Chain jump on new 7 speed freewheel (Shimano IG chain dimensions?)

[stevesey]

Hi all
Just fitted a new Shimano HG 7 speed freewheel to my Raleigh Record Sprint (Ultra 6 before) - all is good - except for some jumping on the small 13T cog - the extra width means the chainline leaves little space between the 15T and the chain as it comes off at the 12 o'clock position. Initially though the shift ramps or pickup teeth might be fouling. On closer inspection I realise the old Raleigh chain is taller and the chain is resting on the spacer (so not full engaging in the teeth). See the greasy marks on the spacer below (top right) and if you look at the chain you can see how tall the inner links are.

Measured the chain height and it's 9.5mm - check my daughters old £60 halfords special MTB and that's more like 8.5.

This looks to be the problem - anyone disagree with the diagnosis. I was thinking of a new chain anyway so was going to put an IG51 on - anyone know what the height is on that? (Can't find via on google - only the width).

Cheers

Steve

 

[stevesey]

Of course there shouldn't be any issues with a Shimano IG chain on an Shimano HG freewheel. Just keen to be sure this is the issue - magnified a couple of photos online and based on the pitch being 1/2in the IG height looks like somewhere in the 8-8.5mm (so does look like the current chain is too tall, hence the occasional slip when on the smallest cog).

 

[Rickshaw Phil]

Personally I'd always replace the chain too when fitting a new freewheel or cassette. Chains lengthen with wear so it's quite likely the jump is because the chain is not meshing properly with the new freewheel.

KMC or SRAM chains are good quality and come with quick links that make fitting the new chain easier.

 

[DWiggy]

Sounds like you also needed a new chain

 

[stevesey]

Personally I'd always replace the chain too when fitting a new freewheel or cassette. Chains lengthen with wear so it's quite likely the jump is because the chain is not meshing properly with the new freewheel.

I did measure the chain and it seems spot on length wise (should have said) - it has only jumped on the 13T (but then you'd expect that to be the worst - but I did load the 15T up, probably more so than the 13T, a few times with no issues).

Think it's the height of those links having a similar effect - and not letting the rollers drop right into the teeth.

 

[Rickshaw Phil]

I did measure the chain and it seems spot on length wise (should have said) - it has only jumped on the 13T (but then you'd expect that to be the worst - but I did load the 15T up, probably more so than the 13T, a few times with no issues).

Think it's the height of those links having a similar effect - and not letting the rollers drop right into the teeth.

Ah, right. Didn't realise you'd measured it. It still sounds like there is an incompatibility there, so you'll need a new chain either way. Any 7/8 speed will do the job but I can recommend the brands I mentioned above. They can be obtained cheaply too. Have a look here.

 

[Cycleops]

Always a good idea to change the chain when installing a new freewheel.

 

[stevesey]

IG51 with KMC missing link connector on the way (£6.25 inc p&p from pedal bits ebay shop). Will save me cleaning the old one properly :-)

 

[stevesey]

That's sorted it - chain now sits right down on the bottom cog (not resting on the spacer) and no jumps.