Loud crack/bang from drive train/BB. Help.

Hungrycol

Can anyone help me. Have a funny problem around the drivetrain/BB area. It happens only when I start pedaling following freewheeling. I'd be freewheeling up to lights and they go green, I pedal hard and CRACK. Sounds louder the harder I pedal after freewheeling and only the CRACK. Once I'm pedaling again nothing happens. What the fub is going on? Any suggestions? It's only a relatively new occurance, last week or 2. The BB itself is fairly new, I got a new chain, small chain ring and cassette about two months ago. Could it be the freewheel?

bcmf

does it feel like the chain is slipping.
To me it sounds like a bearing in the BB has gone..

Hungrycol

Thanks bcmf. No chain is smooth. I initially thought the chain wasn't sitting right on the front chainring because while freewheeling a was pushing the crank horizontally. The crack it too loud for this though.

munchkin_utd

Have you checked the pedals/ cranks/ rear sprockets for play?
When bearings are gone then you should notice this.

Also, maybe the cranks are slightly loose on the shaft of the bottom bracket?
Pedalling you wouldnt notice it but when putting a large amount of pressure on the pedals, like taking off from a standing start, itd sound alarming enough.
(you will eventually notice it when the crank falls off the bike!!)
Before tightening them, put a bit of grease on the bottom bracket shaft to help eliminate any squeaking noises (or if theres none of that about the house just use butter! it works just as good!)

Diarmuid

I get that every now and then too. Similar circumstances. Very hard even to tell where the noise comes from. My bike is new and well maintained, never figured it out either

Hungrycol

Thanks munchkin. I cleaned my chain, cassette and chainset on Sunday and didn't notice anything obvious but I wasn't looking for it either. I think you might be right about the pedals though. They're old Look Delta's, tiny bit of play but they may have had their day. I'll check the cranks bolts this eve. Some great suggestions here. Thanks so much.

niceonetom

Haven't had that problem myself but from your description Hungrycol, and the fact that the noise follows freewheeling I'd also have a look at your hub. Maybe the clutch in the freewheel is in poor shape and is making the noise when it disengages? What kind of wheels have you? Some hubs are pretty easy to take apart and have a look, on others it's a lot harder and need unusual tools...

munchkin_utd

if i were in your position id just remove both cranks, "butter" them up lightly and screw them back on good and tight.
You would have that done in 10 minutes.

To overhaul the pedals is much (much much.....) more of a pain so i'd eliminate the crank possibility first before thinking about the pedals.

Hungrycol

Shimano Tiagra hubs. Honestly I think the problem might be here. I've put the wheels through some abuse and as a heavy rider would be heaving more that your average Joe. Everything has been changed except the freehub. Think shimano freehubs come off with allen keys. Oh hang on don't tell me I have to take out the axel to release the freehub I'll check the cranks first.

Hungrycol

munchkin_utd wrote: »

To overhaul the pedals is much (much much.....) more of a pain so i'd eliminate the crank possibility first before thinking about the pedals.

It would be a case of new pedals. I enquired form Park Tools about tools for Look Pedal disassembly as I didn't seem on their website. Sure enough they don't do them. I might get a cheap pair of Shimano pedals as I have Ultegra on my Cannondale and my DHB shoes with Look cleats fit better than my Sidi's with SPD cleats.

kona

What gear are you in when you pull off?? DOes it happen it the easiest gear too?

My bet would be the ratchet in your freehub has had its day. If it was your BB it would be constant, same with your cranks and pedals.

If its only happening when you pull away, this is when you are putting the most force on the ratchet and the bang you hear is it slipping.

Good news: shimano freehubs are a piece of piss to replace. You just take off the cassette, axle, bearings. Then get a 8mm allen key(needs to be long with a handle ) and it just screws off. Then put it all back together.

Second most likely is a stretched chain.

Hungrycol

Thanks Kona. Does mean I have to get new freehub or just give it a regreasing? If defo only happens when I pull away. Chain is fairly new so that's not it.

Edit. Donesn't really matter which gear I'm in when it happens, I generally only use 5th, 6th, 7th, 8th, 9th (9spd) on my commute.

Edit 2. I see a Shimano Free hub is only €11 in CRC. Maybe I'll just get one and swap it over at the wkend. Lying cadgers, FROM €11.18 for a 7 speed!

Hungrycol

Sorry again folks but would a FH-5600 freehub fit a 9 speed Tiagra Hub?

kona

Hungrycol wrote: »

Thanks Kona. Does mean I have to get new freehub or just give it a regreasing?

Nope, Just replace it as you know they are not expensive.

Hungrycol wrote: »

If defo only happens when I pull away. Chain is fairly new so that's not it.

Did you replace the cassette too? have a look at how the chain is sitting on the cassette.

Hungrycol wrote: »

Edit 2. I see a Shimano Free hub is only €11 in CRC. Maybe I'll just get one and swap it over at the wkend. Lying cadgers, FROM €11.18 for a 7 speed!

Ive no Idea, but I cant see any reason why it would not. 5600 is 105 so it should be compatible and 9spd.

Hungrycol

Thanks Kona, Yeah got a new cassette, chain and front small chainring about 2 months ago.

Appreciate the advice everyone.

tomasrojo

kona wrote: »

Good news: shimano freehubs are a piece of piss to replace. You just take off the cassette, axle, bearings. Then get a 8mm allen key(needs to be long with a handle ) and it just screws off. Then put it all back together.

What does one do to maintain a freehub? When I had a screw-on freewheel, I used to take it off every five months and drip some light oil into it. Can you do something similar with freehubs, or do you just run them till the give up the ghost, like sealed bottom brackets?

Hungrycol

I thought freehub and freewheel were the same thing! You can disassemble them and regrease them but you have to be wary of the spring in it. For €20 on CRC I'll get a new one in case the rachet (?) is knackered anyway.

kona

tomasrojo wrote: »

What does one do to maintain a freehub? When I had a screw-on freewheel, I used to take it off every five months and drip some light oil into it. Can you do something similar with freehubs, or do you just run them till the give up the ghost, like sealed bottom brackets?

Some you can service but I wouldnt bother most are so cheap to replace anyways.

tomasrojo

Hungrycol wrote: »

I though freehub and freewheel were the same thing!

By screw-on freewheel, I meant the one on the left in this picture.