Warning, this post contains wheel building nerdliness. You have been warned!
Way back in the early 90s, our head wheelbuilder was lucky enough to build oodles (a technical term) of the first commercially available carbon rims in the country – the Zipp 440. The 440 was 55mm deep carbon tubular rim aimed primarily at the fast moving (and technology focussed) early 90s Triathlon market.
It’s a long time since then, and we assumed that they would all have been worn out, crashed out, or plain abused to their death by now.
It was to our surprise that we noticed a set for sale on a local forum, with a spec that looked vaguely familiar. We contacted the seller to confirm some details, and then did what we advise no one else to do – we bought some 21 year old carbon wheels!
When the wheels arrived, we were happy to see that these had indeed been built by our head wheelbuilder, all those years ago. That was the good news.
The bad news was that the original screw on hub on the rear had been replaced with an 8s Shimano, and the rebuild was at too high a tension (a common mistake – this is how most of them died). Three nipples had pulled through the rim. However, the 24 hole rim had been repaired by a reputable carbon repairer and was structurally sound, straight and true.
The 16 hole front hub had fatigued and a crack had appeared in the flange – it had to be rebuilt. The rim was perfect.
Realizing that these wheels were simply an experiment in sentimentality, XLR8 got to work.
We delaced the rims, and made a decision – we’d use the perfect 16 hole on the rear, and the 24 hole rim on the front (where it would be subjected to less stresses in the future).
Why use less spokes on the rear? We didn’t. The 16 hole rim was re-drilled* with another 8 holes. These were specifically located (and angled) to accommodate a “triplet” lacing pattern.
* Don’t do this at home kids, without the right equipment and understanding, you will damage stuff and maybe hurt yourself later … we are professionals!
The triplet pattern has 16 driveside (DS) spokes laced in a crossed pattern, and 8 spokes on the non-driveside (NDS). We used an old 32 hole Shimano 600 hub lurking in the bottom of our spares box. With only 8 NDS spokes every second spoke on the NDS flange is skipped (specific triplet or 8:16 hubs are available from White Industries, but we decided to go ghetto on these wheels as they’ll only be used occasionally, and this was a recreational exercise).
The benefit of this pattern in this instance is that NDS spoke tension is about 95% of the DS. This is almost double the usual NDS tension (of a conventionally laced wheel with an equal number of spokes on either side).
Why is that important? Well, 440s cannot take very much tension and when built conventionally, the NDS spoke tension runs at about 55% of the DS, tensions being very low. NDS spokes can slacken when the rim flexes, leading to nipples unwinding, or early spoke fatigue (due to constant tension-detension shock loading on the spoke).
We got funky on the front wheel as well. Diving into our parts bin we found an old Hope Ultralight Titanium hub, drilled for 36 holes. We “skip laced” this hub with 24 spokes to match the 24 hole rim^.
^ Don’t try this with any hub. Only the highest quality (and ideally forged) hubshells can deal with the greater loads of less spokes, and missing spokes. The same goes with skipping NDS holes with the triplet rear. You have been warned, again!
So what was the outcome? We’ve resurrected these old battleaxes, and they ride really nicely. They’ll never win a beauty contest, but they are aero enough, stiff enough, and reliable enough to wear an XLR8 decal.
After a few rides, we’ve donated these to (the den of all things caffeinated) Cafe Marius in Lennox Head, where they adorn the walls for all wheel nerds to admire.