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Can a Mountain Bike Stem Be Too Short? What About Frame Size?

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.

 

Can a mountain bike stem be too short

The crew at All Mountain Cyclery putting a 50 mm stem and 780 mm bars on a XC Race bike!

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.

Metric Small Medium Large X-Large
Top Tube Length (Effective) A 563mm 584mm 607mm 627mm
Top Tube Length (Actual) B 528mm 547mm 571mm 594mm
Reach C 400mm 420mm 438mm 457mm
Standover Height (Based on 27.5″) D 681.5 726.5 744.5 754.5
Seat Tube Length E 381mm 431.8mm 483mm 508mm
Wheel Base F 1127mm 1148mm 1171 1192mm
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°
Chainstay Length J 425mm 425mm 425mm 425mm
Bottom Bracket Drop K 5.5mm 5.5mm 5.5mm 5.5mm
Head Tube length L 105mm 110mmm 120mm 125mm
Canfield Balance

Canfield Balance

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?”.

 

 

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14 replies
  1. luis says:

    I ride a Titus Rockstar 29er with 459mm CS and it doesn’t handle switchbacks to well. Wish it was like 20mm shorter! It’s stable at speed so somewhat of a tradeoff…I guess.

    Reply
    • Gene says:

      Hi Luis,

      Bike companies are finally figuring 29er’s out and that is a long chainstay (hard to make a full suspension 29er with a short chainstay!). I’m sure when you are ready for a new bike they will be even more dialed.

      Cheers,

      Gene

      Reply
  2. Eric Hollander says:

    Great article! I am looking at those two bikes as well. I am 6″ with a 35″ inseam and my current bike has only a 16.1″ reach which I feel is too short. For many bikes going up to an XL is too large, so I need a large with a decent reach so I can run a shorter stem.

    Have you checked out the Knolly Warden? It has one of the longest reach around for a given size.

    Reply
    • Gene says:

      Hey Eric,

      Just checked out the Warden, those are big bikes, would definitely run a 35 mm stem and at 6’3″ I would still get a large! Great looking bike though, know a lot of people that love their Knollys!

      Create a great new ride,

      Gene

      Reply
  3. Esteban says:

    great stuff i am already a firm believer in the longer bar/short stem approach to more control on my ride and it has worked out great on my other bikes but am trying to square the circle w latest ride and hope you can shed some light….I am 6’1″ and have a New Funk La Ruta 29er ( 70 deg head angle and 24.6″ top tube) )went w Enve bar 760mm, 9 degree sweep, had 35MM stem but it was WAY twitchy…change to 90 MM stem that improved things a lot so now trying to figure out why. Fork is fox 2014 Float 32 w 51MM offset so front axle is pretty far ahead of head tube centerline already maybe this is why ? So now with 90mm stem is the ” effective stem length” really 39mm taking into account the axle being offset forward? PS I put a 70MM stem on and seems like best so far but still curious as to relation of axle offset on “effective” stem length…

    Reply
    • Gene says:

      Hi Esteban,

      A lot of things can make a bike twitchy, including the rider. That 70 degree head angle is scary steep and big part of the twitchy feeling. Having spent a lot of time talking with Bryson Martin (fromer owner of Tenneco Marzocchi and founder of DVO suspension) about head angles and forks and he said most companies haven’t figured out the right amount of “trail” for 29ers and 650bs, that can greatly affect the handling. I honestly don’t know for sure the answer to your question about fork offset and how it might change “effective stem length”. The main benefit of short stems has little to do with fork offset, the are simply shorter levers, example: if you have a 120 mm stem and I have a 35 mm stem and we both “steer” twenty degrees to the tip of your stem and your bars are going to move quite a bit more than mine. The second benefit is weight placement, the longer the stem the more your weight moves forward making it harder to keep all of your weight on the pedals. I hope that helps. If you have 1.5 headtube look into getting an “Angle Set” headset and slacken that head angle a degree or two. That will make the bike less twitchy and all hills not seem so steep!

      Cheers,

      Gene

      Reply
  4. Paul Wintermute says:

    Hi Gene.
    I’ve been thinking a lot about modern trail bike geometry trends since I was in the market for a new bike last year (got a Mach 6 two months ago). Here are my thoughts: the trend had been towards a longer top tube (reach), shorter chain stay, and slacker HT angle, with shorter stems and wider bars. Personally I love all the above but the push towards 66 even 65 deg head tube angles, larger wheels, and ever longer top tubes on trail bikes have a negative side effect: wheelbase. Sure frame builders have tried to counter the ever expanding wheelbase with shorter CS but they can only go so far before there is clearance issues especially with 150-160mm travel. I think Pivot made a nice compromise and kept the TT and reach reasonable along with sub 17″ chain stays to counter the 66 deg HA. Giving a nice balance between nimbleness and stability. Look at the new SC Nomad. The top tube is not very long at all. I argue they are trying to keep wheelbase in check with that 65 deg HA. All mountain/trail bikes have a difficult balancing act especially when trying to maintain the nimbleness that the old 26″ bikes had with the stability to ride DH trails. The best of the new class of “enduro” bikes have been pulling it off amazingly well.
    Anyways I don’t think Top tubes are going to get much longer on average and boy are we lucky to have such amazing bikes to ride!
    Thanks Coach,
    Paul
    DH student from many years ago

    Reply
  5. Simon says:

    Good article, opens up the thorney debate over frame type / wheel size nicely. I have switched recently to a nukeproof mega tr XL, with 70mm stem, & 720mm bars (warhead low risers). The frame is their 26″ wheel version with stand flow ZTR rims with maxxis DHR2′s. Me bring 6’2″. Fits perfect great stability yet nimble in tight techy trails.interestingly my wheel / tyre set up is near identical to 275′s with skinny tyres…..plus lighter / stronger / etc.

    Reply
  6. Troy Smith says:

    I’m not sure you can really point to motorcycles as evidence that there is an ideal size, regardless of the size of rider. I think it’s far more likely that, for economic reasons, motorcycles are sized according to the best compromise of performance for the most common sizes of riders. It’s much more profitable to only manufacture one size and make everyone ride it. It’s still far from ideal for very large or very small riders.

    Reply
  7. Brian says:

    That is the first time I have heard that the 10mm Mondraker handles poorly. Where are you getting that information from? Have you tested it yourself? As far as I’ve heard, the only reason they are coming with 30mm stems now is because most people wanted the ability to lower it down; not because it handled better.

    Reply
    • Gene says:

      Hi Brian, I have not ridden the Mondraker. I was told by a friend who works for Mondraker that it didn’t work as well as expected. Don’t think it was the stem so much as the 40mm longer (than previous models) reach on the frame making the wheelbase too big. Not sure this worth arguing over, my whole point is short stems and longer frames are better but POSSIBLY only up to a point.

      Thanks for your input,

      Gene

      Reply
      • Brian says:

        Hi Gene,

        Thanks for the reply. I definitely hear your point on that and I don’t mean to argue over it. It’s just that I was planning to go with a Mondraker with a 10mm stem myself as the numbers all seem to be perfect for me. However, I too have not ridden it and am only going off of the opinions and reviews of others. Most people do seem to opt for the 30mm stem on the bike to get their bars lower but I actually prefer a slightly higher bar like Fabien Barel so the 10mm stem would put it right in the ideal spot for me with a 20mm rise bar. However, this does make me somewhat concerned that maybe the wheelbase will be a bit too long or the stem too short. If I go a frame size smaller, I could use the 30mm stem but then I’d have to get a larger 40mm rise bar and compromise on some other things. Hmm…

        Reply

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