Why does my chain slip? I know, big question but please read

The History Man

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Ok have new chain, cassette not worn, cables oiled, gears adjusted and all change fine but a little sticky on rear down change but only v occasionally.

When riding across a road undulation that causes rear suspension to compress slightly I loose pedal pressure for less than half a pedal rotation. Chain etc makes no noise, doesn't jump or change sprocket. Pedal just seems to lose pressure.

Can't think of anything else to try other than new gear cable but would this make any difference? Is mech spring a factor as also checked and seems fine.

Any suggestions ? :facepalm:

Bike as below
 
Re: Why does my chain slip? I know, big question but please

As gear cable routed under BB would it pull on swing arm upward movement? Find this hard to believe as surely would be a design issue sorted long ago.
 
Re: Why does my chain slip? I know, big question but please

freewheel problem perhaps? If the chain were skipping, you'd hear it.
 
Re: Why does my chain slip? I know, big question but please

Poor design of rear suspension. Under compression it moves the cassette closer to the chainrings thus making the chain momentarily loose.
 
Re: Why does my chain slip? I know, big question but please

Rampage":t9z97qwn said:
Poor design of rear suspension. Under compression it moves the cassette closer to the chainrings thus making the chain momentarily loose.

So have just got to live with it? Your suggestion seems to make sense but surely this wouldn't happen on an £1800 (1997) push bike?
 

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Re: Why does my chain slip? I know, big question but please

I have to admit when I read your post I thought it would be a late 80's / very early 90's bike. I was surprised to see it was made much later!

Let's hope it's something else!
All the pivots etc are origional I take it? Nothing bent? Shock bushes / bearings ok?
 
Re: Why does my chain slip? I know, big question but please

All seems to move ok under compression. Should I strip the pivots and grease everything? Doubt if its ever been done.
 
Re: Why does my chain slip? I know, big question but please

Can you remove the shock and see if it still moves smoothly without the wheel in?
Also, can you lockout the shock and ride it and see if it stil happens?
It doesn't have oval chainrings?!
 
Re: Why does my chain slip? I know, big question but please

Rampage":s1midb78 said:
Can you remove the shock and see if it still moves smoothly without the wheel in?
Also, can you lockout the shock and ride it and see if it stil happens?

No lockout - fox alps 5R

Not sure what mean for first question? Please explain further.
 
Re: Why does my chain slip? I know, big question but please

Remove the shock to make sure the linkages are smooth. With the shock installed you can't tell. Also to see if the chain slackens when it's fully compressed.
 
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