RE: [ST] Dreaded cupping

["Heyer, Matthew A." <mheyer@xxxxxxxxx>]

OK - I'll chime in here.  An excerpt:

"Cupping, which is more accurately described as scalloping, 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 scalloping takes place within the
side wear bands of a leaned motorcycle as discussed earlier. 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 on a scalloped
tire. 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 scalloping follows the tread pattern. The
leading edge of the tread 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 and the tire
flexes there which causes less scuffing so less material is ground off
the tire. The more complex the tread pattern, the more complex the
scalloping pattern will be. The softer the compound of the tire, the
sooner this scalloping will become evident. Radial tires are more prone
to cupping than are bias ply because the compound of radials is more
often softer. As one can see, the simple tread pattern of the Avon
pictured produces a simpler scalloped pattern while the more complex VTX
D256 Dunlop is somewhat more involved, though still fairly easily seen
in our photo. Scalloping on the Valkyrie Dunlop D206 is very hard to
photograph because of the complex tread pattern. Improper balance has
nothing to do with "cupping" on a motorcycle tire. Improper balance will
merely cause your bike to vibrate within certain and specific speed
ranges. Low tire pressure will exacerbate this wear pattern and you will
lose many serviceable miles by running low."


Matt Heyer


- -----Original Message-----
From: owner-st@xxxxxxxxxx [mailto:owner-st@xxxxxxxxxx] On Behalf Of Rick
& Joyce
Sent: Thursday, October 14, 2004 10:40 AM
To: ST@xxxxxxxxxxxxxx
Subject: RE: [ST] Dreaded cupping

Neil wrote:
> I'd also suggest that the cupping of the front tire tread is 
> symptomatic of relatively heavy use of the front brake, 
> notwithstanding the fact that Bridgestone tires seem to be 
> particularly susceptible to this phenomenon.

Gotta jump in here.  As a subscriber to the "Pace" school of riding, I'm
not a heavy braker.  My OE front pads lasted almost 34k miles and would
have gone much farther had a rock not become wedged behind one of the
pads.  I've understood that cupping can be attributed to HOW you use the
brake and the throttle while in the turning mode.  My sense is those of
us who trail brake or use a large measure of throttle while exiting
turns can expect to see more cupping.  

That said, I agree that the brand of tire is a factor.  Every
Bridgestone front tire I've run on a modern motorcycle has cupped, some
rather badly.

Rick in Oregon
'01 Sprint ST


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