Aptera Tires

[MegaAutoBit]

This last weekend I spent approximately a $1000.00 on new tires for my car, and I started to think about the Aptera. I remembered hearing that Aptera was planning on using Honda Insight tires, so I wondered how much a new set cost and how they were rated. I can only hope these aren’t the tires they decided to use.

http://www.tirerack.com/tires/tires.jsp?tireMake=Bridgestone&tireModel=Potenza+RE92&vehicleSearch=true&partnum=665SR4RE92&fromCompare1=yes&place=0&speed_rating=S&speed_rating=T&speed_rating=U&speed_rating=H&speed_rating=V&speed_rating=Z&speed_rating=W&speed_rating=Y&speed_rating=(Y)&minSpeedRating=S

[gg222]

I was thinking the samething. But if you look at it's rating, the place where it got it's bad marks was winter driving. The Aptera was really never made for that. If it snows, I'll use my other car (Honda CRV).

[MegaAutoBit]

I'm still not that impressed, if they are using the same wheel size as the Insight this would be the only tire available.

[KarenRei]

Not bad for a low rolling resistance tire, really.

[MegaAutoBit]

How much would the fuel economy go down if I switch to performance tires? Keep in mind I have a hybrid.

[garygid]

Presumably it is these tires, inflated to around 50 psi.

[MegaAutoBit]

With those tires at 50psi, you would be skidding across the road whenever it got damp.

[garygid]

Maybe I was wrong about the very high pressure, but
I thought I read it somewhere, and the "50" figure stuck
in my memory because it surprised me at being so high.
But, maybe it was "50 days until Christmas". :)

About the Honda Insight tires,
from www.insightcentral.net/KB/faq-ima.html

----------------
"Q: The Insight has "low rolling resistance tires". What does this mean?

A: One of the ways in which overall energy efficiency is improved in the
Insight is by using a low-rolling-resistance tire design.

The Insight's tires are designed to reduce rolling resistance by 40%
compared to conventional tires, while also reducing weight by 5%.

While tire material and tread design are an important part of the low
rolling resistance equation, one of the biggest factors is reducing the
amount that the tire deforms as it rotates. While you may think of tires
as being round, when loaded with the weight of a car, they are no longer
a circle. Rather, they deform so that the bottom of the tire is "squeezed".
To the right you'll see an exaggerated illustration of this effect.

The result of this deformation is that as the tire rolls down the road, it is
constantly changing shape. This continual deformation wastes a significant
amount of energy. In order to reduce the amount of this deformation, the
Insight's tires are inflated to fairly high pressure (38 psi front, 35 psi rear, by
Honda's specs). Disadvantages of higher pressure are that it decreases ride
softness, and increases tire noise. The Insight's tire design is also relatively
low profile, meaning that there is less sidewall to flex, further reducing
energy lost to this rolling resistance.

In terms of tire tread design and material, the Insight's original equipment
tire is the Bridgestone Potenza RE92. This is what Bridgestone says about
the Potenza RE92:

* High performance tire designed to complement today's sporty coupes, sedans.
* Circumferential tread grooves provide efficient channeling of water
to help resist hydroplaning.
* Bridgestone's variable pitch technology "effectively limits" road noise.
--------------------

[jsnable]

With those tires at 50psi, you would be skidding across the road whenever it got damp.

Actually, they're not that bad. I had the Bridgestones for quite a while on my Insight before I replaced them at ~60,000 miles (bought the car with 40k on it). Never had any issues in the rain... I now have some slightly wider Michelins on it and get ~15% lower mpg (55 vs. 68, accounting for size difference). They are quieter and handle better, but not significantly. I'd buy the Bridgestones next time - unless my Aptera is here first of course!

Also, one thing to note is that the 165/65R14 size is specifically for the Insight, and lower rolling resistance than the rest of the Potenza line. The only valid reviews would be from Insight owners. Much more info on InsightCentral for those who are interested...

Jay

[KarenRei]

Personally, I'd like to see some dashing young company (*cough* Aptera *cough*) do a paradigm shift on tires on their next vehicle. :)

The harder the tire/wheel is -- the less flex as it rotates -- the lower the rolling resistance. Steel wheels, like on trains, have an order of magnitude less rolling resistance than car tires. The big downside is that such rigid wheels get horrible traction.

