time for new tires

colonel6632 · 10-09-2009, 12:49 AM

hey everybody. car needs new tires. so i figure i'd buy some new ones.

my question is. i live out in the middle of nowhere's and do alot of highway driving. my car currently gets pretty good gas mileage (about 37 US MPG, 45 UK MPG) on average. it depends on the wind and stuff. but i break 34mpg on the highway all the time. but i want a little better mileage. my car goes at about 2250rpm on the highway. i want that to be 2000rpm for better gas mileage.

so i want taller tires to drop the rpm.

heres what i'm looking at
http://www.canadiantire.ca/AST/brows...ler%2BSR-A.jsp

in the size p235/75/R15 for my 15" rims. this tells me i should drop my rpms to just below 2000rpm. (i used this site http://www.miata.net/garage/tirecalc.html

does anyone see a problem with putting taller tires on. like clearance issues? or if i have alot of weight the taller tires rubbing on stuff. or issues turning?

i have a set of 16" rims and a set of 15" rims i can put the new tires on.

sorry for the long post. i appreciate it if you actually read the whole thing

kwhauck · 10-09-2009, 01:15 AM

can't run that tire it is way to tall....

it's almost 29" tall

26" is pretty much the max...

Redog · 10-09-2009, 01:33 AM

What MPH are you running at for that 2250?

Messing with the tire size is NOT the way to go with this.

What about a K&N filter or lighter foot.

I'm running about 2000 (maybe like 2050) at 70 MPH, before the K&N it was around 2700 at the same speed

colonel6632 · 10-09-2009, 01:38 AM

not sure how changing your air filter lowers your rpms. thats a new one to me.
and i dont use my foot on the highway. lol. i already have a k&n filter. i know i'm pretty much maxing out my gas mileage for this car. i've got a few other things to try yet. and i usually drive at 60mph or 70 mph. at 70 mph i'm normally around the 2500rpm. it's a 2.2 5-speed. your rocking a 3400 which is probably geared lower already

dragon8807 · 10-09-2009, 02:24 AM

beside being too tall you can't run that tire anyway cause it's designed for a light truck/suv

Redog · 10-09-2009, 03:29 AM

Ahhh sorry, post skimming.

Yeah a K&N will lower the RPM's at highway speeds.

The Cavy I had, with the 2.2 (Non Eco) engine ran 3500 RPM's at 75 MPH with a stock filter, after a K&N replacement 2600 at the same speed, then after exhaust it dropped to 2400

Ian 2000GL LA1 · 10-09-2009, 06:45 AM

i have a 3.4l but i threw a k&n stock replacment style filter in ($55) and i noticed better mileage, not that i keep track but it made my gas last longer. with the same daily drive.

CactusWill · 10-09-2009, 09:09 AM

Raising your car would be counterproductive to gaining fuel economy. When you raise your car it increases wind resistance and aerodynamic drag.

If you want to get better fuel economy from a tire, consider trying these: http://www.tirerack.com/tires/tires....Com pare1=yes

And goto www.gassavers.org to read up on increasing fuel economy. Theres a dude on there getting 70mpg from an ecotec cavalier, but his mods are pretty extreme to say the least.

Quote:

Originally Posted by colonel6632

not sure how changing your air filter lowers your rpms. thats a new one to me.

It doesn't. The air filter may save fuel by giving a little more power, and it may save fuel while accelerating with that extra power, but once the car is at speed it has no effect whatsoever. Once you're cruising at freeway speeds, you're either got the clutch fully engaged with a manual, or the torque convertor locked up on an automatic. The air filter has nothing to do with the gear ratios of a transmission, and the road horsepower required to push a car on a flat surface at 70mph is only 20-30 horsepower, the only thing that will affect your rpms by that point is acceleration/deceleration or changes in uphill/downhill.

CactusWill · 10-09-2009, 09:14 AM

This is the guy getting 65mpg out of an ecotec cavalier: http://www.gassavers.org/garage/view/649

He has no tire mods listed other than over-inflating them to reduce rolling resistance. He also states that the addition of a K & N filter was a waste of money.

colonel6632 · 10-09-2009, 09:20 AM

just becuase tires are for light trucks doesn't mean they wont go on my car. every set of tires i put on my last car were a set of light truck tires. the street tires couldn't compare to the truck ones.

i'll read up some more about gas mileage stuff

kwhauck · 10-09-2009, 09:28 AM

Quote:

Originally Posted by colonel6632

just becuase tires are for light trucks doesn't mean they wont go on my car. every set of tires i put on my last car were a set of light truck tires. the street tires couldn't compare to the truck ones.

i'll read up some more about gas mileage stuff

did you read what i wrote, they won't fit.....

Cashdollar2009 · 10-09-2009, 09:32 AM

Quote:

Originally Posted by colonel6632

just becuase tires are for light trucks doesn't mean they wont go on my car. every set of tires i put on my last car were a set of light truck tires. the street tires couldn't compare to the truck ones.

i'll read up some more about gas mileage stuff

Haha alright go for it buddy.

[ion] C2 · 10-09-2009, 09:37 AM

Get a tire that's a hard compound with shitty traction. Less rolling resistance.

Beef up your car. Increasing the efficiency of the engine also increases fuel economy.

antichrysler · 10-09-2009, 10:24 AM

I think your focussing too much on fuel economy and not traction. We've both driven Saskatoon streets to know what they're like. If I was in your shoes right now I'd be looking for a good set of winter tires instead. Get a good set of Michelins in the summer. I'm not quite sure how truck tires are on a car (never tried).

Not quite sure how an air filter will lower RPMS at cruising speed.... but okay.

JLw7123 · 10-09-2009, 10:35 AM

get some all season tires

Vic28 · 10-09-2009, 02:52 PM

I need to laugh, so you think going to bigger size gonna give your better gas mileage? Dont you know you gonna get bigger tire = more weight more gas burn. Go buy the size and find out.