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mjr

Comfy armchair to one person & a plank to the next
You probably cannot afford to live in a council area where they have 25 workers permanently on 24-hour standby with all the equipment warmed up and read to roll at the first report of a pothole.
Maybe not to that extent, but I'd happily pay a bit more council tax if some of it went to better cycle route repairs, but apparently "localism" doesn't extend to allowing local government to increase taxes more than Whitehall permits without holding a punitively-expensive referendum stacked against them.
 

EasyPeez

Veteran
No.
Go and have a look at a few short videos on Youtube on friction for high school and university students. It is actually quite fascinating. Friction is NOT dependent on surface area so a bigger contact patch will not move the breaking point. This breaking point is where static friction becomes kinetic friction. It is not affected by surface area because if you use a smaller area (contact patch) under the same object, the pressure increases. As the pressure increases, so the friction increases. It is an almost linear relationship. That is the fundamental principle of friction. My example above was a very special case. What I did by greasing/oiling a piece of the contact patch was to decrease the effective size of the contact patch without increasing the area. A kind of cheating if you like. My explanation is wonky, come back to me if you don't get it. I'll try and think of a better analogy.

Again, thanks for taking the time to offer such a thorough explanation.

In relation to the former, I understand what you are saying and no further analogy is needed. I had no idea of the linear r/ship between contact area and pressure when it comes to friction, so now I get why my ostensibly common-sense hypothesis becomes bunkem in the face of actual science!

And in relation to the latter, I can see how the same principles hold. I am only really interested in the tarmac riding as I already understood the basic gist of how reducing pressure can increase friction on rougher/softer terrains and ride those much more rarely (and on knobblies) anyway.

All that said, and while I don't doubt your explanation in the slightest and feel I have learned plenty, my instincts still tell me that a 35mm semi-slick tyre run at 75psi will hold onto a wet corner better than a 28mm slick at 95psi! I think we need to find a willing volunteer with a Gopro and a wet road to settle this once and for all in my mind....
 
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All that said, and while I don't doubt your explanation in the slightest and feel I have learned plenty, my instincts still tell me that a 35mm semi-slick tyre run at 75psi will hold onto a wet corner better than a 28mm slick at 95psi! I think we need to find a willing volunteer with a Gopro and a wet road to settle this once and for all in my mind....

Instinct is hard to overcome. That's why quantum mechanics is so daunting... as well as stereotyping and a bunch of other social evils.
 

Ajax Bay

Guru
my instincts still tell me that a 35mm semi-slick tyre run at 75psi will hold onto a wet corner better than a 28mm slick at 95psi!
If we're going to find someone to do that test, to take the same weight, if the 28's at 95psi, the 35 should be at 63psi ish.
 

Ajax Bay

Guru
A little bird tells me that very slightly damp surface is better than a dry one, for grip! (Unfortunately it's not just a little damp outside; it's wet, and I'm wimping out of my ride this lunchtime.)
 

ColinJ

Puzzle game procrastinator!
There is a valid issue here. A rider who is in control, and feels it, will be smoother than one who is nervous about loosing grip. It is probable that the more nervous ride is more likely to contribute to their own downfall.
OTOH, someone who puts excessive trust in a tyre's tread/width/pressure/compound's ability to cope with dicey conditions is more likely to come a cropper than someone who doesn't!
 

EasyPeez

Veteran
If we're going to find someone to do that test, to take the same weight, if the 28's at 95psi, the 35 should be at 63psi ish.
Sounds like we have a volunteer to me...
 
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