XM-2000 front brake adjustment - mine squeaks, gets hot and eats range

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greatguru
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XM-2000 front brake adjustment - mine squeaks, gets hot and eats range

Can anyone tell me how to adjust the XM-2000's front brake? It's squeaking and getting hot lately. Also, coincidentally, range is decreasing.

Thanks!
Markus

reikiman
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Re: XM-2000 front brake adjustment - mine squeaks, gets hot ...

It's disk brakes? Likely the pads are rubbing too tightly.

jdh2550_1
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Re: XM-2000 front brake adjustment - mine squeaks, gets hot ...

The pads are probably sticking and the return spring isn't strong enough to return them to the open position. I don't have the brake assembly in front of me so I can't tell you how to address it off the top of my head. I can look later and send you the info - or you can google for an answer.

John H. Founder of Current Motor Company - opinions on this site belong to me; not to my employer
Remember: " 'lectric for local. diesel for distance" - JTH, Amp Bros || "No Gas.

sgmdudley
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Re: XM-2000 front brake adjustment - mine squeaks, gets hot ...

There are no return springs in disk brakes. There is always pressure of the pads
against the rotor. However, it should not be a lot. Should not cause heating or
put so much pressure on the rotor that the wheel does not rotate smoothly with
just a little drag. I have worked on several scooters for this same problem
and have not really found a good solution.

The main thing I do is disassemble the wheel and caliper. make sure the caliper
pins are lubed to allow the floating part of the caliper to freely move. This
was designed to allow for wear of the pads. Sometimes, if dry, the assembly will
not float so will bind putting too much pressure on the rotor.

Also make sure pads are clean and have not picked up any dirt or grease on the surface.
This results in binding of the rotor.

Make sure that when you tighten the caliper mounting bolts that they don't cause the
assembly to tweak out of alignment with the rotor.

Robert Dudley
E-Scoot Tech

greatguru
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Re: XM-2000 front brake adjustment - mine squeaks, gets hot ...

Thanks for the input. I got to look at the caliper only today - finally got to buy a large wrench that was able to tackle the supertight hex bolts.

The caliper is fluid operated and has two pistons that push the brake pads against the disk. As you already guessed, after operating the brake handle, the pistons don't return into their start position, and keep pushing against the brake pads. In fact, the more often I pull the brake, the tighter the pistons grab the pads, and never let go, as if fluid pressure builds up more and more. Even if I wait a while, they don't let go and stay stuck with mighty force, and only with significant effort, forcefully prying the pads apart with a large screwdriver, can they be pushed back into their start position. While doing this there is a viscous feel to it, as if I am pushing the fluid back through the brake cables into the top reservoir.

Lubricating the pistons does not help, they still get stuck just the same.

The brake handle moves easily back and forth, and smoothly operates a small piston attached to the handlebar reservoir. That piston moves in and back out just fine as expected. Only the caliper pistons get stuck.

What do you guys think? Should I open the caliper up and check inside? How do I do that without spilling the fluid? Or could the problem be in the handlebar reservoir?

Thanks for any input!

Markus

XM-2000, Voloci, custom electric bicycle
[url=http://www.wikipik.org/vc16]WikiPik[/url]

sgmdudley
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Re: XM-2000 front brake adjustment - mine squeaks, gets hot ...

I have a Zapino so do not know if the brakes are the same manufacturer.
All the fluid leaked out of my front brake so I will be disassembling
the caliper to investigate. I suspect in your case there is a valve that
should allow fluid pressure to back off when you release the brake lever.
This would back off the pressure of the pistons against the outer pad.
Seems that a complete disassembly would be in required to inspect all
the parts. Could be some debris was allowed into the system during manufacture.
It is a closed system, unless you take off the Master cap to add fluid.

Robert Dudley
E-Scoot Tech

greatguru
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Re: XM-2000 front brake adjustment - mine squeaks, gets hot ...

Thanks for the info, Robert! Yikes, opening up that system sounds like a mess. When will you open yours? What fluid would I use to replace leakage? Are you aware of any maintenance guide describing the brake system? Sounds scary to mess with a vital system like the front brake...

Thanks!
Markus

XM-2000, Voloci, custom electric bicycle
[url=http://www.wikipik.org/vc16]WikiPik[/url]

sgmdudley
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Re: XM-2000 front brake adjustment - mine squeaks, gets hot ...

Hydraulic brakes are all the same. You have a closed system except at the Master cylinder where
the cap is to add regular brake fluid. When done, it does require bleeding the air out of the system.
The master cylinder is on the handlebars, the slave is the caliper. Yes, it is messy. If you decide
to take it apart, the best cleaning solution to use is brake fluid. Flush the master, the hose and
the caliper. Reassemble and add fluid. Some folks use a pressure device to add fluid from the bottom
and it pushes air out the master. The other way is fill the master, pump the brake lever, open the
bleed fitting at the caliper and shut it quickly. Do this until nothing but fluid comes out. Brake
fluid comes is several DOT versions and regular fluid or synthetic fluid. We don't know what China
is using. I plan on flushing everything with DOT 4 or 5 and then filling with same.
My scooter repair is planned for Thursday. I will be taking pictures.

Robert Dudley
E-Scoot Tech

greatguru
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Re: XM-2000 front brake adjustment - mine squeaks, gets hot ...

My master reservoir says embossed on it:

"WARNING. CLEAN FILLER CAP BEFORE REMOVING USE ONLY DOT4 BRAKE FLUID FROM A SEALED CONTAINER"

What does this mean?

Thanks so much and looking forward to your report on your brake repair!

