Secure Braking

S

sbturtle

10 mW
Joined
Sep 14, 2018
Messages
21
I'm using a 240/350 watt front UrbanX wheel - not exactly sure of the wattage, it was used when I purchased it.

I have hydraulic brakes and a non-suspension steel fork.

I have attached a torque arm, c washer, an anti-rotation washer, and lock washers. I cannot fit washers between the hub and my fork, there's no space.

This is what happens:

If I go fast and brake hard, the front brake caliper goes slightly out of alignment or the wheel does - difficult to determine which.

Has anyone else experienced this?

What can I do to better secure the wheel and/or the front brake caliper?

Thanks!
 
Washers are usually meant to go on the outside, unless you need them for spacing.
 
Is this site incorrect about the axle washer?

http://www.ebikeschool.com/install-hub-motor-washers/

Anyhow ... do you know what could be causing the caliper and/or wheel to shift on a hard brake?
 
Depends on the motor.
If you have to spread your dropouts out ( IE it's a good fit *without the washers* ), don't use the washer inside because you don't need them.

With no pictures to go off, i'd assume you're bending your dropouts outward and that's interfering with the disc brake..
 
No bending. This is what the disc brake side looks like. Nothing is touching. But if I hard brake I have to recalibrate the caliper or wheel.

disc brake.jpg
 
Something is misaligned or bending under load.

You might notice if you stare downwards while you brake.. ( but don't shift your weight forwards too much otherwise you'll do a reverse wheelie :)

How big are those hydros? perhaps the fork is bending diagonally because the things are too damn powerful for the fork..

203mm hydros can easily snap lesser aluminum suspension forks in half.. so there is sure as hell some bending going on here.
 
Just a guess, but usually the washers that come with the motor are too big to fit in the circular recess around the dropout in a fork like normal bike axle washers do, and no matter how tight the nuts are it slips around a bit.
 
Holding the motor washers in vice grips and taking them to the bench grinder until they fit in the recess worked for me. A cup of water for cooling them off for test fits is pretty handy.
 
I don't do fronts much, anybody have any input on whether or not that's the direction of torque arm mounting that promotes it rotating the axle down out of the dropout?
 
I wonder if the torque arm is pulling it slightly to the left and that's exactly where it tends to rub after a hard brake. Should I get a second torque arm for the right side of the fork?
 
If the axle doesn't tighten down securely, the brake will tend to push the axle down on that side, towards the opening of the fork tip.

If your fork has "lawyer lips"-- raised ridges at the bottom intended to keep a loosened wheel from falling out-- get rid of them. Carefully file them down until they're flush with the clamping surface. When you use an axle that isn't 10mm or smaller and round, it won't locate at the same center that the lawyer lips were designed to accommodate. You have to make them go away so the axle nuts can tighten against a flat surface.

Once you're able to affix the axle nuts securely, braking forces should stop shifting your wheel out of place. Remember to put a dab of grease on the axle threads so your fastener torque goes towards making clamping force instead of fighting friction.
 
Appreciate the advice, but I'd rather avoid removing lawyer lips at all costs because they are meant for safety, especially if I use my non-ebike wheel again. This fork is much more valuable than the ebike hub. If it came down to that I'm better off waiting to get a rear ebike hub or getting a different fork.

Only one side of the wheel has an anti rotation washer (which sits flush with the lawyer lips) and a torque arm. I use a c washer for the other side but I doubt it's helping. I ordered a second anti rotation washer so both sides will have them.

Is there some kind of material that can be put in between the washers and fork to fill in any minor gaps? Like when using grease or loctite to fill gaps in bolt threads.

Would a second torque arm help or make no difference?
 
Front motors are a pain for this reason. They should only be used when the bike is very very special and cannot use a rear motor or you want to keep a rear IGH..

Lawyer lips only become anti-safety devices when your washers hit up against them and mess up the interfacing.

i think it's very likely that your fork is twisting under hard braking if those are 203mm hydros.
Those brakes are kind of excessive for such a low power bike, unless you need to go down 10% grades regularly or something..
In that case, i'd be running a rear direct drive with regen braking to do most of the braking.. and throw a basic vbrake or wimpy disc rotor up front to do the rest of the work.
 
