Thursday, January 03, 2008


Time is running out. Vote on the right for your preferred frame material!

It's 10 degrees Fahrenheit in the shop (garage) , so still no more work there and still none of the promised pictures. Instead, a few other pix and further discussion around building a light Rando bike. First a spy shot of the oh-so-close-to-done path racer. In the tradition of spy shoots, its dark, grainy and hard to make out. But, sharp eyed viewers will
get a sense of how the finished product will look (as always, click to enlarge pix)
One Honjo is partially fitted and one to go. Tape and shellac the bars, replace the tires and change the chainring for a TA 1/8" track ring (although that Stronglight ring looks mighty pretty to my eyes).

I'm getting itchy to put this one on the road, but not until they're cleaned up a bit.

Next come some pictures of the wheels that I laced (not trued or tensioned yet) yesterday. More on that in yesterday's post.

The rims are made by Velocity, using the extrusion of the Aerohead. If you don't recognize the label, it's because the distribution rights to this rim (which is a 650B or 584 ERD size) belong to an Australian outfit called Chainring Transit Authority (or CTA). They fronted the money for having this size manufactured and got an exclusive on it. That said, their prices (even shipped from AUS) are quite fair, they offer extra services (want a hand polished rim? How about a customized drilling pattern?) and I enjoy doing business with them. Most likely, these rims will be the light-weight standard for 650B wheels for some time to come.

Here is the 100gm H2 front hub from White Industries. Lots of other hubs might have worked, but these combine lots of attributes that I like: finely polished; sexy shape (with a traditional look); nicely 'engraved' logo; nice sealed bearings, low weight, & made in the USA.

Here's the business end of the rear-hub. That's a titanium cassette carrier which helps the complete wheelset (using Sapim spokes w/ brass nipples) to weigh in at 1515gms. Not bad eh?

And if you break a spoke, any decent shop should be able to fix your wheel!

As is always the case, once you start weighing things in real life, they add up to more than theoretical weights. Also, at this point in the process I'm trying to be fairly conservative.

So let me explain theis chart. In the build kit, every item was weighed on a digital scale unless it is highlighted in yellow. We don't need the full length of the seat post and can probably get it down to its spec'd weight of 188 grams. Also, its easy to sub in a Sella Italia SLR for the
Arione. This would net a reduction of about 0.2 pounds. But, in reality for a Rando bike, we might go with a Brooks saddle for an approximate weight gain of 0.7 pounds. And, I don't know what handlebar tape we'll use, or its weight.

However, the rider at hand likes the Arione so that's going to be the basis of our computation. The wheel weight is probably going to go down a little once the rear gets re-spoked - which should compensate for the h-bar tape. And who wants to cut seat-posts?

So the real open question is frame and fork weight. I may have under-estimated here, but don't think so. The fork will have relatively short legs and a rather short steerer, so I anticipate it coming in at around 700 grams if a fairly light crown is used. I don't think that it will be a problem to hit 700 grams. The frame itself has bigger question marks. First of all, let me note that the tube set weighed in right to the gram of the Columbus spec: 1420 grams. Using BikeCad, I determined the length of each tube, center to center, and created a ratio of that to the uncut tube length. So, if a tube, C to C, is 92% of its uncut length, then I multiply 92% times its weight. In reality, the tube weight should be less than this for two reasons: 1) the tube is butted, and all trimming comes off the much heavier ends; 2) the ends aren't cut square - they are mitered and really don't quite reach to center of a joint even at their longest point. So, my calculated final tube weight is probably well over the actual cut lengths.

This takes us from an uncut weight of 1420 grams to a cut weight of 987 grams. To this I've added the 108 gram raw weight of the rear dropouts and 132 gram raw lug weight. These will also be reduced, but not by much. In any case, the cut tubes, lugs and dropouts come to 1227 grams - well under the weight of just the uncut tubes. There will be a cable guide under the BB, some cable stops on the TT, a housing stop and a chain catcher on the chain stay, and a brake bridge. I've estimated these at 5 oz, bringing the total frame weight to 1369 grams. You might note that I haven't accounted for filler (silver) or paint. So I may have under estimated total weight. But then again, I've over estimated the tube, lug and dropout weight.

The net of this is that it looks like this bike, with 32mm tires will weigh about 16.75 pounds. I'd say not bad - but not a record holder. Also we have to mount a good front rack, a bag, fenders, and a light set. Ideally the light set will be generator based. So there is still work to do. But it looks like we're on the right track. And we aren't engaged in a weight contest, just trying to keep the bike as competitive as possible without compromising its performance. That's it for tonight.



rigtenzin said...

I'm not much of a weight watcher, but your bike sounds fantastic. The idea of riding a bike that light with all the functionality intact sounds great.

Chauncey Matthews said...

That's a feather weight compared to the Great Divide Race mtb I'm building right now!
Looking forward to the pix of your rando bike.
FYI, the poll shows "cannot process" when I vote. So put me down for steel- straight gauge and lots of it!
-Chauncey Matthews