Chainset replacement

[Shut Up Legs]

Yes, I know I'm starting a thread very similar to 2loose's, but my configuration is different, so I didn't want to hijack his thread .

The current configuration on my commuter bike, a Vivente World Randonneur tourer (the drop-bars + STI shifters 2008 model) is:

• Shimano FC-4503 chainset with Sora chainrings;
• Shimano 5700 bottom bracket; and
• Shimano Sora 3403 road triple derailleur.

I want to replace the chainset with a newer and preferably lighter one, but I'm unsure about compatibility with my existing frame's BB shell. The above-mentioned BB fits perfectly, but can I replace this with a square-taper sealed cartridge BB, such as the UN-54? This would give me more options for chainsets, wouldn't it? Someone on another forum suggested the Tiagra 4603 chainset, but I think this might weigh as much as my current chainset, and about 130g more than the Ultegra 6703, so I wouldn't really be changing anything.

Also, after much searching on the CRC site, I found numerous references to 10 speed chainsets, but hardly any mention of 9 speed chainsets. Currently I'm using 50-39-30 on the front and 11-34 on the rear, i.e. 9 speed. Can I use a 10 speed chainset instead, such as the Ultegra 6703, for example? This seems like a nice one, and uses a Shimano 6700 bottom bracket with the Hollowtech II design, so it should be compatible with my frame's BB shell.

Are 9 speed triple chainsets with 50(or 52)-39-30 chain rings being phased out, is this why they're hard to find in online cycling vendor sites? Just about all the 9 speed triples I found had MTB chain rings, e.g. 44-32-22 or 48-36-26.

Here's an image of my current chainset:

 

[RecordAceFromNew]

Yes, I know I'm starting a thread very similar to 2loose's, but my configuration is different, so I didn't want to hijack his thread .

The current configuration on my commuter bike, a Vivente World Randonneur tourer (the drop-bars + STI shifters 2008 model) is:

• Shimano FC-4503 chainset with Sora chainrings;
• Shimano 5700 bottom bracket; and
• Shimano Sora 3403 road triple derailleur.

I want to replace the chainset with a newer and preferably lighter one, but I'm unsure about compatibility with my existing frame's BB shell. The above-mentioned BB fits perfectly, but can I replace this with a square-taper sealed cartridge BB, such as the UN-54? This would give me more options for chainsets, wouldn't it? Someone on another forum suggested the Tiagra 4603chainset, but I think this might weigh as much as my current chainset, and about 130g more than the Ultegra 6703, so I wouldn't really be changing anything.


Also, after much searching on the CRC site, I found numerous references to 10 speed chainsets, but hardly any mention of 9 speed chainsets. Currently I'm using 50-39-30 on the front and 11-34 on the rear, i.e. 9 speed. Can I use a 10 speed chainset instead, such as the Ultegra 6703, for example? This seems like a nice one, and uses a Shimano 6700 bottom bracket with the Hollowtech II design, so it should be compatible with my frame's BB shell.

Are 9 speed triple chainsets with 50(or 52)-39-30 chain rings being phased out, is this why they're hard to find in online cycling vendor sites? Just about all the 9 speed triples I found had MTB chain rings, e.g. 44-32-22 or 48-36-26.

Here's an image of my current chainset:

Since you have HT2 already I see no reason why your frame would not be compatible with all internal BB systems and all similar conventional external cup systems. However, if you intend to stick with triple/double chainset then while a square tapered system has many advantages light is not one of them (given you appear to be in pursuit of lightness), unless you spend BIG money on both BB and specialist chainset.

There is a school of thought that says for conventional road components Shimano is generally not the best vfm for lightness. This might give you some ideas.

IMHO if the terrain allows it going Nx1 is one of the best ways to lose some weight. Separately for the majority of mid/low range bikes careful selection of tyres and tubes is often the most effective way to reduce weight while improving acceleration/feel in a meaningful way.

 

[Shut Up Legs]

Thanks for the reply . The only reason I mentioned a square-tapered BB is that a lot of chainsets seem to require them, so I wanted to keep my options open. Correct me if I'm wrong, but aren't chainsets compatible with only one of these 2 BB types, but never both?

Weight isn't that important; I just thought that if I buy a new chainset I might as well try reducing a bit of weight while I'm at it. Mainly I just want a good sturdy reliable chainset (I mentioned this is my commuter bike). I also don't want to swap this bike out for a new one - I've done 59,000km on this bike and it really is the perfect commuting (or even all-rounder) bike.

 

[RecordAceFromNew]

Thanks for the reply . The only reason I mentioned a square-tapered BB is that a lot of chainsets seem to require them, so I wanted to keep my options open. Correct me if I'm wrong, but aren't chainsets compatible with only one of these 2 BB types, but never both?

Weight isn't that important; I just thought that if I buy a new chainset I might as well try reducing a bit of weight while I'm at it. Mainly I just want a good sturdy reliable chainset (I mentioned this is my commuter bike). I also don't want to swap this bike out for a new one - I've done 59,000km on this bike and it really is the perfect commuting (or even all-rounder) bike.

You are right that each chainset has to be fitted with a specific BB type, but there are many types of BBs.

 

[Shut Up Legs]

You are right that each chainset has to be fitted with a specific BB type, but there are many types of BBs.

I know, I just mentioned those two because they seem to be the most commonly-used. But I'm no expert, hence this thread .

 

[fossyant]

Why not a set of new chain rings (keeping the cranks) ? Some decent ones will be lighter than the current Sora ones. E.g. stronglight

 

[jarlrmai]

keep the cranks get new rings ++

 

[accountantpete]

The Ultegra will be fine as will a 10 spd chain (they just made the outeside of the chain a bit thinner and kept the internals more or less the same).

You just need to make sure your BB is 68mm wide (it should be). You can use any Shimano Hollowtech BB with the Ultegra cranks so the 5700 should be ok - stick your fingers in it and turn the bearings when you disassemble to make sure the bearings are still ok as it looks like the bike has seen a bit of action!