How to torque this down?

Discuss light weight issues concerning road bikes & parts.
addictR1
Posts: 1380
Joined: Sun Jun 10, 2012 1:11 am

by addictR1

This is the seatpost for my BMC TMR02. I’m using Romin Evo Pro saddle with carbon rails. Before it was the Romin Comp with Ti rails so I didn’t worry about tightening it down.

But with carbon rail, not sure how to go about it. The socket won’t fit through the hole in the saddle and not sure if there’s such a thing as side torque wrench?

Thoughts?

Image

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by Weenie


TLN
Posts: 91
Joined: Wed Jul 12, 2017 4:50 pm

by TLN

Does't look like a stock mount. It should be a hex head on the bottom, and nut on the top. Nut might be specific to that seatpost too. I'd contact BMC and figure it out. I bet you can easily source screws there.

g00se
Posts: 34
Joined: Fri Feb 21, 2014 11:22 pm

by g00se

Couldn't you replace the bolt with a hex-bolt and use a hex driver in the torque wrench? But TLN is right, that doesn't look stock...

glander
Posts: 52
Joined: Sat Feb 24, 2018 3:07 pm

by glander

addictR1 wrote:
Tue Apr 03, 2018 7:45 am
This is the seatpost for my BMC TMR02. I’m using Romin Evo Pro saddle with carbon rails. Before it was the Romin Comp with Ti rails so I didn’t worry about tightening it down.

But with carbon rail, not sure how to go about it. The socket won’t fit through the hole in the saddle and not sure if there’s such a thing as side torque wrench?

Thoughts?

Image

Image


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First before you start wrenching make sure that clamp is approved for those carbon rails. The alloy ones are round and the Specialized Carbon rails oval so you might end up crushing them if you use the wrong clamp. Just a thought....

sungod
Posts: 1685
Joined: Fri Dec 24, 2010 9:37 pm
Location: it's raining, it must be uk

by sungod

there're images of the post that show the same bolt head, it's also in the bmc online manual, so it seems correct, for instance...
https://aerogeeks.files.wordpress.com/2 ... _02571.jpg
https://static.evanscycles.com/producti ... 8500-1.jpg

that clamp looks like it makes rail contact over a large area, that should give a wide safety margin, i would just gradually tighten it / test it until it's secure

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oldnslow2
Posts: 222
Joined: Wed Feb 03, 2016 1:50 pm

by oldnslow2

As mentioned, replace the bolt with on that has a Allen or Torx head.

You could also use a crows foot on the torque wrench.
Image

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ms6073
Posts: 2561
Joined: Fri Jul 23, 2004 8:24 pm
Location: Houston, Texas

by ms6073

addictR1 wrote:
Tue Apr 03, 2018 7:45 am
The socket won’t fit through the hole in the saddle and not sure if there’s such a thing as side torque wrench?
I would use a 1/4" drive low profile metric socket with 1/4" extension. Place the socket on the nut, insert the extension, then attached the torque wrench to the extension.
Michael - The Anaerobic Threshold is neither...

KarlC
Posts: 732
Joined: Fri Dec 05, 2014 2:08 am
Location: San Diego Ca USA

by KarlC

Change the bolt to an allen head bolt, thats what I did.

You can get one at any hardware store, or order a light weight one

dfischer1
Posts: 28
Joined: Fri Aug 01, 2014 8:19 pm

by dfischer1

KarlC wrote:
Tue Apr 03, 2018 3:29 pm
Change the bolt to an allen head bolt, thats what I did.

You can get one at any hardware store, or order a light weight one
+1. I'd be very surprised if that was the stock bolt. Looks like a bodge.

addictR1
Posts: 1380
Joined: Sun Jun 10, 2012 1:11 am

by addictR1

thanks all for the response. the bolt is original from BMC and yes i agree it looks like a bodge! the rail fits and support the carbon rails, so should be ok there. i fitted over the carbon rails first and inspected before mounting and fitting it on.

KarlC, which kind of bolt did you get and where to get a light one from? Thanks!

sungod
Posts: 1685
Joined: Fri Dec 24, 2010 9:37 pm
Location: it's raining, it must be uk

by sungod

what is the code on top of the bolt? it looks like it might be 12.9 which is a high-tensile steel, but the image isn't clear

whatever grade it is, presumably bmc's engineers decided that's what is needed, i.e. to take any off-axis forces from the saddle

if you replace the bolt, i'd use one of equivalent strength

addictR1
Posts: 1380
Joined: Sun Jun 10, 2012 1:11 am

by addictR1

Ok I’ve took some pics of the bolt for your references. Didn’t know about the number listed on the bolt till I saw Sungods post.

Not sure what the number represents but hopefully there’s a Ti lightweight version of this bolt I can use instead.

If you guys have a link on where to get it, that will be greatly appreciated Image

ImageImage


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sungod
Posts: 1685
Joined: Fri Dec 24, 2010 9:37 pm
Location: it's raining, it must be uk

by sungod

12.9 is a high strength steel bolt, ti bolts wont be as strong

what the numbers mean...

https://www.westfieldfasteners.co.uk/Re ... _Spec.html

assume that bmc's engineers chose 12.9 grade for a reason and forget about saving a few grams on a part that could cause a serious accident if it failed

from the image it looks like m4, get a 12.9 grade steel hex bolt, might be worth putting a washer under it as the head will be smaller than the standard bolt
https://www.westfieldfasteners.co.uk/Bo ... -12.9.html

best option is leave the current bolt as is and simply tighten until the saddle is secure, with that clamp design you have plenty of margin

mattr
Posts: 3907
Joined: Fri May 25, 2007 6:43 pm
Location: The Grim North.

by mattr

M4? On a single bolt clamp?
M6 is more like it.

https://www.westfieldfasteners.co.uk/BZ ... ap_M6.html

Still, best to measure across the threads etc to check all the dimensions.
But my money is on a M6x40 being the best fit.

by Weenie


addictR1
Posts: 1380
Joined: Sun Jun 10, 2012 1:11 am

by addictR1

Damn you guys are good!!

Thanks Sungod and Matt for the links. Gonna take the bolt to local hardware store and see if they have something like it.


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