what's flexing?

[vqdriver]

since i got a set of enve 3.4 wheels, i've noticed that the brakes rub in out of the saddle efforts, either sharp acceleration or up steep inclines. it's obvious now because the textured brake tracks on the rims make a distinct whine when the pads touch them. with my old al rims, this wasn't audible at all.
curious to know if it's the wheels that are flexing or if it's the frame. is there an easy way to find out? only other wheelset i have is the al wheels.

fwiw, it's not rubbing hard enough for me to feel like it's adding resistance, just enough to let me know it's happening. also, i have a good amount of clearance between rim and pad when open.

[m4rk540]

Pair an ultra stiff, deep profile carbon rim with a low spoke count as you find on almost all aero carbon wheels and the system will be prone to flexing. Essentially, the rim overwhelms the spokes.

[drewellison]

You get rub on the brakes because the rim are so stiff that sideways force on the rims from the road (rocking the bike or sprinting) translates to movement by the brakes. Think of the stiff rim pivoting sideways around the hub.

Aluminum rims are more flexible, so flex down by the road does not mean that the rim will be moved by the brakes. So less likely to rub.

I think there's more to it (spoke count, etc.) but that's how I understand it. After all, I read it on the internet so it must be true.

[BdaGhisallo]

What hubs and spokes do you have? The standard Enve builds can be flexy. Build a set with White T11 hubs and Sapim Race spokes and you will get a much stiffer rear wheel.

[m4rk540]

http://www.slowtwitch.com/Tech/Debunking_Wheel_Stiffness_3449.html

[vqdriver]

hubs are the carbon enve hubs. which i understood to be dt 240 but with carbon shells. my previous al wheels also roll on 240 hubs.

so the consensus is that it's the wheel. i was just wondering out loud if it were the frame flexing this whole time and i just wasn't aware of it due to the traditional smooth brake track on my previous wheels.

[m4rk540]

Which frame?

[54ny77]

https://media.giphy.com/media/K4nNX4ye7gHQc/giphy.gif

[rnhood]

The Slowtwitch article is a good one. Enve builds wheels, but it's not clear that they engineer or devolop wheels in the way Zipp and Mavic do. There may be something Wheelbuilder can do to mitigate the deflection but, the whether its worth it is another question. If it doesn't bother you, then just ride it.

[54ny77]

That's true. Zipp engineers their wheels to be swapped out for something better from another brand. :bike:


The Slowtwitch article is a good one. Enve builds wheels, but it's not clear that they engineer or devolop wheels in the way Zipp and Mavic do. There may be something Wheelbuilder can do to mitigate the deflection but, the whether its worth it is another question. If it doesn't bother you, then just ride it.

[vqdriver]

Which frame?

time vx edge from 06

[rnhood]

Well, none of them are perfect. Zipp has certainly had their hub issues. But their rims are really good, and I have not seen delamination on a Zipp. Regardless, its best to ride and enjoy. I use aluminum (actually scandium) rims and am very happy - whether they are near perfect or far from it. They don't fail and braking is excellent. I need durability, not fashion.

[saab2000]

time vx edge from 06

I'm guessing it's the frame that's flexing. I ride ENVE wheels and I had a set of 3.4s. They were fine but I sold them, moving back to aluminum clinchers.

Anyway, I rode them mostly with a Look 585 of similar vintage. They were stiff wheels and I think overwhelm the frame.

I ride a Giant TCR Advanced SL as well and it's a really stiff frame. In that frame I use a set of ENVE 45 tubulars. No flex anywhere.

I'm not an engineer but I'd think it's the frame, not the wheels, that's flexing.

[elliott]

If you are using the old style Enve skewers I would swap them out. Enve just came out with a mavic style skewer that has much better clamping force.

[vqdriver]

hrm. hadn't considered the skewers. i'm using a set of salsa flip offs.

[saab2000]

hrm. hadn't considered the skewers. i'm using a set of salsa flip offs.

Definitely consider better skewers. I run either Shimano Dura Ace or Campagnolo internal cam skewers on all my bikes. They definitely clamp best and being steel, are strong and stiff.

