Changing chainset/BB question

lizzylad84

I'm hoping to change the current chainset on my bike from a FSA vero to shimano ultegra, but I'm unsure what bottom bracket I'll need, i presume itll be the shomano equivlent bb? not sure what size or type my current bb is. don't suppose anyone on here would have an idea?

seamus

The FSA Vero from what I can tell uses a 3-piece crankset, square tapered. What this means is that you have two crank arms which are bolted to an axle. The axle is probably integrated into the bottom bracket as one piece, and the ends of the axle are square shaped.

The Ultegra crankset typically uses a two-piece hollowtech II crankset*. What this means is that the axle is welded to one of the crank arms and is then slotted through the bottom bracket. So you can't mix and match

You want a Shimano-compatible hollowtech bottom bracket. Lots of people make them. Unless you have one of the rarer makes of bike, you want a 68mm shell with English/ISO threads. Italian threads are for contrarian manufacturers and larger shell widths typically for mountain bikes.

You need a few special tools to remove your existing crankset and install the new one. You also need a good degree of care to avoid damaging the threads in your frame. So I would recommend handing this over to a bike shop to do.

mp31

seamus wrote: »

You need a few special tools to remove your existing crankset and install the new one. You also need a good degree of care to avoid damaging the threads in your frame. So I would recommend handing this over to a bike shop to do.

IMO, as long as you have the correct tools and can use them with reasonable care then there is no real danger of damaging threads etc. and no need to go to a bike shop. YMMV when it comes to using tools but I don't think it's that tricky.

@OP: Why are you changing cranksets BTW? Is it for a better shift quality or different ratios?

seamus

It's a risk. There are only two major places now where you screw things into the actual frame; the derailleur hanger and the BB*. And the former is replaceable if you screw it up, the latter may not be.
It's a risk, and you're right - as long as you're reasonably careful and remember to never ever force it, you should be fine. But if DIY isn't a strength then you may lack the experience to know what is and isn't forcing it. So for the sake of not scrapping your frame, it would be money well spent in a bike shop.

*I wouldn't include bottle cage bosses or eyelets in that

lizzylad84

mp31 wrote: »

IMO, as long as you have the correct tools and can use them with reasonable care then there is no real danger of damaging threads etc. and no need to go to a bike shop. YMMV when it comes to using tools but I don't think it's that tricky.

@OP: Why are you changing cranksets BTW? Is it for a better shift quality or different ratios?

Changing it for better shifting quality, not quite confident in my climbing ability yet to switch from compact to standard/double cranks

mirv

If it's over shifting quality - let me ask you a few questions - how clean is your drivetrain, and do you have a new or properly degreased and lubed chain and clean cassette, or are they worn and need replacing? Also, how well is your front derailleur set up and do the cables need replacing?

You might be better served doing a good clean, and it might be prudent to change your chain, and then cassette before you replace the chainset. If the chain/cassettes are worn and stretched and you don't replace them first, you'll just ruin the chainrings on the new ultegra crank.

Having your drivetrain in good condition means that even entry level gear can shift very well. On a slight tangent here, but there are lots of 'ultegra is better than sora or tiagra' opinions around, but they often fail to mention that they haven't taken care of their drivetrain and are comparing a neglected dirty drivetrain to a freshly installed groupset.

Mugser

seamus wrote: »

You want a Shimano-compatible hollowtech bottom bracket. Lots of people make them. Unless you have one of the rarer makes of bike, you want a 68mm shell with English/ISO threads. Italian threads are for contrarian manufacturers and larger shell widths typically for mountain bikes.

Apologies for the hi-jack but would I be correct in assuming that the 68mm refers to the width of the frame at the bottom bracket?

seamus

mirv wrote: »

Having your drivetrain in good condition means that even entry level gear can shift very well. On a slight tangent here, but there are lots of 'ultegra is better than sora or tiagra' opinions around, but they often fail to mention that they haven't taken care of their drivetrain and are comparing a neglected dirty drivetrain to a freshly installed groupset.

You're absolutely right. The only thing is that triples are notoriously finicky and can require a lot of fiddling and maintaining to get right - especially if things aren't lined up just right. Doubles and compacts are far easier to setup and maintain because they effectively operate in a binary mode. So once configured correctly, shifting just works.

Mugser wrote: »

Apologies for the hi-jack but would I be correct in assuming that the 68mm refers to the width of the frame at the bottom bracket?

Yep.
http://en.wikipedia.org/wiki/Bottom_bracket#Shell_diameters_and_threading