View Single Post
Old 08-22-2022, 06:57 PM   #10 (permalink)
Master EcoModder
redneck's Avatar
Join Date: Jun 2009
Location: SC Lowcountry
Posts: 1,783

Geo XL1 - '94 Geo Metro
Team Metro
Boat tails and more mods
90 day: 72.22 mpg (US)

Big, Bad & Flat - '01 Dodge Ram 3500 SLT
Team Cummins
90 day: 21.13 mpg (US)
Thanks: 225
Thanked 1,343 Times in 706 Posts

Originally Posted by zonker View Post
Thanks for the solid advice. I wonder which one did the most for you? As for tires/wheels, the car has the 3.79 final drive and I'm running 155/80-12 Nankang tires, with an OD of 21.8". With the ratios and diameters calculated, it is turning 2750 rpm in 5th at 62 MPH.

I get why you'd want to increase the OD of the tire, but would adding rotating weight also sap some of that savings? the 12" set I have are a combined tire/wheel weight of 20.5 lbs! I've never seen anything that light on a passenger car.

Lets say I ran the 13" Metro wheels with a 155/80-13 tire, the diameter would be 22.8" and the weight would be 5 lbs more, at 25.5 lbs. The RPM I now would be turning at 100 KPH (62 mph) is 2650 rpm.

Is reducing engine RPM from 2750 to 2650 RPM at 100 KPH going to offset the additional 20 lbs of rotating weight I will be adding to the car? Plus the expense of all that new stuff would probably not pay for itself during the life of the vehicle. Perhaps it's something I can play with when these tires have reached their expiration.

Good advice there - all that has been accomplished so far. I also added Motorkote friction reducer to the engine oil and the synchromesh. I've zeroed the alignment and cut the coils to lower the car about 1".

Of that listed, I've completed the passenger mirror delete and inflated the tires to 40 psi. I was thinking of disabling the steering wheel lock so I can turn the car off with key at will and not worry about a potential calamity. Grill block and heated air intake tube are on my radar of things to try next. Right now, I've just removed the cold air fender snorkel and added a 1" lower lip made from landscape edging.
If your tires are good, I would wait to replace. No sense in wasting good tires that are paid for. In the mean time I would be looking for 13” wheels. 12” tire selection is poor, 13” is slightly better. I don’t remember what my wheel weight is. I’ll try to get a number for you.

Personally, I wouldn’t mess with the factory ignition switch. Installing a remote stop start switch(s) is easy. Plus it could be used as a anti theft device of sorts to boot.

If you’re interested in aero stuff check out my thread.



Woke means you're a loser....everything woke turns to ****.

Donald J Trump 8/21/21


I’m not a climatologist, aerodynamicist, virologist, physicist, astrodynamicist or marine biologist..


I play one on the internet.

  Reply With Quote
The Following 2 Users Say Thank You to redneck For This Useful Post:
Ecky (08-22-2022), freebeard (08-22-2022)