Front fork failure
- Thread starter Giant
- Start date
johnrobholmes
10 MW
Never seen the failure, but putting a motor on a suspension fork is asking for trouble. I had stanchions come loose just going down stairs backwards. Having a motor pull on the fork in that direction can pull a cheap one apart!
michaelplogue
10 kW
For front suspension forks, you might consider a springer-style setup. These ones will fit most bikes. One would probably want to have some beefier steel rockers made, but these should work just fine with a front hub motor.
Johnbear
10 kW
I have personally had one. It happened from a dead stop and tore the dropouts out. I have since sold my front motors and bought rear motors. No problems since. If you go front definitely use a torque arm or two!
Johnbear
10 kW
It was a golden motor, roughly 500 watts rating - at 36v. I had the forks for quite a while, but I did turf them when cleaning up. I should have taken a picture!
etard
100 kW
I had the fork dropouts just rip right off. Brand new forks 
You have to be careful when accelerating from a stop, cause thats where the maximum torque forces are. I only had the stock WE BL36 torque arms, which aren't sufficient. The dropouts on aluminum forks just aren't built for the twisting forces of a hub motor. Instead use the heavy duty toothed torque arms from amped bikes, expensive, but worth it. Or just get a rear hub.That springer fork is a good idea, I dont see any brake mounts though.
You have to be careful when accelerating from a stop, cause thats where the maximum torque forces are. I only had the stock WE BL36 torque arms, which aren't sufficient. The dropouts on aluminum forks just aren't built for the twisting forces of a hub motor. Instead use the heavy duty toothed torque arms from amped bikes, expensive, but worth it. Or just get a rear hub.That springer fork is a good idea, I dont see any brake mounts though.
dogman dan
1 PW
1100 miles on my cheapie steel suspension forks. WE brushed hub at 36 volts. Do lots of no peadling starts unless it's uphill and that will trip my controller. No torque arms. 40 mm travel sucks but it's enough for the commuterbike. Some of the bumps on my bike route can get me airborne when I hit em at 25mph. You have to vise squash the fork tips to make a hubmotor fit, but I abuse it pretty hard and no problems. Of course the cheap forks only fit cheap bikes sooooo.
michaelplogue said:For front suspension forks, you might consider a springer-style setup. These ones will fit most bikes. One would probably want to have some beefier steel rockers made, but these should work just fine with a front hub motor.
dont buy theses fork for ebikes...
theses forks are known for failling at the steertube/crown juction. its been recoded at multiple custom bikes forums (ratrodbikes, chopper bicycle.net etc..)
according to crossbow it has only affected 5 fork out of 600 sold but who would take a chance!
to make sure i sent an email to crossbow today and they are the ones..I also asked him about using them for a front hub motor and he said
dogman dan
1 PW
I figure if my cheapie forks fail, it will be at the headset. But then any fork is about the same there, so I'm not worrying.
diver
1 kW
well , darn it. I just bought a cheep spring fork from choppers r us with hopes of using it with my x motor with a little beefing up. I never gave a thought of the stem tube breaking at the head set. i will now look real close at that and hopefully may be able to beef it up some.
dogman dan
1 PW
Maybe it has to do with the length, giving it leverage there that a shorter fork doesn't have? Maybe you can just weld on some strengthener gussets there or something. Cost you some chrome for sure though. Looking at the pic, maybe a stronger tube inserted in the bottom of the steer tube, and welded to the forks?
johnrobholmes
10 MW
The issue is at the crown and steer tube. Most forks are press fitted. They don't like being wiggled back and forth.
The reason I asked this is that many (most?) of the premade ebikes have front motors w/ front suspension forks (2 examples are Ezee and Giant brands), and I just hate to remove a perfectly good cassette/freewheel that was factory made and fitted for the bike in the first place. The front hub seems a simpler, more elegant conversion that interfers less with the overall design of the bike. I was planning on converting a $500 bike. What I am saying makes less sense with less expensive bikes.
diver
1 kW
the springer works really well for me so far. on acceleration the spring seems to dampen the torque of the motor to the stem. I had to weld on the stems on forks for the brakes. over all i really like it. No more handle bar vibration over bumps. I hope it holds together ,only time will tell
BiGH
100 kW
The springer looks good- you could probably replace the bottom metal parts for some with thicker dropouts 
heck if you made them removeable - you could actually have torque arms that wrap 100% around
heck if you made them removeable - you could actually have torque arms that wrap 100% around
totals
10 mW
I run a 5303 on a front steel suspension fork. No problems. Will report as time goes on.
I'd say hub motors are bad on threaded type headsets. The steel headset tries to unscrew and the top lock nut is made from aluminum and after about 1000 miles it strips out from force and pressure. Loctite does nothing. I went through 2 nuts before changing to a threadless fork.
dogman dan
1 PW
On cheap bikes the locknut is steel. get one of those. Getting close to 2000 no problem miles on mine. I doubt your problem was strictly related to the motor. But some bikes just don't stand up to real use, even expensive ones. Not arguing that threadless is not better, I'm just saying there is more than one way to solve any given problem.
snowcrow
100 W
It could be stainless steel. I used stainless nuts, washers, and, threaded rod, when building my wind generator.D-Man said:
Blessings, Snow Crow
dogman dan
1 PW
Yes it could, stainless will not stick to a magnet. But I have come to hate stainless screws since they strip the heads about as easy as brass. My source of parts has become the flea market and garage sales. I buy any bike in any condition for 10 bucks if it has just one part I can, might be able , to use on it. I'm just about done with the bike shop jerks.
I know magnets don't stick to stainless steel. Its got a chrome plating on it whatever it is. Notice how the threads have flattened on one side only. This is what I think the hub motor does to the lock nut. The is the 2nd lock nut the bike shop gave me. They claimed it was steel. But here. You be the judge:
dogman dan
1 PW
Seems to me that would happen if it was loose enough to rock a little. Quite possible the same thing is happening to mine, but mine rust where the paint rubs off so it may just be taking longer. If yours is stainless I would guess it is softer than the nuts on my forks. I'm running a steel cheapie suspension fork, so maybe the slop in it takes some of the strain off the headset on my bike too.
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