2013 Dirty Dozen Training Rides
Chris Mayhew wrote:Also, lower your tire pressure. I don’t know what you weigh but 120 psi is quite high. It actually increases rolling resistance and decreases ride quality.
Well, it does not increase rolling resistance (rail road has one of the lowest one — metal on metal) but it decrease ride quality so much that total speed gets reduced. And there is non trivial relationship with friction-friction spot-skidding.
You are in fact wrong. Tire pressure that is too high does increase rolling resistance. There’s plenty of evidence out there. http://www.slowtwitch.com/mainheadings/techctr/wheels_tires.html
Actually, Google “Tom Anhalt tire” and spend more than 24 minutes reading it before getting back to me.
Chris Mayhew wrote:“Tom Anhalt tire”
Chriss, not to offend you but I’ve spent 5 years studying math and physics. If you want we can get deep into integral/differentials/etc. But even you first article shows:
The understanding of the above explanation will go a long way towards understanding why wider tires have lower rolling resistance than narrower tires (for a given tire construction and pressure), why higher tire pressures (to a point) will reduce rolling resistance, why higher “thread count” tire casings (i.e. thinner materials) typically exhibit lower rolling resistance, why thinner tire treads will reduce resistance to rolling, why materials used to enhance puncture resistance can increase rolling resistance, and why certain inner tube materials are faster than others.
And it’s to the point is not about decreasing, it’s about no increasing — it becomes flat.
As per Tom A. articles and as it was already discussed among physics — on real flat and smooth surfaces it’s not standing. Still higher pressure gives lower rolling resistance. What is happening in real life is that you cannot get surface smooth enough. And one using high pressure is going to bounce and vibrate. And it takes your energy. But it is not a rolling resistance!
Cool. Glad I started this. I am an actual Physicist for what it’s worth… Fortunately, all I really care about is getting to the top of these suckers. I’ve seen quite a lot of discussion about the moments of inertia of various wheels etc that basically boil down to “it’s totally irrelevant” but rolling resistance is obviously relevant to, well, rolling. It seems like for climbing, all things considered, MORE friction is better (loss of traction being one of the difficulties).
To completely sidetrack the discussion, I obviously appreciate that minimal weight is a good thing for climbing, but it did take a while to get comfortable standing on the really steep pitches on my road bike because the CG gets high compared to my heavier cyclocross.
ps — I am a bit over 160 so by your chart I should be at 110#. But the other question still stands — is it better with cobbles and whatnot to be on 32mm tires at 80#?
Anyway, I thought that at one point there were 15 dirty dozen hills. I was going to find the email with their names and then find them and ride them..Dornbush may have been one of them. At any rate, I will try to make it to canton to yell at people.. I mean encourage people.. To get to the top, since I am not able to race.
Neil I think larger tires with less pressure will help you on cobbles to bounce around a bit less/ have more surface area of contact. That being said I think 32’s are a bit of overkill 25’s or 28’s would be fine I think. Although if you have 32’s on a cyclocross bike already you could always give the hills a try on each bike and compare.
Yeah, it’s more complicated than a simple physics issue, because the road is not smooth. Imagine hitting a rock with really high pressure tires. They will not deform, so instead the entire wheel will have to go up as it rides over the rock. Pushing the wheel up takes energy. You get some, but not all, of that energy, since some goes into making your ride uncomfortable, etc. Now imagine the same thing with a soft tire. It deforms, the wheel doesn’t have to go up. There’s still energy loss, because it takes energy to deform the tire, and you don’t get all that back on the other side of the rock. But less energy is lost because only the tire deforms.
OTOH, on a smooth road the soft tire continually deforms and reforms its shape as it contacts the road, so you lose energy that is not lost with a hard tire. Metal wheels on a metal track are optimal for this reason.
So the comparative efficiency of tires depends on the road, the air pressure, how much shock the bicycle itself absorbs, the weight of the rider, maybe even the rider’s technique, and so on. It’s not easy to work out from basic physics, and even experimentally it’s hard to study because there are so many different factors.
First four yesterday — quite fun. No cobbles of course but Berryhill is pretty chewed up.
Drove home from the Mon valley this afternoon and went by Canton and Boustead (had not visited them before). I expected Canton to look like a climbing wall, so I was surprised that visually it is not that intimidating. It is so very short. Boustead on the other hand is just bad ass. I am currently very intimidated by that hill.
