105 RD-5501 to replace Lx M550?

[cmjc]

Hopefully this is not heretical; but...

I'm considering replacing a worn out Lx M550 rear derailleur (It is 24 years old after all) with a 105 RD-5501 long cage.

I understand the 105 works with 7 and 8 speed systems, mine is a 7 speed, 3 ring Panasonic MTB.

But is an 7-8 speed chain too fat for the 105's cage?

I rarely ride off-road, but often have to cope with earth and rubble covered road surfaces.

Is this idea a non-starter?

 

[jimbo-xc]

Re:

You might find the 7/8 speed chain rubs on the mech. It happened to me recently trying to use a 7/8 sp chain (in an 8 sp trans.) with a short cage 5501 mech. Fitted a 9 sp chain & all was well.

 

[cmjc]

So I'll forget that idea. (I recently bought 2 years worth of KMC Z7's.

Ta for the feedback.

I'll keep looking for a decent Lx M550 rear derailleur.

 

[cmjc]

Like a dog with a bone... the thought occurred to me..

I wonder if placing small washers as shims, on each side of the pulley wheels, would then allow an 8 speed chain to be used without rubbing on the cage?

I really don't want to go 9 speed chain.

 

[mattr]

You'd need longer bolts.

Nick the ones from the outgoing lx mech.

 

[cmjc]

Splendid, should work if I pack the cage a tad wider, and as you suggest, use the pulley axles from my old derailleur, or rummage in the LBS drawer for better ones.

Anything else to consider?