Wheel characteristics?

[edgerat]

I have seen comments about certain wheels being fast and others about wheels that spin up fast. Aside from hub engagement what makes for a fast week? Based on the comments i have seen it isn’t purely about aerodynamics.

What about stiffness of a wheel set? Lightweight seem to be the stiffest wheels out there, is being stiff good, bad, other? My only fancier wheels are DuraAce C50s and some Alpinist CLX I. have a build coming and trying to sort out the wheels.

Isaac

[Peter P.]

"Fast" wheels are those the spin up to speed quickly. It's a function of their polar moment of inertia. Which means where the weight on the wheel is located acts like a lever arm. The farther away from the hub the weight is located, the more energy is required to bring a wheel up to speed. Once at speed, things don't matter as much.

Therefore, light rims, tires, and tubes matter more than lightweight hubs.

Stiffness-obviously you don't want a wheel to flex when leaning into a curve. Think more in terms of strength rather than flex. A spoked wheel is very strong in resisting pedaling forces, called torque. Think about reefing on a socket wrench. The longer the handle, the more torque is applied. But leaning into a curve the rim can flex laterally. This is affected by the tension on the spokes, as well as the width of the hub flanges, which you can't do anything about. Bladed spokes, being thinner in the left to right direction, can flex more when a bike is leaned. Round spokes offer the best compromise in lateral resistance to flex and strength against pedaling forces.

You don't build flex into the wheels, or build them to provide a comfortable ride except for tire and air pressure choices. Any differences in feel between two different height rim walls would be the way they transmit vibration.

There's definitely more to wheels than aerodynamics and I feel aero is over-rated.

[Hilltopperny]

I tend to like a stiff wheel with a fast engagement hub. Aero benefits are mostly seen at higher speeds although the newer crop of aero wheels are light and wider. I even have a set of i9 65s I use on my gravel bike sometimes. Mated to a nice set of tires at the right pressures any good modern carbon wheel should spin up easily with a good hub. Lots of good stuff out there!

[martl]

put our bike on a workstand or similar, so that the rear wheel can spin freely. Spin it as fast as you can. Then stop it by pressing your thumb to the tire. The amount of warmth you feel in your thumb - that is the energy required to spin that wheel up. (hint: it ain't much)

[saab2000]

The best feeling wheels I’ve ever had were Campagnolo Nucleon tubulars.

I am no expert but these wheels, when examined closely, were engineered in a way that likely optimized everything. The rims were offset. The spoke pattern wasn’t just a 2x or 3x. The cassette side of the hub was high flange and how the spokes were anchored into the hub was cool. Hard to describe but clearly in a way that was well conceived. The spoke nipples were nuts accessed through the rim, with washers IIRC.

After time I started to break spokes and they weren’t seemingly easy to find at the time and I moved off of them. But they had a lively feel to them that makes at certain that if I buy a Campagnolo group again I’d likely also buy their wheels again.

[oldpotatoe]

Originally Posted by edgerat

I have seen comments about certain wheels being fast and others about wheels that spin up fast. Aside from hub engagement what makes for a fast week? Based on the comments i have seen it isn’t purely about aerodynamics.

What about stiffness of a wheel set? Lightweight seem to be the stiffest wheels out there, is being stiff good, bad, other? My only fancier wheels are DuraAce C50s and some Alpinist CLX I. have a build coming and trying to sort out the wheels.

Isaac

Most wheels that 'feel' fast feel that way because they are stiff. Weight at the rim, so-called 'flywheel effect' is mostly lost in the noise. Vastly overplayed. Yes, the 'effect' is there but the differences in 50-100 grams really means not much.

Tires, their construction, materials, PSI make a MUCH bigger difference in 'feel' than the weight of components at or on the rim.

[tellyho]

I do think I only notice the difference between really heavy and light. In the MTB world, I can tell the difference between the feel of carbon rim and aluminum but I'm not sure I could tell on smaller tires.

