Ritterview

An article at BikeRadar apropos to tandems, as it is all about rider weight and rim braking heat.

It appears to me that there have been improvements in recent years. When I bought my Edge carbon clinchers for my tandem in 2009, it was over the objections of Wheelbuilder, Fairwheel and Calfee. All were sure I would melt them. Calfee substituted aluminum rims for NAHBS, I think because they didn't want to appear to endorse carbon.

I switched them out in 2010 due to a non-heat warranty issue to the new Enve clincher formulation and brake pads in 2011. I noted at that time that the people at Enve now waxed confident, though it was destined for a tandem. I bought carbon rims from Enve in 2011 for my half-bike, and in my discussions with Enve they were not interested in my weight or descending habits. They hadn't been getting returns, and weren't worried anymore.

I have a rear disc, and only the front rim is exposed to brake heat. I generally just use the front caliper to modulate or supplement, relying mainly on the disc (which I've upgraded to 220 mm). With this I've had no heat problems with the front rim, though we've done a lot of descending, much of it steep (about 100,000 ft in 2012). Neither on my half-bike, with no disc, has there been any problems, even though sorely tested.

So, since carbon clinchers are becoming arguably more heat resistant, popular, cheaper, with more interest for use with tandems, are carbon clinchers now an item tandem teams can more readily consider even with, say, moderately hilly riding and calipers only?

Carbonfiberboy 

Article linky here.

PMK

FWIW, those Chinese rims I posted about have Basalt brake areas to deal with heat.

In regards to the rims though, the ones I have repaired or been asked to quote a repair on, all had damage from impact or even worse, the guy removing the tire crushed the sidewall / flange of the rim.

I would expect that current rims are made from higher temp prepregs and cured at 350. I did not read the entire article, but it did mention that the peak value was 350, so this should be a rather safe bet of them staying together. It wold take a lot of heat for enough duration to cause a failure. No doubt it can be done, but I would suspect it would be from to much mass to stop, poor technique, or maybe starting with smokin' high ambient temps that won't dissipate the heat from braking.

Maybe the question should be presented to the manufacturers, what is the cure temp of the prepregs used to make the rim? Is the resin enhanced, assuming it is epoxy, or are they using something crazy heat capable like a carbon / carbon build.

FWIW, the problem will not be from the fibres, carbon fibre is made at approx 2000 degrees C, the problem will be in the choice of the resin system.

PK

waynesulak

It sounds like they may have the heat build up issue solved. I have read that the friction generated by carbon brake tracks in wet weather is not as great as aluminum brake tracks leading to longer stopping distances. Is this a problem for teams that ride in the wet?

Also along that line wear on aluminum rims in wet weather can be substantial on a tandem. Even here in fairly dry North Texas we have worn out aluminum rims on the tandem. How do carbon brake tracks hold up to wear in wet weather compared to aluminum.

Chris_W

Shimano, HED, and some others make excellent carbon rims with aluminum brake tracks that are light enough, barely more than the full-carbon alternatives. With those options out there, why would anyone choose a full-carbon rim? Even if you're not going to make the rim explode with heavy braking, and the forecast doesn't call for any rain during your ride, then your braking on a carbon brake surfaces is never going to be as good as it would be on an aluminum brake track. Why take the risk for so few grams?

Brake performance is a key safety factor that I don't wish to make any compromises on.

Given all of the other things that the UCI make rules about, I'm still amazed that they haven't outlawed all wheels with carbon brake tracks in professional racing. I can only assume that it is due to the pressure from the manufacturers who have so much money invested in the inherently poor technology, and can make so much money from consumers who are willing to pay high prices to sacrifice their own safety in exchange for a few grams of weight savings.

TandemGeek

I'm hard pressed to be too critical of another "niche" element of the bicycling industry / enthusiast market that operates off a different set of priorities / risks / rewards than I do.

While I've dabbled in gram counting, along with a few other aspects of the cycling hobby / sport / lifestyle just to learn more about it, it's not something that I can embrace as being all that important. But, I respect the right of others to have at it. I think riding fixed-gear bikes on public roads without at least a front brake is pretty far-out there too, but since I don't live the lifestyle that's not unusual. Unicycles... yeah, well. I respect the heck of the folks who are way into it, but really don't have an interest in pursuing it.

I suspect it's much the same for folks who don't "get" the tandem thing, and there are a lot of them out there too. I'd like to think they'd look at my interest and enthusiasm for riding multi-seat tandems as intriging and worthy of their acceptance (respect would be reaching), but know that it just ain't gonna happen for some.

So it is for the folks who are simply obsessed with having the lightest, high-techiest, most expensive, or whatever else it is that trips their trigger thing on wheels... Have at it.

Note that I may reserve the right to stay the heck away from their rear wheel if I lack confidence in their equipment, riding skills or judgement... which is something that I'm constantly having to do any time we ride in groups.

diabloridr

"Niche" may be an overstatement.

Around my neck of the woods, none of the singles run carbon wheels except for when participating in a sanctioned race. I don't even know a tandem team which own a set of carbon wheels.

If you look at the photos from the tandem road races at Master's Natz last year, you'll see a whole lot more aluminum wheels than anything carbon.

