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PostPosted: Thu Sep 24, 2020 12:22 pm 
Retro Guru

Joined: Wed Jun 13, 2007 3:31 pm
Posts: 388
Location: Leeds
What are people views on using aluminium bolts on disc rotors? It's a Sram/Avid set up with 180/160mm rotors.

For context, this is for a kids bike (a 10yr old) not on a full on DH bike.

Your opinions and advice appreciated


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PostPosted: Thu Sep 24, 2020 12:29 pm 
Retro Guru
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Joined: Thu May 17, 2012 11:04 am
Posts: 979
Location: manchester
Use steel or Ti if you are weight worried. never use Alloy bolts for high stress items.


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PostPosted: Thu Sep 24, 2020 5:21 pm 
Retro Guru
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Joined: Tue Aug 07, 2007 12:41 pm
Posts: 483
Location: BURGOS. Castilla y León. ESPAÑA
No, it is no Ok. Use Ti bolts but never aluminium in stressed points.


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PostPosted: Thu Sep 24, 2020 6:02 pm 
Old School Grand Master

Joined: Mon Feb 11, 2008 9:42 am
Posts: 3623
You'd be better off with 3 steel or Ti than 6 aluminium.


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PostPosted: Thu Sep 24, 2020 7:01 pm 
Old School Grand Master

Joined: Tue Oct 09, 2007 1:55 pm
Posts: 10259
Location: New Forest, UK
The force is multiplied 3-4x compared to the brake calliper force - or something like 20x of the force from the tyre.
Do not do it.


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PostPosted: Fri Sep 25, 2020 1:28 am 
Gold Trader / MacRetro rider
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Joined: Sun May 25, 2008 11:03 am
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Location: Sunny Bournemouth
Its down to shear forces as those are the forces acting on the bolt as the rotor pulls against them.
Ti and steel are more than 4x the shear strength of alloy, which is quite soft really when you think about it.


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PostPosted: Tue Oct 06, 2020 11:34 pm 
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Joined: Sun Dec 12, 2010 10:50 pm
Posts: 783
I wanted little red bolts for the discs on me San An so was being tempted by all the anodised alu ones. However, I knew Alu brake disc bolts was a bad idea, but did find some red steel ones.
Which was nice.

Also, when I was 10-ish, I was riding quite hard and fast on road. I was probably only 12 when I start breaking rear spokes (at the bend, non-countersunk cheap hubs) through pedalling effort uphill. Don't underestimate the power of a 10-year old.
Also, much like running out of bog roll or printer ink, brakes and brake parts never ever fail until you really need them.


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