bangozango

I have a 95 hardrock that has a 73mm bottom bracket, bought a replacement 73mm bottom bracket (gineyea brand as I couldn't find a place that sell other 73mm models where I live). I put some antiseize and the drive side went in smooth, but the ND metal cup goes in all the way when tightening, leaving about 3 bb threads exposed. In the end I decided to back it out so the cup sits flush with the frame. The bb has no play and axle turns fine. Is it OK to leave it as is, if the cup isn't tightened?

Bill Kapaun

If it looks like this, screw it in all the way to the proper torque-

IF it's plastic, I'll usually leave the DS a thread short of screwing in, install the NDS and then go back & tighten the metal DS cup all the way.
I loosen the DS first when removing, since the plastic NDS cup will often break if exposed to weather/UV etc. for a few years if you don't.

FBinNY 

Cartridge BBs of this type require that both cups are bottomed out against the cartridge. Failing to do so causes two problems.

1- the gap can allow the cartridge to move sideways.
2- not being tightened against a hard stop means the cup is free to rotate and progressively loosen

Neither condition is desirable, so do the job as specified by the maker. If you're concerned about the exposed threads, wipe a film of grease or work some wax into them to prevent rust.

bangozango

Thanks guys, I tightened it all the way, with just a few threads hanging out

Duragrouch

Am I right in saying, that even though he is supposed to have been given a 73mm BB, it might be a 68? 3 threads is about 3.17mm. (25.4/24) x 3

bangozango

Duragrouch you're right, I decided to strip it and compare (it's in my album, can't post pictures). I should have done this before installing, facepalm. Seemed like gineyea included the flange in the measurement, it's not exactly 68mm, but sure doesnt look like it's for 73mm bb width either.

I found a bike parts shop that sells BB-UN300, in 68x113, and the shop says it's compatible with both 68 and 73mm BB shells. I have my doubts, but just to be sure - is it true?

Duragrouch

You're gonna end up with the exact same issue, if it's a cartridge bottom bracket, unless they include a spacer or two different caps so that it mounts flush on both sides. EDIT: When measuring the cartridge, you do so with the "cap" in place, measuring from its outside, to the inside of the flange on the other side. That should measure darned close to 73, or it's wrong.

With a hollowtech II style BB, with two external bearings, they don't care if the BB shell is 68 or 73, BUT the length of the integrated tube spindle does care, the left spline will either be recessed 5mm (less clamping length), or protrude 5mm, unless they have a clever way around that, such as designing the spindle for 73, but on a 68, you need to use a 2.5mm spacer on each side.

"I'm a smart person. I help people." - Kermit the Frog, Sesame Street, 1970s

bangozango

Thanks for clarifying! That's very helpful to know, it does only seem to make sense that a 73mm cartridge can fit a 68mm bb shell using spacers, but not the other way round. I'll have to keep looking for another BB, but at least now i know at least switching to hollowtech II is an option if all else fails, it seems these are being sold everywhere here...

FBinNY 

It's a distinction without a difference.

What matters is where the crank arms end up. The right is easy, with its position and resulting chain line set by the flanged right cup.

If the BB truly is too narrow, the left arm will be inboard by those 5mm. I assume that if the.arm were too far in and hit the chainstay, you would have noticed and mentioned it. So, consider yourself blessed with a lower Q-factor and move on.

FWIW, I suspect (but don't know) that the only difference between 68 and 73mm versions of this BB may be a 5mm wider left mounting cup. So switching it out won't change anything.

Duragrouch

You could also use a 68 in a 73 shell, if they included two different end caps, 5mm difference in thickness.

Also, using a 73 in a 68 shell would require 5mm spacers under the flange end, and that may screw up your chainline, as it will space the crank outboard by that much.

