Re: clutch housing and pressure plate

[Tpcutter@xxxxxxx]

In a message dated 2/14/06 11:49:06 AM Eastern  Standard Time, 
allen@xxxxxxxxxxxx writes:
As I see it, it's a matter of the  relative cost of parts vs. labor  
and downtime:
if it's your labor,  and you enjoy it, and you're ready to get less  
life out of your second  friction disk than the first, and if you  
don't mind your bike being  cold and in pieces for a few days now and  
then, and if the pressure  plate and inner plate aren't worn out of  
spec, then leave these parts  for a second go and replace them when  
they're worn out of spec.   I've heard of a rare spring failure, but  
I've never heard of an abrupt  clutch failure due to the plates giving  
up.?>>

My  question is simple and to the point: How many BMW clutches have you 
installed?  How many started slipping shortly after you installed a new friction 
plate with  all the other old parts? For me the answers are 1) Over a hundred, 
probably  closer to five hundred, and 2) Almost every one. Now I absolutely 
refuse to just  replace the friction plate even if the customer demands it. I 
would sooner  return the bike in disassembled state.

In short, you don't know what you  are talking about. Clutch springs do not 
break, at least not on BMWs. They lose  tension from heat and from being 
constantly under compression.

The mating  plates, inner and outer, develop a conical form when worn, that 
does not match  the shape of the new friction plate. The resulting combination 
gives about 15%  contact area, not enough to contain the torque of any R1100 
or 1150 engine.  

It is not about measurable wear. It is about loss of contour. New parts  are 
all flat, and will all wear TOGETHER. They start with good (like 80% or  
better) contact, and rapidly bed in to give almost 100% contact. If kept in  proper 
adjustment, and the cable and operating mechanisms are lubricated  
periodically to prevent clutch drag, Oilhead clutches can EASILY last 200,000  miles.

Tom Cutter
Yardley,  PA
http://www.RubberChickenRacingGarage.com  

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