MTB Tire Direction

[markStockton]

 

No-one I know can spin a rear wheel (even a slick) whilst apply full downforce (i.e in the sitting position) on their bike.

 

Have you actually spent much time on an MTB on a technical course with a fair amount of climbing? I can definitely spin the back, and I probably have 1/3 of the power of Andrew Mc and weigh 20kg's more!!!

 

I also noticed LBB loosing traction with every pedal stroke up a climb at Rietvlei last time I saw him.

 

[Canaris]

There must be a way to test all this !! (in the real world )

 

Yes there is. You'd want to test two things which are core to what we are discussing here:

 

1) Slip-out angle. It is measured as a simple angle with a given downforce.

2) Co-efficient of friction in a straight line. (It's been called grip and traction here' date=' all the same thing measured the same way. There is no unit for the coefficient of friction, it is merely a coefficient. But that's not English in your book.

 

Forget about doing a riding test, that's just too messy. You'll have to do the tests statically.

 

For the co-efficient of friction, I suggest you cut a piece out of your mate's directional tyre. A length of about 100mm should do the trick.

 

Flatten it and nail it to a wooden board. Load the wooden board with a couple of bricks and attach a string to each end of the board. Now pull the board on a uniform surface with one of those fishing scales and get a reading. Pull it from the other side and get another reading. Do that several times, throw away the extreme results at either end and average the bunched results. See if it differs significantly from left to right.

 

For the slip-out angle it'll be a bit more difficult. You'll have to get two tyres where the surface area and depth of the two sets of knobblies differ in looks but are exactly the same otherwise.

 

Then you'll have to apply a known force to each wheel and slowly tip it (on your preferred surface) until it slips out. Measure that angle and compare the two after you've taken away the "noise" in the experiment as described above.

 

This would be a real world test. I've never seen any tyre manufacuter perform and publish the results of this test.

 

 

[/quote']

 

On a small point of correction.  Your test does not simulate (check I have fixed the spelling) real world conditions.  TYre are not flattened onto a box in real world conditions (they are round.  Pies are not square).  So the contact surface will be considerably different when the tyre is Flattened out.

 

Secondly, tyre are normally rolled over obstacles and srufaces and not dragged (unless you are braking hard, but then you will be over the handle bars)

 

SO to simulate treall conditions you should use the complete wheel connected to a improvised cart which is then rolled over various surfaces at diferent speeds and angles.  Data is then collected from how far the wheel rolls or how much dirt is displaced ext.

 

I know you ae a stickler for correctness, and this is why I propose that your expeiment won't measure what you want it to ( relevancy)

[TNT1]

 

No-one I know can spin a rear wheel (even a slick) whilst apply full downforce (i.e in the sitting position) on their bike.

 

Have you actually spent much time on an MTB on a technical course with a fair amount of climbing? I can definitely spin the back' date=' and I probably have 1/3 of the power of Andrew Mc and weigh 20kg's more!!!

 

I also noticed LBB loosing traction with every pedal stroke up a climb at Rietvlei last time I saw him.

[/quote']

 

Ever ridden up Magoebaskloof in the wet? On a road bike?

 

[Johan Bornman]

So if tread pattern has no influence on grip/traction when cornering how do you increase grip?Are you only refering to the Pattern of the tread and not the tread itself' date='more tread(bigger) more grip?

 

 

[/quote']

You increase traction by:

 

Providing more downforce (can't be done on a bicycle)

Improving the coefficient of friction on the rubber compound

Improving the stability of the substrate (less loose gravel/mud)

Making the texture of the substrate more like sandpaper.

For a given pattern - for argument sake, say a raised Z shape all over the tyre - it doesn't matter how you orient it with respect to travel. You'll have the same traction.

As the substrate becomes softer, the depth of the tread becomes more important. As Lefty describes it, the knobbly needs to have a paddling effect just like a paddle in a canoe. For a given size paddle, it doesn't matter how you orient it in the water. Clearly depth has an effect.

 

 

 

[Johan Bornman]

Ever ridden up Magoebaskloof in the wet? On a road bike?

 

Let me guess - your rear wheel slips.

 

Perhaps you missed the importance of downforce and my mention of remaining seated. As you stand and pedal up a steep hill, your weight shifts forward and the rear wheel looses traction due to lack of downforce. This has nothing to do with tread patterns or directionality.

 

[TNT1]

 

Ever ridden up Magoebaskloof in the wet? On a road bike?

 

Let me guess - your rear wheel slips.

 

Perhaps you missed the importance of downforce and my mention of remaining seated. As you stand and pedal up a steep hill' date=' your weight shifts forward and the rear wheel looses traction due to lack of downforce. This has nothing to do with tread patterns or directionality.

 

[/quote']

 

Well, it clearly has nothing to do with tread patterns, cause I've ridden that hill many times and the rear wheel slips, if standing OR sitting, on the road bike...

 

[Johan Bornman]

On a small point of correction.  Your test does not simulate (check I have fixed the spelling) real world conditions.  TYre are not flattened onto a box in real world conditions (they are round.  Pies are not square).  So the contact surface will be considerably different when the tyre is Flattened out.

 

Pies squashed by 80kgs of weight do tend to flatten. The contact patch is flat underneath. It is only the rest of the tyre that remains tubular during riding. I think this example is real-world. If you still disagree' date=' modify the shape of the wooden block at bit.

