To Torque Wrench or not?

Roadrookie

I bought a Giant Defy Composite a few months ago and have been worrying about over-tightening the seat post collar and cracking the frame. Is this a legit worry? Should I get a torque wrench and if so any recommendations on a reasonable budget model? I was out on a ride the other day and the seat post sank as it was under-tightened so I want to avoid that happening again but I definitely dont want to crack the frame.
Thanks

chrisaonabike

I'll be interested in answers to this one too, since I'm in exactly the same position, also with a Giant Defy Comp.

schweiz

http://www.toolbox.co.uk/sealey-stw1012 ... 526-108350

and

http://www.powertoolwarehouse.co.uk/sea ... etric.html

and

http://www.finishlineusa.com/products/fiber_grip.htm

zippy483

Yes it is worth getting one

And this one is well worth the limited expense

http://www.ribblecycles.co.uk/sp/road-t ... Googlebase

Roadrookie

Thanks for the replies, will order one. Sounds like you need one too ChrisAOnABike.
Cheers

defycomp2

I have a Giant Defy Composite and I have a torque wrench and it is surprising how tight 6Nm actually is.

Roadrookie

Thanks, that was my next question. 6Nm it is.
Cheers

rrsodl

DefyComp2 wrote:

I have a Giant Defy Composite and I have a torque wrench and it is surprising how tight 6Nm actually is.

Totally agree with this statement.

I recently bought a torque wrench and I've been going through all stems, seatposts, etc. None were close to the limit. 5NM is more than I have used by hand.

To tight a seatpost, I always used guidelines given to me by a friend that is a bike mechanic. Tight enough that you cannot twist the saddle with one hand. I reckon that would be about 3NM

Stems were always finger tight and that was good enough and within the safety range.

gloomyandy

Remember that if there is only a single torque value given this is the maximum. Very often a much lower value is more than sufficient, particularly if you use carbon paste.

sungod

^^^this

rather than just tightening, get a tube of carbon assembly paste*, this increases friction between the post and tube, then...

remove seatpost, give it and the inside of the seattube a good wipe to remove any grease/crud

smear the paste over the post for the full length that will go into the seattube

put the post back in, it may take a bit of twisting/shoving to do this with the paste on it

tighten clamp, the post should now stay put with less clamping force

wipe off the excess paste around the top of the tube


*the finshline one is a bit grittier than the tacx one, if the post is already a tight fit i'd try the tacx type

smidsy

You need to buy a decent quality torque wrench to get any benefit - cheap ones are as accurate as not having one.

Park tools one is where I would be going.

chrisaonabike

Roadrookie wrote:

Thanks for the replies, will order one. Sounds like you need one too ChrisAOnABike.
Cheers

Yep, thanks too from me.

rolf_f

smidsy wrote:

You need to buy a decent quality torque wrench to get any benefit - cheap ones are as accurate as not having one.

Not really so - unless by cheap you mean something out of a Christmas cracker. Cheapness isn't necessarily going to be an indicator or otherwise of calibration accuracy and even a fairly poor torque wrench is likely to be vastly better than guessing.

Ultimately, unless you are assembling a bike from scratch, all you really need is consistency. You can use a torque wrench to measure how tightly a component is fitted (whether or not the measured torque corresponds to a specific factory setting) and use that setting as the value to re-torque the component when refitting. At no point in this process do you actually need to know what torque you are actually using. Obviously, if the torque wrench gives readings close to the factory values then you can be more confident that it is well calibrated but who gets their torque wrenches recalibrated regularly anyway?

BBB one works for me.

Roadrookie

Thanks for the guidance all. I take the point about the carbon assembly paste and will order some too as I want to do what I can to avoid overtightening as much as possible but also dont want another dropped saddle halfway round a 20 mile ride. I see Giant do a Torque Wrench too so maybe that would be worth considering as cost is similar to BBB.
Cheers.

TommyB61

Rolf F wrote:

BBB one works for me.

+1 for the BBB version.

drlodge

I've never used a torque wrench, and probably never will. I think I know by feel how tight something needs to be - the risk with a bike is generally overtigthening, and as long as its tight enough to do the job, then job done.

