MarkInMilwaukee

Hi Everyone, first post on the forum so please be patient if I somehow stumble.

I'm doing some modifications to a Framed 29er and ran into some issues with a 68mm (internal 20 spline) bottom bracket which kind of surprised me. Straight from the manufacturer, I noticed the drive side (shouldered) bearing cup had not been seated fully against the frame. This BB uses a lock ring on the ND side. I did not catch this at first and probably rode the bike less than 30 miles before deciding to change the sprocket ratio. The bearings are Samox 1905317-2RS. The internal spacer is marked "EBS - 2 - 68 - 52mm". The crank spacing washers are all installed outboard. Everything was adequately lubed and not binding, but the bearing cups were pretty much just in there without any torque and the 180° wearmarks on the spindle are making me wonder if it somehow skipped quality control on BB torque-down.

Questions - 1) Shouldn't the drive side cup always be brought up firm against the frame and torqued, or is this different?

2) Why does this BB use a lock ring on the ND side? Is it not intended to be torqued down firmly against the 52mm spacer?

3) Is this an unusual BB or some kind of unique assembly? (I can't find a thing online from any of the stamped markings)

Thanks in advance for taking the time to look at this -- Mark

P.S. - Tried to include detailed pictures but apparently that's not allowed until posting 10 times in the forum.

Iride01 

Are these the pic's you wanted to post?




https://www.bikeforums.net/g/album/31811810

I'll leave the answers to others.

Welcome to BF. Just let us know if you add more pics to the gallery and want post them before getting the magical 10 posts. Someone will find them for you and add them to whatever thread they are intended for.

dedhed

See above.
Might want to post something in the BMX sub forum

​​​​​​https://bmxmuseum.com/forsale/184154

MarkInMilwaukee

Yes! Those are the pics and thank you for making them available. Much appreciated.

MarkInMilwaukee

Thanks dedhed. I'll check it out. That link certainly looks like the same exact BB.

Bill Kapaun

I'm not up on the new fangled stuff (from the last 15-20 years) but my first thought was LOTS of adjustability between BB shell width and/or chain line.

dedhed

https://bmxmuseum.com/forums/viewtopic.php?id=530943

MarkInMilwaukee

So just a quick update on this. Tonight I put the BB back together and seated the drive side flush to the frame. I inserted the spacer and spindle after hand-threading the ND cup in and when I started bringing it all together the spindle came right to a stop. That kind of surprised me, but I guess that's the nature of the beast? I suppose that explaines the lockring on the ND side. Anyways, I backed it off until it just became free, checked for play and sprocket alignment then tensioned down the lock ring. BMX is a different world, it would seem.

MarkInMilwaukee

Well, happy me 🙂 Parts are starting to show up and I'm putting together a 2x front chainring with a 3 speed freewheel on the rear. Amazing how cautious one must be when ordering parts since it's hard to find all the details online. Pretty handy how the BMX bikes use an oldschool pin drive on the front chainring, makes it very simple to drill and rivet them together with spacers to get the proper offset. Facing a few challenges on the front derailleur since the tubing is on the large side, but I'm confident I'll get it sorted out. Thankfully... friction shifters are still available.

Tried to gingerly drift the old freewheel off with a light hammer and soft punch but it wasn't having it. I guess Park Tools managed to get a few more bucks out of me (again and again), lol.