SlamThatStem Headset Caps Let You, Uh, Slam That Stem

“Low sporting look”?

Is this something that a roadie would worry about? I’ve never worried about how my stem looks on my mountain bike, I just want to make sure it is strong.

In response to breadandbits-

Thank you for your concern. Any bicycle warranty can be void by alteration from the original assembled condition. This does fall under that category, but so do many common alterations.

Lowering the stem shouldn’t have any adverse effects on stress distribution in the steerer tube, but I will keep this in mind as I continue with future iterations.

I don’t care how it looks, but am otherwise a proponent of being able to put the stem lower than is often possible on a road bike, for aerodynamic reasons (rider position). More race organizers seem to be disallowing TT bikes in stage races in order to “level the playing field.” This is good, imho, but is also a good reason for frame manufacturers to keep shorter head tubes on some of their bikes.

Regarding a mechanical explanation, if someone asks in a genuinely curious and reasonable manner, I would respond.

Since you’re not offering a response to a question which didn’t have nearly as much hostility as your initial post, I’ll assume you don’t have a good answer.

The stem has less leverage on the steerer tube since it’s closer to the top bearing, this would put no more undue loads on it than having a taller spacer stack. There are limits on (maximum) spacer heights with carbon steerer tubes because of this leverage. The most recent limit I saw was somewhere around 20mm, though that number varies from one manufacturer to another.

Are you talking about a scenario where 3cm of spacers are put above this top cap to take the place of an OE “tall cone” spacer below the stem? That would indeed be unsafe, but that’s also missing the point of this part in the first place.

Another recommendation regarding carbon steerers is to put a spacer above the stem (as in the picture) so that the compressive forces of the stem clamp are entirely supported by the steerer tube, rather than having it spread above the top. I don’t think your concern relates to that though.

Please tell me if I’m misinterpreting your assertion, breadandbits, because at this point, I don’t buy it.

there is no void of guarantee to run your stem all the way down, it´s the way it´s suppose to be. The shims are there because people are to fat and lazy to ride their bikes the right way. I sell cannondale and we just get really happy when people wants to slam! the old bikes like the systemsix has alternative topcaps, shims add flex.

Stupid arguments aside, this is a great idea. There are so many new road bikes coming out that have tall head tubes, and again, come with 30mm top bearing cover, the front end of road bikes is getting higher. This suits most riders, however those after a sporting, or racing position find it harder to do so. Aside from purchasing a new headset, it is quite hard to find a lower bearing cover.
Well done boys.

You don’t have to look very far to find the reason for breadandbits concerns:

https://bikerumor.com/2010/06/23/broken-trek-carbon-steerer-tubes-result-of-the-wrong-stems/

“Use spacers above and below the stem- always. This is not as obvious as over torquing, but riders must have a minimum of 5mm and maximum of 40mm of spacers between the stem and the headset. In addition, a 5mm spacer is required above the stem. These spacers prevent the stem from creating a stress riser on the steerer. Racers must factor in these spacers when sizing their bike.”

The reason is that you create a specific point load if you don’t have any space between the bearing and the stem, which might cause catastrophic pfailure with most carbon steerer tubes.

Try this: take a pencil and hold it with both hands so that your two thumbnails are immediately next to each other. Now try to break the pencil. Try the same with a littlespace between the thumbnails. The latter is harder, because it is missing the pinching effect, besides having more “leverage”.

i don’t slam but i have fantasies that I might one day

Dam*, forget my last post – my bad.

i have one possible idea for the REAL reason some companies recommend at least one spacer below the stem: the stem clamp deforms the steerer tube. it makes the thing non-round (slightly), therefore putting extra stress on the compression ring, and making failure at that point slightly more possible. with a bonded-in reinforcing insert (cervelo, 3t) i would not worry one bit. im not sure i would worry anyway.
the thought of “combining two loads” is a load in itself (sorry, couldnt resist), breadandbits seems to forget that there are other companies with other recommendations/guidelines besides trek.
for instance, both cannondale and specialized recommend running ZERO spacers above the stem after the initial fitting period- their compression plugs/reinforcements support the top of the steerer very well though.

law&order – 04/28/12 – 4:57am
The shims are there because people are to fat and lazy to ride their bikes the right way. I sell cannondale and we just get really happy when people wants to slam! the old bikes like the systemsix has alternative topcaps, shims add flex.

No wonder there are so many people ride ill-fitted bikes.

The shims/spacers are there so people can adjust the handlebar height the way that suits their riding style, flexibility and aspirations, not the way that suits some clueless (bike fitting wise) and patronising shop assistants with racing background.

Link for zodiac engineering: http://www.zodiaceng.com/hardgoods

A lot of you guys have some really specific, relavant and important things to say. But many of you are a bunch of Bloody Idiots who know nothing of what you are talking about. First of all if you commented on this as a MTB’er (as am I- but view this as a roadie issue) – you were right this is a road thing so comment on MTB s*** and leave this talk to the adults. Second, all of you dorks are worried about warrany- i doubt this will come into play but do you have to spill your soul in a warranty replacemen? Put it back as it was and shut the hell up to get her fixed. If it concerns you be honest and cough up the cash- LAMO! IF people want to drop their stem lower for looks they will loose power and are lame posers (pro or not) . But some of who are flexible and can do more than 20 pushups or more ( hopefully- but not Likely) often want to drop the stem more than the bike will allow. So, this will work great for some and give negative benefit for others. Which is prob most of the people asking stupid questions and worrying about warranty. Ride the bike as it fits you best ( which most have no idea what fits them best). But those of you who do know what I mean. I often need a few more mm of drop to get where I need to be to be in the best aero position on my road and tri bike in which I also produce the most power. If you cannot touch much lower than your toes this would not apply to you. This requires flexibility- so go ahead and raise your stem as high as you can if you cannot touch you toes- You have no flexibility- sorry! Try a Hybrid.

Anyone know where I can buy one? Thanks.

Anyone who want to look cool, confidence & wanna gain more aerodynamic benefit drop that sh*t! Cause If you don’t want, just don’t do it.. why always be followers?