A hill too far
Discussion
I live in an up/down country environment with narrow lanes and a lot of small but steep gradients.
Yesterday was going to do the school pick up, and travelling down one of these roads with a icy hill facing me.
Gave it a bit of well heading toward the hill, but halfway up the tyres were unable to hold grip, and I was left spinning and unable to make the wheel go slow enough to gain traction. Tried a couple of times, the last of which was some very lary snaking, so I thought I'd better call it a day.
The small audi behind me thought this was very funny till I had to explain to him he'd have to reverse cos I was unable to go forward and would have to find another way to the school.
Being stationary on a small country lane is very bad if you stay in one place more than a few minutes as a traffic jam ensues very quickly. Invariably ending with one or two people who either won't or can't reverse.
So I was thinking, reduce the pressure in the tyres, carry a bag of potatoes in the boot, winter tyres on a Cerb, change to a narrow winter width of tyre. Anyone else got a solution?
Yesterday was going to do the school pick up, and travelling down one of these roads with a icy hill facing me.
Gave it a bit of well heading toward the hill, but halfway up the tyres were unable to hold grip, and I was left spinning and unable to make the wheel go slow enough to gain traction. Tried a couple of times, the last of which was some very lary snaking, so I thought I'd better call it a day.
The small audi behind me thought this was very funny till I had to explain to him he'd have to reverse cos I was unable to go forward and would have to find another way to the school.
Being stationary on a small country lane is very bad if you stay in one place more than a few minutes as a traffic jam ensues very quickly. Invariably ending with one or two people who either won't or can't reverse.
So I was thinking, reduce the pressure in the tyres, carry a bag of potatoes in the boot, winter tyres on a Cerb, change to a narrow winter width of tyre. Anyone else got a solution?
[/John Inman]
Brummmie said:
Thinner tyres will give more grip as they increase lbs/square inch, like snow tyres in rallying.
Not this again - changing the width of tyres only changes the shape of the contact patch, not the size of the contact patch (for a given vehicle weight and tyre pressure).A longer, thinner contact patch may be more successful at finding longditudinal grip, either by cutting through a low-friction layer (e.g. on snow), or by exploiting friction inconsistancies on the road surface (e.g. on patchy ice or a road surface with high mechanical interlock).
You need a pair of these;
http://www.roofbox.co.uk/autosock/
Just got a set for the rears on the Cerb prior to my trip to Switzerland. Arrived today so will trial fit them tomorrow, but look very useful indeed.
http://www.roofbox.co.uk/autosock/
Just got a set for the rears on the Cerb prior to my trip to Switzerland. Arrived today so will trial fit them tomorrow, but look very useful indeed.
Nefarious said:
Brummmie said:
Thinner tyres will give more grip as they increase lbs/square inch, like snow tyres in rallying.
Not this again - changing the width of tyres only changes the shape of the contact patch, not the size of the contact patch (for a given vehicle weight and tyre pressure).A longer, thinner contact patch may be more successful at finding longditudinal grip, either by cutting through a low-friction layer (e.g. on snow), or by exploiting friction inconsistancies on the road surface (e.g. on patchy ice or a road surface with high mechanical interlock).
JensenA said:
Nefarious said:
Brummmie said:
Thinner tyres will give more grip as they increase lbs/square inch, like snow tyres in rallying.
Not this again - changing the width of tyres only changes the shape of the contact patch, not the size of the contact patch (for a given vehicle weight and tyre pressure).A longer, thinner contact patch may be more successful at finding longditudinal grip, either by cutting through a low-friction layer (e.g. on snow), or by exploiting friction inconsistancies on the road surface (e.g. on patchy ice or a road surface with high mechanical interlock).
No it doesn't it only changes the shape of the contact patch. Try it with some ballons, weights and a sheet of glass.Edited by ro_butler on Friday 12th December 18:01
ro_butler said:
JensenA said:
Nefarious said:
Brummmie said:
Thinner tyres will give more grip as they increase lbs/square inch, like snow tyres in rallying.
