News & Opinion

Ask the Bike Maven: bike fitting 101

In Ask the Bike Maven on April 11, 2011 at 8:05 AM
A properly fitted bike: seat positioned so legs can deliver maximum power to the pedals, elbows slightly bent when hands resting on the hoods

By the Bike Maven | It’s spring, prime bike-buying season. Whether you’re buying new or used, you need to know a bit about bike fitting before you make your purchase.

I know that not everyone is into long distance or fitness riding. Sometimes a quick toodle to the store is all you’re out for. So who cares how your bike fits and what position you are in on your bike? Well, l it can make a real difference. Your position on the bike affects both the efficiency with which you pedal and your comfort in doing so.

And if you are more comfortable and more efficient, you are going to enjoy riding your bike more. Unlike Stephen Harper, I admit to my agendas: I want to see as many people as possible on their bikes, and I want to see them riding as much as possible.

So what’s involved in making sure your bike fits and that you are properly positioned on it?

Your body contacts the bicycle in three areas; your hands, your seat, and your feet. Their position determines your comfort and efficiency on the bike.

The parts of a bike: note the seat tube, cranks (crank arm), stem, brake hoods, and hub, all of which I will refer to in this article (click to enlarge)

The wrong size bike can’t be made right by a bike fitting. So your first priority: buy the right size of bike. But what size is right? I am often dismayed to see “bike fittings” take place in bike shops with staff who have little or no qualifications to fit a bike. The customer gets on the bike, the bike shop employee asks “how does it feel?” Well, if you’ve been used to riding a wrong-sized bike, or you’re an adult getting back on a bike after many years, or if you’re used to riding a bike with a straight handle bar and you are getting your first bike with drop bars, a new bike will feel weird and unfamiliar. Asking you how it feels is a useless question.

Bike fitting has some scientific aspects to it. It’s not just an eyeball affair, and it’s not just how it feels to the individual rider. I’ve lectured U of T Phys. Ed. students on the basics of bike fitting–a quick overview–and it’s taken me almost 90 minutes. A proper fitting on a road bike can take an hour.

But I’m not going into that kind of detail here. What I am going to try to do is give you the basics so you at least walk out the store with the right size bike. As you get more proficient and interested in better performance on your bike, you can then go to a qualified bike fitter who will help you dial in the fit exactly to your body specifics.

Step one: proper seat height. Your leg should not be not quite fully extended at the bottom of the down stroke (leg in foreground). Aim for 20 to 30 degrees flexion at the knee

Step one: get the  seat height right. When I look at casual bike riders out on the street, the most common mistake I see is that their seat height is too low. When stopped, they can put both feet on the ground while still seated in the saddle. When I look at serious cyclists, the most common mistake I see is that their seats are too high. When at the bottom of their pedal stroke, their leg is fully extended.

When your seat height is properly adjusted, your leg will be not quite fully extended on the down stroke. You want about 20 to 30 degrees flexion at the knee at  the bottom of the pedal stroke like in the photo above. Note that the bottom of the down stroke is when the crank is parallel to the seat tube (the tube that your seat sits on top of) and not when the crank is vertical.  Also note that the ball of your foot should be on the pedal, and your foot should be level to the ground. Don’t let me ever see you riding with the heel of your shoe on the pedal, or I will stop you and chew you out.

Why is this the desired seat height? Muscles have an efficient dynamic range. Stretch them too much and they won’t contract back as strongly (think of a rubber band). If the seat is too high, your legs will be extended beyond their point of efficiency as well as comfort. Additionally, you will be swiveling your pelvis from side to side to reach the pedals. That is going to chafe your private parts. That isn’t good for you or your significant other. If the seat is too low, you aren’t getting all the power you could by stretching your legs out more, resulting in a more tiring ride.

Step two: get the bike saddles fore-and-aft adjustment right. The front of your knee should be just in front of the pedal spindle

Step two: get the seat fore-and-aft adjustment right. Correctly placing your seat over the pedals helps efficiency as well as knee comfort. With your foot parallel to the ground, the front of your knee should be just ahead of the spindle of the pedal.  The proper way to gauge this is to either drop a plumb line from your knee, or a metre stick or other straight measure (see photo above).

My choice of saddle: the Selle SMP Strike: minimally padded with good sit bone support, and radical cut-outs for long ride comfort

A quick word about saddles. Those over-padded, big-ass bike seats are much less comfortable than a smaller, firm seat. Think of wearing a Birkenstock sandal (firm, molded) compared to slippers on a long walk. You are looking for a saddle that flares a little at the back to support your sit bones. Women’s saddles flare a little wider than men’s since most women’s pelvis are wider. Rather than being heavily padded, these saddles are indented or entirely cut away at the common friction points between rider and saddle.

The tilt of the saddle also needs attention. You often see bike saddles with the nose tilted radically down. This is usually done to try to ease the pain of an uncomfortable saddle. But with the nose tilted down, the rider’s weight is thrown forward on to the handlebars, resulting in numb hands, and wrist, arm, shoulder and even neck pain. Get yourself a saddle that you are comfortable sitting on when it is flat so that your pelvis is level, and your weight is properly distributed. If you are going to splurge on any part of your bike, make it your saddle.

Step three: with your hands on the brake hoods, your elbows should be slightly bent

Step three: get the distance from saddle to handle bar right. So now that your seat is in the proper position, put your hands lightly on the brake hoods, and rest your fingers on the levers. There should be some bend in your elbows so they act as your suspension as you go over bumps and other imperfections in the road.  See the photo above. Now look down to your front wheel; the handlebar should obscure the hub.

If you have to straighten your arms to reach the handle bar and when you look down, you can see the wheel hub well behind the handlebar, you are on too large a bike frame. Conversely, if your elbows are deeply bent and when you look down, you see the wheel hub well ahead of the handlebar, you are on too small a frame. If the reach is just slightly off, then the frame size is probably okay, but you need a different length of stem (that part of the bike that connects the handlebar to the frame). Reputable bike shops will have a variety of stem lengths on hand to swap out with yours to make the fit right.

In conclusion. A full bike fitting involves many more adjustments, including adjusting handlebar height, width and stance as well as several other contact points on the bike. Tires, handlebar tape, wheels, and gear ratios all contribute to a bike’s comfort. Most of you likely won’t care about a detailed fitting. But the three basics I give you above should at least get you on the right sized frame. If the shop where you’re test riding a bike doesn’t offer at least these adjustments above, run, don’t walk to another bike shop that does.

And if you start to develop an interest in rides of greater lengths, or in racing or triathlon, then you will want to take your bike in to an expert and have a proper fitting. While we are lucky to have several good bike shops in the neighbourhood, none are equipped to do an advanced fitting. In my view, Heath Cockburn at La Bicicletta, 1180 Castlefield Avenue is the best bicycle fitter in the city. Go for the fitting, and enjoy the eye candy while you’re there; this is THE bike store in Toronto for high performance cycling. La Bicicletta has the most wonderful, luscious, sexy, fabulous bikes you can imagine. Try not to fall in love–it will be an expensive affair.

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If you have any particular bike comfort question you want to ask the Bike Maven, or you want to know more about bike fitting, post your question in the comments section below.

The Bike Maven is a Serotta-certified bicycle fitter who lives, works, and cycles in the Annex. Visit his blog at www.TOmaven.wordpress.com.

For other articles by the Bike Maven on the West Annex News, visit the Bike Maven archive.



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