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  1. #1
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    Zinn article on dirt road tire pressures.

    This is interesting, especially when it gets to the rolldown testing and perceived speed -

    What is the optimal tire pressure for gravel? | VeloNews.com
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  2. #2
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    Good read, thanks Mike!
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  3. #3
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    Nothing in that really surprises me. It will be interesting to see how the study progresses.

    The most interesting part for me was the 'psychology' of the rider who said it felt like the harder tires were faster, when they weren't. I wonder what his cycling background is?

  4. #4
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    Thanks, that was well worth reading.

    And since this is about tire pressure, I've got a can of worms.

    I've been riding 650b\42mm wheels\tires and have been running less and less pressure looking for the happy place; Pretty much all road miles. I was starting at 50psi and riding till they started feeling soft before pumping them up again, maybe a month and a half or two months. With my latest front tire I started pumping to 40psi and riding past the feeling soft to getting kinda spongey before pumping them up again, probably that two months again.

    What I'm seeing is that the front tire is showing more wear at the lower pressures, to the point that I could barely read the tread when I looked at the ride. There is no flat spot, the tire is round but the tread is wearing down thru the shoulder on both sides, whether from more tire contact(patch size) or cornering, I don't know.

    I've never seen this much tire wear on a front tire with higher pressures. Is this more "scrubbing" of the tire caused by the lesser pressure or is the larger contact patch somehow contributing to it. I don't mind and find it a small price to pay for the better ride, it's just enquiring minds would like to know.
    Last edited by velodog; 2 Weeks Ago at 01:49 PM. Reason: more to add
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  5. #5
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    Quote Originally Posted by velodog View Post
    Thanks, that was well worth reading.

    And since this is about tire pressure, I've got a can of worms.

    I've been riding 650b\42mm wheels\tires and have been running less and less pressure looking for the happy place; Pretty much all road miles. I was starting at 50psi and riding till they started feeling soft before pumping them up again, maybe a month and a half or two months. With my latest front tire I started pumping to 40psi and riding past the feeling soft to getting kinda spongey before pumping them up again, probably that two months again.

    What I'm seeing is that the front tire is showing more wear at the lower pressures, to the point that I could barely read the tread when I looked at the ride. There is no flat spot, the tire is round but the tread is wearing down thru the shoulder on both sides, whether from more tire contact(patch size) or cornering, I don't know.

    I've never seen this much tire wear on a front tire with higher pressures. Is this more "scrubbing" of the tire caused by the lesser pressure or is the larger contact patch somehow contributing to it. I don't mind and find it a small price to pay for the better ride, it's just enquiring minds would like to know.
    I've been doing some experimenting on my gravel bike as well.

    I'm currently running 650b (Boyd Jocassees) with WTB ByWay Road Plus 47mm tires (tubeless).

    I'm trying to find the optimal pressure for mixed surface (rough pavement and gravel/dirt roads).

    Ideally, I'd like to get as low as I can comfortably without pinch flatting.

    My problem is, I'm a big, heavy rider at 6' 5" and 230lbs. If I get my pressure too low, those fat tires start to bounce when I'm hammering on pavement.

    I love the tire volume on fast descents on gravel roads. The bike feels like it's floating over the rough road surface. Since I've been running that setup, I've PR'd every downhill segment on my favorite gravel rides, just because I can descend so much more comfortably without risking a rim hit/pinch flat if I hit a rock or pot hole. It's a pretty fun feeling hammering down the side of a mountain on a dirt road going 20+ mph.

    I think on I'm going to experiment with a 700c wheel with some 30mm Schwalbe G-One Speed and the 38mm Schwalbe G-One All Around, and see if that improves the bouncing without losing the comfort on the fast downhills.

    I suspect for most of the riding I do, I'll end up on something in the 38-42mm range on 700c with moderate pressure. I'll save the 650b/47mm setup for the harsher washboard type stuff that I usually ride later in the season....

