Stem Riser Extender
 

A friend gifted me a nice road bike but it has skinnier tires than I would like and a racier geometry.

There’s little I can do about the tire size but I’m considering adding a riser extension.

Since I’m somewhat new to cycling I’m unsure if this is wise, are they safe, and are there issues of which I’m unaware?

Thanks

I've put them on a lot of bikes and I see a lot of bikes with them attached...they work fine and should be what you need...just consider you are likely going to have to replace all of the cables/housings as you are increasing the height of the bars...you may be lucky and won't have to but just a consideration to keep in mind.

The answer is "It depends". If it is a recent road bike, it probably has a carbon steerer. A stem extender should not be used on a carbon steerer.

But.......you can still get a more upright stem and tilt the bars up slightly to get your position higher.

The big issue with steerer/stem extenders is the added leverage the higher placement of the bars will exert on the top end of the steerer. This is why most carbon fork instructions restrict the use of them.

But a second issue is the added "joint/connection" between the stem and the steerer. We see so many bikes with loose stem pinch/wedge bolts with the OEM stem/steerer already. Please periodically check the various fasteners for remaining tight (in addition to any steerer cracking).

I would first explore the shape of the bars and the rise angle and reach of the stem before suggesting a riser. And, yes,, generally some or all of the control cables will need lengthening. Andy

They are safe and commonly used. Have one myself.

Just like cars and guns. When used properly any tool can do it's job without issues. With improper use or neglect the results can be deadly. We are trying to make sure the OP isn't doing something that might be more dangerous than they are OK with.

One detail that I don't think has been mentioned is that some riser's have a "no stunt or off road riding" clause. Just like many of the adjustable angle stems have too. Andy

And my ladders say I need to lose weight to use them. Same overall logic I would guess.

Do you really think someone gifted him a bike with carbon stem?

BTW, why is it everyone gets huffy about a stem extender but never preachy about wider bars? Contributes to the lever arm either way I would think.

Russian roulette is such a fun game, isn't it?

Pretty much almost every road bike now has a carbon steerer. Most aluminum road bikes now have a carbon fork.

Nope, not the same.

Ignorance is bliss?

The stem extender extends the lever forces while a wider bar would not change the lever unless you ride with both of your hands on the same side of the bar, which would cause a whole other problem in itself.

I have my doubts as to exactly how much the extender contributes to the lever arm, and would imagine it won't be an issue if it only extends it to the amount an uncut steerer would, but you can't blame members for using "better safe than sorry" as guidance for their answers.

And yes, just like your ladder, there's probably a lot of wiggle room in there. It's just risky to go in search of that limit.

Speak for yourself. urbanknight explained it well enough.

The question is do you feel lucky? Are you going for a Darwin Award? If not, lose weight or get a heavier duty ladder.

So if I put a torque wrench on a nut at the 12:00 position I get a different reading than if I put it at 9:00?

The torque at the pivot point is pretty easy to calculate. Many riders tend to pull up on the bars when they come out of the saddle to pump. I don't think the answer is as simple as being made out.

IDK, not to pick on anybody but I think some people need other people to tell them what is safe and what isn't.

I wonder just how fragile carbon steering posts really are. Didn't realize that "most" road bikes have carbon posts. The bike I put the riser on is steel, so by BF presumptive logic I could put a tow strap on that.

Now you're just being silly and arguing for the sake of arguing.

That makes sense, actually. They are still different types of forces (I'm thinking how hard your arms transfer your weight to the bars when you hit a pothole, for example, versus the power of the arms pushing and pulling), but I really have no idea what's more dangerous.

Many Thanks
 

I appreciate the info but for now will abstain from adding the riser.

My gut tells me it isn’t a good move. 😀

Thanks so much again everyone for your help.

And you can always get a more upright stem like this one:

https://ritcheylogic.com/bike/stems/...-axis-30d-stem

you do realize that has the exact same problem as a stem riser? Handle bars end up in the same place, forces on the stem will be identical. You accomplish nothing with that.

Actually, that illustrates exactly the point I'm trying to make. Whether the lever is straight or turns and angles, the only thing that tries to bend the steering tube is the overall distance from the pivot point. People have a difficult time visualizing that for some reason

Thinking about this some more, adding a longer stem will have a greater impact than a stem riser. The farther one's hands are from the steering axis the greater the torque on the steering tube. Probably the greatest force the tube will endure is the downward force from a rider out on the hoods hitting a pothole. In that scenario the height of the stem doesn't matter, but the downward force times the longer lever arm increases the load on the stem.

