|Stem rise question||James OCLV|
Nov 20, 2002 6:57 AM
|I want to adjust the height of my handlebars. I have a threadless fork, and my LBS cut the steerer when they built the bike. I currently have an ITM Millenium stem (not sure of the degree rise). The drop from my saddle is roughly 3".
What I've done thus far is flip the stem. It has changed my drop to 2", however, I'm concerned that the stem wasn't made to be used in this fashion and thus not safe.
I did some looking around, and so far the only manufacturer that I've seen that sells a stem that doesn't have a negative rise is Bontrager. I believe their racelite stem comes in a 7 degree and a 17 degree. I guess my question is what do these "degrees" mean, and what difference whould they make in handle bar height? Additionally, I was wondering if anyone else had any other ideas as to what I could do to remedy the situation.
|Your stem is safe. Thomson has +5 rise. Do the trig. (nm)||Spunout|
Nov 20, 2002 6:58 AM
|Well, if I could do the trig I wouldn't have asked the question||James OCLV|
Nov 20, 2002 7:07 AM
|re: Ritchey makes a 90 degree stem||teschrider|
Nov 20, 2002 7:38 AM
|which = no rise. However, most headtubes already have about a 73-74 degree angle on them. Thus, a 90 degree stem will give you some rise. The Thompsom is also an excellent choice for a 5 degree rise stem. Good luck.|
|re: Ritchey makes a 90 degree stem||James OCLV|
Nov 20, 2002 8:20 AM
|Thanks. The reason that I'm confused is that my ITM has an 80 Degree rise and it looks negative; I saw a Bontrager stem with a 70 degree rise that looks less negative (almost straight). I would expect, with 90 degree = no rise, that the 70 degree would be more slanted than the 80 degree. What would the 170 degree look like?|
|Some answers.||Len J|
Nov 20, 2002 7:58 AM
|0 degree & 90 degree are the same, that will give you a stem that runs perpindicular (Sp?) to the steerer. therefor if you have a 73 degree headtube a 90 degree (or 0 degree) stem will rise 17 degrees off of parrellel to the ground. A -17 degree stem (or a 73 degree stem) will be parrellel to the ground (with a 73 degree steerer).
I'm not a math wizard, but a rule of thumb is that for a 110 stem, every 6 degrees of rise change will change the bar height by approx 1 cm. Others can get more precise, but this will get you in the ballpark.
Flipping a stem from a negative rise to a positive rise has absolutly no impact on safety. Stems are designed for this.
|re: Stem rise question||StewK|
Nov 20, 2002 8:09 AM
|Salsa has the widest range of stem rises I know of.
The easiest way to figure out how bar height and reach change is with a piece of graph paper and a protractor. Draw a horizontal line (representing the ground) on the paper, then draw another line at an angle of 73 degrees (your head tube) you can then calculate the effect of any stem size and rise.
Nov 20, 2002 8:18 AM
|Now that we have addressed stem rise. Do manufacturers measure stem length the same? And how are they measured, from the center of the steerer tube to center of the handlebars?|
|Stem Measurement: Centre-to-Centre (until proven wrong!) nm||Spunout|
Nov 20, 2002 8:19 AM
Nov 20, 2002 9:22 AM
|Back when all stems were 73 degree, the stem length could be measured by laying a scale across the top and measuring from the center of the quill bolt to the center of the bars.
Most threadless stem don't measure this way. They are measured aong a line that is parallel to the extension (regardless of the angle) and through the center point of the bars (as seen from the side). If you measure across the top, the stem will typically be 5mm longer than the advertised length.
Having said that, there are exceptions. I've measured different models of Ritchey stems that were not the same length, even though the stamped length was the same.
|Check this one out...||Spunout|
Nov 20, 2002 9:10 AM
|Looks cool. Do you know anywhere else that you can buy it? (nm)||James OCLV|
Nov 20, 2002 9:40 AM
|itm millenium adjustable...||merckx56|
Nov 20, 2002 11:31 AM
|they come in 100 and 120 lengths for 1-1/8". I'll sell you one for $100 including shipping!|
|itm millenium adjustable...||James OCLV|
Nov 20, 2002 12:38 PM
How exactly does the stem work? Do you know anyone who is currently using it, or have you used it yourself? Are the stems that you have new? I'm definately interested...
|itm millenium adjustable...||merckx56|
Nov 20, 2002 1:31 PM
|The part that goes on the steerer is completely stationary. the front 2/3 of the stem is what is actually adjustable. It hinges, if you will, and has an allen head on the side that you cannot see in the photos. The allen head bolt is connected to a ratchet type set-up. When the stem is loose, you can raise or lower it in increments. once you have it where you want it, tighten it down and ratchet catches the stationary part of the stem for a tight fit. Here's a pic of a different version, but you can see how the mechanism works. We use one in the shop to do fittings. It pretty light and stout. I've ridden one on my cross bike to get my fit down and really didn't notice any difference in stiffness nor did I worry about the stem itself moving. it's a standard 26 bar size. I don't have a new one in stock, but can get a 120 in about 3 days, so you'll be getting a brand spanking new one.|
Nov 20, 2002 1:32 PM
|email me at firstname.lastname@example.org|
Nov 20, 2002 4:05 PM
This website has a pretty good chart that will provide a reasonably accurate estimate of stem changes.
There are 360 degrees in a full circle. 90 degrees is the difference between horizontal and vertical.
Stem degrees are no different, but unfortunately, it's the point of reference that's confusing. Road bike stem angles are usually measured relative to a line that runs through the steering tube. Until the advent of threadless headsets, most stems had a 73 degree angle that made the stem extension horizontal to the ground (on a bike with a 73 degree head tube angle).
To make up for the reduced stack height of threadless headsets, manufacturers first began making 80 degree stems as a standard. An 80 degree stem would have a rise of 7 degrees above horizontal. Most 80 degree stems are now made symmetrical, so the stem can be flipped over to produce a 100 degree angle. Flipping an 80 degree stem will raise the bars about 3.6cm (for a 110mm stem) but it also requires a 10mm longer stem to produce approximately the same reach.
The second method of measuring a stem's angle uses the a line that is perpendicular to the steering tube as the reference or "zero" line. A zero degree stem by this method would be a 90 degree stem by the former method. This method seems to be pretty standard for MTB stems. You will see a lot of stems listed 6 degrees "of rise" which acutally means 6 degrees more than 90. The term "rise" as used with MTB stem can be very confusing. A 6 degree rise stem acutally has angle relative to the ground of about 23 degrees (96-73). Are you confused enough now?