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I have a roadbike with a 73mm BB shell and I recently bought a Tiagra compact crankset that has a 110mm bolt circle length. However, I can't get enough of it to come out the other side to properly attach the left arm of the crank.

This is really upsetting because, as far as I can tell, Shimano only makes 110mm length cranks for compact (double) chainrings. The only solution I see is getting a new triple crankset for about €100 and this would mean I have to change my STI shifters and possibly the front derailleur as well... Are there any other options?

EDIT: You are right i was confusing BCD with spindle length, the problem is that the 110mm spindle wont come out enough to attach the left arm, triple cranksets do have slightly longer spindles tough.

The frame with specs from where i bought it

The crankset thats too small

  • You are replacing the crankset, right? What was the old crankset brand/model? – Argenti Apparatus Mar 18 '18 at 17:52
  • I'm a bit suspicious of the frame geometry given in that image - mountain style 73mm BB shell but road style 130mm rear dropout spacing. Can you point us to where the info came from? – Argenti Apparatus Mar 18 '18 at 18:27
  • There was no old crankset i bought the frame online the picture is from the website with the specs and how it came, the bb shell measures exactly 73mm, could they have sold factory faulty frames with the wrong measurements?? – user36972 Mar 18 '18 at 20:52
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    Maybe contact Cube and ask what BBs they use to get a Tiagra crank on an Attain frame? – Argenti Apparatus Mar 19 '18 at 17:59
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    I have answer for that after some research - newer Attains have press fit BB – Argenti Apparatus Mar 19 '18 at 18:35
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You need a mountain bike specific crankset. Tiagra is a road group. Road bikes typically have a 68 mm wide bottom bracket shell, and mountain bikes have 73 mm. The wider BB shell is used to give a proper chainline with the (usually) wider rear axle spacing (OLD) and will result in a wider q-factor (distance between pedals.) This frame is an unusual build with the 73mm BB and the 130mm OLD, perhaps to take advantage of the smaller chainring sizes available in MTB cranksets.

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You are confusing two different measurements. The bolt circle diameter (BCD) is the diameter of the circle the bolts that hold the chainrings lie on, not the length of the axle.

In general a crank needs to be matched to the type of bottom bracket you have. There are many bottom bracket types and selecting a compatible crank is confusing.

First step is to compare your new crank to the old. If the axle is shorter then the new crank is a mismatch.

If the axle length is the same then there may be a spacer that needs to be removed.

If you need to get a different crank you’ll need to figure out what type of bottom bracket you actually have - one for threaded shells or one of the press fit types. Adding a picture to your question will enable someone here to help. Also add the exact model of the new crank (and the old one if you know it).

UPDATE:

I checked the axle length on an older 105 crank I have lying about, and the shell with of the bike it came out of. The axle measurement as shown in your pic was indeed 110mm (I think it's a co-incidence that it's the same length as the BCD, apologies for to misunderstanding and miscorrecting you). My BB shell is 68mm - the common standard for road bikes. So you have a mismatched shell width and crank. This answer may help explain what's going on here. Incidentally, if you have a 'road' Hollowtech II BB for 68mm shells the inner sleeve will not be bridging the bearings which is a bad situation.

I’m suspicious of the B.B. shell width given in the pic. Cube Attain is a road bike and according to the Cube website all the models have road cranks. Did you get a ‘mountain’ style BB? Those come with spacers and fit both 68 and 73mm shells. If so and you installed it with spacers the BB would be too wide.

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Other answers have suggested solutions, but I think I know why the situation has occurred.

The entry-level model of the Attain (and the Axial WLS) use a 73 mm threaded shell, and use a 73 mm cartridge bottom bracket like the BB-ES300. These offer a choice of axle length and use Shimano Octalink cranks, so the axle length can be specified to suit the road crankset you are replacing.

Threading in a Hollowtech II bottom bracket to the 73 mm shell makes the assembly too wide for the (110mm) axle of a road crankset so it won't fit.

Higher spec models use a 73 mm press fit bottom bracket shell. This has no outboard cups and therefore allows the assembly to be the correct width for a road (HTII) crankset.

Unfortunately this all means that your frame will not accept the road style Hollowtech II crankset and the upgrade is off the table. You could explore the use of mountain cranksets but as you appreciate the shifters and derailleurs might not be compatible, or the gearing might not suit road riding. The other risk would be frame clearance. Let us know if you experiment and get it working

  • @LindaKantnerova it’s possible that your question will have been removed by the time you see this as it’s currently in an answer slot. Hopefully this answer gives you something to work with, but if you have more questions, do ask away as a new question – Swifty Sep 10 '18 at 19:45
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The BB for Cube attain 2016 is Shimano BB ES300 73mm x 118mm. You can look for ISIS or Octalink BB/ crankset.

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