Fuel mileage with a rock guard

Franksteer · 05-29-2019, 12:48 PM

Just bought a 94 inch rock guard for my Winnebago Vista 36y. I am wondering if fuel mileage will decrease when installed because of wind drag.

Tucsontoy · 05-29-2019, 01:35 PM

No. Your rig has already cut a path through the wind. Air actually circles back from your rig so that air currents are net zero. That is why dirt can sit on the rear bumper.

Jim_HiTek · 05-29-2019, 02:33 PM

You won't have a measurable difference in fuel mileage.

But you will notice more rock hits on your toad with the rock guard. You'd be better off to return it before installing it.

Oldchinahand · 06-04-2019, 11:01 PM

When we bought our rig it was fitted with mud flaps behind front and back tires and a Rock Gard just under the radiator. It was trimmed to the recommended 4in ground clearance.

Deep sixed the Rock Gard a few years ago. Stopped using the big bulky rock gard on our dinghy tow bracket as well.

To Jim's point, seems clear to me that the Rock Gard just stirred up dust and gravel (we are more byway folks than highway folks) and pelted our dinghy rock gard and windshield. Chipping the latter.

40K+ miles w/o either rock gard, and our dinghy and windshield have not been dinged.

Believe the mud flaps deflect any gravel picked up by the tires.

Fair Winds and Following Seas

Cooperhawk · 06-05-2019, 06:43 AM

My rock guard is installed so that it clears the ground by at least six inches and I have absolutely NO rock dings on any toad. We have towed three different vehicles with no damage whatsoever.

Just like any other subject you address on any forum, you will get all the negative answers, but very few of the folks with a positive opinion will venture forth.

Jim_HiTek · 06-05-2019, 08:32 AM

I was the campground host at a large campground in Fairbanks, Alaska. I was considering a wide mud flap back then so as guests would pull into the campground I'd ask them if they had one or not, and how the trip went as far as rock hits.

Most of the wide mud flap users had rock chip damage and most of those without did not. Of course some of the difference had to do with the toad's profile, and the height off the ground of the mud flap and whether or not it was a solid flap or a brush type, but in general, without one seemed to be better for the toad.

That straw poll was good enough for me. That along with the test I ran before I ever bought a class a were enough to convince me having the mud guard did more damage to the toad then not having it. ON AVERAGE.

What I did was to follow big Class A rigs and watch how they were driven. I'd never driven a big vehicle before so I was curious how they handled, the typical speeds driven, how quickly they switched lanes...that sort of thing. And since this was in Portland, OR, I often had the opportunity to follow them in the rain.

And wow, what a surprise the first few times I'd be following and 'sploosh', a ton of water would hit the windshield. Wait a few seconds and sploosh, another ton of water. If it wasn't that periodic sploosh, it would be a heavy buck shot type rain storm effect of smaller droplets that if I backed off from the RV would go away. And finally, there were those where when following them there wouldn't be any 'extra' water hitting my windshield, just the rain. The difference I discovered was mud flap, broom, and no wide product at all, just the mud flaps behind the duals.

Hmmm. That's interesting, I thought, might require some more testing. So I sought out RVs traveling on gravel roads. By this time I'd already researched a little on RV dot net and iRV2 forums and found that many people were asking if they did any good. Same thing only this time, instead of rain, gravel sized rocks, or small pebbles would hit the windshield with the guards and nothing from those RVs with no guard. I had a crappy car I was planning on getting rid of anyway so I didn't care. Didn't run that test very long either. Just long enough to form an opinion. And my opinion is that wide rock guards did more harm than good. Wide brooms did a little better then the rock guards but still kicked up small pebbles. The best seemed to be just the mud flaps behind the duals. To be fair though, I didn't try to made note of 4" vs 6" off the ground flaps. They all seemed to toss up gravel. Just less with the 6" height.

So my opinion comes from both a straw poll & observation in real world situations.

Meridian42e · 06-08-2019, 10:53 AM

Ours came from the factory with a rockguard and threw rocks clear up into the air intake in front of the windshield of the Jeep. One day my daughter was following me in the rain and she said the the water spray patter off the back of our coach was stupendous! It completely covered the Jeep in a spray up over the top of the roof.

I took off the rock guard and never had a complaint since. I run naked back there, just using the factory mudflaps behind the tag.

sciguy6 · 06-10-2019, 08:16 AM

I put on a solid rubber one on my Thor Ace as my Jeep Wrangler engine compartment was caked, absolutely caked with dust and dirt. Dust if no rain, dirt if rainy. Did the trick and was significantly better. Also a bonus was my rear camera which was unusable during rains, was much better. I now have a diesel pusher and no flap and getting the same issue in my Jeep. I am going to try putting the same on on but the difference is that on the ACE, I installed it on the bumper but have to do the frame rails on my DP. So maybe that is the difference but maybe put it up a bit higher than the 4 inches recommended ad try to get it closer to the frame. On my to do list.

Oldchinahand · 06-10-2019, 11:27 AM

What are the odds!

Some of us like 'em, some of us don't.

I love America!

Fair Winds and Following Seas