|stem length... (fit)||gnailuh|
Nov 11, 2002 10:25 AM
|I just bought a used bike, frame size is just right and i'm trying to tune the rest of the fit. Seat height and seat fore-aft position seems relatively easy since your leg is pined between the seat and pedal. i used the knee cap to pedal vertical line for the fore-aft setup.
my question is regarding the stem length. i've seen two website, both quoting the lemond method, that the handle bar should obscure the front hub... but one says when on the hood, while the other says in the drops... which one?
i found yet another site that says if you put your elbow next to the seat tip, and reach your forarm towards the bar, the fingertips should just tough the bar.
well, my setup now if pretty good, but depending on my head and upper body position, using the hands in the drops method, i sometimes see the hub before the bar (too close) and sometimes right on, which leads me to think that i need a slightly longer stem. but if i use the elbow-forearm method, the stem seems too long... and i have long arms.
lastly, how much below the seat should the handle bar be? mine now is almost 2 inches below if i use a level. i might add that i'm very flexible.
thanks in advance... any help would be appreciated!
|You should always buy product that has little or no stems. (nm)||onespeed|
Nov 11, 2002 10:50 AM
Nov 11, 2002 12:45 PM
|"possession of nothing but twigs and seeds"||4bykn|
Nov 11, 2002 2:32 PM
|had heard it...||Frith|
Nov 11, 2002 5:58 PM
|but had to cheat and use google to remember. |
|to confuse you even more, the variables that you have raised||bill|
Nov 11, 2002 11:06 AM
|are probably not only the most subjective but the most subject to change, even within a season. Put on a couple of pounds and those bars can seem low and far away. And vice versa.
The sad truth is that there are no accurate, sound objective tests for bar height or stem length. Trial and error. What feels good. To compound that, you can get used to anything. And a lot depends on how you ride.
You need to be comfortable, pure and simple. Comfort is low enough to be aerodynamic and feel as if you are "in" the bike but not so low that you have to crane your neck to see or your back hurts. For some people this is no drop, for others it's as much as 4 or 5 inches. Comfort is far enough away from your bars (but not too far) so that something less than half of your weight is carried on your arms, with your arms relaxed and flexed a bit in the position you most often use when you ride. You should be able to lift your hands off the bars without falling forward. You shouldn't have so much weight on your hands that it hurts (although sometimes when your hands/upper body hurts, it is counterintuitevely because you are too close to the bars and are pushing back). When you are in the drops, you should be far enough so that your knees aren't banging your elbows.
In other words, not very objective. Which is why people come up with these tests. They are ridiculous, except that they sort of work.
Think about how ridiculous the bar/hub/vision thing is. It has nothing to do with anything. It depends on your neck length and your head size and the position of your eyes on your face. But it still kind of works.
I would say bar obscured when hands on the hoods is a decent starting point. After that, it's all trial and error (and you should try and err until you get it right).
|re: stem length... (fit)||laffeaux|
Nov 11, 2002 11:11 AM
|First, the obscured hub method is a general guideline and should not be used as the method to determine stem length. The best way to determine stem length is to be fit to the bike. A fit involves having various measurements taken (of your body and the bike), these then can then be used to detemine what length stem "might" work best for you on the bike.
In the abscence of a true fit, you're on the right track. The first adjustment is seat height and fore/aft measurement. The KOPS (knee over pedal spindle) is a good start. It's a bit of an approximation as well, and can be adjusted based on personal preference - i.e. I prefer being a cm or two behind the spindle. Once that's set you need to work on stem length and handlebar drop - 2" of drop is reasonable. Some people prefer more in order to achieve a more aero position, but often riders prefer less. If you're new to road biking, I'd leave it around 2" for now.
The reach to the bars is a bit subjective. You should be comfortable. You should be able to relax your grip and not feel as though you are falling forward as a result. The angle formed by your arms and chest (looking from the side) should be about 90 degrees. Beyond that it's really where you feel comfortable. Generally I'd opt for a less stretched out position (shorter stem) if you're fairly new to cycling, and move the bars further away if you start to feel cramped.
The down side of all of this, is unless you have a lot stems to try, there's a lot of guess work involved. If you have a local shop that will let you swap out stems and try different reaches, you're more apt to find a better fit. It can cost a lot to start buying stems and guessing which will work.
Best of luck.
|what Bill said||Allez Rouge|
Nov 11, 2002 11:18 AM
|Everything Bill wrote is right on, IMO. You're asking questions that have no hard/fast answers -- certainly not for all people, and not even for you as one individual for all time.
With that said:
I have always read that the bars-should-obscure-the-front-hub rule is with your hands on the hoods. Like all rules of thumb it's not exact but it does get you in the ballpark if you're not too oddly put together.
"Almost 2 inches" of drop to the bars from the saddle works out to right about 5cm, and while that's getting toward the Boy Racer end of things it's certainly not as extreme as the 7 or 8cm I've seen on many bikes.
Both of those are offered FWIW.
You might also wish to review what Keith Bontrager's views on what he terms, "The Myth of KOPS":
|Going a little further..||DINOSAUR|
Nov 11, 2002 2:46 PM
|There is no set formula for determing stem length as most of it has to do about riders anatomy, flexibility and personal preference.