 

 

Secondly, tyre are normally rolled over obstacles and srufaces and not dragged (unless you are braking hard, but then you will be over the handle bars)

 

SO to simulate treall conditions you should use the complete wheel connected to a improvised cart which is then rolled over various surfaces at diferent speeds and angles.  Data is then collected from how far the wheel rolls or how much dirt is displaced ext.

 

I know you area stickler for correctness, and this is why I propose that your expeiment won't measure what you want it to ( relevancy)

 

You are confusing rolling resistance with traction. Go back and familarise yourself with the two. I have explained it.

 

Traction is static friction (stiction in shock abosorber terms). We are trying to measure the maximum reading on your scale just before the block and its tyre starts to move. As soon as it moves, the scale will give a smaller reading.

 

If you measure static friction on a given uniform surface, you know that reading will be the base factor in any reading obtained by worsening the surface.

 

Here's an example. If you measure the traction of the device on a smooth steel surface and you get a reading of A in the one direction and B in the other direction. If you now make that surface irregular by punching it neatly like a cheese grater (with unidirectional spiky bits) and you now measure the two directions again you'll get A+C and B+C.

 

For the purposes of our experiment C is unimportant, so you restrict the experiment to a smooth uniform surface knowing that anything else will simply be an additional bit.

 

If A was bigger than B, then A+C will not suddenly be smaller than B+C.

 

Remember, all we want to know is whether tyres are directional or, if traction changes if you reverse the tyre.

 

I suppose I could just have said that your cart will measure rolling resistance and my sled will measure coefficient of friction.

 

 

 

 

 

[Wyatt Earp]

  

 

Joke? youmade a joke? really? where? please show me.

 

So you don't have an arguement and now resort to the buddy club and length of service. Well if this has to be a dick swinging exercise then so be it.

 

In your mind the tyre marker is a god who cannot be challenged. Well heres a secret; Marketers lie [try to contain your horror at this revelation.]

 

mine is not a theory' date=' it's fact. Science fact, engineering fact.

 

Patents:

the only patents that are valid revolve around the compound formulation and noise reduction around the shape of the tread. it can be argued that noise is energy loss and therefore if you reduce it you infact save ex[end less energy. This applies on a tar road. On a gravel road, where MTB tyres are most use, it makes no difference because the substrate is compliant. So if you ride on slick rock or tar all the time then perhaps direction is important to minimise energy loss through noise. Here, in SA we ride on gravel road or sandy trail.

what benefit does a patent have in tread design? Marketing. It provides the customer with a "reason to believe" in the product. Its something the buyer can see and touch and they will believe everythng it says on the box. I'm sure if someone invented coffee scented tyres everyone would belive that the tyres will your coffee for you.

 

Motocross bike tyres have to cope with much higher acceleration, great weight per cm^2 and therefore the tread design here plays a bigger roll. On a bicycle it makes no difference as long as there is a paddle to provide the trust through soft soils. the surface area and depth are the biggest contributors.

 

read up on this, there is plenty of information on the WWW to support these facts.

[/quote']

Tsk.tsk.tsk you are an agressive little fella

As I said if you have been around lefty's long enough you would have understood

At least you have stopped lecturing me on headshocks.

I will now follow your lectures regarding tires, by the way which tire company do you own ?

The big WWW is full of opinions from idiots like us.

Have a good day sir.

 

[Johan Bornman]

Well' date=' it clearly has nothing to do with tread patterns, cause I've ridden that hill many times and the rear wheel slips, if standing OR sitting, on the road bike...
[/quote']

 

Look TNT, you have enough experience with mature debate to know that it is easy to find extreme examples to disprove just about anything. I did say ice-rinks excluded. Why force me to exclude a bed of ball bearings, a slimy shiny wet tar road, a conveyor belt in a vaseline factory and the slippy slide at Waterworld in Benoni.

 

There are plenty of situations where traction is extremely limited. Point remains, turning your tyre around under those (or any other) conditions will not suddenly return traction.

 

 

[intern]

 

  

 

Snip snip

 

The big WWW is full of opinions from idiots like us.

Have a good day sir.

 

 

C'mon guys. you're trying to have an argument that is vying for top spot in the 'how boring and pedantic can you get' competition (and I'm not saying that the competition isn't fierce, cause it is) Play nice!

 

[Wyatt Earp]

  

 

Snip snip

The big WWW is full of opinions from idiots like us.

Have a good day sir.

 

C'mon guys. you're trying to have an argument that is vying for top spot in the 'how boring and pedantic can you get' competition (and I'm not saying that the competition isn't fierce' date=' cause it is) Play nice!
[/quote']

Apologies there intern, I am done

Summit Cycles2008-10-02 04:47:39

[Loon]

Respek!

 

You oaks are too high strung...

Just put a freaking tyre on and go ride...

Or be like Canondale's marketing add. Epic on a CrossMax SLR...

Bet you those boys did not give thought as to which way the rims traction was...

 

[dirtrider]

WE done already ?? And here I am finking hard for the last hour to come up with something radical and new !

[TheLegend]

 

  

 

Snip snip

 

The big WWW is full of opinions from idiots like us.

Have a good day sir.

 

 

C'mon guys. you're trying to have an argument that is vying for top spot in the 'how boring and pedantic can you get' competition (and I'm not saying that the competition isn't fierce' date=' cause it is) Play nice!

[/quote']

 

but summit called lefty "aggressive little fella"!!!!!

 

[dirtrider]

Ja don't know bout the little part !

[Loon]

LOL...

 

I think Ysterman has left the buillding...

 

He is going to got put tyres on any direction and not give a hoot. He is just going to have fun riding.