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Changing type of bottom bracket
#1
Ok so I've been wanting to replace my crankset for a while and I've finally gotten myself into looking at some online. However the ones that I'm seeing that I like are all either Hollowtech, ISIS, or Octalink. I have a square taper sealed cartridge. So my question is, is it possible to switch the type of bottom bracket I have with a different one?

The bottom bracket size I have is 73x122.
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#2
Yes you can fit any of the "newer" BBs in place of your current square taper.
I think that some come with a spacer that allows for the difference between your 73 and the more normal 68mm shell size.
Different chainsets may need different overall lengths of spindle compared with the 122mm that yours is.
If you can, ask the supplier for the recommended matching BB'.

As you may have noticed the latest designs come with the spindle as part of the chainset so all you have to do is fit the "external" bearing housings.
[font=Trebuchet MS]Ride hard or ride home alone![/font]
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#3
Ok I'll look into that. Are there any pros and cons to each of them that I should know about?
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#4
(02-20-2011, 04:45 AM)nameused Wrote:  Ok I'll look into that. Are there any pros and cons to each of them that I should know about?

All my bikes, except one, are square taper. I have one bike with Campag' outboard bearings. I have no experience of the other formats.
The outboard bearings type have had mixed reviews with some not lasting long. The instructions for these type of bearings say to have the shell ends faced to make sure they are square. Whether this makes any real difference I don't know.
I wouldn't go using a high pressure washer on them.
[font=Trebuchet MS]Ride hard or ride home alone![/font]
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#5
As CyclerUK says, keep the pressure washer away!

I'll run through a little list of pros and cons:

Square taper:
Pros: lasts ages, cheap.
cons: not strong enough for serious MTB applications (fine for road), could be lighter

ISIS:
This evolved from square taper for MTBs. The idea being that these provide a much stronger axle for harsh treatment by MTBers. Octalink is pretty much the same, apart from a different crank interface.
Pros: stronger than Square Taper, not too expensive
cons: HEAVY, bearings last about 30 seconds.

Hollowtech, X-Type, etc.
An innovation that sought to deal with the problems of ISIS but keeping the same strength.
Pros: much stronger, reasonable bearing life, lighter than most, some BBs can have replacement bearings fitted
cons: not exactly cheap.

Of course the above are general guidance, and there are some grey areas. Hollowtech can trump Square taper for road, as they CAN be made lighter than any square taper setup (though these may cost a lot of money). The advantage of a hollowtech over a square taper is that you can get high strength (as in do 20ft drops to flat) with low weight. Of course you won't be doing that on a Road bike so a lot of the advantage is lost until you get to full carbon cranksets, etc.

With hollowtech BBs the quality will vary from manufacturer and price point. For instance, RaceFace BBs don't last that long compared to even the cheap shimano ones. Hope ones can last years.
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#6
(02-20-2011, 09:36 PM)JonB Wrote:  As CyclerUK says, keep the pressure washer away!

I'll run through a little list of pros and cons:

Square taper:
Pros: lasts ages, cheap.
cons: not strong enough for serious MTB applications (fine for road), could be lighter

ISIS:
This evolved from square taper for MTBs. The idea being that these provide a much stronger axle for harsh treatment by MTBers. Octalink is pretty much the same, apart from a different crank interface.
Pros: stronger than Square Taper, not too expensive
cons: HEAVY, bearings last about 30 seconds.

Hollowtech, X-Type, etc.
An innovation that sought to deal with the problems of ISIS but keeping the same strength.
Pros: much stronger, reasonable bearing life, lighter than most, some BBs can have replacement bearings fitted
cons: not exactly cheap.

Of course the above are general guidance, and there are some grey areas. Hollowtech can trump Square taper for road, as they CAN be made lighter than any square taper setup (though these may cost a lot of money). The advantage of a hollowtech over a square taper is that you can get high strength (as in do 20ft drops to flat) with low weight. Of course you won't be doing that on a Road bike so a lot of the advantage is lost until you get to full carbon cranksets, etc.

With hollowtech BBs the quality will vary from manufacturer and price point. For instance, RaceFace BBs don't last that long compared to even the cheap shimano ones. Hope ones can last years.

Haha I don't have a pressure washer so I don't have to worry about that. Tongue
The riding I do on my mountain bike is kind of a mix between road and mountain. I ride medium to light trails, but then can easily ride on the road for a long time and at an "amazing speed" as my friend with a road bike said yesterday.
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#7
Fair enough.

Have a look into something like a Shimano Deore or LX hollowtech crankset then. They're light and surprisingly strong for budget cranks, and the BB will fit just fine.

With hollowtech cranks, the 68/73mm model has a fixed spindle width, you just simply add or remove spacers between the BB and BB mount (supplied normally) until it works (for 73 it's normally just one on the drive side, 68 it's 1 on non-drive, 2 on drive).

I'd either stick with square taper if you can find something suitable and cheap, or just grab a set of the above cranks or similar.
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#8
(02-20-2011, 09:36 PM)JonB Wrote:  ISIS:
This evolved from square taper for MTBs. The idea being that these provide a much stronger axle for harsh treatment by MTBers. Octalink is pretty much the same, apart from a different crank interface.
Pros: stronger than Square Taper, not too expensive
cons: HEAVY, bearings last about 30 seconds.

Really? I guess I'm pretty luck then. I bought my 2005 Felt F65 used last year, with the original ISIS BB. I put in about 6,500 miles in addition to the near 600 I already have for this year - much of it on slushy, salty winter roads - and it has yet to show any signs of wear. Smile
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