2020 Schwinn Axum 29'er

[Dshue]

Today I got started on my 2nd build.
It's a 2020 Schwinn Axum 29'er. It's a $400 Walmart bike. It comes with a 1x8 drive train with an 11-40 cassette, a spring fork with no rebound damper and a mechanical lock out with 100mm travel. It's a large frame with a 19" seat tube, 31.8mm bars 720mm long, a long 30.9mm seat post, it has a straight steerer tube but the frame readily accepts tapered head set and has a 67.8° head tube angle. 100mm front axle and 135mm rear. The rear can be converted to 142 "boost". Mechanical disc brakes that work exceptionally well, 160mm rotor rear, 180mm rotor front.
29" wheels with 35mm inside width rims and 2.6" tires. The wheels (but not factory tires)can be set up tubeless.
Bottom bracket width is 73mm and the ID is 33.7 +/- and standard BSA threaded.

Enough about the bike and on to the conversion.
Because of the plus size tire capability the rear chainstays are really wide and since the chainstays are 435mm long(rear tire is within 3/8" of seat tube) they bulge out very close to the BB. This was my main concern since I'm trying to use the 68-73mm BBSO2 that I already have.
After measuring and even making a template that I could take into the store I found that it would be a really close fit. So I picked up some freehub/BB spacers in various thicknesses and ordered a new crank arm puller.

Today I got the chance to try it out. I used a 3mm spacer on the drive side and I have just a slight amount of clearance between the gear reduction housing and the chainstay, Great. And the nut has full thread engagement on the non drive side, Great. The Bafang crank arm has plenty of clearance on the drive side, great. BUT the Bafang crank arm hits the chainstay on the non drive side, Damn. So I figure since the bike came with 170mm crank arms I would try the stock arm on the non drive side and it clears, NOT Great! It has the wrong square orientation, while the bafang uses a diamond ◇ the Schwinn uses a square□.... But since the offset crank arm clears on the non drive side by just about the same amount as the straight Bafang arm clears the drive side I ordered a new 170mm offset left crank arm and when it get here Thursday I'll do out and see how it works.

Once that situation is resolved I will consider the possibility of modifications that may get the motor closer to the BB. Chainline could use a few mm of help. But before I do that I need to research my chainring options. Right now I have a stock Bafang 44t and I'm wondering if using another and cutting the chain ring off of one and cutting the center hub from another then welding the second one to the inside of the first would work. I looks like there is plenty of room and this would reduce my chainline offset by the thickness of the chainring and that's atleast 2.5mm. But that seems like a lot of work for so little gain. And there is the Bling Ring option and is the route I will likely go with. And like I mentioned earlier I am considering thinning the back of the gear reduction housing and possibly the chainstay though I would rather not modify the frame.

[73Eldo]

I have heard that isn't a terrible bike. Schwinn for the last 20 some years and Walmart usually didn't spell quality but I have heard that that has been changing especially with their special addition online only models. Interesting frame design especially down by the BB. What size was the original front chain ring? That chain line does look a little funky. I wonder why they went with a 73 bb and the 135 hub? Seems a little odd these days, I'm sure there has to be some cheap ass wider things around these days. What is that 142 boost thing?

I'm pondering my winter 'street' build and don't have anything with discs. Looked on the used market and almost nothing for sale has discs but I will be watching your project to see how it goes because getting a new bike like this may be a reasonable option rather than trying to convert to at least a rear disc. Just thinking in the snow and ice disc will be nice. Both my 'extra' BBSHD's are the narrow ones but I think the gearbox may be bigger on the HD so maybe it would not fit as well as yours is?

[Dshue]

Boost is complicated. So here's a link https://noblwheels.com/blog/standard...v=4326ce96e26c The original front chainring was a 30 t and sat just about as close to the chainstay as the gear reduction housing on the bbso2. The reason for the 73mm bb is the 1x drive train. The single chainring has to move out farther than the small chainring on a 2 or 3x drive train. So rather than the typical 113mm spindle of a 3x this uses a 127mm spindle.
And the chain has to clear the 2.6 tires.
I like the bike a lot. My original thought was that if the motor kit I have didn't fit I'd just return the bike or flip it for some profit. They are in demand. But I decided yesterday that if it doesn't fit I'll keep it and retire the Specialized Rockhopper. Hell if it fits it will effectively retire the Rockhopper anyway.
The biggest knock on the Axum is the fork and I don't plan on jumping or even hopping the bike so it will serve me fine. The only upgrades I have to do are a 25° rise stem and 60mm riser handle bar since this isn't a trail bike I want a slightly more upright position and I'm 6' 7" tall. As it is now it puts me in a cross country riding posture where the seat is slightly higher than the bars similar to a road bike.
I really think this will be an awesome adventure bike.
And the frame has unused cable routing mounts intended for a dropper seat post so the main buss cable for the Bafang will have a clean routing right along side of the rear brake cable.

