Trec 810 forks mxus hub

bayrider

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Sep 21, 2013
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Hi everyone have got an issue and that is got a trek 810 mtb which is ideal as the forks are robust and strong steel which made it an ideal choice to use with mxus mottor, I checked it to fit my axle 100mm and it does but found once the hub was fitted on the forks I haven't enough clearance for the upper outer hub where the outer screws are fitted, the forks are wider fatter here then below where they sit, so my question is can I file/grind the sides flush to allow the forks the clearance needed ? I am guessing I need to clear 3mm each side but not for until tightened up. Any advise would be much appreciated I don't at this stage want to look at alternative forks. If not practical or safe to do so how about trying to widen stretch the forks further apart and if this is an option how or best way to do this?

Just researched the frame and this is what it's made of :


chromoly
ˈkrəʊmɒli/
noun
  1. a form of steel containing chromium and molybdenum, used to make strong, lightweight components such as bicycle frames.

Thanks guys
 

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Nealh

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I wouldn't be grinding any thing off the fork legs, forks aren't suitable for using in this case.In my view and from my experience in time or within 500 miles of use the fork dropouts will crack/snap whether or not torque arms are used.
 
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bayrider

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Sep 21, 2013
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I wouldn't be grinding any thing off the fork legs, forks aren't suitable for using in this case.In my view and from my experience in time or within 500 miles of use the fork dropouts will crack/snap whether or not torque arms are used.
Hi thanks for reply I have a carrara bike with same motor steel forks and no issues and no width issues I am aware of torque arms have used on weak framed forks. With this trec bike I put a magnet on the forks and it took to them so I know the forks are suitable for the motor hub ..... so would I be ok trying to widen if possible and if so how? or likewise file or carefully grind each inner side of the forks.
 

Nealh

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If steel then no real issue with D/O as they look plenty thick but I still wouldn't go down the road of grinding off any of the forks thickness. Ideally you need a set of forks the same as the Carrera.
 

bayrider

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If steel then no real issue with D/O as they look plenty thick but I still wouldn't go down the road of grinding off any of the forks thickness. Ideally you need a set of forks the same as the Carrera.
Thanks might have to look at the forks option failing that anyway over time of widening / stretching apart say with a wooden block or anything? if this fails as it's light might just ride as a normal bike
 
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Deleted member 4366

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They're not steel forks. the bottom , where the drop-outs are, is cast with the main part. you can't do that with steel. steel dorks have welded on drop-outs or they smash the steel tube flat.

To solve your problem, you need new forks with inboard drop-outs or a new motor.
 

bayrider

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Sep 21, 2013
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They're not steel forks. the bottom , where the drop-outs are, is cast with the main part. you can't do that with steel. steel dorks have welded on drop-outs or they smash the steel tube flat.

To solve your problem, you need new forks with inboard drop-outs or a new motor.
oh thanks for that I might well just ride it as a normal mtb as it's very light without hub gutted wanted this to work out but that said cost 70 so not too bad I guess could get forks but would need them affordable to make the project worthwhile
 

bayrider

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So you wouldn't advise then even if I where to get a torque arm fitted for added strength, filling down each side to height of hub till totally clear of rubbing both sides on the forks then?
 
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Deleted member 4366

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They're hollow. How much can you file them before the inside is on the outside?
 

Woosh

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strange case.
can you post a picture of your motor?
 

bayrider

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They're hollow. How much can you file them before the inside is on the outside?
Sent Trek an email if they can advise the thickness of the tube. It's kind of ironic but seem to have plenty of play with the rear axle but hope not being stupid here, but would the front e hub fit on the rear or is it all completely different ball game and if so how ?
 
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Woosh

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you can't use a front hub motor at the rear.
If my memory is correct, the two anti torque washers are inside the fork.
How are the AR washers on your wheel?
 

Woosh

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Try placing the 1mm thick normal washers between the motor and the AR washers, they may help to clear the motor from touching the inside of the fork.
 

bayrider

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Try placing the 1mm thick normal washers between the motor and the AR washers, they may help to clear the motor from touching the inside of the fork.
It seems when lining up the flat part of the axle to the forks when bike is upside down that it sits in the D/O but need to apply pressure to fully mount it then the motor casing is somewhat wedged no room either side for maneuver the forks are rigid was considering if possible filling down both sides of the lower part of the forks to allow some space chromoly seems to be the said material used for this make of trek bike
 

Woosh

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it may be worth your while replacing the fork.
This problem is virtually eliminated on all recent suspension forks.
 

PC2017

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I will try to briefly resurrect this thread... The trouble is I checked the forum for the word "chromoly" before I posted, I was trying to be good and do my own research.

Just for reference I have run similar forks to these(above) with a front motor and t-arm for several thousand miles however the suspension seized up years ago(cheapo forks) and now it's time to replace them and since I have a fantastic NCX seatpost I do not require spenny forks and before supply lines dry up, capitalism falls and the whole world crumbles I should be getting some fitted this week.

Question to OP, from memory was the bike frame Chromoly and NOT the suspension? Did you ever magnet test the dropouts? I would agree that those forks are not steel.

Did you ever get some steel forks?

Confirmation required: to anyone - If as mentioned in Deleted members post above, that steel forks dropouts are welded or hammered out one assumes that the magnet test on the dropouts would in fact prove steel or no steel on forks labelled as chromoly would this be correct?
 

Nealh

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Bit of an old thread for which the op hasn't posted again since summer 2019 so likely has moved on.
Cromoly forks will be magnetic in it's entirety, a mix of chrome/ molybdenum so iron/carbon is in the material.
For push bike forks 4130 Cromoly is often used, If one is in doubt about then the magnet test is the best option.
 
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