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Melted ENVY Rims

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Melted ENVY Rims

Old 07-18-19, 10:52 AM
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merlinextraligh
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Melted ENVY Rims

We've been running ENVE rims on our Calfee Dragonfly for the last 4 plus years. (Classic 65 28 spoke rear, Classic 45 28 spoke front) I estimate that we had 20,000 plus trouble free miles on the wheels.

That all ended this weekend in a matter of minutes on the descent of Walnut Gap in the Hot Dogget ride in Mars Hill NC.

We completely melted the front rim, causing the wheel to partially buckle and the tire bead to expand to the point the tire blew off.

Walnut Gap is a 9% grade and we had reached a max speed of 42 mph before the failure. When I put the brakes on to slow for turn, I could here and feel the front pads pulsating on the rim. Fortunately, I decided to stop and check it out, slowing to about 10 mph before everything let loose.

To keep this readable, I'm going to break this up into several separate posts.



front wheel


closeup of failure


note bulged brake track


brake track


blew a hole a foot long
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Old 07-18-19, 11:06 AM
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While we've had the bike for 4 plus years, this is the first time wed done any major descents on it. (we keep our Robusta in NC, and usually use it for mountainous rides)

The Calfee was originally set up with Dura Ace Caliper brakes, and has great stopping power.

In spite of the fact that we're a larger team (350lbs), I've never been too concerned with brake heating issues because our riding style is to bomb descents, not ride the brakes, and only use them for short bursts before turns. For example we've done the Haleakala descent in Hawaii with no over heating issues at all (albeit on aluminum rims).

However, using carbon clinchers on a tandem with sharp relatively long descents, I was concerned enough to put a rear disc brake on for Hot Dogget, with the theory being that I could do a lot of braking with the rear disc, and limit use of the front brake, and spread that use out. Unfortunately the rear cable actuated Bengal disc brake did not produce as much brake force as I would have hoped and I ended up using the front more than expected.

That said, I was shocked we completely destroyed the front rim in such a short time. We were 17 miles into the ride and had done two short fast descents with very little braking, and then the one steep descent of Walnut Gap.

In a matter of minutes we were able to turn the front brake track to toast in multiple spots (ironically the wheel looked much worse hot.as it cooled off some of the melted pieces settled mostly back in place) fold the rim in one spot, and bend the bead open in spot large enough for 12" blow out.
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Old 07-18-19, 11:13 AM
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After getting home, and assessing my repair options (unfortuantely ENVE no longer makes 28 spoke rims suitable for tandems) I discovered that our rear rim is also toast. Before I put the Bengal disc on the back, we did one ride in North Carolina on the Blue Ridge Parkway using a rear caliper brake.

The BRP is not very steep (almost nothing above 8%) and the descent we did was not technical. Yet in the course of that one descent, we heated the rear rim enough to warp the bead to the point it is also no longer safe to ride.

I put all this info out as one data point, not necessarily to bash carbon clinchers. Personally, I would not ride ENVE classics in the mountains on a tandem with a decent sized team and rim brakes in the mountains. Of course that may be of limited relevance now, given that they are no longer available.
saw this bulge after we had ridden another 70 miles. Glad it didnt let go


a worse bulge


rear brake track
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Old 07-18-19, 11:26 AM
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Wow, I assume you were using the appropriate pads for those carbon wheels?
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Old 07-18-19, 11:37 AM
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Glad you are still here to write about the woes!!!

Keep on ENVE to get this resolved. Do they have 32 spoke wheels? Anything else suitable? Is this covered by warranty? Seems like a design issue more than a wear issue.

I was going to suggest either discs or drums. Disc rotors, of course, come in different sizes. Can you get the biggest one available installed?

