Is a torque wrench really necessary ?

[snazpizaz]

Hi

I have a titanium Brompton and i'm wondering about investing in a torque wrench.
However, taking i don't (yet) do huge millage on it i was concerned that a torque wrench can become de-calibrated over time/ when not in use and using it unawares whilst in this state is likely to achieve the exact opposite of it's intended purpose and damage the bike.

What are folks views on use of a torque wrench for servicing a bike used only for light or summer month leisure cycling ? I do basic bike maintenance at home and have a good tool kit otherwise.

My torque requirements are:

• Do by hand ?
• Brake lever 2
• Rear rack stay 3
• Do by hand or with a torque wrench
• Front wheel hook 3.5
• Front carrier block 4
• Do with a torque wrench
• Chain tensioner 5
• Brake cable clamp 8
• (Dynamo wheel axel 8) - don't have one
• Handlebar catch clip 9
• Brake caliper 10
• Chainring bolt 10
• Pentaclip 15-17
• Handlebar clamp 18 max
• 3-6 speed wheel nut 18

Do by hand ?

• Pedals 30
• Crank bolt 30

Required Torque wrench range = 3-20Nm/ with Hex 4-5-6 and pz2

Thanks
sp

 

[Milkfloat]

That depends on how calibrated your hand is, if you are mechanically sympathetic then you may not need one at all. A cheap torque wrench won't be highly accurate to start with, but to be honest does not need to be. Closer enough is good enough for cycling applications.

 

[Mark pallister]

If you service your own bikes I would say a torque wrench is essential
wether or not they decalibrate over time I’ve no idea
not using one you risk snapping bolts ,cracking the frame or cranks ,so why risk it ?

 

[Smudge]

I prefer to use feel rather than trust something to do it for me. Torque wrenches certainly can go out of calibration.
Whether you have faith in yourself to do this, only you can answer that.

 

[carlosfandangus]

I use a torque wrench, 2 of my bikes are carbon so tend to use it a lot, paid about £30 quid from CRC and always slacken off to less than 2nm when I have finished using it, don't know its accuracy compared to more expensive ones, however it is more accurate than these extra large and strong ex bricklayers hands!!

 

[si_c]

I have a torque wrench and do use it, but only because I have it.

Until I got a new bike with a carbon steerer tube I just tightened by hand, you get a feel for what's tight enough after a very short time. If something comes loose then you just do it a bit tighter next time.

I would say a torque wrench is only necessary if you have carbon parts on the bike - they are very sensitive to crushing damage so overtightening does risk permanently damaging them.

My torque wrench was £20 from Screwfix, you don't need an expensive cycle specific one.

Edit to say: it's also a ratchet wrench and has multiple socket heads so it's actually just useful full stop ignoring the torque element of it.

 

[Profpointy]

I've never used one on bikes (all my bikes have been steel not carbon) and the only car thing I've used one on is a cylinder head, though there are other car jobs where I would use one. I'm not a professional mechanic in any sphere but I do think I have reasonable mechanical sympathy. I've happily tightened both car and bike bearings by feel for instance. Apparently it's considered advisable to use a torque wrench for things screwing into carbon fibre frames but I've no personal experience of that

 

[Electric_Andy]

People use torque wrenches for years, as long as you slacken them off after use it should be fine. The inaccuracy from degredation of the wrench may be as much as the inacuracy due to a cheaper tool anyway.

I've never owned a torque wrench but have maintained cycles and motorcycles for years. Never had a problem, just look at the size of the fastener and what job it has to do, and use common sense.

 

[figbat]

I tend to do a dynamic risk assessment (as my workplace would describe it) and decide how critical the correct torque value is and what the consequences of over- or under-torqueing might be. Most times I'll do it by feel but now I have three carbon-fibre frames, one with carbon bars, I have recently picked up a 2-20 Nm torque wrench. I already had a much bigger one for automotive use. I always store them unwound and never revalidate their accuracy but so far, so good.

 

[Cycleops]

I'm guessing those figures are recommended by Brompton. They are just covering themselves against abuse by customers. As long as you are careful and have a degree of 'mechanical sympathy' you can manage without a torque wrench.

 

[Andy in Germany]

If you service your own bikes I would say a torque wrench is essential
wether or not they decalibrate over time I’ve no idea
not using one you risk snapping bolts ,cracking the frame or cranks ,so why risk it ?

Elder son reports that in a shop torque wrenches "should" be recalibrated every year at least.

His employer never has, on the other hand...

 

[numbnuts]

That depends on how calibrated your hand is, if you are mechanically sympathetic then you may not need one at all. A cheap torque wrench won't be highly accurate to start with, but to be honest does not need to be. Closer enough is good enough for cycling applications.

This ^^^

 

[snazpizaz]

Thanks that's quite a lot in favour of doing it by hand/feel.

Given the torque specifications given by Brompton and the majority in this post favouring hand/feel tightening, i think 9 of the listed bolts could be tightened by hand/feel. That narrows the concerning bolts down to these 6:

• Chainring bolt 10Nm - not sure about this
• Pentaclip 15-17Nm - holds saddle in place - could i do this by hand/feel ? - https://www.evanscycles.com/brompton-pentaclip-00102999
• Handlebar clamp 18Nm max - this seems to me the most volatile nut/bolt on the entire bike and one where the torque needs to be correct because the securing passages/holes on the steel frame are not particularly robust. see images here: https://www.perennialcycle.com/brompton-handlebar-clamp-bolt-all-riser-stems.html
• 3-6 speed wheel nut 1Nm 8 - not sure about this

I'm unclear if people think i could do the following by hand/feel

• Pedals 30Nm - lightweight folders - https://brilliantbikes.co.uk/47-brompton-pedals
• Crank bolt 30Nm

My hand is 'sympathetically calibrated' to the extent that i've ridden steel generic bikes all my life. However i am not attuned or familiar with the measure of Nm, just boy-to-man basic cycle maintenance habits.

Of the TR's mentioned:
1. The £30 CRC torque wrench option mentioned seems to be a pre-set tool version.
https://www.chainreactioncycles.com/s?q=torgue+wrench&cat=direct
2. The £20 screfix non-cycle specific torque wrench option mentioned (seems like a good idea budget wise ?) indicates something along the lines of this Magnusson torque wrench:
https://www.screwfix.com/p/magnusson-torque-wrench-3-8-x-14/5848v
Not sure if cheap torque wrenches are considered advantageous or not though

Maybe i could just do with a preset 18Nm torque wrench here ?

cheers
sp

 

[Rusty Nails]

Metal bikes and components can be very forgiving of cack-handed bodgers mechanics, unlike carbon.

I suspect that many mechanics with "sympathetically calibrated" hands are not quite as accurate as they believe but just get away with it.

 

[snorri]

views on use of a torque wrench for servicing a bike used only for light or summer month leisure cycling ?

I was doing some "summer month leisure cycling" when my handlebars came loose, very loose in fact. A quick investigation revealed a sheared bolt which had apparently been over torqued for some time but decided to shear just as I was pushing my bike across a road 500 miles from home. Had I been pedalling the bike at the time I would have been very lucky not to have suffered injury, so no, torque wrenches are not essential but could save you a bit of serious bother.