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Recreational Cyclocross and Gravelbiking This has to be the most physically intense sport ever invented. It's high speed bicycle racing on a short off road course or riding the off pavement rides on gravel like :The Dirty Kanza". We also have a dedicated Racing forum for the Cyclocross Hard Core Racers.

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Old 06-24-09, 06:15 PM   #1
Sincitycycler
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Any advantage of using a 700x32c tire over a 700x28C?

Been commuting on my fixie, but my normal route has been torn up somewhat due to construction, and I even have to run on the sidewalk on some sections w/ those annoying relieve cracks every 4 feet...

Currently running 700x23 tires at 116psi, but the rough sections knock my fillings out

I like get a smoother ride-been thinking of 28s or 32s at <100psi. Suggestions?
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Old 06-24-09, 07:40 PM   #2
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Been commuting on my fixie, but my normal route has been torn up somewhat due to construction, and I even have to run on the sidewalk on some sections w/ those annoying relieve cracks every 4 feet...

Currently running 700x23 tires at 116psi, but the rough sections knock my fillings out

I like get a smoother ride-been thinking of 28s or 32s at <100psi. Suggestions?
I've used both. I would say 28's can do almost any firm surface, including gravel.

32's can run at lower pressures and are more stable over potholes, gaping cracks and soft surfaces.

I use 28's and run them at 100 psi, the ride is acceptable. 32's are not going to feel as fast, if that matters.

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Old 06-24-09, 08:04 PM   #3
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Either size should be a considerable increase in comfort from a 700x23 which I no longer ride. My current tires are 32 cross tires which are dying. I may go for a set of 30's with the round/smooth profile rather than the 32's with cross treads. Keep in mind manufacturers aren't always on the same scale when it comes to measurement; I've seen 32's close to 30's and 28's also close to 30's in actual size.
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Old 06-24-09, 08:43 PM   #4
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Agreed, although you will notice the increase in rolling resistance. The ride is a lot smoother.
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Old 06-25-09, 11:20 AM   #5
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It depends on if the 700x28 is a city or trekking tire or if it is a road racing tire. The former would be exemplified by something like a vittoria randonneur and the latter would be more like a conti gatorskin or grand prix 4 season.

Basically, the lower of a pressure range is has, the more comfortable it can be, albeit at the expense of more rolling resistance.

The 700x32's I've tried have had noticeably more resistance though I hear the Panaracer Urban Max 70032 @ 100psi rolls pretty fast.
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Old 06-25-09, 11:24 AM   #6
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I went from a 27c to a 32c this year. The change was not dramatic, but it was welcome. The roads this year are hideous, construction everywhere, potholes, you name it.

I am contemplating something even larger.
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Old 06-28-09, 12:36 PM   #7
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Agreed, although you will notice the increase in rolling resistance [with increased tyre width]
No. This is one of those everyone-knows things that isn't true. RR depends a lot on tyre compound type and tyre wall thickness, and for a given tyre it descreases with pressure, but wider tyres actually have LOWER RR. Take a look at http://www.terrymorse.com/bike/rolres.html and see the sports touring 28mm kick the ass of the race optimized tyres narrower tyres.

24mm tyres are still faster in real road race conditions, because they take place at speeds where air resistance dominates, and a narrower tyre provides reduced frontal surface area.

So if you seek out a premium compound wider slick then increased RR shouldn't be a problem. I'd see if there is a 32-38mm Rubino, or go for a Sports Contact. Exact tyre width should depend on surface and on ***rider weight.*** Rivendell has a good chart for this.
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Old 07-02-09, 07:35 PM   #8
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So based on the above tests, the Hutchinson Top Speed is the fastest clincher tested?
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Old 07-04-09, 10:06 AM   #9
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So based on the above tests, the Hutchinson Top Speed is the fastest clincher tested?
Yes when not taking into account wind resistance.
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Old 07-04-09, 12:14 PM   #10
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So based on the above tests, the Hutchinson Top Speed is the fastest clincher tested?
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Yes when not taking into account wind resistance.
actually looking at the figure it seems to me that the hutchinson would be the slowest.
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Old 07-04-09, 06:04 PM   #11
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So based on the above tests, the Hutchinson Top Speed is the fastest clincher tested?
My bad - I'm looking at this on a Netbook, and I forgot there where several graphs below the one I referred to - which was the "classic" Jobst Brandt graph - http://www.terrymorse.com/bike/imgs/rolres.gif; the fast 28mm there is the Avocet. And performance of tyres of the same width varied a LOT.

Basic lesson: it's the tyre compound that matters most, not the width. Fast compound (with low hysteresis energy) used only to come in a narrow tyres for racers, but you can now get it in wider rubber - eg 1.5 x 26 Rubinos. Otoh performance of "premium" narrow racing tyres varies widely.

..And if you ride too narrow a tyre on a soft or loose surface then the physics gets more complicated and you lose energy in other ways. Ditto for too high a pressure I *think* - the back wheel's tyre needs enough flex to conform to the surface to transfer power ...

Oh - and latex tubes will make you go faster! Good article on RR on the road:

http://www.rouesartisanales.over-blo...e-1503651.html



..And the physics of real offroad tyres for MTBs are so complex I don't even want to think about it!
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Old 07-04-09, 11:39 PM   #12
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I like get a smoother ride-been thinking of 28s or 32s at <100psi. Suggestions?
Riding 28s or 32s at anything close to 100psi is counter productive... The while point of getting a bigger tire is so you can run much lower pressure... I have a Rivendell that I run 33s on with around 60psi, my cross bike runs around 45-50psi when on trails and I haven't had any problems...

If you go with the bigger tire, I recommend nothing higher than around 80 at the max...

Grant Peterson of Rivendell has pretty strange ideas sometimes, but he is right on with a lot of stuff also... Check out this article http://www.rivbike.com/article/components/tires

Chris
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