108 gram derailleur

[Donald]

My 108 gram Dura Ace 8-spd derailleur. I have modified many of these through the years, this is the lightest one yet. I continue to run a 12-21 cog set, even in the hilly Bay area, being out of the sddle for long periods has always worked very well for me. Three of the pins are al. I wanted to make one of the springs Ti., didn't have a long enough ti spoke for that so I just shaved down the stock spring. There are some other things I did like making the inside carbon jockey wheel plate, and some other little trick things. This derailleur started out at over 200 grams. I'm sure it will work just fine and will install it sometime soon. Actually it was 107 grams on my Ohas triple beam scale. A scale I have used since the 70's to weigh parts.

[Gumgardner]

Nice work Don.

[FAQinc]

Don't breathe on it it will snap

On the more serious side beautiful craftsmanship!

I like the idea of plastic limit screws but the back plate does look a bit fragile though.

[Fuchs]

nice but you could make it lighter

thats the xtr from a friend of me for example

[Boonen]

Nice work on both those derailleurs!! Fuchs, is there even anything from the original xtr derailleur left in that one?

Donald, there is/used to be a guy on Ebay who sells titanium springs. It's the same one who did those outer cages years ago. You're right you can't use a ti spoke for those as it's much to short. If you could replace both with a titanium one you'd save about another 10 grams.

Also with most frames I don't think you need the lower adjustment bolt, the upper one is nice to have to prevent the deraulleur from shifting into the wheel but the lower one was only really functional when there was a large cap between the smallest sprocket and the frame where you could jam your chain into. Nowadays usually there's no room for that any more anyway and it shouldn't do anything for the shifting either if the drive train is set up well.

[dunlinii]

even though this stuff is well beyond me, its really amazing.

[Donald]

Fuchs, awesome xtr, thats the lightest I have ever seen. If that would work with my Shimano levers, I might try to do a similar mod. These dura ace 8's are heavy before mods. I think I could have shaved 1 or 2 more grams of material but didn't want to push it to far. Also Boonen, thanks for the info. Its the bigger spring, connected to the pully cages that I would like to change as its the biggest one. Also my experience is that , some times, I do need the lower adj. bolt as there is a slight difference in some of my wheels, 12 cog distance to dropout. I always feel that this forum and Fairwheel bikes, Jason, etc., are some of the most knowledgeable and experienced around, and always helpful to others. Even though I don't respond much to others on the Forum doesn't mean I don't appreciate others bikes, components, tuning, etc. There are so many of you doing such great things.

[larry_ck]

That's very impressive work! I for one like seeing your tuning projects.

[mises]

Beautiful work Donald. Where did you find the plastic limit bolts? Only places I know all have minimums of 100pc.

[Donald]

I buy the nylon bolts at Home Depot, the small ones are usually in packages of 3 or so. Other poly bolts I have bought from an online store. Just google nylon, plastic, etc. fasterners or bolts and many sites will show up. Have fun on tuning various components.

[Gumgardner]

How do you know what bolts you can safely tune? What bolts/screws should we definitely stay away from?

[Donald]

There is a difference in bolts, but even good materials and manufacturing can sometimes have defects, etc. With al. bolts there are different grades of al used. One time I had a carbon bolt, M6 fail. I used one on my seatpost, bolt that holds the saddle, but that failed because I went over some real bad roads and wasn't sitting easy on the saddle. But that is not the best place to use a carbon bolt. I also use various sized tap & dies to get the right metric threads I need on some nuts and bolts. Any area, part, that has higher stress, it is best to use Ti. although I still have an ITM Mag. stem that came stock with the two M6 Al. face plate bolts, still going strong on one of my other bikes. Also a bolt that need higher torque and also bolts that lossen and need tightening from time to time are going to be stressed more. Also I weigh 140, and tend to ride easy on my equipment, even on bad roads. One should use ones best judgement, ask around, and so do something that you will worry about. Cycling should be fun, safe and reliable.

[Ypsylon]

Were you refering to the group or just all bolts in general?

Anything structural should be steel or ti. Anything close to the seatpost and the cockpit should not be carbon or aluminium, unless there are very special circumstances.

Usually you can look up the max torque a bolt can take, and if a bolt can only take 2 Nm, but you need four to keep the seatpost from slipping you know you need a different bolt. Pretty simple, really.

[Donald]

Ypsylen, I always appreciate things you say. I know you have losts of expert knowledge and experience. I have learned things from you. I was refering to all bolts in general. I'm sure most any seat post clamp that uses a single bolt has more stress on it than a two bolt clamp. I just thought I would try the carbon, and it did last about six months. I'm sure with many bolts used in seat post clamps, its those bad roads, bunny hopping, and other situations that can really stress that area, including the weight of the rider, etc. Sometimes my wife and friends say I'm a little crazy doing some of the things I do, and perhaps sometimes I can't really disagree with them.

[Ypsylon]

I wasn't meaning to critzise you or saying you were crazy, more giving an additional reply to Gumgardner.

And my experience is way more limited than what you'd think if you look at my post count. My knowledge mostly comes from reading around, not really from trying something first hand.

So theoretically speaking, with quality bolts they'll tell you the max torque the manufacturer will stand up for, which doesn't mean you can't go higher, you just do it at your own risk.

The Schmolke M5 carbon bolts are speced as 1.5 Nm. I could imagine that, depending on a lot of factors, like how your frame and seatpost mate, length of exposed seatpost, STA, setback, clamp design and what not, you might be able to get away with torquing two carbon bolts to 2 Nm each and have that hold up for quite a while. I'm no engineer and don't know jack about fatique life or spontaneous over load or whatever you would call that, so maybe if you were willing to exchange those bolts every month, they're on € 8,50 each, that might even hold up.

You might have gained more weight in added assembly paste than you lost by going with CF or Al over Ti, but that's another story.

At the end of the day it's just knowing you're doing it at your own risk and applying a bit of common sense. If something breaks and you know that's the risk you took and don't complain about the manufacturer on the internet and you think a moment about what would happen if that very bolt you want to change breaks, I think you are half way there.