Another tire question!

Got a question on tires in general. I find myself riding a lot of hard gravel roads getting to trails. Usually at 30-55 mph. Sometimes for 1/2 hour straight at a time. I run 18PSI front and rear with MSR HP Ultra Heavy Duty tubes. If I stop after 10 or more minutes after riding the gravel, my rear tire is HOT! Not scorching, but noticeably very warm! It's not weather related as this happens when its 50F outside too. Is this normal? Is it tire flex that is causing the heat?

On one of my 400R's, I have IRC Vulcanduros. They are wearing evenly but quickly. The other 400R has Maxxis IT's and are wearing evenly, and not as quickly as the IRC's. Both heat up pretty good. Is this heat causing them to wear out quicker than normal? Another observation: After the IRC's got to about 75% of tread remaining, they really took a crap fast and seem to be wearing twice as fast as when they were new running the same conditions.

What tire would be good for extended use on hard gravel roads but still work OK when I hit the trail? (Trails can be hard pack 40% to clay30% to soft mud 30%) By miles, I would say my use is 50/50 gravel road to trail.
 
It's normal for tires to heat up. Try the same on your car or truck and you will find that they also get warm. Less air pressure means more flexing and that makes more heat. Adding load is the same as removing air, you get more flex. That is why tires are rated at max psi. If you look at your dirt bike tire you will see it is at 36psi or so. One thing you could try is to air up before leaving home and air down when you hit the trail.

Heat does cause the rubber to wear faster. It's not a linear thing though. There is a heat point where the tires will just shred in no time. A little heat is not to bad, but a lot can fry your tires.

If I'm going to be doing extended high speed stretches I always try to air up to about 20. Even on my MT43 rear. My high speed is faster than yours though. I'm on the pavement or desert dirt roads and I'm going more like 50 to 65+.
 
Just a simple observation side note but the Bridgestone ultra HD tube is twice as thick and heavy.
Now some body is gonna come and say that is not necessarily good because of unsprung weight.
BS! Add a hefty heaping of slime and no flats will be had.
 
you could maybe try the dunlop d606 dual sport tire. its Dot approved for faster speeds and i have heard that it is decent on the trail i have never used it personally though. heres where you can get it.
Motorcycle Tire
just type in d606 in the search.
 
If I stop after 10 or more minutes after riding the gravel, my rear tire is HOT! Not scorching, but noticeably very warm! It's not weather related as this happens when its 50F outside too. Is this normal? Is it tire flex that is causing the heat?
I can only address part of your question whcih is rtelated to tire heat...all tires will get warm/hot when ridden on for any period of time at some type of speed. My wifes car has low profile tires on it and when it's cold outside the tire pressure sensor lights up (low tire pressure) BUT, once she's on the road and the tire's had a chance to warm up the light goers out due to the heat build up causing the tire to inflate. If you ever watch drag racers especially AA Top Fuelers you'll notice their back tires are very soft due to low PSI, when they take off the tire will suck in on the sides and grow in diameterwhat appears to be about 1 foot. To answer your question I figure it has to be due to friction bewteen the tire and gravel...more harder the surface the more friction.
 
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