5/16/14 4:08 PM

Are radial non drive side wheels just like this, or was it the 24 spoke rear with a fat ars? Both I am thinking, all three actually.

I tossed the Roubaix back into a running bike with multi day rides in mind. 10 Speed Ultegra triple, the best triple I have ridden ever. As in it behaves like a double basically. It takes you forgetting to get in the wrong ring, no double drops from the big ring. Only did that once today, forgetting not a double drop. ;) Trimming positions decisive.

Anyway, as to the spongy comment, next to the Scott the Roubaix is a little spongy, everything is probably. For yesterday's ride I grabbed a barely used Easton wheelset after I got the groupo setup and chain on. Easton on Velomax hubs, I guess these where soon after Easton bought Velomax?

24 spoke rear 2x drive radial non drive. 4 days in a row riding, and I was sucking eggs a bit at times. Attributed it to my lack of legs, now not too sure. Putting watts into the wheels was, just spongy. I did not remember the Roubaix feeling like this that much.

So today, same bike, 5th day, even more spirited ride with some strong folks. But my 32x A23 rim in the back. The pedal pushing sponginess very slightly there, so frame I guess being sportiff. But what a difference from the 24 spoke Easton. I should have been suking eggs worse 5th day a harder ride, I figure... Was at the end of the ride. ;)


The guy that fell on me last Friday apparently broke a rib. He was riding today but not up front like usual. Suks all around, at least he did not bust me falling on me. just some minor road rash on my left calf it turns out.

5/17/14 8:10 AM

...or is Sparky's post really difficult to understand?

Regardless, I think there's a question there regarding half-radial rear wheels. No, half-radial does not make a wheel "spongy". If a wheel is properly tensioned, it should transfer drive torque efficiently and I can honestly say that I've never felt sponginess or windup in a rear wheel. I've ridden everything from 24 to 42 spokes, most of which were half-radial, but also a lot of 36 spoke 3x both sides. I've also ridden a reasonable variety of rims from ultra-light box-section tubulars to 50mm carbons.

I suggest that the difference in feel is much more likely to be due to the tires and/or tire pressure than to the wheel lacing or the spoke count.

5/17/14 8:50 AM

Sorry about the format of the message.

Same tires and pressures. I know the difference was no in my head for sure. The 32 spoke 3x laced wheel did not exhibit said sponginess when watts put in. The 24 spoke rear feel with the radial non drive was noticeable and energy sucking.

5/17/14 11:32 AM

or other geometric/physical differences between the 2 wheels.

5/17/14 6:28 PM

If this is a case of drivetrain wind-up, I can say that I've felt that many times, usually it is one way I can notice that I'm not in the big ring, where chain/chainstay/axle elasticity is exponentially lower than caused by reduced chain tension alone.

5/17/14 7:22 PM

Any time the "flex causes energy loss" question is raised, I have to ask "So what were the results when you put a watch on it?" I still remember the first time I rode a Litespeed - it felt flexy compared to my steel bike. But in a time trial, it was just as fast.

In order for flex to be causing any energy loss, that energy has to be going somewhere. If the frame is not heating up, if the wheels are not heating up, if the time trial time doesn't change, then all we are talking about is a perceived loss. Lots of people think stiffer frames, handlebars, stems, wheels, cranks, etc. are faster just like they think that tires are faster when pumped up harder. Feels faster. Must be faster. But the data disagree.

5/17/14 8:46 PM

Put that wheel on the scott for the heck of it, just went up the hill here in the sub-div. Definately feel the buffer of it, for what ever reason it is spongy.

Don't care enough to to any time comparisons really. ;)

5/17/14 9:13 PM

I'd say it's the 24H spoke count, not the NDS radial. I've had NDS radial on three wheels, none were particularly flexy/spongey.

5/17/14 11:32 PM

I suspected the 24 spoke wheel as well, since the reduction of spoke weight and aero loss is taken to maximum level at some expense to flexing, per the priority of allowing an average racing cyclist to realize the maximum overall performance.
Now if this were a HED Belgium rim, which is particularly wide and noticeably stiff laterally, 24 spokes would be more optimal overall for Bob.

As far as "energy loss" this is a term that gets tossed around, but I think can be misleading.

I think it can be more of a case of "energy not delivered", when flex prevents muscles from meeting full resistance during their contraction, the brain may not synchronize the contraction optimally with the motion, resulting in an effectively later, less-productive pedal stroke, just as if a spark-ignition engine had delayed ignition timing relative to the position of the crankshaft and piston.

What makes it more difficult for the rider's nervous system to adapt to bicycle flex is the fact that with increased effort, the flex increases further, thus further distorting the timing of an optimal muscle contraction, and thus forcing the rider to push the pedal earlier and harder near the top of the pedal stroke in order to pre-load the "spring" that is the flexing bicycle.
It seems that some famous riders have adapted to riding flexible bikes, likely by initiating pedal force earlier, but it's hard to distinguish their genetics and raw talent from this presumed high degree of pedal dynamics adaptation.
Perhaps their softer bikes may have even compensated for the entire reduction in maximum power delivery by sparing them from the fatigue of a harsh ride.

I agree and/or assume that pedaling energy actually imparted into a flexing bicycle is for the most part fully recovered, but I don't think that a flexing bicycle can be anything but bad for power output when effort/force levels are at their highest.