I suppose it is time to start experimenting with different calipers. TRP makes the hybrid mechanical/hydraulic which is worth considering. Upgrade to full hydro?
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Old 07-18-19, 12:48 PM
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255mm rotors?

https://www.bicycledesigner.com/bike...tor-255mm.html

Do the pads heat up?
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Old 07-18-19, 12:54 PM
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Originally Posted by jadocs View Post
Wow, I assume you were using the appropriate pads for those carbon wheels?
Brand new ENVE pads, specific for ENVE rims
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Old 07-18-19, 01:07 PM
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Originally Posted by CliffordK View Post
Glad you are still here to write about the woes!!!
Thanks. Paying attention to the sound and the feel of the brakes, I believe kept this from being a more serious problem.


Originally Posted by CliffordK View Post
Keep on ENVE to get this resolved. Do they have 32 spoke wheels? Anything else suitable? Is this covered by warranty? Seems like a design issue more than a wear issue.
I did speak to ENVE, and the y encouraged me to file a warranty claim. which was a pleasant surprise given the age of the rims, and their use on a tandem.

As for design, ENVE did say that their current carbon wheels are designed to be more heat resistant than the old classic wheels, with changes in both the resin and the brake track design.

Unfortunately, ENVE no longer makes any deep sectioned road rims with more than 24 holes, pretty much putting them out of the tandem market for all but the smallest teams

Originally Posted by CliffordK View Post
I was going to suggest either discs or drums. Disc rotors, of course, come in different sizes. Can you get the biggest one available installed?

I suppose it is time to start experimenting with different calipers. TRP makes the hybrid mechanical/hydraulic which is worth considering. Upgrade to full hydro?
Drum is out of the question due to weight. As for the size of the disc, we're using a 203mm rotor which I think is big enough. Ironically, I have installed a TRP hybrid cable hydraulic caliper, which I planned to install before Hot Dogget, but didn't arrive in time. The TRP appears to have much more braking force.

Full hydraulic really isn't practical for us because 1) I'll run rim caliper brakes on the bike in all but the big mountains, and 2) we don't have a front disc fork (or a good option to retrofit one on our frame) so the front brake will always be cable.
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Old 07-18-19, 01:16 PM
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350 pounds of riders - plus the weight of the bike - with a 4 year old/20000 mile rim brake carbon front wheel.... Glad for you that this didn't end badly and I must say I admire your sense of adventure!

I think that you were on the right track by using a disc on the rear. But, the physics is such that the rear brake does not provide nearly as much braking power as the front, and a hydraulic disc brake is going to give you much more braking power than the mechanical disc you have.

I suggest that if you are going to ride carbon rims that you get yourself a nice set of hydraulic discs - either full hydro from the lever or cable-actuated hydro. And, make sure your front fork can handle the load and disc braking forces you are intending to apply.

Good luck!
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Old 07-18-19, 01:38 PM
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I thought ENVE specialized in wide tubular rims... I'm surprised they aren't doing heavier duty rims, although... perhaps your Tandem woes are part of the reason.

You can always resell whatever they send you and buy what will work.

I think ZIPP is heavy into the cyclocross scene. I'd think ENVE too... but there should be options out there.
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Old 07-19-19, 01:17 AM
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Fark!!! Just glad you're ok and the failure wasn't at 42m/hr. If Enve aren't able to make the 32 hole rims you need then perhaps Lightbicycle might be an option. They will do custom layups and hole drillings for about an extra $20 I think. I'd be swapping out the front fork for one that had disc brake mounts and using discs front and rear with TRP Hy/Rd brakes.

These youtube videos are worth watching about carbon rims


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Old 07-19-19, 04:29 AM
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@merlinextraligh: Thanks for sharing this story. And thanks God nothing serious happened.
Stories of fun & success are easy to share but those experiences are really valuable for everyone.

My thoughts on this are whether I would really like this high-tech race material on a tandem or not.
Since our setup was always rather a touring machine than a racer, I didn’t even think about carbon wheels.
On the contrary, for >200kg gross weight (overnight tour setup, we’re not even a heavy team) I felt (and feel) always safer
on our beefy 26” rims with cargo bike approval.

