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Old 07-03-10, 01:35 AM   #1
snafu21
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'More rubber on the road gives more grip' - discussion

Well?

Do fatter/ larger/wider tyres give more grip? If so, how do small-wheel folders, with their silly 'clown' wheels, actually manage not slide sideways from the face of the planet on every bend?

We need the truth, and we need it now.

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Old 07-03-10, 02:03 AM   #2
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http://www.autospeed.com/A_108915/cms/article.html
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Old 07-03-10, 02:16 AM   #3
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grip has 3 factors.

1: contact patch
2: tire profile
3: tire compound

pertaining to inline wheeled vehicles

fatter tires give a slightly wider
larger tires give an elongated
oval profile gives more in corners
box profile gives more in straights
softer compound give more
lower inflation pressure gives more

All bicycle tires are pretty much a circle in profile, the wider they are, the taller they are.
Wide gives both more width and diameter, using a small wheel with fat tires gives more contact patch all around than a larger wheel with narrower tires of the same diameter. To reflect this, wider tires are inflated to lower pressures, because the tires support more of the weight on their wider contact patch.

In addition to that, since there is additional distance between the rim and the road, the tire is allowed to deform more to the contours of the road. Even in bumpy places, the CoG of the bike isn't thrown up and down as badly, which suppresses the tendency for the rider to bounce and unweight the bike.

However, there are downsides to wider tires. Manufacturers are very keen on selling their high performance tires with softer compounds for narrow tires. There are a few exceptions, like the kojak, but overall there are very few performance wide tires.

Wider tires also don't cut through debris and mud on the road as well as a narrow tire. This is because the contact patch is fairly wide and tends to ride up, rather than plow. It's not like a narrow tire has a huge advantage for cutting through slop, but I would give it a slight edge in this regard. Overall it's better to just have wide tires with treads that will cut through slop even better than narrow tires or simply bite into the slop and ride over it. It's like a comparison between stabbing food with a spoon and fork.


There are also things to consider like the weight and aerodynamics, but for just grip, wider is better
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Old 07-03-10, 02:19 AM   #4
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Ah yes.
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Old 07-03-10, 02:37 AM   #5
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that article is not very useful to bike tires, since they're not designed the same.
car tires don't have to be round since there is no 'tilting' required
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Old 07-03-10, 05:52 AM   #6
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The only variable that should matter as far grip and stopping goes is the tire compound. As far as the ride is concerned there a definitely lots more factors. So to answer the questions as posed I would say no, it does not matter. The frictional force comes from the tire compound times the weight on the tire. The area of the patch does not matter just the pressure on that area. If the patch is smaller the pressure is greater. Amateur science at work.
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Old 07-03-10, 06:11 AM   #7
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It depends entirely upon whether the bike has dérailleur or internal geared hub.
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Old 07-03-10, 06:13 AM   #8
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I am looking for a very fast smooth light puncture-proof 16" tire that also has small spikes that are normally retracted but which can be deployed with a remote control button mounted on the stem

I need these for cornering over painted pedestrian crosswalk lines under wet conditions

If anyone knows a source for these let me know
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Old 07-03-10, 07:10 AM   #9
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It depends entirely upon whether the bike has dérailleur or internal geared hub.
Ha ha ha VERY FUNNY
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Old 07-03-10, 12:42 PM   #10
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I am looking for a very fast smooth light puncture-proof 16" tire that also has small spikes that are normally retracted but which can be deployed with a remote control button mounted on the stem

I need these for cornering over painted pedestrian crosswalk lines under wet conditions

If anyone knows a source for these let me know
I had that idea when I was in high school... after I watched a lot of bond films.
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Old 07-03-10, 04:51 PM   #11
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Real World: The wife is far more comfortable on gravel and dirt bike paths with the 1.75" Kendas on our Pocket 8's than the 1.35" Marathon Plus tires on our custom Fridays. I'd say the same.

Lou
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Old 07-05-10, 05:54 AM   #12
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So: res ipsa loquiter: larger people have more grip.

