Motor for 130 mm rear drop outs

[Nealh]

It is simple hubs are built for 70mm - 100mm front forks, and typically 135 for std rear drop outs.
If one thinks 5mm is to much to spring a 135 hub in to a dropout by hand then better buy a different frame that needs no strecthing.

 

[saneagle]

The terminology is certainly confusing if 135mm motor IS for 130mm drop-outs.
Post 7 (https://www.pedelecs.co.uk/forum/threads/motor-for-130-mm-rear-drop-outs.46586/#post-700689)
suggests O.P. can get away with 135 on his 131 titanium hub; that is great, and makes most of the thread after post 7 irrelevant to the original question.

However, that post makes it look as if a smaller difference (140/137) would not work easily on his alu Canondale. Would you say '140mm motor IS for 135mm drop-outs'? Would an 135 wheel fit easily into an 130 stiff alu frame?

O.P. was in the lucky position of having an appropriate wheel around and being able actually to do it (or at least, actually test it) as you suggest. Most people wouldn't be.

You get a piece of wood, cut it to 135mm, 142mm or whatever you want, and stick it between your drop-outs, then you know whether your motor will fit.

I have never found a motor that wouldn't fit the frame I had intended it for. That includes 100mm motors for Brompton and other 74mm forks, 150mm Xiongda motors and many more, though I can understand that a 150mm motor is unlikely to fit 135mm drop-outs on a bike with 20" or smaller wheels. The wood test would confirm that.

If you haven't got a bit of wood, go find a tree and break off a branch about 25mm dia. If you haven't got a saw, use a sharp knife. There are no excuses now.

 

[Bikes4two]

My oldest bike, (early 2000s), a non disc road bike, has an alu frame and as measured the OLN is 130mm.

I needed to replace a spoke and tru up the wheel and as an interim measure fitted a spare wheel whose OLN was 135mm - it was a struggle (for me at least) to get it into the dropouts and not wanting to have the same struggle dealing with a roadside repair, I got the original wheel fixed and back into place promptly.

If like the OP I were looking to fit a rear hub motor to that bike, then I would be concerned at using a 135mm motor from the tight fit point of view.

I wouldn't attempt to spring alu forks, so as suggested by @Nealh, I'd need to consider a different frame.

Fortunately for me, I was give a tsdz2 to put on that bike.

 

[saneagle]

My oldest bike, (early 2000s), a non disc road bike, has an alu frame and as measured the OLN is 130mm.

I needed to replace a spoke and tru up the wheel and as an interim measure fitted a spare wheel whose OLN was 135mm - it was a struggle (for me at least) to get it into the dropouts and not wanting to have the same struggle dealing with a roadside repair, I got the original wheel fixed and back into place promptly.

If like the OP I were looking to fit a rear hub motor to that bike, then I would be concerned at using a 135mm motor from the tight fit point of view.

I wouldn't attempt to spring alu forks, so as suggested by @Nealh, I'd need to consider a different frame.

Fortunately for me, I was give a tsdz2 to put on that bike.
View attachment 55969

OK, so you have no experience and wouldn’t know how to do it. Surely, best not to comment in that case.

 

[Nealh]

Aluminium can be sprung but ideally one would only want to do it once .

 

[Bikes4two]

• @Babsbike - as you can see, your post has given rise to different points of view regarding fitting a 135mm hub motor into a 130mm OLN frame with some saying it's fine and others not.
• On the Cycling UK forum back in Oct'23 there was a long post on springing or 'cold setting' a frame from 126mm to 130mm, but this was with steel frames. Again, a diversity of opinion (link) which you might like to read to get a wider view of the subject and differing viewpoints.
• I've asked the question about cold setting titanium (and aluminium) - I'll leave it to you to choose whether to read the views of others, let alone heed any particular advice where there doesn't seem to be one definitive answer?

 

[saneagle]

• @Babsbike - as you can see, your post has given rise to different points of view regarding fitting a 135mm hub motor into a 130mm OLN frame with some saying it's fine and others not.
• On the Cycling UK forum back in Oct'23 there was a long post on springing or 'cold setting' a frame from 126mm to 130mm, but this was with steel frames. Again, a diversity of opinion (link) which you might like to read to get a wider view of the subject and differing viewpoints.
• I've asked the question about cold setting titanium (and aluminium) - I'll leave it to you to choose whether to read the views of others, let alone heed any particular advice where there doesn't seem to be one definitive answer?

