How to torque this down?

Discuss light weight issues concerning road bikes & parts.
addictR1
Posts: 1367
Joined: Sun Jun 10, 2012 1:11 am

by addictR1

As it turns out.. it’s actually an M8x35mm coarse thread.

Found a steel version with 12.9 class, but it a 40mm long. So will probably have to cut it down.

No need for washer as original cradle has a washer already.Image

i checked on this site. seems the 12.9 marking is for steel material and Proof Load (MPa) is about 970. but say titanium grade 5, the Proof Load (MPa) is about 74,000 for over 1".

would this mean the Ti bolt would be stronger?

https://www.boltdepot.com/fastener-info ... chart.aspx

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by Weenie


sungod
Posts: 1642
Joined: Fri Dec 24, 2010 9:37 pm
Location: it's raining, it must be uk

by sungod

my eyes have gone wonky! for some reason i read your ruler as 1mm markings but of course it's 2mm, yeah, m8

you need to be wary of the context of the various numbers

below is from https://raceboltuk.com/technical-information/
This helps our Ti Bolts achieve a strength range between Class 8.8 and Class 10.9 alloy steel equivalent bolts, with a Tensile Strength of 950 MPa (138,000 psi
personally i would not use a ti bolt to replace 12.9 steel, aside from strength, ti may be more susceptible to fatigue long term

but if you avoid ti bolts of uncertain quality there's probably enough safety margin in the design - if you aren't heavy and don't ride rough roads then the forces you generate are likely to be lower than a heavy person/rough roads

mattr
Posts: 3694
Joined: Fri May 25, 2007 6:43 pm
Location: The Grim North.

by mattr

addictR1 wrote:
Thu Apr 05, 2018 8:54 pm
Gonna take the bolt to local hardware store and see if they have something like it.
That was a really good idea. Seeing as i didn't notice the tape measure was in 2mm increments either!

WTF, what sort of half arsed tape uses 2mm increments!!

(Get a cheap vernier for future bike type stuff, and read the instructions!! Should only be 20-25 dollars for one good enough for bike measurements. Mine cost nearer €100, and it's massively overkill! )

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ms6073
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Joined: Fri Jul 23, 2004 8:24 pm
Location: Houston, Texas

by ms6073

mattr wrote:
Fri Apr 06, 2018 8:02 am
WTF, what sort of half arsed tape uses 2mm increments!!
Obviously a tape measure that does not cost very much. :smartass:
Michael - The Anaerobic Threshold is neither...

mattr
Posts: 3694
Joined: Fri May 25, 2007 6:43 pm
Location: The Grim North.

by mattr

Well, i've had customers turn up with mail ordered 25mm seatpins that won't tighten up in their 27.2 frame.

"But i measured it"
"what with"
"a tape measure"................

addictR1
Posts: 1367
Joined: Sun Jun 10, 2012 1:11 am

by addictR1

lol.. thanks all. i'll stick with the steel 12.9 :) surprisingly the 40mm i got is 20g and the original measured around 35mm is 17g. the 40mm is too long as i tried to hand tighten it down and it bottoms out while seat craddle was loose. local hardware store didn't have 35mm version and only 30mm available. but i think the 30mm may be too short, so i'll just dremel cut it down to match the original bolt length.

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