Acceptable play in a bottom bracket?

[alicat]

How much play is acceptable in a bottom bracket, as measured at the end of the crank arms?

I have a Giant Expression N7 hub gear bike, which has a semi-cartridge bottom bracket ie adjustable at the non-drive side only by means of a Shimano-type JIS cup and lockring.

A couple of months ago I took the bottom bracket out to test my fettling skills. The other day I noticed play in the cranks. I've tightened the cup and refitted the lockring. There is no visible play in the bottom bracket axle but about 1-2mm at the end of the crank arm when both cranks are fitted. Is this acceptable?

If it is going to cause harm then I would rather fix it but I am conscious of knowing when to stop bearing in mind my fettling skills and aptitude (fair to middling only).

Thanks in advance for any guidance.

 

[Profpointy]

Essentially none - or more precicesly, if you can feel any play, there's too much !

 

[J1780]

There should be no play in it at all.

 

[alicat]

Okay thanks - I will give it another go.

 

[Profpointy]

Basically adjusting bearings with some play, is you do it up a bit, then find it's binding / stiff, then slack it off a bit, then there's a bit of play - so round and round you go till it's "just right". Then you do up the locknuts (if any) and find you've tightened up a bit too much, so round and round you go again. Eventually you work out how much slack to allow before doing up locknuts and then it's perfect. i'm exagerating a bit - all the above shouldn't take more than 10 minutes

 

[BimblingBee]

If I understand you correctly you are referring to a cartridge type BB with a plastic cup on one end (may be metal depending on spec). With these you cant adjust the actual bearings, if it feels notchy when rotating by hand, excessive play, or creaks, clicks, grinds when pedalling then it's time for a new one. They are pretty cheap just make sure you get the right axle length.

Riding it as it is won't cause any damage and its very unlikely to fail before it get so loud and annoying you replace it anyway.

 

[alicat]

It's a semi-cartridge bottom bracket so you can adjust the amount of play. It has a metal cup like the cartridge types plus a lockring on the non-drive side only.

There is nothing wrong with the bearings. I took it out to regrease it and check what state the frame was in. Now I'm having trouble removing the play without making the cranks too stiff.

I don't want to buy a cartridge bottom bracket because I need a K-type that is hard to come by (the bike has a chainguard mounted from the bottom bracket) and at some point I will probably change the cheap cranks the bike came with and at that point I will get a new bottom bracket to suit the new chainline.

I'm halfway through the adjustment process so wish me luck.

 

[RecordAceFromNew]

It's a semi-cartridge bottom bracket so you can adjust the amount of play. It has a metal cup like the cartridge types plus a lockring on the non-drive side only.

There is nothing wrong with the bearings. I took it out to regrease it and check what state the frame was in. Now I'm having trouble removing the play without making the cranks too stiff.

I don't want to buy a cartridge bottom bracket because I need a K-type that is hard to come by (the bike has a chainguard mounted from the bottom bracket) and at some point I will probably change the cheap cranks the bike came with and at that point I will get a new bottom bracket to suit the new chainline.

I'm halfway through the adjustment process so wish me luck.

For play adjustment you don't need luck, all you need is a marker pen and a sticky tape wrapped around the bb shell, and put a mark on the adjustable cup like the hand of a clock and leave a mark adjacent on the tape every time as you iterate, which will help you iterate with certainty quickly towards the correct preload by letting you know exactly where you have been previously.

With a chainguard I expect you need a E-type cartridge bb if you were to replace your existing bb, and which are increasingly rare as you said. However it seems a possible reason why Shimano is running them down is because Hollowtech 2 mtb bb's can accommodate any E-type chain guard / front mech by leaving out one of the two 2.5mm drive side spacers. So one way of bypassing the E-type cartridge bb sourcing problem is to go for HT2 mtb chainsets.

 

[alicat]

However it seems a possible reason why Shimano is running them down is because Hollowtech 2 mtb bb's can accommodate any E-type chain guard / front mech by leaving out one of the two 2.5mm drive side spacers. So one way of bypassing the E-type cartridge bb sourcing problem is to go for HT2 mtb chainsets.

Thanks for that, RecordAce. I want to change the cranks from 170mm to 165mm (bit of a whim for a shopper bike I know) so I may have a look for a suitable chainset. I really like my shopper bike so I don't mind upgrading it.

The task is beginning to get on my nerves - it's hard to stop the bottom bracket tool slipping under pressure - and the adjustable cup seems to undo when I tighten the lockring.

 

[alicat]

Well, I think I've fixed it.

It will give me time to research 165mm Hollowtech II silver single chainsets. That should keep me busy for a while!