Go Back  Bike Forums > Bike Forums > Classic & Vintage
Reload this Page >

3TTT Death Stem

Classic & Vintage This forum is to discuss the many aspects of classic and vintage bicycles, including musclebikes, lightweights, middleweights, hi-wheelers, bone-shakers, safety bikes and much more.

3TTT Death Stem

Old 11-25-17, 08:08 PM
Senior Member
Thread Starter
Join Date: Aug 2017
Location: Kansas
Posts: 151

Bikes: Peugeot PR-10, Peugeot UO-8, Boeris racing bike, AMF Roadmaster Renegade, Gitane Gypsy Sport, various Schwinn muscle bikes, Schwinn Super Sport, Panasonic DX-4000, Palo Alto Campy equipped bike

Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 42 Post(s)
Likes: 0
Liked 1 Time in 1 Post
3TTT Death Stem

I know AVA stems have the reputation of being the famous "death stem" but check out the end of this 3TTT aero stem:
If this isn't an accident waiting to happen I don't know what is! Some shyster eBay seller was actually passing this off as a good stem. Are failures like this a problem with 3TTT stems also? They seem to share the same double slit expansion area with sharp corners at the top of the slits as AVA death stems do.
taguy4 is offline  
Old 11-25-17, 08:15 PM
Senior Member
malcala622's Avatar
Join Date: Oct 2014
Location: Pico Rivera, CA
Posts: 3,701

Bikes: 88' Bianchi Giro. 88' Bianchi Krono. 80' Gios Torino. 83' Basso Gap. 03 Lemond

Mentioned: 82 Post(s)
Tagged: 0 Thread(s)
Quoted: 1061 Post(s)
Liked 768 Times in 488 Posts
Id like to think half the time its the owner/mechanic or whoever is installing the stem overtightening causing it to crack.

Now i gotta go check all my stems.
'88 Bianchi Giro. '88 Bianchi Krono. '80 Gios Torino. '83 Basso Gap. '03 Lemond Tete

malcala622 is offline  
Old 11-25-17, 08:33 PM
Reynolds's Avatar
Join Date: Jul 2005
Posts: 7,233

Bikes: 1998 Pinarello Asolo, 1992 KHS Montaña pro, 1980 Raleigh DL-1, IGH Hybrid, IGH Utility

Mentioned: 5 Post(s)
Tagged: 0 Thread(s)
Quoted: 727 Post(s)
Liked 397 Times in 224 Posts
It's ugly but I doubt it might cause an accident. Probably the stem would just feel loose and you would check it up.
What i fear most is the handlebar clamp or handlebar breaking suddenly.
Reynolds is offline  
Old 11-25-17, 08:41 PM
Senior Member
Join Date: Aug 2013
Location: San Francisco
Posts: 1,272

Bikes: '68 Raleigh Suberbe, '92 (German) Centurion Equipe, '85 Schwinn Peloton, 1983ish Zunow Road Racer project, '69 Squanch Super Tourer, 1980 Bianchi Super Corsa, '82 Austro-Daimler Vent Noir, '89 Miyata 914 project, 1982ish Bianchi Rallye

Mentioned: 25 Post(s)
Tagged: 0 Thread(s)
Quoted: 293 Post(s)
Liked 7 Times in 7 Posts
That's not safe to ride. All those stems without a stress-relieving hole at the end of the expansion slot risk those cracks.
artclone is offline  
Old 11-25-17, 08:50 PM
Ride, Wrench, Swap, Race
dddd's Avatar
Join Date: Jan 2010
Location: Northern California
Posts: 8,031

Bikes: Cheltenham-Pederson racer, Boulder F/S Paris-Roubaix, Varsity racer, '52 Christophe, '62 Continental, '92 Merckx, '75 Limongi, '76 Presto, '72 Gitane SC, '71 Schwinn SS, etc.

Mentioned: 112 Post(s)
Tagged: 0 Thread(s)
Quoted: 1078 Post(s)
Liked 511 Times in 365 Posts
What I think is the main cause of such failures is any extreme torque that is transmitted from stem to steerer, as when a bike is crashed or when someone tries to forcibly twist out a stuck stem.

The sort of shear forces generated in the quill by such causes will greatly stress the quill at the top of the slot, and the crack can be seen to follow just such a path of maximum shear stress.

