[ This is the second of a series of short interviews with John. In this interview John touches on the importance of a straight frame. If you have a topic or questions you’d like discussed please send us a note.]
Q What does it mean to have a straight bike?
A straight bike is a bike where the critical points of the frame align in a center plane which is in the same center plane as the front and the rear wheels. Everything aligns centered through the same plane.
If the frame isn’t straight, when you go fast it will wobble or it won’t corner properly. It will scare you. So you can’t ride a crooked frame fast, but you won’t know it until it’s too late.
So the straighter the bike, the more confidence you’ll feel while riding – you’ll actually be able to feel it. It’s like driving a car. Some cars will do 100 mph and some won’t. Some cars will scare the crap out of you when they hit 70mph.
The straighter the frame and fork (and wheels), the straighter the bike, the faster you can gowith confidence. That’s the main thing.
There are tolerances for a straight bike. Paramount/Waterford had the tightest tolerance bikes that were available. That’s where I learned to build frames and forks and thats how I still make my bikes.
Q: What thought process goes into building a straight bike?
There’s a proper sequence of events for aligning a frame. You have to do frame alignment and fork alignment. You could have a perfectly straight frame and if the fork is off you could still have a wobble issues, or vice versa. You could have a perfectly straight fork but if the frame is off, the front wheel will fight with the back wheel over who’s going to be the boss and which way to go. This is
what we call high speed wobble. It’s not just that the back feels squirrely but you’ll actually get an oscillation of the frame at speed. The more speed the more wobble you’ll get. It can actually wobble you right off the road.
A lot of people can make a frame so it looks like a bicycle, but it might not have the proper angles or the proper weight distribution or proper critical frame point orientation. It might not have the back wheel tracking immediately behind the front wheel. It will just ride stupid and feel wrong.
Q Have you ever ridden a bike like this?
I have. It’s scary. Once a bike starts to wobble you have to slow down until it doesn’t wobble any more and then that’s as fast as you can go. On a good bike you should be able to ride at 60 miles per hour and it should just feel like it’s on a rail, really confident, like it’s solid and secure.
Q what’s the experience like of riding a straight bike?
The bike feels like part of you and like you’re part of the bike. A rider will know that the bike feels right.
Q: Tell me about the role of the alignment table.
The alignment table is a tool for measuring the results after fixturing and brazing and for correcting minor deviations from the tolerances. The alignment table is critical in the building process – you can’t build a straight bike without being able to measure the straightness through out the building process.
It’s a tool for quantifying the results of the frame throughout and at the end of the process. It’s a measurement tool and is also used for cold-setting, or bending the frame.
The alignment table is a tool for testing the frame. But the ultimate test is the ride.
Q: So frames can be bent?
You can do some bending of a metal frame. Carbon frame alignment depends on how they come out of the molds – they’re as straight as they’re going to be when they come out of the mold. Welded frames are less bendable, unless the frame material is a softer metal. A metal frame can be aligned (cold set) to some degree, but the back and front wheel still might not be in alignment.
Q: Can you tell me more about wheels and straight bikes?
When building a bike you build around the wheel/tire that the bike is designed for, so we use a guage wheel as another measuring tool,and the wheel must be “scary straight”.
You should learn how to build wheels before learning how to build a bike. In my opinion you can’t be as good of a frame/fork builder without being a good wheel builder. Talking about wheels is like talking about frames/forks or fitting, there is a lot to talk about here.
A: So it’s a very technical process?
It’s a function of process and the conscientiousness of the builder. You should to be able to trust what the builder is producing. A builders reputation means quite a bit.
So a good builder will understand how to build the bike through the whole process so by the time the rider gets the bike, it’s the way it’s supposed tobe – in alignment and in proper fit.
The most important part of a straight bike is the frame, then the fork, then the wheels, but then we must also have a properly fitting bike. You can’t have one without the other.