Hope Mini Disk Brake Fix

Note:  See the update at the bottom of this page...

I found a design flaw with the Hope Mini disk brakes.  The caliper is split in two halves that are bolted together at two places on either side of the brake pads.  This leaves the top of the caliper unsupported.  I found I was having trouble with the brake leaking and fading.  When grabbing the brake hard, the top part of the caliper would separate and allow oil to leak out, soaking the pads and coating the rotor.  

Lets just say I wasn't very happy about this.  I've had problems with Hayes brakes and was hoping the hopes would work better.  Chris at Speedgoat came to the rescue.  I talked to him about the problem and he helped me diagnose it and gave me his solution.  He's been using wire to wrap around and twist it to give some clamping force... kind of like wire is used to fasten BMX grips to handlebars.  It worked for him pretty well and his brakes felt better.   I wanted something a bit more solid and permanent. 

Here is the solution that I found. 

Materials:

Most hobby shops that sell RC Cars and airplanes should sell the bolts, washer and lock nuts.  The other item in the photo above is the Hope screw that is used to hold the brake pads in. 

Wrap the hose clamp around the upper part of the caliper, right below where the hose fitting and bleed valve enter the caliper.  Tighten it down.   If you're using the 90 degree hose fitting, be careful that the clamp isn't pressing against it.  If its touching, the clamp can rub against it and weaken it.  I've broken a hose fitting already.  When its tight, it should look like this:

Caliper with clamp

Caliper with clamp.

Once you've done this, bleed the brake and make sure there are no bubbles in the lines.

The next part is also pretty easy.  Chris at Speedgoat gave me this idea.  Remove the bolt that holds the brake pads in.  Leave the pads and rebound spring in.  Replace the bolt with the 4-40 bold that you got at the hobby store.  Make sure the washer is on the side of the screw head.  Tighten the lock nut on the other side.  I used an aluminum lock nut to make sure I'm not able to apply too much force to the caliper.  This area of the caliper is unsupported, so it could distort if you clamped it too hard. 

On top is the new screw, washer and lock nut. On the bottom is the original bolt.

 

Here's what it looks like at the end of the project.

Clamp with a 90 degree hose fitting

Clamp with straight hose fitting.

A few other comments on the Hope Brake.

Get rid of the 90 degree hose fittings.  They come stock with the Hope Minis.  They don't handle pressure very well and they're quite fragile.  I got mine from Speedgoat (1-888-545-GOAT or www.speedgoat.com).  Chris at Speedgoat really knows his stuff and is very willing to help.  Quite honestly its the best place to purchase a bike. 

Before this problem happened... for the first few months I had the Minis, they were the best brakes I'd ever used.  Not all Minis have this problem. There are lots of people that have given positive reviews on MTBR.com.  Hopefully this will help a few of the ones who have problems with squealing and fading. 

Update: 09/13/02

Chris from Speedgoat proved himself the coolest guy in the bike business.  After all the talking and e-mailing that he and I did over the last month, he got his CNC guy to come up with a prototype clamp to test out.  Here's what it looks like:

Big close-up

Another close pic.  

I made one tiny change before installing it.  I'm somewhat partial to hex bolts for the clamps.  I replaced the slot head cap screws with the hex bolts that you see here.  The fit was perfect.  Don't change the bolt size, Chris.  The 4-40's work perfectly. 

Here's what it looks like installed. 

From the back.

From the side

Another view from the back.

From the other side. 

Installation was very easy.  It took me 2 minutes and that's because I had to hunt for my SAE hex keys.  It had better clamping force than the hose clamps I was using.  

I took it for a small test ride and found the brakes felt even a little better than the old hose clamps.  Check with Chris at Speedgoat in a month or two and he'll have a final version for sale.  I'll get another that matches for the front when they're available.  I'll be going on two epics this weekend to test out the new clamp.

Thank you, Chris!  As I've told you for years, y'all are the best!

 

If you've got any questions, please drop me an e-mail at pedrogringo@yahoo.com.