Tire and rim weights
 

Recently, I traded the 14x5.5" Mazda Miata wheels that I had been running for over a year on my Escort for a set of 14x4 space saver wheels.

Why the change?

My next tire is going to be 165/65R14 Bridgestone Potenzas. For those who do not know, these tires are the upper echelon for fuel efficiency. There are none better, except maybe Bridgestone B381s. The Potenzas have a knack of wearing the outside of the tire out before the center, even with high air pressure. Dropping 1.5" of rim width should counteract their tendency to do this and give a longer life. Besides, the Potenza's tread width is only 5" according to tire rack. A 5.5" rim is too wide for that!

While I was getting tires and rims swapped around, I took my handy Wal-Mart fish weighing gauge and weighed the rims, tires and the new setup. Here is what was found -

The old rims weighed 12-13 pounds.

http://s26.postimg.org/4s4lm1lzt/0522150935.jpg

The spare tire and rim combo (14x4 steelie & 115/70D14) is 23 pounds.

http://s26.postimg.org/wqyrcwnmh/0522150936.jpg

My tires (185/70R14 Blacklion Cilerro BH15) are ~16 pounds.

http://s26.postimg.org/yg7ukz3bt/0522151005.jpg

The spare tire (115/70D14) by itself is 7.5 pounds.

http://s26.postimg.org/nunz8yx09/0522151008.jpg

The weight of the 14x4 rim & 185/70R14's are a tad over 31 pounds.

http://s26.postimg.org/g5r4x8wih/0522151017.jpg

This means I gained 2-3 pounds per corner by going with the skinnier wheels. So far mileage has taken a small hit during the everyday. Maybe 1-1.5 mpgs overall. Part of the reason is less with the weight and more with the drum brake now rubbing ever so slightly IMO :p

There may be increased hysteresis (tire flex) with the new setup due to the narrower rim pulling the sidewalls inward. It is hard to tell right now, and I cannot do A-B-A testing without it costing $$$.

I'm digging the look though:thumbup:

http://s26.postimg.org/70is3dt3t/0522151048b.jpg

I prefer light weight wheels for the ease of acceleration For my city driving

It will be interesting to see your fuel logs, my guess is you will notice no real gains or loss from the wheels

I like the look! Can you get more pictures farther away?

Also - are donut wheels safe to drive on permanently? Aren't they a lighter gauge of steel?

Wheel/tire/hub/brake/drive elements assemblies are reservoir of rotational kinetic energy. More simply, flywheels.

The measure of this rotational kinetic energy is called moment of inertia.

Moment of inertia goes up in proportion to the assembly weight and the square of the diameter.

High moment of inertia is a killer in city driving where you have a lot of acceleration and deceleration. Being inertia it resists changes in velocity - both ways.

You can use this moment of inertia to your advantage if you learn to coast more. All that coasting allows you to 'harvest" the energy you poured into the rotating assembly upon acceleration.

Aero > Weight.

Here you are Miller88!

http://s26.postimg.org/qy81llfvd/0526151412.jpg

They seem to be as sturdy as my old OEM steelies. Time will tell, though I do think they are strong enough for daily driving. The Donkey CRX runs Honda Insight space savers on his VX and I am yet to hear of anything going wrong with his wheels.

Chrysler Kid - I do not do much city driving myself. Lighter wheels would help out in that situation. I'm not expecting any gains until I switch from the Chinese tires to Potenzas :)

Big Dave - I had the thought that the moment of inertia would increase when they were being put on and realized they were heavier. I already coast a bunch, so they may help out as I get used to them.

cosmick - Yes sir! I would say the space savers have good aerodynamics, being closed off and producing little turbulence. They also tucked mt tire in by slightly less than 1/2". That will make front skirts easier to make, increasing my aero!

Just an observation My 15" by 5.5" steelies with hubcaps were nearly 6 lbs heavier per wheel than the Sparco Alloys I replaced them with ,sized 15" by 6" . I run 65 series LRR Goodyear fuel Max on both sets of wheels and did see a slight MPG improvement but I didn't track the improvement over the long term. The car handles much better on the wider wheel. Also as most of my daily drive is 65 MPH or better at times. I would not want to chance running on donuts. There is simply not enough tread to maintain traction in an accident avoidance situation.

Yes but acceleration in general is not a linear aspect, those hills you drive up on the highway are now going to take twice the effort to climb, so what you see in benefit from coasting may quickly turn into loss from trying to stay at speed up hills

For 14" I would definitely go either HX rims or Insight rims. I believe that a HX rim with a new RE92 on it is less than 20lbs. Insight rim is like .75-1.25lbs heavier.

You want really lightweight 4" rims, get the OEM Honda Insight spare rim... it's aluminum alloy, aero, and weighs almost nothing.

Even better? It's BRIGHT YELLOW.

2000 Honda Insight Spare Tire Wheel 2001 2002 2003 2004 2005 2006 | eBay

Best info I can find is that 14" HX rims are ~11.5lbs, and 13" VX rims are ~9.75lbs.

