I am attempting to re-assemble a mountain bike for a friend that won it "pre-assembled" at a fundraiser auction. It is one of those nasty, cheap full suspension bikes. Michelob Ultra full suspension. These keep showing up on Craigslist as "1 of only 300 ever made" collectors bikes non-sense.

This one is brand new out of the box and slapped together for the auction block.

The issue is the disc brakes. They are labeled "YUS" and that is all.
These appear to be a Yusheng YDS-11 brake caliper.


The problem is, there are no assembly instructions for the bike and the caliper does not move when the lever on the caliper is moved. The lever moves freely but the piston does not even hint at compressing.

I am about to disassemble the caliper and was hoping maybe someone has looked at and has some clue about these calipers.

Attached is an example picture of the bike in question:
Michelob Ultra bike.jpg

Consider replacing them with Avid BB7 calipers?
which are supported with Downloadable manuals,
and are given positive revues as to function,
spare pad sources, and so forth..
Part of the SRAM brands .

I just assembled one of those awful things for a customer at the shop last week. I wouldn't use one of these for a lawn ornament, let alone try to ride it.

What I noticed about the calipers is that there are hex screws on the backside of the mounting bolts that move them closer or further away from the frame mounts. Try playing with them first. The brakes were actually easy to adjust, even with the out of round rotors. They work about as well as old steel side pull caliper brakes.

Sounds like you got a bad caliper though. Are both of them the same way or just one?

Thanks for the advise, kingsting.

These are just nasty, nasty calipers. They should be melted down to make something useful like weights for fishing line.

The set screws to position the caliper in line with the disk are unbelievably fiddly and probably won't be set correctly for more than a few hours of wear on the brake pads.

There is nothing that auto adjusts with wear on these calipers. I appears I will have to adjust the set screws on the caliper body to move it off center as the pads wear as the active "piston" only has one position, period. So, as the pads wear, the stationary pad will have to be adjusted closer to the disk and the caliper moved in the opposite direction to center the whole unit on the disc.

There are no rails on the caliper to allow the caliper to auto-center as the pads wear. So Every time the "piston" clamps, it has to actually bend the disc to engage the stationary pad. I can't imagine this will work for very long.

Both calipers do work and it does actually stop the bike... for now.

The mechanics of the caliper are REALLY simple so the isn't much room for any major failure aside from the cable slipping out of the caliper arm. The whole mechanism inside the "piston" consists of a spring loaded plate that ride on three loose ball bearings that roll up three ramps machined into an outer stationary plate. The outer stationary plate has a hole through it for the cable actuator arm. So you rotate the arm. the piston plate turns and the bearings ride up the ramp to compress the pad against the disc. And that is all there is.

yuck.

I did find the manufacturer of the bike, Cycle Force Group. ...Apparently part of Pacific Cycles.
(Correction: Cycle Force Group is not affiliated with Pacific/Doral in anyway.)

They were very responsive to email support and provided me with the missing assembly instructions. However the instructions did not have the particular calipers that were on this bike.

For what it's worth, Anheuser-Busch (Michelob) was also very responsive and offered to try to locate the bike manufacturer as well. Yusheng never responded to any emails for support on their products.

When these horrid things fail, I'll just replace them with one of my many piles of cantilever brakes. The forks are already drilled for a caliper brake but have the hard points for cantilevers.