Wheels & Tires

[Snick]

I won't pretend to completely understand your calculations, Snick.

I do get the general theory you have though.

My question is do those calculations take into effect the fact that the Elio has 3/4 the rubber on the road as a car?

YES!!! That's one of the main points people are forgetting. 3/4 of the tire area and 1/3 of the weight of a saloon car!

You do NOT need the same width tire that a 3600lb, 4 wheeled car does. I will break down the math of that later.

 

[2.ooohhh]

Okay guys, this is why I've been harping on tires -- I have been inputting the Elio's parameters into one of the most rigorous mpg estimation engines I could find. It is the one in my signature link called Road Load Calculator. Here is the copy/paste for the urban UDDP driving cycle:



And here is the copy/paste for the highway driving cycle (HFET):



As you can clearly see, tire rolling resistance drag is the 2nd most drag on the Elio! Tire rolling resistance will be THE "alpha factor" for your mpg (because there are almost no gains to be had on aerodynamic and braking. It will NOT be subtle, it will be significant.

Also, with the bottom 1/3 of the tire unfaired every gain in width is an increase in aerodynamic drag, much more so that raising the roof because of the high turbulence and crummy form factor.

I do see your point about the overall cost. I just wonder how they will hit anything near the mpg goals with wide tires. As we all know, gasoline cars fair far worse in the "real world" than these models suggest. Gasoline cars almost never live up to their mpg claims because of throttling losses at partial loads and most drivers habits of jack-rabbit driving style.

Snick, I'm afraid your calculations are incorrect. While the calculator you link to is very good, the data you've inserted for some of the variables is off. The one that popped out to me at a drunk glance was "wheel diameter" Wheel diameter in performance calculations is always the diameter of the entire wheel & tire assembly. Using the tire several have pointed out in the thread this would be around 22.4" rather than 15". I'll be happy to check the rest for you in the morning if you like, I just need some sleep first before delving into the actual math.

Drag Coefficient: .28 (a prius is .25 so I would hope the elio will slide in at or under that)
Frontal Area:9 ft2
Rolling Resistance Coefficient:0.008
Wheel Diameter:15 in (should be close to if not 22.4")
Rotation Factor:1.0
Grade0 percent
Air Density:1.2 kg/m3
Ave. engine efficiency:27 percent
Ave. drivetrain efficiency:93 percent
Ave. regen efficiency:0 percent
Fuel heating value:114132 btu/gal
Driving Cycle:UDDS

 

[skygazer6033]

Wheaters, In many Asian countries sidecars (they're called tricycles in the Philippines) are the prevalent means of transportation. There are tires (tyres?) available in motorcycle sizes but with a flat automotive type profile and they're cheap. $40 each for 3.50×18 the last ones I bought. Don't know about the size you would need. Bias ply im sure.

 

[wheaters]

The small three wheelers are called "Tuktuks" in other countries and the maximum speed of them is very low. The speed of my car is probably double, as would be the case of the Elio, if not three times.

The speed rating has to match the capability of the vehicle, in addition to the load rating; as I wrote earlier I would only use moped tyres on a moped.

I have no preference to use bias ply tyres, btw, we have to use what is available. There isn't much choice in the 16" wheel size and hardly anything in a radial. We (Liege owners) have been running our cars for almost fifteen years and this is an ongoing issue. We have researched the foreign market as well as our own.

I have to import the rear tyres I use for trials, from USA. Due to the low demand, the tyre dealer we use will only obtain four or five sets at a time and this results in a very high cost for what they are.

One further complication is that our cars are used for competitions as well as on the road and generally speaking, changing wheel and tyre sizes (or tyre types) isn't allowed. If you do this, you may be excluded from the event altogether or put into Class 8, which is the unlimited class, where we would no longer be competitive.

 

[Jambe]

Tonight I read on Facebook the definitive word on the front tires size that will be used on the Elio. Apparently this is not speculation.

"They are Cooper auto tires that will be 135/(70 or 75)-15. The P4 is running wider 170 tires as the 135's Cooper will make are not yet done."
The rear tire will be wider. (unspecified)

This will not be available initially at your local tire store unless it carries Cooper tires.

However Sears does have this size...
http://www.sears.com.pr/bridgestone-temp-spare-tire-135-70r15-99t-bw/p-09581489000P (labelled s a spare tire).

 

[wheaters]

Unless Cooper are making a very special deal with Elio these tyres will be relatively expensive when compared to more commonly used tyres.

Cooper would be understandably cautious about going into high volume production of a one-off size until they know they can sell them, in other words Elios are going to be rolling off the production line in high numbers. They will have to price the early batches high in order to recover their costs.

The Indian tyre manufacturer I was in touch with wanted me to front up for the s
etting up costs and the moulds as well as paying for a minimum of 1000 tyres. As there are only 60 cars in existence, we had to look elsewhere.

