Ebike crank arms

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Philaphlous

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Hey guys....need some help here.

I've got an electric trek 80C sport (basically an 800) and one of the torque arms is completely destroyed by myself for not being able to screw in the pedal...I know there's a right hand and left hand thread for each. I also destroyed a cheap aluminum pedal when I wrecked my bike last year...like half the pedal is still in tact.

In order for me to ride the bike and actually pedal I need a new crank arm. I believe it's the left one that is not on the side of the sprocket. Id like to replace these and possibly with cheap crank arms...? I'm not sure if I need a square or rhombus hole crank? Does anyone know. And it seems eBay has mostly left crank arms...not right? What gives? The crank arms aren't attached to the sprocket so they're very similar except for the pedal screw direction...

Thanks guys! I'd love to get this fixed because this is the #1 issue why I don't ride my bike right now. Im point to spend under $20 also.
 
You need the same, ideally. Another might have slight differences in lenght and width, that you will feel and find bothering.

Usually, they are available unless very old. Yet a whole used crank of a better quality can be found pretty cheap.
 
since the bike is made by Trek then you should be able to take it to a trek dealer or your local bicycle shop for repair.. damaged pedal threads on your crank arm can likely be repaired by installing a "helicoil" replacement thread insert.. if the cranks are shimano brand then check the back side of the crank arm for the manufacturer part number.. on a trek 800 or similar level bike it probably has square taper cranks and crank axle spindle.. any pics of the damage??
 
I can only google up trek 80c without motors. A link for exactly what you have would get you more specific answers.

80c appears to be a dirt jumper, while 800 is the common steel mtb that is a great choice for hubmotor conversions.

If its a hub motor bike, you just need to match the type of crank, and can easy enough replace both sides. New or used.

By this I mean mtb type crank for mtb, road crank for road bike, etc, and of course the type of spindle. On less expensive mtb's, almost always a common square taper. You will need the crank remover to properly get it off the bike, or have a shop pop it off for you. Look of course, for the length of crank you want, particularly if you replace only one side. 175mm is common, but some bikes have other lengths, 170,165 or whatever. the length will be stamped on the inside of the crank, facing the frame.


If its a mid drive, then chances are you need a factory replacement part. It could be anything for the spindle, including a crank with internal freewheel.
 
I'll get a picture up today. I'd rather buy a new one.id probably end up spending more to fix it at a shop in my area. Standard of living is like 60% higher in my area that the rest of the country...gotta love Bethesda Maryland!
 
Looks like a 170mm length. The threads are totally destroyed. I even tried to drill 2 holes through the crank arm and pedal to keep it attached with no luck...

40080694641_cb20d427be_h.jpg
 
Philaphlous said:
Looks like a 170mm length. The threads are totally destroyed. I even tried to drill 2 holes through the crank arm and pedal to keep it attached with no luck...

40080694641_cb20d427be_h.jpg
Click to expand...

looks like it says Suntour / 170
so now you know the brand and length..
next you will need a crank arm puller for square taper cranks in order to remove the crank arm from the bike.. maybe call your local bike shop and ask them for the cost of removing the arm for you verses the cost of the needed tool, probably close to the same price.. assuming that you order the correct tool and crank arm then the tool will only be used once.. whereas if you go to the bike shop then this should ensure that everything fits and is tightened to recommend manufacturers spec so that it shouldn't happen again..
if you decide to fix it yourself then you will need to remove the crank fixing bolt with the correct size socket or allen wrench.. then tread in the puller securely with lots of thread engagement, then screw in the puller bolt.. the puller bolt will then push on the spindle thereby backing the crank arm off the spindle..
 
Is this a mid drive you're dealing with?

If so, you might have the arms on the wrong sides. RH thread is on the right, LH on the left, which is opposite from the bottom bracket threading. If you switch them around, normal pedaling forces will tend to unscrew the pedals.
 
the pedals are usually labeled R and L, check at the end of the pedal axle for this.. also the pedals should tread into the crank easily most of the way by hand, then require a long wrench to tighten securely.. be sure to grease the pedal threads and crank spindle before installation..
 
I have a pulley puller and so I'll use that to pull off the crank. I'll have to take a look to see if its the L or R...they're identical except for one has the left hand turn threads...
 
FYI just wanted to update the thread...
I took the bike out this am and was able to confirm I have a square hole. I ended up ordering a 175mm square crank arm. Same brand. Hopefully it fits. Lol. I don't think I'll notice the 5mm difference but we shall see. I also ordered a badly needed suspension seatpost too so I'm slowly upgrading my bike. My biggest upgrade this year will probably be a suspension fork on the front and a neaw rear tire...that is if I end up using this bike this year for my work commute.
I've got another thread open in the ebike technical and if I can enable regen this bike is going to be amazing...just saying.

I'm working on another project at the same time...vinyl wrapping my skis! Oh yea...those will be sweet!
 
You want both cranks arms the same length, send it back.
 
For what it's worth, one of the crank arms of my Bafang BBS02 came loose and the square hole was damaged, so I replaced both with a set of very inexpensive unicycle cranks, which were narrower and shorter (making it easier for me to pedal quickly along with the motor).
 
Dumb....ordered the crank arm. Received it today...it's the wrong one. Picture and description says 175mm and square taper. Ends up being a rhombus and 165mm... Thats crap. Sending that one back and already ordered another one thats definitely a 170mm length square taper... Ugh. Well at least I won't be riding anytime soon.
 
Funny story...this entire time I thought I had a trek 80C sport.... The sport part covers some of the last 0 so I just always thought it was a C...well I don't think it is. Lol so I've got a trek 800 Sport. Ha. What's strange is I can hardly find any detailed specs on them. I took out my seatpost thinking I had like a 27 or 27.2 post and ended up finding 29.2 on the stock post. Lol.

I'm hoping a little down the road I can pick up a suspension fork for my bike. I've read all the reasons why not to but there's too many compelling reasons why I need to get one...the ride on a hard front end is too nasty if I'm going to be commuting with this. Even a cheap pair of front shocks will be better
 
I had suspected same, you have a trek 800. You will need to figure out the size of the headset to replace the fork.

It will be either 1" or 1 1/8" . Not tapered.
 
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