MTB Tire Direction

[shrubber]

Mmmmmm, interesting......

 

What effect would tire pressure have on grip?

 

I run relatively high (higher end of the recommendations) due to my weight (pinch flats/snakebites) and to minimise hard surface/gravel/tar rolling resistance.

 

Am I barking up the wrong tree here? 

[nochain]

You want grip on the front tyre' date=' not traction. If you go into a corner you want the wheel to grip on the sides not have for resistance when going in a straight line.

 

But I can be wrong, I did not go get my degree from www.smartassuniversity.com

 

 

[/quote']

 

Mampara, grip and traction is the same thing. There is no way of differentiating between them in science and they use the same units when measured. Lefty did a nice description of grip/traction vs adhesion.

 

The rolling resistance of a tyre is a function of the thickness of the rubber, which includes the tube, sidewall (with its fibres) and thread. It is not a function of its tread pattern except for extreme cases which don't apply here.

 

Should a tyre be a bit bald in the centre, that section will have lower rolling resistance than other sections where there is still a lot of rubber left, but since rolling resistance has nothing to do with traction, it is irrelevant in our debate.

 

 

So would the tread pattern have a different effect on traction when cornering versus straight line traction??

[Johan Bornman]

Johann you are very funny some times . But maybe we should look at the nobbly next to the swiss cross and decide it direction gonna change the traction ? Oooo wait you already explained that it doesn't .

 

Well, yes we did, especially in the previous word war on traction here on the Hub some weeks ago.

 

If you look at Larssen's recommendation on the tyre with that pattern throughout (can't remember its name now), you'll notice that it should be placed in such a way as to reduce traction - by the standards and understanding proposed here. In other words, the leading edge is the ramped edge that suggests slipping instead of gripping.

 

The thing is, mechanical traction where to shapes interlock perfectly, is an extremely random notion. Just think of hte randomness of a dirt or tar road and try and imagine how many times we'll get perfect interlocking. Very little.

 

Luckily, traction is not dependent on mechanical interlocking but by friction. Friction is determined by the rubber itself, the surface it runs on, the downforce on the wheel and loose gravel rolling about acting as ball bearings between the rubber and substrate.

 

The only reason Larssen has that ramp on that knobbly is to reduce noise. It softens the leading edge. However, if like me you wildly experiment and damn the consequences, you'll discover that riding it the other way around causes a buzz on tar roads. I couldn't distinguish the difference on dirt. Soon the false leading edge is worn away and looks just like the intended leading edsge - ramped. Traction is not compromised.

 

Humour always softens these things a bit.

 

[Mellow]

Im not left or right brain minded - i have no brain.

 

This is why I had to do a test a couple of months back on the Larsen and Crossmark to look at the effect of changing the tyre around (rotation direction). You smart guys can explain the result, im happy with what ive learnt.

 

Ive noticed that i kick-up a noticable amount more gravel and water when turning it in the opposite direction than shown.

 

Hope this helps 

[Wyatt Earp]

If the leading edge is tapered to eliminate noise, then why don't they taper both sides ???????

Logically if it makes a noise on the TAR, and we are not talking roadbike tires here, then obviously there has to be a different effect.

Maxxiss would love to see your thesis.

[Johan Bornman]

Im not left or right brain minded - i have no brain.

This is why I had to do a test a couple of months back on the Larsen and Crossmark to look at the effect of changing the tyre around (rotation direction). You smart guys can explain the result' date=' im happy with what ive learnt.

Ive noticed that i kick-up a noticable amount more gravel and water when turning it in the opposite direction than shown.

Hope this helps  [/quote']

 

Interesting observation and from a cursory glance I agree on the water issue but don't understand why it should shoot up more gravel in one direction and not in the other.

 

The way the Larssen grips and flings gravel has nothing to do with the leading edge ramp but with the distance the knobs are spaced - gravel size distance. At the contact patch, the tyre is spread out like your toes when walking barefoot. Gravel enters the grooves. As it rotates out of the contact patch, the tyre contracts sideways and holds the gravel lightly but not enough to overcome centrifugal force. It is then flung out into your wheelsucker's eye by that centrifugal force.

 

I hate riding behind Larssens.

 

 

 

 

[Loon]

Give em stick Summit... LOL

Good morning comedy.

[Wyatt Earp]

Im not left or right brain minded - i have no brain.

