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Stem length(6 posts)

Stem lengthWiaruz
Dec 19, 2003 12:17 PM
Is the length of a stem usually quoted "center to center", that is from the center of the bars to the center of the head tube?
Also, with the new style no-thread stems, how is the degree to which the stem points upwards determined?
Many thanks for your help.
re: Stem lengthMel Erickson
Dec 19, 2003 2:57 PM
Stems are generally measured center to center (center of bar clamp to center of steerer tube clamp). Stems are usually measured by the number of degrees the stem deviates from 90 degrees. You will see a variety of methods such as 105 degrees (15 degrees from 90) either up or down for many stems because they can be flip flopped. Or you might see it referred to as a 15 degree stem, same thing. Some stems cannot be flop flopped and the degree that it varies from 90 is usually downward for this type of stem. Now, is that clear as mud?
several angle standards...C-40
Dec 19, 2003 4:04 PM
MTB stem and roads stems are not usually identified with same angle measurement.

MTB stems use the method you've described. A +6 degree rise means 6 degrees more than 90. The acutal angle when mounted on the bike will be 17-18 degrees more, or 23-24 degrees above the horizontal.

Road stem are not usually specified by the method above. Road stems usually are specified by the angle formed between the steering tube and the stem. 73, 80, 82 and 84 degree stems are common for roads bike. A 73 degree stem is approx. horizontal when mounted on the bike. In MTB terms these would be -17, -10, -8 and - 6 degree stems, respectively. These stems can also be flipped over to produce angle of 107, 100, 98 and 96 degrees.
Basically the same thingMel Erickson
Dec 19, 2003 4:47 PM
Just on the other side of 90 because road stems have traditionally been mounted in that fashion. With the advent of threadless headsets and their limited adjustability it's become common for road stems to be used both ways and the nomenclature has become mixed. There are many road stems, usually from the manufacturers that produce more MTB stems, that use what I described. I also stated it is referred to degrees less than 90 (or something like that). It's really a mish mash.
This should help....coonass
Dec 19, 2003 4:19 PM
I dunno, maybe it's just meMel Erickson
Dec 19, 2003 4:58 PM
But I found that chart more confusing than helpful in my last search for a new stem. What I ended up doing is putting my old ride on the wind trainer with a plumb bob touching the center of the bar clamp and another the front of my saddle. I left the two plumb bobs in place, took off the old bike and put on the new one. I put the front of my saddle on the new bike (mounted to match my old ride as closely as possible) up to the plumb bob and then measured from the center of the steerer tube to the plumb bob that would be over the center of the bar clamp. This gave me the extension I needed and using a protractor I estimated the angle I needed. The stem I bought ended up being as close to perfect as I think I could have gotten, given the differences between the two bikes. This sounds complicated but was pretty easy. It only works if you've got a bike that fits you well and you want to duplicate the position on a new bike. It worked for me, that's all I can say.