Yah. They are 160 but I'm going down 10% and steeper grades for up to 5 miles distance and returning the sameway uphill.

I paid a super low price for the hub because it wasn't working but I managed to fix it (bad throttle).

Changing to another type of ebike hub will be a consideration in the near future when the budget permits.

For now, I'll attempt the following:

Second anti rotation washer.
Second torque arm.

Question: Do anti rotation washers and c washers serve a similar purpose? They appear to fit identical except one is a complete washer that also has a tab.
 
All you really need is 1 washer that sits flat on the frame ( to prevent the nut from grinding away your axles ) and a nut to secure the axle to the frame.
And the torque arm needs to be somewhere in the mix. The closer to the dropout, the better.

My preferred order:
torque arm
washer - 2mm-3mm thick is enough
Bigass bolt.

ps i'd absolutely run nothing BUT a direct drive in your condition. Brake fade and brake wear with those extreme kinda hill declines is gonna be an issue. I understand why you chose a hydro brake!
 
And just an FYI, depending on how much you value your time, if you have a whole working system you got cheap, a new rear motor is pretty cheap and easily gotten these days, by the time you grind lawyer lips, or more torque arms or switch forks etc, you could just go rear...
 
I'll keep an eye out for a good rear hub deal but when I do that I'd like to get something that resists moisture. Here there's a morning marine layer that's equivalent to rainy conditions.

The wheel alignment issue is exasperated by the ehub but was a slight problem with the regular wheel too. So, if I can super secure this ebike hub it won't be done in vain as I'll keep the same method for the transition to a regular front and e-rear.

Yah, brake fade is a problem. I've learned to use a kind of fast alternating brake (left right, left right and so on) technique to avoid overheating.
 
Torque arm on one side only, does make the fork twist a bit under braking and acceleration. That can be corrected with a more precise/tighter fit, or by adding a torque arm on the other side.

Some disc brakes are more tolerant to slight misalignment because either they release way off the rotor or they are floating on a lateral pivot, usually big calipers that are the most expansive.
 
Do as much braking on the rear as possible because rears can handle a lot more force.
The larger the rotor, the more the rotor can shed heat. I'd put the most monstrous sized rear rotor on the rear and then proceed to use 1/2 or less of it's braking capability.

If you had this braking problem before but it's exaggerated by a hub motor, i'd imagine the theory about the fork being a bendy little thing was correct.

ps - if regen is tuned correctly, it's like having a brake that never fades. It is a way better option than throwing more money at the brakes.
 
I tried to put a 180 on the rear, but it didn't fit. I used to have a 180 in the front, but it felt too bitey and lacked modulation - at least with the regular wheel. I may revisit a 180 for this one, but for now, my primary goal is to get that balance. If I put a 180 in the front, it may introduce more of the same problem.

How much does a regen rear wheel cost? Is it water resistance?
 
The motor is the same, as long as it's direct drive... It's the controller that makes the regen happen. But realise youre then getting into really really needing torque arms and non slipping axles once the alternating drive and regen starts making the axle rock back and forth.
 
Rear brake can’t achieve adequate braking distance to be safe in emergency braking situations. Your best brake should be on the front, and it should be good enough to make the rear just about useless in emergency braking. If not, then you need to be conscious of your long braking distance and ride accordingly, keeping a longer distance from other vehicles ahead, and slowing down when approaching any potential hazardous situations.

Testing your braking distance at various speed and to be conscious of it, is a must. Working on your bike and skills to reduce your braking distance, is your best investment in safety.
 
Since I'm riding down steep hills for long periods of time, I tend to alternate my braking when I stop or slow down -- so I use a technique such as left/right/left/right in rapid succession till I slow or stop. I don't know if that's the correct way to brake but it's how I've avoided overheating them.
 
On two of my bikes, I have four brakes. Four cables. Four levers. 2 disc, 2 rim.
Each hand has front and rear. One finger on each.
Not only can I rest brakes on long downhills, I can rest a hand, shake it out, change hands, change brakes.
Redundancy, super stopping power with four fingers, less pad wear because nothing gets hot.

Of course you need a frame/fork and rims that can take rim brakes, but maybe you have that.
 
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