Plainsman

I was about to install a brand new BB (JIS), and noticed the feel is a little “rough” when I turn the spindle. Nowhere near as smooth as the 10 year old BB I’m replacing (new crankset, so must replace). Do BBs loosen up a little after break in, or is the less than smooth turn I’m detecting just a sign of a cheap/low quality BB (Sunlite btw)?

blamester

You have it now so might as well use it and keep an eye on it.
Get a new one when you need too.

Unca_Sam

You'll need to provide more information. Newer cartridge bearing bottom brackets do have a little resistance until the seals wear a little, while you'll be able to fine tune a loose ball bottom bracket to your desired amount of resistance.

Plainsman

Plainsman

Sorry about that, I didn’t give you much info. Attached are some photos. When I turn the spindle with a very light touch on the new BB, it feels like there is a small hitch about every quarter turn. Don’t think I’ve noticed this with other BBs. The old one is smooth for 360 degrees, and turns with an incredibly light touch (It’s an RPM).

Unca_Sam

I'm with you. I'd expect a steady resistance for cartridge bearings with no hitch. If you haven't mounted it, you could see about exchanging it for a different one. They have to cut corners somewhere to make it cheap.

dedhed

for a few dollars more you could have had a Shimano UN 55

Plainsman

I have not had luck yet finding the UN55 in a 103.

dedhed

Yeah, they don't go that short. For higher quality in 103mm, you'd be looking at a bit more expensive Tange or Sugino

ThermionicScott 

A smooth drag means the seals are doing their job. Since you can't rebuild the bearings, they ought to be sealed better than old-style cup-and-cone bottom brackets.

Plainsman

Can you be more specific by what you mean by a smooth drag? This one is definitely tighter that the one I’m replacing, but I would not call it smooth. There is definitely no crunching or roughness, as if I had a bad bearing, it’s more like when I attempt to lightly turn the spindle with thumb and forefinger, it gets tight(er) at each quarter revolution and I have to apply just a little more force to turn past those points. Doubt my legs would ever feel it, but hate to install something new that is not right from the get go.

Crankycrank

Put a few miles on it (50+) and check it again. It may loosen up and be smoother as well.

ThermionicScott 

So, when I grab one of my new cartridge BBs out of the tote (UN26, UN55, Velo-Orange) and twist the axle with my fingertips, it's like trying to twirl a big spoon in molasses or a thick soup. There's resistance, but no hitches or anything. Since your fingertips are so sensitive, and you're not applying a lot of force compared to what you do when pedaling, it's easy to think that it's a lot of drag, but it's really minor in practice.

BTW, here's the 103mm bottom bracket I use in my fixed-gear. It's pricier than a UN55*, but has stayed smooth for thousands of miles now: https://www.universalcycles.com/shop...s.php?id=48420

* Checking my records, I paid $26 in 2013... so that goes to show how well it's held up.

UKFan4Sure

FWIW, I've noticed a bit of roughness on NOS BB's before causing me pause. After installing and putting the cranks on, it isn't noticeable I have found.

Unca_Sam

I've been meaning to find a replacement for my wife's bottom bracket since the cups have started pitting. It pedals fine, it's just that the roughness isn't helpful for longevity. The bottom bracket here will pedal just fine, but it may last 90% as much as one with better tolerances.

DOS

If you can, try, very gently, to pry outer seals from the bearings. Once the seals are removed, is the drag lessened? If so, good news, the drag your feeling is the seals and is inconsequential when riding.Reinstall the seals and the install the bb.

ThermionicScott 

Shimano UN26 and UN55, at least the ones in my shop, have an additional little disc pressed onto the axle next to the bearing. I think it acts as a splash guard to protect the bearing where the seal moves. That's a roundabout way of saying that it would take some doin' to get at the seals to confirm whether they're the source of the drag.

As long as the BB doesn't have play or feel gritchy, just install it and ride it until it develops those symptoms.

jbucky1

The rough is just a symptom of a super cheap BB, like others said you have it so may as well just ride it till you need a new one. (if you are not picky)

- james
www.buckyrides.com

Plainsman

The rough BB was an easy return, so I ordered another one, the model specifically called for by my crankset (FSA cranks). The RPM/FSA/TH BB came in today, and it feels WAY smoother than the Sunlite. WooHoo!!! Stupid question probably, but when I grease the threads on the left B.B. cup, is there any need to grease the inside of the cup shell?

Unca_Sam

It's not a stupid question but could likely result in a civil war here. Have you seen the way they'd fight over torque values and greased threads? I grease the cup threads and expect sufficient transfer to the BB shell. I don't see any harm in greasing both sets of threads.

Plainsman

oh, I’m definitely gonna put a layer on the shell as well as the cup. Other than to help with the cartridge install if the left cup is snug, is there any reason to put a thin layer of grease on the non threaded inside face of the left cup?

Unca_Sam

I'm not following what you're asking about. The balls get tucked into a bead if grease inside the cup, then smothered in another layer on top. The threads of the cup and shell get a thin layer. What additional spot do you want to grease?

Again, there are lots of opinions, but unless you're thinking of greasing a braking surface, chain, or a contact point, it doesn't really hurt much if it's not supposed to be greased and it is.

Plainsman

I was just referring to where the left cup slides over the outer face of the bearing.

jbucky1

I always do, a smidge super thin, just because if a customer brings it back after a year its one less thing that could be seized, it is metal on metal.

- james

www.buckyrides.com

https://www.etsy.com/shop/Buckyrides

Plainsman

The seizing aspect, good point. Thanks.