[73Eldo]

So it comes with classic 100/135 QR hubs? The boost thing is the through hub style which this bike can be converted to? Got any links that talk about that conversion? I heard you could go the other way but thought you kinda needed the dropouts designed for through axle.

Do you know how much larger the gear case is on the HD? You really got me thinking about going this route now and supposedly there are a couple bikes in stock in my area right now. Tempted to go buy one since they are in stock and ask questions later. Also tempting because I already have a selection of 29 tires for my Pug. If I got this I could leave my Pug set up with the 26 fat tires.

[Dshue]

Sorry i have no idea what the dimensions of the HD are.
For the BBSO2B the gear reduction housing is roughly 4.656" diameter and from the back face of the housing to the back face of the Bafang 44t chainring is .675". But there is a roughly .080" or 2mm instep around the BB shaft housing, meaning the gear reduction housing sits to the inside of the bb shell by .080".
I am pretty sure that I've seen dimensional drawings of the HD on here.
Here is the pattern I made to test frames with. It's not perfect and doesn't include the .080" instep but it was close enough and it works on the non drive side as tong as the chainstays are symmetrical as most are. It's just made from foam core board and some thin balsa wood sheet to get the correct thickness. The outer diameter is the size of my chainring and the smaller od represents the reduction housing. The center hole is sized to fit over the BB, flange(which roughly equals the .080", 2mm instep of the reduction housing. What I'm trying to get across is that this step allows the reduction housing to sit that much closer to the center line of the frame.

[73Eldo]

Ah, I thought you had another build with an HD. I will have to go measure one of mine. Ran some numbers through a gear calc and found out with that 40t rear even with a stock HD 46 ring I would have a slightly lower gear ratio than I have now on my Pug which so far has worked well for me. This build would be mostly a street bike so loosing the stock low gears should not be an issue for me. Not sure the 46 will clear but if your 44 does a 42 should and those are not crazy expensive like the 40's can be.

Found some info on the hub axle thing. Youtuber 'trail features' has some videos on the axum and mentions the hub conversion thing. Guess its good that there are options.

[73Eldo]

Hmmm..... HD housing is about 5 1/4 so I would likely need a little more spacer action. How much more thread was left? Yours had some extra with the trim/lock nut thing installed or you just have the main plain nut?

[Dshue]

One thing I left out about my template is that it also doesn't account for the reduction housing covers bolt ears. I believe that with them the cover is 5 ¼" diameter, but with the angle the motor sits in this frame they don't come into play and that diameter can be ignored(unless the HD has the ears clocked differently to the O2)

I only have the main nut but honestly the Bafang outer locknut doesn't seem to help anyway. They need to design it with either a key way for a keyed washer or with a flat for a D washer between the nuts so that rotational forces from one can't affect the other.
And I'm looking at a few options to solve the loosening bottom bracket issues
1) making a nut retainer that will lock into the notches of the nut and bend around the V plate that bolts to the motor,
2) drill the nut for safety wire,
3) have a tab welded to the nut for safety wire,
4) drill and tap the nut for 1 or 2 set screws that would press against the V mounting plate, this also gives the option of dimpling the face of the v plate so the set screws won't allow the two to move independently while the jacking effect further locks the threads effectively making the nut tighter than it was with the wrench only.

I may also build a torque arm.
On the previous build I used red locktite plus had the lock nut on and it still loosened.
As far as spacing goes I am thinking of thinning out my reduction housing cover for better clearance. I haven't checked but I don't think it is necessarily a structural part. It just keeps dirt out and grease in. And it is the main reason for my needing to space the BB out 3mm. I really want that 3mm back and with some creative contouring with a file on the back side of the cover and housing I think I can get most of that 3mm back. It's just hard to bring myself to permanently alter a $460 part....

