Bottom bracket replacement

The place for discussions on what piece might fit where, where to buy it from, how to fit it, etc.

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Matt
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Bottom bracket replacement

Post by Matt » Fri Mar 23, 2007 21:52

The Lansdown ride seems to have been too much for my BB, which has now got a bit of play in it as well as sounding unwell. Its an ISIS type (Truvativ Giga pipe) which, judging from the internet, seems to be a fundamentally bad design almost guaranteed to have a short life due to the small size of the bearings used as a consequence of having a bigger spindle.

Any recommendations for a replacement? Should I go the simple route and just replace it with another standard ISIS type, but maybe a more expensive one in the hope that it lasts longer?

Or go for a BB with external bearings, which would then mean replacing the chainset too?

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Adrian
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Post by Adrian » Fri Mar 23, 2007 22:05

Matt

Rob is the man to answer this one. I think bigger guys are more likely to gain from the external BB so that would suit but is an expensive option due to the chainset issue - i think i would go for a cheap BB and then go for an external when I needed a new chainset. Ian has trashed a few so his advice might also be good

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Ian Long
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Post by Ian Long » Sun Mar 25, 2007 16:05

My experience was that it really didn't matter how much you spent on an ISIS bottom bracket, it was never going to last very long. I think I got through 5 in the 2.5 years I had the hard tail. The most I ever spent was £80, the cheapest £20. They all seemed to last about 3 months of riding 1-3 times per week. The shortest life I got was 4 weeks, this last one lasted a whole year - about 6 months on the hard tail then a further 6 months when I transferred it onto the full sus. It was a mid range Race Face - I think around the £40 mark. I have its remains lying on the side in the garage, so will have a look in a minute and let you know.

3 different bike mechanics have told me that the ISIS will never last very long because of the size of the bearings, so I would suggest you bite the bullet and go for an external - which will mean changing the whole lot as you suggest.

I have just fitted a Shimano LX Hollowtech from Chain Reaction for £75 which I know you have been looking at. I swapped the chain rings from my existing chainset, so didn't have any risk of worn rings etc and will fit the ones that came with it later when my own wear out (mine were only new last November at Steve's 50th). Fitting the external BB was dead easy - although you do need the appropriate BB spanners. I now have the socket to remove your old ISIS and the spanners etc to fit the external if you need to borrow them....

Hopefully that will be the last time I need to replace my BB for a year or so. That said, Neroli has worn out the external BB on her "new" full sus already, yet in the entire time she had her hard tail, she never wore out a single one. :???:
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Ian Long
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Post by Ian Long » Sun Mar 25, 2007 17:38

Previous BB was a FSA Platinium Pro £35 on Chain Reaction
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Matt
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Post by Matt » Mon Mar 26, 2007 23:03

Thanks for the info Ian. You've saved me from splashing out on an expensive BB in the hope that it would be better. I forgot to tell you I've rounded off the internal hex socket on one crank bolt, so I'll either be butchering it myself or taking it to a bike shop. As Adrian says, it probably makes sense just to change the BB for now until the chain rings get more worn.

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Post by Matt » Fri May 04, 2007 21:53

Update - new BB now in. It's a standard ISIS so I can continue to wear out the existing chainset. It took me a couple of sessions with a drill and Dremmel thingy to drill & grind the head of the crank bolt off but it came apart in the end. I've treated myself to some new flat pedals too as an experiment. Hopefully the experiment won't involve too much shredding of my legs by the 'aggressive' pins on them. :???:

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Post by Al Donald » Sat May 05, 2007 08:20

Matt wrote: I've treated myself to some new flat pedals too as an experiment. Hopefully the experiment won't involve too much shredding of my legs by the 'aggressive' pins on them. :???:
That's why we all wear leg armour!

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Post by NigelP » Sat May 05, 2007 13:18

As a post script. If you do ever switch to external bearings you may need to have the socket on the bike machined by a bike shop, so the bearing seats properly. Fitting the new crank after that is easy (and I also have set of the spanners if required.)

Also. If you are concerned about the wear on the Shimano external bearings then BETD (https://www.betd.co.uk) will fit an oversize set for you. Same price as Shimano, but you need to send in an old Hollowtech 2 bearing to be refitted. They also supply a sexy Hollowtech crank bolt that replaces the plastic Shimano one and fits with an Allen key instead of the bespoke tool. :D

I found that the flat pedals were just the start. I ended up buying new shoes as well. :cry:
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