Ideas for improving poor gas mileage

[flying kurbmaster]

all due respect but 10% gain on large vehicles is massive without changing drive trains, I have a small Toyota van that I grill blocked, partial belly panned, installed spats, filled the spokes of the mags, installed a kamback and LRR tires my gains were about 10%, before the LRR tires and I have not seen much of a gain since I get 33mpg imp. this is a small van with an aero shape, On my stepvan the Kurbmaster, which is a brick, I grilled bloked, full fender skirts, side skirts, kamback, belly pan, skirted between the front and rear wheels, wings down the sides at the back, an air dam on the front, monitor air pressure and have seen little to no gain in mpg. It seems very difficult to make gains on the stepvan due to its built in poor shape, the front air dam seems to have produced the best gains at round 3%, the rest of the stuff is interesting but at this point not working, I plan on making some of it bigger like the Kamback and the wings on the back. Now if I installed a cummins 4bt I might find 20% gains. I get between 15 and 16 mpg imp.

 

[SoulRaven]

Greetings!

I agree, a 10% gain to me is huge, but others have told me that going from 13.5mpg to 15mpg just isn't worth screwing with.

To me that translates into an extra 50 miles per tank. After you do the math, that's saving me between $15-$20 per tank, for a one time $29.95 investment.

Normally, my return trip from Florida costs about $15-$20 less than getting there, that particular return trip cost me over $100 MORE!

Maybe the guys who don't understand don't do enough driving to care...

Cheers!

The CamperVan_Man

 

[Van-Tramp]

I fear that people are being sucked in by the siping fad. It is great if you live in COLD climates, but will DESTROY your tires in hotter weather.

Understand what siping does; it allows the rubber tread blocks to move more, to flex more. That movement causes friction which in turn causes grip. That friction should, if anything, worsen your MPG's, not make it better. It will also give the sensation that your vehicle is is driving on gelatin, not hard rubber (moving around a lot more, especially on grooved roads).

Anyone with a grade-school education in physics will tell you that friction also causes heat! Heat will wear your tires faster and possibly to a dangerous level in a very short period of time. Siping is NOT something I would recommend and I fear that people will be learning some very hard lessons soon. Best of luck.

 

[user 423]

You'll notice Schwab or others selling the service make no claims of better MPG, only better traction. The tire companies use some pretty fancy technology these days when designing their tire treads, so slicing them up would be messing with a good product. There are low rolling resistance tires available which offer more MPG and would be a better solution. You would have to do some long-term testing to substantiate better MPG and test for extra tire wear. A 10% increase is very hard to believe.

 

[WheelEstate USA]

Given the cost of good tires I'm not about to mess with their design.

 

[SoulRaven]

I fear that people are being sucked in by the siping fad. It is great if you live in COLD climates, but will DESTROY your tires in hotter weather.

Understand what siping does; it allows the rubber tread blocks to move more, to flex more. That movement causes friction which in turn causes grip. That friction should, if anything, worsen your MPG's, not make it better. It will also give the sensation that your vehicle is is driving on gelatin, not hard rubber (moving around a lot more, especially on grooved roads).

Anyone with a grade-school education in physics will tell you that friction also causes heat! Heat will wear your tires faster and possibly to a dangerous level in a very short period of time. Siping is NOT something I would recommend and I fear that people will be learning some very hard lessons soon. Best of luck.

Greetings!

Friction and traction are two different entities. If you are spinning your wheels, you have a lot of friction, but no traction. If you are stuck in mud, you have lots of friction to throw mud all over, but you have no traction to get out of it.

Likewise, infusing extra air into the rubber hitting the road will have a cooling effect not a heating one.

Siping reduces the rolling resistance of the tire = less friction.

I've got a total of probably 75k miles on siped tires in both hot and cold climates, and I have never experienced any kind of a mushy feel. My first set of siped tires were rated at 40k, and I got a little over 50k on them before the wear bars told me it was time to replace them.

Finally, if they are so bad, why have so many 18 wheelers been using them since the early 2000's. Simple, better traction, longer tire life, and better mpg.

A few years back Volvo promoted an increase of 2 mpg on their new trucks. It was a HUGE success for them... They didn't change their trucks, they siped their tires!

Some will tell you that water must flow downhill... Yet water can and does flow uphill in many cases. Physics is not an exact science, over half of it are only theories, not necessarily reality.

Meanwhile, I'll keep enjoying the benefits of my siped tires...

Cheers!

The CamperVan_Man

---

You'll notice Schwab or others selling the service make no claims of better MPG, only better traction. The tire companies use some pretty fancy technology these days when designing their tire treads, so slicing them up would be messing with a good product. There are low rolling resistance tires available which offer more MPG and would be a better solution. You would have to do some long-term testing to substantiate better MPG and test for extra tire wear. A 10% increase is very hard to believe.

Greetings!

