Can I get taller gear to improve gas mileage-bigger tires or

[pinetreeporsche]

My old 2100cc '86 now has a 2200 rebuild w/ a good hp increase- so I go into the high-70s without a push. It used to get a bit less than 20 mpg on the road (not incl. city), probably at around 70 mph, but now seems down by 2 or 3- maybe because I'm going a few mph faster, but I wonder. Thinking about this I noted that the roadside speed warning light-up signs signal me that I'm going about 10% slower than my speedometer reads. That tells me I have tires that are a bit smaller diameter (and circumference) -although w/ a slightly wider tread than the OEM ones. (Michelin 'Agilis 61" 185 R 14C)
Q: I(s there a good modern tire that has a taller profile, thus larger circumference that fits the VW alloy wheels? OR- some other method of getting taller gearing-- probably not by changing to a Porsche 5-speed transmission, which would cost a fortune. Like: does the Vanagon have an optional output gearing that would help? With today's prices, 17 mpg is a pain in the wallet!

[dobryan]

Sloooow down. Speed kills mpg's.... Aerodynamic drag (and the Vanagon has a lot of drag) goes up by the square of speed. 60 mph is less drag then 70 mph by a factor of 3600/4900 = 73% less drag.

Try only going your 'old engine' speed and see what your mpg's are. I have a Subaru 2.5 with larger tires/gears and there is a big difference in my highway gas mileage with speed. (I did not go with larger tire/gears for better mpgs).
_________________
Dave O
'87 Westy w/ 2010 Subaru EJ25 (Vanaru) and Peloquin TBD

"To travel hopefully is a better thing than to arrive." Robert Louis Stevenson

MD>Canada>AK>WA>OR>CA>AZ>UT>WY>SD
https://www.thesamba.com/vw/forum/viewtopic.php?t=620646

Building a bus for travel in Europe (euroBus)
https://www.thesamba.com/vw/forum/viewtopic.php?t=695371

The Western Syncro build
https://www.thesamba.com/vw/forum/viewtopic.php?t=746794

[Phishman068]

I couldn't complain about 17mpg at "high 70s"mphs!
I don't get that when I keep my driving calm, mostly due to the size of my tires.

To answer your question, "NO". Big tires add big weight and resistance and are more likely to ruin your mileage than anything. I am told it can help a bit, to some extent, on an automatic vanagon, but not much on a manual/syncro.

As stated, slowing down makes a HUGE difference.
Your pushing a brick, and getting better mileage than a jeep. Be happy!
_________________
http://www.thesamba.com/vw/forum/viewtopic.php?t=559766&highlight=winter+rust
http://www.thesamba.com/vw/forum/viewtopic.php?t=482402&highlight=sunroof+syncro
http://www.thesamba.com/vw/forum/viewtopic.php?t=569774
http://www.thesamba.com/vw/forum/viewtopic.php?p=6864936#6864936

"Along with the ability to go fast, one looses the desire to hurry."

[MarkWard]

[Jake de Villiers]

I have a taller top gear, a 4.57 R&P and a more modern engine and still the only way to get decent mileage is to slow down. There's a big difference between 65 and 70 MPH and it gets worse from there...

Aerodynamics is king!
_________________
'84 Vanagon GL 1.9 WBX
'86 Westy Weekender Poptop/2.5 Subaru/5 Speed Posi/Audi Front Brakes/16 x 7.5 Mercedes Wheels - answers to 'Dixie'
@jakedevilliersmusic1
http://sites.google.com/site/subyjake/mydixiedarlin%27
www.crescentbeachguitar.com
www.thebassspa.com

[T3 Pilot]

GPS mounted on dash is helpful to indicate your true velocity. Consider running your van according to engine speed instead. The numbers posted above demonstrating the effect of velocity on wind resistance are sobering....
_________________
1988 Vanagon

The most important part in every vehicle is the nut behind the wheel......

[danfromsyr]

it takes alot or driving to make a good return on investment for transmission and tire upgrades.
where you (as mentioned above) can make an immediate difference with your right foot.
for a daily driver a few MPG makes a world of difference, but for a summer roadtrip travel excursion vehicle it's not a deal breaker.

but I ran some numbers once.
for a 2500mi trip

[Jon_slider]

> so I go into the high-70s

high 70s?
stop using your speedometer, they are not accurate, even with stock tires, which is the size you have.

your gas mileage calculations are probably also not accurate.
you need GPS speed, and GPS distance to get accurate mpg

comparing your mpg now and before the motor and tire change (you don't say what tire you had before), is most likely the difference between pressing on the gas pedal and smiling now, vs pressing on the gas pedal and praying before

but don't kid yourself, the horsepower increase is not a free lunch, it uses more gas, because you smile more (while stepping on the gas)

You can get MUCH better fuel mileage at 55mph than at 65. And much better at 65 than at 75. The fact your van can now go faster, makes total sense that it would use more gas. No free lunch.