Duragrouch

Some useful info I posted on a different thread; Advantages and disadavantages of internal cartridge BB, versus external bearings with hollowtech II style crankset:

"Internal cartridge" bottom bracket, design been around many decades. It replaced "cup and cone" BBs which had loose or caged balls, solid axle (usually square taper ends), and bearing cups (outer races that threaded into the BB shell).
Advantages:
+ Huge labor savings for service; no need to remove and clean bearings, repack with grease, reassemble. The cartridge just screws in and you're done.
Disadvantages:
- Once the cartridge starts to "loosen up" from wear, there is no way to adjust it out. It'll still be a while until the BB fails, but the axle will be looser, which stretches the seals (letting in rain if applicable), accelerates wear on the bearings (because a loose bearing only loads 2 or 3 balls at a time, whereas a "snug" bearing loads about half, 180 degrees of the bearing balls under load), and makes the chainrings wiggle.
- Cost; More expensive in parts than cup and cone bearings which can be rebuilt for ten cents in grease, two dollars for new bearing balls if needed. For this reason, cup and cone bearings still dominate low-cost bikes, and most especially bikes in the third world.

The other style BB bearings that you may have seen are "external", 2 parts, each a bearing that mounts between the BB shell end faces and the crank on each side.
Advantages:
+ Allows a larger diameter, hollow BB axle, which is stronger, stiffer, and lighter.
+ Like internal cartridge, quick to replace.
+ Because external, bearing balls are larger and/or more of them, making the bearings more durable.
+ Bearings are closer to each crank arm, reducing bending moment on axle and loads on bearings, making the bearings more durable.
+ Unlike internal cartridge, ***slack over time can be adjusted out, to back like new***, you just loosen the left crank arm, adjust preload, replace crankarm. Restoring the preload reduces load on individual bearing balls. This makes the bearings more durable. (Are you sensing a theme?)
+ Backwardly compatible! Can fit in BB shells whose design dates back 100 years.
+ Can remove crank (even in the field) by simply loosening two allen-head screws on the left crank arm, I don't need a "crank tool".
Disadvantages:
- Requires replacement of the entire crankset for (one example) "Hollowtech II" style; This has hollow (pipe) BB axle permanently attached to the right crank arm, it slides through both bearings, the left arm attaches with a clamp around splines on the end, and there is a cap on the end to adjust bearing preload.
- Requires a special wrench for the outside splines on the bearings, which vary greatly, but the most common standard is "ISO External"; I bought a 4-way wrench that has that pattern, as well as 3 others, in case I need in future.

The good news is, Hollowtech II style is now available generically, so a whole double chainring crank with chainrings, and ISO-External bearings, cost me USD$65, cheaper than just the chainrings would cost. I ordered a 2nd one for spare parts, cheaper.

For any of the above, be careful:
- The cup or bearing on the left (non-drive-side) of the bike is RIGHT HAND THREAD (normal; righty-tighty, lefty-loosey).
- The cup or bearing on the right (drive-side) of the bike is LEFT HAND THREAD, left rotation (anti-clockwise) tightens, right rotation (clockwise) loosens.
This helps keep the bearings tight. This assumes you have a BSA*/English BB shell standard, the most common.

There are more rare BB designs (such as "Italian") where the right cup is right hand thread, and they have a habit of coming loose.

* Birmingham Small Arms (yes, that Birmingham, UK); Guns, bicycles, motorcycles, etc.

bangozango

Ah that makes sense. The lowest spindle length I could buy was 113mm, 4.5mm more than my old 108.5mm BB, that could be why! Glad to know this works, I still want to find a proper sized BB, since this one is neither 68 nor 73mm

Right like FBinNY said, that makes me wonder if they gave me a 68 ND cup by mistake

Thank you all for the wonderful insights, I learnt a lot!

Duragrouch

Our messages crossed, didn't see his till I posted mine. Great minds think alike.

bangozango

Holy.. that's some incredible info! After what you said, I looked around and the price for a generic crankset + hollowtech II bb from china, indeed cost slightly more than just a BB-UN300 cartridge. Definitely looks like something worth upgrading to!