Having seen how the walls of a house fail from shear stress during an earthquake, and having studied statics and mechanics of materials, leads me to such a conclusion. The concentration of stress at the top of the slot could have been reduced by even a small radius if the stem's maker had figured on whatever caused this stem to fail, but the history of this item is unknown and it very well may have been seriously abused.
dddd is offline  
Old 11-25-17, 09:16 PM
Senior Member
Join Date: Jun 2006
Posts: 15,921
Mentioned: 105 Post(s)
Tagged: 0 Thread(s)
Quoted: 1910 Post(s)
Liked 741 Times in 578 Posts
The gouging was of not help, time to dress the inside of the steerer.
Beyond that, I have on a few of my stems drilled with a drill press or vertical mill a hole of about 3mm (1/8") to obliterate the sharp slot end. Just makes sense. Not that hard to do.
repechage is offline  
Old 11-25-17, 09:53 PM
Friendship is Magic
3alarmer's Avatar
Join Date: Nov 2010
Location: The Big Tomato
Posts: 19,736

Bikes: old ones

Mentioned: 280 Post(s)
Tagged: 0 Thread(s)
Quoted: 21318 Post(s)
Liked 4,224 Times in 3,089 Posts
...alloy stems are not forever. The AVA ones had a bad period where they were very poor and thinned castings.
But I think I've seen at least one busted stem from all the more common manufacturers...especially if you include failures at the bar clamp area.
3alarmer is online now  
Old 11-25-17, 10:12 PM
Senior Member
Thread Starter
Join Date: Aug 2017
Location: Kansas
Posts: 151

Bikes: Peugeot PR-10, Peugeot UO-8, Boeris racing bike, AMF Roadmaster Renegade, Gitane Gypsy Sport, various Schwinn muscle bikes, Schwinn Super Sport, Panasonic DX-4000, Palo Alto Campy equipped bike

Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 42 Post(s)
Likes: 0
Liked 1 Time in 1 Post
Speaking of bad designs, I have an AVA stem on one of my Peugeots that has an oval cutout in the front of it's handlebar clamp to let the handlebar show thru; I've always thought that was a bad design, too, but it's managed to hold up since 1976. I would like to change it, though, for a more substantial looking stem at some point.

Getting back to the 3TTT stem above, I wouldn't want to be going very fast and turning a corner when that piece breaks off and the stem comes loose in the steerer tube. Something tells me that wouldn't be a good situation to be in. If it broke while going slow and without any traffic around it might not be a catastrophe.
taguy4 is offline  
Old 11-25-17, 11:29 PM
Senior Member
Join Date: Oct 2015
Location: Los Angeles
Posts: 6,287

Bikes: 78 Masi Criterium, 68 PX10, 2016 Mercian King of Mercia, Rivendell Clem Smith Jr

Mentioned: 120 Post(s)
Tagged: 0 Thread(s)
Quoted: 2311 Post(s)
Liked 563 Times in 404 Posts
That stem is toast. Don't ride it if you don't want to die.
Salamandrine is offline  
Old 11-25-17, 11:56 PM
A Roadie Forever
79pmooney's Avatar
Join Date: Oct 2014
Location: Portland, OR
Posts: 9,600

Bikes: (2) ti TiCycles, 2007 w/ triple and 2011 fixed, 1979 Peter Mooney, ~1983 Trek 420 now fixed and ~1973 Raleigh Carlton Competition gravel grinder

Mentioned: 102 Post(s)
Tagged: 0 Thread(s)
Quoted: 2930 Post(s)
Likes: 0
Liked 1,492 Times in 994 Posts
My take? Retire that stem but don't sweat it. It was highly unlikely to get worse as long as it was sitting in the steerer undisturbed. Putting it back in and re-using it is iffy so I wouldn't. And I would chalk it up as a "good" failure. Any failure you detect at your workbench, vs on the road, is, in my book, a good failure.

Edit: I've never thought to study the slots on the TTT stems I've owned. Likely many had that same square detail. Never broke one and I used some of them many miles. My Peter Mooney went 25,000 plus miles on a new TTT bar and stem. I retired them because they had seen a couple of hard crashes. (I was worried more about the handlebars.) That said, I will have to look at all my stems and their slots. (My Nittos use wedges which has always struck me as a better system in addition to being easier to make. Among other things, diameter and fit tolerances matter far less with a wedge.)


Last edited by 79pmooney; 11-26-17 at 12:05 AM.
79pmooney is offline  
Related Topics
Thread Starter
Last Post
Classic & Vintage
04-30-17 08:19 PM
Classic & Vintage
06-13-16 02:03 PM
General Cycling Discussion
07-22-14 02:29 AM
Road Cycling
01-05-11 11:33 PM
Classic & Vintage
12-27-09 01:19 AM

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell My Personal Information -

Copyright © 2021 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.