RBA Q&A: You Have Questions & We Have Answers

What would be the best way to know if a bike would be my size without actually seeing or riding it? Is top tube length the most important measurement that I should be concerned with?

Not so long ago frame size was dictated by the seat tube length, which is a nearly meaningless measurement. Then top tube length was the more popular measurement for sizing, but it still doesn’t give a clear picture of what you’re truly getting in fit. More recently, “stack” and “reach” have found their way onto the geometry charts of most brands, and those two measurements give a much more true idea of sizing.
Frame stack is the vertical length from the bottom bracket (center) to the top of the head tube. Frame reach is the horizontal length from the bottom bracket (center) to the head tube (center). The two measurements use the same points, just with one being vertical and the other horizontal. So as long as you know what those two measurements are on your current bike (and assuming that your current bike fits you), you can make a much more educated decision on the correct size of your next bike.


Can you please help/advise on some road pedal choices? I am looking at trying clipless road pedals for the first time and would like to use a pedal that offers the easiest entry/exit, especially exit. I have narrowed it down to:
1. Look Keo Easy
2. Look Keo 2 Max
3. Shimano R540
4. Shimano R550
5. Shimano PD-5800 (105)
6. Shimano PD-6800 (Ultegra)

I am concerned that the Look Keo Easy seems to have a smaller front opening and smaller platform, making it a bit harder to enter and harder to get good power contact. But, conversely, I am concerned that the Shimano or the Look Keo 2 Max may not permit as easy of an exit as the Look Keo Easy. The performance, durability, weight and cost are less important now. And, I enjoy looking for new parts for upgrades anyway; it adds to the fun of biking. But, as I am trying to learn with this, I would rather get things best for a beginner.

After having tried all the pedals on your list, except for the Shimano R540 and R550, I believe that the Keo Easy would be the best pedal to meet your needs. The Keo Easy makes exit very simple and gives you a lot of confidence knowing that unclipping at a stop will be an easy thing to do. The engagement is going to be awkward on any pedal at first, but I don’t think the difference in the front opening size will noticeably affect it. My second choice would be either the PD-5800 or 6800 from Shimano. They have a good platform size, and tension can be decreased enough to make the exit simple. The switch to clipless pedals is the biggest performance increase you can get for the dollar!


Is there any benefit to having a stem that’s carbon wrapped over aluminum? Is it stronger or better at absorbing vibrations than just an aluminum stem?

For the most part, the stem is one of the few parts on the bike that doesn’t allow much, or any, weight savings by using carbon over aluminum. In many cases, full-carbon stems are actually heavier than the top-end aluminum versions due to the need of reinforcing around the fastener bolts, which is typically six (four faceplate and two steerer) bolts. When it comes to a hybrid design of carbon-wrapped aluminum, it’s a case of fashion over function. FSA’s 0S-99 CSI is one of the few carbon/aluminum stems that’s competitive in weight (126 grams) with the top aluminum versions, but the price is much steeper, and any benefits would be much harder to measure.

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