A couple of problems.

[Bristol Dave]

I have an intermittent 'knocking' that seems to come from the bottom bracket and is in tune with my cadence. This comes and goes and I have checked everything for tightness and all seems okay.

My second issue is an occasional slip of the chain when piling on the pressure - usually up hill. I have checked over the rear dérailleur and it looks okay. However it does seem more 'in line' when I'm on the bike than when examining it dismounted (me not it).

Anyone come across these sort of things before? I'm reluctant to take it to my, very reliable, LBS due to the intermittent nature of both problems. The bike is only around 6 months old and is a Marin Kentfield FS. I only use it for a short commute and I try not to treat it roughly - pot holes excluded.

BD

 

[swee'pea99]

6 months? Is it not under guarantee?

 

[e-rider]

the knocking sound from BB area could be any number of things. We could all suggest stuff but we'd be guessing without actually seeing the bike.

My guess is the pedal bearings. If you have access to another set of pedals try swapping them over to see if that helps (if the others are decent that is).

As I said could be loads of stuff; eg. BB, front mech height, angle, adjustment, gear alignment, chainrings, pedals, cranks, chain, cassette, rear hub, rear mech etc etc..

One thing to get checked are the BB cups. If one has come loose and you continue to ride the bike, this would damage the thread in the frame and ultimately this would require a replacement frame.

As for the chain slipping, it happens when the chain is worn or if you put a new chain on worn chainrings and freewheels. Your bike is new so it's more likely that the gears just need adjusting. Which might also solve your other problem.

 

[summerdays]

What part of Bristol are you in? I noticed on the better by bike website that you can take your bike to Horfield Sports Centre for a free check and it even covers minor parts. Its on specific dates and you need to book it in advance.

http://www.betterbybike.info/bike-check-up-at-horfield-leisure-centre

 

[02GF74]

I had awful knock from BB - turned out the pedal - splined BB - was loose. a dab of grease and tightening up all was well.,

worth checking, especially on a new bike to allow it "to settle."

 

[Big John]

Hiya Dave

As the bike is only around 6 months old I reckon the bottom bracket should be fine as Google tells me it's a cassette one. A simple check by trying to rock the cranks to see if there's any play in the bottom bracket should rule that out. If there's any play then replace it.

It' more than likely to be a noise coming from the pedals. Not having seen the pedals I can't comment on how best to put things right but usually it's pretty obvious how they come apart. If you're happy to invalidate any warrantee you might have then take them apart, grease and re-assemble.

As for the chain slipping this is symptomatic of a worn chain or worn cassette or both. Check Sheldon's website for how best to measure a chain for wear (a good 12 inch metal rule is useful for this). If it's worn then replace with a new one. Chances are you'll then need a new cassette otherwise the jump will be more pornounced than before! If a new chain/cassette doesn't cure it (and it should) it could be the freehub. These can be replaced easily enough but you'll need a big allen key.

I'm surprised you're having these problems at all, to be honest, if the bike's only 6 months old. I can only assume you must be piling the commute miles in!

 

[Norm]

Are you sure that the chain is slipping and not just jumping between gears? As tundragumski suggests, cable stretch may have that as one of the symptoms.

Has your bike been serviced / checked at all since you got it? Most should come with a free check over after 150 miles / 6 weeks and, in my experience, they need it, just to re-adjust the stuff that has bedded in over that time.

 

[Bristol Dave]

Thanks for all the replies.

@swee'pea99 - yes it is still under guarantee but a bit of a faff to sort as I bought it in Bath (a story for another time).

@summerdays - I'm in St.George, so not far from Horfield.

@tundragumski, O2GF74, Big John and Norm - thanks, I'll have another look and see if I can suss out what is happening. The bike was serviced at 6 weeks and I only ride a 30 minute commute (so 5 hours a week on the bike). I don't pile on the pressure and rarely rise from the seat, preferring to use the gears. There is no play in the bottom bracket. There was no problem last night or this morning and the ride feels the same as always.

It could be a jump between gears Norm. In fact this seems a better description of the problem now I think of it.

Thanks again.

BD