MPGs run, Aspire SE

[TominMO]

Mis-spoke in post #29 for a tire recommendation size. Should be 185/70x14, not 185/75x14.

[TominMO]

Here is my Aspire, completely modded for its test....

Notes:
Front tires are 165/80x15 on 1992 Accord space-saver rims.

Dagnabbit, another error! Fixed it for me.....

Other JY sources for wheels for this tall skinny 15" tire (from the 4-hole wheel list):
4x100......1998 Acura Integra 15 x 5.5 (11 Y-type spokes)
4x114.3....1989-90 Acura Legend 15 x 5.5
5.5" is as wide a rim as you would want to go with a 165mm-wide tire.

[Movin]

Lets get good enough mileage that yo mama slaps U !!

[TominMO]

Lets get good enough mileage that yo mama slaps U !!

Yo mama is so dumb, that when she heard most car accidents happen within 25 miles of home, she moved!

[TominMO]

Just came back a little while ago from doing another MPGs test. Same 99.1-mile hwy course, same perfect weather. Changes to the car were taller 165/80x15 tires, and more aero mods. I even made rear-wheel skirts this morning, out of some styrofoam I had laying around and the last of my white duct tape. Total aero mods to date have cost less than $30 in materials.

See pic below. (Included is a bonus pic of the cat who owns me.)

The results were surprising and disappointing. It took 1.88 gallons to refill, at the same pump I always use. This came to a MPG figure of 52.7! This despite the fact that on a roll-down test, it took a long time to lose speed, and was significantly quieter inside the car (lower radio volume needed), indicating less air disturbance. Engine RPM was down from 2700 to 2400, the same as my Festy's @ 60, due to the taller tires.

What I am thinking is: fill error. Need to do a longer test to get better results. It could also be that I had a fill error on the previous run (when refilling), so that my result of 55 MPG was not accurate. So for now the jury is out. I just need to do a longer test.

The other possibility is that the 15" steelies and tires are so heavy that it took more gas to keep them rolling than was gained in lower rolling resistance or lower RPM; but I don't really believe that. BTW these tires are just too tall for everyday driving; lotsa scraping of the fender liner happened on turns or small bumps.

Tmw I will do another identical test with my regular 185/70x13 tires on front to see if that was an issue. It will raise RPM back to 2700, but on the other hand it will also lower the front of the car by about an inch. Possibly that was also a factor, but again I doubt it based on how quiet the car was.

[Spike]

Actually considering buying 4 spare tires..

Never realized how awesome they look!! They look like '70's Mopar wheels.

-Joe

[TominMO]

Actually considering buying 4 spare tires..

Never realized how awesome they look!! They look like '70's Mopar wheels.

-Joe

You would need thick spacers tho, and long studs to mount them. And they are heavy steelies.

Just went out and weighed several tire and wheel combos. Used a cheap bathroom scale, so FWIW:
Weight.....Description
13 lbs......Aspire steelie, no tire
22 lbs......very used 185/70x13 on old aluminum AR rims
22 lbs......new 155/80x12 on a Metro steelie
28 lbs......new 155/80x13 Firestone Winterforce on Aspire factory aluminum rims (winter tires are apparently heavier)
31 lbs......new 165/80x15 tire on Accord space-saver steelie

So given the 31 lbs (+ 1-2 lbs adaptor) of the tire I just used in my test, compared to my usual 22 lb tire/rim, maybe the extra rotating mass was an issue after all. Makes more sense than a fill error, since all my previous results seemed reasonable given the curcumstances. But I'll see with the next test: full aero treatment, original tires.

Edit: here is another thread on tire and wheel weights that I started a few years ago.

http://www.fordfestiva.com/forums/showthread.php?30205-Tire-wheel-weights&highlight=tire+wheel+weights

Note that Aspire steelie and aluminum rims weigh about the same!

[Movin]

With that many changes did you re align the front end ?

[TominMO]

With that many changes did you re align the front end ?

Nope, left it as it was, which was pretty good.

Here is a useful list from Kumho on tire sizes, weights, and widths on specific size rims:

http://www.kumhousa.com/tire/category/car/A554FF1F-6F0E-4A7B-B4F2-F117F7942A2D

[Movin]

Its hard to tell looking at the pics but it looks like the front tires are offset to the outside
quite a bit. That could compress the springs more changing the toe. It probably just looks
that way. My car toes in quite a bit with 1/2 inch change down in height, so I don't mess with the coil overs much. Yours may not change as much, it all depends how you are set up.
I suppose you could rig a rope and fish scale to "weigh" rolling resistance. Try the different wheel tire combos you have collected. You are too careful and I can't see you messing up a fill, there has to be other reasons!