Most claim Insight wheels are ~11lbs, but they have the advantage of not needing smooth wheel covers. MetroMPG weighed some Insight rims and tires and came up with ~9lbs for the rims alone, but his scale was uncalibrated. However, I've seen several reports of Insight wheel + tires weighing in at approximately 22lbs, and officially, RE92's weigh 13lbs, which agrees with MetroMPG's measurements.

Eli over on InsightCentral made this spreadsheet with rim weights:

https://docs.google.com/spreadsheets...CNKaoIED#gid=0

I was looking at rims for my car and the lightest ones I found were Enkei Racing RPF1's. 9.5 lbs.

http://www.tirerack.com/wheels/Wheel...9&autoModClar=

Yeah or you could save $800 and just buy the factory enkei civic vx/hx wheels.

You will need to run a spacer and slightly smooth over your brake caliper but the hx wheels will fit the fit

This is not correct.

Yeah, the RPF1's are pretty pricy. Aren't the vx/hx wheels 14"? Those RFP1's are 15. The fit is already geared terribly low. Smaller wheels would make it worse.

I was looking at the Insight rims, both the stock alloys and spares. They are asking a high prices for them though, when the one I have cost only $20 a piece, and 1 came with the car :) One thing I stall at is running a 5" wide tire on a 5.5" rim. It seems to me like the tread would already be in a position to wear more on the outside. This would be magnified with the RE92s.

Great info in that spreadsheet, Ecky! Thanks a bunch:thumbup:

Chrysler Kid, I would love to run the VX wheels, but they are 13s. Which means less tire selection, and not Re92s.

Samwichse, can you explain why Chrysler Kid is incorrect in his posting that acceleration is not linear?

I had an idea on the way home last night. Being in the classic truck world for a while, I have seen people take the stock 15x8 steel wheels and add on to them to make them 15x10 and even 15x12. To put this in the Eco-perspective, why not take my Aluminum MX-3 wheels and have them modified skinnier, to 14x4 or so? I know aluminum can be welded and know welders who might could make this happen.

Thoughts?

Vx wheels are 13, hx wheels are 14s:thumbup:

Wheels have nothing to do with gearing. That is determined from the overall tire size. If you decrease the aspect ratio proportionally to increasing wheel size, then your gearing is left close to the same.

yes it is.

I found this doing a quick Google search: Narrow your rims!. I am going to contact these guys and get a quote on how much it will be to take 1.5" off of my MX-3 alloy wheels. I expect it to be cheaper than getting a set of Insight spares or RPF1's.

It became very apparent to me today that my coefficient of rolling resistance (Crr) has increased since I went with the new wheels :( Even with running at higher air pressures than normal, coasting distance is not as it was, which is making my P&G less effective. The tires are also running a lot warmer since the switch. So back the MX-3 wheels I go...

So did I understand that right, you put a normal 5in wide tire on a 4in space saver spare rim?

Did you change both tires and wheels? If so, then what tires did you change from and to?

Be aware that when you get new tires, you will take a fuel economy hit from the increased RR of the tires - as in, all other things being equal, new tires have larger RR than worn tires.

You are correct nimblemotors.

I changed only the wheels, CapriRacer. The tires were swapped from the MX-3s to the space savers. They had close to 15,000 miles when I swapped, so RR should not had changed.

With the 14x5.5 rims, the tires barely got warm after driving 40 miles. With the 14x4 rims, the tread gets actually hot in that same drive, driven the exact same way. The increase in heat is what is cuing me in on an increase in RR.

What is your expert opinion on the matter? I did not expect the tire's heat to increase as it has. The only thing I can think of is a combination of increased hysteresis and the tread being affected by the pulled in sidewall.

If the wheels are wider than the tread, there's a bit more stretch in the sidewall... which stiffens them. At least that's the theory, and there are racers who use that to get more performance out of the same tire.

Jaguar, for the XFR-S (the "S" signifying that this is the "Sporting" R-model... :p ), widened the wheels about an inch without changing the tire model used, as part of the handling upgrade package.

I guess you can figure out if it's that or the rubbing that's causing the extra heat by pumping the tires right up and observing the extra heat goes away.

First, the stock tire needs a 5" to 6 1/2" wheel and you are using 4" I suspect the tread is overly arching and the over all movement of the tread through the footprint has increased = more RR.

I wonder if the narrow rims bulge the tire too much?
I need some narrow 15in tires to put on the 4in wide rims, no cheap option it seems. How long will the spare tires themselves work?

Tire manufacturers specify a recommended rim width range for each tire size. A 185/70 R14 tire typically requires a minimum rim width of 5". In this case, 4" wheels are a liability and something I personally wouldn't consider. I can image how poor the handling must be. It's interesting that the coasting distance decreased. Thanks for sharing that info!

donuts/safety
 

I think the wheels are as robust as a standard wheel.The space-saver tires a speed limited to 50-mph though,and about 50-miles range as they are gummy and wear quickly.
CAR and DRIVER put a set of four on a Corvette and skidpad tested it,returning almost as much cornering G's as the wide,high-performance OEM tires.

