[Closed] Improvised torque wrench - fork top cap 28Nm

40Nm for a cassette is bastard hard tight. 28Nm is less of a bastard. I’d go with that.

It's a fork cap, it's not overly sensitive. Needs to be tight enough to make the seal and to not vibrate loose, needs to be not tight enough to damage anything. "A little bit past snug" is probably precise enough tbh.

It's 28nm... I'd just go to the 25 max of your normal torque wrench, give it a bit of a snug up if you feel it needs it.

Use your 12Nm one twice - that will be 24Nm. 😉

28Nm is tighter than it needs to be in terms of being air tight, but anything less than that and it could be a cause of creaking.

And any ugg a duggs in the windy gun is bad. Maybe an ugdug, but not a full blown dugg a dugg.
And yeah, use the 25 you’ve got and a touch up of a gnats dick with a ratchet.

If you regularly use hand tools I would say you are overthinking it. If its torqued 25-35nm ish it will be fine. Obviously they are fine alloy threads so dont go mad, dont leave them loose either as the stanchions can walk the crown.

Lots of options if you want a new tool, ebay 19-110 £18, 3/8 7-112nm magnusson screwfix £25, Draper 10-80 £30, Teng 20-100 £60

I torque customers with a fancy digital one, but have never had any issues with my own personal bikes done at home.

I would probably just suggest spending the £30 on a draper one for home use if you want one.

I go off how much effort was required to undo it, then use about the same effort to do it back up.

28Nm sounds pretty high for a stem top cap, it's only for pre-loading the headset before you do up the stem bolts...

You sure it's not meant to be 2.8Nm?

Fork top cap, not a stem top cap.

@cookeaa I thought the same. 28Nm would probably prevent the bars from turning.... on my bikes at least.

EDIT: Ah yes. I see now.

Fork top cap, not a stem top cap.

Whoops.

As you were...

If it's spec'd for 28Nm, then I'd be pretty happy with it at either the 25Nm or the 30Nm wrenches that you've got available to you.

I’d just nip it up by feel - it’s just a fork top cap, it doesn’t rely on tightness for sealing because surely it’ll have an O ring to do that?

Good points, thanks.

I have a rough idea now from experimentation with both my 30-210 and improvised, it's more than what I'd have guessed. I wouldn't trust my basic (or any) 30-210 right at the bottom of its range for actually doing it though. Similarly I wouldn't trust any of the cheap wrenches suggested (thanks) - plenty of disastrous stories on their reviews too! I don't actually have a 5-25, as most of my things are in the 4-8 range. I've used hand tools regularly but not professionally for decades, rarely using torque wrenches, just on more robust and much cheaper threads.

It is a massive diameter and the shoulder is immediately adjacent to the thread. As soon as it nips up, the torque is going to spike and you've got no chance of actually accurately setting preload in the fastening. Nipped up then QT is entirely appropriate. Any attempt to use torque to set this fastener is false precision.

OP's proposed contraption to set torque is false accuracy for other reasons as the luggage scale setup will likely be measuring statically (because it is cumbersome) and torque needs to be set while the fastening is in motion. But as stated before this is a fastening where any attempt to accurately set stretch is doomed to fail.

The o-ring means it is quite a frictiony fastening, so what you measure (in motion) is ebven less of a clear indication of what is going on in the fastening itself.

In my experience, bike manufacturer torque settings are not like aeroplane manufacturer torques. They're more guidelines. The earnestness with which some (GMBN etc) tell you to use torque wrenches or expect your bike to explode is a bad joke and usually accompanied by a demonstration of exactly how not to use a torque wrench. Bad torque wrenches, used badly against bad torque specifications is just a recipe for stripping threads (usually in soft alloy). FWIW, one Yeti torque specification on their rear suspension was sufficient to collapse the bearing it was preloading.

Incidentally, love the Topeak Combo Torq. As a spring type torque wrench it is worth a thousand clicky types.

Very few bike fasteners are truly stretched and most bike torque settings are given to prevent stripping threads in alloy. You're safer by: 1) using levers of proportionate size to the fastening, and 2) nipping up followed by QT.

Torque wrenches in bike workshops are so that Cytech qualified mechanics have a way of blaming a tool rather than ham-fistedness when they strip threads.

@peaslaker out of interest. Why do you prefer the spring type torque wrench over the clicky types?

@Jordan, these reasons:

1. Cheap clicky types change the point where they click based on shear forces and axial twisting reacting the torque; how you hold them changes the result you get up to and including stripped threads.
2. To use clicky-types properly, you should always approach the torque by setting a lower value first and then building up which very few users will ever do. This is a built-in behaviour of a spring-type, where you see the build up of torque. The fastener is not going to require many degrees of rotation to get from "half torque" to "set torque", but if you have no idea that you have reached half torque you have no indication that you're already in the danger zone for stripping threads.
3. Although it is getting better, there is still a "Dad-educated" mass of people who believe in "click once, click twice, click thrice and give it a bit extra". The only feedback is the click, so even if you educate good practice it comes over as so abstract that old habits persist.
4. Anecdotally, I've witnessed many new torque wrench owners launch topics on web forums about how a bike part must have been made of cheese because they used a torque wrench and the thread stripped. I've watched it happen in person with a user taking their brand new torque wrench from the box to the bike and insisting on using it because it is the new tool... leading straight to a stripped thread.
5. Spring types don't (typically) go out of calibration like clicky types do and clicky type calibration can vary significantly across the torque adjustment range.

The click-type sells you a pup. It tells you it is easy to use but to get safe and consistent results you actually need good technique and regular calibration checks.

I've formed my opinion by making my own mistakes to get here.

Its only a fork top, i wouldnt over think it, it not even a part under significant variable load that can work its way loose.

You only actually need a handful of torque settings:

Snug
Nip
Tight
FT
Find a long bar and hang on it

IME forks can creak awfully if this isn’t done up tight enough. My LBS did it for me for free.

@peaslaker some interesting points there, one or two I hadn't considered. I am forunate that I was trained to use a torque wrench correctly in an engineering environment but I have seen the people who like to give a second click just to make sure.

Never really thought about the calibration aspect of one type versus the other before. I have a nice little calibrated Norbar clicky one for bike use which I treat with kid gloves and a couple of bigger ones for car stuff. One clicky and one beam type. They probably have not been taken great care of over the years. I just went to the shed and tested one against the other. The clicky one clicks at way under value according to the beam one. Hmm.. I wonder which is most accurate. I can see how the clicky ones could go out of calibration quicker as the springs are seeing more use due to constant adjustment and resetting.

Well this is certainly an education. I think I might just get a rigid fork 😉 The contraption is out for sure, so is the 30-210 click wrench.

I wonder which is most accurate. I can see how the clicky ones could go out of calibration quicker

It is really hard for beam types to go out of calibration. They give torque indication just as a result of Young's modulus reacting to the input torque across the section of a piece of steel. Unless you attack then with a grinder, the indication will be the same. Clickys are reacting torque through a cam mechanism against a spring. Zero offset in the spring isn't apparent. Zero offset in the beam type is shown by it not reading zero at zero torque applied.

Calibrations are typically expected to be redone every 12months. I don't think that's adhered to by many hobbyists. Comparing to a beam wrench is a good practice but that's just telling you that the beam wrench is the more trustable tool.

@peaslaker Good explanation! Every day's a school day 🙂