Motobecane Sturgis 2018 fit with BBSHD 100mm ?

[pbert]

Hi everyone,

I'm building my first mid-drive e-bike and have narrowed down my bike and motor to the following :

Motobecane Sturgis NX 2018 : http://www.bikesdirect.com/products/...is-nx-1x11.htm

BBSHD 100mm

The big question I am wondering is, will the 100mm fit the Sturgis 2018 ? The chainstay may get in the way some.

I have read a lot and have seen some people saying it may fit, others saying that not.

The reason i want the 100mm BBSHD is because i would like to swap it to a 73mm BB bike in the summer.

Thanks for any inputs.

[max_volt]

This maybe

[pbert]

Awesome, thanks for this. So on page 42 in the comments i found this :

I'm only aware of 3 'announced' MBSB/BBSHD builds so far. 2 of us used 120mm, the other
(Mountaintime) used a 100mm, but recommended that wider would be better. So, pretty
much a consensus, yes.

So i guess I'll be able to fit the 100mm BBSHD but it will be tight and need an offset crank arm. As long as it's possible i'm happy. Thanks!

[AZguy]

I can't speak to the specific frame but I've got a boris the evil brute and managed a 100mm.... barely. Just about two thread of bite on the inner lock ring and not even close to being able to use the outer ring. 3000mi later it's been just fine with some blue loctite on the threads but if I had it to do over the 120mm would have been a much better choice and the pedals would have been more symmetrical too...

[pbert]

AZguy do you know if I were to go with the 120mm model, would I be able to fit the 120mm model on a 73mm bottom bracket bike ? My goal is to be able to swap the motor between the fat bike and a summer commuting bike. I would think the 120mm BBSHD might be way too offset on a 73 mm bottom bracket bike...

[AZguy]

I think with spacers you could but I agree 50mm (~2") is likely too much offset...

20mm offset (or for me it would have been about 17mm) wouldn't be a big deal and in mine it would center the pedals better anyway.

The challenge on the boris was that for the secondary reduction in the BBSHD to clear the chain stay I had to put ~3mm of shims which reduced how much threads I had on the other side. If I had needed even 1/2mm more it wouldn't have fit.

The site shows dimensional drawings for the rear for both bikes and they're definitely different but I can't tell for better or for worse where the secondary interference is. Just beware as it's close.

Maybe someone with experience with that specific frame and the BBSHD can speak...

[pbert]

Yes I saw the schematics on both the sturgis and the boris the brute but would need more time to try and decipher them and see if i am able to determine if the sturgis chainstay will be similar to the boris or if it is larger and then that would definately disqualify that bike from accpeting a 100mm BBSHD. I'll try and spend some time to figure it out. Thanks.

[AZguy]

The interference is only a couple of inches from the crank where the webbing is and the dimensional drawings don't really look like they'll help in that area...

[pbert]

So here are the results (to the best of my ability :) of comparing the Sturgis vs the Boris rear triangle sizes. I took the rear triangle diagrams for both bikes from bikes direct (attached) and then did the following :

- cut the boris image to the lines marked as 197mm and resized the image to actually be 197mm
- cut the sturgis image to teh lines marked as 95 and mirrored so it makes 190mm and then resized it to actually be 190mm
- colored the sturgis from black to red and then made the white transparent and overlayed it on the boris image
- final image attached

So in conclusion it would seem if my super scientific methods applied above are valid that the sturgis rear traingle would in fact have more clearance for the BBSHD 100mm install than the Boris, so i should be ok with the 100mm.

Let me know if you guys think my comparison makes sense.

Thanks.

[AZguy]

The greatest challenge I see with that method is that it would be far more informative if the crank/BB locations were aligned and then scaled vs. working from the axle as a datum.

[pbert]

AZguy yes that would be much better actually. The images on the BD site dont have the BB included though. I could do another version of the overlay with the frames lines up closest to the downtube... or any other suggestions that may give a better comparison ?

[pbert]

I did an overlay based on the 2 little circles on the non-drive side which may be a better point of reference to compare the 2. I lined up the circles to be centered over each other and then shifted the Sturgis over the center line of the Boris. I think this may actually be a much better comparison and it would seem that the 2 frames are very very close in amount of clearance for the BBSHD with the Sturgis maybe even having a tiny amount less clearance. Anyone have a better suggestion or points of reference to use to overlay these images ?

[pbert]

Comparison result from comment #3 above.

[AZguy]

If you are confident you'd like to go with the sturgis frame, since we know it will be fine with 120 but are uncertain about 100, you could purchase the bike and then measure the frame and get the100 if it will fit - someone here would almost certainly make some clearance measurements for you on their BBSHD.

OTOH if the key is a 100mm unit that will go between the two bikes it makes this more difficult since I just don't think you are going to know until you or someone else has the frame in hand.

I think JPLabs has done some sturgis frames although they may not be exactly the same as what you are looking at. Regardless, I think he's used 120mm but he'd know whether 100mm would even be an option on the ones he's done...

[pbert]

Yes my goal is to use the one motor between 2 bikes, one in summer (73mm BB) and one in winter (100mm BB). If the Sturgis wont work with the 100mm then i'll choose something else but i really like the Sturgis NX setup for the price.

[AZguy]

I think it's tough to be certain about a fat-tire frame, especially if it has a really wide set of chainstays. The boris is wide enough to accept 5" tires easily and the rim/tire setup on that sturgis is very simialr (I wish they came with 100mm rims but that's another discussion ;-} ). While the BB size is 100mm on the button, because of the chain stays it pushes the secondary reduction portion out and the 100mm would not be my choice again.

