How are my wheels impacting FE?

[mcrews]

Originally Posted by aardvarcus

Wheels/Tires:
Stock tire size on your car would be 185/65/14, or 23.4” diameter. Your 205/45/16s are 23.2” diameter, so less than a 1% change. The downside is that most low profile tires like you now have are geared more for grip and performance, not for rolling resistance.

For example if you wanted to go with Michelin Energy Saver A/S the smallest tire for a 16” rim on Tire Rack is 205/60/16, which is 25.7" or 10% bigger. I know from experience there is a drastic change in acceleration when you upsize that much, if you even can fit something that large on your car without rubbing.

As far as handling goes, my Celica had fairy new low profile Kumho 205/50/16s on it when I bought it. When I replaced them with oversize 205/65/16s Michelin Energy Savers the handling of the car surprisingly improved drastically. Night and day difference, they were better on dry pavement, wet pavement, cornering, everything except squealing. It was simply a better tire, and that advantage overtook the fact that the previous ones were low profile.

If you like the wheels and want to run them, go for it. If you are looking for aero, personally I think the 7 Slot 15x6 inch, 4x100 bolt pattern (45mm Offset), One Piece Alloy Factory OEM Wheels look pretty good and appear more aerodynamic. Keep an eye out for a pair cheap. Pair that with some 185/65/15 or 195/65/15 Michelin Energy Saver A/S tires (or your LRR of choice) and you would have a good factory looking LRR setup.

Engine:
Your 1.6L was designed to be a mainly high revving engine, low end torque was never the specialty of semi-modern four banger imports. My celica hates below 2k as well.

Gearing:
What are your cruising RPMs right now at your most common speeds? I regeared my Celica because my highway RPMs were 2900@65 and my interstate RPMs were 3600@80. Now I sit at 2600@65 and 3100@75 (great mod btw, 80->75). I wouldn’t recommend you significantly regear like 10% using tires unless your RPMs are way too high, as you take an aerodynamic hit, the weight increases, etcetera. If your RPMs are already decent, going up 3-4% would help without significant impact.

Great post!!!!

[aardvarcus]

Originally Posted by MetroMPG

OT: aardvarcus, did you post a thread about regearing your Celica? I'd like to feature it if you did, and if you have MPG before/after results.

Sorry, no I didn’t do a specific thread on it, just posted about it in some other tire size change threads. I have some data, but unfortunately it was an apples/oranges comparison so I don’t have any concrete data about how much was truly due to the diameter change versus the rolling resistance change. I did just get a spare set of wheels, so if I can find some smaller diameter Energy Saver A/S tires cheap I will do an Apples/Apples test.

[9646gt]

Sorry it took me so long to get back to you guys as I had a death in the family. So I am trying to figure out if its with trading my aftermarket wheels for stock wheels that also have new tires if I can find someone on craigs list who will do it.

Issue in having is I think my car stock had steel wheels with hubcaps right? I see there are some hx model wheels I could hunt down but they are 1" smaller as they are 14's. But they are alloy and much lighter I would think than steelies. Would the difference in coasting ability and fe difference be noticeable if I moved to the steel wheels with a tire with more sidewall since they also will be more narrow?

Or should I try and find a trade for some hx wheels? They will be lighter but the 14" seems like it would raise my rpm at highway speed? Need so advice guys Thanks!

[cbaber]

The wheel size alone doesn't effect your RPM or speedo. The overall diameter of the tire and wheel is what you need to look at. The overall diameter of the wheels/tires you have now is almost the same as stock, so your speedo/RPM is not affected by your current setup. If you switched back to stock 14 inch steelies, or the 14 inch HX wheels, the outer diameter would still be the same as your current setup. Even though the rims are a smaller diameter, the tires are taller, resulting in the same overall diameter. This calculator should help illustrate the concept:

Tire size calculator

I vote to trade for HX wheels with tires. The HX wheels are lighter than your current wheels, and lighter than the factory steel wheels. Plus, they look a lot better.

[mcrews]

Originally Posted by cbaber

The wheel size alone doesn't effect your RPM or speedo. The overall diameter of the tire and wheel is what you need to look at. The overall diameter of the wheels/tires you have now is almost the same as stock, so your speedo/RPM is not affected by your current setup. If you switched back to stock 14 inch steelies, or the 14 inch HX wheels, the outer diameter would still be the same as your current setup. Even though the rims are a smaller diameter, the tires are taller, resulting in the same overall diameter. This calculator should help illustrate the concept:

Tire size calculator

I vote to trade for HX wheels with tires. The HX wheels are lighter than your current wheels, and lighter than the factory steel wheels. Plus, they look a lot better.

This is spot on.
THe MAIN issue is not the rim....it'e the overall diameter after you have installed the tire!!
TO improve mpg you need to lower rpms at highwayspeed.