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Old 03-05-11, 02:51 AM   #1
Stu In Tokyo
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How to Measure a Stem...?

OK, my new bike, the 2010 Charge Mixer 8 that I'm using to tow my trailer, the frame is kind of strange, very tall, but short. I find the reach to the bars really short, I feel cramped in the saddle. I have the seat pushed back on it's rails as far as it will go, but still, I'm wanting another couple of inches of reach. I'd also like to go up another inch or two. I put the headriser thing on the bike to get the bars up a fair bit, and I bought an adjustable stem to the bars more, but in doing so, I also move them closer to me not what I wanted.

This is the adjustable stem......






(Ignore how stuff looks on my bars, I put the stem flat to measure it)

How do you measure these things?

Bazooka calls this a 95mm stem.

What I'm looking at is this one.....



They are saying that it is 120mm

So would it make sense that the 120mm long stem is 25mm longer than the 95mm stem? I figure with the extra inch, I could still go up a bit, but stay out further....?

Any other suggestions would also be welcome.

I really do want a more upright seating position, as I am not going fast, and need to really be aware of what is going on around me.

Domo
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Old 03-05-11, 03:01 AM   #2
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Looks like 10cm to me, perhaps they measure the 95mm with the stem set at a 15° angle (or 10 or?), which would decrease effective extension.

You want a couple of INCHES more? That's kinda nuts. Trekking bar + 13cm/25° stem might be in order if you really need that much more reach. Maybe 13cm/6 degree stem and some riser bars. I'd like to see a side shot of the entire bike to say that's a good idea for sure, however.

You should not adjust saddle position to get a desired reach.

Last edited by LesterOfPuppets; 03-05-11 at 03:08 AM.
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Old 03-05-11, 07:53 AM   #3
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Thanks for the input Lester

here is a pic of he bike......



As you can see I'm hauling a trailer with the bike around Tokyo, doing deliveries.



Usual load is over 70Kg, so no high speed runs

I have the saddle all the way back (maybe not in that pic?) and I understand that it should not be, that is why I'd like to have a bit more stem, and then I could move the saddle forward a bit.

My old Cannondale that I've been riding on for 23 years, I have set up how I like it, no knee pain, back pain or such, even on long all day rides, I tried to mimic those measurements or at least get them close, the difference from the bars to the saddle was about 10 cm when I first got the bike, the Cannondale compared to the Mixer 8


Not the best pic for comparison, but that is all I have.

I think I'll go with the Ritchey adjustable stem and hope it gives me enough room, well it will certainly give me some more. No long rides in the saddle with this bike hauling beer around, longest delivery is about 30 minutes, but most are more like 15 minutes, so I can handle being cramped a bit.

Cheers!
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Old 03-05-11, 11:03 AM   #4
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Stems are measured along the centerline of the extension, from the center of the bar to the centerline of the fork. With large angles it's best to measure from the side where the centerlines can best be referenced.

Adjustable stems present a problem because the centerline distance to the fork varies as the angle changes. I'd assume that the published dimension is with the stem hinge opened straight, because once they're flexed, too many variables enter the picture.
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Old 03-05-11, 11:56 AM   #5
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You, seems to me, would divide measurement in 2 ..
steerer tube center-line to axis of the pivot,
and axis of the pivot to the center line of the handle bar.
as you note adjusting the angle changes the distance
'as the crow flies' getting shorter as you raise the angle

Steerer tube being 17 degrees off vertical
also gets closer as you as the same length straight stem
is brought higher.

Last edited by fietsbob; 03-05-11 at 12:04 PM.
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Old 03-08-11, 01:59 AM   #6
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See this website for a very useful graph showing how the length of the stem and the angle combine to set the reach. Don't forget to add the difference between your head-tube angle and 90 degrees before using that chart (as shown in the inset in the upper-right, probably about 19 degrees for the bike shown above).

I believe there is some variation between different stem manufacturers as to how stem length is measured. Although it is certainly measured center-to-center, which line they measure could be:
(1) Along the length of the stem, ignoring the angle.
(2) The extension perpendicular to the steering column; so that only stems with zero degree rise would have the same value for methods (1) and (2).
(3) As the horizontal extension level with the ground; so that only stems with -17 degrees rise would have the same value for methods (1) and (3).

If someone could put me straight on what method is normally used and whether some manufacturers do use different methods, then that would be great. Hopefully that will then also answer the questions as to how stems with adjustable angles are measured.
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Old 03-08-11, 11:46 AM   #7
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Quote:
Originally Posted by Chris_W View Post
I believe there is some variation between different stem manufacturers as to how stem length is measured. Although it is certainly measured center-to-center, which line they measure could be:
(1) Along the length of the stem, ignoring the angle.
(2) The extension perpendicular to the steering column; so that only stems with zero degree rise would have the same value for methods (1) and (2).
(3) As the horizontal extension level with the ground; so that only stems with -17 degrees rise would have the same value for methods (1) and (3).

If someone could put me straight on what method is normally used and whether some manufacturers do use different methods, then that would be great. Hopefully that will then also answer the questions as to how stems with adjustable angles are measured.
Over my 40 years selling stems in the bike industry, I've never seen one that wasn't measured on centers along the axis of the stem. I exclude hinged stems, but the ones I've seen were measured the same way while straight. There's a reason it's done this way, in that any other way would depend on the orientation of the stem requiring assuming some unknowable information to make a measurement.

Imagine a basic 100mm 17° stem. Mounted angle, down the axis length and horizontal reach would be equal, but with the same stem inverted, they'd be very different. The same applies to height which changes with orientation of angled (non 90°) stems.

So we have two sets of dimensions, angle and length, which are inherent properties of the stem, and reach and height which depend on the mounted position, and become properties of the bike as a whole. Obviously stem makers want to publish absolute measurement specs, and they do so.
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