Well...

Why not "Real-Time Traction Adjustment" (RTTA, to coin the term)? I can think of a dozen different implementations. All of them are based around sensors that detect wheel slippage. Here's one implementation: each tire has multiple inner tubes with varying degrees of inflation. The innermost one is what the car drives on most of the time, and has very short sidewalls and is quite rigid -- as rigid as possible while still being durable; perhaps not even rubber. This has little traction, but so long as there's no slippage, it stays like this. If slip is detected, compressed air cylinders rapidly inflate adjacent tubes on each tire, bringing more of the traction surface down -- progressively stickier and stickier, wider and wider. Slowly, so long as slip isn't detected, the air is pumped back into the cylinders until there's the minimum amount of grip to keep the car steady. So, if you were driving on ice and slipping like crazy, it'd keep as high of a traction surface down as possible the whole time, while if you were driving on a perfect clear road, it'd be almost lossless. And, since adjustments would be made quickly on the inflation side of things, you'd get extra grip near immediately, but since it would be slowly on the deflation side of things and trying to find a good equilibrium point, it wouldn't be constantly inflating or deflating tubes and wasting energy that way.

This is, of course, merely one possible implementation of such an approach. I mean, perhaps even more trivial would be just to have two wheels side by side where there would normally be only one, one sticky and one hard, with the sticky one ranging from lifted off the road to bearing nearly the full force of the vehicle, depending on the situation.

Of course, there are other issues to account for -- for example, road noise. But it'd be interesting to see what could be done.

[SpyderMike]

get air out of the tires altogether...old technology.

[KarenRei]

Well, the Tweel isn't quite there yet -- still not quite as low rolling loss as pneumatic tires, and not very good at high speeds. Do you have a different tech in mind?

[MegaAutoBit]

Aptera should use the Tweel, it maintains good performance, eliminates weight, and is recyclable.

http://www.gizmag.com/go/3603/

[MegaAutoBit]

Never mind browser was behind.

[Aptera 1103]

I love my Insight and have no problems with the tires at all. :happy0025: The only complaint I had was that when it came time to replace them I only found one tire to put on the car. The same Bridgestones and I could only fine them at the local Firestone dealer.

The main reason for the car is great MPG and these tires fit the bill. Maybe our next set of tires could be Tweels.

[CandidQuality]

Potenza RE92 is the tire currently on the Aptera. (can't tell the size though) But we are still in the prototype phase. Perhaps they will cut a deal to have something else made.

Edit: reviews for this tire are horrible, but that is no indication of how tires will indeed react on this vehicle. If it wasn't for the tweel's noise I'd take it now.

latest info on the tweel " Eventually, improvements in design will make the tweel outperform the traditional pneumatic wheel. Michelin has planned all the design flaws to be corrected by the year 2016,"

from http://news.softpedia.com/news/What-is-a-Tweel-77436.shtml

[gg222]

Thought this was a funny post from epinons.com regarding the Bridgestone Pontenza RE92's ...

The Subaru Outback XT is a great car, and these are great tires to learn to drive it with. You can drift corners at extremely low speed. I feel that this is an important safety feature. With good tires, you would have to go fast to drift corners in a Subaru, but with these "training tires" you can really get the car sideways at safe, low speeds. On snow, they are an absolute blast!!! You get the feeling of going really fast, but you aren't. Then after about 10,000 miles when these are bald and you go find something/anything better, you will have a good feeling for how to control your car in the unpredictable situations of every day driving. I highly recommend getting a set, burning through them in a controlled setting, then putting some good tires on your car.

You think he didn't care much for them?

[KarenRei]

Lol. :)

[appyfan]

Hey guys this might sound a little childish but I just couldn't help myself...

I was in my car today and felt like having a little bit of fun, so I stopped at this stop sign up hill with my clutch in, put her in first and then dumped the clutch to make this really big smokey burnout. I hadn't smiled so much since I first started driving. :evilgrin0013:

Question is... Do you guys think burnouts will be possible on the Aptera? An electric motor develops torque instantaneously and theres only one drive wheel so I'm wondering if it's a possibility...

