Best Economy on Gravel

[SentraSE-R]

Park it 2-1/2 miles from the pavement, and get your morning and afternoon exercise walking from home to car and v.v.?

[DucFanDan]

^^ Actually... I am thinking (lightly) about buying the empty acreage right next to the paved highway and building a garage that could house pavement-only motor vehicles
(sports/collectible cars, sportbikes, etc). I wonder how long it'd take me to bike there... or get a really fuel-efficient dirt scoot to get there and back... something like a Ruckus, or a little 125cc 4-stroke dirt bike. If I could get it from my parents, they have an unused Honda CL175. It's 70's vintage. Gets upwards of 75 mpg. In great nick, just needs the carbs rebuilt.

Anyway...

They just regraded the road surface yesterday, then it rained, so it's slick and sloppy. Once it dries back out, I am going to be doing some speed tests in an effort to find the most efficient way to get up and down the road. It'll take time... I'm just gonna do it each day on my commute, so 4 times a week (I telecommute on Fridays). Will try 25 mph, 30, 35, 40, and 45. Anything north of that and you're starting to get into more measurable aero resistance.

The upshots of faster speeds are that you can maintain a higher gear, and you start to "skim" over the bumps. Actually, when it gets washboarded, the most comfortable speed is 50+.

[DucFanDan]

Quick update: I've tested 25, 30, and 35. It seems to like 35. Haven't tried 40 yet.

Down at 25, it downshifts and revs too much on the grades... just gets bogged down and slurps down fuel at the rate of about 8mpg.

At 30, it downshifts only on the steeper grades, and drops down to 9.0-9.5 mpg according to the readout.

At 35, it will hold gear on all but one steep grade, and it only dips below 10mpg briefly on the steepest grades.

Still need to try 40.

Bear in mind, when I give a speed, that's just my "target speed"... I let it rise up to 5 mph above when coasting downhill, and let it drop 3-5 mph when climbing.

So... thus far it appears to be most efficient on gravel in the same speed range it is most efficient on pavement. There may be a small difference... maybe peak is at 35-40 on gravel where it is 40-45 on pavement. Not sure yet, but they're shaping up to be close.

[trooper Tdiesel]

what kind of rock? theres all sorts of rock roads and they change from season to season..depending on repar of the road, level of traffic, and type of traffic..

is it packed 3/4 minus with fresh layer put on once a year. a common low traffic county road set up..
other then when the fresh rock is spred the amount of added drag on packed 3/4" rock is about as good as it gets for min rolling drag..


or is it the other extreme, raw pit run driving on 4 to 7" rocks.
in that case going around will be faster...then 5/15 mph. and carrying two spares..

don't get siped tires, or pay to have the tire shop put siping on them.
just a little bit of spinning on rock can shred a tire in no time flat...

running rock roads with tires rated at 40psi with 50psi on the car is a bad idea.
there not going to last long.
if they make them, you may want to change the car over to load range C, LT rated tires versus the P rated car ones..
it adds 2 plys to the face of the tire and helps let the tire live a longer life on rock or off road in genral.
LT tires are not common on newer sube's so there may flat out not be a size that fits the auto that's LT rated.

as the truck has much stronger tires load range D or E with a max rating of 65 or 80 psi id run it no less then 45 psi unless your loaded, then up them.

[Saskwatchian]

On the subject of tire pressure on gravel, I would actually DECREASE your pressure for better performance and puncture protection on gravel. Lower tire pressure will help take some strain off the suspension and make the tire less prone to puncture by allowing them to flex more.

I have found LT C tires to be perfectly adequate on gravel roads in rural SK but 10 ply LT E tires are more suitable to crushed rock roads of the north where I was getting a flat a week on my 6 plys.


If you aren't getting flats though I wouldn't worry about your tire choice, especially if you are carrying a full sized spare, a good patch kit and compressor (which IMO should be compulsory equipment for anyone traveling off the black top or in rural areas).