[Tippster]

Thought I'd share with you the weights from having stripped down my new Dura Ace 7800 rear mech.

Pivot bolt (DA) 10.38g
Pivot bolt (SRP - Al) 5.94g

Pullet wheel bolt x 2 (DA) 3.99g
Pullet wheel bolt x 2 (SRP - Al) 1.34g

Cable bolt (DA) 2.37g
Cable bolt (SRP - Ti) 1.50g


Total savings of SRP bolt kit for a DA 10 speed DR-7800 2004 rear mech 7.96g. For the obsessives, you could switch the Ti cable bolt for an Aluminium one and save a further 0.7g.

For the record before tuning 181.66g. Without barrell adjuster 177.42g.

I'm running my DA 7800 mech on a mtb with XT shifters. The shifters have barrell adjusters, so the adjuster on the mech gets dropped.

Next stage is to replace the mech plate with Carbon Fibre. Expected saving 3g. Expected final weight 165g.

 

[nino]

173g here...

i put the SRP kit of my 9s 7700 DA and it fits perfect.i further replaced the cable holder bolt with a Al bolt and weight is 173g now. with some tuned pulleys 164g are doable as you can see on the picture below...carbon fiber plates won't save any weight. i got the info direct from the guys who do them.DA plates are already light. but carbon would look sharp

 

[Tippster]

How many pulley wheels did you experiment on before you got to the bottom picture?

Loads more hole than wheel.

What size drill bit did you use?

Does it make it more difficult to clean?

Do you use the mech, off-road?

 

[Tippster]

Nino,


Have you checked out the adjuster screws on the 10 speed DA mech?

Are they steel or Al?

The CF mech plate I added to a 2003 XTR rear mech saved 4.6g. 50% more material in an XTr mech plate (roughly).

 

[nino]

9g Pulleys

I'm using my derailleur oofroad since 1/2 a year but with the regular pulleys.

adjuster bolts are Al if i'm not totally wrong. the pulleys aren't the ones from the DA! on DA pulleys you can't save more than 3 or 4g. the ones i pictured there are some cheapo DEORE ones , all plastic without bearings.they also weighd 18g but after some serious tuning i got them down to just 9g.11g would be durable enough for offroad too:

extended tuning here...for road use no problem.the upper pulley has to be a bit stronger to withstand some sideloads, the lower is no problem.

and here's a picture of a untouched and tuned pulley.note that i also made a hollow Al-axle to save weight.

 

[Tippster]

Nino,


I've seen pulley wheels with single holes drilled in but not ones with 2 to 3 holes drilled and then joined together.

 

[nino]

pushing the envelope...

it's time you start experimenting on your own then
these pulleys are out of a very hard plastic and are still plenty stiff. the pulleys on my 3 year old 9s DA derailleur show hardly any wear so wear shouldn't be a problem and if ever replacement is cheap. i didn't drill some holes for the looks, it's about saving weight...

same story on my SID where i shaved the disc adapters first before starting to shave all colour, replace the internals and recoat it to get a fork weight of just 1068g

 

[Tippster]

I'm all for experimenting . . .

It's just that I expect to do approx 8k miles a year road and 1k a year off-road XC.

Just concerned over possible durability issues.

I justify my bike bits spend on the fact I save approx £300 a month by not running a car. Home to work every day by bike. For around a year now I've been spending approx £200 a month on bike upgrades.

 

[Tippster]

Pulley wheel question

Nino,

On your comment on the pulley wheel axels, I pulled mine appart.

The bearing dust covers appear to be different from one wheel to the other.

One wheel is idential to your picture on the right.
solid plastic right up to the bearing, with a thin hollow axle inside.
over the bearing goes a washer, one centimeter in diameter

The other wheel has a circular groove cut out around the outside of the bearing with tiny holes drilled out. over this goes a (approx) 1 inch diameter dust cover.

Any reason why the two wheels would be different?

 

[nino]

to float or not to float...

as i already pointed out the pulleys have different jobs.the upper pulley is much more stressed sideways , the lower one has not too much to do other than make the chain go around.
therefore the pulleys come with different bearing types.one has float, the other doesn't. the pulleys i tuned are really basic and aren't of the same precision as the DA ones.

 

[Tippster]

I take it the pulley with the float goes on the top, closest to the cassette?

 

[eurorider]

nino, does it matter that those cheapo Deore pulleys only have 10 teeth compared to 11 teeth on the DA 7800?

what do the stock pulleys on the 7800 weigh anyways?

btw, i like the Al "axle"

 

[Tippster]

stock pulley wheels from a 7800 mech weigh 19.1g for pair.