[3-4-me]

I would think if you had the Aptera on a hill and nail it, it would break loose.
For sure if you get the tire wet.
The weight concentrated on the back tire, will make it grip pretty quick though.
You can burn out from a left turn lane if there is oil in the middle of the lane.
Just my experience with a 3 wheeler.
http://farm3.static.flickr.com/2385/2475460392_d247eaabed.jpg?v=0

[garygid]

Tire Specifications (hopefully correct, from (http://www.tirerack.com/tires/Spec.jsp?make=Bridgestone&model=Potenza+RE92)):

for Bridgestone Potenza RE92, size 165/65SR14:

(tire section = 165 mm wide, 165 x 0.65 = 107.25 mm high)
14" rim (355.6 mm)

Load Index 78 = 937 lbs (425 kg) per tire
Speed Rating “S” = 112 mph (180 kph) 78S SL
Treadwear: 260(%)
Traction: A (Above 0.47 0.35)
Temperature: B (Between 100 to 115 mph)

937 lbs. max load
44 psi max pressure
9/32" tread depth
13 lbs. weight
4.5-6" rim range
5" standard rim (-> 5.5" rim)
6.5" section width (-> 6.7" approx)
5" tread width
22.5" diameter

Traction Grades: on Asphalt, Concrete:
AA Above 0.54 0.41
A Above 0.47 0.35
B Above 0.38 0.26
C Less Than 0.38 0.26

Temperature Grades:
A Over 115 mph
B Between 100 to 115 mph
C Between 85 to 100 mph

926 rev per mile

[n_dawg]

Wow, what a wealth of information. Thanks gartgid.

44 psi seems pretty low for the max sidewall. I wonder what the Aptera recommendations will be for the inflation pressure…

[SpyderMike]

given temperature increase I bet 34 psi cold.

[dcmeserve]

Why not "Real-Time Traction Adjustment" (RTTA, to coin the term)? I can think of a dozen different implementations. All of them are based around sensors that detect wheel slippage. Here's one implementation: each tire has multiple inner tubes with varying degrees of inflation. ...
I like this idea, though that example still sounds complicated.

Rather than pumping up some special set of innertubes, what about just letting some air out of a regular tire?

Normally, a car tire has no innertube; it's just the once piece, sealed tightly to the rim. If the rim had a large-diameter nozzle built in, then it's possible that a traction-control system could open it to let out maybe 5-10 psi or so pretty quickly, thereby increasing the tire's flexibility, and its grip. Once "slip conditions" are over, it could flip on a small pump to start gradually reinflating the tire through either that same nozzle or a second, smaller one, maybe taking a few minutes to restore the pressure.

Actually, didn't the original HumVee have something like this, albeit with manual control?

[garygid]

I wonder if there will be enough room for a flat tire to deform
as it is going flat and still not snag on the skirt's bottom edge?

[ApteraStorm]

I wonder if there will be enough room for a flat tire to deform
as it is going flat and still not snag on the skirt's bottom edge?

Speaking of that... will you be able to 'open a door' to check the tire pressure, or do you have to keep driving until the stem is visible to check the pressure?

Many cars (like the Prius) have a low tire pressure indicator, but it doesn't indicate until the pressure is much too low, so I wouldn't want to rely on that only.

[n_dawg]

Tire pressure sensors would be a great addition to the Aptera, though I have yet to find any mention of them. Even smarter, even more efficient!

[garygid]

The Accutire MS-4359B (http://www.autobarn.net/accutire-ms-4359b.html)Remote Tire Pressure Monitoring System
with 4 Electronic Valve Caps (a spare cap for the Aptera).
At this site, $50 + shipping, but $35 at Amazon.com
It is not really "Remote" monitoring. Apparently you have to
actually touch the hand-held unit to the sensor on the valve stem.
Also, mixed reviews at amazon.