[vqdriver]

i've got a set of campys rattling around in the parts bin. i'll give em a go

[Satellite]

As others have already said above. ENVE Carbon rims are stiff. The stiffness actually translates from the ground up through the rim to the top where the brakes are located. It causes brake rub. When the rim/wheel has more flex it deforms at the ground and begins to straighten back out before it can be translated to brake side of the wheel. Like others have said NOT too much to worry about. I doubt very seriously it is robbing you of any watts. Just enough to be annoying and make you think if you weren't hearing the rubbing you would be going a lot faster. Just to be sure you can check the toe of your brake pads and if they are really toed in adjust them until they are about 1-2mm. The front of the pad should just ever so slightly be toed inward to make contact to the rim before the pad is in full contact for the rim.

Do a search on the forum you can spend days reading about why this is the case. Ergott and 11.4 have written Doctorate Dissertations on the subject.

[dddd]

The spoke count, as well as the spoke bracing angle, play huge in terms of a wheel rim moving out of plane with the hub.
I remember building wheels with heavy, wide, 36h, double-walled Mavic Module4 rims. These rims were notably stiff, yet the wheel touched the brake pads more than with the previous single-walled rims.
The spoke-bracing angle wasn't great, since the spokes were offset to each side of the rim's centerline along the radius of the rim's outer wall.
Can't say that I felt more flex at the contact patch, and the wheels proved 100% durable for off-roading and a few CX races.
Finding decent, wide rims was almost impossible 20 years ago!

[charliedid]

open the brakes a little

[ptourkin]

I have two sets of Enves that I use on my Exogrid. My main set are 2.2s on Enve hubs. I've had multiple problems with these hubs (broken spokes, cassette body bearings) but not brake rub on hard efforts.

My tubulars are 3.4s on DT 180s. I do get some kind of flex rub on hard out of saddle efforts.

I'm using Enve skewers on both and both have DT Swiss spokes.

[m4rk540]

I have two sets of Enves that I use on my Exogrid. My main set are 2.2s on Enve hubs. I've had multiple problems with these hubs (broken spokes, cassette body bearings) but not brake rub on hard efforts.

My tubulars are 3.4s on DT 180s. I do get some kind of flex rub on hard out of saddle efforts.

I'm using Enve skewers on both and both have DT Swiss spokes.

Enve carbon hubs are notoriously bad. Every set I've seen has had manufacturing issues, mainly wobbles. Essentially, they can't get the tolerances as precise as aluminum since the hubs expand once taken out of the molds.

[ptourkin]

Enve carbon hubs are notoriously bad. Every set I've seen has had manufacturing issues, mainly wobbles. Essentially, they can't get the tolerances as precise as aluminum since the hubs expand once taken out of the molds.

Good to know. I usually weigh less than 140 and broke three spokes this year. Two fronts, which are ride-ending on a 20 wheel. Also, cassette body bearings completely slopped out, leaving everything wobbly. My builder will probably cut them out and rebuild with 180s.

[BdaGhisallo]

Good to know. I usually weigh less than 140 and broke three spokes this year. Two fronts, which are ride-ending on a 20 wheel. Also, cassette body bearings completely slopped out, leaving everything wobbly. My builder will probably cut them out and rebuild with 180s.

Give White T11 hubs a try. TI cassette body and better flange geometry. DT 180 hubs are very overpriced for what you get.

[sandyrs]

https://www.youtube.com/watch?v=8Wew6ljPbrM

[Keith A]

https://www.youtube.com/watch?v=8Wew6ljPbrMWhat am I missing here? Was this necessary?

[ptourkin]

What am I missing here? Was this necessary?

Maybe not but it's stuck in my head now :hello:

[sandyrs]

What am I missing here? Was this necessary?

It's a famous song with a famous lyric about "flexing" and the first thing that came to mind when I saw the thread title...

[Keith A]

It's a famous song with a famous lyric about "flexing" and the first thing that came to mind when I saw the thread title...Sorry, I had the volume turned off and didn't hear the song...but I did see the image on the YouTube video. I had a complaint about this post, which is why I responded.

[sandyrs]

Sorry, I had the volume turned off and didn't hear the song...but I did see the image on the YouTube video. I had a complaint about this post, which is why I responded.