I had a chance to examine some of those tires, and they looked very close to my siped tires. The only noticeable difference I could see is that mine have kind of lopsided elongated diamond shapes, and those had smaller more conventional diamond shapes.

Those were passenger car tires though, so the slight difference in design might have something to do with weight ratings or something.

Well, maybe I gave a wrong figure at 10%... Help me figure it out, according to my trip computer I went from 13.45 mpg to 15.1 mpg (exact figures) and also according to the computer, I went from 470.75 miles per tank to 528.5 miles per tank with a 35 gallon tank.

So am I wrong? I admit that I didn't use a calculator or anything in coming up with saying 10%, I just eyeballed it...

Cheers!

The CamperVan_Man

 

[Van-Tramp]

Traction is derived from friction CamperVan_Man. That is plain physics, no arguments about it.

The opening up of the tread is NOT allowing air in there to cool them, the siping is specifically to allow the thread to move MORE (which does grip the road surface better). Take any piece of metal (say a spoon) and bend it back and forth hundreds of times. What happens? It heats up and eventually breaks. Again, plain physics and no arguments about it.

If 18 wheelers are using siping (I've yet to see a single siped tire on a truck) I can guarantee you it is being done at the tire manufacturing level, not after the fact. And I can also assure you it is being done for SAFETY (grip on snow and ice) not MPG.

Volvo's marketing does not equal fact.

"Physics is not an exact science..."
Um, yes that is EXACTLY what it is; taken from hundreds of years of very smart people doing a lot of science.

If you are perceiving a benefit, by all means go for it. Again, I would never recommend siping perfectly good tires. If I wanted cold-weather tires I'd buy cold-weather tires. If I want tires designed specifically for better MPG, then I'd by LRR tires. Siping is certainly no magic solution and in my mind it is a danger to the uninformed.

 

[SoulRaven]

Greetings!

Oh, I forgot to mention that those figures were both taken at 60mph on the same stretch of flat level ground.

Cheers!

The CamperVan_Man

 

[user 423]

Trip computers can be wrong and I wouldn't rely on them for accurate MPG figures at all. Accuracy only comes from the old miles/gallons calculation and that's with an odometer that has been verified by mile markers over long distances.

 

[GotSmart]

I started looking around to find out what is true.

http://www.cleanmpg.com/forums/showthread.php?t=26119

For those who don't know, there are 2 types of tire siping:

1) The kind the tire maufacturer puts in the molds. These will always have a small gap in them. In some respects, these are just very tiny grooves.

2) The kind put in after the tire is made - and that's probably what we are discussing here. these typically have no gaps and are produced by a series of circular kife cuts:

Needless to say, there is a charge for this service.

There are a lot of claims about this process - some true, most NOT!! So what is the truth?

1) This will violate the tire manufacturer's warranty. It is altering the tire and that is expressly forbidden by every tire manufacturer's warranty.

2) Wet traction improvment: Yes (No effect of hydroplaning resistance)

3) Snow traction improvment: Yes

4) No affect on wear? No, this adds more movement to the tread elements - which is why you get wet and snow traction!!

5) No effect on fuel economy? No. Movement = heat = increased fuel usage.

6) Dry traction: worse.

7) Ride: No effect

8) Handling: very slight degradation in crispness. Where you would see a major change is in grip (traction)


And this from Tire Review, an industry publication that has studied the process.

http://www.tirereview.com/Article/82425/explore_tire_siping_for_added_opportunities.aspx

While opponents admit siping enhances traction on snow and ice, they note the process makes the tread squirm more, decreasing performance on dry pavement and increasing wear. By making the tread more flexible, siping increases rolling resistance, thus reducing gas mileage. It also results in more road noise.

 

[flying kurbmaster]

Greetings!

Oh, I forgot to mention that those figures were both taken at 60mph on the same stretch of flat level ground.

Cheers!

The CamperVan_Man

I am not doubting your figures, I was wondering if they were taken at the same time of year as winter, summer can differ by that much you will get much better mileage in warmer temperatures. Better to make your big miles midday then evening or morning.

 

[GotSmart]

I found no reference to Volvo in my research.

---

I am not doubting your figures, I was wondering if they were taken at the same time of year as winter, summer can differ by that much you will get much better mileage in warmer temperatures. Better to make your big miles midday then evening or morning.

The different fuel mixtures sold summer and winter will also make a difference in mileage.

 

[SoulRaven]

I am not doubting your figures, I was wondering if they were taken at the same time of year as winter, summer can differ by that much you will get much better mileage in warmer temperatures. Better to make your big miles midday then evening or morning.

Greetings!

Those figures were taken on the same day, roughly 2 hours apart, immediately before and immediately after having the tires siped.

In the real world, I typically fill the tank just before it reaches the 1/4 mark. The actual mileage traveled on that amount of gas, immediately saw an increase of 30-35 miles, and has remained relatively constant for the last 1.5 years on this set of tires.

Cheers!