The Hella TC400 (http://www.amazon.com/Pressure-Monitoring-Adjustable-Background-Display/dp/B000QSDZQC/ref=pd_sbs_auto_title_3)In Car Tire Pressure Monitoring System
With Adjustable Background Color Display ... is $224 at Amazon,
and the two reviews give it good marks. Also monitors Over-Temperature.
Also see them here (http://www.crutchfield.com/S-kbeyjdorWGi/App/Product/Item/Main.aspx?i=529TC400), for $279, where they say:
"Note: The remote sensors replace the valve stems in your vehicle's wheels.
Proper installation, tire replacement, and wheel balancing should
be performed by a professional mechanic."

Of course, there are other systems.

[daddio]

How do you get access/find the tire air valve for routine top off of air?
It doesn't seem the wheel/tire valve is visible beyond the tire covers?

Insight owners must have dealt with this.... but in their case it would be a little easier as it was only the back wheels and their skirts are higher

[garygid]

Yes, the Honda Insight rear skirt is a lot higher than the Aptera's skirts.

I think that no part of the vehicle can go below the rim of the wheel,
but that is about 4.4 inches for the Insight's Bridgestone tire that
the Aptera will most probably use.

However, that leaves no curb clearance, little "bump" clearance,
limited "hole" clearance, and ... unknown access for checking the
air pressure or for filling with air. Another surprise that we await.

[SEGsby]

Was just wondering this the other day:

How many people does it take to put air in an Aptera's tires? :aptera:

Seriously. What exactly would be involved in maintaining them, and getting the best range possible from the vehicle? The valve stems appear difficult to access...

Thanks,

[speculawyer]

How many people does it take to put air in an Aptera's tires? :aptera:

Seriously. What exactly would be involved in maintaining them, and getting the best range possible from the vehicle? The valve stems appear difficult to access...
1 person who has common sense.

The tires are the same tires that the original Honda Insight used. The various cowlings can be removed to access the tire for filling air & fixing flats.

[SEGsby]

Common sense tells me that tools would probably be required to remove the skirts? Anyone know for sure? How long would this process of removing the skirts, dealing with the tire, and then replacing the covers take?

[evolutionmovement]

Could be something like flush Dzus fasteners that you can remove with a quarter-turn from a coin.

[IamIan]

If anything like the Insight Skirts they can easily be removed in ~5 seconds, with a coin or screw driver.

[garygid]

The 2e might even have (an option for the) electronic
monitoring of tire air pressure.

[Matthijs]

This is from the FAQ:

Is there a spare tire? What happens when I get a flat?
We realize it is important to provide ease of service and repair and the vehicle is designed to accommodate the driver appropriately. Each vehicle is equipped with an emergency tire system.

[SEGsby]

You have to admit, "Emergency Tire System" is pretty vague. A lot of car makers would call that a Spare Tire, or doughnut. *shrugs* I have no idea what they mean by that statement.

But I notice that the Front Pants appear to have panel lines on the sides. That seems to indicate they come off there, to get to the tire. There are no visible places to use tools for this... I can imagine a latch you pull under the front or back (or both?) edges, to disengage the panel. But who knows?

http://www.aptera.com/look.php

And the back... That intrigues me a bit. The only "smaller" panel for user wheel access appears to be the darker shaded section that's pretty long and seems to be one piece. There does not look to be any seam in the back, so it's probably shaped like a fairly large "V" when it comes off.

Due to the shape, the rear tire would have to be unbolted and rolled back to remove it, assuming one could lift and stabilize the back of the car without damaging it. Standard mechanics lifts at Service Stations will probably not be useful for this operation?

I dunno. Owning one will certainly be an interesting experience.

[garygid]

The "Look" computer renderings do not include all the fasteners or
other fine detail. Remember, the steering wheel was "floating"
in one view (they fixed that after we made fun of it).
The Backup TV camera is still there in the rear-view drawing.

The "emergency tire kit" will probably include a can of something like
"Fix-a-Flat" and possibly a wheel jack mechanism and lug wrench.
Very unlikely to actually include a "spare" tire.

However, buying a spare rim and tire to keep ready-for-use in your
garage is very likely be an extra-cost option.

[efxjim]

Wonder what the jack looks like?

[garygid]

Perhaps a simple vertical bar with a bottom "foot" plate and a ratcheting
head that hooks under the bottom of the front steering knuckle?