Alloy wheels and flex?

[Xrslug]

I recently picked up a set of HED Ardennes RA Black wheels from a member here — very happy with them but did have a question about wheel flex. On my first ride on them when sprinting out of the saddle, I noticed the distinct “whir” sound of the brake pads rubbing on the textured brake track of the rims for a moment on each pedal stroke.

I usually like my brake pads set pretty close to the rims, but I opened them up and also switched from the light weight ti skewers I was using to beefier Dura Ace 9100 skewers. I can still hear a bit of brake rub when pedaling out of the saddle with this new set up. I’m big for a cyclist but not gigantic — 6’ 2” and 195 pounds or so all kitted up and I guess I’m fairly powerful but nothing exceptional given my weight (peak measured power = 1200 watts).

Curious to hear if others with the Ardennes have also seen a bit of wheel flex. I’m wondering if this has been happening on all my alloy wheel sets and I just never noticed because there isn’t that distinct sound when the brake pads rub the rims.

[Black Dog]

What is the spoke count of the wheels? All else being equal lower spoke counts will produce more flex than higher spoke counts.

[Baron Blubba]

I have the same wheels on my Ritchey Logic and have not experienced that at all. I’m a lot lighter than you, but 190 isn’t exactly heavy weight. Unless you are doing monster effort 1000w sprints, there’s no way you should be experiencing brake rub with the brakes open (and even then, doubtful).
Overall, transformatively great wheels, I’m very very happy with them.

[hokoman]

What frame are these wheels on?

[Xrslug]

Thanks for the responses. In answer to questions, this is a steel frame, 1x oversize tubing (1 1/4 dt, 1 1/8 tt). Frame doesn’t feel noodley at all to me, but certainly has more flex than a carbon race frame. Spoke count is 20/24 Sapim CX Ray. Light-ish wheels but these are “all road” sturdy, wide wheels.
I didn’t open the calipers up completely but adjusted to give more room to the rim. When I sprint I do put out over 1,000 watts, but that’s not crazy power output for 190+ pounds. I have a feeling the answer is I need to lose 15 pounds . And also experiment with how much room I can leave between the pads and rim.

[robertbb]

20/24 is likely the issue.

I can’s see any good reason to go less than 24/28 for any rider or rim brake build. Like, ever.

What problem do ppl have against spokes anyway? 20 grams and a watt of drag? C’mon maaaaaan

[Peter P.]

Delete duplicate post.

[Peter P.]

I'm inclined to say the spoke count is too low.

But you can't change that.

Have you checked the spoke tension-it could be low.

What's the spoke count on the wheels that don't exhibit rub?

[Mark McM]

It should be noted here that HED used to sell their wheels in a "Clydesdale" version for larger riders, with 4 extra spokes per wheel (24/28 instead of 20/24).

I suspect that it is a combination of two things already meantioned - that there is extra flex due to the lower spoke count, and that it is probably happening to some extent to your other wheels but the textured finish on the HED rims makes it more noticeable.

You can't change the spoke count your wheels of course, but the wheel could be made stiffer with thicker spokes. HED uses Sapim CX-Ray spokes, which are very thin (0.9mm x 2.2mm). Replacing the spokes with something like Sapim CX-Sprint spokes (1.25 x 2.25mm) would increase the lateral stiffness a meaningful amount. (Note: CX-Sprint spokes, and the equivalent DT Aero Comp spokes, still have a bladed profile for aerodynamics.)

[Xrslug]

Thanks, Mark — that’s helpful. I really like the width of the Ardennes rim and the braking with the textured surface. I haven’t noticed rubbing in the past with Ritchey Classic wheels (also fairly light alloy wheels with 20/24 spoke count, DT Competition spokes) or Roval SLX 24 wheels (20/24, DT Comp Race spokes). But I suspect unless the CX Ray spokes on the HED wheels are noticeably flexier than the DT Comp spokes, these three wheels are so similar in spec that it seems likely I was getting flex / brake rub in the Ritchey and Roval wheels and just didn’t hear it. I still have the Roval wheels so may try to experiment with them and see if I can notice any rubbing. And lose some weight!

[GregL]

So, adding up all the discussion in this thread: 195 lb. rider + 1200W peak power + fairly shallow height rims + 20/24 CX-Ray spokes + steel frame = rim hitting brake pads when sprinting out of the saddle. Makes perfect sense to me. Mark McM nailed it: more and thicker spokes are the answer.

For comparison, I have a rear wheel with a Kinlin XR-31T asymmetrical rim (deeper, likely stiffer section) and 24 CX-Sprint spokes (thicker spokes). It’s laced 2X on both sides. The best peak power I recall this year was 1100W. Running this wheel on my Cannondale CAAD9/10/13 (likely stiffer chain/seatstays than a steel frame) I’ve never rubbed the brake pads.

Greg

[dgauthier]

Yes, if you want solid control and no brake rub, you want to be 28 front/32 rear minimum. 32/32 will feel better on corners. (I will never get below 193, so those are my own rules.)

As others have said, this isn't an Ardennes thing, it's a wheel build thing. 20/24 won't be a huge problem, but you'll have to accept a little brake rub, and a little squishiness.

[Amateroy]

Originally Posted by robertbb

20/24 is likely the issue.

I can’s see any good reason to go less than 24/28 for any rider or rim brake build. Like, ever.

What problem do ppl have against spokes anyway? 20 grams and a watt of drag? C’mon maaaaaan

You may be right though!

[jm714]

I’m 6’5” 210. Ive never been able to ride a 24 spoke rear wheel regardless of it being alloy or carbon. They have rubbed the brake pads when I stood up to pedal. It goes away when I up the spoke count to 28.

[Mark McM]

Originally Posted by Xrslug

Thanks, Mark — that’s helpful. I really like the width of the Ardennes rim and the braking with the textured surface. I haven’t noticed rubbing in the past with Ritchey Classic wheels (also fairly light alloy wheels with 20/24 spoke count, DT Competition spokes) or Roval SLX 24 wheels (20/24, DT Comp Race spokes). But I suspect unless the CX Ray spokes on the HED wheels are noticeably flexier than the DT Comp spokes, these three wheels are so similar in spec that it seems likely I was getting flex / brake rub in the Ritchey and Roval wheels and just didn’t hear it. I still have the Roval wheels so may try to experiment with them and see if I can notice any rubbing. And lose some weight!

Wheel flex is due to a combination of rim stiffness, sp/oke number and thickness,and even hub axle flex plays a part. But as far as the contribution of the spokes, the thinner the spokes, the more flex the wheel will have.

That being said, on an individual spoke basis, DT Competition spokes (1.8mm center section) will be about 40% stiffer than a Sapim CX-Ray spoke, and DT Competition Race spokes (1.6mm center section) will be about 15% stiffer than a Sapim CX-Ray spoke. Sapim CX-Sprint spokes will have a similar stiffness as DT Competition spoikes (about 40% more than Sapim CX-Rays). That's not to say that using spokes that are individually 40% stiffer will make the entire wheel a full 40% stiffer, but the wheel will be meaningfully stiffer with the thicker spokes.