Hoping for any advice from all you great folks.

My disc brakes have been driving me nuts (first time ever having them). I have a Montague Paratrooper (26" folding MTB) with Promax disc brakes (page showing adjustment system).

My problem is that folding the bike entails removing the front wheel. And about 1/3 the time I reattach the front wheel, the disc brakes are suddenly rubbing so I have to spend 10 minutes readjusting them. Is this a common problem for removing the front wheel (regardless of whether it's a folding bike or not)?

Options:
1. Suck it up and realize that it's price paid for superior brakes.
2. Change the front brakes to V-brakes for easier, adjustment-free removal. (It only rains here like 4 days per year, so I assume disc brakes provide minimal benefit.)
3. Change the front brakes to a disc brake that is either easier to adjust or less likely to get out of whack simply by reattaching the wheel.

Thanks for the help!

With mechanical (cable activated) disc brakes, typically one brake pad is stationary and the other, movable pad, compresses the disc against the stationary one. With these systems you can usually adjust the distance each pad is from the disc. You basically have the following options:

1. Adjust the pads so they are further from the disc which will give you more tolerance when you remove and reinstall the wheel but may give you reduced braking performance.

2. Carry a 5mm hex key and muck with the caliper mounting bolts in accordance with the site you linke to, each time you reinstall the wheel and find the brakes are rubbing. This should get the brakes to stop rubbing but can be a pain and the possibility exists that if you are not careful you may strip a post the bolts thread into.

3. Carry what ever other tools you need to adjust the clearance of the pads once installed. Possibly a little more time consuming but less chance of stripping something.

4. As an alternate method to what the site you linked to suggests...take a playing card and cut it in half. After loosening the caliper mounting bolts slide the 2 pieces of card on each side the disc between the disc and pads...squeeze the brake lever and at the same time tighten the caliper mounting bolts. Remove the pieces of card and check for rub by rotating the wheel...with a mechanical brake system you may want to glue two pieces of card together for the inner pad.

The problem is that incredibly small gap between pads and disc and the lack of tolerance in the fabrication of the fork dropout and hub axle.

With hydraulic disc brakes a quick fix is to set the tension of the quick release and then let it hang open, grab the brake lever and while squeezing tight close the quick release...but hydraulic disc brakes have pistons that operate the pads that retract. Your mileage may vary if you do this with mechanical disc brake because the inner pad typically does not move as mentioned above so this technique might just cause the disc to be pushed and set against the inner pad causing the problem to be worse.

Disc brakes tend to be fickle. Good luck.

-j

You should be able to remove and reinstall the wheel without the brake disc getting Bent.

Promax calipers were chosen to lower the selling price of the bike as a Whole

NB: there are easier ones to adjust, its primarily a friction material wearing thinner reason to adjust them ..



I Like bikes with the Shimano center lock front hub design, because the disc is held on with a lock ring, which is the same spline type as their cassette lockring.

When repacking tourists bikes to ship home , the disc comes off the hub and gets packed separately so It wont get bent in transit ..

I have the same splined hub type on the Schmidt dynohub, that is fitted on my Bike Friday pocket Llama, with Avid BB7 calipers.

What's your procedure for removing and reattaching the front wheel? There may be a 4th option.

If you flip your bike upside down when you do this, it's common for the hub axle not to seat all the way in the dropouts. If that happens, it'll make your brake rub. I prefer to reattach the front wheel with the bike standing up and push down on the stem to seat the axle in the dropouts before tightening the front wheel.

Thanks for the tips guys. I like Greenfieldja's tip about using playing cards for a quicker adjustment; I'll give that a try.
But it's sounding like I should replace the front disc brake with a V-brake.


Yeah, I reattach the wheel with the bike standing up. In fact, if at first the disc brake rubs, then I reattach the wheel 3-4x more in the hope that it stops rubbing one of those times. If it keeps rubbing, then I sit on the ground, have a brief cry, and get to work readjusting the brake housing (since the gap isn't the issue).

Sorry you are having so much trouble. I have disk brake bikes and have no trouble removing and remounting them. Something isnt quite right.

One step left out of the guide you posted a link to, is AFTER making the adjustments they demonstrate, hold the brake ON and loosen the mount bolts, then re-tighten them. This will make the caliper more parallel to the disk than just eyeballing it. That might solve your problem.

-SP

And this is why quick releases are terrible for disc brakes...

The best solution is to make sure you ALWAYS put the wheel on with the exact same procedure. Sometimes centering the QR on lawyer lips is more repeatable than the top of the QR slot. Basically, you need to tighten the QR with the wheel lifted off the ground, and ideally the brake clamped.

There is ABSOLUTELY no technical reason you should be having this problem. After all, mtn bikers have been using QR's on disc brake wheels for over a decade, and we don't hear a flood of complaints about mounting wheels without rub.

Consider ---- The disc is securely attached to the wheel, so it's not going anywhere. The wheel should be able to mount in the exact same place, so so close that it doesn't matter, especially since you're mounting it when the bike on the ground, and using gravity (which I'm told is a very reliable force) to settle it home.

Lastly the caliper is securely mounted and shouldn't move, but then again, maybe that's it issue. Is it possible that when folded, something is bumping the caliper and moving it?

Try correctly adjusting the brake, then removing and remounting the wheel a number of times and see if it repeats consistently. To do this right, start with the brake adjusted wide open, then opening the QR, settling the wheel, and closing it to ensure that the wheel is settled in the fork free of any influence form the brake. Then set the brake, and see if things stay put.

If you can remove and mount the wheel w/o disc rub when not folding the bike, then that implies that it's the caliber and not the wheel that's moving.

I am interested in the OP's little hidden comment about fiddling with the brake housing after putting the wheel on . I suspect there are root issues with the adjustments on the caliper itself, and unless those are right, no amount of tightening or slackening the brake housing will fix the issue.

Your cable-actuated caliper has a fixed pad and a moving pad. Use the playing card trick, but only on the fixed side. Bike upright with the wheel in place, q/r skewer open. Slide card in between pad and rotor on the fixed pad side. Squeeze brake lever while tightening closing the skewer. Your brake should be centered on the rotor.

I've not used this method, but I have had mechanical disc brakes in the past. This is the way I would approach it. Good luck. PG

Try marking the axle with a dot of paint so it can be placed in the same rotational position every time you put the wheel back on the bike.
Some people have found this works to stop rubbing.

https://forums.mtbr.com/general-discu...ff-781795.html

Answered over in the Folding forum. Note,your fork doesn't have canti posts,so switching to a V brake isn't an option unless you swap the fork. Also,realize that switching to a V brake means you have to open/close the brake when removing/installing the wheel,meaning you can forget to close the brake,something that's not possible with discs.