KymcoForum.com
General => Technical | How To => Topic started by: Stig / Major Tom on April 06, 2014, 08:49:48 PM
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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:
(http://i59.tinypic.com/9a1tfr.jpg)
My rear Michelin (with plenty of tread)
(http://i59.tinypic.com/33kzk29.jpg)
(http://i57.tinypic.com/jv3rf7.jpg)
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I am assuming you corner aggressively or at high speeds.
It's normal.
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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)
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Good Stuff.
You can actually determine how the rider rides by checking out their tire wear/tire condition.
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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
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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
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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.
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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... :)
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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.
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Right Zombie... it's a scooter... ;D 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...
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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.
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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...
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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.
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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 !
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Or simple to check your alignment, try the string test.
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Or simple to check your alignment, try the string test.
I did and it's spot on.
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Or simple to check your alignment, try the string test.
That is where I said there is NO point of reference to judge by on these scoots. They may indeed be parallel (front to rear) but the square to ground may be off.
I'm not trying to be dramatic or anything.... Just stating what I have found on all these scooters.
Naughty Lee... I assume you meant the rear tire. That's where the OP's issue is. That's where my problems always are/ were as well.
Something else that comes to mind are the red or green dots they always place on a tire from the factory. Red dot means the heavy spot or side of the tire, and the dot should be installed opposite the valve stem, and a green dot is the lighter side that should mount on the valve stem side. Manufactures have not gotten together yet on this one, and most installers are unaware of the dots meanings. That makes balancing a "catch up" game instead of maybe not even being needed.
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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!
;D
Go easy on Mr. Stig, it's hard to drag pegs whislt eating donuts
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I think I'm going with the Trailing Edge of Certain Types of Tread Blocks Squirm theorum today.
Basically it means my City Grips are gripping as advertised.
Keeping bakers employed in the MidWest....Stig
(true confession: I do Tim Horton's more for the coffee than the do-wackers. Keep your old paper cups from Tim's, and the pasteboard tray. Put your new hot cup of joe in that stack of used cups - keeps it warm till you get out in the boonies on a frigid sunrise ride.)
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Drag slicks... End of thread! ;D
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Or just join the darkside.
(http://i58.tinypic.com/5wkzro.jpg)
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Or just join the darkside.
(http://i58.tinypic.com/5wkzro.jpg)
Don't tease me... I just might! I LOVE that style scoot. Here we go. Another 6G's on crappy ass scooters. Damn!
I just zoomed in. He has cupping too! WTF!!!
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Stig, I think what you are experiencing is "normal" wear for your type of riding. Below is a picture of a fairly new tire on a new to me bike, that had been ridden by an older gentleman who obviously took it easy in the turns. Carrying Tom Horton's coffee, I assume.
(http://i58.tinypic.com/24omwsn.jpg)
I've only put a few hundred miles on the bike and have yet to drag pegs, but am gunning to wear off the chicken strips soon. I am not sure if it's too late to save the tire from a Tim Horton's fate but I'm dam sure going to try.
(http://i60.tinypic.com/xppogl.jpg)
Regardless, if I see that XXXL helmet coming down the road, I'm gonna wave! Peace. ;D
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Not to appear disagreeable Cosmo but I don't see any sign of the "cupping" we are talking about. In fact I would say that is a perfectly worn tire.
Although I do agree it has been ridden at 90* to the road for most of its life, and you can tell he preferred left turns to right. ;D
Ps... That looks like a KendaTire
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Try this for sh**s, and giggles Stig... Try a known square straight edge across both sides of the rear tire that is long enough to reach across the entire front tire. Just like the string test but without any chance for deflection.
It may be best to have someone help to be sure there is no bias. Even a few thousandths of an inch is what I am talking about in my replies. I am VERY curious.
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Not to appear disagreeable Cosmo but I don't see any sign of the "cupping" we are talking about. In fact I would say that is a perfectly worn tire.
Although I do agree it has been ridden at 90* to the road for most of its life, and you can tell he preferred left turns to right. ;D
Ps... That looks like a KendaTire
Hmmm... what do I know.
Dunlop Elite 3.
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Hmmm... what do I know.
Dunlop Elite 3.
Just sayin' Go back to Stigs first post w/ the picts. you can see what appear to be 1/4" raises on most of the tread. It's as uneven as the grand canyon (almost).
I can't see that in your picts.
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Stig... loose some weight... end of thread..
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And Vivo gets yet another Kymco "I fixed it on line" T shirt. Employee of the month, every month, since the beginning of months.
Shenanigans!!!
South Park vs. They Live remix (http://www.youtube.com/watch?v=qhx8DMzYWIs#)
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Stig... loose some weight... end of thread..
Did my mother text you?!
(I went out and added 2psi to the rear tire. 2 over the spec now - but maybe it's all those tools, rollers, plugs, belts and bulbs I'm still carrying under the seat!)
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I have 35 psi in my rear tire...
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I have 35 psi in my rear tire...
40 rear, 33 front. The bike weighs 98 pounds wet. Aint you jealous!
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40 rear, 33 front. The bike weighs 98 pounds wet. Aint you jealous!
That would seem to equate to a total of 1 square inch of tire contact, each end.....and a ride like a bar of soap in the wet.
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NNNooooo!
Rolling Huge Tire Downhill Into Lake (http://www.youtube.com/watch?v=rxCv-ZvLZx4#ws)
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That would seem to equate to a total of 1 square inch of tire contact, each end.....and a ride like a bar of soap in the wet.
i dont think so... The tire would be "slicing" the water ... No hydroplaning.... And with a soft rubber compound.... Tire will stick to the road....
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Hi Stig.
My DT300 (2900 miles) has the standard Maxxis tyres and the rear tyre now has the exact same wear as evidenced in your photos.
The rear tyres on a number of my previous maxi scooters (different makes and engine sizes) went the same way.
Could be trait of CVT driven rear wheels.
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Hi Stig.
My DT300 (2900 miles) has the standard Maxxis tyres and the rear tyre now has the exact same wear as evidenced in your photos.
The rear tyres on a number of my previous maxi scooters (different makes and engine sizes) went the same way.
Could be trait of CVT driven rear wheels.
Thanks a lot Mitch for your reply.
This squares with what I have read elsewhere.
I like my Michelins ---- good ride in today's big downpour!
Stig
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All the effort that went into explaining why they cup, and the fellas come up w/ "it's a scooter thing"
I get it. I'm chopped liver riding a crooked stick with bars of soap for tires.
Too late now... My feelings have been CRUSHED! :'(
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When I was ten there was a "treaded slick" on the back of my Schwinn Stingray. I'll bet one of those whould solve all of Stig's problems.
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When I was ten there was a "treaded slick" on the back of my Schwinn Stingray. I'll bet one of those whould solve all of Stig's problems.
or a cup of coffee... ;D
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;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D 8)
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I've experienced the same sort of cupping on the OEM tires on my Yager GT 200i, almost all the way over to the edge (tiny chicken strips on my tires, if I lean any further, I scrape). I started seeing it at around 6500 miles, on both front and rear. More pronounced on the front.
When I'm leaned way in on a high speed turn (a 35 MPH curve taken at 70 MPH, for instance), I can feel the bike kind of "squirming" a bit, like the tires are slipping then catching. Pushing the inner handlebar outward (ie: taking a left-hand curve, steer right a very slight amount) and leaning outward a bit to compensate seems to smooth it out. So it's perhaps a result of being a bit too aggressive in the curves.
Strangely, I only notice it doing this on curves that are sloped (ie: the roadway is sloped toward the inner radius of the curve). Not sure why.