cjboden
12-16-2007, 02:10 AM
Working after the successful front fork spring upgrade to the (lowered) Hyperpro's, we moved on to the rear mono-shock.
Interesting mounting and removal process. First, jacking up the rear of the bike with the front in a chock requires the rear tire off the ground by straps to the rear rack area and not anything from below that involves the swingarm. Easy enough. Removed the seat and the two side skirts for better top access, as well as the small assembly that holds the gas vapor canister. This can be just tilted to the right side to be out of the way, without removing all the hoses.
Removal of the shock bolts is very easy. BUT: there is not enough room to remove the shock without the gas tank getting in the way. Removed the upper shock adjustment knob (only the knob) and still not enough clearance. There are then 4 bolts that hold the entire rear frame member to the front frame. Removing these allows the entire rear frame with gas tank in place to slide backwards GENTLY. This allows enough clearance for the shock to be maneuvered out.
Now the real job starts! These shocks are very high pressure and the stock spring is very competent on the bench, even if less so on the bike. In any event, our desire was to replace the coil over spring with the matched Hyperpro lowered unit. If not for this, I would NOT touch the rear at all unless replacing with an Ohlins unit with remote reservoir,etc. as a real upgrade. The BMW shock is a Showa B042, with standard mounting loop on the top for through bolt, but the bottom is BMW specific with a block of aluminum and the rebound adjuster knob in that. This lower "block" has the typical overspring washer and clip plates in place, and seems the logical place to compress the spring, remove the circlips and take the spring off. BUT the aluminum mounting block stops this from happening and the removal of the spring is on the PRELOAD adjustment side and is much harder to mount for spring compression and HIDDEN clip removal. The chance of damage to the shock top, even if just marring is very high! On the HyperPro instructions this is shock type 3: Hydraulic adjustable preload shock. Unless you are a dedicated do it yourselfer and have at minimum an hydraulic press, this is the time to take the shock and the new spring into the shop to let them at it. Single spring dismount and mount is inexpensive and you have at least saved yourself all the cost of the bike disassembly and assembly. Most auto shops that deal with coilover shocks have spring compression rigs to handle these shocks and there is no need to go to the bike shop for hourly rate.
Andrew and I will report the measurement changes with the lowered Hyperpro set up once we recover from this job!
Interesting mounting and removal process. First, jacking up the rear of the bike with the front in a chock requires the rear tire off the ground by straps to the rear rack area and not anything from below that involves the swingarm. Easy enough. Removed the seat and the two side skirts for better top access, as well as the small assembly that holds the gas vapor canister. This can be just tilted to the right side to be out of the way, without removing all the hoses.
Removal of the shock bolts is very easy. BUT: there is not enough room to remove the shock without the gas tank getting in the way. Removed the upper shock adjustment knob (only the knob) and still not enough clearance. There are then 4 bolts that hold the entire rear frame member to the front frame. Removing these allows the entire rear frame with gas tank in place to slide backwards GENTLY. This allows enough clearance for the shock to be maneuvered out.
Now the real job starts! These shocks are very high pressure and the stock spring is very competent on the bench, even if less so on the bike. In any event, our desire was to replace the coil over spring with the matched Hyperpro lowered unit. If not for this, I would NOT touch the rear at all unless replacing with an Ohlins unit with remote reservoir,etc. as a real upgrade. The BMW shock is a Showa B042, with standard mounting loop on the top for through bolt, but the bottom is BMW specific with a block of aluminum and the rebound adjuster knob in that. This lower "block" has the typical overspring washer and clip plates in place, and seems the logical place to compress the spring, remove the circlips and take the spring off. BUT the aluminum mounting block stops this from happening and the removal of the spring is on the PRELOAD adjustment side and is much harder to mount for spring compression and HIDDEN clip removal. The chance of damage to the shock top, even if just marring is very high! On the HyperPro instructions this is shock type 3: Hydraulic adjustable preload shock. Unless you are a dedicated do it yourselfer and have at minimum an hydraulic press, this is the time to take the shock and the new spring into the shop to let them at it. Single spring dismount and mount is inexpensive and you have at least saved yourself all the cost of the bike disassembly and assembly. Most auto shops that deal with coilover shocks have spring compression rigs to handle these shocks and there is no need to go to the bike shop for hourly rate.
Andrew and I will report the measurement changes with the lowered Hyperpro set up once we recover from this job!