Cornering Scare

[MattiGuzzi]

I have a2003 V11 Sport with custom bikini fairing. About two weeks ago I went out for a ride and took a left hand curve at a reasonable speed (nothing dramatic) but I experienced something like the rear end wanting to continue to drive the bike down to the left. I immediately cut the throttle and regained control. The bike stood up and I stopped. It was very unnerving. If it had happened under aggressive cornering, I would have crashed. I safety checked the bike (steering damper, loose bolts etc. Everything checks. I went back over the spot and it was clear of hazards. I have recently experienced a little extra play in the clutch and slippage (again, nothing dramatic) when accelerating hard. Any thoughts would be appreciated. 

[4corsa]

Possibly your rear brake caliper not releasing promptly after applying before the turn. I just rebuilt mine for a similar issue.

[guzziart]

1 hour ago, 4corsa said:

Possibly your rear brake caliper not releasing promptly after applying before the turn. I just rebuilt mine for a similar issue.

Hey 4corsa...

Any idea why the caliper was hanging up?  slid pin froze? Piston stuck? Is the piston metal? Does the caliper piston have a dust boot? Corrosion in side caliper bore?  Other...master cylinder piston not fully retracting/restricted port?

I really don't know too much about the brakes on my Lemans but was wondering about what you found.  Nor do I have any brake problems...yet.  I'm hoping routine fluid changes will keep me out of trouble.

Thanks,

Art

[Chuck]

When I saved Rosie the Rosso, the rear brake disc was blue and sounded like a gun went off when I removed it. Need I say it had been dragging a bit? My guess is the brake line was routed incorrectly too near the exhaust and the heat pressurized the line. That is only a guess, of course. A new rotor, caliper rebuild, and rerouted brake line fixed it at any rate.

[footgoose]

It's a little late in the season for wooly worms but I hit one with my front tire in a similar turn and it brought me down immediately. Like hitting a teaspoon of grease just right.

[LowRyter]

What do your tires look like?  What's the air pressure.  I rode a Griso that wouldn't turn, then fell quickly and then wouldn't turn all at the same curve.....Bad tires.

[docc]

Glad you regained control, @MattiGuzzi !

Good advice, already (rear brake, tire condition, road hazard).

It also occurs to me to suggest inspecting the lower shock eye. They are prone to breaking on the Sachs shock, and that the swingarm pivot bolt can get corroded and seize.

Also, to remove the rear wheel and inspect the wheel bearings. Failed rear wheel bearings can cause unexpected/unwanted shifts in the wheel position.

[PJPR01]

Tire pressures?  Cold tires due to temps dropping?

[MattiGuzzi]

4 hours ago, LowRyter said:

What do your tires look like?  What's the air pressure.  I rode a Griso that wouldn't turn, then fell quickly and then wouldn't turn all at the same curve.....Bad tires.

I'm and idiot! I was confident the tires and air pressure are good because, "I know what low tire pressure feels like!" No. The pressure was down front and back. Probably due to the drop in temps and having not ridden the bike since warm weather. I'm an idiot for having not checked it at the nearest station! Hopefully I'll get another chance to test before snow!

[4corsa]

5 hours ago, guzziart said:

Hey 4corsa...

Any idea why the caliper was hanging up?  slid pin froze? Piston stuck? Is the piston metal? Does the caliper piston have a dust boot? Corrosion in side caliper bore?  Other...master cylinder piston not fully retracting/restricted port?

I really don't know too much about the brakes on my Lemans but was wondering about what you found.  Nor do I have any brake problems...yet.  I'm hoping routine fluid changes will keep me out of trouble.

Thanks,

Art

Hey Art,

I'm not 100% sure what was causing the rear caliper to hang up, but my suspicion is the corrosion on the slide pin. I never fully understood how the hanging pads are expected to retract freely on anything but a brand new pin.  I cleaned it up well with steel wool and WD-40, but i probably should replace it.  

The pistons and seals all looked quite good - there is no dust boot.  I bought a seal kit and replaced them.  The pistons are aluminum cups and had no corrosion or pitting.  I did gently run some fine steel wool on them just to make myself feel useful.  I haven't ridden it yet as it has been too cold.  I need to pump some new fluid through first.  I'll report back if any issues. 

[docc]

Good to service our brakes, polish those pad pins!

No petroleum products around the brakes! Silicone greases, only!

[guzziart]

11 hours ago, 4corsa said:

Hey Art,

I'm not 100% sure what was causing the rear caliper to hang up, but my suspicion is the corrosion on the slide pin. I never fully understood how the hanging pads are expected to retract freely on anything but a brand new pin.  I cleaned it up well with steel wool and WD-40, but i probably should replace it.  

The pistons and seals all looked quite good - there is no dust boot.  I bought a seal kit and replaced them.  The pistons are aluminum cups and had no corrosion or pitting.  I did gently run some fine steel wool on them just to make myself feel useful.  I haven't ridden it yet as it has been too cold.  I need to pump some new fluid through first.  I'll report back if any issues. 

Hi 4Corsa,

Thanks for sharing your conclusions, corrective action & pics, perfect!  

Art

[LowRyter]

Yeah, tires are the first thing to look for.  My EV loses all the air in the front, so I have to air it up everytime I ride it.  I'm considering to sell the EV.  I'd like to keep the Greenie.  That one needs a good going over, new tires, brake pads, new plunger for the clutch engagement, lube job, tune up and oil change.  Someone reported on WG that the cheap sparkplugs are no longer available on these bikes, don't know.

Anyway, a good once over of the basics like tire wear and pressure, chain adjustment  are a good practice periodically or sometimes before every ride-  particularly if the bike hasn't been ridden in the last three or four days.  I find it best to clean the bike top to bottom and inspect everything.  Even the least mechanically inclined person as myself will find something to clean or tighten up. 

[MattiGuzzi]

1 hour ago, LowRyter said:

Yeah, tires are the first thing to look for.  My EV loses all the air in the front, so I have to air it up everytime I ride it.  I'm considering to sell the EV.  I'd like to keep the Greenie.  That one needs a good going over, new tires, brake pads, new plunger for the clutch engagement, lube job, tune up and oil change.  Someone reported on WG that the cheap sparkplugs are no longer available on these bikes, don't know.

Anyway, a good once over of the basics like tire wear and pressure, chain adjustment  are a good practice periodically or sometimes before every ride-  particularly if the bike hasn't been ridden in the last three or four days.  I find it best to clean the bike top to bottom and inspect everything.  Even the least mechanically inclined person as myself will find something to clean or tighten up. 

The funny thing is, I have an air compressor right next to my bikes. I check my V85TT every few days because I know it looses air very slowly. I had ridden the V11 for many many months and just stopped checking it because it was good. My stupidity for not being thorough and growing complacent. 

[stewgnu]

V11 handles bloody awful on low pressure tyres.  I cooked a rear disc once on the run up to and wa-hayy around the Scottish rally, which i think was just a badly maintained caliper- clean that bugger once a year!