I searched around for Boustead on the forum and came upon the “how hard are they?” thread from last year, and I must say I was a little surprised by the “why would you want anything more than a 26” discussion (other than the machismo). Quite simply, with a compact 50-34 and a 32-28-25-23-…11 (Sram) that 34:32 lets me SIT DOWN on most of the hills. Anything below 22% or so and I am mostly to entirely seated (on the first 4 last weekend I stood only for the steep pitch on Berry Hill — the pretty part). Below 18% or so and it is possible to take a blow. Add to that for me it is my arms that blow up before my legs (I think some of that is (lack of) technique), as others also pointed out on that thread, and again being able to sit in the saddle is a big deal. That would basically not be true (for me) without the granny (I am AARP eligible…). My objective is making the hill, not making it fast (at least at first). I love that 32…
Boustead is fine, fun even. You will stand, but it’s so short you’re not going to wear yourself out.
Canton takes a lot of skill to ride up in my opinion. You run out of momentum pretty quickly if you are running a low gear. I generally won’t even use my lowest gear on Canton.
If you’re not competing for points, let the dust settle before attempting Canton, there’s always riders taking down other riders (not intentionally obviously). A bunch of people snap chains the first go around too.
Did reddan get Canton on the recumbent ever?
Nope. Crashed lots, flipped a couple times, once rolled it so badly I made the bike unfixably unridable and had to beg a ride home.
Current plan A (not this year) for Canton is fat low-pressure tires and try slightly higher gearing. Plan B is a recumbent trike; per Danny, that’s legit, so long as it keeps moving forward at all times.
I don’t know how you could possibly keep a front wheel down on Canton with a recumbent. I mean, more power to him if he has.
I’ll just say I had my own center of gravity issues just riding an upright hybrid with panniers. My front wheel came up immediately and no matter how far over the bars I tried to lean and I could not get it down.
I was too afraid of falling over backwards to keep pedaling. I’d say the hill laughed me off, but I stopped so soon, I don’t think it even noticed my presence.
Boustead has thus far been the upper limit of successfully keeping the front wheel down on steeps, and the front does feel awfully light there. Canton gets me because I start bouncing on the bricks, and once the front hops even a little bit, I’m pretty much done.
The son of a friend of mine, Greg Roberts in Boulder, does
I’m pretty sure he could go right up.
rice rocket wrote:On a 8? wheel, maybe.
C’mon, you can always put longer cranks there! :)
BTW, A lot of people do it on something like 32-32 which is ration one-to-one and in this case it’s to ration wheel-to-crank. As we know, for road bikes its 700c/2=350 to 172/172.5/175 mm ratio. :) So it should be doable on 700c wheel with 175 mm crank.
Mikhail wrote:Hm, is the Unicycle an answer to Canton?
A penny farthing ridden backwards perhaps?
I went out to Canton yesterday afternoon, but couldn’t figure it out. Now matter what I did, it felt like my bike as about to rear up and stop, and I couldn’t keep going. Any advice? I have a standard road bike — I guess a mountain bike would be better, but I can remember lots of road bikes making it up last year. I’ve got a handle on the other hills, but Canton terrifies and baffles me.
In my experience, you have to do two things:
– forward enough over the bars so that you don’t flip backwards
– butt back enough over the back wheel in order to maintain traction
If you can master it on long steep hills like Suffolk and Eleanor-Barry-Holt, then you should be OK on Canton.
Canton is a brute force thing. It is about keeping a minimum of momentum, which due to the cobbles and the contact patch that gets interrupted as a result, can be tough.
I have climbed it numerous times in dry conditions on my road bike with 23mm tires without dropping the pressure in them.
With a compact crank (50-34) and an 11-28 cassette, I need to be in the 2nd last ring in the back to have enough torque to keep some momentum.
Also, taking a running start never hurts. Here is a video I took during the summer.
For Canton you really really need to be low and over you bars otherwise you’ll pull up. Then you just need to keep pumping the legs, never stop. Ken’s rights, it’s a mix of brute force and also picking a good line. Once you get it, you get though:)
Keep your cadence the same. I had a problem last year with the front wheel pulling up or the back wheel spinning out. I couldn’t get my weight in the right spot most of the time at 34-28 (I sit and spin on most of the other hills at 34-25). I was finally able to get it at 34-32. I spun like crazy and it felt super slow but somehow in that gearing I got my body positioned in the right place. I also dropped my pressure (running 25s).
Nope but, Main street looks pretty crazy! Haha, will have to remember that one and give it a try someday!
On Saturday I’m going to do most of the course, probably stopping somewhere in the Southside before the last couple hills. I’ll be starting at 11am at Butler and 46th St if anybody is interested in joinin me.
I’ll be doing a medium to fast pace and I’m happy to ride at others’ paces or take short brakes when desired. I’ll probably fugde the route in Beechview so we can still hit the hills but minimize our time on Saw Mill Run and Banksville.
What’s the best time to show up at Canton or Boustead as a spectator?
Good luck to all of you hard core folks who are participating!
Congratulations to everyone who took part. Thanks to Danny Chew, and everyone who makes this cool event happen. It is great to have this in Pittsburgh.
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