Duragrouch

That's what I'm saying. I upgraded my folder, a 1X crank didn't give me enough range. First bought a square-taper triple crank, wouldn't work, the front derailleur wouldn't go in far enough for the inner chainring. Plus, the crank weighed a ton, it was cheap. So I looked at other options, and the new 2X cranks with a 16 tooth difference, would give me almost as much gear range, so I ordered one in Hollowtech II style, worked for gearing, but then studying it carefully, I realized how much better a system it really is. Plus, once bearings installed, I can remove the whole crank by simply loosening 2 clamp screws on the left arm, I don't need a "crank tool". It's just plain BETTER. Somebody was thinking. I also liked that I was able to find a HT2 50/34 in 5x110mm BCD bolt pattern, I prefer over 4 bolts, and most especially 4-bolt-asymmetric pattern. My crank also has a "low q-factor", the pedals not as far apart because the crank arms are straighter, this is usually the case for a "road" crank. Mountain cranks tend to have a larger q-factor. If off amazon, make sure you scroll down and read the fine print, where I bought sold several cranks, the one pictured had aluminum chainrings with lift pins, and that's what it said, but the one they sent me had steel rings. I politely asked WTF and they sent me aluminum rings and updated their ad to read steel for the 8 speed crank.

bangozango

That's must have been a pretty satisfying find! Most HT2 cranksets I see here are 4x104mm BCD, and max 38T on single chainring. Is there any advantages a 5 bolt pattern would have or just a matter of preference?

Duragrouch

Aesthetics mostly, I'm a stickler for classic bike style when possible, 5x110 is an old standard. Technically, the rings should also have a bit more lateral stability. But mostly, I hate proprietary interfaces, which shimano symmetric-4 and asymmetric-4 were in the beginning, the're both now available generic I think, but I still love 5 bolt. I'm used to road 5x130mm BCD, I needed to go 110mm BCD to get that 34T low; Any lower and I need a smaller BCD for the inner ring, like 5x74mm.

Oh, I revised my earlier post and you probably didn't see, look at the end and see my comments about "fine print".

Oh, and Shimano has engineered their recent cranks so that only Shimano-brand replacement chainrings look right, where it blends into the crank arms. Hate that.

bangozango

Thanks! The older cranksets do look very pleasing, like the older suginos, some of them having very interesting patterns.

Duragrouch

This is the crank I bought, currently unavailable on amazon, but I have seen them on ebay:

https://www.amazon.com/Bibike-Cranks...dp/B08NXJ6F59/

bangozango

That's pretty slick looking! Apparently they have square taper variants of the prowheel ounze you posted too

FBinNY 

Why? To what end?

Back at post 4 you were perfectly happy to have a working BB. Then, upon learning it might be "wrong", you're no longer as happy, despite the fact that it's working perfectly.

Sometimes you really don't want to know what's in the sausage, and should just enjoy the meal.

It's your bike, and you're free to spend dough if you wish. But don't convince yourself that it's mechanically necessary to do so, until it actually is.

Duragrouch

Yes, but then you miss all of the other benefits of a HT2 design, for the same price, if you are replacing a crank. Don't get me wrong, square tapers are fine, I clung to them forever because it was a non-proprietary design. But the biggest advantage of HT2 to me is that I can adjust out bearing slack when it shows up, and that makes the bearings way more durable. Internal cartridge BBs would begin to get a bit of bearing slack in 1 year of daily commuting, and that was all dry, I never rode my precious road-race bike in the rain. Just a lot of mileage.

Now one person on another thread said they were getting better durability on a mountain bike with internal cartridge BBs, and I could see that making sense, as the seals are well away from the crank, whereas on HT2, the seal is close up against the backside of the crank arms, so any dirt getting between, might grind away at the seal. So HT2 is not perfect. But for a roadie, I think it's superior. EDIT: I looked back at your original post, 1995 Hardrock, sounds like a mountain bike. If riding on a lot of dirt, perhaps staying with square taper BB is better. You might ask others who use HT2 on a mountain bike, see what they say. Also, a road crank on a mountain bike, the crank arms might not clear the chainstays if they are fat and wide apart there to clear big tires, you might need a bigger q-factor.