How Do You Determine the Proper Stem Length and the Rise or Drop for Your Road Bike(s): Part One, Length.
I was called a geek/nerd for my post yesterday by a commenter. Folks, if the $#!+ fits, wear it… And that’s comfy as my bath robe. I am an unapologetic bike geek, and I can do better than yesterday’s post.
The stem is an often looked at as an afterthought. Something that simply comes on the bike to hold the handlebar – and most never know that there exists a greater purpose. The stem is really the key to fitting the cockpit of the bike to the cyclist. In terms of dinner, most people look at the stem as the bottom bun of the perfect barbecue bacon burger with onion straws and queso (try it, it’s freaking awesome, just wait till you’re in-season – you can thank me later). My friends, the stem is the bacon. If it isn’t right, the bike may never really feel right. Getting the stem correct is pretty important, especially if one doesn’t know what one is doing, in terms of ride comfort and enjoyment.
I watched a video yesterday from GCN in which the presenter asked the pros how they determined their stem length. There were guys who had stems ranging from 120mm all the way up to 150mm in length and the common rise was between -10 & -17° but some went wild with a -25° (a little too much for my tastes). What was most interesting (perhaps jaw dropping) was the response from Adam Blythe, who says he’s never had a bike fit but he knows he wants a stem between 120 and 140mm based on feel.
But… but… HOW? Oh no, that just won’t do for one of us mere mortals! It may work for Adam, he’s a pro and he’s got a team that’ll hook him up with whatever he wants. We’re not as lucky, so I’ve got the technical aspects for you and I’m geeky enough to know how to use that information. I’ve got, what, four road bikes now, if you take the tandem into account, five if you count my Cannondale (we count that as my wife’s nowadays).
I’ve got a -6° x 100mm FSA stem on the Venge, a -17° x 90mm Bontrager stem on the 5200, a -12° x 130mm Origin 8 stem on the tandem, and a -12° x 110mm Specialized stem on the Diverge (gravel bike). The difference between a 17° rise and a -17° rise is just flipping the stem upside down.
So how did I determine the stem lengths I needed? I’ve got four different road bikes and four different stem lengths – and only the Venge has a stem that matches the original that came on the bike. Now pay attention, because this is important, the distance from the tip of the saddle to the center of the handlebar on three of those bikes is exactly 22-1/2″ (57.15cm). The gravel bike is at 22″ (55.8cm) and I did that on purpose. I was planning on putting a 120 on there but opted for the 110 so I could sit a little more upright when I rode on dirt roads. Less stretch = more upright.
Here’s how this all works… First, when you’re a geek like I happen to be, you only need one bike fitting. You take the numbers from the initial fit and transfer them to subsequent bikes after you watch how the numbers are gathered and come together to determine what to adjust. My fulcrum bike, the bike which all others in the stable are built around, is the Specialized. That bike came with a Specialized 100mm stem, I simply picked up an FSA stem to replace it for weight and looks. The fit that I had done on that bike was extensive. So, I had my foundation and I rode it… a lot.
From my bike fit in 2013…
Without getting too technical, over the course of ten or fifteen thousand miles, my body became used to that position. A few minor tweaks here or there is all that was done to the bike after that fitting. I began transferring numbers to the Trek, which needed a bit of work from its original pieces and parts:
If memory serves, the original stem that came on the 5200 was 100mm but it put me in a terrible position. The original stem was discarded before the bike even came home with me and swapped for the one above… As I grew more comfortable on the Specialized, I was able to stretch out more on the Trek. I transferred the reach (22-1/2″) from the Venge to the Trek. That required new quill stem adapter, a 90mm stem, and I had a 10° stem, flipped, on there for years. It was only recently I decided to go with the negative rise and put a flipped 17 on it:
A few years ago, we bought the Co-Motion tandem. I knew nothing about tandems back then, and ours was converted from a flat-bar hybrid to the awesome road steed it is now, so there were a lot of numbers to take into account:
Because of my lack of knowledge with that style of bike, and because it was new, I took my Venge to the shop and let them match up the tandem captain position as best they could given the wildly different geometries. In order to get the reach right, the bike needed a whopper of a 130mm stem.
For the gravel bike, I wanted to be able to keep my head up and eyes forward a little easier so I could see potholes in the dirt roads, so when I brought the bike home and started setting it up, I set the saddle where it needed to be, took all of the spacers from beneath the stem that I could, and installed them over the stem (lowering the bar)… Then I measured out 22-1/2″ to get my 120mm stem length, then subtracted 10mm to bring the bar a little closer so I’d sit up:
Here’s where this gets technical…. Many cyclists make the mistake of trying to move the one thing that can be moved to make the stem work – the saddle. Unfortunately, that’s all wrong. We rarely, if ever, change the reach by moving the saddle. Once you get that saddle locked into your power position (where the front of the leading kneecap is directly over the pedal axle when the crank arms are parallel to the ground) and the height is set, the saddle position doesn’t change to fix reach issues. You change the reach by changing the stem, which is why I have four bikes with four different stem lengths… I’ve got four bikes with four varying geometries and the goal is to get each cockpit to feel like the other, as much as possible. We do all of this at the stem…
Set the saddle where it needs to be, then measure from the nose of the saddle to the center of the handlebar of your most comfortable bike (or the one you had fitted to you, ideally), and that’ll get you close. There are variances to be dealt with, of course. Different saddles, different handlebars, etc… but when you’re dealing with different geometries and different bikes, you end up getting the bikes as close to your “A” bike as possible. It’s rarely, if ever, a perfect fit going from one bike to another, especially when the geometries of the frames change. Close is usually good enough, just as long as it is, indeed, close.
So that deals with stem length. I’ll get into the rise or drop tomorrow.