I'm going to pick up a torque wrench - I'm prone to overtightening bolts! There are enough threads on whether or not a torque wrench is necessary, so let's not get into that here. Assuming I want one for my bike build and ongoing maintenance/repair, is this one sufficient: Beam-type, 3/8" drive, 0-75 ft-lbs (link). And I guess I'll need a set of hex bit sockets (link).

Is a 75 ft-lb wrench sufficient for bottom brackets, or do I really need a second, larger torque wrench? Can I just slip a pipe over the end of the smaller wrench for more leverage? Or is accuracy the bigger issue?

Yes to both. This won't be appropriate for smaller fasteners, but will work fine for the bigger ones like BB and crank.

If the 0-75 ft-lb rated wrench isn't good for small fasteners, what should I get? What do you mean by "small" - 4-5mm stem clamp bolts?

If you look at the torque charts on the Park Tool website, about the highest torque they list is on the order of 50 ft-lbs for certain BB cups, but even that is pretty extreme IMHO. Most of them are more in the ballpark of 25-35 ft-lb. Also, I have the Craftsman wrench that you linked to, and it has plenty of leverage for installing BB cups (removing stubborn cups is a different matter, but you shouldn't be using a torque wrench for that!)



Actually, lately I've stopped using a torque wrench for cartridge bottom brackets. It always seems like when I tighten them to spec, the bearings bind up and I have to back off the torque. This includes high quality cartridge BB's like Phil Wood and Campy Centaur. Instead I use threadlocker and just tighten the cups until just before the point where I start to feel resistance in the bearings.

75ft is like overkill unless you're installing bolts that hold a skyscraper up.

Park makes one that goes up to, I think, 60 in-lb. It uses 1/4" drive so you'd need an adapter or else find a source for 1/4" metric hex sockets (they're not too common but I've seen them around, e.g. Ace Hardware, Pedros, S&K Tools). As you mentioned, you would use this for stem bolts, seatpost clamp, cable pinch bolts, etc. For the smaller fasteners the concern is usually in overtightening them and either snapping the bolt or damaging the component being clamped (especially if it's carbon).

You need a 1/4 drivve 20 to 200 inch-lb and a 3/8 drive like you picked. Less than 20 inch-lb would be nice.

If there is a store near you these are ususally on sale foe $20. I checked mine at work and it was within specification. The click is not as crispe as more expensive wrenched. Digiatal will run you a few hundred.

https://www.harborfreight.com/cpi/cta...temnumber=2696

https://www.harborfreight.com/cpi/cta...Itemnumber=807

For the truck.
https://www.harborfreight.com/cpi/cta...Itemnumber=808

www.mcmaster.com
7767A11
Electronic Rotary Dial Torque Wrench 1/4" SQ Drive, .62-6.25 ft-lbs Torque, W/Std Battery
In stock at $356.66 Each
7767A14
Electronic Rotary Dial Torque Wrench 3/8" SQ Drive, 5-50 ft-lbs Torque, W/Std Battery
In stock at $356.66 Each

I don't like beam type but here you go.
https://www.parktool.com/products/det...13&item=TW%2D1

Arrrghhh! So I gather I need TWO torque wrenches. A 3/8 drive with a max of ~50 ft-lb and 1/4 drive with a max of ~60 inch-lb. And then in addition to the 3/8 hex bit socket set, I'll need a 1/4 to 3/8 drive adapter (like this?).

Just realized I'll also need a splined tool for the BB cups - the Park BBT-19 looks like it will work with a torque wrench.

A suggestion:

If you're not going to use a 3/8" torque wrench often, many auto parts stores offer free loaner tools. As to the 1/4", buy one at Harbor Frt. It's a good idea to us a torque wrench on carbon parts.

Too high torque wrench for a bicycle. Most you need to get to is about 30 ft/lbs for most bicycles, and most of the important torques for a bicycle are low, in the <10 ft lbs range. A wrench with that high a limit will not accurately measure the low torques you need to measure on a bicycle.

That's why I was thinking I'd need 2 wrenches. 1/4 drive up to 60 in-lb and a 3/8 drive up to ~50 ft-lb. That should cover all the bases, right?

Cranks and cassettes - 30 ft lbs == 360 in-lbs == 40 Nm.

BB's are often spec'd to 60 Nm == 540 in-lb == 45 ft-lb.

That's near or beyond the capacity of 1/4" wrenches, and that's an awfully short lever arm for those torques especially with the length of the adapters and tools involved. I wouldn't use a 1/4" wrench for cranks, BBs, cassette lockrings, etc. Just too small.

3/8" is perfect for those; I usually use a 1/2" wrench for them.

60 in-lb is only 5 ft-lb. Way too small for a bike and too small to overlap a 3/8" wrench. Figure any wrench is inaccurate below about 15% of its range. In a little wrench you want something that will go up to 250 in-lb or so.

Please also be aware that if you are using a torque wrench to precisely tighten fasteners, then you need a precise torque wrench. I've got some great stuff from Harbor Freight, but I would not buy a torque wrench there.

Get a Snap-On or at least a Craftsman. Don't get a no-name unit that hasn't been calibrated.