And absolutely NO! you can NOT increase your gas mileage by using taller gears, nor by using taller tires. Those changes use MORE power, and wil DROP your gas mileage.

Congrats on your new motor, enjoy it. Gas mileage is NOT something you can tweak with gears and tires. Gas mileage is best tweaked by controlling the NUT at the Gas Pedal.
_________________
My Soapboxes: Inflation; Handling; Gearing; Decoupling; Swepco

[MarkWard]

To add to Dan's assessment. If I drive 70 mph for an 8 hour day vs 60 mph, my mpg does suffer, but I get about 80 extra miles for my seat time. Over a week, that works out to about 560 free miles for my seat time. For us, that is almost a day less driving.

So, as long as I have a job and am limited to x amount of vacation days, I'll pay for the extra fuel I use. In our van, if I drive 60mph, I get 36mpg or better. If I run in excess of 70 mph with the AC on, it drops to closer to 26mpg. So I am paying a monetary price to move along.

[Randy in Maine]

The next time you shop for tires, consider getting 195R14 tires.

They are a little taller (about an inch) than the 185R14 you have on there now. My 195R14 Hankooks are rated at "8 ply".

[Howesight]

To the OP:

There are a lot of good reasons to abandon the VW 14" wheel/tire combo, even though those alloys look nice. The best reasons are cornering stability, crosswind stability and tire availability.

If you live in a mountainous area (I do), then going to a larger-than-stock height tire gives you an advantage you might not have considered. I installed my BFG AT 215/16/75 tires (about 28.5" height) before I swapped out my tired 2.1 WBX. Although it had less acceleration in every gear after the change (I was just about to install an SVX engine, so I did not care), the one benefit was that I could run up mountain passes at, say, 50 to 52 mph in 3rd gear, rather than being rpm-limited to about 43-45 mph. Since my WBX engine was old and tired, I tried to keep it under 4,300 rpm.

Other than that one odd benefit, VW seems to have done a good job of gear ratios for the vanagon with the 2.1 engine. Most 2.2 and many 2.5 subie swappers keep stock gearing, it seems.

For what it is worth, my SVX conversion uses those same BFG tires, but higher 3rd and 4th ratios (0.70 for 4th) for noise suppression and gas mileage. The wind resistance on these vehicles is phenomenal. I can get 20mpg (US gallons!) at 55 to 60 mph, despite the larger engine. At 80 mph, fully loaded and with AC on (which my wife does a lot on long trips), gas mileage goes right down to 13 mpg. By the way, in my combo, 80 mph is right around 3,350 rpm, IIRC.

Even a tailwind or headwind makes a big difference. With the summer westerly winds here on our major east-west highway, I can still get about 19 mpg at 70 mph if the usual 15-20 mph tailwind is present.
_________________
'86 Syncro Westy SVX

[hdenter]

I improved my MPGs by going to a 5speed trans. I am running the trans from a euro 1.6td van. It has a bit of a tall ring/pin at 4.86 and 1st gear runs out a little faster than the standard 4speed gas model. The good news is that I can now climb the grade I commute over at 55mph/3500rpm in fourth and on the flats it spins 500rpm slower at 65 mph in 5th. I gained just short of 2MPG with the switch. Wasn't the cheapest route to go... Ultimately I plan to match this trans with some taller wheel/tires. This will bring the gearing of 1-4 closer to that of the stock 4speed and 5th will drop my cruising RPMs down even more. I may loose my easy climb in 4th doing this. My goal is 22mpg cruising at 65-70 with the weekender modestly loaded.

Hans
_________________
'79 triple white convertible bug
'84 sunroof vanagon
'85 weekender

[levi]

Maybe you guys are only talking about freeway driving, for which I do not have any long term results for comparison.

BUT, in town I had a significant increase in mpg by installing 28" tires.

I believe that's around 7 to 10% over stock.

I had long term gps data with stock tires, then 27", and then 28".
Fwiw, I had expected to lose mpg in town, but didn't care, expecting the dollar amount to be insignificant.
However, each gave an increase in mpg, in town.

