Cupped Tires...

[jeff355]

Hi guys, just a quick question/observation. What causes a front tire to "cup". Ive read here that it seems to be an issue on the Busa. Mine is showing it too. Now when I was out last week on a ride with about a dozen other bikes, Id bet 6 or 7 outta 12 had the same issue. I find that overwhelming. So if its an issue on many motorcycles overall, how can you prevent it ? I always check tire pressure a couple times a week. Is it a "local" thing because of the road crown in my area? The bikes in our group that werent showing yet were on new to almost new rubber. I run a shinko raven and its only a season old and shot. Lotsa tread left, but showing signs of cupping.

Any help/insight would be great. Thanx, Jeff.

 

[twotonevert]

Not sure on the Shinko's, but I had a BT-21 do the same thing to me, not even a 1000 miles and the front was shot. I switched tire brands and have not had this happen again yet. That was about 7k miles ago. I too always check pressures and I was dead on. There will be others that will chime in soon.

 

[BusaWhipped]

Incorrect tire press is a major contributor. A lot of sport bike riders run lower tire pressures for better grip. Incorrect suspension setup is another factor. Sometimes you just get a bad tire.

 

[trekfuel]

Incorrect tire press is a major contributor. A lot of sport bike riders run lower tire pressures for better grip. Incorrect suspension setup is another factor. Sometimes you just get a bad tire.

+ on tire pressure... what pressure are you running....

Lower pressure.... higher temps.

Follow pressure recommendations shown on the Dunlop Motorcycle Tire Application Guide. Contact Dunlop if year and model are not shown on the current guide and the owner's manual does not list pressure settings for Dunlop tires.

Keep in mind that hard cornering, passengers, heavy loads and sustained high speeds will require higher pressures (up to that indicated on the sidewall).

CHECKING TIRE PRESSURES IS THE MOST IMPORTANT TIRE MAINTENANCE FUNCTION YOU CAN PERFORM.

For high-speed, fully loaded or dual-riding touring motorcycle applications, inflate front tires to maximum recommended by vehicle manufacturer for Dunlop fitment and rear tires to maximum load inflation pressure on sidewall. Rear touring tires must be inflated to a minimum of 36 psi for light to medium loads and 40 psi for dual riding and other loads. Never exceed maximum load indicated on tire sidewall or vehicle capacity load found in owner's manual.

Underinflated tires can result in imprecise cornering, higher running temperatures, irregular tread wear at the edge of the contact patch, fatigue cracking, overstressing and eventual failure of the tire carcass.

Overinflating tires does not increase load carrying capacity, but will result in a hard ride and accelerated tire wear in the center of the contact patch.

Check cold tire pressure frequently with a good quality gauge that holds a reading, and always before extended trips.

Loss of pressure may occur due to worn out or badly seated valve cores. Check valve cores. If necessary, tighten for correct seating, or remove and replace them. A metal or hard plastic valve cap with an inner gasket should be used and installed finger tight to protect the valve core from dust, moisture and to help maintain a positive air seal.

Repeated loss of inflation pressure may result from undetected tire damage. Visually inspect tires for punctures, cuts, abrasions, cracks, bulges, blisters or knots. It will be necessary to dismount the tire to complete an inspection for internal damage and any need for repair. See the Tire Repair section. Only certain punctures in the tread area may be repaired, and only if no other damage is present.

Tires with non-repairable damage must not be used again. Damage caused by impacts, penetrations or continued underinflated/overloaded use is progressive and can result in sudden and complete tire failure and accident.

Always seek expert inspection of the dismounted tire following curb, chuckhole or other impacts, evidence of penetration beyond the tire surface, bulges or low pressure. Do not continue riding on such tires.

Inspect your tires frequently for damage and always heed warning signs such as vibration, handling instability, rubbing or tire noise that occurs during operation of the motorcycle

taken from Dunlops site

 

[RMS2005]

same here, always been told it was due to low pressure.

 

[jeff355]

I always run them at the max 42. If underinflations the only cause, then my tire must be defective from the get go, because its always at the 42.

 

[sixpack577]

The individual tire can have a little to do with it, sometimes you can get one that doesn't wear as well.
Over inflation, improper balance, bad suspension setup, tire compounds, riding style(Little lean angle, straightline riding)all can be factored in. All these things can make a tire more prone to cup.

 

[kml]

What follows in bold (and you would be well advised to click the link and read the whole page) is a cut and paste from;

Motorcycle Tire Wear

CUPPING:
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.

The following textual illustration comes from Martin who contributed to this article by E-mail on June 26, 2006:
I was just reading your bit on "cupping" and thought I'd share with you how I describe what's going on. I usually tell people that what's happening is that the individual "blocks" or "islands" of tread are squirming and deforming due to the forces applied to them during cornering and braking. When this deforming takes place, the wear is naturally not evenly distributed across the surface of the tread. (I define a tread block as an area of the tire surface surrounded by a groove.) I next tell people they can demonstrate to themselves what's happening by taking a new pencil with an unused eraser on the end and while holding the pencil perfectly vertical, push down and drag the eraser on a rough surface in one direction. Then I tell them to look at the eraser and note that all the wear is on the leading edge and not evenly distributed across the end surface of the eraser. It seems to make the concept easier for many to understand. Cheers!

There is your explanation.

cheers
ken

 

[jeff355]

Now that was a great answer ! Thanx.

 

[sportcustoms71]

thanks for that explanation KML

 

[dmallord]

+1 kml