[Mark McM]

Originally Posted by martl

put our bike on a workstand or similar, so that the rear wheel can spin freely. Spin it as fast as you can. Then stop it by pressing your thumb to the tire. The amount of warmth you feel in your thumb - that is the energy required to spin that wheel up. (hint: it ain't much)

As above, it takes little energy to spin up a wheel when it is off the ground in a work stand. But when actually riding, unless the tires are slipping the wheels can't spin up without the bike and rider also accelerating. The difference in inertia between a very light wheel set and a heavy wheel set might be under 1% of the total inertia of the bike + rider, so the "spin up" when riding with the very light wheels might be less than 1% faster than with heavy wheels.

That being said, riders can often feel the differences in weight or stiffness between wheels, even if it doesn't result in differences in acceleration. This is because when we ride, the bike doesn't just move forward - we often swing the bike back and forth laterally. Differences in spinning wheels can often be felt when the bike is rocked laterally, because the inertial and gyroscopic precession forces can be significant compared to the weight/inertia of the bike alone. Likewise, wheels can have meaningful differences in lateral flex when the bike is leaned from side to side. Both of these can give the rider different impressions of the "responsiveness" of wheels - even if it doesn't actually result in the entire wheels + bike + rider system accelerating forward any faster.

I have to admit that even thought I know that light, stiff wheels don't actually make me accelerate much faster at all, I do enjoy the feeling that light stiff wheels give when I ride.

[martl]

Originally Posted by Mark McM

As above, it takes little energy to spin up a wheel when it is off the ground in a work stand.

As a matter of fact, it takes the exact same amount of energy to spin up a wheel regardless whether the wheel has contact to the ground or not

I have to admit that even thought I know that light, stiff wheels don't actually make me accelerate much faster at all, I do enjoy the feeling that light stiff wheels give when I ride.

Fully agree! I have a very small, very steep (optional) hill at the very end of my regular training route. When i feel cocky, i end my training routine sprinting up with all i've got left.
There are worlds between how that feels on my training bike with very heavy shamal style wheels, and on my good bike with the 1100g super stiff lightweights. Makes me almost want to reconsider what i have learned about physics

[rnhood]

Originally Posted by edgerat

What about stiffness of a wheel set? Lightweight seem to be the stiffest wheels out there, is being stiff good, bad, other? My only fancier wheels are DuraAce C50s and some Alpinist CLX I. have a build coming and trying to sort out the wheels.

Isaac

You already have two excellent wheel sets. You will be hard pressed to do any better, imho. The C50's are fast, beautifully built with extremely good hubs - arguably the best in the industry. The Aplinist CLX's are lightweight and also built extremely well. And both these wheel sets are good for the long haul.

I highly recommend you figure out how to test ride a wheel set before laying down a bunch of money. You might find out the boutique wheels are not as good as what you have.

[November Dave]

First, I'll contradict Peter P's assertion that bladed spokes flex more. You aren't taking the spoke out of a straight line when you stress it laterally, you are just pulling it harder or less hard. The stiffness of a spoke is a function of the cross sectional area of the spoke and the Young's modulus of the spoke material. Since most spokes are made out of the same material, cross sectional area matters, but section shape doesn't.

The #1 issue that flexy wheels have ever exhibited to me is understeering in hard cornering. Lace a 32h Open Pro with a 16h front hub and go rip some corners and you'll see what I'm saying. It's awful.

Really heavy wheels also corner less well, to me, than lighter wheels. I've known people who prefer the feel of heavy wheels (old, deep carbon rim brake wheels with alloy brake tracks, 2000g for the set type of stuff). Anything where you're throwing the bike around pretty hard, you will notice substantive differences in wheel weights.

The "spin up" stuff has always smelled like BS to me.

It was quite a while ago that I started thinking of wheels as "tire holders." Absent any notably bad characteristics - very heavy weight, profound lack of stiffness, bad build, unreliable hubs, etc - the differences between wheels are really down to the differences between the tires on them, and the pressure those tires are inflated to.

With the wheels you have, assuming you're putting road tires on them, I'd be in absolutely no hurry to buy anything else and wouldn't expect much difference from anything but a super light set (which may or may not be appropriate for what you're doing).

