Bottom bracket UN55 loose cup

[Leaway2]

I have just received a new UN55 BB. The loose cup is not a close fit on the body. this normal? The old RPM bearing cup is a snug fit on the bearing body.

 

[4F]

Correct, it is more of a guide and to keep crap out than to hold the BB in place. Fitted the same one to my bike a couple of weeks ago.

 

[Leaway2]

Thanks 4F. It rattles round in the cup, its very disconcerting. I have Googled this and other peeps are asking the same question. I will be fitting it tomorrow

 

[4F]

I am pleased to say mine makes no noise so no problems here.

 

[Leaway2]

I am pleased to say mine makes no noise so no problems here.

Just out of interest, what bike? This is for a Specialized secteur.

 

[4F]

Mine is an old peugeot converted to run fixed gear. I got a UN55 68 x 108 to replace my old UN 54 version that was staring to groan.

 

[fossyant]

Once fitted it will be fine. These cheaper 5x series BB's use the plastic cups which will mould to the BB once it tightens up. It won't move.

Personally I prefer the alloy cups, but they are like rocking horse poo ! Got alloy on my best bike and trainer road bike (Dura Ace and Ultegra cartridge). Plastic on the MTB and Fixed commuter both UN 53/54 - no issues.

 

[4F]

Actually Foss the Un55 has an alloy cup where as the un54 had the plastic one

 

[Leaway2]

Yes it has the alloy cup. Anyhoo its in. Just going to have a and take it out for a quick spin. Thanks for the replies.