Issues with front hub motor on aluminum shocks.

J

jcool3

100 mW
Joined
Jun 18, 2017
Messages
39
Location
san francisco
Are there issues with mounting a front hub motor on aluminum bike with suntour shocks. Would regular torque arm work?
The bike is a Specialized step-thru. My other bike has a rear hub motor and it is such a complete hassle to change flats! suntourweb.jpg
 
If I had a dollar for everyone who has asked this question, been told it's a bad idea, decided to try it anyway, and then come back to post how they had broken their fork, I'd be be able to buy a Zero FXS.
If I had a dollar for everyone who's asked, been told No don't do it, decided to try it anyway, and then never returned to post anything again, I be buying the Zero with blood money.


It's a bad idea. Sometimes it works fine. With a low powered motor and getting the install right every time to remove the wheel, it will work without problems. Get things a little wrong, and most motors have enough power to twist in the dropouts. Aluminum, especially the cast aluminum used in cheap suspension forks tends to crack and break off when that happens, leaving you very suddenly with no front wheel. Losing your front wheel is a very painful way to crash.
 
The trick when breaking a fork, is to keep the eyes on your front wheel. It will end up behind so you will roll to your ass, instead of digging the trail with your face.

Just in case you persist with the idea, and to make sure you can come back to tell us. :wink:
 
jcool3 said:
My other bike has a rear hub motor and it is such a complete hassle to change flats!
Click to expand...

Learn to repair a flat with the wheel inside the frame! :wink:

Yeah i understand that for a new tube you need the wheel to come out the frame...
 
Benjamin Wassink said:
jcool3 said:
My other bike has a rear hub motor and it is such a complete hassle to change flats!
Click to expand...

Learn to repair a flat with the wheel inside the frame! :wink:

Yeah i understand that for a new tube you need the wheel to come out the frame...
Click to expand...
have done that, still a major hassle ....
 
I had a cheap, cast aluminum suspension fork break with a rear hub motor. Wasn't even going fast. Just not strong.
 
jcool3 said:
have done that, still a major hassle ....
Click to expand...

Yep. That's why I've made my rear tire more puncture resistant. Given that I already have a rear hub motor, that seemed to be the simplest and least expensive approach.
 
I snapped both AL fork dropouts in the first meter of my first hubmotor ride. Luckily my dual torque arms kept the wheel on the bike and avoided the face plant.

Flats are a pain on a hubmotor whether on the rear or not, so I switched to moto tires a decade ago and would never go back.
 
wturber said:
jcool3 said:
have done that, still a major hassle ....
Click to expand...

Yep. That's why I've made my rear tire more puncture resistant. Given that I already have a rear hub motor, that seemed to be the simplest and least expensive approach.
Click to expand...
Unfortunately I went thru an episode with 3 flats within a week on my rear hub motor wheel. Finally figuring out that the xlm thorn resistant tubes were defective .... the presta valves were leaking at the base which was impossible to fix.
 
Re torque arm, not sure, but many I've heard of had them, and still broke off the dropout tips, but at least had the wheel stay semi attached to the fork.
I've had bad luck with extra thick Prestas, the stem attachment area is so small it rips off easily, esp if the air is a little low to where the tire creeps around the rim during hard braking. Maybe drill your rim for Schrader valve if the rim is wide enough?
 
When you build a bike, the tires and puncture proofing are way lower in the priority list, than making a rear wheel mount that is planned for quick servicing.

Pinch dropouts are simple and safe, quick and easy.

Not applicable for all frames, bolt-on through axle dropouts are also very quick to service.
 
jcool3 said:
Unfortunately I went thru an episode with 3 flats within a week on my rear hub motor wheel. Finally figuring out that the xlm thorn resistant tubes were defective .... the presta valves were leaking at the base which was impossible to fix.
Click to expand...

Yup. My most recent flat was a presta valve base failure. But that was on the front wheel. I'm at about 3500 miles without a flat on the rear now. I've had no rear flats since I went with the "tire inside a tire" scheme.
 
wturber said:
jcool3 said:
Unfortunately I went thru an episode with 3 flats within a week on my rear hub motor wheel. Finally figuring out that the xlm thorn resistant tubes were defective .... the presta valves were leaking at the base which was impossible to fix.
Click to expand...

Yup. My most recent flat was a presta valve base failure. But that was on the front wheel. I'm at about 3500 miles without a flat on the rear now. I've had no rear flats since I went with the "tire inside a tire" scheme.
Click to expand...
these were all presta valve. My first blow out, the presta valve was gone so I had no idea what was going on. The second leak occured during installation. I took off the wheel, put in a new presta valve tube and it started leaking immediately. The third
install I rode for a couple days and then flat .... leaking presta valve. Those were xlm thornproof tubes from Random Bike Parts.

Thinking of going to a mid motor instead of front or rear hub motors.
 
markz said:
Justin rode across Canada with a front 500W hub.
https://youtu.be/oCvo6ffWRdE?t=272https://youtu.be/oCvo6ffWRdE?t=272
Click to expand...

... and a non-suspension steel front fork. :^)
 
jcool3 said:
the presta valves were leaking at the base
Click to expand...

Failure at the base of the stem usually means the pressure was too low, so the tube and tire was able to move around the rim, which tears the stem at the join with the tube.

You don't see the movement in a presta tube (cuz it's fixed to the rim by the nut), but you can easily see it in a typical schrader tube (the stem looks tilted in the valve hole).
 
amberwolf said:
jcool3 said:
the presta valves were leaking at the base
Click to expand...

Failure at the base of the stem usually means the pressure was too low, so the tube and tire was able to move around the rim, which tears the stem at the join with the tube.

You don't see the movement in a presta tube (cuz it's fixed to the rim by the nut), but you can easily see it in a typical schrader tube (the stem looks tilted in the valve hole).
Click to expand...

That's possibly what happened. I drilled the rim out and am now running Schrader on the front. It was dumb that I had presta on the front and Schrader on the back to begin with. Really dumb actually.
 
Nothing really dumb about using two different types, though it means having to carry two kinds of spare tube (unless you carry two presta, or two schrader and a drill ;) ).



I haven't used presta in...forever (other than what came on that Trek), but I've had this happen with schrader valves numerous times, both in powered (from acceleration and braking) and unpowered wheels (from braking, mostly, sometimes on rear wheels hauling heavy loads, mostly back in pedal-only days).

So lots of observations to draw conclusions from, unfortunately. :(
 
wturber said:
jcool3 said:
Unfortunately I went thru an episode with 3 flats within a week on my rear hub motor wheel. Finally figuring out that the xlm thorn resistant tubes were defective .... the presta valves were leaking at the base which was impossible to fix.
Click to expand...

Yup. My most recent flat was a presta valve base failure. But that was on the front wheel. I'm at about 3500 miles without a flat on the rear now. I've had no rear flats since I went with the "tire inside a tire" scheme.
Click to expand...

what size tire do you have inside and out?
 
jcool3 said:
what size tire do you have inside and out?
Click to expand...

Outside is a 26X 2.0 Bontrager. Inside is the tire that came with the ebike kit wheel. I'm not sure of the size. I think it was 1.95 or 1.85. Here's a couple of pictures of what I stuff into the Bontrager. The combo is a thicker than normal tube, an anti-flat tire liner,
and the old tire with the sidewalls cut off. I use rubber cement to glue the anti-flat liner to the tube. I just use one thin coat which is just enough to keep the liner in place as I stuff the three piece sandwich into the tire. The rubber cement is flexible enough to give and let everything expand as needed when the tube is inflated.

file.php

file.php
 
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