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Cracked GB stem

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Cracked GB stem

Old 02-04-21, 11:41 AM
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Cracked GB stem

Typical issue:





So make a flat spot, centre-punch, drill, chamfer, and polish (bit of compound on a shoelace):



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Old 02-04-21, 02:19 PM
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Nice work. Thanks for posting excellent pictures. This could help someone in the future with the same dilemma. I have heard that ttt (3T) stems often do this as well.
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Old 02-04-21, 02:54 PM
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Originally Posted by Velo Mule View Post
Nice work. Thanks for posting excellent pictures. This could help someone in the future with the same dilemma. I have heard that ttt (3T) stems often do this as well.
It's not the maker, it's the slot. Of course it's going to crack.
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Old 02-04-21, 03:18 PM
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I don't think I've heard of GB stems using this sort of unrelieved slot... I guess I'd better check my Raleigh.

I have had this on an AVA stem that I owned and sold. Being a hollow cast stem, it was already scary enough. pics below.....





Steve in snowy Peoria
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Old 02-04-21, 04:16 PM
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Originally Posted by steelbikeguy View Post
I don't think I've heard of GB stems using this sort of unrelieved slot... I guess I'd better check my Raleigh.
Yes you should - this is from a GB stem out of an '83 International - slots yes; cracks fortunately no (but it still will get holes because otherwise no really means not yet):





And while you have it apart, consider this - a poor excuse for a key, hardly more than a filing upset from the top of the cone.
On the other stem it had clearly twice not been in a slot when tightened - gouges on the stem inner face and the "key" pushed half-way back to where it had started.
It's getting a quick once-over with a smooth file, so there'll be no more gouges:

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Old 02-04-21, 05:15 PM
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Originally Posted by Velo Mule View Post
Nice work. Thanks for posting excellent pictures. This could help someone in the future with the same dilemma. I have heard that ttt (3T) stems often do this as well.
3t stems, even the vintage ones from 60s, are forged and not cast like French stems from bike boom era....and all those I have messed around with had the relief hole drilled from factory. As such, if I plan to ride the vintage bike and want to keep vintage-correct I replace the French stem (bars generally too) and replace with 3t. Its not just the lack of the stress relief hole but French castings of this era are notoriously bad. Here is 3t page from 1966 Cyclo-Pedia:
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Old 02-04-21, 05:43 PM
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Originally Posted by Markeologist View Post
3t stems, even the vintage ones from 60s, are forged and not cast like French stems from bike boom era....and all those I have messed around with had the relief hole drilled from factory. As such, if I plan to ride the vintage bike and want to keep vintage-correct I replace the French stem (bars generally too) and replace with 3t.
Why did they choose a 7mm hex-socket?

Oh, sorry, so they could sell you one because that size never showed up in the metric sets you could (can still?) buy.
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Old 02-04-21, 09:10 PM
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Originally Posted by oneclick View Post
Why did they choose a 7mm hex-socket?

Oh, sorry, so they could sell you one because that size never showed up in the metric sets you could (can still?) buy.
that sort of question would probably make a great thread all by itself... "why don't manufacturers stick with the standards?".
I know that I've wondered why one of my British bikes uses a 7/32" allen for the seatpost binder bolt. I think it might use Whitworth threads too.

Steve in Peoria
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Old 02-05-21, 03:24 AM
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Originally Posted by steelbikeguy View Post
that sort of question would probably make a great thread all by itself... "why don't manufacturers stick with the standards?".
Raleigh did.

Originally Posted by steelbikeguy View Post
I know that I've wondered why one of my British bikes uses a 7/32" allen for the seatpost binder bolt. I think it might use Whitworth threads too.

Steve in Peoria
More than one of the metric sets in the tool bin have a 5.5mm size.
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Old 02-05-21, 05:43 AM
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Originally Posted by steelbikeguy View Post
that sort of question would probably make a great thread all by itself... "why don't manufacturers stick with the standards?".
I know that I've wondered why one of my British bikes uses a 7/32" allen for the seatpost binder bolt. I think it might use Whitworth threads too.
I learned, thru trial and error in a very mixed bucket of sockets, that many of the vintage nuts on Raleigh seat post bolts fit a 17/32 socket quite nicely. Again not metric and a pretty rare size. We've seen many of those nuts rounded off and damaged and seat stay paint all chipped off from "mechanics" using the wrong socket or a poorly made adjustable wrench. Even using a well made adjustable wrench requires skill and luck. I've assumed the actual size is Whitworth but I don't know.
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Old 02-05-21, 07:20 AM
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Doing a once over last night on my ladies' ava stem equipped Schwinn Super Sport, The stem had twisted a very noticeable amount on our last ride apparently. The right grip was down a good inch or more from the left grip. Yikes.
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Old 02-05-21, 04:11 PM
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So as everything was out and setup to fix slotted stems all of them got at least looked at; then this one appeared and it is sort of a comment on the slot-versus-wedge arrangement.

Someone (not the factory,surely) has taken a slotted 3TTT stem and cut it at exactly the correct angle for a wedge, which wedge and screw fit very nicely. It's a good job, the cut is flat and the tip has been tidied up just the right amount:




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