Changing a crankset

[robgul]

I have a customer with a 3 x 9 speed set up (Sora mechs & shifters) - with a Spa own brand basic square taper crankset/rings (44-34-24). He's gone through 3 cartridge bottom brackets in about 6,000 miles (First Components DX30*) . . about half the mileage loaded for touring/camping.

Seems to me that fitting a "modern" external cup BB would be beneficial - but that would require a crankset set with an axle. Nothing readily available with the rings and 175mm cranks (he's a very tall bloke)

I've found this https://bankruptbikeparts.co.uk/pro...organic&utm_campaign=sag_organic&gad_source=1 - rings are close enough.

Question: will this crankset work with the Sora mech and shifters? (Fitting a Shimano 24mm axle threaded BB rather than work-of-Satan pressfit)

I can't see why it wouldn't . . . 9 speed chain is whisker wider than 10 speed (searching suggests no issues from users) - the cassette would be unchanged as 9 speed 11-34.

The existing chainrings are close to needing replacement so the cost aspect isn't too horrendous.

• this BB seems to have dubious reports and reviews? It seems that the old favourite Shimano UN55 has been discontinued and reports on its successor aren't brilliant.

 

[I like Skol]

If you think square taper bbs from Shimano are not great then heaven help you if you swap to a hollowtech bearing setup. Please tell me what you have read that suggests this will be an improvement in this case?

 

[wafter]

Balls.

 

[robgul]

If you think square taper bbs from Shimano are not great then heaven help you if you swap to a hollowtech bearing setup. Please tell me what you have read that suggests this will be an improvement in this case?

1 Experience - managing an LBS
2 Bearings are further apart and thus better support the axle
3 Bearings are better quality (and can be upgraded to even better) [. . . and yes you can swap bearings in most external cup BBs with the right tools)
4 Experience - with my own fairly high-mileage bikes

 

[fossyant]

Nope, External bearings are no where near as long lasting as square taper. Go shove in a UN300 - I've done two years commuting on mine (with a triple) and it's as smooth as butter. Shame GXP needs new bearings/re-greasing on a regular basis. FSA Mega Exo isn't much better.

The UN300 is fine TBH. Just change the BB for £15.

 

[fossyant]

PS I've done the bearing upgrades on GXP - they are still in the firing line of crud off the front wheel (tested in extreme MTB conditions)

 

[I like Skol]

1 Experience - managing an LBS
2 Bearings are further apart and thus better support the axle
3 Bearings are better quality (and can be upgraded to even better) [. . . and yes you can swap bearings in most external cup BBs with the right tools)
4 Experience - with my own fairly high-mileage bikes

1, In that case why are you asking us?
2, In theory yes, but all the manufacturers have targeted cost and weight savings, so the possible mechanical improvements are more than undermined by the sacrifices made to reduce weight and cost of production.
3, Shimano hollowtech bearings are woefully inadequate and typically give a short service life. Replacement of the bearings is possible (I've done this) but you are still stuck with questionable quality bearings that are still of an inadequate rating for the job. For some reason Shimano also spec a bearing 1mm narrower than the industry standard for that size so you REALLY struggle to get replacements.
4, can I ask what bb you are running to achieve this? I have had some luck with a praxis unit which seems well made, takes sensible bearings and is easily rebuilt, but Shimano versions have been lucky to do much more than 2-3000 miles typically (obviously there is the odd set that bucks the trend, but that's rare).

 

[I like Skol]

The UN300 is fine TBH. Just change the BB for £15

^^^This.

 

[I like Skol]

Or there are still some NOS UN55s around in certain sizes.

 

[fossyant]

I run a Praxis GXP which is much easier to replace bearings than the SRAM version. But the bearings do cost me about £20 a pair for decent ones. I have a really old UN71 and a UN91 that have never been touched, other than removed, frame checked, and shoved back in.

One advantage with sticking with Square Taper and the SPA chainset, is I bet it's running standard BCD pattern, so chain rings are readily available. The problem with shifting to the likes of Shimano/SRAM, is their insistence on specific BCD's and expensive chainrings as a result.

I would have thought a touring bike needs to be more generic, just in case parts fail mid tour - easier to obtain replacements.

 

[robgul]

I should have said that the customer is keen to escape the Spa kit (long, sad story) hence looking at alternatives whilst maintaining the ultra-low gear ratios.

What foxes me is how he manages to wreck the cartridge BBs - he's tall, thin and pretty fit - and seems able to put a lot of power into pedalling. The bike is usually very clean and gets dried etc after bad weather (it's a Ti frame). Perhaps he's just unlucky with the BBs?

 

[chriswoody]

This is the UN300 that I replaced a few weeks back, from my folder after 6 months winter commuting and general knock about riding. My commute is only 6km, so in total this BB has probably done 600km. The last one didn't last too long either, in my experience the UN300 is utter rubbish, nothing like as well built as the old UN55.

The External BB's on my Gravel and Mountain bikes are used all year round in filthy conditions and last an absolute age.

Just my experience.

 

[Punkawallah]

Slather the BB in grease? i had a Boardman hybrid that had a similar problem. Slathering the ends in grease seemed to help with water ingress.

 

[ColinJ]

PS I've done the bearing upgrades on GXP - they are still in the firing line of crud off the front wheel (tested in extreme MTB conditions)

I killed a BSA30 road BB in 2 months this winter! It only lasted a few hundred km. That's probably because I don't have mudguards on that bike so the external bearings were subjected to near constant salty, gritty spray.

 

[fossyant]

I suspect you've got water getting into the frame - mine looks nothing like that after 2 years !