SRAM Red Rear Derailleur Tuning

Discuss light weight issues concerning road bikes & parts.
stevec1975
Posts: 250
Joined: Tue Nov 24, 2009 12:37 pm

by stevec1975

On the back of chris14's idea, I stripped the decals of my red mech and have it a good polish, I also painted it to match the 2016 mechanical stuff, sans the sram logo

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Weight with rothshek bottom pulley and sram top was 130.2g

by Weenie


chris14
Posts: 36
Joined: Fri Dec 23, 2011 12:50 am
Location: France

by chris14

Looks great. How did you polish it?

stevec1975
Posts: 250
Joined: Tue Nov 24, 2009 12:37 pm

by stevec1975

just a bit of dremel and autosol, comes up to a mirror finish

chris14
Posts: 36
Joined: Fri Dec 23, 2011 12:50 am
Location: France

by chris14

Just tried .... perfect thanks


chris14
Posts: 36
Joined: Fri Dec 23, 2011 12:50 am
Location: France

by chris14

Not yet, I have got side-tracked on another DIY project on the Red brake levers. Not sure where to post though. May be this thread should be called just Sram Red tuning. Or should I post it on 'Show me your tuning'?

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prendrefeu
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Joined: Wed Oct 31, 2007 10:32 pm
Location: Los Feliz, Los Angeles, California
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by prendrefeu

Here's another contribution.

Image

The bolts are aluminum because I haven't had good fortune in using nylon bolts: they always seem to be too weak and bend or break fairly quickly. I also tried polycarbonate bolts for the limit screws, those broke on just a simple hand test. My only real concern is the rear-side of the arm: it's an ulta-light variety and the standard SRAM arm is only 3g more mass. On another derailleur/build I once had one of those thin rear-arms on the cage fail during a ride which lead to the chain jamming up and a entire world of pain as I crashed badly to the front.... so... slight concern, I may take the 3g penalty for the sake of my nerves. I left the lip on the arm because it's convenient to move the arm around when putting a wheel on or taking a wheel off.
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Jenmoss
Posts: 97
Joined: Wed Oct 25, 2017 10:15 am

by Jenmoss

prendrefeu wrote:
Wed Jan 10, 2018 9:20 am
Here's another contribution.

Image

The bolts are aluminum because I haven't had good fortune in using nylon bolts: they always seem to be too weak and bend or break fairly quickly. I also tried polycarbonate bolts for the limit screws, those broke on just a simple hand test. My only real concern is the rear-side of the arm: it's an ulta-light variety and the standard SRAM arm is only 3g more mass. On another derailleur/build I once had one of those thin rear-arms on the cage fail during a ride which lead to the chain jamming up and a entire world of pain as I crashed badly to the front.... so... slight concern, I may take the 3g penalty for the sake of my nerves. I left the lip on the arm because it's convenient to move the arm around when putting a wheel on or taking a wheel off.

Nice job. B limit screw at the rear ,I have come to realise that any sort of plastic /nylon etc ends up bending/twisting so I opted for a very light titanium screw.

I mean 3grams you could lose cleaning your teeth :lol: it’s just better to have the worry go away.
Good point about the lip , I never thought of that I always cut them off.
Looks propppppaaahhhhhh :thumbup:

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4ibanez
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by 4ibanez

Great stuff! How long is the screw you use for the adjuster? 10/12mm? Is the amount of adjustement about the same as standard? Looks like the plastic held up to drilling fine - any tips or was it super easy? Did you re-shape the slot at all to get a good fit for the housing?

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prendrefeu
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by prendrefeu

The adjustment bolt: it's a M8 Polycarbonate bolt with a 2mm hole going through it, really easy to do just go slow. I re-tapped the original adjustment hole to M8 to make this possible. The fit is nice and tight, no spring needed. The housing fits into the head of the bolt perfectly, no drilling or re-shaping necessary.

I could cut down the length of the bolt by a small amount, I don't need *that* much adjustment, but I do want it to be strong within the reduced arm of aluminum.
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4ibanez
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by 4ibanez

Shame there's not more love for this. I'd love to know where you removed material from the derailleur. There seems to be a dearth of information on where's best to dremel it.

I can see you've ground away the obvious stuff at the top and some from the little arm that houses the adjuster....where else? Anything else planned?

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prendrefeu
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by prendrefeu

Yes, times have changed - many people are now afraid of modifying their equipment for what is often a questionable warranty - and the increased popularity of the sport/recreation has made many come in with more $$$ in mind than interested in knowing how their equipment actually works. Plus the whole 'aero' thing has made people forget that mass still matters. It's "aero + light" not "aero replaces light" which a lot of people think is the case.

Anyway, my 'day job' has been rather busy lately and I'm headed on a short holiday for a few days. I plan on doing some more tuning of this derailleur soon and will post some more detailed images of where things were removed (and reasoning why some areas weren't reduced). Sorry for the delay.
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prendrefeu
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by prendrefeu

Ok, I spent a little more time on the derailleur removing some more of the body material. I also edited the adjustment bolts: removed the heads, cut into the shaft to make an in-line flat-head screw. All of this was partially negated because I replaced the rear-arm of the cage to the original from SRAM. As I mentioned before I've had bad luck with the ultra-light variety of those rear cage arms, so I'm going with the standard. Then again who knows if the rest of the body will fail now? :lol: So with a weight penalty of 3g from the prior post, I managed to reduce at around another 1g from further editing. I really don't feel like I want to go any further with this one. If I do tuning on another rear derailleur again I'll go a bit more extreme (and perhaps a bit more thorough... why not just model the parts individually on my own, 3D print them, and build it from scratch to match the same mechanical attributes of an original?)

Image

Notes on the detailed images (as requested) - I drilled out the center of two of the 4 pins. This was a result of frustration because I tried every method to get them out (including the 'make a screwdriver into a circular-holed lever trick), so I ended up drilling out the centers in the process of trying to extract them... then stopped because, well, I got a little nervous about it.

Let's see how this holds up. :lol:

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Jenmoss
Posts: 97
Joined: Wed Oct 25, 2017 10:15 am

by Jenmoss

Prendy , I use the “ standard “ rear cage from Fibre Lyte not the ultra light one. I still have the first one I used on one of my mechs . It held up fine even survived a broken mech . The ultra light one weighs 2grams the normal one weighs 5 grams . Same cost.

Mech looks great.

by Weenie


TARE
Posts: 25
Joined: Thu Jan 29, 2015 10:27 am
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by TARE

Image

Not RD... but i think you would like to see this. Red22 brake levers.
Made from m40j carbon. 20 hours of work and 21.2g for the pair at the end of the day.

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