I just can't say about a frame I've got no experience with. I suppose you could get the motor and then purchase the bike and return it if it won't fit by measuring things but what a costly hassle if it doesn't - tough choices. If you actually start putting the motor in you pretty much eliminate the possibility of return so you should be very confident prior to doing any work.

FWIW, buying the boris, my single experience with bikesdirect, was excellent. The bike arrived at the house two days after ordering it! It was in perfect shape and has been an awesome machine. Frame is excellent and the components top notch with the only complaint being that I think they should go with 100mm rims. Price was superb. I know there are others that have complained - it seems mostly from shipping damage however from what I've seen. I measured things and ordered the 100mm BBSHD based on measuring and... well you see how close it was...

[pbert]

AZguy, what year model was your Boris ? And if it is an older model, do you know if the frame geometry has changed from your year to the current one ? Maybe i'll go with a Boris since i would know the 100mm would fit. Thanks.

[AZguy]

Mine is a 2016 but again, I would not recommend it with 100mm - it was way too close. half a turn less on the retaining nut and it would have been a no-go...


OTOH I like the great big step through on the boris and it's one thing that drew me to it over the others with less. Even though I'm 180cm I have a very short inseam (30") and only one leg so the step-through is a primary concern for me. I got the 17" and the triangle is large enough for a shark but just barely!

Since you are looking for something to move from bike to bike and the frames are so opposite... you might just pull the trigger on the sturgis (or whatever) and consider removing metal from the frame if it isn't long enough for the 100mm. it wouldn't take more than 1mm or so but I don't mind saying I would not go down this road - mostly from my ignorance about doing something like that...

[pbert]

Cool, yes the step through does seem nice on the Boris and may save my nuts when riding in snow and stepping/falling off into snow and having foot sink in snow but bike stay afloat.

When you say i could shave metal off the frame, you mean shaving some of the BB off ? I thought about it but would need to look for people who have made videos about doing this. I guess the goal would be to remove some of the metal on the non-drive side to expose more thread ... that would be an experience i would rather avoid :)

[AZguy]

I have another fat-bike that's shorter (the crank is lower) and by all appearances the step through looks very similar. for some reason it's crowded out though and I've fallen so many times on that bike when i have to stop on the "wrong" leg it's silly. That just doesn't happen on the boris...

[JPLabs]

I had to make the same choice for my 2 Sturgis Bullet builds. Medium 17" frames, 2015 or 2016 model, I don't recall. Bought 2 years ago. Supposedly identical frames except color, both from BD but a couple months apart.

I needed some spacers under the drive side on one of my bikes, to prevent contact. Maybe 2 mm. was close. With that, I'm glad I chose the 120mm, or the 'not enough threads' concern would have bit me, I think.

I can't personally and confidently say the 100 will fit. I saw variation between my 2 frames in the critical area, and if exposed threads are minimal, I'd worry about not having enough.

I don't remember where, but seem to recall there are 1-2 Sturgis builds with 100mm that worked out OK, someplace, done after mine.

Running a 120 on a 73mm bike will require the drive side to be where the chainline wants it. So the LH pedal may be way outboard, 47mm further out than the right. Would not feel very good to ride, I think.

I recommend the 120mm if you want to be sure it can fit a Bullet, from what I saw. And I don't think that's much good for a narrow bike, later, sorry.

Buy a 100mm first, try on the Bullet, and if it fits, you are done. Sounds like there's a decent chance it will have enough threads. If not, use it on the skinny one, and buy a 120 kit for the fat bike. You need 2 ebikes anyway :)

[pbert]

Great, thanks for the input. I'll order the Sturgis and attempt to get the 100mm to fit and report back with the results.

[AZguy]

...
Buy a 100mm first, try on the Bullet, and if it fits, you are done. Sounds like there's a decent chance it will have enough threads. If not, use it on the skinny one, and buy a 120 kit for the fat bike. You need 2 ebikes anyway :)

That's exactly what I was thinking... I was afraid to say it though - LOL...

[pbert]

Alright, so i ordered the Sturgis NX this morning. I had to order by phone because Im in Canada and the nice lady on the phone told me i managed to get the last Sturgis NX 17.5 ... just in time i guess. I'm going to go pick it up next week. Once i've attempted to install he 100mm BBSHD i'll give an update with pics.

[AZguy]

I'll bet you get it on - but I'm more risk averse than that =]

[JPLabs]

Me too, I think we are all pretty careful not to promise something will work, when someone else's money and build is on the line. Kudos to pbert for having the fortitude to not care if it's not a sure thing, and just try it. There's a lot of that in building a project, and that's why budgets get blown, and we get cool spare parts. Can't let it stop us.

But some builders only want to try a sure thing, so we are careful to not confuse, with our own examples. Nothing wrong with that, either.

[pbert]

Yup, thanks guys for the input and advice. I agree with being cautious when giving advice and to not guarantee anything that is uncertain. You guys did good, gave as much facts and examples as possible. Each individual is different and the decision to take the risk or not, is based on their personal situation. I'm picking up the motor and bike next weekend. I'll document my build process and provide feedback here after. Thanks again.

[pbert]

Ok its been a while but i received the bike and the motor. I was able to install the motor but had to grind off the front derailleur hanger and even by doing that there were only a few threads left on the non drive side to screw on the final lock nut. All is good though it fits. I'll update the post with pics i took.

My goal was to be able to swap the motor and electricals from my fat bike to my commuter. I built a quick swap system using industrial velcro and tie wraps and im able to remove all the wires and motor and swap it onto the other bike in under 10 minutes. Pretty sweet :) The only thing i had to do was buy a second throttle and leave the throttle on both bikes so that i dont have to remove anything from the handle bars. I'll put some pics of this too.