Carbon fiber is a fantastic material. Well designed it can bear lots of load in the desired direction.
But it is just not very forgiving for something like unwanted lateral forces or high temperatures.
With this warning shot I would really think about 36 Spokes, Aluminum and some good (hydraulic disc) brakes.
The rear brake on a tandem is not as disadvantaged as on a single bike. The load shift is not as dramatic (a “stoppie” on a tandem is hard to perform ).
Therefore a good rear brake makes definitly sense...
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Old 07-19-19, 05:34 AM
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Interesting report, thanks. A friend of a friend recently had a carbon rim failure on the Triple Bypass. There is a reason some well organized mountain rides will not permit them. Seems as if the popularity of discs will soon consign this issue to history.
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Old 07-19-19, 06:48 AM
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A few thoughts:

1) I don't think the age/mileage of the wheels had any effect on this. The brake tracks showed virtually no wear prior to this incident. The fact that we got 20,000 trouble free miles out of them indicates to me they were plenty strong, and well suited to our use, other than this heat issue.

2) I do think the TRP/Spyre hybrid disc brake will help. While more braking force comes from the front, as Lichtgrau points out, the weight distribution on a tandem lessens that effect. The Bengal brake we were using could not even come close to locking the rear wheel. The TRP can lock the rear, and more importantly, modulate just short of that.


3) Carbon fiber clinchers have gotten better in the more than 8 years since ENVE Classics were designed. The current popular recommendation for go fast tandem wheels appears to be Zipp 404 Firecrest rims with 28 spokes. (Calfee's current recommendation). According to Zipp they have never had a heat related failure on a 404 Firecrest.

4) Future setup: for most of our riding, other than in the mountains, we'll set the bike back up with rim brakes and Zipp 404's. The bike weighs 24lbs, and I don't want to add several pounds with discs front and back. For the occasional ride with big descents, I'll put the TRP disc on the back, and an older Zipp 808, with an aluminum brake track on the front.
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Old 07-19-19, 07:09 AM
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Originally Posted by merlinextraligh View Post
A few thoughts:

1) I don't think the age/mileage of the wheels had any effect on this. The brake tracks showed virtually no wear prior to this incident. The fact that we got 20,000 trouble free miles out of them indicates to me they were plenty strong, and well suited to our use, other than this heat issue.

2) I do think the TRP/Spyre hybrid disc brake will help. While more braking force comes from the front, as Lichtgrau points out, the weight distribution on a tandem lessens that effect. The Bengal brake we were using could not even come close to locking the rear wheel. The TRP can lock the rear, and more importantly, modulate just short of that.


3) Carbon fiber clinchers have gotten better in the more than 8 years since ENVE Classics were designed. The current popular recommendation for go fast tandem wheels appears to be Zipp 404 Firecrest rims with 28 spokes. (Calfee's current recommendation). According to Zipp they have never had a heat related failure on a 404 Firecrest.

4) Future setup: for most of our riding, other than in the mountains, we'll set the bike back up with rim brakes and Zipp 404's. The bike weighs 24lbs, and I don't want to add several pounds with discs front and back. For the occasional ride with big descents, I'll put the TRP disc on the back, and an older Zipp 808, with an aluminum brake track on the front.
Do the HyRd calipers automatically advance the pads?Don't know, just wondering out loud.

I wonder if part of your lack of braking power wasn't just because of rear-disc-only....but also because with 400 pounds of bike and riders and gear, you wore through the cable-pull caliper pads to where they needed manually advanced for wear.
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Old 07-19-19, 07:30 AM
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Originally Posted by Marcus_Ti View Post
Do the HyRd calipers automatically advance the pads?Don't know, just wondering out loud.
According to TRP, the hydraulic reservoir automatically adjusts for pad wear

Originally Posted by Marcus_Ti View Post
I wonder if part of your lack of braking power wasn't just because of rear-disc-only....but also because with 400 pounds of bike and riders and gear, you wore through the cable-pull caliper pads to where they needed manually advanced for wear.
I don't believe it was pad wear. The Bengal brake we have ( don't recall the model) just never has grabbed well. Adjusted as tight as possible, there's not enough cable travel to really crank them down. Given my concern about our brake setup, I adjusted the brake at the SAG stop at the top of the descent.


