First Post Questions

[Jethro56]

I have a Trek 7300 Hybrid That I'm considering as a candidate for an ebike. What I would like to do is purchase a geared front hub 48V lipo system from e-bikekit.com. I've read where front aluminium forks are not a good idea to power. The suspended forks are Suntour NEX 4110 TK. The upper tubes are definitely steel. The cast lower portion has some magnetic properties but not enough to hold the magnet up.Will they standup with a torque arm?

If I go with a rear drive I would like to stay with the eight speed if deraileur adjustments are unnecessary. The reason for this would be for ease in going back to non ebike uses. Somehow I think this may be unavoidable as the necessary shims will move the deraileur out of alignment.


While I'm at it. I noticed most pictures of ebike conversions show full suspension mountain bikes as the donor. Is it because of speed or durability or availability?

Any comments would be greatly appreciated.

 

[MadRhino]

I would build rear, yet upgrade your Suntour. The freewheel that you have now, you'll keep it on your actual wheel, so you can always put it back. Usually, you won't be able to set as many gears with the hub motor, depending of the width of your dropouts, and the motor itself.

Most who are after performance, build on FS bikes for the obvious reason that speed handling requires stiff frame, suspension and disc brakes. A DH or freeride bike has it all already, and is ready for performance.

 

[torker]

No geared motor here so I don't know about the 8 speed. As far as the suspension. I run front suspension and 2.3" tires and wish I had rear susp. also. My bike only runs 20 mph. but I tend to run 20 mph. everywhere I go now. Around corners, up the alleys And I do it all in high gear, I haven't been out of 7th gear since I electrified it. I pedal but I don't contribute much. It did not make me lazy, I am sure I was already that way Oh , Rear motor= much safer esp. with alum/magnesium forks.

BTW Welcome to ES

 

[Ykick]

I run a direct drive (DD) front hub with suspension fork but it's one of those cheapo steel 105 Ballistic forks that came on Walmart mtb's. Not even fair to call it a suspension fork but it does spring a little. However, even though it's steel I also run 2qty torque arms on each side.

YMMV but I'd be cautious of powering an alloy suspension fork without a pair of steel arms - especially with a geared motor as they seem to develop more torque at startup than DD.

Full suspension is better IMO for anything above 20MPH. Shit in the road, potholes, etc. The extra weight of motor, controller, batteries just begs for some suspension help under most +20MPH conditions.

Perhaps find a garage sale or Craigs List donor bike for your 1st attempt? If for no other reason, the spare parts might come in handy? I guarantee most usually build a 2nd rig after learning what's what from their 1st.

 

[Drunkskunk]

Welcome to the forum. If you got the magnet to sort of stick to the front forks, but not hold, then you were sticking to the spring inside, through fork. that model fork does have aluminum lowers, and that's the part that matters. Its not suitable for a front motor.

The problem you will have with the rear is that all hub motors use a freewheel cluster, where your Trek uses a cassette. the only ( and rare) 8 speed freewheels are spaced at the 5-7 norm, where cassette 8 - 9 speeds are narrower.

Your best bet would be to use another bike, one meant for 7 speeds in the rear, or that has a steel fork. An older Trek 800 from craigslist might work for a front motor, as it doesn't have a suspension fork. 820 has a suspension fork, so good for a rear motor. older versions were 7 speed.

I think most people here actually ride hard tails, or no suspension at all, but those who have the big DH full suspension bikes like to show them off. Its like a car magazine. Most of the readers and writing staff drive things like honda accords, toyota cameries, and ford focuses, but the cover of the magazine will have a Ferrari.

 

[Jethro56]

Drunkskunk has voiced my uninformed concerns. I guess I didn't realize the 8 speed freewheels had a different spacing than cassettes. That means the indexed shifters I like so well won't work either or is there a workaround that doesn't occur to me?

 

[StudEbiker]

Dogman has posted a thread on how to safely run front hubs on AL sus. forks. It used to be completely verboten, but I think some people have come up with a system for safely running 48v on AL sus. forks.

http://endless-sphere.com/forums/viewtopic.php?f=4&t=15167&p=225410&hilit=Torque+arm#p225410

 

[Jethro56]

So I am assuming the real issue with al suspension front forks is the danger of spinout and not bending due to the transmission of force to propel the bike. I have access to a mill so the fabrication of custom torque arms is manageable. This bike is a 700c model will this further complicate the torque issue?

 

[Ykick]

It won't bend, it will break. 2 arms might give you time to stop. Might not...

 

[spinningmagnets]

Steel dropouts are more likely to spread open, allowing a spin-out, which will pull the wires out at their roots. Aluminum alloy drop-outs are more likely to snap off, often resulting in a crash.

 

[dogman dan]

The even bigger issue with the alloy forks may simply be that a gearmotor won't fit between them, period. So start with measuring the forks between the tubes, and see if the motor covers even clear the tubes.

You can run front hubs on alloy forks, using the proper washers and torque arms, and experience. But you haven't the experience, and I only recomend the alloy fork with front hub to those with hands on knowledge. It can be done by a noob who sees, but not by one who merely looks. Only 10% of us see.

Fornt hub is nice on street commuter bikes, so maybe just hunt down a fork that does work. The trek 820 has such a fork, if your lbs has one on display you can look at them. Basicly still a cheap steel fork, but 60 mm instead of the wallbike 40 mm ones. Or even use a hard fork till you get the experience with the fitting process you need to go alloy.

Rear motor is not as big a problem as you may think. Rear and disk brakes can be a hassle to find the right washer combinations to get it all aligned. I haven't had any serious problems running a 7 speed or smaller cluster on an 8 speed bike though. 9 speed is where the indexing really starts getting too different. All you have to do is re set your limiting screw on the inside to 7 gears instead of 8.

Besides, you are going to only use the derailur when you break down. You'll stay in high gear nearly permanent, unless you have steep hills to grind up.

 

[motomech]

Dogman has posted a thread on how to safely run front hubs on AL sus. forks. It used to be completely verboten, but I think some people have come up with a system for safely running 48v on AL sus. forks.

http://endless-sphere.com/forums/viewtopic.php?f=4&t=15167&p=225410&hilit=Torque+arm#p225410

I am one of those folks. No concerns.

http://endless-sphere.com/forums/viewtopic.php?f=2&t=23897&p=347689#p347689