So in a recent video about stem length from GCN, the guys supported that the "correct" stem length is the one which the bike came with from the manufacturer. They support that this is the way the bike was meant to be ridden.

Do you agree with that view?

You can publish your view by voting in the poll!

Sort of. If a bike comes with a 110 stem and you end up with an 80, you ought to either know that you have some sort of departure from average body shape to require this, or suspect you are on the wrong size frame.

But 1-2cm either way should not be an issue.

I'm surprised they'd take that view...it doesn't really make any sense. I mean, yeah, the stock stem length is going to work for some-- maybe most-- riders, but I don't see what harm there is in 10mm or so one way or the other.

Yeah, no. That would be like saying that one shouldn’t raise or lower the saddle from how it sat on the LBS floor.

That's not exactly what they said. They were not focusing on bike fit but on handling characteristics of the bike.

Take a look at the video "What's the best stem length for you? - GCN does science" at 10:14

(sorry I'm not allowed to post links yet as I am a new member!)

From the film,

"Bike Fit should be the determining factor" 9:25

I'm not convinced that ± 1cm really makes that much difference, and have been quite happy with stems/frames that are a little long.

Keep in mind that the GCN is barely (hardly) scientific. They do some testing, but usually only do a couple of trials in each condition. In fact, they mentioned that practice with the slalom made them better, and that traffic was a hindrance with their descents.

Anyway, unless the stock stem was really odd, I'd probably use it (although I've mostly been building/customizing my bikes lately). Track stem?

I think the question assumes that the bike fits perfectly in every other way. If that were the case, I might be somewhat inclined to agree.

But fit almost always a compromise. And even in the same frame size, you'll have varying lengths of top tube among various brands. Plus, if you throw in head tube and seat tube angles, and the math quickly becomes impossibly complicated, except maybe for the pocket-protector, slide rule types. And how many of them are serious cyclists?

Another factor is weight loss. A smaller gut will allow a more stretched-out position to be comfortable than was ever possible with beer gut firmly in place.

Also relevant is how long the rider will be on the bike. What's comfortable for a one hour loop through the countryside, will be different from what would be best to use for competing in the Race Across America. Or a triathlon. Or a criterium. Or a trip to the store.

I think the #1 factor ought to be comfort, but a bunch of factors come into play there as well, as what's comfortable for one person with long arms and short legs, won't be comfortable for someone else with short arms and long legs. Even if their height and weights are identical.

So taking all of this into account, I don't see how any bike designer can say definitively what size stem a given frame size should properly use. It's all about compromises and balancing this factor vs. that factor, and hoping that the result of all this number crunching results in something that "feels right". Which is a completely subjective determination in itself.

The video doesn't have riders trying different combinations of stem and top tube - they are changing the rider's fit with every new stem. I'm not surprised that descending on a cramped reach isn't stable.

True, your crit, hitting 30 to 40 MPH, will be very dominated by aero.
Nonetheless, I wouldn't ignore aero for a 3000 mile race, although comfort and aero would both be important.
No draft rules on the RAAM and various TT and Tri races would certainly affect one's bar choice and body positioning.

Heading to the grocery store, pulling a trailer like a dragster parachute combined with a boat anchor makes all that seem a little less important.

Very good point. I'm 5'10" and probably "should" ride a 56cm frame. But with proportionally shorter legs and longer torso, I always felt more comfortable on a 54 with a 120mm stem than a 56 with a 100mm stem.

I hadn't thought of the trailer scenario, that really puts things into perspective. Or what if you plan to use aero bars? And then not all handlebars have the same reach, so you need to figure that in too. As well as the goal of maximizing comfort in all 3 different hand positions, hoods, drops, and tops. More compromises there.

Seems like such a simple subject at first, but it quickly becomes quite complicated if you worry about it too much.

#1 I'm not absorbed by road race bikes, exclusively.. ,


08, I bought a Used 26" wheel Trekking Bike and changed many parts but not the stem.

Depends on the rider. In my case, yes... it came with the right size stem. My last bike came with a 100mm stem, I experimented with a 110 and a 90 that I already had and found that the 100 was the best size. Now, had the reach on the bike been 5-10mm shorter, I probably would have opted for the 110 and answered no.

IMO bike manufacturers will equip a bike to fit the average size person whatever that is. If you look at bell curve chart its that big hump in the middle. For some of us we will be on the edges and might need to custom fit our bike to get the most comfortable fit. For others, they might not care enough and will take whatever their bikes came with. Its not enough of an issue to change things. So it depends on what you really want...