The TRP hybrid's actuation appears to multiply the force on the pads, compared to a pure cable setup, ameliorating the problem of limited cable pull
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Old 07-19-19, 02:33 PM
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Originally Posted by jlaw View Post
...and a hydraulic disc brake is going to give you much more braking power than the mechanical disc you have.
Evidence for that? Where does the additional "power" come from that hydraulics supposedly have? Not disputing that hydraulics do have some advantages over cables, just don't see where they have more power, is all. If they were drawing extra energy (power x time) from the airflow (like speed brakes on airplanes) or from the weight of the bike descending (like dynamic brakes on locomotives) I could see it. But the only source of power into any bicycle brake is from squeezing the levers.
This is not merely to be argumentative. The OP and his crew face design constraints on their ability to adopt hydraulic brakes. It is not helpful to suggest something that will not fit their bike unless there is clear evidence that they should abandon those design contraints and adopt hydraulics anyway. Besides, I don't think they were asking for suggestions, just very kindly and helpfully relating something bad that happened to them that thankfully was not a whole lot worse.

Really really glad you guys are OK!
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Old 07-19-19, 03:15 PM
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Originally Posted by merlinextraligh View Post
According to TRP, the hydraulic reservoir automatically adjusts for pad wear



I don't believe it was pad wear. The Bengal brake we have ( don't recall the model) just never has grabbed well. Adjusted as tight as possible, there's not enough cable travel to really crank them down. Given my concern about our brake setup, I adjusted the brake at the SAG stop at the top of the descent.


The TRP hybrid's actuation appears to multiply the force on the pads, compared to a pure cable setup, ameliorating the problem of limited cable pull
Yes TRPs advance the pad. Make sure you run them with compressionless brake housing only since the housing run is extra long. If you have strong hands and feel the lever pull is too long consider modifying the cable mount point
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Old 07-19-19, 03:26 PM
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Originally Posted by conspiratemus1 View Post
Evidence for that? Where does the additional "power" come from that hydraulics supposedly have? Not disputing that hydraulics do have some advantages over cables, just don't see where they have more power, is all. If they were drawing extra energy (power x time) from the airflow (like speed brakes on airplanes) or from the weight of the bike descending (like dynamic brakes on locomotives) I could see it. But the only source of power into any bicycle brake is from squeezing the levers.
This is not merely to be argumentative. The OP and his crew face design constraints on their ability to adopt hydraulic brakes. It is not helpful to suggest something that will not fit their bike unless there is clear evidence that they should abandon those design contraints and adopt hydraulics anyway. Besides, I don't think they were asking for suggestions, just very kindly and helpfully relating something bad that happened to them that thankfully was not a whole lot worse.

Really really glad you guys are OK!
The design of a hydraulic brake uses the properties of a non-compressible fluid to multiply the effort that the user applies with his fingers on the lever. This is why motor vehicles have brakes that use DOT fluid and a system that vastly multiplies the effort you exert stepping on the brake pedal. It would take a mile to stop a car that used a cable to connect the brake pedal to the calipers.

I have hydros on my downhill bike and TRP Spyre cable-actuated on a road bike - huge difference in braking power for a given input of effort.

Give them a try for yourself.

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Old 07-19-19, 04:14 PM
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In a job 20 years ago at a composite shop, we did strictly custom work for the military or aircraft industry. That work consisted of inlet ducts for the old U2 spy plane, then being used for photography purposes, Apache helicopter and some work for Boeing. Our shop got epoxy resin samples weekly that were tested for particular properties for our projects. This came to dozens of resins whose properties were then entered into a data base. Chemical engineers understand the resins at a molecular level and can taylor properties for specific purposes. My experience and that of the engineers is just as the Aussie in the video stated. Carbon composite can be very strong when carefully built but there is no way to tell in advance. In a shop environment every aspect of the process has to be monitored and tested. As a rudimentary example, has the resin/catalyst been accurately mixed and cured parts tested. How do we know?
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Old 07-19-19, 04:30 PM
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Sobering, isn't it? Having had the good fortune to blow a few tires off alu rims also while coming to a stop, we must salute our good sense! Way to go. Solution for alu rims turned out to be deep rims and a drum when touring in the mountains. 2 lbs. extra has not been a consideration for us when touring. I like your solution also. Our frame doesn't have the ability to mount a disk.
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Old 07-19-19, 05:49 PM
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Re: how hydraulic systems work I found the image shown below.

