while we’re talking tires…good compromise between gravel and slick?

[Harry Meatmotor]

@hozn 146469 wrote:

Wow, that is a lot of pressure! I have run increasingly lower pressures, trying o shake myself of assumption that road tires start at 100psi. Or at least trying to see how low I can go before I start noticing problems. Tubeless helps here; maybe carbon rims do too (on the road bike). I have started running 85/90psi for my 23mm tires. Typically that is without backpack. I am running the 28mm tires now at 60/65psi. And 25s I guess I will run at 75/80 or 80/85 (we’ll see what works better; haven’t been on 25s for awhile).

I think by some/many tests my pressures are too low for optimal rolling resistance, though I will admit to being intrigued by Jan Heine’s comment that our perceived speed is often wrong because we associate vibrations per second as speed; however, when the rider is experiencing the road vibrations that is an inefficient dissipation of energy (i.e. so softer tires feel slower, despite being faster).

Time to try doing some roll down tests with decreasing pressure. Timed descent with no pedal input and no change in position on the bike.

These are also known as hill repeats, however.

[hozn]

I am skeptical of my ability to replicate bike position exactly and seems like aero would be a much larger contributing factor than crr?

[Raymo853]

@hozn 146469 wrote:

Wow, that is a lot of pressure!

I was thinking wow those are tiny tires, winter 25s and summer 23s. I suggest changing to 28s for the summer and winter. 28s are faster and more comfortable than the 23s or 25s.

[hozn]

@Raymo853 146562 wrote:

I was thinking wow those are tiny tires, winter 25s and summer 23s. I suggest changing to 28s for the summer and winter. 28s are faster and more comfortable than the 23s or 25s.

Well, that is also true! I do enjoy having narrower tires on the road bike to change it up — justify having a dedicated road bike and all . I have 23s on there now (measure around 25mm); they were cheap and I just can’t bring myself to discard the still-good tires (and they feel great). I have a set of 25s to put on next; those fit the rims nicely: tire same width as rim so no bulb effect.

[Raymo853]

@hozn 146567 wrote:

Well, that is also true! I do enjoy having narrower tires on the road bike to change it up — justify having a dedicated road bike and all . I have 23s on there now (measure around 25mm); they were cheap and I just can’t bring myself to discard the still-good tires (and they feel great). I have a set of 25s to put on next; those fit the rims nicely: tire same width as rim so no bulb effect.

I so agree on using up tires. I have four Bonti AW2 28s that just will not wear out allowing me to buy nicer Specialized 32s.

[hozn]

@Raymo853 146585 wrote:

I so agree on using up tires. I have four Bonti AW2 28s that just will not wear out allowing me to buy nicer Specialized 32s.

So how have the Specialized Roubaix 2BR treated you?

I gave mine to a co-worker, but have periodic regrets.

[huskerdont]

@Raymo853 146562 wrote:

I was thinking wow those are tiny tires, winter 25s and summer 23s. I suggest changing to 28s for the summer and winter. 28s are faster and more comfortable than the 23s or 25s.

Well, I have experimented a fair bit and can definitely say that for my weight and riding style, the 23s I have are faster/easier to roll and more fun than the 25s, and the 25s are easier than the 28s. I don’t find any problems at all using 23s in good weather, other than the obvious need to be a bit more careful at bridge joints, cracks, etc. So when the weather is nice, I definitely prefer 23s. YMMV.

This is my perception, at least. I have not done the roll-down test that Mr. Meatmotor suggests. I doubt my ability to do them accurately, but they sound like fun. I might be observed some day sitting by the side of the 41st Street hill switching out tires. (Because you’d need the same weather for a good test, so wouldn’t want to come back another day.)

Note that for real winter (snow/ice) I have other bikes that have knobby tires–cyclocross (32s/35s) and MTB (27.5 x 2.25), so it’s not like I’m riding 25s in the snow.

[Raymo853]

@hozn 146586 wrote:

So how have the Specialized Roubaix 2BR treated you?

I gave mine to a co-worker, but have periodic regrets.

I love the one I have, but it does seem to wear quickly. I realy just want to go buy two new ones and toss the worn one and the Bonti 28 on the front. Hmmmmm, maybe I should do that right now.

[Raymo853]

@huskerdont 146592 wrote:

Well, I have experimented a fair bit and can definitely say that for my weight and riding style, the 23s I have are faster/easier to roll and …

When it comes to speed and comfort, the research by Trek, Specialized, Continental, Michelin, experts on touring, randonneuring, racing, fitness riding, and so on …. all agree 25s and smaller tires are slower on real World surfaces. Yes on a very smooth surface, like a polished wooden track, smaller tires are faster even when you include tire mass as a factor. They all concluded larger (up to a point, about 28) tires are faster for everyone regardless if they weigh 35 or 135 kg, are loaded tourists, grand tour sprinters, crit racers, sport racers, fitness riders, ….

[huskerdont]

I’ve read those articles and understand what they’re saying about the contact patch length vs. width, but it hasn’t jibed with my experience riding, especially when going up hills. Maybe it’s the tires I’m using or maybe it’s only perception, I dunno. I’m happy enough with what I’m doing that I see no reason to change it. It’s not like I need to shave a couple of seconds off on a time trial or anything so that it matters that much. If I need to ride gravel or cobbles or really rough roads, I use a different bike.

