Bicycle expert help requested

[Piff]

Number 2 son has a Muddy Fox "meltdown se" which has 21 gears (3 front cog x 7 back cog) He has a paper round and as far as I can see the bike gets much abuse & little maintenance. The chain has always been rusty & the bike dirty, despite parental criticism.

Problem has developed where the chain is "slipping", resulting in a recent spill & damaged knee.

Looking at how the chain travels over the rear cogs, rather than settling into each tooth on the cog, it rises & then slips a tooth.

My conclusion is that the chain is stretched/worn and needs replacement (and better future maintenance)

This is where my knowledge lacks. When replacing a chain, do the cogs also need replacement?

Is there a recommended place to buy the necessary components?

 

[vijilants]

The cog shouldn't need replacing....if the chain is rusty, could it be that some links are sticking ? May be an idea to remove it, clean it and re-lubricate it and ensure that all the links move freely.

If you need a chain, you should be able to buy one from Halfords or any bike shop.

 

[Timster]

Hi.

In the bike world we call this "ramping" The cain has stretched so doesn't sit neatly on the teeth of the cogs, and the cogs are worn, giving that arched appearance you talk of. Chain and cog have stretched and changed together over the years, but now won't work together as too much ramp on the cogs.

Solution is to replace both the chain and the cogs. THe front cogs may well be OK, this is usually solved by changing the rear cassette (cogs) Shouldn't cost much, and easy to do yourself as long as you've got a chaine breaker tool, a chain whip and the correct tool for looseing the cassette. Ask in the bike shop where you get the new cassette, they'll probably loosen the old one and tighten the new one for nothing.

There's no other solution to this i'm afraid. If you just change the chain it'll still ramp off the worn cogs, and if you just change the cogs the old chain will be too streched for the teeth on the cogs, so will slip.

Good luck.

Tim

 

[greggster]

i'll second that opnion. its the same as my enduro (mx) motorbike every 10 hours!!!

 

[KillerHERTZ]

Ditto - mine is doing it at the mo aswell it 'clunks' and knocks your feet off the pedals, I go through 1 chain set (XT) per year on a 4 mile cycle to work & back (I cycle hard).
As everything wears down at the same rate, if you simply replace the chain it will be worse as everything wears at the same rate.

 

[Smatt]

Would be worth giving chain a good oil & loosening stiff links first to see if that stops the chain jumping. If that solves jumping, then it is an option to just stick with current chain/chainwheels/casstte- may get many more miles of 'adequate' use, although gear shifting will not be as smooth/responsive
If that doesn't work, then you have to replace everything as the above posts

 

[ROBB]

The chain jumping of the casette could be down to just poor indexing - do the gears change ok at the back??
if the indexing is ok - then chain and/or chainset & casette need changing but you will only know for sure if you have a chain wear indicator (£8 from halfords for mine) or if you put a new chain on. . . . .

Check out www.chainreactioncycles.com for best prices & free delivery on chainsets etc or have a word with local bike shop.

TO prevent recurrance - replace chain when aforrementoned chain wear indicator says chain stretch has reached 0.75% - then you will not accrue wear on the expensive bits of the drivetrain

Rob

 

[Piff]

The chain jumping of the casette could be down to just poor indexing - do the gears change ok at the back??
Rob

I think indexing is ok. I've turned the bike upside down and just turned the chain slowly & you can see it ride up on the teeth of the rear cog.

 

[RoseTattoo]

If you want the perfect job replace them and clean everything. Better to get a good bike shop to do it. You need a specific chain and cassette type.
OR
Clean everything, oil and adjust the drop-out depending on the type to stretch the chain a little more. This is the non-perfect but maybe practical solution.

 

[Piff]

If you want the perfect job replace them and clean everything. Better to get a good bike shop to do it. You need a specific chain and cassette type.
OR
Clean everything, oil and adjust the drop-out depending on the type to stretch the chain a little more. This is the non-perfect but maybe practical solution.

more info please on "adjust the drop out". He will struggle on paper round money to do the "perfect job"

 

[Stratman]

Adjusting the drop-out means moving the rear wheel backwards a bit to take up slack in the chain.

Loosen the nut(s) that hold on the rear wheel, pull the wheel backwards so that the chain has a little play in the vertical plane, about 1-2 cm at the mid-point of the run, and re-tighten the nuts, ensuring that the wheel points straight ahead. It's quicker to do than explain.

 

[Timster]

Looseing the drop out won't help.

THe chain is streched and the teeth are worn - they need replacing. Anything else is a waste of your time.

