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torque wrench


twotommos's picture

By twotommos - Posted on 17 March 2012

I'm using a few carbon fibre bits on my bike now, and I'm consciously aware of over tightening certain bolts!
What should I be looking out for when it comes to torque wrench's for MTB? Can anyone recommend a specific brand, size and all the bolt sizes so I can smarten up in this area?

Fatboy's picture

I use a 'Pro' which comes with around 8 different sockets and has a range from 3-15Nm of torque. They are a good unit and will do most bolts on your bike except the larger items like the bottom bracket & cassette. It's the smaller bolts that are most sensitive to getting the torque right so I find this unit ideal. I think they retail for about $140 locally.

I use titanium bolts on my bike & tighten them a little below what the recommended settings are but use titanium paste eg. If they recommend 5Nm I go 3.

hathill's picture

I do not agree with the previous post recommending under tensioning bolts. The quote from www.lifetime-reliability.com about bolt tension explains why.

"Bolts are normally tightened by applying torque to the head or nut, which causes bolt to stretch. The stretching results in bolt tension, known as preload, which is the force that holds a joint together. Torque meter can be used to measure bolt tension.

High preload tension helps to keep bolts tight, increases the strength of a joint, and generates friction between parts to resist shear and improves the fatigue resistance of bolted connections

."

Of course, I defer to the experts on carbon but it is definitely a no-no to under tension bolts. Imagine doing that to connecting rod bolts in a car engine. Bike bolts undergo all sorts of cyclic stress so lets give them a fighting chance eh?

More reading here: http://www.google.com.au/url?sa=t&rct=j&q=metal%...

Zoom's picture

Just do it up until the thread strips then back it off half a turn.

hawkeye's picture

I use the Pro one as well, and it actually provides 0.4-20Nm if you use the scale on the adjuster carefully.

I also agree with the post above - I usually go to the somewhere between the middle and the maximum recommended torque. Example, if it says 7-9Nm for the brake caliper bolts I'll go 8-9Nm So long as you don't exceed the max you're OK.

Undertensioning leaves you prone to things coming loose at the worst possible moment, and can result in early fatigue failure. The only exception I wold grant would be brake and shifter clamp bolts on the bars, where I tighten them up just enough to resist in-use movement, but loose enough so that they'll move in a bingle as opposed to snapping off.

Brian's picture

@zoom, you sound like you're a mechanic Eye-wink

chrischris's picture

I purchased a Park Tool TW-1 which I've found really good. However, the value of the 'Pro' along with the attachments it comes with looks like good value. It also has a wider range.

I've only had to use my larger Kinchrome torque wrench once when double checking the installation of the BB & XTR cranks.

Fatboy's picture

You learn something every day - my 10 years of enduro racing on under tensioned bolts without a single mechanical problem of any kind appears to have been a fluke Smiling

If in doubt try this. Apply your carbon paste or titanium paste depending on your bolt & bike materials, torque the bolts to 2Nm below optimum, go for a ride, come back & re check torque. In my experience they will now be at least a couple of Nm higher.

hathill's picture

Yes fatboy - they will appear tighter but that's due to the imperfect mention of measuring bolt torque.
When you are using a torque wrench to tension a bolt (notice the two different terms torque and tension) you are trying to stretch the bolt a pre-determined amount calculated by the amount of torque applied. This is a bit of a guessing game as the lubrication on the threads, bolt head etc can make a huge difference in the resultant bolt tension for a given amount of torque. When you come back an re-check a bolt torque, you have to overcome this intial friction which needs a larger amount of torque to overcome. You are now over torquing the fastener assuming it was correct to begin with and the joint has not moved in the meantime. For accurate bolt tension measurement you have to use something like this:-

http://www.checkline.com/product.php?id=125935&l...

This is good reading too.

http://www.boltscience.com/pages/tighten.htm

mothy's picture

I have one of these "Pro" torque wrenches and find it great. As mentioned above the supplied adapter and both hex/torx 'bits' sold me. It's a "clicker" type wrench; when it gets to the preset torque, a ball-head just below the ratchet kinda 'clicks' as the ratchet 'rolls over' on the ball-head (I didn't understand how they worked, nor the first sales person I spoke to. A mechanic walked past and taught us both!). I just double checked and the hex/torx bits seem to be a fairly standard size. The extension adapter fitted my Stanley hex/torx bits so other sizes that aren't supplied (hex=3/4/5/6mm & T25/T30), shouldn't be a big problem. Also as metioned above, it's only good for 3-15Nm. If you need 15+Nm then this probably isn't the right tool for the job.

Hope that helps a bit.

(Oh, and I found mine in a nameless LBS right near Brookie Oval - Disclaimer: No, not an employee or affiliate - just a customer.)
Cheers
M

VTSS350's picture

I agree with you to a point hathill. Your on the money with steal and aluminium bolts and components.

BUT when you are clamping carbon parts with a steal bolt the bolt will not come close to reaching the point at which it stretches.

twotommos's picture

Thanks Guys this is extremely useful information....what are the most common bolt sizes that one would use on your MTB?
Would the following adaptor sizes cover most bases: 1/4" 3/8" 1/2"?