The 135 section seems a good compromise. I think some older cars in UK could also use this size of tyre, which could help bring the unit cost down.

 

[goofyone]

Tonight I read on Facebook the definitive word on the front tires size that will be used on the Elio. Apparently this is not speculation.

"They are Cooper auto tires that will be 135/(70 or 75)-15. The P4 is running wider 170 tires as the 135's Cooper will make are not yet done."
The rear tire will be wider. (unspecified)

This will not be available initially at your local tire store unless it carries Cooper tires.

However Sears does have this size...
http://www.sears.com.pr/bridgestone-temp-spare-tire-135-70r15-99t-bw/p-09581489000P (labelled s a spare tire).

A few members have reported this news in the past as it has been discussed at tour events however we have yet to hear anything officially from Elio Motors. As noticed the 135/(70 or 75)-R15 sizes are actually common sizes for donut spares so it would not be difficult to produce a fully rated tire at this size in an existing tire plant as they are already producing this size for limited life spares.

Unless Cooper are making a very special deal with Elio these tyres will be relatively expensive when compared to more commonly used tyres.

Cooper would be understandably cautious about going into high volume production of a one-off size until they know they can sell them, in other words Elios are going to be rolling off the production line in high numbers. They will have to price the early batches high in order to recover their costs.

The Indian tyre manufacturer I was in touch with wanted me to front up for the s
etting up costs and the moulds as well as paying for a minimum of 1000 tyres. As there are only 60 cars in existence, we had to look elsewhere.

The 135 section seems a good compromise. I think some older cars in UK could also use this size of tyre, which could help bring the unit cost down.

As long as the Elio goes into production then volume should not be too much of an issue for Cooper as Elio is trying to sell out about 50K or so vehicles in advance of the first years production run which would result in over 100,000 new tires needing to be produced plus replacement tires to supply these vehicles for years to come.

135(70-75)R15 tires are likely a good compromise as a narrow tire that should be fairly easy to produce with existing equipment. Also 135R15 are somewhat common here in the states for classic cars such as VW beetles, Citroens, and Renaults even though this is a taller (80) sidewall.

 

[Tomg3rd]

The moment of angular inertia gets higher with heavier wheel/tire combinations, and as mass goes out more toward the rim as often happens with heavier tires and wheels (less hub material relative to rim), there is a shape factor too.

Here's the math: kinetic energy KE required to spin a wheel at angular velocity omega is:

KE = k*mass*omega^2

disc shape has k = 1/2; for reference, sphere has k =1/3 and toroid has k =3/4 if I remember these ones correctly.

so, KE when k is larger and mass is larger grows in direct proportion to their product (mass times k-constant).

This is just the analysis of KE required to spin the wheel/tire. Now, also consider that the wheel/tire/hub has to rotate around a point if using torsion beam suspension, or has to travel up and down linearly if using McPherson strut or similar. So, of course it's apparent that heavier wheel/tire/hub combinations have greater inertia and are harder to get them to change direction.

Yes exactly- Thats what I was going to say! (haha)

 

[wheaters]

As long as the Elio goes into production then volume should not be too much of an issue for Cooper as Elio is trying to sell out about 50K or so vehicles in advance of the first years production run which would result in over 100,000 new tires needing to be produced plus replacement tires to supply these vehicles for years to come.

135(70-75)R15 tires are likely a good compromise as a narrow tire that should be fairly easy to produce with existing equipment. Also 135R15 are somewhat common here in the states for classic cars such as VW beetles, Citroens, and Renaults even though this is a taller (80) sidewall.

Yes, but the point I was making was that Cooper would need to satisfy themselves that production of the Elio will actually begin (or get paid up front for the initial batch of tyres).

I would love some modern 135/15 radials for my Liege but our cars have 16 inch rims, die cast alloys made specially for the car by the manufacturer, due to the unusual wheel bolt PCD.

 

[goofyone]

Yes, but the point I was making was that Cooper would need to satisfy themselves that production of the Elio will actually begin (or get paid up front for the initial batch of tyres).

I would love some modern 135/15 radials for my Liege but our cars have 16 inch rims, die cast alloys made specially for the car by the manufacturer, due to the unusual wheel bolt PCD.

I am sure Cooper, and other suppliers, are being kept well in the loop on EM's development and funding and will be well satisfied by the time they need to fully commit to gearing up for mass production. I am sure the suppliers have an agreement with Elio Motors requiring certain objectives, and likely payments, which must be met before producing and delivering the products to Elio Motors for final assembly. My guess this is this will happen about six months or so prior to Elio Motors officially beginning production.

By the way I did forget to mention that while the tire sizes have not yet been officially confirmed one thing that has been confirmed is the fact that Elio will use 15 inch, 5 bolt pattern wheels.