Need Help! Bigger Tires?

[DragBean]

Well i couldn't find the right rims for what i wanted so i just bought the biggest narrowest tires (p165 80 13) for the existing rims on the front. Im bummed i couldn't get bigger rims that work but i dont want to waste anymore of my time on this and i need tires. Still a 1 inch improvement though and tad narrower. I was at the junkyard today and noticed a 155 width tire on a r13x5.5 rim (165 is the lowest recommend 175 is stock). It seemed to be worn fine so I'm putting that size width on the back. I'll definitely find a good spot to do some crazy turns to make sure the back doesn't slip out or the 155s break their beads.

[dfeldt91]

I got my lug bolts for the new rims today so I've also got larger tires and rims on. Aside from the faster acceleration I did notice that I am using less gas by checking the Torque app for fuel economy. This was in urban driving with less stops up to 40 mph.

Another thing to think about is deceleration cutoff.....

If you don't know what that is: Deceleration cutoff is where the car will turn off the fuel flow when the accelerator is not pressed and RPMs are above a certain number, usually about 1600, so the car just coasts in gear but uses no fuel. Not sure if your car has this feature but with larger tires the engine will be spinning less for a given speed effectively changing when you will enter deceleration cutoff which may negatively affect the MPG. I did notice that in certain circumstances where I would normally be in Decel mode I was still using fuel. Instead of having no fuel flow I would see that I was getting roughly 60 MPG while coasting meaning I would have to downshift to second which would cause the car to slow down too quickly. It was late and I may have had my foot on the pedal while coasting so it might have registered that and kept it out of decel mode so I will have to test it in the next couple days.

This is with 195/60/14 --> 195/60/15 tires and rims.


Let me know how you get on with the narrower tire. I'm thinking about heading to the junk yard to grab some narrow taller 14's for my steelies.

[DragBean]

I'm so excited I got my new tires on by myself! I can't wait to see how much better my fuel mileage is going to be.

Not only are the tires overall lighter, but they all are narrower and the drive train has a larger diameter to reduce engine RPMs.

How much does everyone think my fuel mileage will increase by?

PS. If anyone is wondering how they can put their tires on themselves and save a bunch of money, check out the videos I made.

Setting the bead with a leaf blower:

https://www.youtube.com/watch?v=lCYNkpNL2V8

Redneck style of removing a tire:

https://www.youtube.com/watch?v=lCYNkpNL2V8

Using an oven and freezer to assist with putting a tire on a rim:

https://www.youtube.com/watch?v=zMASfv2cLGk

[dfeldt91]

I noticed in my own testing that I was never really utilizing fifth gear because it caused my fuel economy to go down. The only time I used fifth was following behind trucks at highway speed. So I might as well have a four speed transmission now that I have larger tires. I'm not complaining though. I am getting better gas mileage in fourth with the larger tires than in fifth with the smaller tires.

My drive shaft fell off the transmission the other night as I was leaving a rest area so I ended up staying overnight in my car, so with four hours of idling for heat and 265 miles I have used 9.5 gallons. Taking into account the .5 gallons per hour of idle, I got about 35 miles per gallon so I would have to think the extra 6 miles per gallon over EPA were in part due to the larger tires and my new driving techniques. Only 150 miles of the 265 were with the new tires.

Also, keep in mind that lower RPM's does not automatically equal higher fuel economy. Engine load has a lot to do with it:

If I am in third gear going up my hill which is pretty steep then I get about 28mpg with a very slight slow down. If I throw it into fifth then I get about 12mpg even with the lower RPM's because the engine is requiring more fuel to do the same amount. This is more so evident when you have the larger tires on when going up hills.

On long flat roads drafting is your friend, especially with the larger tires. Your car will use much less fuel to turn the extra tire size.

[dfeldt91]

And to answer your question:

I am guessing you will see a 4-5% increase with the same driving.

This link says your RPM's at the tires will drop 3.3%: https://www.tacomaworld.com/tirecalc...0r13-165-80r13

[DragBean]

@dfeldt91

That's a bummer about the drive shaft. What kind of car is it? Did it come off while turning real hard?

I do have good news. The car glides now. I don't think i even need to get the wheels balanced. I'm barely pressing on the gas on the highway and she's super smooth. I'm pretty sure I'm going to get 45 mpg tank in the near future.

[dfeldt91]

The drive shaft fell off because I assumed my friend tightened the bolts since he put that side back together after swapping the clutch. He assumed we were just finger tightening them at that point and didn't bother to tell me. I pulled in to the rest area for a break and backed up then put it in gear and it just revved as if the car was in neutral. It made a clunking sound so I assumed my new lug bolts were the issue and maybe one snapped. Looked at them and they were fine then got under the car and saw six 5/8" ball bearings on the ground...oops. The clunking ended up being the last bolt that was holding it together snapping since the others had already backed themselves out. It is a 1997 VW Golf. Cheap fix though, CV shaft was $15 at the junk yard and I only had to undo the large bolt at the end where the brakes are to get it out.

If the tires feel smooth at speeds of 60 mph then I would say they are close enough to not need to be balanced. At least I wouldn't bother. I paid $65 to get mine dismounted, cleaned, remounted, sealed and balanced for three tires. My new rims and tires were on a car that rolled so there was dirt in the bead causing them to lose air. They are doing well now though!

What were you getting before the tires mpg wise??

[DragBean]

My record was 40 mpg a few tanks ago. I've been getting 36, 38 mpg tanks with one 32 due to me running wide temporary tires.

That's good the car's fixed. It sounds like you didn't have to pull the tranny or anything.

[DragBean]

My record was 40 mpg a few tanks ago. I've been getting 36, 38 mpg tanks with one 32 due to me running wide temporary tires.

That's good the car's fixed. It sounds like you didn't have to pull the tranny or anything.

[DragBean]

#$%$%^^^

OK so I"m angry. If anyone is following they could see I put my tires on myself. So somewhere in the process of me putting my tires on myself to getting rear endeded to the point where my trunk does not open right now... i'm getting worse gas mileage. 36 compared to a 41 max recent. To Be more true to reality.. I warped my rear rotors (both passenger and driver rear {I'm hoping gfront'ts aren't F'd).

Long story short what should have been a easy hpyothesis and implementation turned into odo-meter let-Down.

But the good news for anyone considering this mod is there is still hope.

My Hubs's got warped.

So I never got to see if narrower tires and larger drivetrain/ reduce RPMS reduces MPG.