Is it my front mech?

[smokeysmoo]

Long story short time

6 speed Raleigh cold set and re-built with modern 10 speed wheels and an 8 speed cassette.

Original front mech retained and works fine but can't seem to provide a chainline in all gears.

I know all about cross chaining so that's not my quesiotn, I just don't like the front mech catching in any gears when I set them up.

You can see on the picture below that the chain line is not right when the chain is on the lower end of the cassette, but other than that it rides perfectly.

So would an 8,9 or 10 speed front mech make a difference?

I'm guessing it would as it must have a longer throw than the original Sachs Huret one from the 6 speed set up.

Anyone?

 

[Nigelnaturist]

If its at its limit, then a new FD I am guessing is the way to go. Its what I will be doing when i get round to the Carleton.

 

[Drago]

You need a 7 or 8 speed specific front mech. The cage isn't wide enough on a 10 speed to use.on an 8 speed set up and will run in some gears no matter what you do.

 

[smokeysmoo]

If its at its limit, then a new FD I am guessing is the way to go. Its what I will be doing when i get round to the Carleton.

You need a 7 or 8 speed specific front mech. The cage isn't wide enough on a 10 speed to use.on an 8 speed set up and will run in some gears no matter what you do.

Cheers fellas. I figured as much but thought there's no harm sanity checking myself

 

[sittingbull]

Have you replaced the BB with a shorter one? Or one of the same length but narrower taper?

It may be some sort of optical distortion but the amount of displacement looks more than the chain resting against the cage.

 

[smokeysmoo]

Have you replaced the BB with a shorter one? Or one of the same length but narrower taper?

New UN55 fitted, same length to about a mm. I've never considered the taper but it all seems fine and the front mech just can't shift over anymore, it must be the mech.

 

[sittingbull]

It may be the mech, although if it worked OK with the original BB I would have thought it should now.

The mech may be slightly out of alignment but it's difficult to say from that angle.

Still looks like it could be a chainline issue. Cold-setting will add 2mm each side with minimal difference to the chain position at the front which the front mech should accommodate.

 

[Big_Dave]

Are you on modern brake/shifters? if so the sachs derailleur won't work as the throw is wrong, mine worked ok with the downtube shifters but not with modern brake/shifters.
my Raleigh is on 8 speed cassette, I run a 9 speed chain and 9 speed front mech shimano tiagra although 8 speed chain was ok the 9 speed is 0.25mm narrower so a little more clearance.

 

[smokeysmoo]

Are you on modern brake/shifters?

Nope, original Raleigh Record Sprint brake levers and downtube shifters

 

[Big_Dave]

that is strange, my sachs mech ran a triple as well when I swapped from the double (on the downtube shifters),

 

[sittingbull]

Still pondering this 'cos I'm potentially going to come up against the same issue. I've got a Holdsworth from around '89 with a 105 groupset. The frame is way too big and I'd like to use the groupset on another frame.

I've been pondering on BB length as I'd like to switch from cup and cone to cartridge. This listing for the same 105 crankset advises on increasing the BB length from 113mm to 115mm when changing to a cartridge but dosn't explain why. I can only assume it's due to the "taper".

Years ago I had another cup and cone 113mm BB replaced with a cartridge (I can't remember the length) on a double from the same era and that threw my chainline out.

Hopefully it's just your mech. Please update with your solution @smokeysmoo

 

[smokeysmoo]

Hopefully it's just your mech. Please update with your solution @smokeysmoo

Will do

 

[Big_Dave]

I had a play today on my raleigh with the sachs mech & dts to see if I could replicate your problem, I used a 113mm BB with the 8speed, I tried the 115mm BB and there wasn't enough movement on the mech, when I changed to a 9 speed mech I fitted a 118mm BB for it to work and gave it a lot better chain line. My sachs is a band on type or you could have borrowed it.

Edit, Have you torqued the crank bolts (40Nm)

 

[raleighnut]

That chain line does look a bit extreme in the photos, is it as bad in reality or more of a lens exaggeration (wide angle lens) other than that can you get the front mech to throw a bit further out ( I have to manually trim my similar set up in sometimes when using the 2nd largest rear cog to get up a short climb)