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Crazyrabbit 02-07-2011 09:57 PM

Altering Tire Rolling Resistance
 
It occurred to me today that I might lower the rolling resistance of my tires by cutting the tread blocks across the tread so that they were, by say, 1/2 or 1/3 as long, along the direction of travel. By doing this, I submit that the work of bending the tread as the tire enters and leaves the contact with the pavement would be reduced. I would propose to cut them to the depth of the tread. I think this would accelerate the wear rate during acceleration and braking, but then I am no tire engineer. I know we have actual tire engineers on this site, what do you guys think?

Since I got my Ohatsu Negotiator 155/80R13 tires that are rated for 51 psi, I have been able to get 64.6 mpg out of my '81 Diesel Rabbit. Since then I put on a four into one header, with a 2 1/4" system with a Flowmaster 50 series muffler. That was the most spectacular power increase I have ever seen, the top speed went up at least 10 mph! WOW! Inlet work and a new tall geared tranny are next. I should be able to lower engine speed at cruise by ~30%. Anybody got a spare long legged 020 VW tranny?

The Rooster 02-07-2011 10:09 PM

What you are describing is called siping, and is done to increse traction in mud, snow, wet, or otherwise low traction conditions. It's a process that was actually patented in 1923 by John F Sipe. The effect on fuel economy and tire wear have usually shown to be neutral, however handling on dry conditions can be compromised, making your tires feel squirmy or soft, which is why slicks are used in dry racing environments, and a lot of sport tires have very large tread blocks.

Frank Lee 02-07-2011 10:13 PM

I think it would have opposite the intended effect as it would promote even more flexing than without, and it is the flexing of the rubber than causes the r.r. losses.

I've sometimes wondered if filling inbetween the tread blocks with silicone rubber or ? would reduce r.r....?

CapriRacer 02-08-2011 09:50 AM

Quote:

Originally Posted by Crazyrabbit (Post 219157)
It occurred to me today that I might lower the rolling resistance of my tires by cutting the tread blocks across the tread so that they were, by say, 1/2 or 1/3 as long, along the direction of travel. By doing this, I submit that the work of bending the tread as the tire enters and leaves the contact with the pavement would be reduced. I would propose to cut them to the depth of the tread. I think this would accelerate the wear rate during acceleration and braking, but then I am no tire engineer. I know we have actual tire engineers on this site, what do you guys think?......

The stiffness of the tread is very minor compared to the stiffness of the belt, so anything done to the tread stiffness would have a minor effect. If anything, you'd want to increase the stiffness of the tread in the longitudinal direction.

But you've proposed removing tread rubber and that would have a positive affect. Better would be to remove tread rubber along the grooves - perhaps cutting off the corners.

Quote:

Originally Posted by Frank Lee (Post 219159)
........I've sometimes wondered if filling inbetween the tread blocks with silicone rubber or ? would reduce r.r....?

That would be adding mass - which would not be good. If you are thinking that you would be reducing the movement of the tread elements as they move through the footprint - that is a very minor affect as well and it's the belt that pretty much controls that.

Crazyrabbit 02-08-2011 10:42 AM

Thanks for the comments. Just to clarify, I was not proposing to remove any tread. I was thinking of just slitting across the tread blocks to the depth of the tread, so that at the beginning and end of contact the slit would open reducing the amount of flexing in the tread block. I would not expect this to have much impact on handling, but would expect the tread to deflect more due to braking and acceleration and therefore wear more.

The Rooster 02-08-2011 12:36 PM

Quote:

Originally Posted by Crazyrabbit (Post 219210)
Thanks for the comments. Just to clarify, I was not proposing to remove any tread. I was thinking of just slitting across the tread blocks to the depth of the tread, so that at the beginning and end of contact the slit would open reducing the amount of flexing in the tread block. I would not expect this to have much impact on handling, but would expect the tread to deflect more due to braking and acceleration and therefore wear more.

As I explained earlier, it very much does have an impact on handling. You are describing a process called "siping" that is practiced often in cold climate area's, when I lived in Washington, Les Schwab would sipe your tires for free when you purchased them if you wanted them to. The process has provent to improve handling, acceleration and braking on ice, snow, mud and wet conditions, however the tires become very spongy, almost slimy feeling when driving on dry surfaces.

CapriRacer 02-08-2011 01:11 PM

Quote:

Originally Posted by Crazyrabbit (Post 219210)
Thanks for the comments. Just to clarify, I was not proposing to remove any tread. I was thinking of just slitting across the tread blocks to the depth of the tread, so that at the beginning and end of contact the slit would open reducing the amount of flexing in the tread block. I would not expect this to have much impact on handling, but would expect the tread to deflect more due to braking and acceleration and therefore wear more.

Ok, so no change in the amount of tread rubber - so that makes it "Going in the wrong direction".


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