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mechanical grip

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anyone on here have any cut and dry advice on how to achieve better mechanical grip with a motorcycle?

basically just looking for a list of areas of the bike that effect mechanical grip (i.e. shocks, tires, tire pressure, etc), and how each one will positively and negatively effect mechanical grip.

thanks in advance :thumbsup:

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Eh... Normally 'mechanical grip' is just called traction, since we really don't deal with chemical grip or anything like that.

1. Tire appropriate for terrain - soft type tire for soft ground, hard for hardpack/rock, paddle in sand, SM for asphalt, snow tire with spikes for ice, etc

2. Shock preload/compression/rebound set for terrain and weight. Forks also preload/compression/rebound set for terrain and weight.

3. Lower tire pressure on softer terrain, higher on harder terrain, GENERALLY!

4. Rider control of throttle/clutch - too much power breaks traction, as can power delivery.

5. Rider body position - where you throw your weight matters, i.e. leg forward in corners to help weight front wheel from washing out.

6. Rider input. Easily the greatest factor.

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Eh... Normally 'mechanical grip' is just called traction, since we really don't deal with chemical grip or anything like that.

1. Tire appropriate for terrain - soft type tire for soft ground, hard for hardpack/rock, paddle in sand, SM for asphalt, snow tire with spikes for ice, etc

2. Shock preload/compression/rebound set for terrain and weight. Forks also preload/compression/rebound set for terrain and weight.

3. Lower tire pressure on softer terrain, higher on harder terrain, GENERALLY!

4. Rider control of throttle/clutch - too much power breaks traction, as can power delivery.

5. Rider body position - where you throw your weight matters, i.e. leg forward in corners to help weight front wheel from washing out.

6. Rider input. Easily the greatest factor.

I look at mechanical grip as more of a static mechanical grip. I dont want to take into consideration anything such as body position, rider input, or throttle/clutch control (although i do agree those are traction factors). I'm looking for ways, from a setup standpoint, that you can do to increase the amount of grip your bike would have on the ground right out of the box.

I understand shock/spring settings, tire selection, and tire pressure would all be factors, but what about frame design and such. Is there particular geometry that lends itself to create an optimum rake and trail for motocross riding vs. say trail riding vs. supercross?

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The obvious flaw in that is that a motorcycle is not a static object when in use.

neither are professional purpose built race cars, but race engineers use mechanical grip ,"traction", as a large factor in the setup for the car for every single practice, qualifying session and race.

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neither are professional purpose built race cars, but race engineers use mechanical grip ,"traction", as a large factor in the setup for the car for every single practice, qualifying session and race.
True, but in a dynamic, not static sense.

You may be referring to traction in steady state conditions such as a skid pad, where there is no active steering or chassis shifts. The vehicle is still in motion, but there are no changes in loads taking place.

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Just making a clarification here. The contact patch of a tire while rolling (not sliding) is in a static friction condition. A sliding tire (i.e. supermoto backing it in) will adhere to the dynamic grip rules

Another word for grip is friction. Friction is a simple equation Ff=N*Cf

or the Force of friction = the Normal force times the Coefficient of friction.

So, the simplest way to get more mechanical grip is to eat a big meal before riding or add weights to your bike. This will add to the normal force, and therefore more foce due to friction. But this will hurt you in other ways (more difficult to turn, longer stopping distances, etc)

Simple ways to increase the Coefficient of friction would be to add contact patch (lower tire pressure), or increase the stickiness of the tires (tire warmers)

There are ways to use suspension geometry to add normal force to help mechanical grip in certain situations(anti-squat and anti-dive), but most modern motorcycles already do a very good job of balancing this with ridability.

It may be possible to change geometry to get more grip where you want it but the suspension will suffer in other areas (i.e. a bike that squats the rear suspension dramatically under braking, but that same bike can't hit a speed bump without bouncing the rider off)

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The fact that the center of the tire contact patch is, however briefly, static is true enough, but the so called "static" traction condition is only remotely similar to the conditions under which a rolling tire operates. within the tire alone, as the next inch of tread rolls into contact with the ground, the cornering load is transferred to it from the previous inch, and the tread and tire carcass flex and twist in response, generating a scrub angle that differs from the direction the wheel is pointed even if there is no loss of adhesion between the tire and the ground surface.

Then, you have to add to that that maximum traction between tire and pavement occurs at something like a 12% slip.

In dirt it gets even more complicated, since surface adhesion often accounts for very little actual traction, depending instead on the tire digging into the soil and bearing against it. That brings the cohesion of the soil into the matter, and again, maximum bite is achieved at some varying degree of wheel slip.

It's true, as you say, that to an extent, the whole thing can be analyzed as if the vehicle were static and being loaded laterally as if cornering, and many of the same things that would improve traction under those conditions do help the bike (or car) when underway, actual cornering, braking, and accelerating are in no sense static situations.

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The fact that the center of the tire contact patch is, however briefly, static is true enough, but the so called "static" traction condition is only remotely similar to the conditions under which a rolling tire operates. within the tire alone, as the next inch of tread rolls into contact with the ground, the cornering load is transferred to it from the previous inch, and the tread and tire carcass flex and twist in response, generating a scrub angle that differs from the direction the wheel is pointed even if there is no loss of adhesion between the tire and the ground surface.

Then, you have to add to that that maximum traction between tire and pavement occurs at something like a 12% slip.

In dirt it gets even more complicated, since surface adhesion often accounts for very little actual traction, depending instead on the tire digging into the soil and bearing against it. That brings the cohesion of the soil into the matter, and again, maximum bite is achieved at some varying degree of wheel slip.

It's true, as you say, that to an extent, the whole thing can be analyzed as if the vehicle were static and being loaded laterally as if cornering, and many of the same things that would improve traction under those conditions do help the bike (or car) when underway, actual cornering, braking, and accelerating are in no sense static situations.

Can you elaborate on your "12% slip = max traction" statement? What do you mean by slip? Just curious, thanks!

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On asphalt surfaces, maximum straight line braking force is achieved when the tire is turning at a speed variably between 10 & 15% slower than actual vehicle speed. Likewise, maximum straight line acceleration comes when the wheel is spinning about that much faster than vehicle speed. Slip speeds in excess of that amount see the tire friction drop away very quickly.

While the dynamics of lateral acceleration are somewhat different at the tire than these two examples, the same thing applies, although there are a lot of factors which can change the optimum amount of slip. Some is better than none, but things deteriorate quickly once you reach the threshold of an excess.

That's for pavement only. Dirt is a whole different ball game.

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