Taller tires for pickup?(do they increase mileage?)

[aardvarcus]

Regardless of who is right/wrong/nice/mean/etcetera why don't we try to get back on topic. Having some experience changing tire sizes on both big trucks and small cars, I figure I will try to assist from my experiences.

My first question is how low is your first gear? 10% taller means 10% lower cruising RPMs, but it also means over 10% harder on takeoff. It is something to consider, especially if your clutch is already worn, and may make you replace your clutch sooner both because it will wear a little faster and you will notice it is worn more. I am ok with the tradeoff in my Celica, but my 0-10mph take offs have definitely slowed down.

Second your cruising RPM’s aren’t that bad already. On my Celica sixth gear is 0.725, final drive is 4.529, and stock tires are 24”, thus at 65 MPH rpms are 2925 and at 80 RPMs are 3600, which are way out of the best RPMs for economy. That was a big driver in my change, but I think you are already in good shape on that front. On my trucks changing tire diameters on my truck from approx. 31.5” to 33” (5%) wasn’t really noticeable, as the differences in the other aspects of the tire overwhelmed changing my cruising RPMs when I was already at 2000ish.

Third, since you are already at a decent RPM choosing the correct tire tread pattern will have more to do with your fuel savings than the diameter. From my experience with a few different tires I would recommend Michelin M/S 2 for mainly street use, but they handle “light duty” off-roading fine as well, aka taking your 4x4 where you need it to go without getting stuck, but not dedicated offroading.

Fourth, weight of the tires matters too. Tire weight affects mileage more than regular on the car weight. It isn’t as important when you get up to speed, but if you get heavier tires expect to mash the gas harder or wait on the gas longer to get up to speed. Even highway driving has some speed up and slow down to it, so it still factors in a bit. On a truck going from a light tire to a heavy tire of the exact same diameter is noticeable on acceleration. (255/85R16 (light) vs 285/70R17 (heavy), both approx. 33” tires)

Fifth, I would let the prices of the tires help with choosing the size. On my car I knew I wanted Michelin Energy Savers, stock as 205/50R16 l and I wanted to do 205/60R16, but ended up with 205/65R16. The reason being at the time the 60’s were $120ish each and the 65’s were $75ish each.

[euromodder]

I'll have some first hand experience with taller tyres pretty soon.

As I wanted to fit ***** ***** tyres - the sole double A (*) rated tyre available in a size that more or less fits the VW up! - I'm going to fit 185/60/15 tyres to The Dwarf instead of the 185/55/15 that VW wants to use.

[Well, it won't happen, as the AA-tyres I intended to get aren't even in production !
Lots of blahblah in the media since about 1 year, but only 1 of these tyres is available, in ONE size.]


(*) on the European tyre labeling system
- A (best) rating for low rolling resistance / fuel use
- A (best) rating for wet braking

Closer Look at the EU Tyre Label | Blackcircles.com

[aktacoma]

So today I did a 50 mph 60 and 70 rpm test
50 mph-1750 RPM
60 mph- 2090 RPM
70 mph- 2500 RPM

I am looking at getting Yokohama Geolander A/T-S
in 30x9.5 R15 which has an overall diameter of 29.6 inches

another question does siping the tire decrease tread life?

[mcrews]

Originally Posted by aktacoma

So today I did a 50 mph 60 and 70 rpm test
50 mph-1750 RPM
60 mph- 2090 RPM
70 mph- 2500 RPM

I am looking at getting Yokohama Geolander A/T-S
in 30x9.5 R15 which has an overall diameter of 29.6 inches

another question does siping the tire decrease tread life?

Can you live with 1750-1800rpm?
does it bog when you need to speed up?

Also do you have a scan gauge to check the mpgs at those speeds?

[Sporty Modder]

Siping does decrease tread life, but gives you better grip, esp on snow/ice. Probably decrease mpg due to the tread flex.

[star_deceiver]

Siping will get you a little more grip but those all seasons will become hard as a rock when the temperature dips and you'll become just another one of those 4x4's in the ditch on a nice, icy day. Once the miserable weather starts, ditch the good FE all seasons and put on the winters tires/wheels!

Take the 1-2mpg hit with the winter tires. It costs a lot less then fixing your truck because you slid into the back of someone!

As for taller tires, make sure they will fit without rubbing. You can only upsize so far before your first corner rubs a nice hole in your fender wall.

[aktacoma]

Originally Posted by star_deceiver

Siping will get you a little more grip but those all seasons will become hard as a rock when the temperature dips and you'll become just another one of those 4x4's in the ditch on a nice, icy day. Once the miserable weather starts, ditch the good FE all seasons and put on the winters tires/wheels!

Take the 1-2mpg hit with the winter tires. It costs a lot less then fixing your truck because you slid into the back of someone!

As for taller tires, make sure they will fit without rubbing. You can only upsize so far before your first corner rubs a nice hole in your fender wall.

I've been driving in snow and ice all my life all I have ever ran is all terrains drive slowly and dont be a jackXXX and you get by just fine. I mostly run around in 2 wheel drive in the winter.

[Frank Lee]

If it was me I'd shoot for 1000-1200 ft/mn piston speed at 55 mph.

[aktacoma]

Originally Posted by Frank Lee

If it was me I'd shoot for 1000-1200 ft/mn piston speed at 55 mph.

please explain

[Frank Lee]

In the absence of a BSFC chart, I think 1000-1200 ft/mn piston speed is a good engine rpm to shoot for, for maximum fuel efficiency.

There are online calculators for figuring that piston speed and engine rpm; when you have your target rpm range and you know your trans and axle gears, then you can figure how tall the best tire should be.

I didn't know these things when I tried taller tires on my F150. Turns out it's engine is already turning too slow. When the tires it has wear out I'm going back to stock size.