BMC Hub Motor - customer support - stripped threads

I did buy a BMC V2 motor recently thinking it had to be a high quality product since it wasn't exactly cheap. To my surprise BMC didn't provide any manual or installation instructions so before I mounted the wheel onto my bike I read some threads here about problems with Chrystalite axles. I used a torque wrench and tried to be careful not to apply more torque than posts here recommended for Chrystalite. Still the threads got stripped on one side of the axle and so much that they are beyond repair and I have either to replace the axle or get a new motor.

Then I encountered the probably worst case of customer support that I have seen. Before I installed a new axle I needed manufacturers recommended torque data. My dealer has been great to deal with but he couldn't get the specific data I wanted so starting a few weeks ago I tried to contact Mr. Vanjani at BMC USA by e-mail three times. When BMC persisted in refusing to respond to my e-mails with my question I finally had to call BMC and Mr. Vanjani promised to respond by e-mail the following day. That never happened so I followed up with another e-mail reminding him about his promise but he didn't respond to that either.

I understand that BMC motors are now manufactured in China but to what extent this may have an impact on QC and steel quality I don't know. Still it seems that BMC wants to keep torque information a secret. Before I decide whether to stick to BMC or get another brand for my motor replacement I want to hear from people with a similar experience or with thoughts on the torque matter.

you likely only stripped part of the threads, add washers so the axle nut is on a different part with good threads..

i've never bothered with a torque wrench.. just crank them down real good or as much as i dare and ride on !.

I have a torque arm on that side plus extra spacer for torque arm alignment so I only have an extra few turns of thread. Besides torque data is normally provided by the manufacturers of bike equipment, at least upon request.

welcome to the ebike industry standard ! 8)

Yes Vanjani is a complete DICK and will only sell to you. Customer service from BMC no chance as he is a DICK. I called him for a keyway as he said he has a hole bag. After many e-mails and messges - ZERO. For help with BMC ask Ilia at http://www.ebikessf.com. Did I say Vanjani in India is same as DICK . I will take my shoe off to throw at him.

Back on point the axle on a bmc hub is very to get out so be careful. Not it may even be swegded in so to speak.

Yes BMC USA's customer support sucks. I never got any response from them either and that's also the reason I switched from BMC motor to MAC. Two different companies but their motors are virtually identical and the MAC is a lot cheaper and has great customer support.

besides adding washers to get the nut out to where there are good threads, consider the nut is too loose and a new nut with better and tighter threads may help. chase the threads with a thread die of the right size and pitch.

i feel that the threaded couplings are the best bet since they have such long threads they can provide a lot of support spread out over many more threads than just a short nut. tighten with a pipe wrench or maybe you can find a metric threaded coupling of the right size with flats on the outside that will accept a wrench.

if you do find one, post it up because a lotta people would be interested.

A long hex shaped coupling nut sounds like a great idea. I will try that. Do you know the thread standard, pitch and diameter for this particular thread?

nope, and that is the critical info. along with finding a source for such an unusual coupling too if it is metric. but it may be out there, just a minimum order of 5,000. hehe

Hm, they're made in China now? geez. Now they're really not worth the extra cash.

You can get replacement parts from a few domestic sources though; ebikessf, lyen, and it's electric/power in motion should be able to help you out;

http://us.itselectric.ca/
http://lyen.com/
http://ebikessf.com/

You mentioned "your dealer" so it sounds like you did not buy this directly from BMC. The dealer may be able to send it back and it will be replaced if warrented. He can just tell Chandu that it was stripped out of the foam box. Mr Vanjani, (Chandu) does not want to deal with a lot of questions from the public. That's why he imports and sells through dealers. A split lock washer should hold the nut on from backing off. A second thin nut can be used to jam lock the first nut. Metric threads are so fine and the big nut is sloppy to begin with. Try to find a smaller nut and die (English) coarse thread to repair the one side. Torque specs are found online but I would not use them unless for a perfect match of threads (no slop). You can go with a MAC but put your V4 clutch into it if you got the latest in your BMC. I can't stand the noise in my old clutch, green gear BMC motor.

Looking at the drawings on BMC's website it is clear that the axle thread is M14-1.5 Fine. The ANSI tolerance standard for this thread is among other things an overall diameter between 13.73-13.97 mm. I measured my axle at various points with a high precision caliper and the average diameter was just below the standard range. Combine this axle with a sloppy nut with an inner diameter above standard (5% difference) and soft axle steel and threads are easily getting stripped even with moderate torque. 5% is a lot and I don't know what tolerance limits BMC has but it seems to me this axle/nut combination may have slipped through BMC's quality control.

The reason I contacted BMC was that BMC's website invites questions related to their products, but little did I know. I am now working with my dealer (Ilia Brouk) on this issue, he is great and very helpful and does his best to assist me.

Regarding the hex coupling nut it seems easy to find M14-2 Coarse but for M14-1.5 Fine I have only found sources in China where you can buy these in bulk.

CogHog:

You wrote:

"Torque specs are found online but I would not use them unless for a perfect match of threads (no slop). You can go with a MAC but put your V4 clutch into it if you got the latest in your BMC. I can't stand the noise in my old clutch, green gear BMC motor."

