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PostPosted: Fri Jun 08, 2018 3:40 am 
Devout Dirtbag
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Joined: Sun Apr 22, 2018 3:59 pm
Posts: 113
Morning chaps.

3:32am and I cannot sleep because I am stressing over this Raleigh Banana :oops: :lol:

So, bottom bracket.. first word that comes to mind is Eeeekkk!.. I haven't.... Got … A clue :shock:

I have took some pics and hope someone can help clarify if this looks right and what I need so I can get rolling asap.

Ere's me findings:

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So looking at my old BB I have it as the following: Shell - 68.18 mm - I.D. - 33.98 mm - Cup - 34.70 mm - Spindle - 124.37 mm)

I was thinking of staying with square taper bottom bracket and crank and thinking of this as the BB:

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However if I went with the 68 x 127mm wouldn't that put the crankset and therefore chainline out too far? :?:

I then have the worry about the British, English or Italian thread option, I have no idea :|

Finally I was thinking about buying this, maybe you guys can spot if it will / will not work with this bike, size, bottom bracket etc:

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Edit: - I have just seen this info on the crankset:

Product description - Details
Recommended bottom bracket length: 110 mm
Case width: 68/70 mm
Compatible chain: HG 6/7/8 -speed

I guess that will not work if my spindle thing was 124.37 mm?

Any suggestions on what I need to do to get the correct bottom bracket and crankset would be sooo helpful right now. I wonder if a newer bottom bracket and like hollowtech thing would be more compatible? (sigh)

Thanks in advance :oops:


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 Post subject: Re:
PostPosted: Fri Jun 08, 2018 7:40 am 
Dirt Disciple

Joined: Fri Jun 10, 2016 4:11 pm
Posts: 42
bb you bought is much too long. For a double i would expect something from 107-113mm depending on crankset.

Your proposed crank is proof in point but check that is a road crank to maintain chainline as you say.

Good luck


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 Post subject: Re:
PostPosted: Fri Jun 08, 2018 7:48 am 
Dirt Disciple

Joined: Fri Jun 10, 2016 4:11 pm
Posts: 42
Sorry 68mm shell and English threading ok. Make sure you install correctly as drive side is left hand thread.

Un55 is a great choice but you can find less expensive units if you prefer.


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PostPosted: Fri Jun 08, 2018 4:32 pm 
Devout Dirtbag
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Joined: Sun Apr 22, 2018 3:59 pm
Posts: 113
Hey Ray thanks so much for the replies mate.

The bb I had was what was on the bike already and I took measurements from that but I am starting to wonder, are bottom brackets used in conjunction with what chainset you run?

If so, maybe I can run a 110mm spindle and the above crankset on my frame and it be ok? I don't know if that is sound logic or not but it feels right lol :)

I am also wondering that maybe the reason the spindle was so long on the original crank is because of how big the crank arms are and how much the tapered spindle went into it, maybe newer stuff isn't as deep and therefore you can get away with smaller bottom brackets?

OK so looking at the above, am I right in thinking I can go ahead and buy that crankset and get the 107 or 113mm bb as they are both within 3mm of what is required, I guess its best to have more than less and it would be 1.5mm more each side and I ain't even sure if one would notice that?

I feel like I am close to understanding it, but not quite lol. Maybe a hollowtech II bb would work with the correct crank, maybe the shell is the defining factor.

God I hate being new :(


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PostPosted: Fri Jun 08, 2018 6:18 pm 
Old School Grand Master
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Joined: Fri Oct 14, 2011 8:41 pm
Posts: 9314
Location: Cumbria
The top BB with the threads coming out of the axle look like a Sugino Maxy variant. For a modern crankset you need something completely different in length. LFGSS have an unnoficial BB / crankset thread which might give a matching BB for your proposed cranks.


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 Post subject: Re:
PostPosted: Fri Jun 08, 2018 8:05 pm 
Retro Guru
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Joined: Mon Sep 24, 2012 9:10 pm
Posts: 997
Quote:
I guess that will not work if my spindle thing was 124.37 mm?


Well, you could get the square taper cranks of your choice and try them out on the existing BB (after putting it back in the frame.) Doing that would tell you pretty closely how much too long the existing spindle is. You might want to check that your existing spindle is symmetrical- i.e. the bearing tracks are equidistant from the end faces.

You need a bit of clearance between the chainstay and the back of the cranks/spider- not too much, and not too little.. I'd say 3mm-5mm.

But really that is secondary to the chainline thing- if you measure out from the centre line of the bike, the mid-point between the two chainrings is supposed to be the same as the mid-point of the sprocket cluster so that the chain doesn't have to go too diagonal if you're in big sprocket/big ring or small sprocket/small ring.

So if you've got an 124mm symmetrical spindle and you mount your RH crank of choice on it and it is off outside the chainline by say 5mm, that should mean that you need a spindle 10mm shorter (5mm each side) So in that example 114mm. (as long as it won't cause the cranks to foul on the chainstays)


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PostPosted: Sat Jun 09, 2018 11:25 am 
Old School Grand Master
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Joined: Fri Oct 14, 2011 8:41 pm
Posts: 9314
Location: Cumbria
I'm trying to think if that long BB axle would have a JIS taper meaning an ISO crank might not seat properly?


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PostPosted: Sat Jun 09, 2018 12:00 pm 
Devout Dirtbag
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Joined: Sun Apr 22, 2018 3:59 pm
Posts: 113
Thanks a lot for the info there chaps, I feel so much more understanding and confident in choosing the right chainset now.

Cheers :)


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 Post subject: Re:
PostPosted: Sat Jun 09, 2018 12:57 pm 
Retro Guru
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Joined: Mon Sep 24, 2012 9:10 pm
Posts: 997
Midlife wrote:
I'm trying to think if that long BB axle would have a JIS taper meaning an ISO crank might not seat properly?


Yeah the thought of a JIS/ISO conflict occurred to me too.

I have late '70s SR Royal cranks on a 7400(?) Dura-Ace BB, 110mm iirc, maybe a bit less- in a 68mm shell. Seems to work ok and give me an acceptable chainline for 120mm rear end, and 5mm clearance between chainstay and inner ring. I have no idea whether the tapers are JIS or ISO on either the spindle or the cranks. I wasn't aware of the two standards when I first assembled it. I think it was dumb luck that it all fitted together.


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