I am going back to the 14x5.5 MX-3 wheels. I can't stand the hit in fuel economy that I have taken! I had a 48 mpg tank before I swapped and was keeping my average in the 47's easily, I even had multiple 50+ mpg trips. Since then my fuel economy has tanked. This tank is sitting at 45.2 right now, and it is a struggle to get a 50 mpg trip. I will say an easy 2 mpg hit, which hurts when you are so close to breaking that mythical 50 mark :(

Using a calculation of increasing 10% Crr equals a 1.1% reduction in fuel economy, it appears that I have gained a minimum of 40% Crr from swapping the wheels!:eek: I find that hard to believe... 3 pounds of extra wheel weight wouldn't be this detrimental though, and that is the only other thing that changed.

I am :confused:

I don't think you know that wheel choice is the only thing that changed, and there is a very good probability that, although the wheels are not helping city driving, other things have also changed. Imperceptible changes in your throttling, wind patterns, routes, average daily temps, humidity, the number of stoplights you hit during the tank, minutes idling, and perhaps most importantly... the possibility of a creeping mechanical issue reducing economy but not yet setting off a CEL. I have dealt with that last one kinda often this year. Grrr.

But in the end, I agree the greater wheel weight will hurt city driving fuel economy and must be a contributor here.

Sorry

My loss is everyone else's gain with regards to information :thumbup:

The handling has decreased slightly, not enough to get in an uproar about. I can't wait to get the other wheels back on, as I rediscovered that a Honda Insight's stock wheels are 14x5.5"... and they run the skinny Potenzas :o

As much as I hate to admit it, you are right California98Civic. There are too many variables to know exactly what is causing my mpg decrease. All I know is the coasting distance is down and tire temperatures are up. I'm glad that I do not do much city driving! Stoplights and stop signs are painful as always.

And I think some of the comments about the 5.5 tire on the 4.0 rim are really important. I hadn't notice that before writing to you. That sounds unsafe, tempting sidewall failure. I guess that's why the higher temps. Yikes. Glad you are removing them. Also glad you posted honestly about the difficulties. People learn that way--and not just you but others of us too.

It was worth a shot IMO. I see many people running 12.50" wide tires on 7" rims around here with no issues! 5.5" on a 4" rim didn't seem that bad in comparison.

Honesty is my policy, and I try to provide the data and reasoning for what happens in my situations. I know guest view our site quite a bit as well, so this will dissuade them from going down this path along with members.

I have to figure out what I am going to do with 4 14x4 space savers with no spare tires now...

Before you go switching back, I thought one of the reasons for the space saver wheels was making space, the offset making wheel skirts easier to do. Are the wheels set in farther with the space savers? If so, enough to effect wheel skirt design? if they are set in deeper in the fender, I think that would harm your aero if not running skirts front and rear

I looked through my old pictures and the space savings are minimal. It is along the lines of 1/2" farther into the fender, if that! So the front covers can be slightly more flush than with the 14x5.5s. I'd rather have a small redesign of my skirts and less Crr!

It may also be the tires that is making the rims have little effect. With the space saver wheel & tire, the inset of the combo was much greater compared to the MX-3/185 combo and the spare/185 combo.

Here is pictures of the different wheels with the same tires:

http://s26.postimg.org/4ldixnp21/1115141618.jpg
http://s26.postimg.org/ew8dygwpl/0415151229a.jpg

http://s26.postimg.org/f0twnsbyx/0602150733.jpg
http://s26.postimg.org/owuznfhqx/0602150733a.jpg

Mount the spare wheels backwards for the deep dish wheel look!

The side walls don't look over flexed to me, however their foot print stays the same or can even get larger on a smaller width wheel.


I would also weigh the pros and cons of duct taping cheap stuff everywhere on your car. Getting sex from females often out weights the benefit of duct tape aero mods, if I recall you are in college and you should be getting laid by now

If you're already married I say step it up and do the whole car in duct tape, kind of like a vynl wrap

No sex for me! I'm remaining chaste until marriage and the duct tape and coroplast does a good job of keeping it that way:p I haven't always been this way, but it is important for me and my girlfriend/soon-to-be fiance:)

On with the rims: I do believe I am going to switch back to the MX3 wheels. I have until the 19th of June to return the spares to the JY and get my $60 back. The moment came when my brother ordered new 15x10s for his truck and they weighed 21 pounds! These 14x4s weight 16ish! The others were around 12! Nope, I want my lightness back. The RE92s will be just fine on them anyways since stock Insight wheels were 5.5 inches wide too. I'll post updates when it happens. Probably Wednesday.

Is there anyway to check tire footprints? Is love to compare my rims and see if there is any differences between the tire footprint.

Inkpad. A4 paper. Muscles. :D

I'm not going to get a chance to compare footprints as the space savers went back to the junkyard where they belong today! I put my MX3 wheels back on, which are 3-4 pounds lighter and 1.5" wider. All I can say is WOW! Coasting, DWL and acceleration are all improved noticeably and my mpgs are going up.

I plan on doing a second round of coast-down testing to see if there has been any reduction in rolling drag and aero drag.