Upgrading Crankset & BB

[Cycle Fan]

I'm wanting to upgrade my crankset & BB and would like to try and do it myself. Can anyone tell me how to ensure I buy the correct BB for the correct crankset. What is the difference between English and Italian thread? Does the frame determine the BB size or the crankset? Lots of newbie questions - but its the only way you learn!

 

Thanks in advance for the advice...

 

[Johan Bornman]

What's wrong with your current crank and BB? Put that money into your savings or pension fund.

 

I know you won't listen so here goes:

 

BBs are determined by the width of the BB shell on the frame. A 68mm shell is an English BB and a 70mm shell is an Italian BB. Further, the British/English BB is threaded left and right hand on the right and left hand respectively whilst the Italian BB is threaded right hand on both sides.

 

They wont fit, the Italian BB is also bigger in diameter. Italian BBs are dying out and the world is being taken over by British BBs.

In addition, BB axles also differ. You get square taper types and splined types and one-piece cranks which are actually two pieces.

 

Once you are at peace with that, you are ready to learn about external and internal BB cups. The later is the dog's bollocks....or so they say.

 

By upgrading your BB from an old square taper to external BB you are downgrading bearing durability. But no shop or brochure will tell you that. Keep it a secret.

 

To upgrade the BB yourself you will probably need a special tool to remove the old BB and another special tool to insert the new BB. Once you have removed the old BB you can throw the old tool away since you won't need that again.

 

Futher, you'll have to contend with anti-click strategies, Q-factors, compact vs standard crank and round vs oval chainrings.

 

 I suggest you open a beer and put the money in your pension fund.

 

Oh yes, and go for a ride.

[Dicky DQ]

 you are ready to learn about external and internal BB cups. The later is the dog's bollocks....or so they say.

 

By upgrading your BB from an old square taper to external BB you are downgrading bearing durability. But no shop or brochure will tell you that. Keep it a secret.

 

Why??

[Cycle Fan]

Thanks Johan, sheds some light on the confusing world of the BB...

[Canaris]

What ever happened to rding it until it breaks or is beyond repair, and then replacing it?  I believe this "upgrade" culture is a clever marketing ploy to get people to buy stuff they don't need.

[Johan Bornman]

What ever happened to rding it until it breaks or is beyond repair' date=' and then replacing it?  I believe this "upgrade" culture is a clever marketing ploy to get people to buy stuff they don't need.

[/quote']

 

Hey, voertsek. I'm the cynic around here.

[Johan Bornman]

 you are ready to learn about external and internal BB cups. The later is the dog's bollocks....or so they say.

 

By upgrading your BB from an old square taper to external BB you are downgrading bearing durability. But no shop or brochure will tell you that. Keep it a secret.

 

Why??

 

Hundreds of small balls far too small for the intended load.

Closely packed balls so they cannot shed ingressed dirt to neutral recesses in the brearing.

Small and poor seals not capable of dealing with the overwhelming attack from water and dust and mud.

Outboard location puts the bearings directly in the firing line of dirt and mud.

Premature failure due to the above.

The new BB30 standard looks promising. It still has a large hollow axle but more space for larger bearings. I can't wait to discect my first BB30 - any volunteers?

 

[Daxiet]

To answer the why not wait until it breaks: Where's the fun in that? But even better, why wait for something to fail while out on the trail/road or worse in a race.

If converting from the older internal BB to the newer External BB you should get the shell faced to ensure the faces are parallel. Failure to do so may result in premature wear of the previously mentioned not so durable External BB bearings.

 

To my knowledge the External BB is now favoured to all others due to the reduction in weight.

 

Removal of old style BB's with the correct tool is very easy, keep in mind the thread directions that Johan mentioned, so far I have yet to bump into Italian BB's. The External BB is equally easy to install/remove, the Shimano cups seem to all come with Tightening direction printed on the BB cups.

 

Go buy the tools you need and get the job done, just be careful not to cross thread when re-installing. Tighten by hand gently and then attack with the correct tool to tighten.

 

 

[Johan Bornman]

Cut cut cut cut cut

 

 

 

If converting from the older internal BB to the newer External BB you should get the shell faced to ensure the faces are parallel. Failure to do so may result in premature wear of the previously mentioned not so durable External BB bearings.

 

 

 

 

This is another one of those famous bicycle myths that refuses to die. I think this one was perpetuated by someone who invested big-time in BB facing tools.

 

Whilst it is true that a BB shell that doesn't have two parallal faces will bind a BB, this should be picked up by the mechanic quite easily. All he has to do is spin the crank upon installation and if it doesn't spin freely, THEN have the BB shell faced. If it spins freely, why bother. I'm yet to find one that isn't parallel.

 

 

 

 

[Daxiet]

May be unlikely to find a BB shell that is horibly off parallel, but when converting from an internal to external BB, the BB faces generally would have been beautifully painted, hence no guarentee that the faces are parallel.

 

The crank spin test I believe would only present a noticable result if you had a major discrepancy in the faces. The bearings by design would mask small issues, but over time they would fail prematurely.

 

No one ever suggested forking out a couple K on a BB Facing tool, but to drop your frame off at a shop and have them quickly slap their over expensive facing tool on will by a tiny cost to ensure you start on the right footing. Perhaps a waste of time and money, but it may save you in the long run.

 

By the way most people who are pro facing recommend re-facing each time you replace your BB, now that I think is a load of ... however, if you have never had the BB faced (internal BB convert), I give it the thumbs.

 

[Johan Bornman]

Cut cut cut cut

 

The crank spin test I believe would only present a noticable result if you had a major discrepancy in the faces. The bearings by design would mask small issues' date=' but over time they would fail prematurely.

cut ut cut cut .
[/quote']

 

Only a noticeable result will make the bearings fail. If that weren't the case, most of today's fancy wheels with cartridge bearings would fail prematurely. Those bearings (as well as BB bearings) are all designed for radial loads but can tolerate small lateral loads. Lateral loading is how the play on cartridge-bearinged wheels is taken out. You screw in the "cones" until the play is gone and by definition this causes a side load.

 

Anyone who has done this will know that it takes just a bit of finger pressure to make the wheels bind.

 

The same for BBs. If you do the spin test anyone but the very unskilled will notice binding immediately.

 

I stick to my story that BB facing is over hyped. Paint is not applied in great big blobs with a putty knife.

 

 

 

 

[Daxiet]

Enough cutting for one day, till next year.