Tire Compounds

[wrayb]

My friend and I were having a discussion about tire compounds. I was surprised that we have 2 opposing views. Can someone give me the definitive answer? The question is: On a hard blue groove track you should use

A) a hard compound tire (to break into the ground)

? a soft compound tire (to grip better)

And...On a soft loamy track you should use

C) a hard compound (to dig into the soil)

D) a soft compound (to match the soft soil)

Can someone also tell me where to find the answer on the web?

Thanks, Barry.

[Guest Guest]

I've been told that the hard / soft terrain designation for tires has nothing to do with rubber compound--only tread patterns for maximum traction in each soil type.

[wrayb]

Chris, that makes sense...I just seem to remember reading somewhere that the hardness/softness of the tire compound also had an impact on tire performance. I have been racing go-karts for the last few years and tire compound is VERY important there. I was wondering how it impacted dirt bike tires as well.

Barry.

[Bruce_in_Phoenix]

A soft terrain tire ususally has taller knobs that are somewhat firm.

A hard terrain tire has shorter knobs and more of them for a greater contact patch with the dirt. A good one will have a softer rubber that grips hard surfaces better than a hard compound that tends to slide around on harder surfaces. My experience has been that Bridgestone M22's (a legendary hard terrain tire) wear out rather quickly but man o man do they work on the hard fireroads and rocks.

[Scott_F]

Tell it Bruce. That's why some sand tires are known to chunk (and chuck) knobs on sharp rocks, because the stiffer compound tears rather than flexes.

[wrayb]

Ok, so I win our discussion. Does anyone have a reference (web site?) that I can go do for the proof? I have to have something in print before I can take it back to my friend because he is convinced that hard surfaces require a hard compound and soft surfaces require a soft compound. I tried the tire manufacutures sites and I could not find anything.

After some thought...Here is my perception of tires for dirtbikes...when we talk about a "hard" vs. "soft" compound for tires we are talking about a "relative" hardness or softness...the "hard" tire is simply harder than the soft tire...the tread pattern is very important because, in the extreme, if the dirt is "as hard as pavement" then a street tire would perform better! The knobs should be almost touching each other (so there would actually be no knobs) and the rubber should be hard enought so it doesn't wear too fast and heat up...but the knobs would need to be soft enought to bend some and give good grip. On the other extreme if the ground is soft (like the DEEP sand we have here on the coast) a paddle tire works best, so the knobs should be far apart and sticking up as much as possible, and the rubber would have to be very hard so the long knobs would not bend too much...

Makes sense?

Thanks, Barry

[This message has been edited by wrayb (edited 02-23-2001).]

[This message has been edited by wrayb (edited 02-23-2001).]