Front forks too narrow... Now what?

[Skunkwise]

So I ordered the front geared hub motor kit from E-bikekit.com. Having seen a number of folding bikes closely related to mine (Tern/Dahon) with the same set-up, I didn't bother doing any pre-measuring before purchasing. My front forks are not the 100mm they should be, theyre at about 75-76mm. They pass the magnet test so they are not alluminum. Can I stretch them out to 100mm and jam the motor in? Or is that way too much?

Stupid is as stupid does I suppose...

Thanks in advance for any help.

 

[Kin]

"They pass the magnet test so they are not aluminum."

To clarify- you mean that a magnet sticks to them? Because Aluminum isn't ferrous, so a magnet won't stick.

It's unclear to me whether you're using a Tern/Dahon or whether those bikes are the similar ones you looked at.

Stretching from 75-76mm strikes me as a large amount, esp for a folder with small arms. Maybe someone who has actually widened their forks could give real feedback though.

 

[Skunkwise]

"They pass the magnet test so they are not aluminum."

To clarify- you mean that a magnet sticks to them? Because Aluminum isn't ferrous, so a magnet won't stick.

It's unclear to me whether you're using a Tern/Dahon or whether those bikes are the similar ones you looked at.

Stretching from 75-76mm strikes me as a large amount, esp for a folder with small arms. Maybe someone who has actually widened their forks could give real feedback though.

The magnet sticks, so yes, they are not aluminum.

My bike is a Tern.

With putting rags over the dropouts (so to not scratch the motor) I can get it pretty close by just pulling them apart with my hands. Just not sure how unsafe it is.

 

[Skunkwise]

Uh, ok new question... I got it to fit, am I gonna die?

 

[Skunkwise]

I've decided against trying to cram it in. I had it nearly in, and could've forced it, but decided no to. I have no idea what type of chain reaction it'll cause with my brake mounts and what not. I'm just gonna see what my options are about returning it for a rear kit tomorrow.

 

[d8veh]

I've seen Brompton steel forks stretched to 100mm. I don't see a problem with steel. You can use a threaded bar and two nuts to jack the drop-outs apart past the elastic limit to get them to stay 100mm for easy wheel removal.

 

[Racer_X]

The threaded bar and two nuts to jack the drop-outs apart past the elastic limit to get them to stay 100mm for easy wheel removal.

This is the best solution to stretch front forks and even back drop outs.

Go through the site and search for "threaded bar" and you will get some pictures on how to do it.

One word of importance when you do this. You must stretch both sides equally, otherwise you going to have problems. So you might want to go 7mm on one side and 7mm on the other side and it should work.
Good luck, you will be fine.

 

[winkinatcha]

being kinda interested in this I did the search n came up empty.. I then searched on "spreading" and with about 70 results found this thread...

http://endless-sphere.com/forums/viewtopic.php?f=3&t=38632&p=563977&hilit=spreading#p563977

this is primarily talking about the rear dropouts but does detail the threaded rod method

vis..
find a threaded rod (IE a steel rod that has a thread its entire length) that will fit inside the dropouts.
using two nuts and two washers, thread the nuts onto the rod so that the nuts fit INSIDE the dropouts, with a washer between the nut and the drop out

Using a wrench turn the nuts so that thay apply pressure on the inside of the drop outs, and continue turning 'til the desired widening has been acheived....

Now the word "threading" after so many iterations.. looks like a nonsense word :lol:

joe

 

[Kin]

oh, you want to use google and not the search engine. The ES search engine is only useful if...I don't know, there are a few minor cases. Usually not useful.

"site:endless-sphere.com threaded rod"
https://www.google.com/search?q=site%3Aendless-sphere.com+threaded+rod&sugexp=chrome,mod=13&sourceid=chrome&ie=UTF-8

Second link:

http://endless-sphere.com/forums/viewtopic.php?f=3&t=38632

 

[winkinatcha]

Ahh Thanks Kin... clears it all up.. Cheers

 

[d8veh]

You'll have to go further than 100mm when you spread them because they'll spring back. Steel has an elastic limit, which if you go beyond, you get permanent change. It'll probably take a few iterations to get it right.

 

[amberwolf]

BTW, for the threaded rod, you can just use an old hub's axle. Then you also already have the nuts and washers.


As for stretching a fork out 12.5mm on each side, that sounds like a lot, to me. However, I've squeezed in rear stays on my CrazyBike2 probably that far (to turn my front 9C into a rear) with no effect on them (yet). I haven't stretched a front non-suspension fork out that much yet, but if it's well-made and you're not putting all the stress on questionable welds like on a wallyworld bike it might be ok.

 

[Skunkwise]

As for stretching a fork out 12.5mm on each side, that sounds like a lot, to me.

Ha, coming from you Wolf, this statement alone is enough for me to pass on the whole idea.
I just ordered the rear hub motor as an exchange. They said I might have to throw a few bucks at a new motor cover because I scratched it up pretty good already. Other than that I'll have my new motor next week. One of the benefits of going with a local tried and tested supplier I suppose.
I'll try the old hubs axle trick on this one as my rear measures 133mm and the motors is 135mm. 1mm each way is a far cry from 12.5, so I'm much more comfortable with this amount of surgery.

Looking at my front forks now, I noticed that the actual dropout must be made of a softer metal because the tips of them now curl outward if you're standing on the forward end of the bike looking aft, kinda like elf shoes for lack of a better descriptor. I can supply pictures if necessary. Is this a problem?

 

[winkinatcha]

Nahh Skunkwise that's a design feature, called "lawyer lips" or some such, designed to help hold those spindle things for quick release wheels, and a bastard to get around when applying torque plates n washers n such when fitting... Go the rear wheel!

Joe

 

[winkinatcha]

BTW, for the threaded rod, you can just use an old hub's axle. Then you also already have the nuts and washers.

I know we all know it, but I am gonna say it... AmberWolf, yer a bloody genius

Joe

 

[chvidgov.bc.ca]

Another solution is the Crystalyte 209 front motor, works well on the narrow front forks of folders. I've got a Dahon folder (about 80 mm front spacing), and its a nice speedy motor on that bike.