Is there a problem with raising the handlebar stem shaft above the max. ht. line?
06-12-08, 01:07 PM
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Is there a problem with raising the handlebar stem shaft above the max. ht. line?
I started a thread in the Bicycle Mechanics forum but I did not finish. My question was about raising the stem shaft above the max. height line stamped on the stem. I wanted to know if I could safely raise the handlebar stem shaft above the max. height line stamped on the shaft. And, if so how high can I raise it? I’m 6’2” and even at the max. height line my back gets sore, especially riding on bumpy roads. Someone told me that even under normal riding the stem would disconnect from the fork. Can anyone tell me why? What would happen if I raised the stem shaft and tightened down the stem binder bolt to a higher torque?
For info I ride a Trek mountain bike.
Please help.
For info I ride a Trek mountain bike.
Please help.
06-12-08, 01:17 PM
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The max line on the stem is there so you know how high you can safely install the stem. If you raise the stem beyond that point, there won't be enough stem material in the fork to safely handle the forces involved. If you install the stem past the max insertion line, you risk having the stem fail or come loose and causing a crash that will probably plant your face into the road at whatever speed you're riding.
It sounds like you need either a bigger bike or a different stem. There are stems out there that allow installing the bars higher. Nitto Technomic and Dirtdrop stems are 2 examples.
It sounds like you need either a bigger bike or a different stem. There are stems out there that allow installing the bars higher. Nitto Technomic and Dirtdrop stems are 2 examples.
06-12-08, 03:15 PM
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I started a thread in the Bicycle Mechanics forum but I did not finish. My question was about raising the stem shaft above the max. height line stamped on the stem. I wanted to know if I could safely raise the handlebar stem shaft above the max. height line stamped on the shaft. And, if so how high can I raise it? I’m 6’2” and even at the max. height line my back gets sore, especially riding on bumpy roads. Someone told me that even under normal riding the stem would disconnect from the fork. Can anyone tell me why? What would happen if I raised the stem shaft and tightened down the stem binder bolt to a higher torque?
For info I ride a Trek mountain bike.
Please help.
For info I ride a Trek mountain bike.
Please help.
06-12-08, 03:48 PM
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There may be a factor of safety but I wouldn't risk it. I'd check bike fit and if necessary buy a new stem, as others suggested.
06-12-08, 04:23 PM
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"raise the handlebar stem shaft above the max. height line stamped on the shaft." QUOTE.
STOP, DO NOT ENTER, NO SMOKING, NO EXIT, USE NO OPEN FLAME, DO NOT DISTURB,
NO PARKING, NO TRESPASSING, NO HUNTING, NO SWIMMING, . . .
"Get it", Max Headroom?
J T
STOP, DO NOT ENTER, NO SMOKING, NO EXIT, USE NO OPEN FLAME, DO NOT DISTURB,
NO PARKING, NO TRESPASSING, NO HUNTING, NO SWIMMING, . . .
"Get it", Max Headroom?
J T
06-12-08, 04:54 PM
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It sounds like you have a standard quill stem (old style) as opposed to a threadless stem (new style). With either type it is a very bad idea to raise the stem above the maximum reccomended height.
On a quill type stem raising it too high can put the wedge bolt which secures the stem into the threaded region of the steerer tube. The threads are cut into the steerer tube so essentialy the tube walls at the threaded portion are only about half as thick as the walls of the rest of the steerer. Tightening the stem with the wedge in this area is itself enough to break the steerer tube resulting in catastophic failure which will most likely happen at the worst possible time like during heavy braking.
On a threadless stem and on a quill stem (assuming it is not in the threads but is still over max) raising the stem above max puts more leverage on the steerer tube or stem quill than they were designed to handle. This, again, will most likely result in CATASTROPHIC failure, most likely during heavy braking.
Add in the fact that you are 6'2" and probably weigh more than the average rider (I'm not saying you are fat or anything, I am 6'2" 200lbs and am in no way fat) your size will make the stresses on the stem and steerer even greater during braking than the average rider.
So, don't do it.
EVER!
On a quill type stem raising it too high can put the wedge bolt which secures the stem into the threaded region of the steerer tube. The threads are cut into the steerer tube so essentialy the tube walls at the threaded portion are only about half as thick as the walls of the rest of the steerer. Tightening the stem with the wedge in this area is itself enough to break the steerer tube resulting in catastophic failure which will most likely happen at the worst possible time like during heavy braking.
On a threadless stem and on a quill stem (assuming it is not in the threads but is still over max) raising the stem above max puts more leverage on the steerer tube or stem quill than they were designed to handle. This, again, will most likely result in CATASTROPHIC failure, most likely during heavy braking.
Add in the fact that you are 6'2" and probably weigh more than the average rider (I'm not saying you are fat or anything, I am 6'2" 200lbs and am in no way fat) your size will make the stresses on the stem and steerer even greater during braking than the average rider.
So, don't do it.
EVER!
Last edited by Cannondaler; 06-12-08 at 05:01 PM.
06-12-08, 04:55 PM
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It's also there to protect your headset bearings from being damaged by the expander wedge. If you want your bars higher, get a longer stem. bk
06-12-08, 08:02 PM
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Caution
The point of the line is to warn you of, for lack of a better term the fulcrum point. With too little of the shaft in the frame/fork and too much above you risk breaking the stem.
As to your problem, it's likely that it is more about the stem design, your seat position, handlebar design and top tube length. A good shop (and I do mean a GOOD shop) will have someone trained to fit you for your riding style. A better shop will have a tool, an adjustable bike so to speak that will allow them to let you feel what a good set-up would be like. I spent years in the shop trying to help people understand that bikes are outfitted for the average proportions of riders. We tall folk often need to change a stem to get the fit we need. Give it a shot, and consider a shock absorbing design if you don't have a shock fork.
As to your problem, it's likely that it is more about the stem design, your seat position, handlebar design and top tube length. A good shop (and I do mean a GOOD shop) will have someone trained to fit you for your riding style. A better shop will have a tool, an adjustable bike so to speak that will allow them to let you feel what a good set-up would be like. I spent years in the shop trying to help people understand that bikes are outfitted for the average proportions of riders. We tall folk often need to change a stem to get the fit we need. Give it a shot, and consider a shock absorbing design if you don't have a shock fork.
