# Torque Wrenches: in/ft vs. lb/ft



## CrashTheDOG (Jan 4, 2004)

As I've reviewed several service manuals I’ve noticed some measure the amount of torque required in “in/ft” and others in “lb/ft”. Is it possible to purchase one torque wrench for all my bike maintenance or do I need one for "in/ft" and one in "lb/ft"? If I can get away with one which should it be, and can I simply convert "lb/ft" to "in/ft" or vice versa?


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## Speedub.Nate (Dec 31, 2003)

*The most well rounded, cost effective wrench...*

...is the beam type from Craftsman ($20) or the Park TR-2 ($35). They are both the exact same wrench, the difference being in the scale (Craftsman shows ft-lb; Park shows in-lb). Whatever the case, you can multiply / divide by 12 to convert from one to the other.

In my opinion, low range in-lb wrench isn't useful unless it gets up to about 150 in-lb. Below that, and it will have limited use. Too much above that, and you'll lose some resolution on the scale and you'll be just as well off with the Craftsman wrench only.

The items that I consider important to measure torque on (BB, crank, stems, pivots & shocks, disc brakes) can be installed with the Craftsman model only, however of those, some of those that fall into lower ranges will use the very low end of the scale and may be subject to some imprecision.

















So as you can see with the Craftsman, a 55 in-lb Avid rotor bolt would be torqued an indicator's width shy of the 5 ft-lb mark; a 90 in-lb caliper bolt would be torqued would be taken up to the 7.5 ft-lb indicator. The 48 in-lb required by Thomson stem bolts translate to 4 in-lb, again a judgement call at a needle width shy of the 5 ft-lb mark.

On the other hand, it'll have no trouble with the 35 ft-lb required by most cranks and the 50 ft-lb required by most bottom brackets.


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## CruzinJapan (Jan 12, 2004)

*You will most likely need two wrenches.*

Small parts like brake rotor bolts, suspension bolts, stem bolts, etc. are normally in the in/lb range. You will notice that it's usually things like the BB are normally in the ft/lb range.

The trouble you will run into in finding one wrench and converting is that the torque wrench that is used for the BB, will not go low enough for the smaller parts. The torque wrench for the smaller parts will not handle the BB.

If you manage to find a wrench that will cover all fasteners on the bike, just multiply in/lbs by 12 to get ft/lbs. Remember, there are 12 inches in a foot. So, to get from ft/lbs to in/lbs, divide the number by 12.

Also, you will run into some things specify torque in Nm. Here is the conversion for that:
1Nm = 8.8507458 in/lb
1Nm = .7375621 ft/lb

Good luck,
Chris
BTW, I have two torque wrenches.



CrashTheDOG said:


> As I've reviewed several service manuals I've noticed some measure the amount of torque required in "in/ft" and others in "lb/ft". Is it possible to purchase one torque wrench for all my bike maintenance or do I need one for "in/ft" and one in "lb/ft"? If I can get away with one which should it be, and can I simply convert "lb/ft" to "in/ft" or vice versa?


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## ToddM (Feb 3, 2004)

The ideal answer is of course to get both.

However if you only get one, get one that is 3/8" drive and goes to about 250in/lbs for bike use. Sears should have one or two models that does that range. It will work on everything on a bike, aside possibly crank bolts and BB shells, depending on the manufacturer. Most bolts on a bike are between 20-100 in/lbs and they are much more picky about being overtorqued than a crank bolt or BB shell. Generally I torque my BB cups and crank bolts to 250 in/lbs. On a BB shell I will tighten it a bit past that without the torque wrench. I've done my crank bolts to 250 in/lbs for 10 years and never had one loosen. Though most isis crank bolts seem to recommend in the 35ft/lb range 

The problem with going with a ft/lb version is most of them start too high to use on 90% of the bolts on your bike such as the stem or brakes etc. Even the 100 in/lb shock mount or chainring bolts is less than 10 ft/lbs most ft/lbs torque wrenches don't even start that low. The models on sears website start from 15-20 ft/lbs thats too much for anything but crank bolts or BB cups.

So if you really want it perfect, buy both, if you only buy one, buy a in/lbs that ranges up to around 250 or so.


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## Xyzzy (Feb 14, 2004)

The small one from Sears works great, but anything much less than 25 inch pounds is dicey because it is a clicker model and they are not too accurate at the bottom end of the range...

Sears also sells a nice red box to store them in... I think the box is like 8 bux and the 3/8 wrench is around 60 bux...


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## fred3 (Jan 12, 2004)

*Kind of expensive...*



Xyzzy said:


> The small one from Sears works great, but anything much less than 25 inch pounds is dicey because it is a clicker model and they are not too accurate at the bottom end of the range...
> 
> Sears also sells a nice red box to store them in... I think the box is like 8 bux and the 3/8 wrench is around 60 bux...


in my opinion. I bought the Park that goes up to around 400in/lbs(also show nm) and it's good for just about every single torqueable(is that really a word? ;-) fastener on the bike and runs less than $30.


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