fitting rear motor kit to 135mm spacing

[emzed]

I have bought a rear hub motor and found (as I suspect many before me) that it won't fit my bike. I have 135mm spacing and the hub motor is closer to 160mm. How have other gone about fitting it to there bikes?
Also, there are two steel tube/bushes (one on each side) which are loose and just seem to sit there. Are they supposed to be loose? Are they just there to take the load when tightening the axle nuts?

I need to get some width down on my wheel. Maybe I can machine off the thread on the brake side as I won't need it. Might also need to consider a smaller gear cluster... 

[Dave]

I just ordered a rear hub kit yesterday, and have been wondering about fit as well. It's possible to spread the dropouts a bit (see http://www.sheldonbrown.com/frame-spacing.html for tips on that) on steel frames (don't do it on aluminum), but I'm thinking that it would be better to narrow the hub if possible, even if only a little.

Any chance you can snap some close-up photos of both sides of the hub?

[emzed]

Hi Dave,

yeah, I will take some snaps when I get home.

I think I may have to go down a similar path to this (see step 5) http://www.users.bigpond.com/solarbbq/GL1.htm

Matt

[myelectricbike]

There are differences in the rear hub cover widths at the axle depending on whether they include a gear or band break thread extension. The difference is 15mm. So in theory it seems you could reduce the overall spacing by replacing the band break hub cover with a front wheel cover. Unfortunately...

The rear axle is 222mm long. The flats are 35mm on the gear side and 45mm on the band break/wire exit side so that the absolute minimum spacing is 142mm - 2 mm more than the recommended coldset maximum, even if you replace the band break cover with a front wheel cover and use a 3 gear sprocket to access the full flat length.

So why not use a 3 gear sprocket and cheat? Its only 2mm! My instructions are: never speed and never cheat!  Suppose the wife says, but honey I was only in bed with him for 2 minutes  - okay bad example never mind.  Try this, but officer I was only going 2 miles over the speed limit, can you give me a break?

[Dave]

There are differences in the rear hub cover widths at the axle depending on whether they include a gear or band break thread extension. The difference is 15mm. So in theory it seems you could reduce the overall spacing by replacing the band break hub cover with a front wheel cover. Unfortunately...

The rear axle is 222mm long. The flats are 35mm on the gear side and 45mm on the band break/wire exit side so that the absolute minimum spacing is 142mm - 2 mm more than the recommended coldset maximum, even if you replace the band break cover with a front wheel cover and use a 3 gear sprocket to access the full flat length.

Most modern mountain bike frames (with 7 or 8 speed clusters) have 135mm spacing. I've measured all the bikes in my stable, and only the eldest (a 25~ year old Trek) has less than that. And if the flat length is an issue, grinding is a possible remedy, as shown in the link that Matt provided.

So why not use a 3 gear sprocket and cheat? Its only 2mm! My instructions are: never speed and never cheat!  Suppose the wife says, but honey I was only in bed with him for 2 minutes  - okay bad example never mind.  Try this, but officer I was only going 2 miles over the speed limit, can you give me a break?

It's not cheating. It's taking what's available and creatively modifying it to be used on alternative hardware. AKA hacking; a practice that's been around for millennia. And please, when referring to a device used to slow or stop a vehicle, the word is "brake", not "break". They sound the same but they don't mean the same. I hate to play the grammar cop, but I will. And don't expect too many breaks from me.

[myelectricbike]

A. Forums are not the place for grammar cops. B. I rarely ever check the correctness of my speller. C. Grammar is also far more sophisticated than either grammar cops, spellers or grammar checkers can handle. Case in point: passive voice is critical to advanced English, French and most languages to give the reader an opportunity to relax and consider with greater emphasis whatever else is being said, just as intensity has a critical role in music. I haven't even gotten into play on words, etc. as reasons why a grammar cop on a forum is a very bad thing. I suggest that if you want to be a grammar cop that you study language, context and venue first before handing out tickets to others.


If the coldset is 10mm or less then obviously you are within the recommended 10mm limit and there is no cheating, whether this is accomplished by either grinding back the flats or using a frame with a rear triangle axle spacing that is already great enough to permit a coldset of 10mm or less. There are also special gages and tools designed to overcome the problem of out of parallel dropouts resulting from exceeding the recommended coldset limits. These tools and gages are not cheap and are designed for the advanced bicycle mechanic. Armatures  (...don't you mean amatures...? Yes, Dear...  ) should therefore conform to the recommended limits as advised. 

