Who's knowledgable about rims?
 

I've got a couple of Open Pro wheelsets and an Arrowhead wheelset. From the first time I rode on the Open Pro's I marveled about how smoothly they ride. What do you think is making the difference? I doubt it's the tires because I run narrower tires at higher air pressure on the Open Pros.

Can't say I've noticed differences among rims of similar nature, same for hubs. Tires and rotational weight I notice...

Different tires make a difference but possibly you have different spoke sizes? A thinner spoke or a single butted or double butted spoke will make a difference as it will flex in the middle thus softening the ride.

It's the tires and perhaps the tire pressure. Believe it or not, wider tires ride more easily, until you reach 28mm in width. Thereafter, they are slower.

Lawrence08648 is mistaken. Spokes don't change the quality of a ride. That's folklore.

Rim weight is a factor but you would only notice it during acceleration and climbing. You might be able to look up your rim weights on the web, at the vendor sites.

All else being equal, the depth and shape of the rim will play a huge role on how stiff the wheel is. Open Pros are slightly shallower than Aeroheads, but a more important difference is the shape of each rim. The OP's are boxy, while the Aeroheads are more triangular. The triangle shape makes a stiffer rim, and could be the difference you are feeling.

There are many other variables too. If you are on very smooth pavement, the higher pressure tires you mention may in face make a big difference in feel. It would probably be better to compare each wheelset with the same tires at the same pressure.

Agreed. But spoke thickness will affect lateral stiffness quite a bit.

New tires usually feel much better than old tires, they're softer and have better traction. Tires harden with age, some experts say to replace all tires after 3 years, regardless of remaining tread. Same holds for car tires. Old brittle tires are more prone to blowouts.

Al

rydaddy, stiffness of rim is not a factor. Tires are a lot softer than rims, so it's impossible to feel the stiffness of a rim.

There's so much folklore!

I'n normally inclined to agree with you, but Retro did say specifically: "I run narrower tires at higher air pressure on the Open Pros." so what he's experiencing musn't be the rolling benefits of wider tires (generally though, I think you're dead on about that. In fact, if the surface you're riding on is anything less than smooth, tires even wider than 28s might let you roll faster).

Sure, tires flex much, much more than the rest of the wheel but spokes flex long before the tire casing bottoms out. For the spokes to flex, the rim must be flexing a measurable amount as well. It seems possible that a sensitive rider might be able notice the difference between different rim profiles.

Retro doesn't seem like the type to be taken in by goofy marketing BS, so I'm sure there's something to what he's saying other than folklore.

No, I don't believe a rider can feel spoke stretching, either, and the ability to feel it is the premise of your post.

You owe it to yourselves to read Jobst Brandt's book. It's not hard reading, and it's not long. He is a mechanical engineer with a lot of background in metalurgy. He's the only person who has measured the forces in bicycle wheels. Measurement is what counts. No one even does blind tests comparing two wheel types. Well, maybe someone does, but no one has ever claimed to have done it. So all this theorizing leads nowhere useful.

Not exactly. As I understand it, spokes compress (rather than stretch) under load and lose tension temporarly as they bear the weight of the bike and rider. Obviously some (however minute) deformation of the rim must be occuring in order to de-tension the spokes, no? And maybe, just maybe, the difference in stiffness between two different rims might be sensible through the OVERWHELMING influence of the tire width and volume.

I can't say as I've ever noticed a the difference in stiffness between rims or wheels myself, but I've never really thought about it much either. I'm certainly not a mechanical engineer, and I havn't read the Brant book (it's on my list) but Retro Grouch's assertion that he uses narrower tires on the wheel that feel "smoother" make me feel like something must be up.

I thought this was half of the fun!;)

No they don't. Spokes are too slender to take any compression without failing in buckling first. What happens is that some, or most of the pre-loaded tension is taken out of the bottom most spokes. It is re-distributed in a suprisingly uniform pattern among the remaining spokes. To read what the best of the Bike Forum community has to say on this chek this out: http://www.bikeforums.net/showthread...+bearing+wheel

Yes, tires make a differences in ride quality. No question about it. In fact, they make more of a difference than anything, including frame. Nothing can change a bike's ride as much as tires can.

Rims do not affect ride quality. Please take my word for it until you read Brandt's book. Thereafter, ignore me and listen to him. OK, they do affect ride when you consider their weight. Lighter rims accelerate and climb better than heavier rims. But that's the only difference. Stiffness simply is not a factor.

Yes, theorizing is fun, for sure. I love it, too. But these things have been measured, and it helps to learn from other people's experience. It doesn't help to answer someone's question with theory that goes against what we've learned.

I read it and Gerd Schraner's also.
Brandt's book as published in 1981, with his tests on 1981(or, older?)components.
Schraner's was published in 1999.

I don't believe the science of bicycles has advanced enough to nullify Brandt's findings. His book is on its third edition. There have been recent corrections and additions. What did you learn from Schraner's book. Does anything in it conflict with Brandt's assertions?

Brandt's book is on the third edition, doesn't indicate anywhere that I could find that it has been updated, just "pointed rewrites"?

Schraner's book is based on his R&D experience, not engineering or computer analysis.

Soil Sampler, I don't follow what you're saying. What R&D are you talking about, and are you saying that engineering and measurement are less valid than other methods of exploration? I found Brandt's book and the arguments in it to be compelling and convincing. If you disagree, I'd like to know how.

I know the guy is offputting on usenet, but as far as I can tell, his observations about wheels are correct. I don't let his personality get in the way of my respect for his expertise.

didn't disagree or agree, pointing out the supposed age of the technology and materials that was used.

R&D-race and development(trial and error.)

Where I come from, R&D means research and development. Anyway, a spoked wheel still gets its strength from spoke tension, whether you use exotic or conventional materials. Cross-spoked wheels are still stronger than radial-spoked wheels. More spokes still provide more strength than fewer spokes.

Bicycle technology advances at a very slow rate, compared with electronics and software. A three year old computer (or boombox or mp3 player) is nearly obsolete. A 30 year old bicycle is far from obsolete for everyone except a professional racer. Yes, there have been advances, and I don't want to live without many of them, e.g. clipless pedals, alloy rims. But they don't change the basic science of things.

If you'd like to cite something that caused a fundamental change in either our understanding or the practicalities, please do so.