The CamperVan_Man

 

[GotSmart]

So the tire industry says your mileage will decrease, but you ignore that and say yours has increased. :huh:

Dude, I do not know what to say~~~:dodgy:

 

[SoulRaven]

Trip computers can be wrong and I wouldn't rely on them for accurate MPG figures at all. Accuracy only comes from the old miles/gallons calculation and that's with an odometer that has been verified by mile markers over long distances.

Greetings!

I certainly agree that these trip computers are toys... I am also a volunteer who does some search and rescue, and you'd be surprised by the number of people who get stranded on logging roads etc. because their computers led them that way...

While I can't verify the accuracy of my odometer, the same odometer was used in all testing, so the figures should be relatively accurate in comparison.

My main method of calculation is by writing down my mileage at every fill up, along with the amount of fuel added at that fill up, and the price per gallon paid, and the total price.

I then use that data to calculate per tank, per 1k miles, per season mileage, and per year mileage. I can tell you that when they put ethanol in the gas in the winter, it costs me 2 mpg.

So I believe that I keep pretty accurate records, and the long term records should compensate for the differences in how far the tank is topped off each time, as well expansion due to heat etc.

If you take your over all mileage for a year, and divide that by total gallons of fuel used, that should give you a pretty good reflection of your average mpg for that year.

Cheers!

The CamperVan_Man

 

[user 423]

OK, this extra MPG came with the new tires, right? That means unless the tires were the exact same brand/model the new set could be slightly larger in circumference than the old which would be the same as having a higher gear ratio and then give you more MPG. Actually, since they would have more tread than the old ones, that would be true anyway. If you changed brands it could mean that the tire compound or other design differences of the new tires result in less rolling resistance and therefore give better MPG. In addition, even a newer version of the same tire model might be better MPG wise! Unless you had the exact same tires as before, your figures don't mean anything.

 

[SoulRaven]

"Physics is not an exact science..."
Um, yes that is EXACTLY what it is; taken from hundreds of years of very smart people doing a lot of science.

Greetings!

After reading your post this morning, since I was heading to the university anyway, I stopped in to ask a physics professor about the definition of physics.

He opened up a book entitled Physics 101, and in the preface, here is what it said:

"Physics: A set of ever changing core theories thought to be accurate and correct at the time of their inception."

The professor then went on to say: "Nothing in this universe is an absolute, it is constantly changing, as is our knowledge of it. The art of physics is the constant struggle to either confirm or disprove these theories, which during this process new theories can emerge. There is no such thing as an absolute fact, only a person's conception of it in any given set of time and space."

I recorded that to make sure I got it accurate...

As I thanked him and walked away, and I can honestly say that I was feeling more confused than I was before that visit, and it conjured up memories of why I had dropped physics many years ago.

So I guess it's kind of like religion and the bible, each person derives their own personal interpretation of things. With the identical set of resources, one person might see peace and tranquility, while another sees violence and mayhem.

Peace!

The CamperVan_Man

 

[WheelEstate USA]

Its real simple...altering tire tread in such a way causes more heat. Tires wear quicker and it has no positive effects in every day driving. If you thing you're getting better MPGs its because your tires are paying the price with their lives.

I raced sand rails some years ago and we used to cut our mud paddle (fins) tires so they would unload mud faster when running bogs. Worked, but the tires didn't hold up as well in the long run.

IMO...cutting up a $500 set of van tires is just plain wacko.

 

[user 423]

You should ask the same physics professor how cutting narrow grooves into tires could possibly reduce rolling resistance. Also, I reread a little....you went from 16.5" tires to 16" tires in Florida and got less MPG. That's because the 16" tires lowered the overall gearing.

 

[SoulRaven]

OK, this extra MPG came with the new tires, right? That means unless the tires were the exact same brand/model the new set could be slightly larger in circumference than the old which would be the same as having a higher gear ratio and then give you more MPG. Actually, since they would have more tread than the old ones, that would be true anyway. If you changed brands it could mean that the tire compound or other design differences of the new tires result in less rolling resistance and therefore give better MPG. In addition, even a newer version of the same tire model might be better MPG wise! Unless you had the exact same tires as before, your figures don't mean anything.

Greetings!

The calculations made were on a single set of tires that were siped at approx. 5k miles. The before and after figures were then compared.

I had in fact realized gains on a previous set of tires, but like you mentioned, since they were new tires as well, I was not sure whether it was the new tires, the siping, or possibly a combination of the two.

So I just silently enjoyed the advantages. On my current set of tires, the only factor that changed was the siping, which resulted in a noticeable change in mpg.

I tend to go to great lengths in testing things, and also to consider any mitigating factors involved when drawing my conclusions.

I have absolutely nothing to gain by posting my experiences, other than the possibility of helping others. Life is a never ending learning experience for me. While I have traveled down many roads throughout the years, sharing my hard earned knowledge, both my successes, and my failures, hoping that perhaps I can improve the life of even one single person through the sharing of these experiences, that is what brings joy to my life.

Cheers!

The CamperVan_Man