[Raymo853]

And you must see my bias and bitterness. Been searching for nice 28s since the early 90s. I am always ready to rant as I hope the market demands continues to build for such tires.

So wish Michelin would bring back the Pro2 in their 25c size or better yet a 28. Those were huge 25s, on Open Pros there bigger than my Bonti 28s on Stan Grails. Plus they rode better than any tire I ever have had and rarely flatted.

[vvill]

@huskerdont 146598 wrote:

I’ve read those articles and understand what they’re saying about the contact patch length vs. width, but it hasn’t jibed with my experience riding, especially when going up hills.

I think it makes sense that if a lower pressure wider tire is faster on imperfect flat roads because of reduced energy loss from ‘bouncing’, you’re going to lose some stiffness going uphill especially if you’re riding a shorter / higher power climb. Most of the tests I’ve seen are done under very controlled environments and I don’t think they’d accurately simulate say, a 15% grade where the rider is out of the saddle wailing on their handlebars.

I’ve run 28s and 25s for road riding and think I still slightly prefer 25s. But I don’t buy 23s anymore (although still have some in rotation, and they don’t particularly bother me).

[huskerdont]

@hozn 146469 wrote:

Wow, that is a lot of pressure! I have run increasingly lower pressures, trying o shake myself of assumption that road tires start at 100psi. Or at least trying to see how low I can go before I start noticing problems. Tubeless helps here; maybe carbon rims do too (on the road bike). I have started running 85/90psi for my 23mm tires. Typically that is without backpack. I am running the 28mm tires now at 60/65psi. And 25s I guess I will run at 75/80 or 80/85 (we’ll see what works better; haven’t been on 25s for awhile).

I think by some/many tests my pressures are too low for optimal rolling resistance, though I will admit to being intrigued by Jan Heine’s comment that our perceived speed is often wrong because we associate vibrations per second as speed; however, when the rider is experiencing the road vibrations that is an inefficient dissipation of energy (i.e. so softer tires feel slower, despite being faster).

I was just watching a GNC video where (converting roughly from kilos to pounds) for my weight with pack, optimal pressure (with tubes) for mixed roads would be approaching 104 psi. They were saying that for 25s, start with 95 psi and add 3 psi for every 7 pounds. Then, if you’re running 23s, add another 3 psi. This would likely feel squishy to me (depending on the tires) and I’d worry about snakebites, but it’s something I may experiment with. I know I’ve always tended toward higher pressure, even for mountain biking, than what is recommended; that is something that would be hard to shake.

The 145 is crazy, yes. Don’t think I’d even experiment with that much. I’d be nervous it wouldn’t hold.

http://www.roadbikereview.com/reviews/5-ways-to-make-your-current-road-bike-faster

[hozn]

Good link! — Yeah, I guess that puts me (~80kg) at 98psi for 25mm tires, which I’m guessing would be an average that gets split to a 45/55 weight distribution. That probably is a little higher than I’d run, but it wouldn’t surprise me if that were an optimal number.

The Velo test (http://velonews.competitor.com/where-the-rubber-meets-the-road-what-makes-cycling-tires-fast) found that good tires generally saw little decrease in rolling resistance with lower pressure, which to me just meant that with a supple tire making it more comfortable wasn’t hurting speed. My anecdotal experience is that I can certainly tell the difference in comfort when I drop the 28mm tires down from 80psi to 65, but it doesn’t feel any slower. It does deflect more on climbs, though, so I do notice that.

Jan Heine’s pressure article is this one https://janheine.wordpress.com/2016/03/09/tire-pressure-take-home/ . Jan comes off sounding very hyperbolic (bigger tires and lower pressure always faster!), but when he actually quantifies recommended pressures as he does in this article, it isn’t much different than what anyone else is saying. (Yes, he was saying it before others.) So using that 15% tire drop chart (which equates to more tire drop on better tires, but still apparently a good starting point) yields something around [or just shy of] 90s psi for my setup (weight + bike weight, etc.) and maybe 75ish psi for 28mm tires. Obviously that’s lower than the GNC recommendation but still higher than I’ve settled into running by default.

Of course there’s also the whole “aero” component which is huge. The only folks I know that have actually looked at both together are Flo:

– Part 1 (tire aerodynamics): http://flocycling.blogspot.com/2016/04/flo-cycling-a2-wind-tunnel-tire-study.html
– Part 2 (rolling resistance & net gain for tires): http://flocycling.blogspot.com/2016/06/flo-cycling-a2-wind-tunnel-tire-study.html

Of course, they didn’t measure anything wider than 25mm. But interestingly, the widest tires don’t win here, but the narrowest don’t either (so aero didn’t completely trump crr). I’m not sure if there’s much more that can be inferred than “it’s complicated”, but clearly when aerodynamics come into play they reshuffle rankings based on crr alone. It would be interesting to see a test that incorporated some much larger tires (28+mm) to see how those compared; I’m imagining that wind resistance will make those slower tires on the whole, but I don’t know that this has been tested scientifically.

[huskerdont]

Kind of a fun exercise to read them all at once and compare. I see from both the rolling resistance test and the wind drag test that I would have done well to buy those Conti GP 4000s I was considering back when they were on sale. However, the Tufos recently installed are ranked #20 in rolling resistance (even with all those tubeless tires in there, which currently aren’t a real option for me), so those are fine (they weren’t rated in the drag test). I have too many tires that need to be used up at the moment anyway, but eventually may get a pair of Contis in 25s just to compare.

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