Can you please guide me as to where I can find the BMC specific recommended torque data? They are certainly not on their website.

If you are careful and attentive, you may be able to die cut the threads on the damaged end of the axle to M12x1.50, and use a 12mm nut on that end. You can leave the wider flats where the axle passes through the torque arm, and then use a washer or two to fill in the transitional area between M14x1.50 and M12x1.50.

I have long assumed I'd be doing something along those lines when the crummy threads on my X5305 eventually strip out. I might be fastidious enough about it to get an M13x1.50 die as well, and pilot it onto the damaged threads first.

Chalo

Seems someone was searching,

http://answers.yahoo.com/question/index?qid=20090825113740AANJWAh

http://www.brightonbest.com/catalog/UK/Socket_Screws_Metric.pdf

You must understand that the load on the axle is Vertical and the nut is just to pinch it to the fork. I tightened mine by hand and last week someone noticed it coming loose even though I have a split lock washer. I would say it does not need to be 70 ft lbs of torque but secured to keep it from spinning off. The constant beating of the sides of an aluminum fork can result in a lose of space from the initial tightening. As my nut came lose. Loctite, Lockwire, Castle nut, Jam nut.
I have a v3 motor that I had the machine shop here drill a second hole down the middle of the other axel to play with bigger wires (for sale needs a new magnet can) and they had a very slow and hard time as it was hardened the whole length. The newer made in China ones I have no idea what is going on there but I will ask my bud who is working at BMC/PPL.

A good nut for these are automotive lugnuts that are available in the fine thread pitch (1.5mm). The ones I found are about a buck a pop and are 21mm long which gives about 80% more gripping area and of course there's more area to put loc-tite on.

Gregor said:

A good nut for these are automotive lugnuts that are available in the fine thread pitch (1.5mm). The ones I found are about a buck a pop and are 21mm long which gives about 80% more gripping area and of course there's more area to put loc-tite on.

Click to expand...

Yes, I use these also as my standard fitment the past few years.

They are better cut threads, and much longer than the "hand-shake-fit" whimpy nuts we get with our motors.

I think the problem is they don't throw away the die when woreout. It doesn't have a size.

As Ypedal said "welcome to the ebike industry standard" That is to say no standard at all. You need to be careful with these things. I have as yet in my 4 new motors only had nuts that fit flush and semi tight on the axle threads once. Probly the dealer I purchased the wheel from already replaced them. Other nuts were so sloppy I would not even think of using them to hold anything of mine. So went to the local hardware store and picked up something that fit much better. My GM nuts were not even drilled at 90 deg to the face of the nut so it would spin on like wobbly weebles having a bad day. At least the axles were threaded and machined decent. I have been unhappy with all 3 of the axles on my BMC motors none have been even close to my standard and on a 1-10 rating, even the best of them, would not get past a 4 or 5. It is up to us to pay attention to what we build as our lives depend on it. I have seen several posts here that may help you out I wish you luck in your pursuit with imperfection. :lol:

I don't have to worry about stripping the axle threads on my BMC motor anymore. I think I have found a solution that protects my axle threads, no matter how much torque I use on the nut (within reason). I use a threaded insert and a M20-1.5 nut (Insert Internal thread: M14-1.5, External thread: M20-1.5, Length: 20 mm). Rather than using it for its intended purpose as an insert in a hole to create or protect internal threads I use it in reverse by protecting the axle threads.

I start by tightening the insert with my fingers until it feels tight. Then I screw the M20 nut on top of it which I can tighten as much as I wish. No more wear and grinding on the original threads. Since the axle has only a small area of threads at the top and bottom of the axle, one more advantage is that now the larger nut has 4 times as much thread area to grab on to which makes it much less prone to stripping, so whether the nut is sloppy or not doesn't matter very much anymore.

One other advantage is that the insert is made of harder steel than the axle. I tested this method on the opposite side of the axle I accidentally stripped and just for testing purposes applied an overkill of 10 times as much torque than I used when I accidentally stripped the original axle threads. The motor axle threads didn't show any sign of wear whatsoever. And best of all, if I for whatever reason damage the insert then I can easily replace it at low cost - No more need for shipping the motor back to the supplier for an expensive replacement.

Hey tkollen!
That is clever! Doyou use loctite to hold the threaded insert in place before the nut is tightened?
otherDoc

No need for any Loctite or similar. By tightening the nut the insert is also automatically tightened as well by being pressured onto the outside wall of the axle thread.

A torgue arm also please.

Found this thread(!) after stripping part of the thread on the axle of my BMC V2-T just the other day.

As background, I am running Dr. Bass torque plates on a Giant Trance and recently installed the Ezee wire protector (http://www.ebikes.ca/store/ezee_manual_V20.pdf) to finally protect the wires where they come out of the axle. All good, but as a result there is very little thread left to work with on both sides, and especially the wire side.

The part of the thread that stripped was far out enough that removing the Ezee wire protector exposed enough thread again to secure the nut. But now I don't have the protection for the wire. I could take the washer off, try to put the wire protector on again, but am afraid of stripping any more of the thread.

I am glad there is a solution with the insert and a larger nut and will try to pick this up in my local hardware store at the earliest - assuming it is something fairly standard I can find there?