?
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Old 07-05-10, 06:26 AM   #13
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So: res ipsa loquiter: larger people have more grip.

?
True but then the forces being resisted are proportionately higher since mass is higher.
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Old 07-05-10, 08:51 AM   #14
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So: res ipsa loquiter: larger people have more grip.

?
although weight does play a factor, there's also ground pressure to factor in.
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Old 07-05-10, 09:53 AM   #15
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although weight does play a factor, there's also ground pressure to factor in.
Ground pressure is the weight divided by the contact patch area. But the contact patch area does not have an effect on grip. Lateral force at the tire is the weight time the coefficient of friction of the tire which is a characteristic of the tire compound.
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Old 07-05-10, 06:49 PM   #16
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Ground pressure is the weight divided by the contact patch area. But the contact patch area does not have an effect on grip. Lateral force at the tire is the weight time the coefficient of friction of the tire which is a characteristic of the tire compound.
what about on loose ground?
I know I want really fat tires for snow and mud.
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Old 07-06-10, 12:12 AM   #17
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^^^^

I understand (?) that for loose surfaces, we move from 'grip' (downforce x C. of F.) to 'traction': tyres with teeth. The downhill MTB boys seem to be in no agreement over tyres either.

The limitation on a folder is what will fit in the forks and frame, of course.
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Old 07-06-10, 03:52 PM   #18
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Lateral force at the tire is the weight time the coefficient of friction of the tire which is a characteristic of the tire compound.
That's not true. The friction force is the weight times the coefficient of friction, but one of the main reasons for using pneumatic rubber tires is because the lateral force at the tire (ie "the traction") consists of more than just friction.

The road is supposed to dig into the tire and grab/push it mechanically and consequently tire grip depends no more on friction than does a roller chain or a toothed belt.

Last edited by chucky; 07-06-10 at 03:56 PM.
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Old 07-06-10, 07:38 PM   #19
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The road is supposed to dig into the tire and grab/push it mechanically and consequently tire grip depends no more on friction than does a roller chain or a toothed belt.
Is it the same way on a velodrome floor?
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Old 07-11-10, 01:48 PM   #20
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I remember when I first got my Brompton S2L-X and went out for a ride. I was riding on the sidewalk in Japan going slow and all of a sudden my tires (Schwalbe Stelvios) went into a small groove along the side of the side walk and I couldn't get out so I ended up crashing onto the dirt. Those tires are not meant to be used on rough roads or sidewalks. I use the Marathon Racers now and they are ten times better in regards to speed (because my bum doesn't hurt I can keep going fast) and safety.
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Old 07-14-10, 08:08 AM   #21
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Is it the same way on a velodrome floor?
Dunno, but I think if traction were an issue in the velodrome then they'd change the surface rather than the bike.

OT: This is something that plagues all bike racing. First all barriers to speed are eliminated by changing the course (ie cheating) and only then do the bicycles themselves begin to be optimized for speed. Consequently race bikes are often quite slow because they fail to address the most significant hinderances to speed in the real world.
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Old 07-14-10, 06:37 PM   #22
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That's not true. The friction force is the weight times the coefficient of friction, but one of the main reasons for using pneumatic rubber tires is because the lateral force at the tire (ie "the traction") consists of more than just friction.

The road is supposed to dig into the tire and grab/push it mechanically and consequently tire grip depends no more on friction than does a roller chain or a toothed belt.
OK, so why is it one type tire has more grip than another?
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Old 07-14-10, 06:51 PM   #23
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Soft rubber compound that will add to grip, at the expense of quick wear, and perhaps rolling resistance .

GP motor bike with abundant HP may use that sticky compound to corner at higher speeds , but
Humans put out a few hundred watts, at most, well below even 1HP.
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Old 07-23-10, 05:21 PM   #24
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Gravity is a weighty issue here.
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Old 07-24-10, 04:47 AM   #25
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Friday morning, on racing bike, fast corner, didn't see wet patch,
not enough rubber on the road........whoops, road rash, destroyed arm and leg warmers............hard and painful wound scrubbing under the shower...Oh joy.
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