Originally Posted by
Kontact
I was a shop service manager for years. It is an exact science, and I know that because of decades of experience that I'm betting you don't have.I'll never understand why amateur mechanics post their problems on forums and then ignore any and all advice offered.
well I don't own a shop, but i have built about a dozen bikes in the last 30 years, so not exactly a total newb either. It's fine to have an an opinion that it's an exact science, but just in this thread we have 2 different people who used the recommended BB spindle length, or longer, and wound up with a crank that was too far in or too far out. Just saying results don't lie,
Originally Posted by
nfmisso
++++ total agree, bicycle components are Engineered.
Take apart an automotive engine, say in your Mercedes Benz, and you will find things that are shimmed to fit. Parts and assemblies can economically be made to limited tolerances and often there needs to be an adjustment during assembly. These adjustments are based on MEASUREMENT, which is a SCIENCE, not a random guess.
well your analogy would be great if all bicycle parts were made by Mercedes, but they're not. We have Japanese, Various other Asian, American, and quite a few European companies all
trying to maintain some kind of standard , both between older and newer generations of drive-trains, all the while constantly cooking up new "standards". The bottom bracket crank interface and number chain-rings being one area where some of the greatest changes have been made on bikes. I can remember in the last few decades on more than one occasion where there were changes made to what was even considered to be the "ideal chain-line".
It just seems like calling this an exact science is a bit of stretch.