shimano tiagra 4500 crankset

[andy h]

Can someone please advise me I have a shimano tiagra 4500 double crankset on a trek can this be swapped for a tiagra 4500 triple instead.Can I use the same bottom bracket? Is there anything else that I would need to replace.

Regards
Andy

 

[alecstilleyedye]

you need:

new 130mm bottom bracket
new l/h shifter
new front mech
and, possibly, new rear mech

having been through this process myself, i found it was cheaper (at the time) just to buy a complete new groupset.

 

[andy h]

The left hand front shifter is already capable of running a 3 gear front crank the bottom bracket is the real thing I am unsure of as I do not know if the spindle on the triple is the same size. Is it an easy job to do or am I better off getting a shop to do it
Regards

 

[alecstilleyedye]

ok, in which case you will still need a bb and front mech, at the least. if the front mech is band on (and not a brazed on fitting), you need to make sure you get the right one for the thickness of the frame tubing (alu is commonly 27.2mm, but check to be sure).

changing a bottom bracket is easy - if you have the tools; crank puller and bottom bracket tool with large adjustable spanner and allen key.

if this is a one-off job, i'd recommend a reputable local bike shop to do it, otherwise get the tools and do it yourself. if you're a member of a cycling club, you might get lucky and be able to borrow the tools…

 

[andy h]

Thanks
Andy

 

[kyuss]

Is the Tiagra 4500 not Hollowtech? If so then the BB won't be an issue as the chainline and chainstay clearance will be dictated by the length of the axle on the crank itself. You should be able to just swap the cranks and use the same BB.

 

[PpPete]

I've got a Tiagra triple - with a splined crank/BB ....I thought it was 4500 series (but I could be wrong)
The latest ones certainly seem to be Hollowtech II

 

[andy_wrx]

Shimano tech docs exploded views of FC4500 double and 4503 triple
http://techdocs.shimano.com/media/t.../FC/EV-FC-4500-2593_v1_m56577569830608861.pdf
http://techdocs.shimano.com/media/t...FC/EV-FC-4503-2594B_v1_m56577569830683052.pdf

Looks to me like the bottom bracket itself (it's an external by the way, not a square taper unit like the earlier 4400 versions) is the same - the same part numbers for the individual bits : parts 5-9 on the double cf 5 & 7-10 on the triple

But note how the triple has the two spacers - parts 6 & 11...
- that's how they get the chainline : the righthand crank obviously has a longer axle and you need these extra spacers external to the BB cups.