Installing BMX BB

[EC Biker]

Can someone run me through the process? I've never done it before, and the set I got came with no instructions. I do have some idea about how to do it, just not a thorough understanding.

Thanks.

[snortpickle]

Hrmm the process shouldn't differ too much between regular 3piece sets. Checkout the profile manual/guide:

http://www.profileracing.com/manuals/3piececrankset.pdf

[FatHack]

Ok, This is best done with a press, but you could (I don't recommend it b/c the cups don't always go in straight) do it with a mallet or a long bolt and some huge washers. Press in one side, put the necessary spacers in the middle (put the axle in if using the mallet method to hold the spacers), then press in the other cup. add spacers to either side as necessary and put the crank arms on. Don't forget to grease the heck out of everything but the cup/shell interface or it will creak in no time and probably never come apart.

[EC Biker]

*edit*

[EC Biker]

What parts specifically do you grease? How do you keep the spacer lined up correctly if there is no axle to hold it?

[snortpickle]

What most people do is get a rubber mallet, grease up the cup and gently tap the cups in. Work your way round tapping. Think of it as installing a headset. You start with the driveside cup. Grease it up a bit..tap it in untill it's flush. Grease up and put in the spindle, don't forget the correct tube spacer to go over the spindle inside the shell. Then you do the non-driveside cup, again tapping it gently as you work your way round make sure you put it in as flush as you can. The non-driveside cup will probably have a miniscule gap and won't be completely flush to the shell. This is normal and caused by the tube spacer that's preventing bearing binding. Now you space and install the drivesidecrank + chainwheel. You've probably gotten a bolt like crank/spindle puller that should be fairly self explanatory to use. Use it. once the driveside is on, secure it with the crankbolt but don't overtighten the crankbolt. I always put some anti-seize compound on the crankbolts but some people like to use blue loctite. Now install the non-driveside crank using the puller tool again. Put in the crankbolt. Tighten, but don't overdo it, the crankbolts on both sides as needed. Et voila. You're done. Well you could use some pedals at this point I suppose

[FatHack]

Originally posted by EC Biker
What parts specifically do you grease? How do you keep the spacer lined up correctly if there is no axle to hold it?

You grease the spacers and the axle, especially where the crank presses on. If it's cratridge bearing, it's also good to put anti-seize on the bearings before they go in the cups. Lining the spacer up is tricky business, usually if you have a press (like a headset press) that fits through the bearing it will fit though the spacer, as they should be the same size. once the cup/bearing is in place it should be snug against the spacer, if not there will be side load on the bearing when you tighten everything up and that is no good.

[bmxr]

What I have found to be the best way to install a press-in bottom bracket (Profile, in my case) is:

-Install the drive side first. Hammer the cup in with a soft mallet, preferably a dead-blow, making sure that it ends up dlush against the BB shell.

-Make yourself a bottom bracket press. You can buy a 3/4" nut and bolt from Home Depot, along with 3/4" washers, for about $2. This works great for easing cups into place. In fact, you can buy bolts in an assortment of lengths and use them for you headset cups, too.

-Then put your bolt in the cup that is installed and slide your tube tube spacer over the bolt. Then you can squeeze the non drive side cup in there evenly and without hitting it with anything.

This has worked great for me for years and is very cheap and reliable.

Good luck!

[EC Biker]

Okay, what I have so far:

1. Grease everything.
2. Install drive side bearing.
3. Take spindle, put it through the bearing, slide spacer over spindle.
4. Tap in non-drive side bearing.
5. Make sure everything rotates properly.
6. Install crank arms, sprocket, bolts, etc.

Is that about right?

[snortpickle]

Yeah that's the general idea. BMXR's homemade cup press also sounds like it should work wonderfully for installing the non-driveside nice and straight. For future investments look into the profile evolution BB. I have one of those. It rocks. You don't have to muck about with press in cups anymore for a bmx bb shell.

[snortpickle]

Oh one thing. If you're planning on using a cupmounted chainguide. Please remember to compensate the inner tube spacer for the width of the chainguide mount with an extra spacer.