Chain freewheels between chainrings

[edat]

This is an old Fugi S-12 I refurbed and converted to indexed shifting.
It has a Shimano Sora crank, 8-speed chainrings, 52 and 42 tooth, a 10-speed chain and rear derailleur.

When I try to shift the front, the chain rides between the chainrings and slips, freewheels. I think the chainrings are too far apart.

Do I have to buy 10-speed chainrings?

Will they be closer together if I do or is it the old Sora spider that's causing the problem?
thnx!

 

[boydj]

I think you need to adjust your limit screws to let the chain move far enough to get onto the big ring. How many cogs do you have at the rear and do your shifters match? Front shifters are relatively insensitive to the numbers of gears at the rear, so should be capable of working if properly adjusted, even if the speeds of front and rear are different.

 

[raleighnut]

This is an old Fugi S-12 I refurbed and converted to indexed shifting.
It has a Shimano Sora crank, 8-speed chainrings, 52 and 42 tooth, a 10-speed chain and rear derailleur.

When I try to shift the front, the chain rides between the chainrings and slips, freewheels. I think the chainrings are too far apart.

Do I have to buy 10-speed chainrings?

Will they be closer together if I do or is it the old Sora spider that's causing the problem?
thnx!

You need an 8 speed chain.

 

[Tim Hall]

Adjusting limit screws will have little effect I think, as the chain gets into the inter-ring gap. I get this too sometimes, running a 9 speed triple with a 10 speed cassette and therefore 10 speed chain.

@edat I guess you have a 10 speed cassette on there.

 

[si_c]

Spacing doe 8/9/10/11 (excepting the new dura-ace and ultegra) speed shimano chainrings is the same - on road bikes anyway. New chainrings won't change anything, you need to adjust the gears correctly.

 

[mcshroom]

It can be down to the chainring dish. I had it on a brand new Spa double when I used a Stronglight inner and a Spa Cycles outer. The outer is slightly dished away from the spider whereas the SL is pretty much dishless, meaning that there's a marginally wider gap between the two than normal. That gap was just enough for the chain to fall in between the two rings when shifting down in some combinations, even when I'd backed off the limit screws enough for the chain to fall off the inner ring in normal riding.

I solved that problem by switching the inner ring for a tiagra one which is less shiny, but is slightly dished.