Wheel and Tire Questions

[scottaharper]

I decided to pull out a set of Mavic Cosmic Carbone wheels that I had hanging in my garage to see if my reaction to them was the same as when I took them off my bike about a year ago. Sure enough, despite the fact that I love the way the roll, they are still noisy and rough riding compared to my 32 hole Archetypes. In fact, the difference was bigger than I remember. Looks like they will have to go.

This got me thinking about wheels, tires, and related stuff. I realized that I have several questions that I am hoping the forums wisdom can help me answer without spending money and time to figure it out through direct experiments.

1) The noise these Cosmics make when I hit a bump or shift annoys me. It seems like the wheels are acting as a megaphone for any sound that occurs on my bike. I am wondering what other wheels might be similar, so I can avoid them. Is is true of all carbon rims? All deep dish rims? Only true of the Cosmics?

2) The ride seems harsh compared to my Archetypes. Is that due to the deep rim, fewer higher tension spokes, or both?

3) In order to maximize the aero benefit of the deep rims, I ran 23mm tires instead of the 25mm that I normally ride. However, I did run them at the same pressure that I run in the 25mm. I know that 25mm provides a nicer ride and I thought that was because you could run lower pressure, and I thought that it was the lower pressure that was providing the benefit. But now I am wondering if the narrower tire was contributing to the rough ride. So my question is will a 25mm tire smooth out the ride of the bike more than a 23mm, if both tires are inflated to the same pressure?

Thanks in advance for your help,
Scott Harper

[kgreene10]

Hi Scott. I don't have answers to all of your (good) questions, but on the carbon rim echo chamber, I have found three things. Tubulars have less of an echo than clinchers. Clinchers with a foam core like the Corimas (also used by Rol) have less echo than standard hollow ones. Among the standard clinchers without a foam core, there's a noticeable difference across manufacturers. I found the Zipp FC to have a lot more echo than the Enve, at similar depths. Oh yeah, depth matters of course. Deeper rims echo more than shallow ones.

[Black Dog]

25mm tires will edit: not ride harsher than 23mm at the same pressure. You need to run larger tires at lower pressures to take advantage of the rolling resistance and smoother ride. Yes, bigger tires at lower pressures are smoother and faster. They are not mutually exclusive. In fact when Tour magazine did rolling resistance testing they found that a 28mm tire was the fastest.

[uber]

I too have found the deeper carbon rims make more noise. Corima is the quietest, Enve the next, and Zipp FC the loudest.

[sokyroadie]

25mm tires will ride harsher than 23mm at the same pressure.

I do not understand this statement.

Jeff

[Black Dog]

I do not understand this statement.

Jeff

Since the 25c tire has a larger contact patch the load is distributed across a greater surface area with the same resistance to deflection as a 23mm tire at higher pressure with a smaller patch. The net resistance to deflection is greater in the larger tire. Think of snowshoes, same mass of person with or without them, but with them you stay on top, without them (load is concentrated over smaller area and you sink).

[cnighbor1]

Have you considered EAR PLUGS while riding those wheels !!!!!

[ceolwulf]

Have you considered EAR PLUGS while riding those wheels !!!!!


Would also help for the shouting drivers.

[Dead Man]

ear BUDS. Bliss from wind and wheel noise, and angry motorists.

28mm tires are faster than 23s?

[Black Dog]

ear BUDS. Bliss from wind and wheel noise, and angry motorists.

28mm tires are faster than 23s?

The data does not lie. In terms of rolling resistance 28c tires are faster than 23mm tires on the road.

[Dead Man]

Well.... that goes against everything I've ever believed about bike tires.

Anyone have some linkage?

How does heavier weight factor in? (I've not yet ever really looked at tire weight... only just got my first set of sub-1500g wheels a few months ago, taking baby steps)

[Black Dog]

I do not understand this statement.

Jeff

Holy crap. I forgot to write the word NOT. Sorry for the confusion.

[Black Dog]

Well.... that goes against everything I've ever believed about bike tires.

Anyone have some linkage?

How does heavier weight factor in? (I've not yet ever really looked at tire weight... only just got my first set of sub-1500g wheels a few months ago, taking baby steps)

Here http://velonews.competitor.com/2012/03/bikes-and-tech/technical-faq/tech-faq-seriously-wider-tires-have-lower-rolling-resistance-than-their-narrower-brethren_209268 is some data.

[rustychisel]

Cosmic Carbones can be noisy, but by no means as noisy as full carbon rimmed clincher wheels.

Carbones are a box section aluminium rim with carbon fairing, which acts as an echo chamber, and when you hit a pothole the 'crack' noise does give pause for thought. But they're strong.

As to tyres: I'd always maintain that good quality 23s are better than merely average 25s. If you're not racing go the 25s all other things being equal; it depends on your weight, riding style, the tyres you use, type of roads ridden, inflation pressure.... you get the idea

[oldpotatoe]

Holy crap. I forgot to write the word NOT. Sorry for the confusion.

whew, for a minute there I was worried the sun wouldn't come up this morning...

[Mark McM]

The data does not lie. In terms of rolling resistance 28c tires are faster than 23mm tires on the road.

... if you ride in a vacuum. At speed, and on smooth surfaces, the 23mm tire may be faster, because the losses in rolling resistance are more than compensated for by reductiions in aerodynamic drag.

[Black Dog]

... if you ride in a vacuum. At speed, and on smooth surfaces, the 23mm tire may be faster, because the losses in rolling resistance are more than compensated for by reductiions in aerodynamic drag.

That is why I said 'on the road' the 28 is faster because of the highly irregular surface. On a very smooth surface there is not a big difference in rolling resistance and drag is more important. None of the roads I get to ride would ever fit the latter.

[Dead Man]

Fortunately for me, most of my 30-mile one-way commute is perfect, new asphalt... gonna stick wit my 23s

[Mark McM]

That is why I said 'on the road' the 28 is faster because of the highly irregular surface. On a very smooth surface there is not a big difference in rolling resistance and drag is more important. None of the roads I get to ride would ever fit the latter.

According to Zipp lead engineer Josh Poertner, their tests with Zipp 303 show that it is optimized for a 23mm tire, and that using a wider tire results in a slower wheel (despite the lower rolling resistance). The optimum width will vary with the rim and the road surface of course, but in any case, wider tires are not always faster.

Here's a Velonews Tech FAQ article (http://velonews.competitor.com/2012/03/bikes-and-tech/technical-faq/tech-faq-again-bigger-tires-roll-faster_209888)where the trade-offs in tire width are discussed.