Stock tire testing

[Bray D]

I did some tire testing and am super impressed with the added performance from grooving them. Here's what I found.

stock tread - forward rotation
http://www.facebook.com/profile.php?...v=538226704182

stock tread - reverse rotation
http://www.facebook.com/profile.php?...v=538226878832

then I cut em up


and here's the cut tread - forward rotation
http://www.facebook.com/profile.php?...v=538226963662

cut tread - reverse rotation
http://www.facebook.com/profile.php?...v=538227023542

I can't wait to get em on some rocks and see how they do.

[jakedasnake92]

Wow that looks like a good improvement. But what kind of surface are you doing that on is it just like a table made of wood with a flat surface or does it have some sort of texture to it?

[Bray D]

I'd say its a slightly padded smooth vinyl top on it.

[jakedasnake92]

I know your video shows the improvement on grooving the tires, but i dont understand how that would change it on a flat smooth surface like that.

[ozpall]

stock tires are crap, they had been tested by a lot of people here, cutting em, rotating em, use them as an obsticle curse and they are great.

[Bray D]

Originally Posted by jakedasnake92

I know your video shows the improvement on grooving the tires, but i dont understand how that would change it on a flat smooth surface like that.

I have no idea either. I guess that's why I was so surprised after seeing the results. I need to get out on some rocks to see if it made any "real world" improvement. Damn the snow.

[Grumpster1980]

Your living room scares me! Black plastic bags and a gas can!

Not a bad idea on cutting the tires

[Bray D]

lol that's the basement, mostly used for storage and the "creeper proving grounds." Plastic bags have holiday decor in them and the 'gas can' is a case that houses a laser (land survey equipment). Its safe

[Simon.O.]

I have done a lot of cuting and removing of lugs on the stock tires and will now leve them as a sort of mudder tire.

I cut out every second knob from the centre rows and then did the same on the outside rows. I have siped the sidewalls and chaneled the foam.

All of this was done progresivly to monitor changes in the tires performance. All of these changes made an improvement.

I then got a set of Rock Lizzards that are also considered as rubbish and did the same R&D on them. They are better than the Ridgelines. Not by a lot.

During this time I got many hours in on the rocks and learnt to drive well too. That can make a big difference.

Yes the stock tires are not flash but for us that have to order stuff in from overseas we begin to learn how to adapt with what we have and then make some very informed decisions.

Rovers or Chisels ?? for example !

Keep in mind that it will cost me about $20USD or more just to post me some tires.

["N8"]

friction is friction, smooth or rough the table is a fine test. I bet those tires are going to rock. Makes me want to remount my old tires on some rims and chop em up.

[Bray D]

friction is friction - exactly right. Thing is, the force of friction is equal to the coefficient of friction (factor of the two materials - rubber and table) times the normal force (force perpendicular to the table). The coeffecient isn't changing since I'm not altering the properties of either material, and the normal force isn't changing since I didn't add any weight to the crawler.

According to the is equation, it should perform the same on in this test whether the tires are siped or not. Where the siping would help is where there's a rough surface for the lugs to 'grab'. The added siping will allow the tread blocks to deform more, and better 'grab' the terrain.

All I know is the videos speak for themselves, and I can't explain it lol.


Thanks for the info Simon - good stuff

["N8"]

my guess is you have increased your surface contact patch. by siping the tires you have allowed almost 1/3 of the lugs to deform more freely then they were. adding this extra lug deformation would allow more elongation of the lugs giving you more surface area of the lugs contacting the ground.

then again... its just a guess.

[Bray D]

Force = suface area * pressure. Force is constant, so increasing surface area will just decrease pressure. Larger surface area*lower pressure (siped tire) = smaller surface area * higher pressure (stock tire). The resulting force is the same, which should yield the same friction force.

Friction is interesting. Its formula suggests that friction is completely independant of contact patch, tread design, etc.

["N8"]

Now admittedly I am not an expert on the matter, but I think your view is a little skewed. Force is beset on factors of a situation. Its a mesurement of how much power is being transmitted to an object that has mass. You can talk about force in terms of how much force the tire can withstand before it breaks traction, or you can talk about how much force you can transmit through the tire and into the ground. Saying force is constant is a little misleading.

On the subject of tires, you have a certain amount of power you are trying to transmit into forward motion through two fricative surfaces. The larger the contact patch the more power you will be able to transmit into forward kinetic energy. So in terms of the crawler there is a set amount of pressure determined by the weight of the vehicle and gravity. So when you only increase the surface area you also increase the force being applied to the tire and ground.

This is why on a drag racer you tend to see humongo tires. If force didnt change through varying amounts of surface area, then theoretically you could take a tire and chop of 90% and still make it to the finish line in the same amount of time.

[Bray D]

I think you misunderstood my post. There are two "forces" in the equation for friction - the "friction force" and the "normal force". The normal force is what's constant. It's dependent on the weight of the vehicle. The weight isn't changing so the normal force is constant, regardless of what tire the vehicle is on.

I hate it when people throw around their degree to try and establish themselves as superior. I'm by no means trying to do that, but I feel its necessary to say that I'm in my senior year of getting a Mechanical Engineering degree. Just trying to establish my credibility on the topic.

Here's a little write up that might help reinforce my statements:

http://www.engineeringtoolbox.com/fr...nts-d_778.html

I disagree that the larger the contact patch, the more power you will be able to transmit into forward motion (forward kenetic energy). Again, looking at the equation for friction, the friction force (the force used to propel the vehicle) is independant of the size of the contact patch (surface area) or tread pattern. The ONLY thing that determines the friction force is the coefficient of friction (function of the two fricative surfaces, which doesn't change), and the normal force (again, which doesn't change). This means that regardless of the tire size, the friction force is the same.

Remember, we're talking about smooth surfaces here. If the surface were rough (porous rock face), then yes, surface area and tread pattern matter. Not because they increase friction, but because they offer more forward pulling lugs. The forward pulling lugs provide a force that propels the vehicle, but that force is NOT a friction force.

Walking is forward motion due to friction between your shoes and the pavement. Pushing yourself off of a wall is forward motion due to a force transmitted through your shoe, and into the wall - NOT friction between your shoe and the wall. That was my analogy to try and explain why siping would help propulsion, but not because of the added friction haha.

I was hoping you would bring up drag racing. I was going to, but I thought I'd wait until you did. My explanation of wide slicks is the larger the contact patch, the more likely you are to find a spot on the race track with a higher coefficient of friction. Therefor, the increased friction force is not due to the fact that there's a larger tire, but because the tire found a higher coefficient of friction between the tire and the track.

I know I'm arguing what my videos show, which seems like nonsense haha. BUT according to physics, what I state should hold true. Maybe after the multiple runs during my tests, the tires got 'cleaner' which increased the coefficient of friction between the tires and the table resulting in a greater friction force that allowed me to climb a steeper angle - who knows.

["N8"]

Im gonna get back to you on this one. I think that your thinking has a hole in it, but im not gonna figure it out till I can get my hands on some other books.

...ill be back

[Bray D]

I look forward to hearing what you come up with

[Bray D]

Find anything?

["N8"]

sorry the minds and books I was hoping to probe wont be together till 7 pm tonight. Ill get back to you in a lil bit

[Bray D]

Sweetness. I love tech discussions haha