Let's say you pull N force on your brake lever causing the lever to move. This force is transmitted to the cross-sectional area of the fluid in the hydraulic brake cable (very small x-sectional area) thereby creating a pressure. This pressure is then transmitted by the non-compressible fluid to the much larger cross-sectional area of the brake caliper. Let's say the area of the brake caliper is 30 times the area of the brake cable. Therefore, 30N of effort is exerted on the caliper - a substantial increase. However, the distance the caliper moves as a result of this effort is much smaller than the distance you moved the brake lever.



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Old 07-19-19, 06:57 PM
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Originally Posted by merlinextraligh View Post
A few thoughts:

4) Future setup: for most of our riding, other than in the mountains, we'll set the bike back up with rim brakes and Zipp 404's. The bike weighs 24lbs, and I don't want to add several pounds with discs front and back. For the occasional ride with big descents, I'll put the TRP disc on the back, and an older Zipp 808, with an aluminum brake track on the front.
I'm not sure an 808 with an aluminum braking surface is going to be a lot better, as opposed to just opening up a slightly different failure mode. You are still going to be dumping an enormous amount of heat into an aluminum/carbon fiber bonded interface with no particular place for it to go. I guess you won't have the extra force of the tire pressure on the carbon hook bead hold the rim on, which is good, but you are more likely to blow the tire off the rim as the tire/rim interface heats up more because the aluminum transmit the heat better than the pure carbon clincher. And I would think the carbon section of an 808 is going to insulate the aluminum a fair amount compared to a pure aluminum rim that is exposed to the air for cooling. I think I'd be using the rear brake a lot. Or would pay a couple hundred gram weight penalty for a deeper aluminum rim that will shed the heat better.
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Old 07-20-19, 08:27 AM
  #24  
conspiratemus1
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Originally Posted by jlaw View Post
Re: how hydraulic systems work I found the image shown below.

Let's say you pull N force on your brake lever causing the lever to move. This force is transmitted to the cross-sectional area of the fluid in the hydraulic brake cable (very small x-sectional area) thereby creating a pressure. This pressure is then transmitted by the non-compressible fluid to the much larger cross-sectional area of the brake caliper. Let's say the area of the brake caliper is 30 times the area of the brake cable. Therefore, 30N of effort is exerted on the caliper - a substantial increase. However, the distance the caliper moves as a result of this effort is much smaller than the distance you moved the brake lever.



Your drawing and explanation confuses force with power. Power (rate of dissipation of kinetic energy of bike + riders into heat) is what determines how fast the bike will stop, regardless of how much force or distance you have to pull on the brake lever. I don't want to hijack this thread and won't say any more about this. Hydraulic brakes are not on the OP's menu and we should leave it at that.
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Old 07-20-19, 08:57 AM
  #25  
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Originally Posted by conspiratemus1 View Post
Your drawing and explanation confuses force with power. Power (rate of dissipation of kinetic energy of bike + riders into heat) is what determines how fast the bike will stop, regardless of how much force or distance you have to pull on the brake lever. I don't want to hijack this thread and won't say any more about this. Hydraulic brakes are not on the OP's menu and we should leave it at that.
You're correct on the semantics but in this case it appears the lack of braking power was due to insufficient mechanical advantage provided by the cable disc brake. Using a hydraulic setup allows one to exert maximum force and dissipate maximum power with one finger.

Cable brakes can also be designed with sufficient mechanical advantage but then they will have more lever travel and require more frequent adjustment.

If you're running discs I hope they're bigger than 160mm. Discs will likely get smoking hot going down a 9% hill.
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