Bicycle Frame/Hub Spacing

[emzed]

Don't you mean amateur?

Dave, here are some photos. The first one is a bit dark but you get the idea. As a previous poster mentioned, the axle is ~222mm long with 35mm flats on the cluster side, 45mm on the other.

[emzed]

This shows the brake side with spacer tube and removed for clarity. As I don't need the brake side, I was thinking of cutting a bit of the thread off, extending the flats and reducing the length of the spacer tube. That should give me ~10mm.

I am also thinking of taking the wheel to my local bike shop to get them to dish it a little to help cancel out the offset created by the modification...

[emzed]

Here are a couple more. The first shows the brake side with the tube removed. Thats where I will probably extend the flats. The second shows how the 5 speed cluster that came with my wheel extends over the end of the flats. In fact, the cluster ends about 26mm from the end of the axle. So I might also see if I can get an thinner cluster (ie less gears).

[myelectricbike]

I've said it before and I'll say it again.. I hate spellers! ...especially those with grammar checkers Most likely.

If you drop three gears and grind the flats back 2mm you should then have 140mm spacing to coldset a 130mm rear triangle by 10mm.  If you have a rear triangle with 135mm then you can skip the grinding. One gear is all you need to be legal but two is better;  one for up hill and one for top speed.

[Dave]

Matt:

Wow! Thanks for the photos; really helps a lot having a good look at the thing. That ought to be something provided by Golden, wouldn't you agree (Philip, are you listening?)

What is up with that huge gap between the freewheel and hub? There's got to be 10-15mm between them... totally unnecessary. I wonder if that's there because the freewheel threads are too long? Like the unit depicted in the link you posted on 8-10; he cut a number of threads off the freewheel side first. Not too tough there. And I see no future where a brake would be put on the left side, so that might as well go also. Looks like the wheel will need to be dished to center it.

I guess it's pretty obvious that this hub was designed for something totally different than being used on a standard bike.

And thanks again for posting the photos.

[emzed]

Yeah, quite a bit can be taken off the brake side. My only concern is how close the hub motor will then come to the frame (the guy that did the mods on the link I posted previously got the motor pretty close to the frame!)
I think the gap between the cluster and hub is where the bearing are mounted internally.

I found this on spoking wheels and it covers dishing a little. http://www.sheldonbrown.com/wheelbuild.html
I'm not experienced enough to dish my own wheel so I think I might take it to my local bike shop and have them do it. May even look at replacing the rim with something a little better...

[emzed]

I figure I might as well turn this thread into a build log...

I have taken the cluster off temporarily. This left me with a width of ~142mm which dropped in quite easily into my frame as I held it open. I did this so I could see how much room I have on the brake side. As you can see from the second photo, I could easily have the hub move over 15mm and still clear the frame. It just depends on how much I can dish the rear wheel.

Does anyone know how much you can dish a wheel?

[myelectricbike]

For starts I'd check out the spoke length calculators on Sheldon's wheelbuilding page and his dishstick note. Even though the spokes you have to work with are short there is plenty of thread to work with. Don't think you'll have any problem.

[macbeth]

Traditionally a Dished Wheel will have 18 spokes on the Right Side Straight and Vertical and essentially your entire weight is now dependent up the strength and rigidity of those 18 spokes, the Left side of the wheel will see the 18 spokes at angle up to 30 degrees and these spokes will be loose and not load bearing.

You MUST carry a spoke key (wrench) and ensure your Right spokes are always tight or your wheel can Taco or at best go out of alignment.

I have not yet seen a Golden Motor but if it is as wide as I am reading in this Forum, then a 3 speed or even a one speed Freewheel sounds healthier. Spreading your rear triangle will mess up brake alignment. A Hub Motor kinda replaces the need for a lot of those gears anyway. Always nice for bragging rights to say you have a 9 speed bike, (I have a SRAM dual drive 9 speed btw) but once the Motor goes on at best you might use 2 or 3 of the 9, so why bother keeping the whole cluster.