If you're anything like me and every other rider on a bmx track it's happened to you at least once.
How many times have you heard a rookie in his/her second week of racing run back to the pits to tell mum that he/she needed a 3 piece to go faster? What about the kid who saw a 2 piece crank on a bike at the store and convinced mom to buy that one for an extra 60 dollars over the same frame with a 1 piece crank?
It doesn't matter if you're guilty of any of these crimes (if you wanna call them that). I like all of you out there am guilty of them all, or I was 2 years ago in my rookie season.
And to top it all, what about noisy profiles? Have you ever seen or heard a pro ride a practice lap with cranks loud enough that they can be heard from the stands 150 feet away? Ever been angry because your own cranks either won't stay tight, or just make more noise then your mom's car?
Today we're going to discuss all of the above, and give a few solutions to the common problems that plague(d) us all at least once. I'll start on the basic concept of a bmx 3 piece crank, and how to keep them quiet. Almost any 3 piece crank made today has some form of what's known as a floating bottom bracket. It works by pinching the arms together on a spindle that has a spacer wrapped around the inside. Most of you have probably noticed that all 3 piece cranks have a bolt in the center of the crank. That bolt is used to tension the arms and bearings against the spacer that's wrapped around the spindle (the big black piece of steel that the arms slide on to). Once you tighten that bolt, the assembly acts as one large unit riding on the bearings and nothing else.
It's crucial to keep the center bolts tight on all 3 piece cranks!
When you ride with the center bolts tight you're using the 3 piece the way its meant to be used. The bearings are doing their job. But you say that when they're tight the cranks don't spin fast anymore. That's because of the nature of the bearings. Remember that the bearings used in 3 pc. cranks are from the automotive industry. They're made to support about 300 lbs more then most of us weigh. There is an upside though, ride your cranks tight like you're supposed to and not only will they stay quiet, but the bearings will clearance out with time and spin fast. It took me 2 years to wear mine in enough that they spin free.
The next common problem on 3 piece cranks is excessive noise. There are only two successful cures for this, both of which don't always work. The first one is to make sure that you put them together right. Anything loose, including the little bolt that holds the sprocket on, will make a creaking sound. A dry chain or worn sprocket will also make a lot of noise. The other cure for noisy cranks is to lube everything up with grease during assembly. This works, but it makes a big mess. I've used Valvoline wheel bearing grease, teflon lube, and I've also run them completely dry. I've found that a 3 piece that's assembled right will be quiet regardless of whether it's lubed or not. Remember that most of them use sealed bearings, and don't require ANY lubrication to work correctly.
Back to the little bolt holding the sprocket on, make sure you have it tight and make sure you space it evenly with the crank so you don't throw a chain. That little bolt is the worst cause of crooked sprockets. And don't, DON'T hit your sprocket with a hammer to try and center it!!!! If it's out of round try tightening the chain until your cranks won't spin on the tight spot. Turn the cranks until you get to the tight spot, then loosen everything and let the chain do the work. Using a hammer is a great way to taco a sprocket.
That gives us the following tips on assembling and maintaining 3 piece cranks: 1. Keep the center bolts tight. 2. Use the right spacer for aluminum and chromoly frames. The bottom brackets are different widths. 3. Noisy cranks aren't usually in need of grease, rather tightening of the bolts. 4. Don't hit your sprocket with a hammer. 5. Use locktite on center bolts that won't stay tight. So what about the psyche move rookies pull on parents to get new parts? I brought that up for all the parents out there who might read this because I know how much you all want to shell out another 160 bucks for a bike you just spent 400 on.
As I was told when I was a rookie, a rookie rider needs a bike that will do what he needs it to do. Does this mean that he'll need a 3 pc.? No, but he will need a good solid bike that won't get shady on him and kill him. A good rider can ride any crate and do well on it, if a rookie is on the track and gets hurt because his bike fell apart he may not want to come back to the sport. So what am I saying? Parents, there's no need to spend too much money on your childs bike because your child is convinced he needs more to go fast. It's better to get junior a good solid ride made by a mainstream company that's going to keep him safe around the bmx track.
To all the Juniors out there who want more parts; Don't believe the hype! Do you really need clips because you saw Super Mario clip in? Do you need a 3 piece crank because you think you can leg press as much as Danny Nelson on your 15 Rookie gate? No, and No. It's fun to go to nationals now and sit at the top of the hill during older rookie motos. Why you ask? Because of 16 clicks that can be heard all the way across the gate. It's all good in the end, just make sure you know what you're doing on flats before some psycho decides to pimp you in a turn while you're clipped in!
I'm out for now, if you have any questions or comments hit me at bmxman_69@hotmail.com.
The first column in the series