Cassette, wheel, front derailleur compatibility

StillGoing

Never really had problems working on bikes, but one I'm working on at the moment is presenting problems. The bike is a 2014 Allez that has been upgraded to have 10 speed Campagnolo Veloce with FSA Gossamer cranks. The wheels are Alexrims S500 fitted with a 10 speed Ambrosio cassette for Campagnolo.

When indexing the front derailleur, the chain continually drops off the inside on the front if it is set with the minimum clearance. The only way of preventing it so far is by having interference when in the inner ring and biggest sprocket combination. When looking along the chain line, it's clear that the chain is at an extreme angle when in this combination. The wheel is true and central. The bike I think originally came with 8 speed 2300 triple speed with different wheels. My suspicion is that the bike originally had a Shimano square taper BB and the additional width of the FSA BB is putting everything out of alignment. Before I tell the owner that they need a crankset that uses a square taper BB in order to be able to dial out the interference and prevent the chain dropping off, has anyone else any thoughts?

mercia_man

I assume you have the outboard edge of derailleur cage parallel with big ring and sitting 1.5-3mm above the big ring teeth. I also find it's important on my Campag bikes to adjust the little ring low limit screw really close so that the chain is virtually brushing or even brushing slightly the inboard edge of the cage in bottom gear. Just a tiny move of the screw inwards (five minutes on a clock face) can make all the difference.

It may be as you say that the chainline has been altered due to a wider bottom bracket/chainset arrangement. In which case, a cheap and easy fix is a Deda Dog Fang for a round seat tube bike. (I think the Allez has a round tube). That's what I resorted to on my tourer which has gone from six speed to nine speed triple over the years and currently has an extreme 39 to 24 drop down from middle to little ring. No matter how carefully I adjusted the Veloce and later Centaur front mech it would occasionally fall off past the 24 ring. A Dog Fang fixed it perfectly.

StillGoing

A chain catcher doesn't cure the problem of noise and I don't think the owner would want one.

I'm inclined to think that the additional width of external bearings on the bottom bracket is the problem and that returning it to an internal bearing set up with a square taper BB is the answer.

mercia_man

Another thought. Are the FSA Gossamer crankset and bottom bracket cups installed correctly and tightened up fully? Is small ring a long way away from bottom bracket and chainstays? Are there any spacers on the driveside of the crank? These are normally used to push out right crank for clearance on mountain bikes but are generally not needed for road bikes.

External cup bearings and cranks don't necessarily mean a wider chainline than an enclosed cartridge square taper system. I'm lucky with my touring bike as I use a 90s Athena cartridge BB with no fixed cup flange so I can adjust it left to right to set chainline to accommodate the various crank sets I've used over the years.

Bobbinogs

philthy3 wrote:

I'm inclined to think that the additional width of external bearings on the bottom bracket is the problem and that returning it to an internal bearing set up with a square taper BB is the answer.

Yepp, I am inclined to think that as well.

StillGoing

Bobbinogs wrote:

philthy3 wrote:

I'm inclined to think that the additional width of external bearings on the bottom bracket is the problem and that returning it to an internal bearing set up with a square taper BB is the answer.

Yepp, I am inclined to think that as well.

I've spoken to the owner and he confirms it originally had a square taper BB set up. That I think solves the problem. Luckily, he still has the original crankset so a no cost problem solving exercise for him.

svetty

OK so the bike originally came with a square taper BB but that still doesn't quite explain why the Campag groupset apparently doesn't work properly when fitted to it. AFAIK a Veloce BB and chainset of the appropriate vintage has the same chain-line as the FSA item that is installed. :?: :?:

mercia_man

Svetty wrote:

OK so the bike originally came with a square taper BB but that still doesn't quite explain why the Campag groupset apparently doesn't work properly when fitted to it. AFAIK a Veloce BB and chainset of the appropriate vintage has the same chain-line as the FSA item that is installed. :?: :?:

I agree. This is a bit of a mystery. The chainline on double ring chainsets for road bikes is generally designed to be 43.5mm, whether there is a square taper BB or external bearing cups. It is a misapprehension to assume that external bearing cups will automatically widen the chainline over a square taper system. But the OP is adamant that the chain is at an extreme angle when on small ring and biggest cog. That's what makes me think there is something wrong with the FSA Gossamer installation. Or else an adjustment issue.

g00se

How are you with maths an vernier callipers? go through these two and compare with the bike. You should be able to determine where the issue is:

http://www.campagnolo.com/media/files/0 ... _06_12.pdf

http://www.campagnolo.com/media/files/0 ... _07_16.pdf

StillGoing

The issue was as I and Bobbinogs suspected; the change from a square taper BB to an external bearing BB (Mega EXO). The additional width of the Mega Exo BB puts the cranks further away from the BB housing and more offset from the cassette putting the chain at an angle even when in the inner chain ring and big sprocket on the cassette. Putting the owner's original chainset back on has lined everything back up with the result the bike is no longer trying to throw the chain on the inside when the proper clearance is set on the front derailleur.

