TexaCali
Posts: 113
Joined: Mon May 12, 2014 5:06 pm
Location: San Jose, CA

changing wheels and tires

Tue May 20, 2014 7:15 pm

I'd like to give my FFE a bit more aggressive look and so I'm considering replacing the wheels with black 18" (which would require 225/40-18 tires). This raises several questions:

1. Does spoke design have a significant impact on wind resistance (and thus range)?

2. A 225/40-18 will lower the car slightly from the 225/50-17. Is this likely to reduce drag (and increase range)? Will the effect be noticeable?

3. How does one re-calibrate the spedo for the slightly smaller wheel?

4. Unfortunately the Michelin stock tires aren't available in this size. Any recommendations for a LLR tire in this size? Obviously I don't want to give up any range to rolling resistance if I can avoid it.

Thanks!

WattsUp
Posts: 2113
Joined: Mon Jan 07, 2013 2:58 am
Location: SF Bay Area, CA

Re: changing wheels and tires

Tue May 20, 2014 8:31 pm

It is LLR, or LRR?

LRR stands for Low Rolling Resistance, correct?
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TexaCali
Posts: 113
Joined: Mon May 12, 2014 5:06 pm
Location: San Jose, CA

Re: changing wheels and tires

Tue May 20, 2014 9:48 pm

Indeed. Typo on my part. LRR (Low Rolling Resistance) is what I meant.

EVA
Posts: 874
Joined: Tue Aug 06, 2013 9:10 pm
Location: Chicago Area

Re: changing wheels and tires

Tue May 20, 2014 9:55 pm

Why don't you use the size tires Ford uses as the summer tire (performance really) option for the ICE Focus?
235/40-18
They used this tire as optional equipment from Ford:
Michelin Pilot Sport 3

There is no offset or diameter change with that wheel tire combination.

Your questions - don't know the answers to a certainty just my opinion:

1) Spoke design must have some kind of affect - look at the ugly mostly flat wheels they put on the Prius. Those designs happened after wind tunnel tests and there must be some affect. The wheels for the FFE aren't unique - they are the same ones used on the C-Max (if I remember that correctly). You would probably never notice the range difference - but it is cumulative, a bunch of small things add up to one big thing.

2) Maybe lower will reduce drag. It will also allow you to hit more curbs and speed bumps. Like above, you probably won't notice the difference, it is a small cumulative thing.
The Tesla used to run at a lower height at highway speeds. After the two cars caught debris, piercing the battery, and the cars catching on fire; Tesla changed the program to lower the car at 100 MPH (you can adjust that value). At 100 MPH when the car lowered I didn't see the consumption go from 430 Wh/mile to 400 (not far off from what it uses at 100 MPH). There was no noticeable difference.

3) you don't recalibrate the speedometer - there is no setting to do that.

By the way - Michelin Primacy MXM4 are available in 235/40-18. That's the tire Tesla uses as standard equipment for 19 inch wheels.
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michael
Posts: 1113
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Location: Los Angeles, CA

Re: changing wheels and tires

Wed May 21, 2014 11:24 am

I've noticed the speedometers in my recent cars have been extremely accurate. I've wondered whether they constantly self-calibrate against the GPS.
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TexaCali
Posts: 113
Joined: Mon May 12, 2014 5:06 pm
Location: San Jose, CA

Re: changing wheels and tires

Wed May 21, 2014 6:32 pm

EVA wrote:Why don't you use the size tires Ford uses as the summer tire (performance really) option for the ICE Focus?
235/40-18
<snip>
By the way - Michelin Primacy MXM4 are available in 235/40-18. That's the tire Tesla uses as standard equipment for 19 inch wheels.
Thanks! That solves a lot of problems and keeps the circumference much closer to stock. Hopefully the Primacy's grip a little better without increasing rolling resistance. The OEM (Energy Saver) tires seem to break free at the slightest hint of accelerator travel. I'm scared to think what they would do in a panic stop or evasive swerve. My traction control light comes on just turning out of driveways and accelerating into traffic.

BTW - in doing some research it appears going wider (for the same load) may actually reduce rolling resistance, and the reduction in rolling resistance may be greater than the increased wind resistance.

Now to find some light weight wheels I like and don't cost an arm and a leg.

EVA
Posts: 874
Joined: Tue Aug 06, 2013 9:10 pm
Location: Chicago Area

Re: changing wheels and tires

Wed May 21, 2014 9:45 pm

Wonderful - glad I could help.

TireRack is my best friend.

Actually the circumference is the same.
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2014 Tesla Model S 85

TexaCali
Posts: 113
Joined: Mon May 12, 2014 5:06 pm
Location: San Jose, CA

Re: changing wheels and tires

Wed May 21, 2014 10:00 pm

EVA wrote: TireRack is my best friend.
Yep, been spending way too much time looking at wheel and tire options on tire rack :lol: . I've also been researching 17" vs 18" wheels (esp in the ICE Focus owners forms) and I may just stay with 17" wheels (but in black). I've found a set of black OZ wheels I really like, but they aren't cheap. However, the 17" version is only 16.9lbs, which might help with all the stop and go in my typical driving. Decisions, decisions.

Oh, in case anyone else out there is considering how different colored wheels (or trim) might look, you should check out Plasti Dip in a spray can. Tons of videos on Youtube about how to paint your wheels/trim/etc with this stuff. Looks very professional, and if you don't like it you can just peal it off with no damage to your original finish. Not a permanent solution, but seems to hold up well and is a cheap and easy way to check out color changes.

scoops
Posts: 40
Joined: Tue Apr 08, 2014 12:48 pm
Location: Atlanta

Re: changing wheels and tires

Thu May 22, 2014 7:31 am

TexaCali: The weight of the wheels will have an impact on your economy during city driving... OZ is usually pretty light.

I'm considering getting some non-LRR tires so I stop peeling out all the time.

TexaCali
Posts: 113
Joined: Mon May 12, 2014 5:06 pm
Location: San Jose, CA

Re: changing wheels and tires

Thu May 22, 2014 4:28 pm

Indeed, weight is a big reason I'm considering staying with 17" wheels (vs 18"). I haven't been able to find the weight of the stock wheels, and I don't have an accurate scale for that range (plus I would be weighing the tire, TPMS, wheel weights, etc), so I really have no idea how the weights would play out. That said, the 17's I'm looking at are 16.9 lbs each, which I'm guessing is significantly lighter than stock. Using 18's would place the wheel at 21.8 lbs AND increase the tire weight by 1 lb. That might still be lighter than stock, but I don't know.

Another consideration is I can keep the same tires with the 17's (at least until I get tired of them). The cost delta between 17's with my tires vs 18's with new tires (and new TPMS sensors) is about $1k! The only real reason for 18's would be looks, and the 17's would probably perform better in most aspects (acceleration, economy, ride comfort, etc).

If you find some non LRR tires that don't kill the mileage and improve traction, please let us know. I'm afraid it may be a choice between range and grip.

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