Back with the Pedals..again...XT M785 Shimano

dudleygb
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Back with the Pedals..again...XT M785 Shimano

Postby dudleygb » Thu Jan 23, 2014 6:10 pm

Sorry for all the noob questions guys. I just got a pair of M785 pedals for a steal. I checked the installation paper and it seems pretty easy, but how the heck do you measure a torque on an alan key?

Apparently I need to install like this --> http://si.shimano.com/php/download.php? ... 02-ENG.pdf
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mitzikatzi
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Re: Back with the Pedals..again...XT M785 Shimano

Postby mitzikatzi » Thu Jan 23, 2014 6:54 pm

Just use a standard size Allan Key and do them up firm. Go for a ride and recheck them. This question comes up often you just have to learn to do bolts up by feel. Finger tight then 1/4 to 1/2 a turn with the hex key. Remember to use grease on the threads. Also remove and re-grease the pedals every 6 months or so.

You use a hex key in a socket with a torque wrench.

dudleygb
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Re: Back with the Pedals..again...XT M785 Shimano

Postby dudleygb » Thu Jan 23, 2014 6:57 pm

Cool thanx, I need to learn this stuff. Last time I stripped my crank pedal hole, let's try this time. Says on some install videos you need to grease the thread, that necessary? I got a car torque wrench. Or is that to big. I will check if it's got the rating on I guess.

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mick243
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Re: Back with the Pedals..again...XT M785 Shimano

Postby mick243 » Thu Jan 23, 2014 7:10 pm

Yes, you need to grease the threads. The grease does 2 things, it makes it screw in tighter for the same torque, so they don't come undone on their own, and it makes it possible to undo them again without destroying something ( be that the tool, the pedal or the crank...)

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Re: Back with the Pedals..again...XT M785 Shimano

Postby mick243 » Thu Jan 23, 2014 7:11 pm

And if it's got spanner flats, you use a crows foot adaptor on your torque wrench, otherwise a hex driver in a torque wrench as mitzikatzi said

dudleygb
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Re: Back with the Pedals..again...XT M785 Shimano

Postby dudleygb » Thu Jan 23, 2014 7:37 pm

Is this a special torque wrench or will my car one be fine

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mitzikatzi
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Re: Back with the Pedals..again...XT M785 Shimano

Postby mitzikatzi » Thu Jan 23, 2014 7:48 pm

You need a torque wrench with the torque range that you need.

35 to 55 Nm

that seems like a lot. I doubt any of my pedals are that tight.

mick243
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Re: Back with the Pedals..again...XT M785 Shimano

Postby mick243 » Thu Jan 23, 2014 8:18 pm

Depends on what exactly a "car one" is... It needs to be the right torque range, and right drive size for the hex driver or crows foot

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bychosis
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Re: Back with the Pedals..again...XT M785 Shimano

Postby bychosis » Thu Jan 23, 2014 9:23 pm

A car torque wrench would probably be fine. My bike torque wrench wouldn't go anywhere near that torque, I think it stops at around 20Nm.

Do them up nice and firm, not bastard tight. Pedals are threaded differently on each side so that they both tighten rather than loosen under normal pedal rotation, so they shouldn't come undone as well.
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Duck!
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Re: Back with the Pedals..again...XT M785 Shimano

Postby Duck! » Thu Jan 23, 2014 9:43 pm

bychosis wrote:Pedals are threaded differently on each side so that they both tighten rather than loosen under normal pedal rotation....

That is not correct. Try this for yourself; insert a pedal loosely, and turn the cranks while holding the pedal by the spindle, so it doesn't spin freely on its bearings. You will find that the pedal will unwind from the crank. So do them up quite firmly.
I had a thought, but it got run over as it crossed my mind.

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bychosis
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Re: Back with the Pedals..again...XT M785 Shimano

Postby bychosis » Thu Jan 23, 2014 10:12 pm

Duck! wrote:
bychosis wrote:Pedals are threaded differently on each side so that they both tighten rather than loosen under normal pedal rotation....

That is not correct. Try this for yourself; insert a pedal loosely, and turn the cranks while holding the pedal by the spindle, so it doesn't spin freely on its bearings. You will find that the pedal will unwind from the crank. So do them up quite firmly.


Yes, but when you take into account the action of the bearings on the spindle (or some other sciencey action) it actually acts to tighten them as you spin otherwise all of our pedals would eventually fall off and not get stuck so tight we can't undo them. Sheldon Brown taught me that here and here

But still do them up nice and firm so the vertical loading doesn't damage the threads
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Re: Back with the Pedals..again...XT M785 Shimano

Postby ironhanglider » Fri Jan 24, 2014 11:37 pm

[quote = Sheldon also wrote] Note! The precession effect doesn't substitute for screwing your pedals in good and tight. It is very important to do so. The threads (like almost all threads on a bicycle) should be lubricated with grease, or at least with oil.
[/quote]

Precession is only a weak force and certainly won't make your pedals get tighter. Stiff bearings or loose shoelaces wrapping round the spindle can easily overpower precession. Pedals that are hard to remove are usually affected by corrosion or galling, hence the grease.

Cheers,

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