SAFETY WARNING! - alloy brake nuts (Diacompe + ?)
07-06-23, 09:21 AM
#1
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SAFETY WARNING! - alloy brake nuts (Diacompe + ?)
STOP riding any bike with aluminium nuts.
I just pulled apart a pair of Diacompe G.
One nut was in four pieces.
Five others were cracked - brakepad nut, cable-pinch nut, centre-bolt locknut.
They've all been replaced with steel - see second pic.
Now all I need is those bloddy adjusters...
I just pulled apart a pair of Diacompe G.
One nut was in four pieces.
Five others were cracked - brakepad nut, cable-pinch nut, centre-bolt locknut.
They've all been replaced with steel - see second pic.
Now all I need is those bloddy adjusters...
07-06-23, 09:39 AM
#2
feros ferio
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... and the weight savings was how much? 
Thank you for posting.
Thank you for posting.
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Capo: 1959 Modell Campagnolo, S/N 40324; 1960 Sieger (2), S/N 42624, 42597
Carlton: 1962 Franco Suisse, S/N K7911
Peugeot: 1970 UO-8, S/N 0010468
Bianchi: 1982 Campione d'Italia, S/N 1.M9914
Schwinn: 1988 Project KOM-10, S/N F804069
"Far and away the best prize that life offers is the chance to work hard at work worth doing." --Theodore Roosevelt
Capo: 1959 Modell Campagnolo, S/N 40324; 1960 Sieger (2), S/N 42624, 42597
Carlton: 1962 Franco Suisse, S/N K7911
Peugeot: 1970 UO-8, S/N 0010468
Bianchi: 1982 Campione d'Italia, S/N 1.M9914
Schwinn: 1988 Project KOM-10, S/N F804069
07-06-23, 09:49 AM
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I will confirm that I've experienced this as well. I think it's intergranular corrosion or some suchlike. Maybe galvanic corrosion by them being screwed onto steel studs/bolts? Seems almost like the nuts are made of cast alloy, based on the look of the broken faces, but not sure.
The domed "acorn nuts" seem to be built different and I have not seen them crack. I have a couple of those I stole from my Diacompes and put on some Mafac brakes and they have been serving fine. Weight savings is minuscule, agreed.
The domed "acorn nuts" seem to be built different and I have not seen them crack. I have a couple of those I stole from my Diacompes and put on some Mafac brakes and they have been serving fine. Weight savings is minuscule, agreed.
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Owner & co-founder, Cycles René Hubris. Unfortunately attaching questionable braze-ons to perfectly good frames since about 2015. With style.
Owner & co-founder, Cycles René Hubris. Unfortunately attaching questionable braze-ons to perfectly good frames since about 2015. With style.
07-06-23, 10:02 AM
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EDIT: two of them are.
Last edited by oneclick; 07-06-23 at 01:40 PM.
07-06-23, 10:19 AM
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Well geez, there goes that. My domed ones have all been fine, FWIW. Maybe different brand or something. Who knows? They are shinier and less grainy lookin. The Herse ones from the '50s I have are also fine, for whatever reason. I've been wanting to buy some hex bar and make a few reproductions on the lathe.
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Owner & co-founder, Cycles René Hubris. Unfortunately attaching questionable braze-ons to perfectly good frames since about 2015. With style.
07-06-23, 10:31 AM
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07-06-23, 10:39 AM
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And the bigger issue being a brake that is labelled: 'Dia-Compe'. I used to have a dozen sets of these - into recycling. Weak flexy arms, poor mechanical advantage, difficult (!) to keep centered, overly strong return springs, and cheap hardware. Any cheap current dual-pivot brake from Aliexpress or whatever is superior.
More about alu nuts: Campagnolo Record dual-pivot brakes used to feature an alu nut drilled for a grub screw. Almost every one of these that I've seen featured a crack through the nut, including several for sale online, or second-hand. The alu nut itself may not have been a fatal idea, but then drilling a big hole into the side of it and then loading it up with a grub screw... What was Valentino thinking?
More about alu nuts: Campagnolo Record dual-pivot brakes used to feature an alu nut drilled for a grub screw. Almost every one of these that I've seen featured a crack through the nut, including several for sale online, or second-hand. The alu nut itself may not have been a fatal idea, but then drilling a big hole into the side of it and then loading it up with a grub screw... What was Valentino thinking?
07-06-23, 12:48 PM
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And the bigger issue being a brake that is labelled: 'Dia-Compe'. I used to have a dozen sets of these - into recycling. Weak flexy arms, poor mechanical advantage, difficult (!) to keep centered, overly strong return springs, and cheap hardware. Any cheap current dual-pivot brake from Aliexpress or whatever is superior.
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Owner & co-founder, Cycles René Hubris. Unfortunately attaching questionable braze-ons to perfectly good frames since about 2015. With style.
Owner & co-founder, Cycles René Hubris. Unfortunately attaching questionable braze-ons to perfectly good frames since about 2015. With style.
07-06-23, 03:07 PM
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think about this on your next fast downhill - all the braking loads go thru that brake shaft and the nuts that hold the brake arms on.
If those arms start flexing as they do, you might be able to crack the nut. Another possibility is incorrect adjustment.
Like "drillium", hardly worth the safety risk for a few grams of weight savings.
/markp
If those arms start flexing as they do, you might be able to crack the nut. Another possibility is incorrect adjustment.
Like "drillium", hardly worth the safety risk for a few grams of weight savings.
/markp
07-06-23, 05:36 PM
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Aluminium alloys 7075 and 2024 and stress corrosion cracking
The failure shown in the original post seems to be from stress corrosion cracking, most likey caused by salt water. These parts look like aftermarket parts to me. This link points to an article about the problem of stress-corrosion cracking with hard aluminium alloys:
Stress Corrosion Cracking of Aluminum Alloys
Lightweight bicycle hardware made from 6-4 titanium will not have this problem, although they will cost quite a bit more.
Alumium spoke nipples are typically made from 7075 alloy. Anodizing parts made with this material reduces the chance of stress corrosion cracking, but it's best to avoid using them in salty conditions.
Jim Merz
Stress Corrosion Cracking of Aluminum Alloys
Lightweight bicycle hardware made from 6-4 titanium will not have this problem, although they will cost quite a bit more.
Alumium spoke nipples are typically made from 7075 alloy. Anodizing parts made with this material reduces the chance of stress corrosion cracking, but it's best to avoid using them in salty conditions.
Jim Merz
Last edited by Portlandjim; 07-07-23 at 11:10 AM. Reason: spelling error
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07-06-23, 05:46 PM
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