Plastic derailleurs

[thelawnet]

Apparently this is a thing. Spend more money, get plastic derailleurs.

Currently:

XTR M9100, M9000, M986 carbon fibre plate body & outer plate
XT M8000, M7000 11sp (not 10sp, which is older kit), M6000 (GS, not SGS) 10sp fiberglass plate body
The XT T8000 is free of plastics, but the Deore T6000 has a fibreglass plate body again.

Fiberglass is also used on Altus & Acera, and there's a bit of carbon fiber (outer link) on Alivio M4000, so hardly a premium material, just cheap.

Dura-Ace R9100/R9000 are similar to XTR but also use carbon fibre for the inner plate.

Presumably XTR is spared this because plastic isn't really an ideal derailleur material.

Ultegra R8000 has fiberglass, but 6800 had carbon fibre. 105 R7000 also uses fiberglass, though the previous generations did not.

Sora, Claris & Tourney also use bits of plastic, but they call it 'resin'.

On SRAM mountain bike groupset everything's steel, aluminium or titanium, except for the 'I want to set my fire to money' XX level, where there's either a carbon cage or carbon/alu.

SRAM also uses fiberglass on their cheapo stuff, but NX, GX and X0 are free of both fiberglass & carbon fibre.

On the road side you get carbon for the Red & most Force derailleurs, but it's missing from Force 1x (presumably because damage is more likely on gravel bikes?)

Rival & Apex are both plastic-free.

Campagnolo use lots of carbon fibre except possibly on Centaur.

The weight saving from 105 5800 to R7000 thanks to the switch from steel inner link & aluminium plate body to fiberglass is 250g to 232g (mid-cage) and 235g to 225g (short-cage).

Presumably when the magazine drones do their reviews they have to show many grams lighter new groupset is vs. old, so this use of plastics makes things look like an upgrade, even if there are no benefits to the consumer. Presumably 'no reason to upgrade, your old bike is perfectly fine' would not go down too well with the advertisers.

[thirdcrank]

There's nothing new in the world. From 1962:-

http://www.disraeligears.co.uk/Site/Sim ... r_532.html

[amediasatex]

You seem to be lumping plastic, fibreglass and carbon fibre composites all in the same bucket.

They're not the same material, even within their individual categories there's variation between materials and their specification and properties so it's disingenuous to equate them in such a way.

[zenitb]

...wow even the Deore stuff is getting plasticised! !! Thanks for sharing this thelawnet....I didn't notice the changes in Shimano's blurb of course Time will tell regarding the longevity of this stuff I guess...is the change just for cheapness I wonder ????

[Brucey]

SRAM X4 mechs have been plastic in places for years. If you stuff one in the spokes of the rear wheel (not difficult to do, because the limit screws need adjusting on weekly basis... ) then it isn't unusual for the steel bits to bend but the plastic parts to survive.
Plastics vary of course and perhaps one shouldn't lump them all in together but they do share one feature; anything that is injection moulded has a rather low modulus of elasticity by comparison with metals. About x10 (or more) lower in fact.

Stuff that is not injection moulded but is reinforced with a high volume fraction of long fibres -which most folk would call 'Carbon Fibre'- has a higher modulus in directions that are reinforced, and a rather less good one in directions that are not.

Anyway the low stiffness of these materials means that their use in (say) derailleur top knuckles is limited, but plenty of manufacturers think it is OK to use plastic in a lower knuckle.

cheers

[thelawnet]

I think the Deore, SLX & XT derailleurs are basically identical. You just get different jockey wheels, and some times they use lighter materials on the plates. E.g., SLX M675 is identical to Deore M615 except for the inner plate (alu vs steel).

On the current models, the Deore M6000-SGS is identical to the SLX M7000-10sp-SGS, except for a stainless cable bolt vs steel. This bolt costs another £10 effectively.

The M6000-GS uses the same cage as the M7000-11sp-SGS, but obviously 10sp vs 11sp in the derailleur itself.

Hence the similar materials.

[Brucey]

IIRC there are different pulleys and different materials and surface treatments on the bushings.

cheers

[fastpedaller]

In the 80's Ofmega made an all (well pretty much all) plastic (resin?) derailleur called the mistral. I had one (but never the courage to use it?) and sold it a couple of years ago.
http://www.disraeligears.co.uk/Site/Ofm ... lleur.html

I wonder if anyone here has used one, and their experience of it?

[foxyrider]

Well i'm quite happy with my 'plastic' bike with its 'plastic' rear mech, 'plastic cranks, pedals, saddle, handlebars etc. At least I don't have to worry about corroded backplates, corrosion worms and all those extra grams!

In fact i've gone as far as replacing dodgy metal bits on rear mechs with 'plastic', even on my touring bikes (one of which even has 'plastic' cranks fitted.

OTOH, I wouldn't fit more than an actual plastic bottle cage on any of my bikes - been there with bendy brake levers, twisty saddle bodies and so on.

[satanas]

Back in the 1980s we sold a depressingly large number of bikes with Ofmega Mistral RDs, and so I had to adjust lots of them. They shifted badly, about what one would expect from what was effectively a Campg NR clone made from either pink or black cheese. If you really had to have a pink RD then they were great, otherwise not so much. I cannot remember now whether they all broke or not, but my experiences with Ofmega parts were almost entirely negative (probably why I've forgotten); their later "indexing" derailleurs and shifters were a PITA too. We sold Suntour before, and it was infinitely superior...

Equating CFRP with injection moulded parts is fairly ludicrous; the difference in stiffness is massive, and it's likely the difference in strength is too, in most cases. Personally, I like forged alu derailleurs, but Shimano seem to be fairly sensible about not making things that snap too often, unlike some of SRAM's earlier carbon cage plates. (I saw a guy snap two XX$pensive SRAM RDs in two days during a MTB stage race once.)

Later,
Stephen

[hondated]

IIRC there are different pulleys and different materials and surface treatments on the bushings.

cheers

As a matter of interest do you periodically re grease those bushings as I do and wonder whether its worth the effort.

[Brucey]

IIRC there are different pulleys and different materials and surface treatments on the bushings.

cheers

As a matter of interest do you periodically re grease those bushings as I do and wonder whether its worth the effort.

yes and yes.

cheers

[hondated]

Thanks Brucey glad to know I haven't been wasting my time Ted

[rjb]

IIRC there are different pulleys and different materials and surface treatments on the bushings.

cheers

As a matter of interest do you periodically re grease those bushings as I do and wonder whether its worth the effort.

yes and yes.

cheers

What would you recommend milage wise to do this and would you recommend a semifluid grease or something thicker?

[hondated]

As a matter of interest do you periodically re grease those bushings as I do and wonder whether its worth the effort.

yes and yes.

cheers

What would you recommend milage wise to do this and would you recommend a semifluid grease or something thicker?

Dont know what Brucey would recommend rjb but I tend to re -grease them when I remove the chain to clean it which is roughly 4 - 6 weeks no matter how many miles I have ridden.