Tim

 

[Piff]

Adjusting the drop-out means moving the rear wheel backwards a bit to take up slack in the chain.

Loosen the nut(s) that hold on the rear wheel, pull the wheel backwards so that the chain has a little play in the vertical plane, about 1-2 cm at the mid-point of the run, and re-tighten the nuts, ensuring that the wheel points straight ahead. It's quicker to do than explain.

Thanks, but doesn't the arrangement under the rear cogs take up the slack in the chain? Or am I missing something?

 

[Smatt]

The rear derailleur will take up slack in the lower part of the chain. Moving the rear axle means that small distances(proportions of a chain link) can be adjusted, meaning the there will be less slack on the upper part of the chain.

This is a muddy fox 21 gear bike.
-By this description, it sounds like a fairly old bike (as even cheap bikes are generally 24 gears now & better ones 27 or 30 gears).
The perfect solution for this bike would be to replace everything with new.
However, this starts to get quite expensive; a cheap alternative might be to clean all up well, lubricate and adjust and the end result may be a usable(but not perfect) bike which is ok for thrashing around on.

Alternatively, a new bike could be considered....

 

[Piff]

The rear derailleur will take up slack in the lower part of the chain. Moving the rear axle means that small distances(proportions of a chain link) can be adjusted, meaning the there will be less slack on the upper part of the chain.

This is a muddy fox 21 gear bike.
-By this description, it sounds like a fairly old bike (as even cheap bikes are generally 24 gears now & better ones 27 or 30 gears).
The perfect solution for this bike would be to replace everything with new.
However, this starts to get quite expensive; a cheap alternative might be to clean all up well, lubricate and adjust and the end result may be a usable(but not perfect) bike which is ok for thrashing around on.

Alternatively, a new bike could be considered....

Thanks.
Number 2 son has a 17th birthday coming up and obviously wants to learn to drive. However, he's already had his birthday present from us in the form of next years school ski trip! Paper round money is tight at £14 per week and we are trying to get him so appreciate the value of money so don't particularly want to bail him out for a bike repair caused (at least partially) by lack of maintenance - chain has been allowed to rust & bike cleaning is an annual event at best.
So as he is saving for driving lessons, we might attempt the cheap option initially with a good clean & lubricate & move the back wheel back to tension the chain.
Will report back!

 

[Smatt]

Sorry, Correction: I think I was getting carried away with the moving the axle thing (thinking of our tandem?). This is useful on single speed bikes with no derailleur.

The rear axle movement will still be taken up by the rear derailleur, so is not necessary apart from to align the wheel in the frame.

(I stand by my other comments! )

 

[Piff]

Had a look today at the rear wheel hub to see if it could be moved but the slot in the frame is vertical rather than horizontal. So no way of adjusting real wheel to take up any slack in top part of chain.

Looked to me that front cog set is also pretty worn so repairs will be pricey.
I assume special tools are needed to remove chain, front cogs & rear cogs.

 

[Barney9304]

The only way to get the bike working correctly is to replace all the drive components, any amount of fettling will not make any difference.

The drivetrain starts to stretch and wear rapidly from the start, I change my chain and rear cogs every 3 months and the front chainset at least annually, but I ride off road at least 3 times a week the year round. No cheap way around it I am afraid.

 

[ROBB]

Piff,

Ive had a look for that bike on t'interweb and as far as i can tell it has a square taper bottom bracket & 7sp rear cassette (without seeing it i cannot be 100% sure. Bits required:

1 of many cheap chains available http://www.chainreactioncycles.com/Models.aspx?ModelID=25427

cheapest triple chainset i could find (for a square taper bottom bracket)
http://www.chainreactioncycles.com/Models.aspx?ModelID=31286

Ur bottom bracket is almost certainly a square taper one and i am assuming it does not need replacing - if it is NOT square taper this chainset will not fit - without seeing it i cannot tell for sure.

As for the rear cassette: assuming it is a cassette and not a screw on block - you should be able to pick one up for about £25

Chainset (front cogs) will require a chainset remover tool, there are lots of different ones and a good reason to use a shop for fitting. A chain tool will also be required as will a cassette remover tool/chain whip.

All in all u can probably get the bits for approx £50 but then u need about £30 of tools - then u have to know what ur doing to get it to work.

Might be best to have a word with a local shop; either way - good luck

rob

 

[verytalldave]

21 gears...........
Mollycoddled.
Buy him a similar bike to what I had when I did my paper round.
A single speed fixed wheel with a front brake and drop handlebars.