worn chainring?

mister g

Member
Hi all,
As a relatively new cyclist was hoping you will be able to point me in the right direction! I've had a rigid mtb for a couple of years which has served me fine for the occasional journey on promenade rides. I've acquired a hardtail (?) as I'd like to do a bit more adventurous riding but this bike needs a couple of things doing to it. I don't want to spend a lot on getting it going so please be gentle with me :smile:
First off, I know it needs the bottom bracket sorting out. Currently it has the ball bearings enclosed in cage rings but one of the cages has corroded. Am I ok to replace this with a sealed cartridge type by (68mm housing, 122mm axle)?
And then I'm going to replace the chain to but my main reason for posting is advice on the chainring. I can't pedal the bike on the middle ring as the chain slips. It seems to be fine on the inner and outer rings so I assume that the rear cassette is ok and the problem lies either with the chain or chainring (or both). I've removed the crankset and see that there seems to be grooves inbetween some of the teeth which don't appear to be the same as the rest but, at the same time, there are four of these grooves spaced at approx 90 degrees and are where there is a lump on the face of the chainring.
In your opinions would you say this is worn or a feature of the middle ring? (I'll add a couple of pics in the morning as I'm typing this on my phone at moment and it won't let me reduce the image sizes)
Thanks in advance
 

Flick of the Elbow

Expecting vaccination in August at best
Location
Lothian
If the transmission is worn that badly yes you probably will need a new chain and middle ring and in all probability a new cassette too.
Can't comment on the bb.
But I'd also suggest forging a relationship with a good local bike shop, they will be able to advise on these sorts of things.
 

raleighnut

Legendary Member
Location
On 3 Wheels
the middle ring has had it and it looks like it cannot be changed so new crank needed, this may or may not come with the bearings/shaft or you could take this as a chance to uprate.
 
OP
M

mister g

Member
OK thanks, yes it's gonna have to be a crankset as they're all rivetted together. Now for my next question: The current rings are 42/34/24 teeth, should I be looking at a like for like replacement? I've seen some slight variances in numbers of teeth but not sure if this would have any detrimental effect. And should I also keep the crank arms at 170mm as per the crankset currently on? I've seen some cranksets on "that there auction site" which would get me going for around £20-£30. I know this may not be best quality stuff but currently I don't want to (and can't) put a lot of money into it as it's only occasional use.
 

gbb

Legendary Member
Location
Peterborough
Definitely fubar'd.
As to keeping to the same ring sizes, yes you probably should. I tried changing a crankset on my sons knockabout from 42 to 48 on the large ring (got a cheap deal on one at a car boot) and then found the extra diameter fouled on the chain stays.
That may well not apply to yours, equally it might.
 

shadow master

Well-Known Member
Any chain that's been running on that middle ring will be totally knackered, i see can most of the riding has been done on the middle ring only hence the wear!bike needs bb,chain set,chain and almost certainly rear sprocket,relatively expensive for a very basic bike.wouldn't mess with ratios at front,probably lead to shifting problems.
 

shadow master

Well-Known Member
Being an 8 speed cassette you have to change the chain and cassette together as they wear as a pair,in short about £50+ for bb chain set cassette and chain
 
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