StillGoing

Mercia Man wrote:

Svetty wrote:

OK so the bike originally came with a square taper BB but that still doesn't quite explain why the Campag groupset apparently doesn't work properly when fitted to it. AFAIK a Veloce BB and chainset of the appropriate vintage has the same chain-line as the FSA item that is installed. :?: :?:

I agree. This is a bit of a mystery. The chainline on double ring chainsets for road bikes is generally designed to be 43.5mm, whether there is a square taper BB or external bearing cups. It is a misapprehension to assume that external bearing cups will automatically widen the chainline over a square taper system. But the OP is adamant that the chain is at an extreme angle when on small ring and biggest cog. That's what makes me think there is something wrong with the FSA Gossamer installation. Or else an adjustment issue.

Wrong. Of course an external bearing BB is going to add width when compared to an internal bearing BB. In the case of the Mega Exo that the owner had fitted, this is not far off of 5mm additional space. With a square taper BB, the crankset is almost flush with the BB shell. With the Mega Exo BB, the crankset is offset by a further distance creating the opportunity for the chain to drop off of the inside unless the derailleur is there to prevent it by having an interference fit.





The FSA Gossamer crankset had been installed correctly with no additional spacers added to either end of the axle.

svetty

I am no expert on Specialized frames but find it hard to believe that a 2014 Allez is designed to work with a chain-line far removed from the industry standard 43.5 mm. Hence I still struggle to understand why the FSA BB/chainset and Veloce groupset wouldn't work together - assuming everything is aligned and installed correctly, the OEM groupset notwithstanding.

Just so long as it's working now though I guess it's all good.....

StillGoing

Svetty wrote:

I am no expert on Specialized frames but find it hard to believe that a 2014 Allez is designed to work with a chain-line far removed from the industry standard 43.5 mm. Hence I still struggle to understand why the FSA BB/chainset and Veloce groupset wouldn't work together - assuming everything is aligned and installed correctly, the OEM groupset notwithstanding.

Just so long as it's working now though I guess it's all good.....

Although the bike was supposedly bought in 2014, it isn't a 2014 model. Per the owner, it came with Shimano 8 speed as standard, but I can't fathom whether it was Claris or Sora. The bike is still with me so I'll do some close looks at the decals for any indication of age.

But, as stated, the Mega Exo BB and the FSA Gossamer crankset were both fitted correctly. I think the combination of the crankset being further out from the BB and the bike now having 10 speed on the rear instead of 8 speed, was too much of an angle for the chain to cope with. Reverting to the square taper set up for the crankset has solved the owner's problems.

mercia_man

Glad you've got it sorted, philthy3. As you rightly say, the right hand crank was sticking out too far from the bottom bracket and returning to the old square taper BB brought it in closer and improved the front mech shift. Still a puzzle for me as to why the crank was sticking out too far - apparently way beyond the 43.5mm standard chain line quoted by FSA's website.

But I stick by what I said that cranksets on road bikes are meant to be 43.5mm chainline whether or not you have external bearing cups or square taper bottom bracket. External bearing cranks have different shaped arms and spiders to square taper ones to bring the rings inwards into that 43.5mm position and to retain a narrow Q factor. So they do not automatically mean the rings being further out even though people might assume that extra width of the bearing cups means extra width on the cranks. Cranks originally designed for mountain bikes, including some super compacts now being used by some road tourists, push the rings out further to clear the fatter MTB chainstays, resulting in a sub standard chain line and Q factor for road bikes.

It's covered well by Jan Heine. He explains how Campag Record square taper bottom brackets have a 103mm spindle and TA a 118mm spindle yet both have a 43.5mm chain line due to the Record and TA having different shaped cranks. https://janheine.wordpress.com/2013/01/ ... mystified/

StillGoing

Looking at the back of the FSA crankset, there isn't a recess that you'd expect for the external bearing to not be adding to the overall width. Maybe the bike it came off (A Wilier I believe) had a specific design and is not automatically interchangeable?

mercia_man

philthy3 wrote:

Looking at the back of the FSA crankset, there isn't a recess that you'd expect for the external bearing to not be adding to the overall width. Maybe the bike it came off (A Wilier I believe) had a specific design and is not automatically interchangeable?

That could be the answer. This is sometimes done. I see in the latest edition of Cycling Plus that FSA supply a special SL-K chainset with a custom 5mm offset for the Cervelo R3 Disc to ensure the correct chainline while retaining short chainstays.

StillGoing

Mercia Man wrote:

philthy3 wrote:

Looking at the back of the FSA crankset, there isn't a recess that you'd expect for the external bearing to not be adding to the overall width. Maybe the bike it came off (A Wilier I believe) had a specific design and is not automatically interchangeable?

That could be the answer. This is sometimes done. I see in the latest edition of Cycling Plus that FSA supply a special SL-K chainset with a custom 5mm offset for the Cervelo R3 Disc to ensure the correct chainline while retaining short chainstays.

Well this bike definitely has long chainstays being 60cm frame size. The thing dwarfs my bikes!