Annual service for 1100S

[Snips]

Just back from have having bike serviced at St Neots Motorcycles.

Firstly they are a great bunch of guys, and very highly recommended.

They noticed a front brake inconsistency at low speed - not warped discs, but variable friction from the material. They are going to get them (and pads) swapped.

I also had a 14T sprocket fitted. I was keeping my expectations in check, not expecting it to make much difference, but wow, it makes a really big (and positive) difference.

It's now much more smooth at 30 mph, and I get to use 6th gear comfortably at 70mph and upwards.

A highly recommended mod.

[walpole68]

When mine had first service done i went up 2 on the rear and very impressed with gears 2-6 but first is useless unless you want to flip it.

[Nickj]

They noticed a front brake inconsistency at low speed - not warped discs, but variable friction from the material. They are going to get them (and pads) swapped.

Presuming that the hub and wheel flange are flat and in good condition {not an old bike so no reason not to be} and that the disk bolts have been installed correctly and tightened uniformly and in the correct order to the recommended torque specification {which is very hard to get wrong} (takes a big breath) then it's going to be caused by friction pad material transferred unevenly to the surface of the disc. This results in thickness variation or run-out due to hot spotting that has occurred at high temperatures.
Now here's where it gets techie!!
Cast iron is an alloy of iron and silicon in solution interspersed with particles of carbon. When it gets hot or bloody hot to use the technical terminology things change in the composition of the disk.
You get what are called inclusions of carbides forming in the iron matrix. So on the rotor itself you have areas that are standing slighlty proud of the disks surface, any uneven deposits like this become hotter than the surrounding metal. Every time that the leading edge of one of the deposits contacts with the pad, the local temperature increases. When this local temperature reaches around 650C the cast iron under the deposit begins to transform into cementite {no nothing to do with blue circle cement, it's an iron carbide where three atoms of iron combine with one atom of carbon). This stuff is very hard, very abrasive and is a poor heat sink. The more you use the brakes the more cementite forms and it just gets worse and juddery without any measurable distortion of the disk.
So in conclusion~
So it's really all down to bedding in pads properly at the outset, Hot enough to burn out the solvents in the pad itself but not so hot you develop any uneven deposits on the disk rotor. The run in for pads not only beds in the pads but surfaces the rotor {the rotor surfacing part is the important part}.
Ten increasingly hard stops from 60 - 80mph to 5 mph with normal acceleration back up to speed in between should do the biz, no more than about .7g, ABS usually kicks in at about .9g if you have such extras.
If you look closely at the leading edge of the pads (certainly on organics) they may have a very thin grey band. This is good, it's the colouring and resins in the pad material burning off and idicating you're at the right kind of temperatures.

Of course if you really nail the pads hard from fresh you get this uneven surfacing on the rotor and the feeling that the disks are warped. Sometimes it's just a poor mix of iron but thats really very rare and the rotor itself will tend to warp.

There ya go don't you feel so much better you know this ?? :freak:

[Gordon H]

Wow.........