Bottom bracket, square taper upgrade?

[drcarlos]

Re: Re:

To answer your question: no, it isn’t possible to upgrade from square taper as it hasn’t been bettered yet.

Brilliant reply! And considering it feels better at 27/28 years old than my 6 year old hardtails BB it's a valid claim

I think the ISIS standard had a lot of promise. The splined system is certainly better than square taper for ease of removal and has the familiar cartridge type BB axle of square taper. The FSA alpha drive which looks like ISIS has lasted many years in first my father in laws bike and laterly my eldests Kona (and now thats' being rebuilt ready for the younger boy the same BB is again being fitted as it's not worn at all. I've had lots of trouble with external BB's myself but Shimano ones seem better quality that FSA and they are interchangable (shame SRAM/Truvative use other sizes).

 

[Prodigal Son]

The only upgrade i see fit is buying a sq taper Phil Wood BB. Forget Isis and other long forgotten standards which had longevity problems and did not do much to improve sq tapers; go to an external bearing modern shimano xt job.

 

[pat_h]

Just when I thought I'd it all figured out. Are the widths different depending on the cranksets? I.e. a triple is wider than a 1x
Mine was a triple, and i'm planning on keeping it 1x for the rebuild. Looking online its a 68/122 and I should go for smaller for the 1x?

 

[Prodigal Son]

Spindle length is determined by crankset model.

 

[Rank_21]

If your running a single chainset, I hope you've thought about replacing the freewheel/cassette. I believe that's problematique with regards to shifting.

 

[drcarlos]

Re:

When switching to 1x assuming the bb size is correct, you place the single ring where the middle would otherwise be so the chain line isn't extreme at top and bottom sprockets. I've done 3 conversions now, one on external bb, one on ISIS bb, one on square taper. The square taper was the most grief as the ring needed slight modification with a file to fit on the locating lugs on the chainset. Every other one is just bolt and go.

 

[jimo746]

Re:

With square taper bottom bracket yes there are a variety of axle lengths to suit a variety of cranksets to obtain the optimal chainline. Sheldon Brown's page on it is pretty comprehensive. https://www.sheldonbrown.com/bbsize.html
With external bottom bracket e.g. Shimano Hollowtech 2 you can move the spacers around to adjust the chainline if needed.
If you're converting to 1x with that square taper bottom bracket then as said above just mount it where the middle ring would normally fit on a triple crankset (you'll need shorter chainring bolts for the single ring, or some normal bolts + washers).
If you ard going 1x I'd recommend a narrow-wide Chainring (dropping the chain can be inconvenient at best, and ball breakingly bad at worst!). 104bcd 4-bolt rings are probably the most widely and cheaply available, you can get 110bcd 5-bolt ones though.
And as also mentioned my Drcarlos above you may find the new chainring (4-bolt 104bcd) doesn't quite fit on the crank and you need to file down the tabs on the crank a little (I've had this happen a handful of times, different rings fit, others need filing).
Don't worry about the cassette, if it works with 3x it'll work with 1x.(unless youre upgradimg to 11 or 12-speed at the rear or something!).

Simple eh?!

 

[pat_h]

Re:

It's mad how complicated all this is! Thanks for the wisdom.
I may be able to reuse the old 400LX cranks, and a 110bcd Race Face Narrow Wide Single Chainring with a new 73 x 122.5mm BB, I think that's as close to what I have, the BB feels a bit rough so it's as good to swap it out.

 

[jimo746]

Re:

You might get away with just using a regular chainring up front, but in my experience anything much more than hopping off a kerb may cause the chain to drop, and that's just s pain in the ass...