ASK MBACTION

DRIVETRAIN DILEMMA

Q: I am just about to purchase a new bike from my local bike shop, and it is between a Specialized Camber Comp 29 and 27.5. The suspension components are equal, but the drivetrain and brakes are from different manufacturers. I have had experience with the Shimano group found on the 29er but not with the SRAM group on the 27.5 build. Which do you prefer? I am progressing out of a 26-inch-wheeled bike, so either 29 or 27.5 will be new to me as far as wheel size goes. Thanks for the input.

—Shannon Sullivan, who wants it to shift gears

A: The more important question of the two is, which wheel size is best? The drivetrain thing is almost a moot point. Sure, Shimano and SRAM have different ergonomics, feel, etc., but both systems work very well. The same could be said about the wheel-size choice, as there are good arguments for both 27.5 and 29er wheels. Bottom line, though: you should make the decision based on the wheels and not the parts bolted to the frame. Twenty-niners roll over obstacles easier but tend to be slightly heavier. The 27.5 bikes are more maneuverable but don’t plow over things as well. The 29ers often feel more efficient, but 27.5 bikes can pick their way through technical trails more easily.
Our advice would be to test both wheel sizes before making the choice, even if it’s not the Specialized Camber you are planning to buy. Once you’re set on the right wheel size for your particular riding style, you have your decision. Don’t pay attention to the brand name on the derailleurs as much as the wheel size stamped on the side of the tire.

SHOCKING ADVICE

Q: In a recent issue’s “Ask MBA” in “How Much Should I Pump?,” your response to Trevor, “who has a bad mechanic,” sent the wrong message. First, you don’t know if the advice was correct or incorrect for his bike. Second, you don’t know how Trevor asked the question. Did he want to understand how to adjust the pressure for all bikes or just what he has? Why assume it was wrong advice when you don’t know the context or requirements in this particular case?

The end result likely angered many mechanics. They often don’t have time to go into detail, and many customers aren’t capable of understanding or are not even interested in the details. To call this one out as a “bad mechanic” is really questionable when you’re trying to maintain readership and credibility.

—Tim King, who has a shock pump in hand

A: We often hear inexperienced riders and mechanics give what we would consider lazy advice. Telling riders, “Just put your weight in there” is a terrible recommendation, unless that number just happens to be right for the rider’s particular shock, suspension design, frame, leverage ratio, riding style, etc. And what are the chances of that? There’s a heck of a lot more to setting up your shock than simply weighing yourself and then hitting the shock pump until the number matches whatever you saw on the bathroom scale that morning. Bottom line: there’s nothing wrong with suggesting that riders rely on sag and then set their damping up to fine-tune the suspension, but if we told everyone to put their body weight’s worth of psi in their shock, we’d be offering terrible advice. Check out our “Pro Tips” on how to set up you suspension.


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