Bottom bracket torque

[cyan]

I'm replacing a BSA bottom bracket (Shimano) on my bike. Shimano says torque both outer cups to 35-50nm, while a few videos online show people just tighten them without using a torque wrench. "Nice and tight" as they say.

Should we use a torque wrench in this case? I think you'd need a dual direction one that can register torque both clockwise and counterclockwise, which is going to cost >$100. If unnecessary, how tight should we go by hand feel or any other measure?

[dave thompson]

A beam-type torque wrench reads in both directions and costs far less than $100.

[Jef58]

35-50 nm is still pretty tight, tighter than you would think. That is a broad range for a torque spec. If it was critical, it would be at a max set number....which usually has a lot to do with the bolt size and thread type. It is good to use strict torque settings on bolts that clamp with more than one bolt to get even tightness, and of course not to damage carbon parts.

[Veloo]

I use a torque wrench for everything now but didn't for many, many years and never had a BB loosen - even on my Giant TCR C2 carbon frame.
Bigger problem was getting the BB off so I got a long ABS pipe for extra leverage.

If you swap wheels on your car at all, you could justify getting a torque wrench for that and use on the bike as well.

[oldpotatoe]

Originally Posted by cyan

I'm replacing a BSA bottom bracket (Shimano) on my bike. Shimano says torque both outer cups to 35-50nm, while a few videos online show people just tighten them without using a torque wrench. "Nice and tight" as they say.

Should we use a torque wrench in this case? I think you'd need a dual direction one that can register torque both clockwise and counterclockwise, which is going to cost >$100. If unnecessary, how tight should we go by hand feel or any other measure?

As mentioned, a torque wrench is never a 'bad' idea. Beam type, 3/8 inch drive and a 3/8 socket toolgood ones not expensive..GREASE and a properly prepped(faced and chased) BB shell also essential..

[eBAUMANN]

To be honest...I've installed countless BSA bottom brackets on my own bikes and bikes of friends and have never (not even once) bothered with a torque wrench and I have never (not even once) had a single issue with bb cups coming unthreaded.

"Nice and tight" is a good way of putting it, just snug it up and then kinda put your body weight onto the wrench, a couple "lunges" and that should do it. Just make sure whatever tool you're using has a nice solid connection with the cup and that you apply pressure as evenly/squarely as possible to avoid tool slippage.

I've really only found torque setting to be necessary when there is a risk of damaging/breaking a component from over-torque. Stem face plates/steerer clamps, seat post clamps, etc - these types of interfaces should absolutely be torqued to proper spec.

[joosttx]

35-50nm is a wide enough range where “nice and tight” probably is pretty accurate.

[ultraman6970]

Cyan...

1... grease the BB shell a lot....

2... put teflon tape in the cups, if you roll the teflon tape the wrong side will bulge so do the homework and figure it out the direction the tape needs to go. Put more grease around the teflon tape, this is to avoid creaks and avoid the cups getting fronzen later on.

3... put the BB and tight the stuff well... dont worry, the cups wont go nowhere because they will stop when they stop, is not like in other components where if you apply too much torque the pieces will round like for example a headset expander. The other thing is that you are using a BSA (english BB), those cups even if you on purpose you get them kind'a lose they will tight themselves because the bearings turn the opposite direction, the direction the cups tight. U really do not need a torque wrench.

Hope this helps.

[OtayBW]

Originally Posted by oldpotatoe

As mentioned, a torque wrench is never a 'bad' idea. Beam type, 3/8 inch drive and a 3/8 socket toolgood ones not expensive..GREASE and a properly prepped(faced and chased) BB shell also essential..

I just bought one at Harbor Freight for ~$25....

[Matthew]

I've also never used a torque wrench on a BB. They bottom out on the frame. They're only gonna thread so far unless you're the Hulk.

[Dave]

I've got an ancient craftsman beam type that works great. I also have harbor freight click types that can be bought for $20. Who says they don't work in both directions?

[FriarQuade]

A counter point, 30-50NM isn't actually that much torque, especially for the size of tools you're likely going to use for a bottom bracket. When I started using a torque wrench I instantly realized how grossly over tightened I had been installing them for years. What problems did this cause, creeks.

IMPO, BB's creak more often because they are or have been grossly over tightened than because they are loose. The absolute worst thing you can do for a suspected creaky bottom bracket is to tighten it some more. People like to put them in like the Hulk. That pushes the metal beyond the plastic state that keeps a fastener tight and causes it to take a set. Once that BB has been removed you've got distorted threads and the next BB isn't going to line up, which causes it to creek.

You're not going to break a frame or your teeth if you don't torque it but it will be more trouble free and quite in the long run if you get them in the recommended torque range.

[cyan]

Thanks all for all the knowledge and suggestions. Certainly helps put my mind to ease.

Re. torque wrench, mine (like most click types I've read) register clicks clockwise only and I didn't realise there are significantly cheaper dual direction ones out there than the Park Tool TW-6.2

[JanG]

If you are going to use a torque wrench then it is critical that the fastener and threads are prepped the way the manufacturer specifies. That may mean no grease. The reason is that the torque spec is just a way to relate to the amount of stretch or spring force created in the fastener. The variability of friction in the male-to-female threads can lead to differences from what was intended. For example, greasing an assembly that was intended to be assembled 'dry' can lead to too much stretch in the fastener because the friction is too low. The reason that critical joints, like head bolts in an an engine, are often specified as torque+angle is to eliminate the friction variability. The fastener is torqued to an initial value which come close to the yield stress, then it is turned further through a specified angle to ensure that is has plastically deformed. The downside to this is that the fasteners are one-time use only.

Jan G.

[Mikej]

I go with German Tight - gutentite or American - good and tight.