I think a photo of the bike along with what material the steerer tube is made of and how much higher do you want to raise the bars can help us determine if this is do-able. Also is the steerer 1", 1 1/8", threaded or no-thread headset? We're all speculating on unknowns at this point.

Thanks but I’ve decided to ride it as it is.

Wouldn’t it be moving the pivot point, or where the pressure is placed? It’s two smaller levers at a wider angle compared to one longer lever along the (allegedly) most delicate part.

FWIW they said a higher angle stem, not longer stem.

No. The shape or angularity of the lever doesn't matter. All that matters is the force vector and the straight line distance from the pivot point and the force itself. the lever (stem etc) can be I, L, S or even U shaped.

Mathematically it is the cross product of the force vector and the vector from the pivot point to where the force is applied. I hate posting a diagram on a site like this but maybe is will resonate with some.

Torque and Equilibrium (gsu.edu)

I think I get what you're saying, but the argument is that the steer tube is the delicate part (again, I have my doubts, but going with that for now). A steeper rise stem on a shorter tube would be pulling on a shorter steer tube, making the "delicate" lever shorter and stronger.

If a diagram helps us understand, go for it. I'm certainly not a physicist.

I use Satori stem riser. I wouldn't use it with carbon fiber or competition but under everyday cruiser its fine.

This isn't a physics problem, it's a hardware problem. Stem risers clamp on the steerer in a different way than stems do. I have yet to see a stem riser that is approved by the riser manufacturer for carbon. They all tend to pinch at the bottom rather than clamp along the length of the exposed steerer like a stem does. And that is because the split ends shortly above the top clamping bolt, preventing the top bolt from closing the upper part of the tube the same way the bottom bolt does. Net result is that the bottom edge digs into soft carbon instead of conforming to a steel tube.


That's the problem with theories - they don't really apply if you don't understand the actual mechanics. And then you are making dumb recommendations on bike forums that could get people hurt. So maybe your ability to do basic physics has little application to actually working on bikes and giving advice?

Don't understand the hostility. Guess that is just your nature.

As to your statements, yes, real high school level physics. But a very condescending thing to say to someone trying to understand.

As for how a stem riser attaches to a stem, and if this is going to cause another apoplexy than please, just stop reading and block me, but I don't follow your reasoning. The few I have used all attach at the top of the tube in exactly the same fashion as a stem. They have a stop about an inch or two in, require spacers, have provisions for pretensioning, and clamp with two clamping bolts along the length of insertion the same as a stem. None I have used have a sharp lower edge.

found this interesting. An explanation without all the drama

I Want To Increase My Bike Handlebar Height: Are Stem Risers Safe? (easymountainbiking.com)

There is a diagram in that link, for some reason the graphic wouldn't paste.

Yeah, I tell you, I've been trying to understand the limitations of carbon parts for some time. Hard to cut past all the emotion and deflection sometimes.

Please, you already called used the word "ignorance", so please stop sounding wounded.

Yes, you don't understand how the clamp on a steerer extender works - and even when I explained to you the difference you persist. If my description isn't enough for those gifted in high school physics to understand, what would?

It's a bad idea, and the fact that you can't understand why and have no experience with either carbon OR extenders doesn't make it okay for you to try and convince innocent third parties to do something super dumb because you think it is all simple.

I think the nuance is most stems have a complete split seam on the back where the two pinch bolts apply clamping pressure. It's a split cylinder and, as long as the two pinch bolts are torqued to similar values, the clamping pressure should be pretty consistent on the steer tube along the length of that split cylinder.

Most stem risers are not split along the entire rear-facing edge like stems are. Most have two pinch bolts, but there's usually solid material just a short bit above the upper pinch bolt. This means the stem riser will not be clamped on the steer tube uniformly. It slides over the steer tube as a split cylinder, but the lower pinch bolt compresses that split cylinder more than the upper pinch bolt can (because the cylinder is solid, and not split, above the upper pinch bolt). So it ends up looking more like a split cone than a split cylinder. I think that's what Kontact was saying earlier -- this uneven clamping, or this "split cone" hardware if you will, will end up digging that lower edge into a soft carbon steer tube (even if it's on a small scale and not outwardly visible).

Interesting. Very true that they all turn solid at the top. I will say the ones I've used are split past the top of max insertion point of the tube. There is a mechanical lip that prevents over insertion. Is that enough to equalize the pressure? Hard to say, especially with the low torque points.

Yeah, I saw the diagram and was just letting you know that I found no problem with using them if they illustrate the point. I think there's more to it than that, but the more I consider your points and the more I think about it myself, the more I realize it's just too far above my head and I don't care to delve further into the subject. Sounds like the OP made their decision no matter who wins this debate.