Ah, got it. Feel free to censor/delete the post, it's certainly not a shining contribution to the discussion of wheel stiffness at hand, just being silly.

[Bentley]

What am I missing here? Was this necessary?

Agree totally, I went to the link, I am not offended easily, but this really was unnecessary

[vqdriver]

well that's not great to hear.
are we talking about these hubs?

https://i.stack.imgur.com/0bM9r.png

Enve carbon hubs are notoriously bad. Every set I've seen has had manufacturing issues, mainly wobbles. Essentially, they can't get the tolerances as precise as aluminum since the hubs expand once taken out of the molds.

[TEMPLE]

I'll throw an observation into the ring. I had a set of wheels (Shimano Ultegra) that were fine for the first 700-800k, then the rim on the rear wheel started rubbing the brake pads when I would put down serious Temple-power. Whatever...the world doesn't get to see that kind of display very often. However, it progressed until it would happen under medium Temple power, so it was then officially a problem. Anyways, since the wheels didn't do that when new, it seemed like they were the obvious source (despite being on a noodle-y Lynskey frame). So, I hauled out the spoke tension meter and tightened the spokes (a few were quite loose, and most were lower than from-the-factory tension) and trued the rear wheel. Problem solved!

[ptourkin]

well that's not great to hear.
are we talking about these hubs?

https://i.stack.imgur.com/0bM9r.png

Yes. Very expensive too. Mine were not factory built but by a builder I trust very much. After a couple front breaks, we switched from 2X to radial. He also made some adjustment to the length. We thought the issue was probably that thick flange but the above report about QC issues also makes sense.

[saab2000]

I'll throw an observation into the ring. I had a set of wheels (Shimano Ultegra) that were fine for the first 700-800k, then the rim on the rear wheel started rubbing the brake pads when I would put down serious Temple-power. Whatever...the world doesn't get to see that kind of display very often. However, it progressed until it would happen under medium Temple power, so it was then officially a problem. Anyways, since the wheels didn't do that when new, it seemed like they were the obvious source (despite being on a noodle-y Lynskey frame). So, I hauled out the spoke tension meter and tightened the spokes (a few were quite loose, and most were lower than from-the-factory tension) and trued the rear wheel. Problem solved!

My wheels normally don't start to show any signs of de-tensioning until I have at least a million K. I'm surprised yours loosened up after only 700-800k. :rolleyes:

[Satellite]

My wheels normally don't start to show any signs of de-tensioning until I have at least a million K. I'm surprised yours loosened up after only 700-800k. :rolleyes:


∆∆ LMAO :butt:

[charliedid]

Ah, got it. Feel free to censor/delete the post, it's certainly not a shining contribution to the discussion of wheel stiffness at hand, just being silly.

shining or otherwise it sure made me laugh

[dustyrider]

It's a famous song with a famous lyric about "flexing" and the first thing that came to mind when I saw the thread title...

I'm not sure whether or not Trinidad James appreciates just how much I laughed while watching his all gold everything video on YouTube. For some reason the whole thing reminds me of an In Living Color sketch and just had me in stitches.
Pleas don't ruin the buzz and tell me it isn't meant to be satirical; ignorance is bliss!

Oh, and I don't know anything about carbon rims...but I will know what "straight flexing" is if I ever hear it again. I hope it makes me laugh just as hard, thanks.

[TEMPLE]

∆∆ LMAO :butt:

I don't get the joke! Fill me in.

[dsillito]

I don't get the joke! Fill me in.

Wow. You have been waiting in suspense for quite some time on this joke. Miracle I came across this in my wanderings.

Seems to be a "comical" (cough) misinterpretation of the letter "k". As a canuck, you were using it as a short form of km (as in "how many "k's" are we riding today?), whereas the joke was based on it being an abbreviation for "thousand" of kilometres. One of those classic "metric system" gags we all got a kick out of back in the '80s.

So one willing to misunderstand for comedic effect would suggest you had a wheel problem after 700-800 thousand kilometres, rather than 700-800 km.

I guess you had to be there...

[MaraudingWalrus]

Link to the song is every bit as relevant and as much a contribution to the discussion as the gif of Homer Simpson flexing in front of a mirror....which is to say an actually fairly reasonable, by internet comment section standards, response to the question "what's flexing?" and a fairly funny one at that.


