Tire Cupping and another question

[C.V.]

-'79 850g

Having some minor handling anomalies, it feels a little wiggly when cornering, and occasionally kind of "wavy" (don't know exactly how to descibe it) on the straight. Are these symptoms of cupping on the front tire? What would I look for visually?

also, I think 110/90 19 is the right size (its whats on it now), but read somewhere here that it is not correct, and handling is vastly improved by using 100/90 19...
any input on this?

Thanks gang!

[bonanzadave]

Not sure about the tire sizes but with your issues its a good place to start. Check the tire air pressure. Look for uneven tread wear. Get the front wheel off the ground and spin it to see how true it runs. Check the wheel bearings and also the steering head bearings.

[Steve]

Tire ... go with the 100/90-19.

Handling ... check your wheel bearings, proper fluid levels in the forks, steering bearing tightness and swiingarm bearings.

Oh, the handling problems are not symptoms of the cupping, more likely, the cupping is a result of whatever is causing the handling problems.

.

[bonanzadave]

Oh, the handling problems are not symptoms of the cupping, more likely, the cupping is a result of whatever is causing the handling problems.

WORD ! I think my bad steering stem bearings F'ed up my front tire.

[waterman]

I will second the cupping probably isn't the cause but more of the symptom. My Klx with its knobby tires will cup the treads with no ill effect on handling or steering. Check your bearings as others stated. If those are okay, start looking critically at the front end components. I had driven a deer wrecked Cavalcade with bent forks that drove as you described. Not fun.

[Nessism]

What model of tire? Some brands/models are more prone than others. For example, I've heard about cupping on Bridgestone BT45 and S11 models. Both pretty good tires but sensitive in some ways.

[82Shafty]

http://www.rattlebars.com/valkfaq/tirewear/

Cupping, which is more accurately described as scalloping (see pictures, but we will use the more common term "cupping" here), is a natural wear pattern on motorcycle tires and it will always follow the tread pattern. It is not a sign that you have bad suspension parts. It merely shows that your tire is indeed gripping the road when you make turns (thank you for that Mr. Tire!). This cupping develops within the side wear bands of a leaned motorcycle. The extreme forces that come in to play when the bike is leaned in a turn are what produce the effect and when the wear becomes sufficient, one will experience vibration and noise when one banks into a turn. Upon examination of the pictures at left of our sample rear Avon, our dusted front VTX Dunlop D256, and the picture of our chalked Dunlop D206 one can see how the cupping follows the tread pattern. The leading edge of the tread does not flex much as it grips the road and the rubber is scuffed off the tire in that area causing a depression. As the tire rotates, the pressure moves to the trailing edge of the tread pattern where the tread flexes more causing less scuffing so less material is ground off the tire. The more complex the tread pattern, the more complex the cupping pattern will be. The softer the compound of the tire, the sooner this cupping will develop. Radial tires are more prone to cupping than are bias ply because the compound of radials is softer. As one can see, the simple tread pattern of the Avon pictured produces a simpler scallop pattern while the more complex VTX D256 Dunlop is somewhat involved, though still easily seen in our photo. Cupping on the Valkyrie Dunlop D206 is very hard to photograph because of the complex tread pattern. Low tire pressure will exacerbate this wear pattern and you will lose many serviceable miles by running low. Improper balance has nothing to do with cupping on a motorcycle tire. Improper balance will merely cause your bike to vibrate within certain specific speed ranges.


Get your front off of the ground and grab tire at 6 and 12 and see if there is any movement.

Stand infront of the bike, grab the forks at near to their lowest point by the axle and try pulling and pushing on them to see if your steering stem bearings are shot or if they need to readjusted. Usually given the age of most bikes, it is a good time to replace them.

My bike felt goofy when I first picked it up, I would change lanes and it would wander a bit or the same with cornering. My steering stem spanner needed to be adj.