[73Eldo]

Those ears may be the difference in the gear housings, the HD doesn't have ears so maybe the innards are the same its just they when to a full flange rather than ears? The BB is exactly 73mm? I wonder if the HD is any longer? If you used a 3mm then the triangle plate which is what about 2-3? Then the nut that is about 5? So about 85 total into the recess to the end of the threads? I just checked the loose one I have and its 95mm from where you would seat into the recess to the end of the threads so other than the chain line seems like the HD should work. I do need to tear into my loose one so that would be a good chance to see how much 'meat' is in that housing.

I got a little too excited about buying a new bike. Decided since its nice again today I should take a 20 or so mile ride on a route I have done before on the antique schwinn just to see how a different bike feels and how different it is than my mid range Surly. I can swap over my grips, suspension post and seat, and SPD's to make the contact points the same. I may find that there is a reason Surly's cost so much or that its not a big deal for the streets.

Plus after tomorrow we should have some more info on how it rides right? What sort of riding are you planning at first? With my luck you will love it and they will be sold out again.

[Dshue]

With the 3mm spacer on the drive side I have full thread engagement using just the triangle mount and the main nut. But no thread left to even start the outer lock nut. I presume if I can get rid of the 3mm spacer I could get the lock nut to at least partially engage the threads on the shaft.

Hopefully I get the crank arm tomorrow.
First thing is I'll get it mocked up to test it out. I'll just keep the first few rides close to home. Then when I'm satisfied that it's going to work good then I'll finalize all of the wiring, rack etc. and work on the chain line. But due to budget constraints I'll have to hold off a little while for a Lekkie Bling Ring if it's required and from what I see the bling ring will supposedly get me 9mm closer to the centerline. And honestly I think that would be all I need.

I assure you that with the chain line sorted out I WILL love this thing.

For me the reason this bike is a great candidate is size, I need a large frame bike. Then it's the wide rims and plus size tires, this helps avoid pinch flats and provides shock absorption which my back loves. Then there is the front fork, while it's a low buck spring only fork with no damping it does have 100mm travel AND it has a lock out, so for times that the battery dies or the electronics fail I can lock out the fork and not have to deal with fork bob as i pedal(The fork lock out and the 35mm wide wheels is why I chose the Axum over the Taff)Then there's the 8 speed rear cassette and the range that it has. The 40 t first gear should be amazing with the o2. I think the 28 t first gear on the previous bike was good. So we'll see if it is better. One thing is for sure it will make the pas system feel completely different. And the 11 t high gear should be quite nice, though I was more than happy with the 14 t high on the old bike. But there is some significant difference in tire circumference between the two bikes so we'll have to see what effects that has, there is about 1/2" difference in axle height.
And I may just put the crankset on my Rockhopper. It's in need of a new chainring set and I have a list of items to convert it to 1x and now I shouldn't have to buy anything to do it, so killing two birds with one stone.
I want to ride anywhere I can, streets, alleys, single track trails in the woods, power line trails etc. Here in western Pennsylvania we have lots of hills from steep to gentle and we have some of the worst potholes in the world. Narrow road shoulders and most of them have 3" plus drops from the paved surface to the soft shoulder. Drivers also don't give cyclist any room, I've had semis with flatbed trailers pass me so close I could rest my elbow on the trailer deck if they were going my speed. The last bike couldn't handle the rough surfaces, and dropping off of the pavement onto the soft shoulder wasn't an option. And honestly the brakes on that thing were horrible. These are all things that I never worried about with the Rockhopper on the roads.(for years it was my primary bike and saw a lot of road use)It didn't care about drop offs, soft gravel etc. I could just react to what was happening with confidence knowing the bike would handle it and thats how this bike feels.

These bikes are really popular, there are quite a few YouTube creators that have been impressed. The one that turned me on to the Axum is KevCentral. And there are Facebook groups dedicated to it as well. I like the fact that Schwinn has already updated (for the better) the 3 bikes in this lineup.

[73Eldo]

Just got back from a ride on the antique Schwinn and I think I want something that is slightly closer in geometry to my Pug. Pavement was fine but actually crashed twice on trails I rode a couple days ago on the Pug. Not a fair comparison 26x1.9 vs 26x4 but still, I wasn't more than about 20' off the pavement when I went down.

Dug around and found some of the Axum's specs and compared them to my large Pug and many things are close, for sure a lot closer than my antique and one was still showing available in my area so I did it. We will see if its actually there and how destroyed the box is or how badly destroyed and missing parts by the last person that returned it. Never bought from wally world online before , hope it goes well. If the box doesn't look decent I may just try and get my money back right away rather than risking getting it home and finding issues.

