Octalink Questions.
 

I picked up an 08 Diamondback Response Sport which has an Octalink BB. I bought it in Feb and rode it probably twice on a decent butt kicking trail and about two dozen times on lengthy road rides. I noticed yesterday I heard a certain creak, which I'm almost positive is due to my pedals since the pedals I put on this bike were about 7 years old and didn't look to be in the best shape. But out of curiosity I lined up my crank with the bottom of the frame so they were both parallel. Then I used my hands to just use pressure by clamping them together to see if I could generate any "play" in the BB.

It moved... a very slight bit. Nothing earth shattering or "OMG GO ORDER ONE NOW!" but just barely enough to even notice. Thing is I never checked this before, so I don't have anything to compare on. It could have been like this since day one and very possibly it just may be completely normal, I don't know.

Pretty much every single place I've read stated that Octalink is stronger than square taper, but this of course is very dependent upon the actual parts you buy - a good ST could be better than a cheap Octalink, etc.

But for a stock Octalink BB on a Diamondback in the 400 dollar range, is it out of the question to consider it "may" be going bad now? Octalink owners - how long did your's last?

Any additional input?

Thanks!

So the replies you got in this thread were all worthless?

I hadn't realized I posted that exact thread here. I post on several bike forums.

But to answer your question, no, that thread does not answer my question. My question in that thread was understanding the different types of bottom brackets that were available and how they were similar/different from one another.

My question this time is questioning whether or not my current Octalink is "normal" by what other riders have experienced.

So, back on topic - Can any Octalink riders attest to whether or not my slight movement is normal with your average Octalink or is it a warning sign I could feel some grinding very soon?

When you're "rocking" your crankarms do they both seem to move or only the left one?

If it's only the left one, find somebody who has a torque wrench and snug the crank bolt down to 30 lb/ft pronto.

If it's both crank arms it might not be time to replace it yet, but it's certainly time to start saving for a new bottom bracket. Yours is dying.

Not normal, check your crank bolts, if they're tight replace the BB. Fast and easy to replace, doesn't cost a fortune either. I had a Deore crank that would work itself loose over time, had to tighten maybe once a month. Was going to just replace the BB but found a sweet offer on a HTII crankset-BB combo.

Considering the amount of time I spent riding, which I don't think has been all THAT much (however, there is a tremendous amount of uphill I do for strength training), is this considered kind of low/average/high for the life span of an octalink BB?

The only reason I haven't jumped the gun and grabbed one is I don't have the tool for it. I'm a hard working poor guy like many others around here so just being kind of a rookie in the biking scene, I have to often associate tools cost with the part cost for whatever upgrades I want to do.

I checked bikepedia to see if my shell was 68 or 73... it didn't have anything listed. Is there any kind of resource I can find to ultimately say "YES, this is 73mm" or whatever?

you could mesure it i guess

Well, yeah... but I never did this before so I don't know "exactly" what I'm looking for... do you just measure to the outskirts of the shell, or do you have to measure something inside of the shell where the actual BB is?

The problem I see on a regular basis with $400 bikes is that they were usually poorly assembled in the first place, and the BB was never checked to start with. If your crank bolts are indeed snug, then yes, it's time for a new BB. When your BB starts to come loose and you don't know it, yet you keep riding on it, it becomes really bad, really quick. No different than headsets or hubs. Snug up the crank bolts and start saving!

The bolts are really tight from what I can tell, however I don't know if it's because I know what I'm looking for now or if it's gotten really bad, really quick, but now every single time I rotate the crank while riding uphill (so there's a decent amount of torque) I do hear a crack.

I'm going to do a little digging on my bike, octalink bb replacements, tools, etc. Meanwhile, does anybody have any suggestions of particular tools that would work for me without breaking the bank? Or perhaps a certain octalink that may be better than the next?

All you need is a Park Tool BBT-2 or 22, or a copy of that. And a 10mm hex key for the crank arm bolts. For the cartridge itself, go for the slightly more expensive BB-ES25, it's just a few $ more.

Edit, if you haven't looked it up, here's the procedure with illustrations http://www.parktool.com/repair/readhowto.asp?id=94

How did you check it?

To understand 30 lb/ft imagine a 30 pound weight hanging off the end of a foot long wrench. That's quite a bit of torque. If you're checking it using a 6" long allen wrench, you aren't there.

Undertorqued crank arms, especially on the left side, are fairly common. Using up a cartridge bottom bracket in 6 months may be possible, but it's comparatively rare.

For measuring shell width, just the outside edge-to-edge distance of the shell itself (not including any BB spacers/components).

Regarding play, I would think you'd also want to make sure the BB itself was tight in the shell, but you've got to remove the crankarms for that.

So if I just pick up a torque wrench, a proper sized octalink BB, and a splined BB tool, I should be in good shape?

Do I need to do facing with an octalink, or is that only with external bottom brackets?

Facing is dependent on the quality of the face of the shell. Even with square taper cartridge units you'll sometimes have to face it (the frame) if it's especially bad.

I'm sorry to sound like an idiot, but I'm still not sure what I need. I went on ebay and put in "BB-ES25" and came back with several things.

Along with the 68 vs 73mm part, there's also a 2nd number...

73x118
73x126
73x121
68x126
68x121

gahhh... How can I figure out EXACTLY which one I need?

What model crank arms do you have? The Shimano model number is usually (always?) cast or stamped into the back side of each crank arm near the pedal spindle.

Once you have the model, do some Googling to find out what length bottom bracket spindle Shimano specs for it.

That's the spindle length. Crank specs a certain length bottom bracket for a standard chainline.

Why single out the left

Ahh, I understand. I do remember seeing a stamped number but I don't recall it. I'll figure that part of it out when I get home.

Tool wise, I got a torque wrench coming that is 0-150ftlb and an octalink/isis splined bolt extractor. Besides the actual bottom bracket, along with some youtubing of how-to videos, should I be good to go?

Because that's the one that always comes loose.

If you take out your old bb, it will probably be labeled with what its dimensions are. If not you can measure it with calipers (cheap@harbor freight, or borrow a pair). The nomenclature is shell width X spindle length. After this you can always put it back in while you wait for the new one to arrive. Also, it is unlikely but possible that you bb is coming loose from the frame. If that is the case, snugging it down should help. When you install the new one, be sure to start the threads by hand so that you do not cross thread it as that is VERY easy to do. Also, the drive side cup is left hand thread.

Why is the left more prone to coming loose than the right

I've got a couple of theories but I really can't say for sure, I just know for sure that it's true. Most bike shops even keep a couple of left crank arms around for quick replacements.

I'm thinking that a bike guy like yourself has to know that also. Are you trying to pick on me?

Until I figure out exactly what BB I have, if I keep riding on my current one, is there a high probability that I could ultimately mess up anything else?

I hear a creak when I'm really torquing down in a small gear, but it doesn't have that much movement in the BB itself. Just enough to realize that something may be wrong here.