December 16, 2011

Where plus-sizing is super-sexy

Some men like them super-sized. And we're not talking about women, or any part belonging to women. We're talking about the rims of car wheels. Car wheels? Why yes: for many cars, plus-sized wheels are a rather expensive option that has mystified CelloMom for some time now. Why are wheels with wider rims worth a premium up to $5000?

In case you are completely confused: Plus-sizing refers to the option of buying wheels for your car with larger-diameter rims. For instance, if the "standard" package has wheels with 16" diameter rims, the option with 17" rims is called Plus-1, that with 18" rims is called Plus-2, and so on. The picture below shows five out of 14 choices offered for the Audi A6 Saloon (Europe-speak for Sedan), culled from the German price list. Way on the left is the standard wheel with 16" rims, the next one is Plus-1, then Plus-2 and Plus-3, and finally on the far right is the Plus-4 tire with 20" rims. Don't ask why a German carmaker like Audi measures its wheel rims in inches, that one is way beyond Cellomom.

You can change the size of the tire rim, but you must keep the overall wheel diameter unchanged, or your speed indicator and mileage counter will be inaccurate. So as you go from a 16" rim to a 20" rim, the tires' sidewall gets smaller by 2"; you can see this trend clearly in the picture above. At the same time, the wheels get wider in the lateral direction (left-right direction of the car). Typically the recommended pressure is a few psi higher for Plus-1 tires.

So that's the what. But why? CelloMom finds that the benefits of plus-sizing falls in two categories: performance and aesthetics.


Performance, the Pros
"Performance" in this context means better handling. That's code for being able to zip around corners better and faster (on dry roads anyway), and to reach higher maximum speeds.

Response time:
Because plus-sized tires have a smaller sidewall, the tire distortion that happens when you go around a corner is reduced, and you can change direction that much faster.

Better traction (on dry roads):
The weight of the car makes the tires sag a little. With smaller sidewalls and higher pressure this distortion is reduced, so the contact patch, where the tire touches the road, is shorter in the tangential direction, or the front-back direction of the car. But the tire is also wider, so the contact patch is wider laterally. Because that is not the rolling direction, this gives better protection against skidding. With a plus-sized tire, instead of starting to skid at 0.83g, you keep frictional road contact until 0.88g (from a Car&Driver test).
Zow. At these accelerations, without seat belts the passengers would be banking the corner sitting at nearly 45 degrees from the usual vertical. Eggs and cellos can be written off.

Higher maximum speed:
Some physics connected with the shorter and wider contact patch (which CelloMom doesn't understand) allows plus-sized wheels to reach higher maximum safe speeds. We're talking an improvement from 150mph to 170mph. Since both these speeds are more than twice the US highway speed limit, CelloMom can't be bothered to dig up the relevant physics.


Performance, the Cons
These performance improvements come at a price. Here is the other side of the argument:

Fuel economy suffers
Plus-sized wheels are heavier than standard ones. In the Car&Driver test going to Plus-4 resulted in a 10% decrease of fuel efficiency.

Bumpy ride
Because the tires' sidewalls are smaller, and because the pressure is higher, plus-sized tires don't absorb any unevenness in the road surface, so you'll feel connected to the road in more ways than one. The shock absorbers in the suspension system are optimised for a lower frequency range, so they won't help much on gravel, unpaved roads and other conditions which are unknown on race courses.

Worse traction in snow and water
Plus-sized tires are wider, so squeezing surface water away through the treads is harder. The result is that it's much easier to start hydroplaning in rainy conditions. And because the contact patch is shorter in the direction of travel, and also because of the higher tire pressure, traction is worse in snowy and icy conditions.

Wheel damage
You know what they say about wheels: when you bend it you can't mend it. A reduced side wall on a tire makes the tire more prone to rupture, and is the shortest way to a damaged rim. In the 2010's US, roads are not only not smooth, they are downright dangerous to the well-being of wheel rims. Never mind the broken glass and the rusty nails: CelloMoms town sports potholes large enough to do the cooking for half a village. And while potholes are merely deep, what's arguably even more dangerous are manholes which have inexplicably sunk into the asphalt, making nice paella pans. Some of those are deep enough to feed half the village also, and sport nice sharp and well-defined edges that will cheerfully put an end to the circularity of your wheel.

Which brings us to the funds required to acquire (or replace) the wheels. For the Audi A6 example, the 16" wheels come standard. Getting successively larger wheels gets more expensive. The most expensive 20" wheel is a €3650 option ($4700 at today's exchange rate).