This is why I had to do a test a couple of months back on the Larsen and Crossmark to look at the effect of changing the tyre around (rotation direction). You smart guys can explain the result' date=' im happy with what ive learnt.

Ive noticed that i kick-up a noticable amount more gravel and water when turning it in the opposite direction than shown.

Hope this helps  [/quote']

 

Mellow, this type of experiment in my opinion is what produces fact, and not hearsay, nice post.

 

[Johan Bornman]

  

<?: PREFIX = O />

This particular tyre's predecessor didn't have the Swiss Cross since obviously the scientists at the lab haven't yet discovered the superior properties of traction on the Swiss flag. 

 

 

It's a neutral tread.

 

Typical me, I wanted to reply and ask you to explain but....slapping my forehead.... I smile.

[markStockton]

 

Mmmmmm' date=' interesting......

 

What effect would tire pressure have on grip?

 

I run relatively high (higher end of the recommendations) due to my weight (pinch flats/snakebites) and to minimise hard surface/gravel/tar rolling resistance.

 

Am I barking up the wrong tree here? 

[/quote']

 

Yes and no, Schwalbe did a study that indicated that there was not a significant increase in rolling resistance when running at a lower tire pressure, the lower preasure gives you much more grip on loose surfaces and sand,  however if you are running tubes you need to keep the pressure slightly higher to avoid pinch flats.

 

I run my tires alot softer than I used and apart from a wobbly feeling at the back on tar or really hard surfaces, much preffer the results.

 

 

 

 

[TNT1]

 

 

it applies to motorbikes as well.

Go around corner and allow the back wheel to slide a bit' date='

[/quote']

 

Yes, it's called "backing it in" Here's how to do it, for a demo, feel free to join me on my commute home this evening

 

 

 

Get the bike going reasonably fast (4th or 5th gear) with PLENTY of

room to spare at the end of the parking lot or wherever you are, Now

 

WITHOUT allowing the bike to engine brake or decellerate pull the

clutch in and downshift 2 gears quickly and just as quickly modulate

the clutch (release it) to about half pull (there about) while

"covering" the rear brake, (meaning apply just enough rear brake to

work together with the clutch to brake the rear tire free.

 

 

 

Now the tricky part is in understanding what is really happening here,

The bike is traveling at speed (X) and the rear wheel is rotating at a

speed constant with speed (X). So when you downshift and cover the rear

brake while the forward speed of the bike is still (X) the rear wheel

rotation speed drops well below that (X) and breaks free and the result

is a slide, up to the point where the bike slows down to the same speed

relative to the rear wheel rotation, then the rear wheel comes back in

line with the front.

 

 

 

In a straight line all you will really feel is the rear wheel dancing

around a bit behind you but the first lesson is to get the tire/rear

wheel to break free so that you can grasp the concept.

 

 

 

Once you have that down you can then move to the next lesson which

involves counter steering in concert with all of the above principles.

This is done exactly the same way and with the exact same approach

however the idea is to slide the bike in as close the the apex of the

turn as possible, that concept is really the hardest to perfect because

you have to train your mind to go alot deeper into the corner prior to

sliding or you UNDER shoot the corner and apex too soon.

 

 

 

Counter steering is an ABSOLUTE in my opinion when sliding on pavement

for 2 very important reasons (1) you are physically PUSHING down (away

from you) on the opposite grip which forces the bike to lean which then

gets you onto the edge of the (rear) tire and (2) gets the front tire

pointed into the direction of the slide.

 

 

 

The biggest mistake you can make here is to stay on top of the bike

during this process, you need to get down into the "hole" with your

upper body with the majority of your weight as low as you can get it

while still maintaining absolute control of the bike. If it hooks up

and you are on top the result could be a high side.

 

 

 

The only variable I can think of would be the number of gears you need

to downshift in order to get YOUR bike slide at any given speed, also

another note to make is to be very aware of chatter and hop during the

slide, if the rear wheel starts hopping pull the clutch in slightly and

back off the brake a little.

 

 

 

Take it easy at first and learn to get the rear wheel to break free in a straight line first.

 

 

 

I am assuming with all of this you will be trying this technique on a 4

stroke machine? 2 strokes are a lot harder to perfect due to the lack

of engine braking.

 

 

 

The speed with which you "Dump/Modulate" the clutch will have a BIG

impact on how this process works or doesnt work but youll figure it out.

