle), but the front tire is not, that's according to Dunlop.

Anyway, book recommend PSI (stock tires would be Dunlop 402s) is 30 front and 36/40 (solo/2-up) rear. Dunlop recommends for AE for mine 30 front and 40 rear. For the life of these tires, I have run 32 in the front and 40 in the rear. First two shots are the rear, last is the front:
Tire Wheel Automotive tire Vehicle Synthetic rubber
Tire Wheel Automotive tire Tread Automotive lighting
Tire Wheel Automotive tire Bicycle tire Synthetic rubber


As you can also see, my rear is a little more squared off than yours. Pics make the tread look deeper than it is, I am .048" from hitting the wear indicator on the front and .080" on the rear.
 
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I would look at the shocks with that wear just thinking the left doing the work and maybe has torqued the swing arm bushings. 90+K miles thinking bushings.
Just my $.02 worth
 

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The thing that confuses me is how high up the left side the excess wear is. Not down close to the center of the tire where most of the riding is done. To be in that area, the bike has to have quite a lean to it.
This makes perfect sense, when you think about it.
The tires are tri-compound, the center tread is the hard rubber, then is gets softer and stickier working up the sidewall. So the chicken ring area of the tire is will wear much faster than the centerline. Especially on the roads in your neck of the woods! Steep twisty mountain roads are going to put those sides of the tires to task. I appears you like to get some on those left hand sweeping turns! (Obviously a better view through the turn vs. a right hander). So we approach the right turns with greater caution and more reduced speed. Resulting in less time at or near the chicken ring over the life of the tire. Just my .02
 
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I would check the rear alignment with an old metal coat hanger. Make a 90° bend on one end about 2" and slide a small tight fitting o-ring onto the opposite end. Now pop the two chrome caps off the swingarm pivot shaft. Put the hanger 90° end into the center of the pivot shaft and extend the hanger to align with the center of the axle, slide the o-ring to that position. Take that measurement around to the opposite side to see if it matches, should be the same for both sides.
 

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Discussion Starter · #8 ·
I would look at the shocks with that wear just thinking the left doing the work and maybe has torqued the swing arm bushings. 90+K miles thinking bushings.
Just my $.02 worth
I don't know if the shock(s) is/are bad or not, and can't check them right now as they are on their way to Big Bear Performance to get rebuilt along with my front forks and cartridges before my next trip. The shocks are a set of #3 - #3's that Howard at Motorcycle Metal built for me 45,000 miles ago. They looked great when I boxed them up as far as any leaking or damage, but I'll have Kevin pay special attention to them during the rebuild. I'll grab the swing arm today and give it a good shake and looky-loo. You're right, the bushings may be due to be replaced. We'll see how a set of freshened up shocks and the new tires look when I get back in late July after 12,000+ miles. Should be damn near time to swap out that rear tire again when I get home.
 

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Discussion Starter · #9 ·
I would check the rear alignment with an old metal coat hanger. Make a 90° bend on one end about 2" and slide a small tight fitting o-ring onto the opposite end. Now pop the two chrome caps off the swingarm pivot shaft. Put the hanger 90° end into the center of the pivot shaft and extend the hanger to align with the center of the axle, slide the o-ring to that position. Take that measurement around to the opposite side to see if it matches, should be the same for both sides.
I used to check the rear wheel alignment on some of my other bikes that way, but to be honest, with the cammed axle adjusters, I just assumed that they were all good. I get more concerned about proper belt tension. Wouldn't hurt to check that when I put everything back together after I get all my parts back.

For what it's worth, the bike does handle well with no hands on the bars for that rare occasion when I NEED to take both hands off the bars. Not a scientific test, but just a note.
 
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Sounds good I happier than a hongry hog at a full trough to git 12K on rear tire. Usually manage to pick up metal, slice them or just change early for long trips.
 

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Another thing that could be going on is the vertical drivetrain alignment. Drivetrain inclined more one way than the other. That can be diagnosed using an inclinometer attached to both brake discs.
 

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Discussion Starter · #12 ·
Another thing that could be going on is the vertical drivetrain alignment. Drivetrain inclined more one way than the other. That can be diagnosed using an inclinometer attached to both brake discs.
Have to research that....... (y)
 
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Could also be the roads where you live. I have lived places where the roads are significantly crowned, so much that you can easily see the arc of the road from curb to curb. Probably not enough to cause the wear you are seeing, but could contribute.
 
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Discussion Starter · #14 ·
Could also be the roads where you live. I have lived places where the roads are significantly crowned, so much that you can easily see the arc of the road from curb to curb. Probably not enough to cause the wear you are seeing, but could contribute.
It could, but I don't think it'd be that far up the side of the tire tho.....
 
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