[turbomatic73]

The Velonews article from a few days ago has got me nervous about the stem I'm running on my carbon steerer--it's got one of the cutouts in between the steerer clamp bolts that Trek says is a "stress riser" and to avoid. The fork, however, is not a Trek--it's a Ridley. The stem is an FSA OS-150...fairly close looking to the one in the Velonews article.

Any general consensus from folks about such stems? Seems like most stems have these sorts of cutouts, though some are more cutout than others...

http://velonews.competitor.com/2010...rned-about-broken-carbon-steerer-tubes_121389

 

[Ventruck]

That's ridiculous imo. A LOT of stems are made with cutouts. Maybe the finish can be suspect, and bolt torque should be given attention with a carbon steerer, but I'm pretty sure most agree that this is a steerer tube issue with the Madone in particular.

*Edit: Even the stock Bontrager stem has a cutout, and that broke the steerer.

 

[NEO Dan]

Easton makes both Stems with cutouts and carbon steerer Forks, if there were a problem with that type of design I doubt they would use it...

 

[SilverStar]

Yeah...I have my suspicions, but not about stems with cutouts. Trek's "it can't possibly be OUR fault, so we'll point the finger at FSA" tactic leaves me cold.

 

[Salsa_Lover]

Are Treks good bikes?

 

[Roadrider22]

I have had several high end bikes with carbon steer tubes (in fact I have about 4 different short pieces of cut off tube in my drawer from different makers) and it is amazing how much thinner the wall thickness is in the 2010 6 series Trek Madones. I absolutely think it is just a matter of their thickness. In fact, the Bontrager Race X Lite alloy stem that comes standard with the 6 series has a large cut out on the stem side. I think we should all want plenty of carbon wall thickness in a steer tube and then it becomes a non-issue. Three manufacturers with thick carbon in their highest end bikes are Specialized, Time and Look. I am sure their are others. 3T has a much thicker wall than Alpaha Q Wolf fork that Cervelo had to recall a few years ago after several failures.

 

[frdfandc]

Looks like a positive conformation that carbon asplodes in the sunlight.

 

[Roadrider22]

In defense of the design of the 6 series fork it obvisiously works and survives 99.9% of the time which would lead one to possibly conclude that the failures could have been induced by incorrect torque or a stem design somewhat less compatible but in the end it is something that could have been avoided with a few grams more carbon.

 

[Kerry Irons]

A few grams?

something that could have been avoided with a few grams more carbon.

Add a few grams? I can see their market share "Slipping Into Darkness." Oh, the humanity!

 

[aengbretson]

Looks like a positive conformation that carbon asplodes in the sunlight.

Looks to me like it asploded in an area that doesn't see much sun

 

[ziscwg]

Looks like a positive conformation that carbon asplodes in the sunlight.

If the carbon matrix is done correctly, like UV resistant epoxy, then this is a non-issue. However, how does one know?????????

 

[ziscwg]

Torque installation was probably an issue here too as said above.

The obsession with weight that manufacturers marketing dept's have push that failure envelope. Combine that with an improper install and someone who just pulls the bars like he's lifting weights; you have a failure.

 

[DaveG]

liability

Torque installation was probably an issue here too as said above.

The obsession with weight that manufacturers marketing dept's have push that failure envelope. Combine that with an improper install and someone who just pulls the bars like he's lifting weights; you have a failure.

Even if these issues were exasperated by excessive torque or a stem cutout design, I have to wonder whether its worth it to an OEM to take the design to the limit of lightness and expose themselves to a great deal of litigation and potential losses. It just seems to me that a couple of ounces of extra carbon would go a long way to avoid trouble. As a consumer I am not sure I am good with "it only fails catastrophically less than 1% of the time"

 

[natedg200202]

In defense of the design of the 6 series fork it obvisiously works and survives 99.9% of the time which would lead one to possibly conclude that the failures could have been induced by incorrect torque or a stem design somewhat less compatible but in the end it is something that could have been avoided with a few grams more carbon.

Do you realize what you just said? 99.9% means that 1 out of 1000 will fail. I know it's just a figure of speech, but the rate of failure for a carbon fork steerer needs to be extremely low! Even if it's 1 out of a million failure, do you want to be that one?

 

[Pirx]

Do you realize what you just said? 99.9% means that 1 out of 1000 will fail. I know it's just a figure of speech, but the rate of failure for a carbon fork steerer needs to be extremely low! Even if it's 1 out of a million failure, do you want to be that one?

Well, that 1 in 1000 may be a bit on the high side, but your 1 in a million is really low. Trek probably sells only a couple of thousand of these frames to start with. Otherwise, I am fairly certain that the probability of you being struck by lightning on your next ride is a lot higher than one in a million. You may want to stay home from now on. Of course, the probability of your house burning down while you're sitting there is higher than one in a million, too...

 

[DaveG]

odds

Well, that 1 in 1000 may be a bit on the high side, but your 1 in a million is really low. Trek probably sells only a couple of thousand of these frames to start with. Otherwise, I am fairly certain that the probability of you being struck by lightning on your next ride is a lot higher than one in a million. You may want to stay home from now on. Of course, the probability of your house burning down while you're sitting there is higher than one in a million, too...

According to the National Weather Service, the odds of being struck by lightning in the US are 1 in 500,000. If your frame sales estimate is accurate (I think its very high) and any of the Velonews reports are real, then the chances of your Trek steerer shearing off would be higher than getting zapped. However, the chance of your steerer failing due to a lightning strike is very remote and you can sleep comfortably

 

[chasea]

These issues have been concerning me, as I am currently building up a new bike with an Edge 2.0 Road fork and a Thomson X2 stem, which has a cutout. The Thomson site specifically states that the stem is okay for use with carbon steerers. The Edge site does not say that a stem with a cutout will increase the chance of failure. I still plan on contacting Edge to make sure this combination is okay.

The Edge site recommends a spacer above the stem and installing the stem with a torque wrench. They are specific about the amount of torque that should be used in the installation. The Thomson site is very specific about where the steerer tube should be cut relative to the stem cutout and bolts.

Trek seems to think that the cutouts are enabling more sharp edges to dig into the tubes, causing the failures. I did notice that the Thomson stem seems to have a slight bevel around the cutout where it would contact the steerer tube. It would probably be wise, if a stem does not have this sort of relief, for a builder to relieve any area of the stem where it might contact the fork with a sharp edge; some very light work with a file or something.

Of course, any modification of any part would void that part's warranty whether or not the modification did any real damage to the performance of the part. In the case of relieving the edges, it might actually make the part safer. Its just a way for manufacturers to cover their asses. I also feel that it is easier for Trek to just blame the stem manufacturer, rather than own up to poor design on their part.

I plan on having my fork painted along with my new frame. Every carbon fork manufacturer says this will void their warranty. Plenty of carbon forks are painted with stock frames. The issue is that it is not done in-house. If it is done by a competent, experienced painter, a coat of paint should not cause catastrophic failure. But, since the part was "modified" by someone not in-house, that person must be the one responsible in the event of catastrophic failure.

Manufacturers are so focused on the lighter/stiffer/more compliant marketing strategy that they are blurring the lines on what is safe to ride. If you want to go lighter, and a part needs a rider weight limit, give it a rider weight limit. If its still iffy, don't put it in the marketplace. But if you do release a part and it fails, you better own up to it or hope the rider dies. Because consumers relay negative experiences 2 to 3 times more than positive ones.