Wheel building - Dura Ace internal spoke nipples

b.bodegraven

An advanced wheel builders question, I'm afraid. I 've got a set of Dura Ace 7800 wheels (these were the first DA wheelset from Shimano (2004)). I want to change the rims for Chinese 24mm carbon rims and keep the hubs and spokes. The DA7800 was the wheelset with the amazing oversized hubs. The spoke nipples are not on the rim side, but on the hub side. (I'll include pictures underneath).

My DA 7900-C24 rims have the spoke nipples on the rim side. There's a difference in the diameter of the holes drilled in the 7800 rim and in the 7900 rim. The holes in the 7800 rim are narrower than an ordinary rim. The question is: "Can I use ordinary carbon rims for this project?"

The pictures of the 7800 wheel:

b.bodegraven

Maybe an extra note. This is going to be my first wheel building project. I have always built my own bicycles and up to now always refrained from wheelbuilding.

ugo.santalucia

The nipples are not internal, they are at the hub, so the spoke head sits inside the rim (as per image below). By using some clever washers (possibly the washers which are already in the rim it is possible to rebuild, better to use rims which are specifically drilled for internal nipples, with smaller holes. The main issue will be to find a rim which has exactly the same ERD dimensions, if you want to keep using the same spokes



Here they might be able to supply rims drilled for internals

https://www.lightbicycle.com/newsletter/Holes-On-Your-Carbon-Fiber-Rims.html

b.bodegraven

Yes, the system works exactly like in your drawing. As you can see also in the drawing the holes in the rim are very narrow. The narrower, the stronger, I suppose. So I am kind of worried to fit this system on an ordinary rim with wider holes. There's a lot of tension on these radial spokes for extra side stiffness purposes.

The spoke head washer is attached to the spoke and I can use both again. That is if I can find a Chinese rim with the same ERD. I will read your very interesting website and come back to this later. Thank you very much in advance!

p.s.
The present alu front rim has cracks in the rim wall near the spoke attachment (hardly vissible). The DA7900-C24 has reinforcements in the spoke hole area (bumps on every spoke hole). I suppose this is a remedy for for the too weak a construction of the DA7800.