[Mark McM]

Originally Posted by November Dave

First, I'll contradict Peter P's assertion that bladed spokes flex more. You aren't taking the spoke out of a straight line when you stress it laterally, you are just pulling it harder or less hard. The stiffness of a spoke is a function of the cross sectional area of the spoke and the Young's modulus of the spoke material. Since most spokes are made out of the same material, cross sectional area matters, but section shape doesn't.

Spokes act somewhat like the guy wires on a tower. The wires only carry forces along their length, so their bending stiffness doesn't matters. Hence, the shape of the guy wires doesn't matter, all that really matters for the tower lateral stiffness is the material (modulus), cross-sectional area, bracing angles, number, and length of the guy wires.

Originally Posted by November Dave

The #1 issue that flexy wheels have ever exhibited to me is understeering in hard cornering. Lace a 32h Open Pro with a 16h front hub and go rip some corners and you'll see what I'm saying. It's awful.

Remember the Roval Fusee Star wheels? These wheels had narrow flange spacing and a shallow rim, hence they were very flexy laterally. A Cat. 1 racer I knew who used them in cyclocross races said that every time she took a sharp turn on them, they felt like they were folding over.

Originally Posted by November Dave

The "spin up" stuff has always smelled like BS to me.

Wheel weight is not nothing, but it only affects "spin up" in relation to how the wheel weight effects the entire system weight.

Originally Posted by November Dave

It was quite a while ago that I started thinking of wheels as "tire holders." Absent any notably bad characteristics - very heavy weight, profound lack of stiffness, bad build, unreliable hubs, etc - the differences between wheels are really down to the differences between the tires on them, and the pressure those tires are inflated to.

This is pretty much how I feel. All I'd add is that rim (inner) width can also make a difference, but only in as far as how it effects the tire dynamics.

And as far as stiffness goes, it is possible to have too little stiffness, but not really possible to have too much. Or to put it another way, as long as the wheels have adequate stiffness, any additional stiffness makes no meaningful difference.

[edgerat]

Thanks all for the info thus far! I agree, the two high zoot carbon wheelsets I have leave little to be desired. I am putting together a new build for an inbound F&F and need another set of wheels. On top of that, the build requires rim brake wheels so, both of the sets I have will stay on their respective bikes and the new bike gets whatever we all decide on as a group, hehe.

Isaac

[martl]

Originally Posted by November Dave

First, I'll contradict Peter P's assertion that bladed spokes flex more.

Absolutely correct. The way a bicycle wheel is built, a spoke only actions in its length and takes force in that direction. This is also why a tied and soldered wheel has almost no stiffness advantage; on the contrary, it denies the spoke the use of some of its length to deal with dynamic deformations of the wheel. It is used on track wheels where there are no road imperfections to deal with and originally had mostly the(today mostly forgotten) purpose to keep the broken spokes in position to avoid nasty injuries in case of a crash. (Jobst Brandt, i believe, cleared this up in his bicycle wheel book)

A larger diameter spoke can take more tension; a spoke with aero and weighr advantage like a sapim cx ray has a smaller cross section area and thus cant be tightened as hard as a larger diameter spoke as round spokes usually will have; this creates a slightly less laterally sfiff wheel.

[oldpotatoe]

Originally Posted by martl

This is also why a tied and soldered wheel has almost no stiffness advantage; on the contrary, it denies the spoke the use of some of its length to deal with dynamic deformations of the wheel.

A larger diameter spoke can take more tension; a spoke with aero and weighr advantage like a sapim cx ray has a smaller cross section area and thus cant be tightened as hard as a larger diameter spoke as round spokes usually will have; this creates a slightly less laterally sfiff wheel.

You tie and solder mostly to reduce the amount of movement of the spoke at the hub, mostly on non drive side rear, to try to eliminate broken spokes there.

The tension of a 14g, non butted straight gauge spoke and a thin, oval spoke should be the same on a well built wheel...as measured on a spoke tension meter...both should be 'about' 100-110 kgf for a normal rim...fronts and drive side rears.