Biker23's picture

Check out Torpedo7 - Good deal until tomorrow

Zoom's picture

Most bolts on your MTB would be metric. In fact they'd all probably be metric.

Oldernslower's picture

Use a Birzman 1/4" drive set that comes with the 'standard' bits - it is a 3-15Nm and bit sockets of 3, 4, 5, 6, 8mm and T25. Made for bicycles Smiling

Discodan's picture

http://www.cellbikes.com.au/Birzman-Bicycle-Torq...

I've got a 1/4 torque wrench, a chinese cheapy, but need to find a decent set of 1/4 drive hex bits to suit bikes. They seem to be as rare as

chrischris's picture

You could always get a 3/8 adapter. I purchased a Kinchrome set years ago for general car / garage use. Expensive, but it'll last forever.

http://www.justtools.com.au/prod5514.htm

(You can find it a lot cheaper than this... I also don't think this kit contains the adapter you need!)

Nerf Herder's picture

Have just bought one of these as I'm building more bikes these days. Eagerly awaiting for its arrival, but will let you know how easy or hard it is to use, when I've used it a a few times.

http://www.cycotic.com.au/products/Syntace-Torqu...

chrischris's picture

http://www.kincrome.com.au/web/catalogue/search/...

Good for 2 - 24Nm. I have the next size up which I can vouch for. Bunnings sell em for around $80. I thought this came with a 3/8 adapter, but the website doesn't say so. Great value for money considering the quality. I'm very happy with the quality of the next size up. (mainly used for cars... or BB)

No, I don't work for them, just a happy customer. Sidchrome was too expensive... but quality is a must.

hawkeye's picture

For 1/4" bits, if you're on the Northern Beaches try Hardware & General's Industrial tool division.

If you're a tool freak, take your hanky to wipe up your drool

AdrianG's picture

If you're not wanting to spend a ton, I'm using a very good sub-$100 wrench by Giant. (I've seen it as a 'BBB' also.) Gets a 4.5 star rating from bikeradar; http://www.bikeradar.com/gear/category/tools/wre....

It comes with a certificate of calibration, so someone believes in it's accuracy and quality.

It has both Hex 3, 4, 5, 6, 8 and 10mm driver bits, and a T25 torx bit (rotor bolts). The wrench is calibrated in Newton Metres and is marked at each 2NMs, from 2 to 24.

A quick google shows it at http://www.moruyabicycles.com.au/contents/en-uk/...

Discodan's picture

Looks like the same one here for $60 inc freight

http://www.ebay.com.au/itm/Bicycle-Bike-Torque-W...

incidentaly I bought a frame off these guys a few years ago and rate their customer service

twotommos's picture

Hey DiscoDan I think you've nailed this one...looks good!
Thanks everyone on your contributions, flipping fantastico!!

trim's picture

@Discodan, I bought the following set from Bunnings about 2 years ago. Lot's of fittings, allen, torx, sockets, philips etc...all 1/4" drive. I'm pretty sure it was about $85.

http://extranet.snaeurope.com/prodblock.aspx?CAT...

jimmy sprocket's picture

I was alone broken down in the outback 70 km north of Laverton and I needed a torque wrench, badly, to get me out of the jam i was in. I hadn’t eaten for 6 days, my water was rationed and i was sun burnt and delirious. I was seeing MR Bear Grylls out of the corner of my eye.

I began to think like Bear, feel like a Bear and armed only with a stick and some water began to fashion a Bear Grylls torque wrench. I called out to Bear and carved the following into the sand:

"torque = force times the radius"

I could measure a radius for god sake! I wasnt going to die from a lack of a radius. I measured a metre length out on a stick (a decent stick). Bear and I began to feel better.

Now I needed force. Bear and I held the stick togethere and carved the following into the sand:
"force = mass times acceleration"

WHATS that BEAR? WE all have acceleration? here, there, all around, yes gravity! (9.8 m/sec2.

"Well, said Bear "allow me my dear Jimmy Sprocket to present to you some mass, not just any mass, waterery mass, made of water, and with a density of one."

"I Think you get it now. Dont you Jimmy". And with that Bear was gone.

YES i DID. At one end of a metre stick I hung a 1/2 litre bottle of water , at the other end i attached a bike spanner (with spinifex and sap) and let gravity push the lever down until it would not spin the nut anymore (5 nm = ~1/2 litre leverage at 1 metre).

so if youre stuck on a bike somwhere like I was, a Bear may find you.

twotommos's picture

Jimmy dude...any man who knows his science, can listen to the voice of the wind, use his brain and I'm assuming has legs to go....must be very high up on the top 10 list of wannabee riding partners!
I'm sure there's someone who can bear your story out....teee heee heee heee..

philberesford's picture

Just got a very timely email. Superstar Componants have just released their own torque wrench. I'd buy this one.
http://superstar.tibolts.co.uk/product_info.php?...

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