Can a Mountain Bike Stem Be Too Short? What About Frame Size? These are questions we get A LOT from students, newsletter subscribers and random riders that found us during a search for a new bike. Over the years there has been a lot of experimenting with stem length, bar width and frame length, by bike manufacturers, bar/stem makers, top racers, myself and our coaches and many interested riders. While there is no “standard” in the industry in general stems have gotten shorter, bars wider and the length of the front of a bike (the “reach” measurement is the best measure for front of bike length, it is measured horizontally from the bottom bracket to a plumb line dropped from the center of the top of the head tube) has gotten longer over the last 10-20 years. There are outliers which have stayed the same or even moved in the opposite of these trends but I believe they are not providing optimum handling.
The stem lengths I have experimented with range from my first mountain bike which had a 150 mm stem to a zero stem that Azonic put out in the mid-late 1990′s. Bike companies have done the same, most recently Mondraker, this article explains their idea: http://www.bikerumor.com/2012/07/19/mondraker-introduces-forward-geometry-are-you-ready-for-a-10-mm-stem/ My experience was the zero stem was weird because I had to almost lean forward to keep my weight equal on both tires for cornering but, that was a long time ago when I didn’t understand body position as well as I do today and unlike the Mondraker the bike I was riding was not designed around a zero stem. As for Mondraker they tried it out for a year and I heard they handled weird and they have since gone to 30-50 mm stems. Personally I have settled into the 35-50 mm range as stems this length give the most precise and “easiest” control. By easiest I mean when riding bikes with 35-50 mm stems I am not thinking about the handling. Put me on a bike with a longer stem, even a 60 mm and it feels odd, even after 4 days of testing (enough time that the “new is weird feeling” should have vanished). I now prefer 35 mm stems but on slightly shorter bikes I run a 50 mm (still experimenting). To me this makes since has motorcycles are designed to handle well and they don’t drastically change stem length to accommodate shorter or taller riders. For some reason many riders think a long stem climbs better than a short stem, this simply isn’t true I and some of my riding buddies can climb the steepest, most technical trails with these stems, stem length has little to do with climbing, it is all about body position. So from the Mondraker experiment I would say that at least for now 10 mm is too short. From my testing and the testing of our coaches and friends we believe the ideal is 35-50 mm and 60-70 mm a compromise for riders with frames that are too short.
Frame length (reach and chainstay) for better bike handling. This is something I have experimented with for years as different sponsors have had different opinions on how long a bike should be. Mondraker obviously has too and many companies have been lengthening the reach of their bikes. Here is where I feel there is a too short and possibly a too long. In general the longer the reach measurement the bigger the “sweet spot” on the bike (the spot where all your weight is on the pedals) and more stable the ride. Of course if a bike gets too stable it is hard to maneuver. Another big frame aspect that affects handling is chainstay length, the longer the chainstay the more stable but less nimble the bike, too short a chainstay and the bike feels twitchy. One manufacturer’s large can have the same reach as another’s medium so to understand what I am calling a large, medium and small the measurements on the Canfield Brothers 2014 Balance, http://canfieldbrothers.com/frames/balance and Specialized Enduro 29er are what we will use. They make great starting points when discussing reach and chainstay length as I feel they have it pretty dialed (Canfield Brothers Balance has a reach 7mm shorter than Specialized Enduro and the Canfield brothers have short but not too short chainstays as does the enduro 29er). The tough thing for me is my height, I’m 6’3″ so I have no idea what it is like to be 5’2″ and ride a small. Fortunately our coach Andy Winohradsky is 5’6″ and I have discussed in length with him the differences between a small and medium for a guy his height. Andy has helped me shape my size theory below.
|Top Tube Length (Effective)||A||563mm||584mm||607mm||627mm|
|Top Tube Length (Actual)||B||528mm||547mm||571mm||594mm|
|Standover Height (Based on 27.5″)||D||681.5||726.5||744.5||754.5|
|Seat Tube Length||E||381mm||431.8mm||483mm||508mm|
|Head Tube Angle 160mm Fork (Internal Headset)||G||66.5°||66.5°||66.5°||66.5°|
|Head Tube Angle 160mm Fork (External Headset)||H||66°||66°||66°||66°|
|Seat Tube Angle (Effective)||I||75°||75°||75°||75°|
|Seat Tube Angle (Actual)||69.3°||69.3°||69.3°||69.3°|
|Bottom Bracket Drop||K||5.5mm||5.5mm||5.5mm||5.5mm|
|Head Tube length||L||105mm||110mmm||120mm||125mm|
All this talk on bike length as it relates to the rider, how about bike length as it relates to the trails we ride? On dirt bikes there is no real sizing for adults, just different size engines so a 5’6″ dirt biker will be riding the same length 450 cc bike as someone 6’6″ as that is the length the manufacturer feels handles best (you can shorten and lengthen the chainstay a bit but it is rarely done by most riders as it requires lengthening or shortening the chain too). If there is an ideal dirt bike length then maybe there is an ideal mountain bike length? I need to ride a few more true XL’s (remember some XL’s have the same reach as a large Canfield Balance) to test my latest theory on bike length (it used to be the longer the better for my 6’3″ body) but I am starting to feel like there might be a point where bikes are just too long for the trail. I still feel if you are between sizes move to the bigger size so you can run a nice short, great handling stem but not sure if that works if you are between a large and an XL, as I like the nimbleness of my large Enduro 29er. It is much more nimble than my XL EVO 29er and way more fun to ride but that could do as much or more with the chainstay being 26 mm shorter on the Enduro. I need to ride a XL 29er with short chainstays before I know for sure if it was the long reach or the long chainstay that made the XL EVO feel so cumbersome. I ran a 35 mm stem on the XL and I currently run a 50 mm on the L Enduro so my cockpit is only 5 mm shorter on the large but honestly, the 50 mm stem doesn’t feel as good as the 35 mm! In short I feel that bikes with 420 to 430 mm chainstays and 420 to 445 mm reach measurements handle the best given the trails that we ride. An important to thing to remember here is this whole discussion is on bike handling, for a really long ride being a little more stretched out can feel more comfortable but doesn’t feel as nimble.
Next week we will tackle the question, “can handle bars be too wide?”.