Many of the comments in that thread were from people, who didn't have a clue. Like Bikes4two, they'd never actually done it and had no relevant experience. They just made up false theory and stated it as if it were fact, or they used irrelevant or out of context information that they didn't fully understand. It would be best if those guys stayed out of things that they don't know about.

There have been many thousands of bikes converted by all sorts of amateurs, many of them completely ham-fisted, but I challenge anyone to find a single example of a frame that broke because a motor was fitted. You can find plenty of high-price EMTBs that got broken frames because of their rough use and design faults, a few folding bikes that broke in the middle because they were not designed for the impulse loads of to the much higher speed and a few cracked seat-posts because of poor design, but that's it.

 

[Bikes4two]

Many of the comments in that thread were from people, who didn't have a clue. Like Bikes4two, they'd never actually done it and had no relevant experience.

How wrong you are about that - you don't know me at all and it is damned rude of you to assume I haven't a clue - what is it with you and belittling people - I have nothing to prove but you it seems, do.

I said I'd not want to cold set an alu frame and I wouldn't - that just my opinion - I'm not stating it as a hard rule.

I have cold set two steel (531 tubing) rear forks and then rest the drop-outs, both with great success.

 

[saneagle]

How wrong you are about that - you don't know me at all and it is damned rude of you to assume I haven't a clue - what is it with you and belittling people - I have nothing to prove but you it seems, do.

I said I'd not want to cold set an alu frame and I wouldn't - that just my opinion - I'm not stating it as a hard rule.

I have cold set two steel (531 tubing) rear forks and then rest the drop-outs, both with great success.

Yeah, yeah yeah, and then you woke up.

 

[FastFreddy2]

How wrong you are about that - you don't know me at all and it is damned rude of you to assume I haven't a clue - what is it with you and belittling people - I have nothing to prove but you it seems, do.

You are right about rudeness, and I would add arrogance. There are many people here who are willing to help, and one or two who want to bathe in their own self-glory.

In my view, an individual who seeks to belittle someone asking for advice, is a bully. It seems you may have stumbled across one.

Just because you can force a wider hub into rear stays, doesn't mean you should. The bend/shape/profile, together with size/diameter of the stays should be considered, and of course, the use the bike will be put to. Making a claim there is no risk to this, suggests the person making that claim has spent a good deal of time running various stress analyses on the frames of the hundreds of shapes the stays might have on thousands of bike designs...... Which on the face of it, does seem a bit unlikely.

And when someone says to me "you're the first to complain" or "no one else has that problem", I would now just point them at a software package known as Horizon, and the 800+ Post Office staff wrongly convicted of theft from a company that swore in court, their software was infallible. Just because damaged frames through spreading rear stays isn't well known, doesn't mean it can't happen. Who wants to be the first anyway, right?

Titanium frames aren't cheap. Typically, the frames are thin tube and very lightweight. That said, they are known to be fairly forgiving.

In your place, I would get in touch with a reputable supplier, and I can highly recommend Woosh. Ask what width exactly is required for an easy fit of a rear hub motor. 130/135/138mm? When you have that confirmed, trial fit some dowel/chair leg/firewood cut to the right size and see/gauge for yourself how much stress the additional spread (if there is any) feels like to you. That was a good suggestion.

This test will cost a few minutes with a saw, and get you feeling comfortable or not, about a conversion.

If you feel like the stay spread might be too much, then either bin the idea altogether, or buy a cheap donor bike off an auction site to convert instead?

Do come back with your findings.

 

[Sturmey]

Can I make a distinction here between 'springing' open the frame wider by an extra 5mm to fit a wider hub, and 'spreading' or permanently cold setting/spreading the chain stays wider.
I have on occasions fitted wider 135 mm hubs on to 130mm wide chainstays by springing them apart, although it does make fitting the wheel slightly more difficult. I am sure in this case there is little risk as the chainstays return to their normal 130mm when wheel is removed.

I have also on occasions permanently 'spread' the chain stays on older cheap bikes using whatevers at hand. (threaded rod or car scissors jack). I have seen the paint crack at the seat stay bridge and at the chain wheel dimple (on one occasion)after spreading. I can understand peoples reluctance to do this with expensive frames with special tubing.