  6. #6
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    Quote Originally Posted by Finx View Post
    I've been doing some experimenting on my gravel bike as well.

    I'm currently running 650b (Boyd Jocassees) with WTB ByWay Road Plus 47mm tires (tubeless).

    I'm trying to find the optimal pressure for mixed surface (rough pavement and gravel/dirt roads).

    Ideally, I'd like to get as low as I can comfortably without pinch flatting.

    My problem is, I'm a big, heavy rider at 6' 5" and 230lbs. If I get my pressure too low, those fat tires start to bounce when I'm hammering on pavement.

    I love the tire volume on fast descents on gravel roads. The bike feels like it's floating over the rough road surface. Since I've been running that setup, I've PR'd every downhill segment on my favorite gravel rides, just because I can descend so much more comfortably without risking a rim hit/pinch flat if I hit a rock or pot hole. It's a pretty fun feeling hammering down the side of a mountain on a dirt road going 20+ mph.

    I think on I'm going to experiment with a 700c wheel with some 30mm Schwalbe G-One Speed and the 38mm Schwalbe G-One All Around, and see if that improves the bouncing without losing the comfort on the fast downhills.

    I suspect for most of the riding I do, I'll end up on something in the 38-42mm range on 700c with moderate pressure. I'll save the 650b/47mm setup for the harsher washboard type stuff that I usually ride later in the season....
    Before going to 700c\38-42mm why not try 38-42mm tires on those 650b rims? Like I said I've been running 650b\42mm(Compass) and have been quite happy with that set-up. I'm not as large as you, 6' and 185lbs, but on the road with some gravel thrown in the 42mm tires work well. Going to 700c\42mm seems like an un-necessary jump in wheel size when you can get the same tire volume in 650b without the weight gain that would come with the larger 700c wheel size.
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  7. #7
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    Quote Originally Posted by velodog View Post
    Before going to 700c\38-42mm why not try 38-42mm tires on those 650b rims? Like I said I've been running 650b\42mm(Compass) and have been quite happy with that set-up. I'm not as large as you, 6' and 185lbs, but on the road with some gravel thrown in the 42mm tires work well. Going to 700c\42mm seems like an un-necessary jump in wheel size when you can get the same tire volume in 650b without the weight gain that would come with the larger 700c wheel size.
    The only reason I wanted to try the 650b was to experiment with the larger volume tires (47mm-52mm). For lower volume tires (say 40mm and down) I want the increased wheel circumference of 700c for better rollover, and the crank clearance (I run 175mm cranks).

  8. #8
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    The larger wheel/tire dia is going to allow u to use lower pressure with the same tire width. I got to think this is a win-win situation going to the largest wheel/tire you can run. And if the road is rough, this gets to be a bigger and bigger issue with the bigger rocks!
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  9. #9
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    Quote Originally Posted by Mike T. View Post
    This is interesting, especially when it gets to the rolldown testing and perceived speed -

    What is the optimal tire pressure for gravel? | VeloNews.com
    Great article. Thanks Mike!
    "With bicycles in particular, you need to separate between what's merely true and what's important."-- DCGriz, RBR.

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  10. #10
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    I was running a WTB 45c Riddler on a set of Stans Arch MK rims with 26mm internal width set up TUBELESS. On gravel only rides I was running 36psi. Was very happy, it even did well on single track. I could smoke it down the hills of N.C. If my ride was heavy with Asphalt, I would bump up to about 40. These tires got really big on MK rims. I think the 26 internal was about as big as I would go with the current batch of tires. I had a 40c Kenda Happy Medium on this rim at one time. It was starting to get a little square but still did ok. Oh, BTW I'm about 165 lbs

    Last edited by Enoch562; 2 Weeks Ago at 02:13 PM.

  11. #11
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    Zinn article on dirt road tire pressures.

    See this article by Jan Heine. https://janheine.wordpress.com/2016/...ure-take-home/

    See this calculator based on Frank Berto's work referenced in that article. http://psicalculator.com

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