I mentioned drivetrain flex as being exponential to gear reduction, because with say a 1-tooth or 2% reduction in chainring size, not only does the chain tension increase by about 2%, but the resulting 2% increase in chain/chainstay/axle flex is exaggerated by an additional 2% increase in pedal movement due to the 2% smaller chainring rotating 2% further for every increment of actual chain stretch.

As an integral of a full 10% reduction in chainring size, the resulting pedal movement from chain/chainstay/axle flex is actually more like a 23% increase.
And for the common switch from a 39t to a 34t chainring, this 12.8% decrease in sprocket size results in a 31.5% increase in chain/chainstay/axle flex movement felt at the pedal!

5/18/14 11:09 AM

My dura ace scandium wheels conversely, rear is radial drive side and 2x non drive and stiff in all ways.

5/18/14 4:56 PM

Shimano's engineering power, optimized structure from hub to rim.

I don't see the spoke cross pattern having much affect on rim support, but would affect the torsional windup stiffness of the hub I suppose.

5/19/14 5:27 AM

I'll go on record as stating that nobody can feel windup in a wheel. No matter how hard one pedals, the elasticity in the spokes is going to amount to a tiny fraction of a millimeter. Torque is distributed among all of the pulling spokes in a wheel and there's no one who can generate enough torque to be able to feel the minuscule amount of windup that occurs. Again, the tires will flex much more than the wheel ever could. Crank arms flex, the chain stretches, the cassette and freehub twist and obviously the frame flexes, but that's not "windup". Lateral flex or relative softness in the load affected zone in a wheel is not windup, either.

5/19/14 7:06 PM

And beyond the fact that no-one can feel wheel windup, Jan Hein (Bicycle Quarterly) has shown that a certain amount of flex is actually faster when climbing. We have this "stiffer is better" default but it is most likely not true. Again, put a stopwatch on it to prove a claim.

5/19/14 7:57 PM

I really did not make any claims of faster/slower, did I.
Only the effect on me. And being the following day I was more tired and had a lot less of this feel, to me it has to be those wheels. Well the rear.

As far as timing it, I am not even using a computer on my bikes these days. Strava kinda cured me. So that is just how I felt pretty much on those days with and without those wheels. The only climbing was when I stuck them on the Scott and went up the hill here in the subdivision, and one hill on that ride the first of the two days really.

5/19/14 8:13 PM

I should add, I may have been doing the wrong thing by pushing harder when I felt the sponge and cooked my legs. But I was good the next day, and I tend not to recover too fast. I actually used the little ring on the triple Thurs twice, but not on Friday FWIW.

I totally get the perception thing, just think it is that wheel...

5/19/14 8:13 PM

Without a doubt, there are differences in torsional stiffness of different wheels, going from normal 32 cross-3 spoking to just 20 or 24 spokes laced radial with 2-cross on only one side.
But no one here is saying that this by itself can be felt by a rider, only that some wheels, in total, feel flexy compared to others.
And, if the windup part can be felt by the rider, then this might likely be only in the lowest gears, on a bike that was otherwise stiff and which used relatively large chainrings (since chain tension caused by smaller chainrings introduces it's own flexibility to the drivetrain, "ahead" or "upstream" of the spoke flanges).

5/19/14 8:30 PM

The part about Jan Heine's testing is interesting to me, having read his test reports and not found anything to disagree about at the time.

Could it be that the whole flex-from-pedaling issue only becomes problematic when higher pedaling forces are involved, either from stronger/heavier riders and/or shorter, more-intense efforts?
Could it even be that, since the bike's speed varies more with each pedaling stroke while climbing (in lower gears), that some total amount of "windup" flex, including from lateral flex, allows the rider's muscles to "ease" into each pedal stroke with an easier, later start to the delivery of force?
Seems like this might spare the rider's legs when the bike's speed is surging with each pedal stroke (as it very noticeably does in the lower gears), but again I don't see this being beneficial to a rider's maximum (sprinting) power.

5/20/14 5:30 AM

...when it's severe enough to affect shifting or the rider's ability to keep the bike pointed where he wants it to go. Excessive flex can also make a bike feel inefficient and/or uncomfortable, even if it doesn't actually affect performance. A psychological disadvantage can be just as detrimental as a physical one. I can't say that I'm any faster on my stiffer carbon bikes than I was on my more flexible Ti bikes, but I enjoy them more because they feel more efficient.

5/20/14 2:06 PM

I have to say I feel a boost in confidence when I attack an all-out, 10 or 15-minute set of switchbacks on my Orbea, the bike telling me it's fully up to my hardest effort. The Orca is plenty stiff, no question.
The fact that it's light does help though, plus it has lots of close gear ratios controlled by STI.
The Ti bikes pay back though when the road surface deteriorates, so riding the flexier bikes like my PX10 is still fine for my strength levels.
At my weight, it's hard to imagine frame flex ever being an issue, not that I can't feel the difference, and different bikes produce different types of psychological boosts for all kinds of reasons. I may ride faster pretending that I'm Bernard Thevenet on my PX10.;-)

5/20/14 2:08 PM

"I may ride faster pretending that I'm Bernard Thevenet on my PX10."

Or at least think you do. ;)

5/20/14 7:02 PM

And let's not forget the tests that MAVIC did where they build wheels with significantly different stiffness characteristics and did blind tests with riders. Riders could not tell the difference between stiff and flexy wheels.

5/21/14 6:01 AM

Do you have a link to the Mavic tests?

5/21/14 7:04 PM

The MAVIC tests were reported in Bicycling or Velo News many years ago as part of an article about the company. Whether they ever "published" it is anyone's guess. I'll leave to you and Google to see what you can find.