Clunks from Bottom Bracket

[The fat commuter]

Over the last few weeks I've noticed a 'clunk' as I pedal. There are two per revolution of the pedals - worse as my left foot goes past the 12 O'clock position. I did think that it was a loose crank but, having waggled stuff about a bit with my hands, it would appear to be loose within the bottom bracket. As I grab a pedal/crank in the 12 O'clock position and push it towards the seat tube, there is a tiny bit of movement on both sides. It's only about 1 mm of movement (if that), but there is movement and there is the same clunk when I do this.

Anyway, I need to get this sorted. Not sure whether it just needs tightening up or whether there is wear within the bottom bracket and it needs replacing. I'm still learning with this maintenance malarkey so I may take the bike down to the Bike Kitchen to do the repair where there is an assortment of tools and advice.

Now for the question. Do I assume that the bracket is just loose or do I assume that it is worn? If I assume that it's worn, I may as well buy a new BB in advance. Do I have to take the bracket to bits to find the size or is there a way of working out the size in advance (like with a tape measure)?

This is the bike http://www.ridgeback.co.uk/bike/Speed . The specifications states that it is a cartridge BB. The bike hasn't done that much mileage - I've covered about 1,200 miles in a year. Half of those miles have been uphill mind carrying seventeen stone plus.

Many thanks for in advance for any advice received.

[beardy]

Your Bottom Bracket cartridge has to match your crankset, that is given in the link as an M171.
A quick google shows that you need a 122.5mm axle length, it doesnt show what width the shell is, ie 68 or 73mm.

http://www.google.co.uk/url?sa=t&rct=j& ... 0786,d.ZGU

It is most likely 68mm but no means sure to be so. Also almost certainly English thread.

Unfortunately out of stock here at the moment as this is a durable BB at a bargain price.

http://www.chainreactioncycles.com/shim ... -prod71369

[NATURAL ANKLING]

Hi,
I think that there was that much play when I started riding my bike about 3500 miles ago, I have just changed the BB as there was about 3 - 4mm
If the bearings are not rough then they will go on for sometime.
Any event you will need two tools, Crank extractor and a BB spline tool.

Dont know the bike but if its External bearing BB then some other tool

It is possible that the BB is loose in the frame, so you need to check that out, else damage to the frame might occur.

[NATURAL ANKLING]

Hi,
I just like to add that most people probably would not tolerate more that 1 - 2 mm of play.
Better quality BB's tend to go rough before there is much play, mine was a cheapo.
I am running my bike on second hand parts

[MikeF]

If you try to tighten or need to remove the BB cartridge remember the thread will be normal on the near/left side ie clockwise tighten, but left hand thread on the off/right side ie clockwise loosen. 1200 miles should be no mileage at all for a BB. Drop the chain off the chainwheels and spin the cranks. Any rough sound or other sign of roughness?

[The fat commuter]

Many thanks for the answers. Gives me a bit of info to go on but it looks like I'll have to take the cartridge out to find whether it's 68mm or 73mm. I'll arrange a visit to the Bike Kitchen workshop to get this sorted - they will have all the tools there as well as the expertise to offer advice.

Regarding the bike only doing 1200 miles before it starting to clunk. I just assumed that it's because it's a cheapo bike. I have a road bike hung up in the garage that is currently out of service but that must've covered well over 20,000 miles with hardly anything needing changing. That said, it was/is a much better made bike that this one.

Cheers

[PT1029]

Check the BB cups are tight, if they are tightish, they can rock on the threads as you pedal (the knock). When/if you check the BB cups are tight loosen the LH one a bit, so you can ensure the RH cup (has LH thread as mentioned else where) can be fully tightened into the frame. Once the RH cup is fully tight, tighten the LH cup (assuming its a cartridge - if its an old cup design, you need to adjust it correctly).
I often see newish bikes (not always cheap ones!) where the cups rock on the threads.
If its a cheap bike, suggest you actually fully remove the cups before tightening, then you can find out if the threads were greased or not. Add plenty of grease (or copper slip) so you know the cups will be easily removable in afew years when the bearings wear out.

[MikeF]

You should be able to measure the BB shell width without removing the BB. It's likely to be 68mm. I see from the website that the BB is just mentioned as cartridge whereas with slightly more expensive Ridgeback bikes the BB is specified as Shimano. Maybe the cartridge is the problem as it's cheap.
Even on non cheapo bikes I wonder how much pre sales adjustment is made on bikes, eg cones, headset etc

[MartynWheeler]

Also check your seat post - mine was clicking recently and I took it out, cleaned, and regreased - now there is no more clicking!

[The fat commuter]

Went to the bike kitchen tonight. Took everything apart and the bottom bracket does need replacing - there is some play in it. Got the measurements off the bracket. Put it all back together. The good news is that the clunking (which had turned into more of a clunk/creak) has stopped. I will order a new one but I can fit it at my leisure.

[NATURAL ANKLING]

Hi,
Did the cranks come off easy
Did the BB come out easy