Here’s the finished unfinished singlespeed cross frame. It may be awhile before paint it and build it up but here are some photos. The alignment turned out better once I put in the seatstays somehow. Here are some numbers:
— Seat tube off the centerline to the driveside by 0.4mm, no second pass or coldsetting.
— Head tube dipping down the driveside by 0.7mm after a few tugs / cold-setting. Head tube twist was worse – off by 1mm (TT/HT is down).
— Rear dropouts – after a minor pull on the non-driveside chainstay before putting in the seatstays it all stayed perfectly centered and spaced at 136mm abouts. The Anvil dummy axle is 137mm to allow for some pull back after welding, but I have to say that this is my best result yet. I didn’t have to touch the rear triangle or dropouts after putting in the seat stays.
One day on this blog, I want to do is provide a ‘braze-on specs’ chart for cyclocross frames. I have used my Independent Fab (year 2000) frame for this but it’s now in another state. So I have had to look online for help. It’s been much more trouble finding such specs online than I thought it’d be. If you know where to find these numbers please let me know. The Shimano framebuilder specs are good, but I’m not sure how well they apply to cross frames with such unique cantilever brakes, and new ones coming out each season. For example, the rear cable hanger to brake stud distance is one of those I call suspect. They claim 135mm minimum distance, but I know that 150mm was too short for a certain bike as the straddle cable hit the cable hanger (a lot of throw in mayfac-style cross brakes) and the frame had to be returned and the hanger bossmoved up the stays a few centimeters. So, I am going to say for cross bikes where you need lots of pull the number is closer to 160mm minimum and can be safely put at 190mm depending on frame size. The other spec that is suspect is the brake stud width. Most people will say 75-80mm in the forums, but for a cyclocross bike that is really wide. I have learned that 68mm works fine with 24mm rims and 35mm tires (able to get the wheel out fine without rubbing the tire on the brake pads. Of course, the brake pad size, type of cantilever brakes you use will dictate how well any given number works, but since I feel like there’s no guide out there I’ll write down what works for me and my 35mm wide tires and be ready to post corrections when needed.