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@rosscooter avatar
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2014 GTV 300ie
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@rosscooter avatar
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The Problem: I went for an uneventful ride after the scoot having sat for over a month. When I returned and went to roll her under cover it was hard to do.I put the scooter up on the center stand and tried to turn the rear wheel by and and it was VERY stiff. The rear rotor was also very hot. I am thinking the brakes are somehow stuck but don't really know where to begin. Once everything cooled off and I worked the wheel around a little, it was looser but still stiff.

I have seen a couple of other threads on the rear wheel being very hard to turn by hand with a lot of references to the clutch or sticking brakes. How is this best diagnosed and repaired and can it be diagnosed and/or repaired without removing the rear wheel?

Edited to add: Could this be moisture in the brake fluid expanding and closing the calipers?

Thanks all.
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Hooked
2020 Vespa GTS Touring 300
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UTC quote
Re: GTV rear brake sticking?
rosscooter wrote:
I have seen a couple of other threads on the rear wheel being very hard to turn by hand with a lot of references to the clutch or sticking brakes.
Not on my newer scooter, the rear wheel will spin by hand with the engine off.
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How long since the last brake fluid change?
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2010 S50 Modified "Punkin"; 2003 ET4 Malossi 187 "ISO"
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Skidmarks
Greetings:

Hmm... Sure sounds like a sticking rear caliper. Brake fluid ever changed over 6 years? I have a friend who had this happen WHILE Riding his R-1200 BMW. On a Front caliper. Damn near dumped him on the highway as the front wheel came close to full lockup. He sold the bike shortly afterward. Unfortunately not to me... Crying or Very sad emoticon Address this without delay. The skidmarks may not be confined to the tarmac.
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2014 GTV 300ie
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Wheelman, Tor2ga: It has been 5K miles since the brake fluid was changed. That is number one on my to do list. I am hoping not to have to pull the rear wheel (exhaust, shock, etc.) in order to diagnose the problem and I certainly won't ride until it is resolved. do you think that the sticking calipers could be resolved with a fluid change?

bosco: Same with mine, until this issue.
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Greetings:
Quote:
do you think that the sticking calipers could be resolved with a fluid change?
No I don't. The caliper has to come off, dismantled, honed, and a rebuild kit installed. Tires and brakes are two areas where compromise is unwise.
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2016 Vespa GTS300ie abs/asr/ess Settantesimo '70'
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ross, all you need do it remove the brake pads and caliper. There is nothing to go honing. The caliper needs a good clean with brake clean, the pistons too. Usually this is quite easy if you are used to doing some spannering. Of course this will mean changing the brake fluid but do that after you have cleaned everything up. It's best to make sure you retain all the old fluid in the system until you clean everything up. You can do that by clamping the brake hose that feeds that caliper. If you don't do that it can be awkward to bleed the new fluid through from scratch. However, after you remove the brake pads you may want to carefully expose the pistons a bit by slightly applying pressure to the rear brake lever first so you can clean any muck off the pistons BEFORE you clamp the brake hose. Don't go grabbing a great big handful of lever though. You don't want the pistons and all the fluid to come rushing out. Work slowly. So, remove the pads and caliper, and clean everything up. It might just be the pads sticking on the guide pins as these corrode and get dirty. This stops the pads withdrawing away from the caliper. However, if the pistons are sticking too you'll need to clean those.

There's another thing too. It might just be the brake master cylinder has a blocked brake fluid return hole. This means that you pull the brake up and it remains in the on position. If the hole is not completely blocked it will very slowly release the pressure and the brake will return to normal. It then blocks again next time you pull the lever, and will do so until the vent hole is cleaned out. It is this that often causes wheels to lock up while riding.
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@kshansen avatar
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Stromrider wrote:
There's another thing too. It might just be the brake master cylinder has a blocked brake fluid return hole. This means that you pull the brake up and it remains in the on position. If the hole is not completely blocked it will very slowly release the pressure and the brake will return to normal. It then blocks again next time you pull the lever, and will do so until the vent hole is cleaned out. It is this that often causes wheels to lock up while riding.
This is one of the first things I would suspect! Another might be if the lever may have been changed and the new one was not made correctly to allow the piston in the master to come all the way back to expose the bleed hole in the master.

One easy way to tell if the bleed hole is the problem would be to try turning the wheel with it off the ground, if stiff or dragging crack open the bleeder on caliper if it then turns free then you know it's not the caliper.

Just remembered another possibility, bad hose from master to caliper acting as a check valve. In that case opening the bleeder at the caliper will release the brake but if you do the test again by opening the connection at the master it will not release the pressure.
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UTC quote
kshansen wrote:
Stromrider wrote:
There's another thing too. It might just be the brake master cylinder has a blocked brake fluid return hole. This means that you pull the brake up and it remains in the on position. If the hole is not completely blocked it will very slowly release the pressure and the brake will return to normal. It then blocks again next time you pull the lever, and will do so until the vent hole is cleaned out. It is this that often causes wheels to lock up while riding.
This is one of the first things I would suspect! Another might be if the lever may have been changed and the new one was not made correctly to allow the piston in the master to come all the way back to expose the bleed hole in the master.

One easy way to tell if the bleed hole is the problem would be to try turning the wheel with it off the ground, if stiff or dragging crack open the bleeder on caliper if it then turns free then you know it's not the caliper.

Just remembered another possibility, bad hose from master to caliper acting as a check valve. In that case opening the bleeder at the caliper will release the brake but if you do the test again by opening the connection at the master it will not release the pressure.
That would certainly make it easier than having to remove the exhaust, rear wheel, etc. I will give that. try first.
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UTC quote
Wheelman-111 wrote:
Greetings:
Quote:
do you think that the sticking calipers could be resolved with a fluid change?
No I don't. The caliper has to come off, dismantled, honed, and a rebuild kit installed. .
Are you aware that rebuild kits don't exist for these brake components?
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Flushed the system and bled the brakes. All is well. Thanks for the input.
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Question
Is that a single-piston (one-sided) caliper? If so, it needs to slide on pins to center the pads. If the caliper can't slide, the brake won't release.
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