Replacing Tiagra Crankset with Stronglight

[Boogaloo]

I have Tiagra compact crankset with external BB on my winter bike and it's time to replace the BB and possibly the 50T chainring.
Now I could replace like for like but am very disappointed with the external BB which only managed 2 x winters. Also spare Shimano chainrings are expensive if available at all. So I am looking at 2 options....

1 - Replace 50T ring with alternative such as Stronglight Dural and fit a new external BB *
2 - Buy Stronglight Impact chainset 50/34 and fit Shimano UN55 which in my experience is a much better BB. **


* Am I correct in assuming that a Dural chainring will work on Tiagra Cranks - both 5 arm 110mm bcd?
** Am I correct in assuming that my BB shell is suitable for either internal or external BBs?


Any thoughts??

[LollyKat]

* Am I correct in assuming that a Dural chainring will work on Tiagra Cranks - both 5 arm 110mm bcd?
** Am I correct in assuming that my BB shell is suitable for either internal or external BBs?

If the BCD is the same the chainring should fit. You could pay a bit more and get a Zicral ring which is more durable than Dural. (TA last even longer but are significantly more expensive).

The BB shell is probably suitable but you should measure it first. What is the bike, and are there any model markings or dimensions on the external BB? If you can fit a UN55 it would last far longer than any external BB.

Note that on some Impact chainsets one of the bolts is 'hidden' behind the crank arm, and need the correct bolt set which includes a captive bolt.

[meic]

You should mention which bike you have, if it is a CF frame then it may use the push fit bottom brackets like BB30s and I dont think they are suitable for internal BBs like the UN55 but I have no experience of them.
I agree if you managed to wear out the 50t ring, you obviously favour it and a Zicral would be a better option than a Dural.
I always use dural outer rings because I favour the other rings and my outer rings last forever, even though they are dural.

Tiagra external bottom brackets can be very cheap and it is certainly less outlay in short and medium term to just replace the ring and bottom bracket. I get a good life out of my Tiagras by opening them up and replacing the grease with waterproof grease but I guess that it a bit too much hassle for most people.

[Boogaloo]

Sorry yes I should have mentioned that it's an aluminium frame with threaded BB shell.

I have opened up the Tiagra BB and cleaned and regreased it although all a bit late as the damage had been done.

[Perthrider]

Tiagra bottom brackets are available widely for around £10. That's pretty cheep for 2 winters use!

[TrevA]

I replaced my Tiagra chainset with a Spa XD2, which is very similar to a Stronglight, although mine were both triples. I had to slightly tweet the front mech but all was otherwise ok. I originally fitted a Stronglight BB, but it only lasted a year and I changed to a Shimano UN55, with no further problems. The Spa has been OK for about 4 years but the middle ring now needs replacing.