[waterman]

Great info there, thanks 82Shafty. I couldn't figure why every set of tires I ran on the bike cupped. At the time, this bike was used primarily for commuting and a lot of stop and go traffic. It doesn't brake very well and I figured most of the cupping was from nearly locking wheel at every stop. It was strange in that I would wear out the front tire before the rear. Definitely made for some weird looking wear patterns.

[Mark whiz]

Braking wear does indeed show itself as "cupping" as well as the forces 82Shafty mentioned.

[mixongw]

http://www.rattlebars.com/valkfaq/tirewear/

Cupping, which is more accurately described as scalloping (see pictures, but we will use the more common term "cupping" here), is a natural wear pattern on motorcycle tires and it will always follow the tread pattern. It is not a sign that you have bad suspension parts. It merely shows that your tire is indeed gripping the road when you make turns (thank you for that Mr. Tire!). This cupping develops within the side wear bands of a leaned motorcycle. The extreme forces that come in to play when the bike is leaned in a turn are what produce the effect and when the wear becomes sufficient, one will experience vibration and noise when one banks into a turn. Upon examination of the pictures at left of our sample rear Avon, our dusted front VTX Dunlop D256, and the picture of our chalked Dunlop D206 one can see how the cupping follows the tread pattern. The leading edge of the tread does not flex much as it grips the road and the rubber is scuffed off the tire in that area causing a depression. As the tire rotates, the pressure moves to the trailing edge of the tread pattern where the tread flexes more causing less scuffing so less material is ground off the tire. The more complex the tread pattern, the more complex the cupping pattern will be. The softer the compound of the tire, the sooner this cupping will develop. Radial tires are more prone to cupping than are bias ply because the compound of radials is softer. As one can see, the simple tread pattern of the Avon pictured produces a simpler scallop pattern while the more complex VTX D256 Dunlop is somewhat involved, though still easily seen in our photo. Cupping on the Valkyrie Dunlop D206 is very hard to photograph because of the complex tread pattern. Low tire pressure will exacerbate this wear pattern and you will lose many serviceable miles by running low. Improper balance has nothing to do with cupping on a motorcycle tire. Improper balance will merely cause your bike to vibrate within certain specific speed ranges.


Get your front off of the ground and grab tire at 6 and 12 and see if there is any movement.

Stand infront of the bike, grab the forks at near to their lowest point by the axle and try pulling and pushing on them to see if your steering stem bearings are shot or if they need to readjusted. Usually given the age of most bikes, it is a good time to replace them.

My bike felt goofy when I first picked it up, I would change lanes and it would wander a bit or the same with cornering. My steering stem spanner needed to be adj.

When checking the stem bearings as described above, do I look for ANY movement as an indication the bearings are too loose?

[Jethro]

Keeping a close eye on tire pressures goes a long away against cupping tires, but it's a fact of life.

[SteveR]

I had a NEW BMW R1100RT 1995 and the front tire cupped about 3000 miles. I replaced it. It cupped. I ran the pressure very high and that slowed it down. Then I could get 4-5000 miles. Two other bikes just like this one were purchased new and they had the same problem. We never really fixed this issue.

[C.V.]

Thanks for the helpful responses

Thanks to all of you guys! The GSR comes to the rescue again-


82shafty- Thanks for the great info and pics, those are just what I need to see, and I indeed am suffering some pretty severe cupping on the Front tire. I will replace the tire, and at the same time check steering head and wheel bearings. I'll get back to you on the results.

Thanks again everyone for the help! The GSR rules!

[82Shafty]

I'm just happy to be able to help others.

[hp1000s]

I had a NEW BMW R1100RT 1995 and the front tire cupped about 3000 miles. I replaced it. It cupped. I ran the pressure very high and that slowed it down. Then I could get 4-5000 miles. Two other bikes just like this one were purchased new and they had the same problem. We never really fixed this issue.

My buddy has a K1200LT that cups the front tire @ around 5 - 6K miles depending on what brand/model he tries. Bob's BMW said (as did an article in one of the M/C mags) that heavier bikes are prone to do this.?