[TominMO]

You know, now that I think about it, with the tall heavy tires on front, it did seem to be pulling fairly hard to the right....think I'll go out and check the alignment again, with the normal tires on.

[TominMO]

Just checked the alignment. It is still 1/4" total (1/8" per side). I will change it to zero after tmw's test, because I have heard on the forum that it gives better mileage. Don't want to change it now since that will introduce another variable. Also, tmw I will pay attention to the steering pulling right issue. Hopefully it was related to the tall tires, as I now suspect.

Or maybe I was driving with the parking brake on....

[mikeyjd]

OK, so you still have Festy brakes if you have 12s on. I'd put those 185/65x12s on the rear and look for larger front tires, like even 155/80x13s, which are 22.7" tall vs. 21.5" for the 185/65x12s.

But frankly I'd call the sweet spot about 24", which is a good 10% taller than stock 12s, very available, and can be used on "normal" rims. The Kumho Solus KR21 comes in 185/75x14. It is an excellent, long-wearing all-around tire, and at 24.2", you will have little or no front fender clearance issues, since the wheel/tire won't be sticking out from using a large spacer. Worst case, you might have to roll the front fenders a little. I think that the higher gearing it provides will more than offset the extra drag of a wider tire (compared to a 155).

Check out this selection at tires-easy: http://www2.tires-easy.com/cgi-bin/r...hen=View+tires
The Hankook is also good and quite cheap. I might stick these on my Capri 14" rims for the Festy.

so capri 14's would be an ideal swap if i wanted to use my current break setup without any kind of adapters?

[mikeyjd]

Just came back a little while ago from doing another MPGs test. Same 99.1-mile hwy course, same perfect weather. Changes to the car were taller 165/80x15 tires, and more aero mods. I even made rear-wheel skirts this morning, out of some styrofoam I had laying around and the last of my white duct tape. Total aero mods to date have cost less than $30 in materials.

See pic below. (Included is a bonus pic of the cat who owns me.)

The results were surprising and disappointing. It took 1.88 gallons to refill, at the same pump I always use. This came to a MPG figure of 52.7! This despite the fact that on a roll-down test, it took a long time to lose speed, and was significantly quieter inside the car (lower radio volume needed), indicating less air disturbance. Engine RPM was down from 2700 to 2400, the same as my Festy's @ 60, due to the taller tires.

What I am thinking is: fill error. Need to do a longer test to get better results. It could also be that I had a fill error on the previous run (when refilling), so that my result of 55 MPG was not accurate. So for now the jury is out. I just need to do a longer test.

The other possibility is that the 15" steelies and tires are so heavy that it took more gas to keep them rolling than was gained in lower rolling resistance or lower RPM; but I don't really believe that. BTW these tires are just too tall for everyday driving; lotsa scraping of the fender liner happened on turns or small bumps.

Tmw I will do another identical test with my regular 185/70x13 tires on front to see if that was an issue. It will raise RPM back to 2700, but on the other hand it will also lower the front of the car by about an inch. Possibly that was also a factor, but again I doubt it based on how quiet the car was.

Also be aware that rolling resistance can vary allot from tire to tire. Things like tread wear and pattern play a huge roll. Some people report as much as 3-4 mpg change from same size tires in different brands just based on the rolling resistance of specific brands. I think that it's even possible that you may have dropped your rpm's to the point where you would need to go even faster to hit maximum engine efficiency load. I'm no expert and don't know what the bfcs's for the 1.3 is but it could be closer to 2700rpm than 2400rpm. If that is the case you would actually just be moving your ideal speed into a higher mph range. Some engines operate at max efficiency at over 3000 rpm's! My guess is that is likely an issue of increased rolling resistance along with moving outside the ideal rpm range for that speed. It's hard to imagine since these seem to be geared somewhat short, but from what I've been told the way the engine is designed limits what can be achieved with taller gearing.

[Movin]

If the rolling resistance is not abnormally high the sweet spot should be 1700 to 2100 for best
MPG's. Even with a trailer on cruising on the hiway is around 2 grand.