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Chain slips under foot pressure.
#1
Hi, All

I am having issues with one of my bikes (Malvern star Rock trails) this bike is a hard tail Mountain bike I got it a few months back and just started to fix it up. It is a perused bike and I have clean it , lined up the front and rear derailleur, checked for stiff links and worn teeth but all seems fine also have checked for chain stretch and all seem good. The one conclusion I have came up with it the chain is to long by 3 or 4 links but my bike store said that it’s might not be the problem. So if you can help me in any way it would be very helpful.
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#2
Chain slip when you pedal hard is usually a result of wear on the drivetrain; often happens when you fit a new chain with the old worn cassette.

Does it happen in all the gears, or just one or two in particular?
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#3
(07-18-2010, 09:17 AM)xerxes Wrote:  Chain slip when you pedal hard is usually a result of wear on the drivetrain; often happens when you fit a new chain with the old worn cassette.

Does it happen in all the gears, or just one or two in particular?
Just one or two gears.
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#4
Look carefully at the cassette, you will probably see that the sprockets you're having trouble with are worn more than the others. You find that the smaller sprockets wear fastest as the load is concentrated on fewer teeth, especially if they also happen to be your favoured gear.

How did you measure the chain wear, with a ruler or a special tool? I find it quite difficult to get an accurate result with a ruler; much easier with one of these:

[Image: 315XG5R9-dL._SL500_AA300_.jpg]

In any case, it's more likely to be a worn chain and cassette than the chain being too long. Chainrings also need replacing if they get badly worn, but they generally last much longer than the rear cassette.

Chains can wear surprisingly quickly in wet, muddy or gritty off road conditions and once the chain is worn, the cassette wears quickly as well. The last chain on my mountain was worn out in less than 1000 miles and because I didn't notice until it was too late, the cassette was ruined too.
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#5
(07-18-2010, 02:04 PM)xerxes Wrote:  Look carefully at the cassette, you will probably see that the sprockets you're having trouble with are worn more than the others. You find that the smaller sprockets wear fastest as the load is concentrated on fewer teeth, especially if they also happen to be your favoured gear.

How did you measure the chain wear, with a ruler or a special tool? I find it quite difficult to get an accurate result with a ruler; much easier with one of these:

[Image: 315XG5R9-dL._SL500_AA300_.jpg]

In any case, it's more likely to be a worn chain and cassette than the chain being too long. Chainrings also need replacing if they get badly worn, but they generally last much longer than the rear cassette.

Chains can wear surprisingly quickly in wet, muddy or gritty off road conditions and once the chain is worn, the cassette wears quickly as well. The last chain on my mountain was worn out in less than 1000 miles and because I didn't notice until it was too late, the cassette was ruined too.

I think your right and I did use a ruler for measuring.
Also i found there's a few teeth missing on the front chaingrings but I don't know if that does anything.

Thanks for the help and any further help you give me.
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#6
Missing teeth isn't a good sign and you should probably replace the chainrings. Sounds like the whole drivetrain may have seen better days.
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#7
(07-18-2010, 10:40 PM)xerxes Wrote:  Missing teeth isn't a good sign and you should probably replace the chainrings. Sounds like the whole drivetrain may have seen better days.

Thanks for the information i will look into replacing the whole drivetrain. thanks.
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#8
What chainset do you currently have? With some of the lower cost models, Shimano Alivio and even Deore, you might find that a whole new chainset is less than the price of a couple of new chain rings. It's a bit daft, but do check it out before you go ahead and buy new rings.
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#9
(07-19-2010, 12:55 AM)xerxes Wrote:  What chainset do you currently have? With some of the lower cost models, Shimano Alivio and even Deore, you might find that a whole new chainset is less than the price of a couple of new chain rings. It's a bit daft, but do check it out before you go ahead and buy new rings.

This is my other post that you replied to it has pictures of the bike.

http://forums.bicycletutor.com/thread-1830-post-9150.html
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#10
Ah, OK, I didn't spot that it was the same auther.

In any case, it's not an expensive chainset and it's probably cheaper to replace it whole than to buy separate chainrings.

Just looking at some prices on the net:
Chainset: Shimano Alivio Chainset Square Taper M410: £27.00
7, 8 or 9 speed cassette: £15.00 to £18.00, not sure what you have.
Chain, around £15.00

So, you could replace the whole drivetrain for around £60.00. Of course, unless you already have the necessary tools, or can borrow them, you will need to buy those as well.

Regarding your other post, I'm not sure what make or model the bike is. I don't think it would have been particularly expensive to start with and only you can decide whether it's worth fixing up. Is everything else OK, or do you suspect that other things will need replacing soon, once you sorted the drivetrain?
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#11
(07-19-2010, 03:23 PM)xerxes Wrote:  Ah, OK, I didn't spot that it was the same auther.

In any case, it's not an expensive chainset and it's probably cheaper to replace it whole than to buy separate chainrings.

Just looking at some prices on the net:
Chainset: Shimano Alivio Chainset Square Taper M410: £27.00
7, 8 or 9 speed cassette: £15.00 to £18.00, not sure what you have.
Chain, around £15.00

So, you could replace the whole drivetrain for around £60.00. Of course, unless you already have the necessary tools, or can borrow them, you will need to buy those as well.

Regarding your other post, I'm not sure what make or model the bike is. I don't think it would have been particularly expensive to start with and only you can decide whether it's worth fixing up. Is everything else OK, or do you suspect that other things will need replacing soon, once you sorted the drivetrain?

Yep everthing else is running fine. thanks for your help
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