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A little bottom bracket help please....
http://www.retrobike.co.uk/forum/viewtopic.php?f=41&t=402462
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Author:  Hovis_loaf [ Wed Sep 11, 2019 11:28 am ]
Post subject:  Re:

Well the last few posts have confirmed what I thought to be the case, thanks to you all for all the info.

I am now wondering if there is a "simple" engineering solution to this. If the biggest problem is the support of the bb in the frame, or the lack of it, if a 68mm unit is used would a longer cup on the non-drive side solve it? The thread in my frame is 27.9mm deep and the current cup is 21.7mm including taper, so that would take care of the 5mm difference.

Now please don't laugh but I done a little sketch of my thinkings. If it would work i am not sure how to best "extend" a cup are different lengths available, I can't find any info on them if they are. I could just use the band saw and create a simple mechanical joint, a step would do it. The advantage of that over brazing would be that each piece could find its own way so to speak, brazing it so the threads match spot on I think would be very very difficult.

Whats fink???

Please feel free to tell me I am idiot, it may be the first of many idiotic things I do/say in my 40's!

Attachments:
BB Sketch.png
BB Sketch.png [ 12.77 KiB | Viewed 303 times ]

Author:  Madmax1993 [ Wed Sep 11, 2019 11:55 am ]
Post subject:  Re:

This seems far more complicated than just getting the correct bottom bracket for the application. It'd even be simpler to swap the chain set for a square taper unit for which you can still get all the different combinations of BB if your old hollow tech one is hard to come by.

Author:  Hovis_loaf [ Wed Sep 11, 2019 12:27 pm ]
Post subject:  Re:

I agree, but I am cant find an exact replacement. Also I don't want to change my cranks, they've been on the bike for the last 19 years!

Author:  Hovis_loaf [ Wed Sep 11, 2019 1:35 pm ]
Post subject:  Re:

One thing I haven't done which I probably should have, maybe first, is ask if anyone here has one they would part with for the appropriate amount of beer tokens!

Author:  jimo746 [ Wed Sep 11, 2019 2:06 pm ]
Post subject:  Re:

Just remove the old bottom bracket, and buy one exactly the same :lol:

For the old type square taper cartridge bottom brackets, if your frame has a 68mm BB shell get a 68mm BB, if it's a 73mm get a 73mm.

The axle length is determined by the cranks you want to use, there's lots of different ones. But if you're keeping the same cranks then just get a BB with the same axle length as the current one (or look up the recommended axle length for your cranks)

Only 2 things to remember...

BB shell width.

Axle length.

Author:  Hovis_loaf [ Wed Sep 11, 2019 2:32 pm ]
Post subject:  Re: Re:

jimo746 wrote:
Just remove the old bottom bracket, and buy one exactly the same :lol:

For the old type square taper cartridge bottom brackets, if your frame has a 68mm BB shell get a 68mm BB, if it's a 73mm get a 73mm.

The axle length is determined by the cranks you want to use, there's lots of different ones. But if you're keeping the same cranks then just get a BB with the same axle length as the current one (or look up the recommended axle length for your cranks)

Only 2 things to remember...

BB shell width.

Axle length.


I wish I had thought of that!! ;-)

....if you could point me in the direction of one that would be great, I'll buy two!

Author:  Hovis_loaf [ Mon Sep 16, 2019 11:24 am ]
Post subject:  Re:

Well I have found one........but I think if I spend over £100 on one the wife may kill me!!!

https://www.ebay.co.uk/itm/NEW-SHIMANO- ... SwoHhdfV0t

Author:  jimo746 [ Mon Sep 16, 2019 11:33 am ]
Post subject:  Re:

:facepalm:

Author:  Hovis_loaf [ Mon Sep 16, 2019 11:57 am ]
Post subject:  Re: Re:

jimo746 wrote:
:facepalm:


If it was just the £96 quid I would have been tempted, it is the extra postage and then is there going to be any import duty?? The one I have is serviceable and a mate of mine this morning said that you can get them apart, he did it once many moons ago.

But what do I do when this one dies? These are the only ones I have found after nearly two weeks of looking!

Author:  Madmax1993 [ Mon Sep 16, 2019 12:26 pm ]
Post subject:  Re: Re:

Hovis_loaf wrote:
jimo746 wrote:
:facepalm:


If it was just the £96 quid I would have been tempted, it is the extra postage and then is there going to be any import duty?? The one I have is serviceable and a mate of mine this morning said that you can get them apart, he did it once many moons ago.

But what do I do when this one dies? These are the only ones I have found after nearly two weeks of looking!


Ditch the obsolete standard and get a new chainset. It's one thing to be attached and keep a bike standard, but sometimes you just have to let it go. It not like it's an old xtr chainset, it's only a specialized OEM item.

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