I kind of like the Sheldon Brown Bike Fit a la Wombat. Place your elbow against the tip of your saddle and stretched your arm. The tips of your fingers should be somewhere between 2-4 inches from the handlebars (which is a big spread in distance).
Same goes for the front hub obscuring your handlebars when you are on the hoods, it doesn't hold water as your position can change depending on where you are positioned on your saddle.
What I did is after I found my prefered saddle position (I use the 5 cm back method...tip of saddle 5cm behind the center of your bb) then I experimented with a couple of different stem lengths and ended up with a stem that worked.
Also as your condition improves, your position on your bike will change. You will become more flexible and will be able to ride more stretched than when you first started. This might take a couple of years until you find the right position.
All being said, when I'm in the hoods and look down, I can't see my front hub...but I have long arms and I can change this if I scoot around in my saddle. I also like my saddle level so I can move around, forward or aft, depending on what I am doing.
It's about experimenting, which can be fun. Just keep track of what you do and write down your settings so you can duplicate it on another bike or if you tear your bike apart for maintenance.
|elbow to fingertip plus width of knuckles||Mariowannabe|
Nov 11, 2002 12:55 PM
|...and this is starting point. Stem length is pretty much the last decision, since it depends on so many other things. Sounds like you're off to a good start. Since it sounds like you'd be replacing the stem (as you already have the bike), ride it a while and see how you feel.|
Nov 11, 2002 3:05 PM
|If the stem has sufficient length, there should be a small amount of clearance between the knee and elbow when riding in the drops with the fingers in reach of the brake levers and the upper back in a horizontal position. I emphasize the horizontal position, because it's always possible to get the knee to hit the back of the arm (above the elbow) if you crouch low enough (with the arms bent and the nose an inch or two above the bars). Too much clearance between the knee and elbow will result in an extreme angle between the arm and torso when riding with the hands on top of the brake hoods. An extreme angle can produce shoulder pain and fatigue. Stem length should be increased primarily to adjust arm position, not to lower the upper body. If you want a lower upper body position, reduce the height of the stem.
Bars height is a topic of many debates, but placing the top of the bars 5-10cm below the top of the saddle is common. I have mine set about 9cm below on a 54cm frame. Bar height has the greatest affect on the angle of the upper body when riding on the brake hoods. It also affects the arm position when riding in the drops. If the bars are set low, a horizontal back position can be attained with only a slight bend in the arms (that's how most pro riders do it). The higher the bars are set, the more the arms must be bent and the greater the stem length required to avoid knee/elbow overlap. Lowering the bars will also produce a more aerodynamic position, but requires more back and abdominal strength to avoid placing too much weight on the hands. The amount of weight resting on the hands should be very small. A conditioned rider can ride with only a fingertip on each of the brake hoods for balance.
The optimum saddle position should be set before stem length can be determined. Dropping a plumb bob from the bony protrusion at the front of the knee, through the pedal spindle with the crankarm in the 3 o'clock position is the common starting point, but seldom the optimum position. Many riders place the knee 1-3cm behind the pedal spindle to increase the ability to apply torque to the cranks. Unfortunately, moving the saddle back can reduce the ability to spin a high cadence. Since power = torque x cadence, the idea is to find a balance between the two that allows you to apply enough torque to crank up the hills, without reducing your cadence (which would reduce power). Determining the optimum saddle position is not something that can be done quickly. It can take many hundreds of miles of experimentation to arrive at a best setting. The best setting can also vary with the terrain being ridden.
Saddle height also has an effect on pedaling efficiency. A lower saddle improves cadence, but too low will create an inefficient and uncomfortable angle of the knee at the top of the power stroke. If the saddle is too high it will force the foot to angle down at the bottom of the power stroke and/or create a knee angle that is inefficient at the bottom of the stroke. Once again, the proper balance is crucial. Moving the saddle up or down also affects the saddle fore/aft position. The saddle will move forward when the saddle is lowered and backward when the saddle is raised. The fore/aft movement is about 1/3 the amount of the up/down movement. If a significant change is height is made, a corresponding change in the fore/aft position should also be made to avoid confusing results.
Nov 12, 2002 6:45 AM
"Bars height is a topic of many debates, but placing the top of the bars 5-10cm below the top of the saddle is common. I have mine set about 9cm below on a 54cm frame."
Assuming a zero stack height and an 80degree stem, I would guess you must have at least 16cm of seatpost showing if you have a 9 cm differential from bars to saddle top. Is the frame a little small, or sized just right?
|frame's not small...||C-40|
Nov 12, 2002 9:29 AM
|I never measure the amount of post showing, since there's no standard of how to measure this accurately. The top of my saddle is 17cm above the top tube. A pretty modest height.
The 9cm drop is with no spacers and an 84 degree Ritchey WCS stem. An 80 degree ITM would increase the bar to saddle height by another 1cm.
|For more opinions and fun reading......||treeman|
Nov 11, 2002 5:43 PM
|Study the fit recommendations of these sites: |
Harris Cycles (Sheldon Brown)
Peter White Cycles
I will let you find the web addresses since I'm away from my own computer. The difference of opinions between the racer wanna-be's and the comfort conscious Rivendell cult strengthens what has been said in other posts - do what's right for you!