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 Post subject: BB help
PostPosted: Wed Apr 01, 2020 12:59 pm 
Devout Dirtbag

Joined: Wed Jan 29, 2020 10:49 pm
Posts: 109
Hi all!

So I bought a GT Xizang (1995) Im in the process of adding the cranks, KOOKAs. When i got them on there was no clearnace on the chainstays.

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I was thinking that the BB spindles were too short as looking at another BB from another bike ive stripped they were further out. Please see images.

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My resoloution was just to swap the two out! as heres the clearance on the other frame with the BB I was intending to fit Problem is my Shimano tools dont seem to fit!

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Does anyone know if my plan is the correct one to take or perhaps are my chainrings just too big for this frame? also anyone know what BB this is? is it a GT, colenago etc it look Ti

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 Post subject: Re: BB help
PostPosted: Wed Apr 01, 2020 1:59 pm 
Old School Grand Master

Joined: Tue Oct 09, 2007 1:55 pm
Posts: 10055
Location: New Forest, UK
You have to match the BB length to the crankset. Depending on the type it could be something between 118 and 122mm.

I have no idea what BB that is, but it looks short.


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 Post subject: Re: BB help
PostPosted: Wed Apr 01, 2020 2:16 pm 
Devout Dirtbag

Joined: Wed Jan 29, 2020 10:49 pm
Posts: 109
How would I find out what bb size I would need? I have a kooka crankset c.1994-7

Also did Bottom brackets have different diameters? So I can keep an eye out for


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 Post subject: Re:
PostPosted: Wed Apr 01, 2020 2:50 pm 
Retro Guru

Joined: Wed Apr 03, 2019 4:25 pm
Posts: 256
Had to deal with this recently... like mentioned above, matching is important

In my case I had an lx crank and xt crank long and short bottom bracket... long only worked with xt and short only worked with lx... a weird comparison would be people putting incorrect rims on a car with different offsets


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 Post subject: Re: BB help
PostPosted: Wed Apr 01, 2020 3:21 pm 
Retro Guru

Joined: Tue Aug 21, 2018 3:43 pm
Posts: 783
Location: Cambridgeshire - flatlands (the horror, the horror)
Spud - a few things need to be considered together.

Firstly, I play with BB axle length all the time to get a low Q factor.

The Q factor is the distance between cranks - good to have that the same as the natural fall of your legs. Places less strain on knees - very important. On some frames this can mean using an axle MUCH shorter than that recommended.

How can you check your Q? By installing both cranks on so that one is 180 deg out - ie they weirdly are together, but that means you can at the same time look at the clearance each side between crank and chainstay. Sometimes you can improve the chainline and get the clearance you need on the chainrings by installing bb washers (like on HOPE bb) on the drive side. This effectively moves the whole BB over to one side. That may seriously misalign the non-drive side - or...as it has done for me on occasion...actually brought everything into alignment.

For instance - I have run a Kona with a 104 Hope ti BB when the recommended bb is 122!! And the 120 gave crazy-wide Q with a HUGE clearance on each chainstay.

You need to play.

But as you say...first you need to get the BB out, and the shimano tool does not fit. I’ve never seen that fitting before, and there have been instances of boutique BB manufacturers bringing out fittings with their own tools included with it. Which is a pain when later you get a bike without the tool. I had a thought that it might be a cassette tool pattern but i have just checked and it isn’t. It isn’t campag either. I am searching further....


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 Post subject: Re:
PostPosted: Wed Apr 01, 2020 4:36 pm 
Retro Guru

Joined: Tue Aug 21, 2018 3:43 pm
Posts: 783
Location: Cambridgeshire - flatlands (the horror, the horror)
Argh should also have said that BB tapers vary of course, forgive me if you already have thought of that. There’s JIS, JIS short taper, and ISO. The late great Sheldon Brown’s endlessly useful website helps explain. They are roughly compatible, but the cranks will sit in a different position on the taper and could give the issues you have. Take a look at the SB website.


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 Post subject: Re:
PostPosted: Wed Apr 01, 2020 4:56 pm 
Devout Dirtbag

Joined: Wed Jan 29, 2020 10:49 pm
Posts: 109
Guys your wisdom is invaluable to me! thank you all so much, really appresiate the help most of these componants are older than me and the knoledge about them is so scattered it really helps to have someone whos knows their stuff telling me :D


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 Post subject: Re: BB help
PostPosted: Wed Apr 01, 2020 5:18 pm 
Retro Guru

Joined: Tue Aug 21, 2018 3:43 pm
Posts: 783
Location: Cambridgeshire - flatlands (the horror, the horror)
Sorry more

If it’s ti I hope they put it in with plenty of slop - copper grease - or the ti will bind like crazy on the alloy threads.

It’s not a standards GT ti bb of the time since that was standard shimano splines and JIS taper.

Hmmm....I wonder:

https://www.bricklanebikes.co.uk/phil-b ... ation-tool

I did think ‘Phil woods’?


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 Post subject: Re: BB help
PostPosted: Wed Apr 01, 2020 5:32 pm 
Retro Guru

Joined: Tue Aug 21, 2018 3:43 pm
Posts: 783
Location: Cambridgeshire - flatlands (the horror, the horror)
GOTCHA!!!

https://bmxmuseum.com/forsale/298174

Even got the same weird pink bearing seals.....


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 Post subject: Re: BB help
PostPosted: Wed Apr 01, 2020 5:33 pm 
Retro Guru

Joined: Tue Aug 21, 2018 3:43 pm
Posts: 783
Location: Cambridgeshire - flatlands (the horror, the horror)
Phil Woods were a very common high end upgrade to GTs


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