Not this again - changing the width of tyres only changes the shape of the contact patch, not the size of the contact patch (for a given vehicle weight and tyre pressure).A longer, thinner contact patch may be more successful at finding longditudinal grip, either by cutting through a low-friction layer (e.g. on snow), or by exploiting friction inconsistancies on the road surface (e.g. on patchy ice or a road surface with high mechanical interlock).
OK, Physics 101:
Normal force excerted upwards by the ground = total weight of the car
Normal force excerted upwards by the ground = pressure in the tyres x area over which that pressure acts (i.e. the contact patch)
Ergo, unless you change the weight of the car or the pressure in the tyres, the size of the contact patch cannot change. If you halve the width, the tyre will deform to double the length.
[Pedant protection]Actually, in the real world it's not quite true that a 50% reduction in width will equal a 100% increase in length, due to small contributions from the stiffness of the sidewall, inconsistancies in the way the tyre deforms, and the fact that neither the road nor the tyre are perfectly smooth. But it's pretty close [/pedeant protection]
Normal force excerted upwards by the ground = total weight of the car
Normal force excerted upwards by the ground = pressure in the tyres x area over which that pressure acts (i.e. the contact patch)
Ergo, unless you change the weight of the car or the pressure in the tyres, the size of the contact patch cannot change. If you halve the width, the tyre will deform to double the length.
[Pedant protection]Actually, in the real world it's not quite true that a 50% reduction in width will equal a 100% increase in length, due to small contributions from the stiffness of the sidewall, inconsistancies in the way the tyre deforms, and the fact that neither the road nor the tyre are perfectly smooth. But it's pretty close [/pedeant protection]
Nefarious said:
Ergo, unless you change the weight of the car or the pressure in the tyres, the size of the contact patch cannot change. If you halve the width, the tyre will deform to double the length.
But surely when you use narrow tires you increase the pressure to offset the 'squashing' of the tires?Or you could stick some mud terrains on. I have a set of 33 inch muds you could borrow but clearanc may be an issue.
Nefarious said:
OK, Physics 101:
........... the size of the contact patch cannot change. If you halve the width, the tyre will deform to double the length.
How can it? The Tyre is round, and it's attached to a rigid Alloy wheel. Maybe you are theorising and ignoring the practicalities of the real world............ the size of the contact patch cannot change. If you halve the width, the tyre will deform to double the length.
Nefarious said:
OK, Physics 101:
Normal force excerted upwards by the ground = total weight of the car
Normal force excerted upwards by the ground = pressure in the tyres x area over which that pressure acts (i.e. the contact patch)
Ergo, unless you change the weight of the car or the pressure in the tyres, the size of the contact patch cannot change. If you halve the width, the tyre will deform to double the length.
[Pedant protection]Actually, in the real world it's not quite true that a 50% reduction in width will equal a 100% increase in length, due to small contributions from the stiffness of the sidewall, inconsistancies in the way the tyre deforms, and the fact that neither the road nor the tyre are perfectly smooth. But it's pretty close [/pedeant protection]
Nope, I think you are wrong. If the tyre was a balloon I'd agree with you, but I think as your last paragraph seems to intimate, the size width and tyre wall are probably more powerful influences than the pressure.Normal force excerted upwards by the ground = total weight of the car
Normal force excerted upwards by the ground = pressure in the tyres x area over which that pressure acts (i.e. the contact patch)
Ergo, unless you change the weight of the car or the pressure in the tyres, the size of the contact patch cannot change. If you halve the width, the tyre will deform to double the length.
[Pedant protection]Actually, in the real world it's not quite true that a 50% reduction in width will equal a 100% increase in length, due to small contributions from the stiffness of the sidewall, inconsistancies in the way the tyre deforms, and the fact that neither the road nor the tyre are perfectly smooth. But it's pretty close [/pedeant protection]
Jens right, if the contact other factors other than those you mentioned are irrelevent then there'd be no point in slicks for santa pod. We should just have bike tyres with better compound
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