These are the tools of the trade when it comes to truly understanding your bike. We’re using a digital caliper, a gram scale, a metric tape measure and a digital shock pump to dial in our bike.
Whenever we get a new test bike, one of the first things we check is frame alignment. While few frames are exactly perfect, it’s a good indicator for how well the frame is built. Remove the wheel to start.
Frame measurements are usually easier done with the components removed.
Use the digital caliper to check key measurements. This is particularly valuable when looking at buying a new bike or after a crash to check for damage. The dropouts should measure either 135, 142 or 150 millimeters wide, inside to inside. A little variance is okay here, but the measurement should be within 2–3 millimeters.
When replacing a suspension component, it’s important to know how to measure the size. For shocks, sizing is determined by two key measurements. The first is the eye-to-eye length, which is the distance from the center of the front-shock mount bolt to the center of the rear-shock mount bolt. This shock measures 7.875 inches (200 millimeters) “from eye to eye.”
The second measurement is the stroke, which is essentially how much the shock compresses. This is not as simple as measuring the length of the body (the slider part of the shock), since some shocks may not compress all the way into the air sleeve. Typically, it’s easiest to let the air out of the shock and compress fully to bottom out, and then measure the distance from the dust wiper to the O-ring. Once you have the eye-to-eye measurement, you have the size of the shock. This Yeti SB5c shock is 7.875 by 2 inches (200 by 51 millimeters).
The final measurement for sizing your shock is the reducer hard- ware measurements. This measurement is the outside-to-outside distance of these pieces. This shock’s front hardware measures 22 millimeters from out- side to outside.
Once you’ve determined the width of the reducers, use the opposite side of the calipers to determine the bolt-hole size. This shock uses 8-millimeter bolts.
Every new Mountain Bike Action test bike goes through a rigorous setup before ever hit- ting the trails. This digital shock pump from Fox is an invaluable tool that not only gives us a precise method for inflating forks and shocks, but also allows us to replicate settings that would otherwise be trial-and-error guesswork. Investing in a nice shock pump, digital or not, is money well-spent.
A fairly reliable way to determine the travel of a fork is to measure the distance from the dust seal to the bottom of the crown. Once you have this measurement, subtract 10 millimeters, and you have your travel. This fork has 140 millimeters of travel.
We also like to keep a log in the Notes app of our smartphone that keeps our settings for each bike. We log suspension pressures, compression and rebound settings, and even small things like component weights and tire pressures.
It might seem like a dorky endeavor to weigh every single component, but it really can make a difference. For instance, tires can vary in weight as much as 5 percent simply due to manufacturing tolerance differences. Word is, the lightest tires are the first ones that come off the line because the tooling to cut the rubber is the sharpest. While we don’t have a way to confirm this, we certainly would pack a gram scale when shopping for tires if it meant saving freebie grams.
We’ve heard too many times the story about how a rider’s 18-year-old hardtail weighed in at less than 13 pounds. The only way to truly know your bike is to put it on a digital scale. Try it; you might be surprised to learn your “25-pound” enduro bike packed on some pounds.
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