Tuesday, August 28, 2018

Mtb geometry part one: standover (meh)

There's a lot of hokey old advice about standover on a bicycle. Standover is the distance between your crotch and the top of the bike. Standover is nice to have, but some people have unrealistic expectations based on decades-old advice about bike fitting. Standover is NOT how you fit a bike, but it's an important safety feature and a good place to start.

If you walk into a bike shop and the salesperson has you straddle the bike, asks about "clearance" and tells you that's the right size, leave the store immediately because that shop does not know what they are doing.

Regarding mountain bikes, look at an old bike from the mid-'90s or before. Rigid forks, 26" tires, horizontal top tubes, steep angles with short top tube lengths and long stems. This is what made it possible to build a mountain bike with tons of standover for the rider. When suspension forks became popular and then ubiquitous, this raised the front end of the bike, making it harder to get the frame lower. Then came longer-travel suspension forks and then 29" tires, and most bikes have a noticeable upward slant to the top tube. Gradually, getting a bike with those previously generous amounts of standover became more and more difficult.

In short, modern bikes generally don't have a lot of standover. Get used to that and move on.

To understand the numbers on a bike manufacturer's website, you need to know your true inseam. You can call this "cycling inseam" or "anatomical inseam" but this in NOT the same thing as your pants size. Your true inseam is likely an inch or two longer than your pants size.

To measure, find something flat with a square edge like a large book or a T-square stand shoeless with your back flat against the wall. Pull your measuring device up between your legs firmly. Don't hurt yourself, but get all up in there. You're looking for the bottom limit of your crotchal region, how far it is from the ground. Mark the wall at the top of your measuring device -- that's your "cycling inseam." Subtract an inch or so from that, and that's the minimum amount of standover you need.

When you start checking out bikes in person, throw a leg over the bike and stand in the middle of the frame. If the bike was designed with some level of intelligence, you should be able to stand with the nose of the saddle right behind your spine without the top of the frame touching you. On most modern bikes, you'll have barely and inch. That's OK, because moments when you're going to stand flat-footed directly straddling the top tube are exceedingly rare. you can stand on one foot, support yourself on one pedal, lean the bike over, etc when  you dismount.

But if you cannot stand anywhere over the bike at all without injuring yourself, you might want to try a few different models. Don't "size down" on a bike with a high standover, because, as I'll discuss later, the way the bike fits while you're riding it is far more important than how it fits when you're not even standing on the pedals.

If you have relatively short legs and a longer torso, you might have problems finding a frame that fits you well when riding and get a reasonable amount of standover. For people with long legs and a shorter torso, you're probably better off with a bike that fits your reach well and use a lot of exposed seatpost to make the bike fit you. More on that later.

No comments:

Post a Comment