I wonder why Park sells two torque wrenches with a "gap" between them:
TW1: 1/4" drive, 0-60 inch-lbs
TW2: 3/8" drive, 0-600 inch lbs

So even these 2 are not sufficient?? Man, this is way more complicated than I initially figured.

pmt: I'm not worried about calibration since I'm looking at beam wrenches, not clickers.

Just about any beam wrench, even a cheap one, is good enough for a bicycle. I know we love our bikes, but a cheap one is close enough. The good thing about beams is that the calibration consists of zeroing the pointer.

Never use a pipe on a torque wrench. The numbers are calibrated from the handle center, beams have a pivot in the handle, to the center of the drive. The handle should be "floating" on the pivot when you use it.

For any kind of accuracy, you should only use the wrench for the middle 1/3 of the scale. I wouldn't worry about that too much unless you are working on the space shuttle.

In previous posts about torque wrenches on this forum, it was determined that the Craftsman and the Harbor Frt. clicker-type wrenches are made by the same folks (in Taiwan). I've looked at both and they sure look the same to me. I've also compared my Harbor Frt. units to beam wrenches, and they're right on the money. You can hook the two together and read the beam as you put pressure on the clicker and see when she clicks. If you want to save a few bucks, go with a beam type, they're certainly more fool-proof, but not as convienant. For that, Sears is probably the best choice.

Just buy a 1/4 drive, 3/8 inch drive and Allen sockets. To me the 1/4 drive is used most since I don't want to over tighten my seat clamp, seat post clamp, handle bar clamp and other small stuff I adjust often. And I want to be consistent.

I did back off a half turn re-tighten various fastener the first time with the torque wrench to get an idea of the torque to put it back where it was. I did find the original seat clamp torque was much lower then the Trek book says but it did slip back a few weeks ago. The seat post torque was also lower but it has not slipped.

Nashbar's wrenches too.

Yep. My little HF clicker is just about spot on. 0-200 in-lb, too. Dual scale. For about $20 you can't beat it.

I'm about to embark on building up a carbon frame set, with carbon parts. I've been wrenching for several years, so I have a clue, but I'm going to buy a torque wrench. There are two harbor freight wrenches mentioned above.

https://www.harborfreight.com/cpi/cta...temnumber=2696

and

https://www.harborfreight.com/cpi/cta...Itemnumber=807

I'm confused. The 1/4" has a smaller drive, but is rated for 20 to 200 pounds. Meanwhile, the 3/8' has a larger drive and is rated 0 to 80 pounds. For bike work, I think I want the lower poundage for most carbon pieces (stem, bar, seatpost). So I would want the 3/8" drive, correct? The sizing seems counterintuitive. Please, help me out here.

The 1/4" drive is rated at 20-200 INCH-pounds. This would be about 1.6-16.6 FOOT-pounds.

The 3/8" drive is rated at 0-80 FOOT-pounds.

Eric

Torque is a rating of a certain distance and force ... FTLBS, INLB, INOZ.

The indicators on a torque wrench are based on the length/distance from the input socket to the handle ... more specifically the hand grip. If you add to/change the length in anyway ( "slip a pipe over the end of the smaller wrench for more leverage", add an extension, etc) you need to do the calculations for the new length. This changes the actual torque applied from what the wrench is indicating. Snap-On provides a need little slide calcuator that will figure it out for you.
So ... yes you can add to the leverage ... as long as you do the torque applied calculation for the new length.

As far as accuracy, the tool generally needs to be more accurate than your tolerance. If your torque spec is say 20 +/- 2 ... that's 10%. If your torque wrench accuracy at 20 is better than 10% (IE +/- 8% of IV), it's generally good enough.

So even if HF torque wrenches are not as accurate as others, they maybe good enough depending on the torque spec called out.
Most of the general use Snap-On break over wrenches are +/- 4% of IV CW. The dial wrenches are +/- 2%.

See what the required torque tolerance is and then get a torque wrench at least accuarate enough to do it.

Go with the 1/4 inch drive. 20-200 inch-lbs is right where the critical fasteners, eg fasteners joining carbon fibre, and most other small fasteners which make up the majority of fasteners on a bicycle, are.

On the rare occassion where you will tighten a square taper crank bolt or a BB, you can get away with the "nice and tight but not too tight" method, meaning just doing it by feel, with no torque wrench.

The 1/4" drive is 20 to 200 Inch pounds, the 3/8" drive is 0 to 80 Foot pounds, there are 12 inch pounds in 1 foot pound, there are several sites on the internet to convert foot and inch pounds to metric.

An earlier thread on torque wrenches advised against clicker style because you can apply too much torque on small bolts before the clicker activates even when properly calibrated. The beam type were judged better for bike work.

I have one torque wrench. I made it for about $5. It is quite accurate. It uses a fisherman's scale and a steel bar. I calibrated the scale with weights of a known value. Send me a PM for more details.

Yep, if you understand the concept of torque, as you clearly do, which a force applied in a perpendicular direction to a lever, you can get very accurate torques using all manner of things. The axle nut on my car has to be torqued to 207 ft-lbs. I'm not going to spend over $100 for a torque wrench I will use a handful of times. But I just convert the torque to inch pounds, divide by my weight in pounds, and the result is the number of inches along a breaker bar that I have to stand in order to apply the correct torque to the axle nut.