standarduck

Hi,

Been riding my caad8 sora for a little while now, and I've recently noticed a grinding noise from the BB when climbing.

I was thinking of swapping out the BB, but I've been told that it's a cup and cone BB. I must say, I haven't got any knowledge in this area, and was planning on a cartridge. I'm guessing that it's trickier to swap than I originally thought.

I'm currently using an FSA crank along with the BB fitted (which came with the bike).

Can anyone help me out? I really wanted to gradually upgrade and swap out the Sora/FSA components for better ones, but this is the first part to cause me any problems, and I've already hit a snag.

FBinNY 

You have a square taper BB. These were the most common configuration for decades before folks decided they needed "improving " upon. Given the square tape it's likely that you also have a 68mm, 1.37"x24 ISO (BSC) threaded BB shell, also the most common arrangement.

So you have a decent selection of BBs to choose from, and can use either a cartridge or loose ball style.

When choosing, confirm that you have a threaded BB shell, then match the spindle length as close as possible.

standarduck

Thank you! So it should be straightforward, if I have what you've said?

And how could I go about confirming exactly what I have? Do I need to remove the BB and have a look?

Bill Kapaun

Take a picture with the arm removed or at least at an angle so one can see the BB cup.
Pic#2 is too straight on to see the BB style.

Andrew R Stewart 

Francis has provided you with the shell/cartridge's threading and most likely width. I agree with his suggestions, I've never seen a Cannondale with a tapered square BB that wasn't a 68xEnglish. But the spindle length is yet to be measured. The first way I'd do to pick the first BB to try (and notice I said to try, not to assume fits perfectly) is to remove both dust caps and bolts. Then measure across the arms right at their outer surface at the extractor threaded hole. This will give you the spindle and some of the arms' width. Then measure in from that same arm surface to the end of the spindle on both sides. Take these two dimensions that are "past" the spindle's ends and subtract then from the first overall arm to arm outer surface and you have the spindle length, within your ability to measure consistently. Repeat a couple of times to confirm.

Method two is much more direct. Remove both arms and measure the spindle from end to end directly.

Shimano BB's come is lengths that vary by 2-4mms. I find that sometimes the spindle length that I've initially determined isn't the best fit. Whether it's because the slight differences in how far up the taper the arms fit on different spindles, because the OEM length didn't give the best chain line or rings' position under the ft der cage and movement range or because the OEM length caused ring/frame interference. Maybe 1 out of 4 or 5 BB replacement jobs I do ends up with a different spindle length that I first thought. Andy.

standarduck

Cannot get the crank arm off at the moment, just my luck. Let me know if this picture is any help or no help at all....

Andrew R Stewart 

Well I had no problem seeing a classic tapered square spindle in the first photos. I don't think any Cannondales used other then a threaded BB unit when the tapered spindles were OEM stuff.

Do you have a proper crank arm extractor? How about the correct BB unit removing tool? If not then you might want to visit your LBS. Andy.

FBinNY 

Nothing has materially changed. You still have a square taper BB, though it appears to be a cartridge rather than cup/cone. But that's immaterial since you're replacing the entire unit.

It's simply a matter of confirming 68mm vs. 73mm BB shell width (most likely 68mm) and the spindle length, by the method Andrew suggested.

Don't over think this, it's very straightforward.

standarduck

68 English - that's awesome. I'll remove the crank arms tomorrow and give it a measure. Will let you know what I find, and then I can go from there.

Thanks to everyone for their help so far!

Bill Kapaun

You have a cartridge BB, NOT cup & cone.
A Park BBT-22 or similar removal/installation tool is what you need + a crank puller.

standarduck

Okay so long story short, I'll be eventually taking the bike to my LBS to get them to sort it. In the meantime - I'm confused.

I bought the bike as it was a good price (but knew little about what I was getting). So a question...

Is it possible to change the bb to something compatible with an ultegra crankset? I'm getting very hung up and confused about the various square tapers and cartridges and stuff!

I'm not a huge fan of the look of the FSA that's on it - and I'd really also prefer a standard double over a compact due to the lack of hills. I'd also like to change the components to help learn about the ins and outs of this sort of maintenance. Apologies for coming across as a novice - but that's an accurate description.

SkyDog75

Yep. Once you remove your existing crankset & bottom bracket, you can replace them with whatever kind you like. When you pick a crankset, just use the type of bottom bracket that it requires.

standarduck

Okay, that's interesting. I'm not that keen on keeping the current crankset, so this might be an option.

However, I'm assuming not just any old BB will fit into the BB shell on the frame...how would I go about making sure I don't spend money on a part that won't fit?

SkyDog75

1) Select your crankset. Choice of crankset will determine the what kind of bottom bracket spindle & length you need.
2) Choose a bottom bracket of the appropriate spindle type & length, in a version designed to fit a 68 mm wide English threaded bottom bracket shell.

For example, let's say you buy a Shimano Ultegra FC-6800 crankset. You'll need a Hollowtech II bottom bracket to go with that, like the SM-BBR60. The BBR60 is available in either Italian or English threaded versions. Choose the English threaded version.

Or let's say you stick with your current crankset for now. It requires a (JIS) square taper bottom bracket. If you can't look up the length of the spindle based on your crank's model, just measure the existing one or look for a label or engraving with the model/specs on it. Pick up a replacement square taper bottom bracket like a Shimano UN55 with the appropriate spindle length. They're available in different threadings and lengths; choose 68 mm English.

Kimmo 

The square-taper BBs tend to last a lot longer than other types, but two-piece cranks are much easier to disassemble, include the spindle with one arm so you never have to think about spindle length again, and are a fair bit lighter/stiffer.

The other downside of external BBs (the kind you get with two-piece cranks) is less heel clearance, similar to oldskool three-piece cranks with straight arms and a long spindle.

BB30/PF30 allows for lower-profile two-piece cranks because the bearings are internal again, but that's a whole new setup that requires a suitable frame.

alcjphil

While most external bottom bracket systems do reduce heel clearance, Campagnolo Ultra Torque cranks do not suffer from this problem. I have a friend who has issues with heel clearance and he has no problem when he rides with Campy cranks, this is on an otherwise all Shimano bike

standarduck

Awesome, thank you to everyone for your help. I have a confession - the grinding was a poor contact between cleat and pedal, and was confusing me by occurring once per pedal stroke.

However, I'm looking to change the crankset anyway, and this advice has been extremely valuable. Thank you to everyone!