Guess I should go out now and tear into my high mile BBSHD to see if its going to be waiting for parts or will it be ready for the new bike tomorrow if it actually exists and is new in box like the website promised me when it took my money. Can always rip the one off the antique if I have to.

Also going to have to look and see what I have for crank arms. How much was the Bafang one hitting by? Couple MM or a lot? Do you have a brand and part number of the crank arm you ordered? Guessing you have to depend on photos to know if they are square or diamond? I don't remember seeing that written in the specs.

Near the end of my ride (after 2 crashes on the offroad section I wasn't planning on hitting) I did notice the drive came loose so I think I too am going to explore other methods of keeping it tight on the Axum. I did have the 'lock nut' on and a few extra threads sticking out so it wasn't an engagement or lack of lock issue. I don't have the fancy socket just the $20 flat wrench. Maybe I will have to try getting a glove on so the sharp edges don't dig in so bad and crank down a little harder?

Do you think I should start my own thread if/when I get mine? Or you think it will be beneficial to others considering a build to have both a 02 and HD on the same bike in the same thread? Personally I would likely be excited to find both options in the same thread if I was considering a build. I know there were times I could not decide between an 02 and HD.

[Dshue]

I tightened the lock nuts on other build with a wrench and gave it extra with a brass hammer and it still came loose. Returns for walmart online bike purchases are easy. Either the box as they shipped it can be returned or the assembled bike can be returned. Right now all Walmart's are accepting returns except in Illinois.
Use care with the disc brakes. Don't touch the rotors, especially with grease or oil on your hands and don't let grease or oil anywhere near them. It's a good idea to wipe the rotors down with rubbing alcohol before assembly just to be sure they are clean before running the pads on them.
This is the crank arm I ordered,
https://www.amazon.com/dp/B07H7ZSFBB..._uVOFFbMG45S4C
The bafang arm barely hit but since the other side cleared by a lot more, roughly an inch I didn't want that much imbalance. And the arm I ordered should have the same offset as the stock arm. Most sellers of single arms will specify the square orientation with the arm vertical. This seller lists it as rhombic but most use diamond and square.

[73Eldo]

I have mechanical discs on one bike now and haven't been super careful around them and how well they work seems to depend on how much mud and sand I have been in recently. Have you looked at what kind of pads they used? Hopefully they are copies of one of the big names like Shimano or Avid so pads won't be hard to find or maybe that will be the excuse to upgrade? I like the Avids on my Surly so I think that would be what I would do so I don't have to 'stock' different pads. I think I saw they are 6 bolt 160 and 180 rotors which is what my other bike has so again one spare part for both rides.

Reviews on the derailleur are not very good but since I plan on riding this thing when ever the snow isn't deep I'm pretty sure the salt will destroy this $10 system as fast as a $100+ one so I don't think I'm going to worry about it till it fails which will hopefully be in the spring at which point I can put something nice on for the summer and partially wear it down before winter when it gets destroyed again.

Have you looked at or read how wide a tire these can take? I may try the stock ones in the sand that got me twice today just for comparison but will likely go to my 2.35 Schwalbe Big Apples till we get snow and ice at which point I got a used set of 2.5 45nrth Nicotine's with aluminum studs to try out so at least I know those will fit. How about rear rack and fenders?

[Dshue]

The pads look like a Shimano M06 pad.
I think 2.6 tires are about the limit. The tread on the stock tires is like a cross country tread.
For fenders I think the front will be easy to source since they are becoming extremely popular in mountain biking. Even Spank sends a fender out with some of their handle bars. The rear will be tricky if you want to protect in front if the rear tire, there isn't much room in between the tire and seat tube. For the rack it does have threaded holes in the dropouts for a rack but not at the top of the seatstays. I plan to use my seat post clamp on rack and fabricate a rear support that will bolt to the dropouts and support the underside of the rear of the rack and put some kick outs to keep my pannier bags out of the wheel.

[73Eldo]

Just saw a 'trail features' yt video on mechanical vs disc and he used the axum for his testing. He gave a link for the pads he used and the link lists them as M900 M06 so you are correct.

[Dshue]

There are also rack options that clamp on the chain stays. Topeak makes a nice rack in that style but it can only hold 26# and it doesn't have a platform like traditional racks.
You can also buy seat post clamps that have rack mounts built in. Like this https://www.benscycle.com/problem-so...hoCzwQQAvD_BwE