I wish I still had the data, unfortunately it's been lost, but in each case it was at least 7, 000 miles of records to give a very solid average.

I now average a little over 25 mpg in town.

I should mention that I have a 2.2 suby with 4 speed transmission.

Also, I realize my driving style is very different from most folks, but since I used the same driving style in all cases it shouldn't matter.

I call around 10% increase substantial, but, I don't think anyone should do this just to save money. In my case the money saved in a year of driving is about $ 80.... = irrelevant.
_________________
One of these days I'm gonna settle down,
but till I do I won't be hangin round.
Going down that long lonesome highway,
gonna see life my way

https://youtu.be/cSrL0BXsO40

[Bassyaks]

I have a fresh 2.1 in a Westy I get 13 @65MPH and 21@ 55MPH.
slow down and anticipate the hills and you'll get better mileage.
enjoy the scenery, and don't worry about the other drivers, Hell, they know your the slowest thing on the highway

[bluebus86]

The vanagon speedo in my 1986 2wd van (non-camper) is overly optimistic. however the odometer is right on mark.

i did put larger tires on the stock steel rims i went to 195 tires, and that allowed me to drvie 70 mph and keep the engine revs down a bit, that was my reasoning, to preserve enigne rpm for better enigne life.

this makes cruising at interstate speds (70 mph) more comfortable (less engine speed,)

however i do notice a litle lack of umph when climbing step hills and do have to down shift sooner on the hills.

at a constant 70 mph on hihghway with some hills were i need to slow, van loaded with four people, and camping gear, I get about 20 mpg I also have a big bore 2.2 liter motor (96 mm pistons)

If i go slower at 65 mph I may get 1 more mpg better milage. around town short 4 mile drives, i get about 15 mpg

I like the bigger tires, but would not go any larger as steep hill performance does suck kind of.

keep that in mind, no free lunch, short of a fifth gear. bigger tires on a stockish motor will casue you to down shift to third. on the Priest Grade near Yosemite, I can still go up it, however going down I need to be in first for engine braking, used to be able to be in 2nd gear. so even going down hill big tires can cause you to go slower or use more brakes.

als check if your spare tire well will accept the bigger tire, i have heard (but not testesd) that my larger tires may not fit in the spare tire well without modification of the tires bracket (i still have an old 185 tire as a spare)

ideally VW shouldd have had a five or six spped tranny installed. oh well, and even at the high price of gas, a five speed tranny woudl not ever pay for itself in gas savings.

remember your moving a big fat box thru the air, the wind resistance goes up squared to the speed, double the speed, and you quadruple the wind resistance. you may well be able to get 20 mpg if you slow to 65/70 mph

also make sure your tires are inflated right low tires can effect mpg as can dragging brakes. car top carriers also reduce mpg

[pinetreeporsche]

THANKS FOR ALL THE COMMENTS. I'll be putting on 195 tires next re-tire-ment time, and assume that the extra power I have at 2200cc will help me to avoid downshifts except on steeper hills. Clearly the change of output ratios is not worth considering until I've tried the larger tire size. -Chris H. in northern VA

[Jon_slider]

> I'll be putting on 195 tires

that tire is only .3" taller (radius) than a 185, or 2.4% taller. I doubt you will notice any difference. imo, it is not a significant size change.

most important is to get a tire that is properly load rated. Do NOT buy a passenger tire. I recommend the Hankook RA08 in either 185 or 195 from
http://www.busdepot.com/catalogsearch/result/?q=hankook&dir=desc&order=default_sort_order

> the extra power I have at 2200cc will help me to avoid downshifts except on steeper hills.

extra power? what extra power? 100cc is only a 4.7% increase. A 2.1 motor has 95 horses, you just added 4.5 horsepower, basically nothing.

Disabuse yourself of expectations of any significant difference.

think of it this way, if your motor is now 4.7% stronger, and you add a tire that is 2.4% taller, you are left with just 2.2% "extra" horsepower, or basically, 2 more horses than a stock motor..

not significant. Im glad you abandoned the fantasy that bigger wheels would give you better fuel mileage.
_________________
My Soapboxes: Inflation; Handling; Gearing; Decoupling; Swepco

[pinetreeporsche]

...slow down and anticipate the hills and you'll get better mileage.
enjoy the scenery, and don't worry about the other drivers, Hell, they know your the slowest thing on the highway[/quote]


Slowest? In the mid '70s I took my 40-horse Splitty from Boston to Guatemala and back (ok, had to do a motor swap in PA on the way home). Did a lot of drafting of the big rigs. Ah, the folly of youth.