"Outboard Bearings"?

[biking_fox]

Anybody able to explain in simple language what "outboard bearings" on a chain set are?

Apparently my only a few years old tiagra group set has parted company somewhere and the LBS is having trouble replacing it because the new designs are all 'outboard'. This was over the ohone so I'm a little confused as to what's broken and where the problem is.

 

[Amanda P]

Ah - that'll be one of these new-fangled bottom bracket/chainset assemblies.

Instead of having the bearings inside the bottom bracket shell, as God intended, the bearings are in shells on the ends of the bottom bracket. This means they're further apart and therefore better able to withstand the torque of pedalling.

I believe they come in lots of different types, too, depending on the type of chainset - some have hollow axles, octagonal splines etc.

Apart from that, I can't be much help because I don't know much about these designs.

(It sounds a bit like your setup had a common-or-garden square taper, internal bearing bottom bracket, and the bikeshop wants to fit a new outboard bearing one, with associated chainset. If this is true, there's really no need - there are plenty of chainsets available that fit on perfectly serviceable square-taper cartridge bottom brackets - which, though heavier than some newer types, have never had an epidemic of catastrophic failures).

 

[Chris James]

What Uncle Phil says.

Depends if you want to use the failure as an excuse to 'upgrade'. The bike shop should be able to sort you out a decent replacement to fit your existing bottom bracket though. Maybe he just meant that new Tiagra wouldn't fit on?

 

[biking_fox]

It was either upgrade, seriously upgrade or downgrade.

The LBS didn't have any old style chain sets in, but could have got hold of some - which would be a downgrade from the tiagra. They had Ultegra new style sets in stock at least twice the price of my existing version!

I've told them as the alternative involves buying stuff in anyway, to order in a new tiagra, upgrading to the new style but not massively more expensive. However it means the bike won't be ready to pick up today

I wonder how long I'd been riding with a broken part? It didn't feel wrong!

 

[piedwagtail91]

if the cranks aren't broken / damaged then it should be a simple and cheap job of a new bottom bracket, these can be got for around a tenner.
it the problem is with the cranks the yes it may be difficult to get replacements, though stronglight do still make square taper.
find out what the problem is before handing over any money.

 

[alecstilleyedye]

if it's nine speed tiagra, it has an octalink bottom bracket. these are available from wiggle, ribble and others. be sure to order the longer one if you have a triple chainset.

 

[GilesM]

This link shows with a few drawings all about external bottom brackets.

http://www.raceface.com/comp/inst/DeusCrankset.pdf

Hopefully it explains it quite clearly, the benefit is that the bottom bracket and spindle are much lighter, however some are not exactly long lasting.

Giles

 

[Smokin Joe]

Your LBS response shows why bike shops are closing in droves. Five minutes trawling the net, as Alecthingy suggests and you would have one in the post to you the same day.

 

[simonali]

Sounds more like BS than LBS! As stated, if all that's needed is a new BB and they're trying to flog you a new chainset to go with it then find another shop.

 

[biking_fox]

Thanks for that link GilesM that's just what I was looking for.

re the LBS: No they aren't "flogging" me an outboard, they were quite happy to get hold of some old style chainsets, but they didn't have any in stock - being primarily a roadbike shop, and as all new roadbikes? seem to be on this design this makes sense. It's part of the "spider"? that's broken I think. I'll certainly be asking for the details when collecting the bike.

Were that I had a wide chioce of LBSs to choose between! I could entrust my bike to the guys at Halfrauds and hope I got the one who knew what he was doing. I have no desire to get a chainset sent to me, I don't wish to, have skills or the tools to, take it apart. The LBS have been a good, fast efficiant and not overpriced in the past and they phoned me to check what I wanted to do.

 

[GilesM]

Thanks for that link GilesM that's just what I was looking for.

No problem, it's worth remembering that quite a few of the component manufacturers do put alot of stuff like this onto their websites, Hope, Shimano, Raceface are all pretty good.

Giles