But the issue of wheel flex/frame flex is one that's difficult to get anyone to a satisfactory conclusion. The number of times I've had the discussion with the same couple guys from a local race team who are adamant that their 808s or 70mm deep reynolds aren't "stiff enough" for the watts they throw down on their training ride for the Cat3 racing season..but the rub doesn't happen on their shallow aluminum wheel.

Impossible to convince them that it may actually be a stiffer wheel which might be why it's rubbing in certain circumstances - that the frame may be flexing into the wheel.

That slowtwitch thread is a gem, have sent many a people to it.

[C40_guy]

Maybe not but it's stuck in my head now :hello:

No, that's another thread... :)

[C40_guy]

That's true. Zipp engineers their wheels to be swapped out for something better from another brand. :bike:

In 45 years of riding, i've broken a grand total of two bicycle spokes, both on the drive side of a Zipp 303 rear wheel.

The second time, the bike was leaning against something and I heard a "plink."

That was it for those wheels!

[benb]

I had a set of deep-is Velomax (later Easton) alloy wheels that did this above probably 400w I'd guess? I thought I saw the OP say 140lbs, I'm quite a bit bigger. Just guessing at the power as I'd notice it climbing out of the saddle on really steep stuff and/or sprinting.

It annoyed the hell out of me, that was a $1000 wheel set or so back in 2005. I took them back and they reworked the tension, the factory build was not to spec.. they were basically fine after that and I rode them till about 2011 when the rear rim cracked, probably cause they should have had more spokes.

For all the complaints about really expensive carbon wheels I don't think I'd buy without trying with problems like this.

It doesn't really matter if the wheel is not stiff enough in total, or it's flexing the frame, or whatever.. you're paying a lot of money and it's a very annoying quality in a wheel. For the amount of weight weenism & spending money to try and get faster going on with $2000+ carbon wheel sets the rubbing of brakes at high power does not seem acceptable even if it's only costing you some single digit power #. Same thing with braking that is even 1% worse than a top end alloy rim IMO too, but everyone has a different opinion on that. Poor braking for me I'd say it can eat up a ton of the gains of the fancy wheel set.

I'm way skeptical of the wheels flexing the frame that much anyway... especially if you're talking a modern carbon super bike frame.

I actually had a way more pedestrian set of wheels detension too.. Mavix CXP or something like that laced to Ultegra hubs, with plenty of spokes. They actually didn't flex and rub the brakes like the low spoke count wheels even when they were practically falling apart though.

[beeatnik]

That slowtwitch thread is a gem, have sent many a people to it.

IIRC, that paper attributes flexing to the interplay between a super stiff deep carbon wheel and limited number spokes. Essentially, the rim overpowers the spokes.

[bikinchris]

IIRC, that paper attributes flexing to the interplay between a super stiff deep carbon wheel and limited number spokes. Essentially, the rim overpowers the spokes.

Exactly. Everyone on this thread is missing the real reason for the problem. Low spoke count. 18 spokes CANNOT do the job of 32, much less 14 or 12 with really bad spoke angles from the hub to the rim.

Might I suggest a fix? Disc brakes.

[duff_duffy]

Bump for the link. Everyone’s gonna be straight flexin on there next ride.

#straightflexin

[benb]

That slowtwitch article is great...

Fascinating to see the Pros complain about this and get special versions of the wheels with more spokes but sexiness & weekend warriors mean the stock versions get fewer spokes and end up with brake rub. :rolleyes: It sure sounds like the guys at the point end of the sport think the brake rubbing slows you down.

The weekend warriors who can't overpower the stock version that doesn't have enough spokes, are they fast enough to be getting a benefit from the aero effects of the wheel?

No matter how strong/weak or heavy/light you are we all get to put up with the negative effects of deep rims in crosswinds.

I guess I'm happy just riding a nicer set of Ksyriums.. I've had 2 sets over the past 20 years.. both felt light enough (~1500g), fast enough, etc.. and I can't ever get them to rub the brakes. The $1000-1500 savings over a carbon setup can go a long way for something else.