Cannondale bottom bracket help

I bought a Cannondale Ashton Signature frame last year (I think it's identical to a late model Beast of the East) which came with a bottom bracket installed.

It seemed smooth with no play in the axle and isn't seized (I don't have a tool but the guy at my lbs had a quick check). The problem is that on the non drive side there's lots and lots of clearance between the crank and frame but on the drive side, the chain ring was pressing against the bb cup before I could properly tighten it.


The axle definitely protrudes much more on the non drive side:


My first thought was, is it in the wrong way around? But the lockring is the non drive side, which I thought was normal.

The axle measures 110mm so if I do need a replacement, what size should I get (looking on CRC, there's more options that I'd thought). I'm also assuming it'll be a 68mm, English thread, is this right?

What is distance between cranks and chain stays like?

Should be same on both sides and about. 10 mm.

If rh cup is lh thread, then it is bsa (english) bb (most likely) and not italian.

Measure length of bb shell to give starting point for yoyr search.

See if the cups have been swapped round. Some models use the same body but the left hand and right hand cups are removable so they can cover both shell sizes with the same parts. Just new cups.
So you could have the actual body of the bottom bracket reversed and the cups in the right place. If it's still massively off set (but the other way) it *might* be from a road triple, they sometimes had different axle lengths.

Or it might just be a wrongun

First off, Shimano 110mm bottom brackets are asymmetric. The 110 is a 107 with an extra 3mm all on the left hand side of the axle. I don't know why Shimano chose to do things that way, but they did. 113mm is the next symmetrical size up, then 118mm.

You look to have more than 3mm of asymmetry there though. It's possible the bottom bracket was designed to be used in a 73mm shell. If so, that would push everything a further 2.5mm leftwards. Check the flange of the fixed cup. It should be marked "68" or "73".

The other thing is that your bash ring seems to place the chainring further from the crank than it would normally sit. That will give clearance problems unless you use a longer axle or a spacer under the fixed cup to push everything out a few millimetres. You could use a bigger bash ring in the 94mm position, or dispense with it entirely for the moment until you have your other setup problems solved.

one-eyed_jim":20hm4tql said:

It's possible the bottom bracket was designed to be used in a 73mm shell....

Click to expand...

I couldn't see it printed but it's a 68mm shell, so I think you're probably right.

one-eyed_jim":20hm4tql said:

The other thing is that your bash ring seems to place the chainring further from the crank than it would normally sit. That will give clearance problems unless you use a longer axle or a spacer under the fixed cup to push everything out a few millimetres. You could use a bigger bash ring in the 94mm position, or dispense with it entirely for the moment until you have your other setup problems solved.

Click to expand...

It's a Middleburn RS(7, I think) crank with a bashguard that replaces the standard spider and an 18t chainring bolts directly onto the back of it. I'm not sure how the position compares to a standard set up. This is it side on:



I have a bb in another frame measuring (I think ) 127mm - is this going overboard if I just swap for this one? If it makes any difference in terms of chainline, it's a 10 speed at the back but I'm likely only to be using the 15t down to 11t.

Edit: I didn't know you could space them! Is this safe to do within a few mm?

DMC3000":1gjjy9hv said:

It's a Middleburn RS(7, I think) crank with a bashguard that replaces the standard spider and an 18t chainring bolts directly onto the back of it. I'm not sure how the position compares to a standard set up.

Click to expand...

Okay, that makes sense.

I have a bb in another frame measuring (I think ) 127mm - is this going overboard if I just swap for this one?

Click to expand...

That's likely to be much too long. These are compact cranks, intended to be fitted to short axles. 127mm is the longest axle Shimano made.

If it makes any difference in terms of chainline, it's a 10 speed at the back but I'm likely only to be using the 15t down to 11t.

Click to expand...

In that case, would it make sense to fit a larger chainring to make better use of chainline and cassette range? That would let you use a conventional compact spider and bash.

Edit: I didn't know you could space them! Is this safe to do within a few mm?

Click to expand...

It's fairly standard practice to use a thin spacer under the fixed cup to shift chainline out by a millimetre or three. I'd probably look for a metal left-hand cup without a flange which can travel further into the bottom bracket shell to make sure the cartridge is properly supported. On the other hand, I'm not sure I'd trust a spacer for trials use.

one-eyed_jim":33vfefpq said:

...would it make sense to fit a larger chainring to make better use of chainline and cassette range? That would let you use a conventional compact spider and bash.

Click to expand...

For normal riding, I'd have gone with a conventional middle ring and a wide range cassette (I've done this on another bike) but the idea with this build is just to have something a bit more usable than a more modern single-speed trials bike. My 'trials gear' is 18:15 (1.2) so using an 11-25 cassette puts the chain somewhere in the middle of the cassette, and obviously adds a few higher ones for normal pedaling (I'm not bothered about the unused gears, I might even end up just replacing them with spacers).

Using a regular middle ring (say a 32t) would make everything too high as even the lowest 32:25 gear would be 1.28 ...plus Middleburn spiders are a pricey component to replace if I slip and land on it!

one-eyed_jim":33vfefpq said:

I'm not sure I'd trust a spacer for trials use.

Click to expand...

Yep, best abandon that. If I work out where I've put the damn bb tool I'll try a few different things and see what works.

Re

Should it not be a 68x113mm crank for the Middleburn RS7 cranks. I have Rs7's on my F800 and they are in perfect alignment. Middleburn recommend a 113 axle for their square taper RS7's. Mine are set up as a tripple but that shouldn't make any difference.

http://www.middleburn.co.uk/technical-crank-info

Hope that helps

Re:

Thanks, I wasn't aware of this. If I wanted to place it further out so its effectively in the middle ring position, how far would this be (maybe another 5mm?) - would you mind measuring it on your triple?

Re:

I normally stick to the manufacturers recommendations to avoid the expensive experimentation of getting thr bottom bracket the wrong size. I still have some bottom brackets from 15-20 years ago when the information was not so readily available.
Be carefull with getting a slightly wider bracket as presumably if you want to get an extra 5mm on one side you will need to get an axle 10mm wider. I maybe wrong so thats why i stick with the manufacturers sizes. You could always contact middleburn for advice.