Tire Cupping??

[Stig / Major Tom]

I have 4500 miles on these Michelin City Grips - inflated properly, balanced, and showing no wobble or tire run-out when I spin the rear.
Yet, I note this cupping of the rear tire only. The front is smooth to the hand, the rear has this cupping. Web searched and found the first photo - author says this is normal wear, and is not an indication of suspension issues.
Scoot corners and handles perfectly.
What's going on here? Nothing? Or something?
info I found:


My rear Michelin (with plenty of tread)

[kneeslider]

I am assuming you corner aggressively or at high speeds.

It's normal.

[Stig / Major Tom]

I am assuming you corner aggressively or at high speeds.

It's normal.

Yep, I'm kinda thinking it is fairly normal wear.
And, THANKS for the compliment....although - obviously you've never seen this senior on his scoot! (I only get aggressive if someone tries to line cut me at Tim Horton's)

[kneeslider]

Good Stuff.

You can actually determine how the rider rides by checking out their tire wear/tire condition.

[donandrews]

Yep Kneeslider...my shop mechanic always gives me flack because I still have some of the little "nipples" left on the sides of my tires after 5000 miles.  He tells me I'm a long way from the maximum corner speeds, but I'm OK with going into a 15 mph corner at 15 mph and accelerating out at 25. Can't figure out how to put my knees down in the corners while sitting on a scooter anyway.
Peace and Ride Safe

[zombie]

That "cupping is from an alignment issue. I fought the same demon on my ZX. If you get an "O"ring big enough to fit over your throttle and slide it between the brake master, and the end of your grip it will make a cruise control of sorts. Point is ride about 40-45, and let go of the bars. You WILL feel the scoot try to run to one side or the other.
The side it falls toward is the side you need to move back. What that means is you have to shim the entire engine backwards on the side the bike favors. I did just that by elongating the engine mount hole in the frame, and cutting small crescent moon shaped nibs of steel to act as shims until I found the correct size to eliminate the no hands pull of the bike. You will have to add a fender washer on each side to hold your shim in place.

Yours is not too bad at 4K but my BRAND new Pirellis looked like yours in 150-200 miles

[kneeslider]

That "cupping is from an alignment issue. I fought the same demon on my ZX. If you get an "O"ring big enough to fit over your throttle and slide it between the brake master, and the end of your grip it will make a cruise control of sorts. Point is ride about 40-45, and let go of the bars. You WILL feel the scoot try to run to one side or the other.
The side it falls toward is the side you need to move back. What that means is you have to shim the entire engine backwards on the side the bike favors. I did just that by elongating the engine mount hole in the frame, and cutting small crescent moon shaped nibs of steel to act as shims until I found the correct size to eliminate the no hands pull of the bike. You will have to add a fender washer on each side to hold your shim in place.

Yours is not too bad at 4K but my BRAND new Pirellis looked like yours in 150-200 miles

Since the rear of our scooters doesn't allow for rear wheel alignment, then such a drastic out of alignment should be sorted out by your dealer?

But the issue here with the cupping isn't an alignment issue i think. if it was then the cupping would only be on one side of the tires. The OP's had the cupping on both sides of his tires, and indeed mine are on both sides too on both my scooters.

[Stig / Major Tom]

Since the rear of our scooters doesn't allow for rear wheel alignment, then such a drastic out of alignment should be sorted out by your dealer?

But the issue here with the cupping isn't an alignment issue i think. if it was then the cupping would only be on one side of the tires. The OP's had the cupping on both sides of his tires, and indeed mine are on both sides too on both my scooters.

Latest info I've found suggests that the tire could use 2 or 3 more PSI....even if currently running spec'd & correct inflation PSI - the rider might be ....how shall we put this?...
Tire might be slightly underinflated for its daily burden. (or it could just be a normal pattern for this tire and this scoot)
Geez, I'm going with the latter...

[zombie]

It's hard to tell from the Pict. if it is cupping one direction or the other.
Yes under inflation or overloading will cause this, as well as worn or improperly adjusted shocks. Also letting the tire sit in an oil stain in the drive/shed will swell the tire causing the same result.
You all have to keep in mind these scoots are built in a tiny factory using nothing more than bicycle jigs to clamp them together for robotic welders to tack them together. Take a real close look at where your frame attaches to your engine mount. I mean REAL close. You will see there is NO filler metal used in the weld. There is NO weld bridge between the frame, and engine mount. The metal is a Chromoly alloy that is simply melted together. To make it worse it is uni-directionally welded meaning it does walk or deflect during welding. Almost every one of our bikes have a tracking issue but most of us never realize it.
 Set a makeshift cruise control, and find out.

I have had the worst luck w/ rear tires until I figured out the frame/engine mount alignment was off 3/16" from the factory. Those that knew me here years ago will tell you how many tires I went thru. In order to ride no hands I had to FIGHT the scoot way over to the left, and it was not comfortable at all.

Point is once I found the problem, and made my home spun alignment slot, and shims the bike tracks true, and the uneven tire wear has actually corrected itself, and taken the cup out of the tire.

The only way that I know to verify all this is a no hands ride. There is no other point of reference on the bike that can be trusted to be true because of the assembly methods used.
The goose neck or steering tube IS hand welded. Take a look at that, and then at the frame/engine mount, and it will be clear to you what I mean.

[Vivo]

Right Zombie... it's a scooter...    I have no cups on my tires so I can't share...   However, one question arises on that shock thing... No 2 shocks are exactly alike, right? so, is it safe to say that a monoshock is better than 2? because 2 at the rear may have different "tuning" and affect performance... 

[zombie]

In a very big way... Yes. BUT it has to be a load centered mono shock to be of any real benefit. Our Mono shock scooters are all side loaded, and actually create more flex in the frame.
 That's why I chose the local air fields runway to speed run instead of the drag strip in Tallahassee. The runway is much flatter.

That brings up another very good point that applies to this thread... A REAL hefty fella, a marginal shock, bumpy or uneven roads on a daily basis, and a maybe under inflated tire could all add up to cupping. Little bit of each make a full basket!

Now if you Don't want to attempt no hands I might suggest a different "type" of tire. City Grips are a mid line average Joe type tire. Maybe a Michelin Pure Power or a Pirelli SL 36. These are both very low profile, and have much less sidewall deflection.

[Vivo]

That's what I meant... a center mono shock... just like on sport bikes...  I changed to a wider and lower tire.. maybe the reason I don't have cups...

[zombie]

I went to wider taller... Maybe the reason I did have cups?

In any event it is NOT normal wear no matter what the guy on the internet says. Unusual wear always equals unusual suspension/alignment issues.

[naughty lee]

I've got four bikes, I've been riding longer than most of you on here have been alive.
All front tyres do that, more so the faster you take corners.

Take a look at your rear tyres, they should look like the edge of a coke can.. Round.
If they are going square across the profile, your doing too many miles in a straight line.. Buy a Harley!

Alternatively, fit a new tyre and seek out nice bendy roads to rip around on !

[kneeslider]

Or simple to check your alignment, try the string test.