If I had a fat wallet and wanted to kill a result at a race that mattered (to me), I'd pull the trigger on some carbon wheels for a flat time trial, and *might* consider it for a road race/crit. That said, the National Champs in one of the tandem TT cats at Masters Natz last year ran a lowly Rolf rear wheel, so I guess it *still* comes down to the motor.

So I guess I'll save my money to waste on something else.

merlinextraligh

I've been racing CF wheels for years, without any problem. With Yellow Swiss Stop Pads, and the added materials put in the brake tracks now, braking is fine on CF wheels.

I recently replaced a set of 404 clinchers that had aluminum braking surfaces with new 404 all carbon firecrest clinchers. I can't say I've noticed any loss of braking power, or difficulty modulating them.

I just got done riding them in West Viriginia down a bunch of hills, some of which exceeded 20% grade.

There may be a rim heating issue in certain uses (tandem, loaded touring, or cheap cf clinchers) but there isn't any braking or safety issue racing highq quailty carbon wheels today.

Ritterview

There is more to it than just the aluminum braking track and saving a few grams.

• Enve rims in particular are well regarded and considered strong, which is good for a tandem. There is no weight limit. These are all carbon.
• Enve has a patent for molded spoke holes. They are not drilled. Molding allows higher spoke tension with less likelihood of rim failure at the spoke hole. Strong spoke holes are particularly desirable in tandems as rim failure at the spoke hole appears to be a common mode of failure with tandem wheels.

• The trend in carbon rims is to dispense with the aluminum braking surface. Witness the new all carbon Zipp Firecrest, which supercedes the alumimum track 404.
• The Hed and Zipp aluminum brake track clinchers have rider weight limits well below a typical tandem team, and in the case of Zipps the warranty specifically proscribes tandems.

• The Zipp 404 aluminum track rim has 16 and 20 holes, the Hed 18 and 24. More holes need be drilled for a tandem. The Enve 65 clincher has 28 molded holes, which has, with DT Comp spokes, proven sufficient for this 295 lb team.

TandemGeek

Perhaps, but if composite wheels are a micro-niche market then are tandem a "nano-niche" market?

Seriously, I'd venture a guess that the number composite wheel pairs sold per year dwarfs the bike shop quality tandem market by several orders of magnitude.

Bear in mind, I'm talking about the composite wheel market at large, not a tandem-speciality composite wheel market.

Let's not forget, most of the products used on tandems are not made for tandems; they're simply "good enough" or adapted, with very few exceptions. And, some of the adaptations are really just cobbling together other existing products to make them work on a tandem, within reason and perhaps with reduced margins or service life expectations.

waynesulak

An interesting data point. Carbon wheels were banned at Levi's Gran Fondo for safety concerns.

Below is the link to the Levi story.

https://redkiteprayer.com/2012/07/car...or-prime-time/

TandemGeek

And this is why Red Kite Prayer remains my Favorite cycle journalism site since discovering it in Jan '11

diabloridr

That's the point I was trying to make, we're being asked to assess a "niche in a niche" market where even the anecdotal data shrinks to a literal handful of datapoints.

Worth reading for the comments section alone on this topic!

Ritterview

VeloNews reports that Specialized is introducing carbon clinchers, and with discs. Whether there is any tandem applicability depends on number of spokes, and hub widths, and whether rims are available as an individual component. There is potential for these rims to be available for less than Enve or Zipp, and from your friendly local LBS/Specialized dealer.

jnbrown

Recently I was looking at building my own carbon clinchers for my single bike with rims sourced from Farsports in China.
Since I don't race and the performance gain would be trivial my motivation was mostly that I like building wheels and it would give my bike some bling.
In the end I decided against it because I felt the risk of a rim failure was too high and concerns for my safety.
I would be ok using a rim from Zipp, Enve or even Reynolds but those are far too expensive.
I have a new found appreciation for my Velocity Aerohead rims.
Light, good braking, immune from over heating and cheap.

merlinextraligh

Saw this at DaVinci's display at the US Pro Challenge:




The bike has a rear disc and front caliper. They say no problem after a year and a half

diabloridr

Unfortunately without a few other tidbits like team weight and terrain ridden, this datapoint doesn't help a lot.

Ritterview

Okay, I guess we can be used as a proxy. Enve carbon clinchers since 2010, a rear disc, front caliper. Team weight 295 lbs. We like to do a lot of climbing, and the terrain is very steep in the Northern California. We started a Strava account to separate out our tandem rides a few months back, and have 713.5 miles with 37,280 ft elevation. Moreover, my stoker is very cautious, and we have to use our brake a lot. For example, this morning we descending Hwy 84. Team USPSPro descended it at 32.2 mph (#10 out of 1765), we used the brake to slow us to 23.1 mph (1487th / 1765). If anyone at our weight was going to have a brake problem, it would be us.

We've had no problems with the wheels in general or brake heat in particular.

merlinextraligh

I didn't drill down on the details with the rep, but my impression was that the bike had Ben ridden as a demo by various DaVinci guys. So likely ridden hard on challenging terrain by folks tending tobe on the smaller side. But that's just my extrapolation.

Ritterview

FWIW, there is a pic of what appears to be this bike among others at the DaVinci site.