Different with say a car cyclinder head, where the bolts need to be at least a certain tightness, and even.

petemadoc

I have an inbuilt torque wrench

stem bolts = a little bit tight
seatpost bolts = not very tight
everything else = very tight
chainset bolts = very very tight

Always worked ok for me

TheTallCyclist

Get one. You will be surprised how much off you were before. Especially with carbon parts. I used to think a torque wrenches are bogus. Not anymore: http://www.thetallcyclist.com/2012/11/r ... ue-wrench/

Enjoy your new bike!

drlodge

PeteMadoc wrote:

I have an inbuilt torque wrench

stem bolts = a little bit tight
seatpost bolts = not very tight
everything else = very tight
chainset bolts = very very tight

Always worked ok for me

^--- this, kinda. The right amount to torque it is...not too tight, not to loose, just the right amount. Experience and common sense prevails, if you have both

petemadoc

Just turn the bolt until you hear a nice crackling sound....

smidsy

Rolf F wrote:

smidsy wrote:

You need to buy a decent quality torque wrench to get any benefit - cheap ones are as accurate as not having one.

Not really so - unless by cheap you mean something out of a Christmas cracker. Cheapness isn't necessarily going to be an indicator or otherwise of calibration accuracy and even a fairly poor torque wrench is likely to be vastly better than guessing.

Ultimately, unless you are assembling a bike from scratch, all you really need is consistency. You can use a torque wrench to measure how tightly a component is fitted (whether or not the measured torque corresponds to a specific factory setting) and use that setting as the value to re-torque the component when refitting. At no point in this process do you actually need to know what torque you are actually using. Obviously, if the torque wrench gives readings close to the factory values then you can be more confident that it is well calibrated but who gets their torque wrenches recalibrated regularly anyway?

BBB one works for me.

Actually you are correct that I was wrong.

A cheap torque wrench is actually less accurate than not having one, as you blindly tighten things to the numbers and not what you feel is going on.

Anyway each to their own.

lotus49

TheTallCyclist wrote:

Get one. You will be surprised how much off you were before. Especially with carbon parts. I used to think a torque wrenches are bogus. Not anymore: http://www.thetallcyclist.com/2012/11/r ... ue-wrench/

Enjoy your new bike!

I am somewhat sceptical as to whether a torque wrench is really necessary. Being off is not a bad thing in itself. The quoted torques are maximums so as long as nothing is coming loose and the torque you have used is lower than the maximum, why would it matter?

My approach with anything delicate (and I have to admit that I don't have a carbon bike) is to use just enough to tighten it sufficiently (and that will vary according to what it is). If it wasn't enough, tighten it a bit more. I cannot remember the last time I damaged something by overtightening it, but it was a very long time ago and I have worked with things ranging from clocks to cars. I'm a big believer in developing a degree of mechanical sympathy.

theslowone

Ultimately, unless you are assembling a bike from scratch, all you really need is consistency. You can use a torque wrench to measure how tightly a component is fitted (whether or not the measured torque corresponds to a specific factory setting) and use that setting as the value to re-torque the component when refitting. At no point in this process do you actually need to know what torque you are actually using. Obviously, if the torque wrench gives readings close to the factory values then you can be more confident that it is well calibrated but who gets their torque wrenches recalibrated regularly anyway?
quote]

Sorry to disagree. I head a calibration lab and we calibrate torque wrenches and analysers. You need to be aware that a tightening torque differs from a loosening torque. The actual difference varies depending on material of bolt and part, as well as any grease used. Your point is valid that it will however help with consistancy of tightening. I use a torque wrench on my bike, although I know that it is not accuate beacause It failed calibration and was scrapped by work. Still prob better than some cheap tat though

kieranb

well, I've never used one to build up my bikes (4 - track, road, MTB x 2) but then I haven't moved over to carbon!

smidsy

theslowone wrote:

I head a calibration lab and we calibrate torque wrenches and analysers. I use a torque wrench on my bike, although I know that it is not accuate beacause It failed calibration and was scrapped by work.

WTF...I despair :shock:

theslowone

You are prob right It is all a bit sad. I was not so clear in my last post. I am not a cycle mechanic so am unable to comment on the importance of bolt torque on a bike. I am however an engineer so I had the chance to "own" a very expensive torque wrench from work, it had failed calibration but still OK within a known error of 0.3NM.
Believe it or not the calibration of torque equipment is not the saddest or geekiest part of life in a cal lab.

Mental note to self GET OUT MORE :roll:

Frank the tank

Two white knuckles is enough, any more and you'll strip the thread.