Markus

XM-2000, Voloci, custom electric bicycle
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sgmdudley
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Re: XM-2000 front brake adjustment - mine squeaks, gets hot ...

There are two kinds of brake fluid. Mineral based and Synthetic. There are various DOT ratings.
I am not an expert on the differences. I just use what the manufacturer recommends. For some
types of rubber products in the brake system, you cannot upgrade from mineral to synthetic. The
rubber would be damaged. So anyone thinking it would be great to go synthetic, just check with
the manufacturer first.

Regular Brake fluid (not synthetic) starts absorbing moisture as soon as you open the container.
Therefore to minimize moisture in the brake system which leads to rust, they recommend you get a
brand new can or bottle and only when you are ready to take the cap off the master cylinder,
open the container to add the fluid. Of course this means that once opened, you are not supposed
to put the cap back on the can/bottle and save it to use weeks, months, years later.
This is for the mineral based brake fluid.

Robert Dudley
E-Scoot Tech

pchilds
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Re: XM-2000 front brake adjustment - mine squeaks, gets hot ...

I think you have confused synthetic with silicone brake fluid. I use Valvoline synthetic brake fluid in all my vehicles. Most brake fluid is glycol not mineral oil based. For more information about brake fluid check out the link below.

http://www.motorcycleproject.com/motorcycle/text/cows-brakefluid.html

Philip

Philip
2011 Nissan Leaf SL

sgmdudley
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Re: XM-2000 front brake adjustment - mine squeaks, gets hot ...

That is a very good article on Brake Fluids. Yes, Silicone is what I referred to as Synthetic.
Glycol is what I refrred to as Mineral Based.
Here is something from Wikipedia:

Mineral-based
Alkyl ester
Aliphatic amine
Diethylene glycol
Diethylene glycol monoethyl ether
Diethylene glycol monomethyl ether
Dimethyl dipropylene glycol
Polyethylene glycol monobutyl ether
Polyethylene glycol monomethyl ether
Polyethylene oxide
Triethylene glycol monobutyl ether
Triethylene glycol monoethyl ether
Triethylene glycol monomethyl ether

[edit] Silicone-based
Di-2-ethylhexyl sebacate
Dimethyl polysiloxane
Tributyl phosphate

Robert Dudley
E-Scoot Tech

sgmdudley
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Re: XM-2000 front brake adjustment - mine squeaks, gets hot ...

Took my brakes apart at the wheel. Some pictures here: 1st two from a spare brake asm.
Master Cylinder on the handlebar
Zap_Frt_Brk_Master.jpg
Caliper Assembly (electrical tape is holding a spacer between the brake pads).
Zap_Frt_Brk_Caliper.jpg
Here is the Leaking Caliper. Leakage seems to be from the seals, there are two for each piston.
Caliper__disassemble.jpg

Robert Dudley
E-Scoot Tech

greatguru
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Re: XM-2000 front brake adjustment - mine squeaks, gets hot ...

Thanks for the pics! That looks pretty much identical to my XM-2000's brake assembly, except for that T-piece adaptor between the caliper and the hose, my XM-2000 doesn't have that. I wonder what the purpose is of that thing and if the reason for its existence has anything to do with the problem I am having.

XM-2000, Voloci, custom electric bicycle
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greatguru
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Re: XM-2000 front brake adjustment - mine squeaks, gets hot ...

So did you get yours fixed? What brake fluid did you end up using?

XM-2000, Voloci, custom electric bicycle
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garygid
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Re: XM-2000 front brake adjustment - mine squeaks, gets hot ...

Normally, disk brake pads should not touch the disk when not being used.

When properly designed and built, and operating properly, the piston has a special flexible gasket around it that keeps the brake fluid from coming out. The outer surface of this gasket resists going out, and the cross section of the gasket deforms (stretches) slightly as the inner surface of the gasket is carried toward the disk by the piston.
As the hydraulic pressure behind the piston is reduced, the stretched gasket's cross section attempts to return to its un-distorted shape, pulling the piston back in just a little, which takes the brake pad off the disk.

As the pad wears, the "resting" position of the gasket will gradually move outward, automatically "adjusting" the disk brakes.

If the piston and cylinder are not perpendicular to the brake disk, or the pad wears into a wedge shape, or the pad is too thick, or the gasket and cylinder walls are not in good shape, this auto-adjusting might not happen properly, and the pads may drag, which is NOT good, desired, or normal, in spite of what a dealer or some service people will tell you.

Cheers, Gary
XM-5000Li, wired for cell voltage measuring and logging.

greatguru
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Re: XM-2000 front brake adjustment - mine squeaks, gets hot ...

Hey I just wanted to update everybody on this age old thread.

FYI, I got the problem fixed by taking the pads off the caliper, then pulling the pistons out, cleaning caliper and pistons well, putting them back in, and flushing the brake system multiple times (secret here is to not let air get into the system (dah) and holding the caliper in such a position that the fluid exits at the very top end of the caliper volume - otherwise pockets of air will remain in the caliper, preventing the brake from operating properly). I just bought off-the-shelf Valvoline DOT 3&4 brake fluid at the car parts dealer (a whole quart which I ended up needing as I flushed the system 10-15 times). Here's some images on how to do it:

This fixed the brake issue, however unfortunately it did not fix the range issue as this turned out to be not so much a brake problem but a battery capacity issue. As I do not have the time and energy to deal with the batteries right now, I decided to sell the bike. Farewell!

Hope this info helps those of you who are still riding XM-2000s and XM-3000s around.

XM-2000, Voloci, custom electric bicycle
[url=http://www.wikipik.org/vc16]WikiPik[/url]

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