 

I hope you remember to keep the speed up

when you get to the sliding into corners part, the slower you go the

more tendancy there is for the bike to hook up and high side you. Have

fun.

 

http://vsmr.net/albums/SumoThai/IMG_6620.sized.jpg

 

 

TNT12008-10-02 01:29:34

[Mellow]

 

Im not left or right brain minded - i have no brain.

 

This is why I had to do a test a couple of months back on the Larsen and Crossmark to look at the effect of changing the tyre around (rotation direction). You smart guys can explain the result' date=' im happy with what ive learnt.

 

Ive noticed that i kick-up a noticable amount more gravel and water when turning it in the opposite direction than shown.

 

Hope this helps  [/quote']

 

Mellow, this type of experiment in my opinion is what produces fact, and not hearsay, nice post.

 

 

Sure, just sharing. I do think there is truth in what Johan Bornman replied, i just dont know, to many variables for me to point at one thing.

 

[Johan Bornman]

 

So would the tread pattern have a different effect on traction when cornering versus straight line traction??

 

No it wont. The co-efficient of friction is not dependent on tread pattern but as I explained, on rubber type, the grain of substrate, downforce etc etc. The rule to apply is that tread pattern has no effect on traction unless you have a perfect mechanical interlock.

 

Therefore the absolute traction will be equal in both directions if all things are equal. However, downforce reduces significantly when we corner since our weight is "diluted" by the leaning angle and therefore all tyres (irrespective of tread pattern) will have less sideways traction (but only when cornering) than forward traction on a cornering bicycle.

 

 

 

[Johan Bornman]

If the leading edge is tapered to eliminate noise' date=' then why don't they taper both sides ??????? [/quote']

 

Because only the leading edge strikes the substrate. It's like running - your heel strikes the ground and your toe pushes away.

 

 

Logically if it makes a noise on the TAR' date=' and we are not talking roadbike tires here, then obviously there has to be a different effect.

 

[/quote']

 

Perhaps you want to rephrase that sentence. I don't understand it.

 

[Johan Bornman]

Mmmmmm' date=' interesting......

 

What effect would tire pressure have on grip?

 

I run relatively high (higher end of the recommendations) due to my weight (pinch flats/snakebites) and to minimise hard surface/gravel/tar rolling resistance.

 

Am I barking up the wrong tree here? 

[/quote']

Yes and no, Schwalbe did a study that indicated that there was not a significant increase in rolling resistance when running at a lower tire pressure, the lower preasure gives you much more grip on loose surfaces and sand,  however if you are running tubes you need to keep the pressure slightly higher to avoid pinch flats.

I run my tires alot softer than I used and apart from a wobbly feeling at the back on tar or really hard surfaces, much preffer the results.

 

I doubt any study will come to that conclusion. As air pressure increases, rolling resistance decreases. Perhaps the escape valve on your sentence is the use of "significantly". I think the difference is significant. That's just the nature of the beast.

 

I agree that traction on irregular surfaces improves with a decrease in air pressure and here the cause is obvious - the tyre moulds itself over something irregular and making that lot slip will require lots more force.

 

I had a look at the Schwalbe study at the time and I don't like their testing method. It is virtually impossible to measure something like rolling resistance by repeatedly riding the same irregular path. You just cannot do that accurately enough.

 

The only accurate way to measure rolling resistance is on a smooth surface such as a steel drum. That'll give you a base to work from and any irregularities you throw at the tyre will just add on top of the base. But at least the base measurements for various pressures are accurate.

 

 

 

 

 

[Canaris]

Interesting reading.

 

But make to the initial remarks:

 

Why should you respect the directional marking on the tyres:

 

Well the clever developers designed it that way.  As some one said, if you put LarsenTT on backwards you will wear the leading edge down to look like it should be.  So way bother putting it on counter directional if you only going to wear the tyre out faster?

 

Secondly, why more grip is needed on the front wheel?  Because you steer with the front wheel!  Obviiously you can slide the back wheel to change direction (but that would meen you would need less, not more lateral grip on the back wheel).  The front wheel needs the lateral grip because you change direction (via steering) with the front wheel.  If your weight is on the front wheel and you don't have grp there the front wheel faces the danger of washing out when you turn.

 

(Now I await at least one flaming and two scientfic studies refuting of what I see as common sense)