What Crankset / chainrings and BB

[Seweryn]

Hi Guys,

The bike is currently equipped with the following (Shimano 105 7-speed) crankset:

I am currently upgrading the wheels and the cassette (that comes with the wheels) to Shimano 8-speed system. I have also bought the 8-speed downtube shifters (7400-series) and now is the time to upgrade the crankset and the BB.
The main reason for the upgrade is the original wheels are 126mm at the rear hub, but the frame is 130mm.

I have a few questions and I appreciate your help:

- What is the BCD of the chainrings on my bike (if I want to "downgrade" the chainrings only)? I can't measure it myself, as the bike is overseas and I ride it only when I am away on holidays. The rings on the cranks are 42/52T AFAIR and are too large for me. I would prefer something like 36/50T or 39/50T.
- What other crankset would fit there, preferably with 165mm arms (the current one is 170mm)?
- What width should be the BB axle for a Shimano crankset like this one? The bike is Italian, so believe it has an italian BB.
- Am I right thinking that the current 105 rear derailleur will work with an 8-speed cassette / shifters?

 

[Seweryn]

Any help Guys?

 

[mattsccm]

BCD will probably be standard Shimano 130mm.
I think the smallest that fits might be a 38 although 39 is standard on a conventional chainset.
Smaller than that means either a modern compact with 110BCD and 34 minimum or something European eg a Stronglight. which can have all sorts of options.
Have a look at Sheldon Brown and search for BCD.
Haven't a clue what BB should be but I find that so called correct ones don't always work as well as other. . Depends on the frame as well in some cases.
I would find a chainset, try that and go from there.

 

[oonaff]

ive been wondering whether all of these were made in italy and japan i read the otherday so im wondering [thaiwan ?] anybody know
what is the tubing ? sorry its abroad.
are you certain its an italian thread bb ?
when they say 'hand built in ' sometimes that means they just assembled it there .
im interested in your conclusions so when youve done what you want please mention in this thread.
bianchi s intrigue me they just made such a massive range i was always put off by the newish ones [1990/s]because my mate got a new one and the frame alignment was poor.

 

[Seweryn]

ive been wondering whether all of these were made in italy and japan i read the otherday so im wondering [thaiwan ?] anybody know
what is the tubing ? sorry its abroad.
are you certain its an italian thread bb ?
when they say 'hand built in ' sometimes that means they just assembled it there .
im interested in your conclusions so when youve done what you want please mention in this thread.
bianchi s intrigue me they just made such a massive range i was always put off by the newish ones [1990/s]because my mate got a new one and the frame alignment was poor.

Regarding your questions:

- The tubing is Columbus SLX,
- I can't imagine this being non-Italian BB, but not sure.
- I believe it is made in Italy. It is the Specialissima X4 model from the late '80s.

 

[pigman]

Its an Italian Bb. I had one of those frames. I liked the style of Moreno Argentin so got the bianchi. The frame is nickel parted u!nder the paint. I got rid of it as it was too difficult to keep clean. Dirt just seemed to smear around rather than wash off.

 

[gazza285]

I'd be tempted to keep the chainset, you can get a 39 tooth sprocket on there, and go for an 11 - 28 cassette on the back. It's what I run on my Vitus and I can get around the Pennines easily enough, some hills take a bit of muscle, but it's boring if it's too easy.

The rear mech will work with 8 speed, no problem.

 

[Seweryn]

Thanks.

Just by the way, are these 7-speed chainrings (if I keep them) going to work with 8 or 9-speed chain?

 

[pigman]

Yeh, no probs. My winter bike has a 7 speed Deore chain set with original biopace rings running 10 speed chain and cassette.