Okay. That was function; how about looks? CelloMom did a small and non-scientific survey among her friends, who were all mystified as to why larger wheel rims are considered more attractive. So, maybe that just means that we are not in the tribe of car enthousiasts. CelloMom asked around at various dealerships, figuring the people who sell those expensive options might have a clearer idea. But the best she got from this (also small) survey is this statement from one dealer, delivered firmly: "The car enthousiast (such as myself) prefers the look of a smaller sidewall." The Car&Driver article on plus-sizing starts by stating, "The aesthetic appeal of larger wheels and tires is undeniable". That didn't help CelloMom at all.

But cruising around the car world, eventually you run into cars that someone like CelloMom would not ordinarily drive. Check out this Ferrari: in this incarnation you can barely even see the tires, because the rims themselves practically fill the wheel well.

A light went on in CelloMom's head: "aesthetics" just means making your car look more like a Ferrari. Even if you never approach 170mph, even if you never take corners at close to 1g centrifugal force, the idea that you look like a Ferrari at all times is still worth a lot - up to $5000, in fact.

One good reason to have a large wheel rim in a race car, besides the improved road-tire interaction, is the dissipation of heat. At high speeds and large accelerations (including deceleration), wheels heat up from the road contact, and braking produces a lot more heat than in ordinary road conditions. CelloMom is not into watching car races, but heard that in some night-time races you can see the wheels glow from the heat generated by the brakes. So you want to design your wheels with a central area that is as large and as open as possible, perhaps also fiddling with the spoke design to whisk away all that heat.

You will notice that, for the sequence of Audi A6 tires, as you go from 16" to 20" the wheels become more open. For the 19" wheels (see picture below) you can look right in, reminding CelloMom of a cathedral window: open, beautiful, and very delicate.

Audi A6, 19" wheel. Rose window in San Vigilio, Trento, Italy

Call CelloMom a nerd. (She won't deny it.) When it comes to cars, she is overwhelmingly more sensitive to actual function than to looks or ideas. She never lives in the conditions where the improved performance of plus-sized wheels would make a difference. She's more than happy to drive in a vehicle with the regular set of tires: More rubber between the rims and the road means more protection from things like rattling teeth, dented rims, ice-skating cars, and the depletion of the purse. We'll take it.

December 14, 2011

Preview: Volvo V60 Plug-in Hybrid

CelloMom can forget about a test drive in this one: There are just a handful of them for sale in 2012. Volvo plans to make 1000 of them for 2013, and 5000 in 2014 (!) of which 30% will remain in Sweden, and the rest doled out to other European countries. But the specs on this baby are enough to make you want to buy a ticket to Stockholm. Certainly enough to make your green-leaning heart beat wildly with desire.

Developed by Volvo and the Swedish energy provider Vattenfal, this is a hybrid with a twist: The five-cylinder 2.4L turbodiesel engine drives the front wheels at 215HP. The 70HP electric engine lives in the back: to be precise, between the rear wheels which it drives. Logical, no? The drawback is that the battery takes up the space where formerly the spare tire used to live. Check out the autoblog.nl gallery for nice cut-out images of the engine placement, as well as other photos, e.g. for the truly distracted among us, the dashboard backlight goes from blue to green to red as your fuel is depleted (no knowledge of Dutch required: these are pictures).

There are three buttons on the dashboard for choosing your driving mode: In the "Power" mode the turbodiesel engine gives that kick (from 0-100kph in 6.9 seconds, if you're into that kind of thing). One would have to be careful when carrying the cello, or eggs. In the "Pure" mode the electric engine does all the work (all 70HP of it); its range is up to 50km (30miles); charging it on a 230V outlet takes 7.5 hours at 6 Amps, or 3 hours at 16 Amps.

The "Hybrid" mode is the intermediate mode that gives the high fuel efficiency. CelloMom hopes you will not be taken in by the 124mpg number, since European fuel efficiency tests are wildly optimistic especially for the most frugal cars. For instance (see table below), the most frugal non-hybrid version of the V60 (which is also unavailable in the US) is the DRIVe with its 1.6L turbodiesel engine and a fuel economy quoted as 52mpg. In real life, as reported by real drivers, this model gets 39mpg, really not bad for a car of this size and weight.

Remembering that official European fuel economy numbers can be off by up to 40%, CelloMom's guess for the Volvo V60 plug-in hybrid is that its real fuel use will be in the 65-80mpg range.

Is 80mpg for the hybrid versus 39mpg for the turbodiesel enough to justify the price difference? Well- no. At European gas price levels, which have been around $10/gal (give or take a few bucks) you would be saving about $18,000 if your drive the car for 150,000 miles. That only accounts for half the price difference. At least another €4,000 (US$ 5,200) is because the "Kinetic" trim quoted in the table is the least expensive option, whereas the "Pure Limited" trim is bound to have all the bells and whistles, and then some. After all, this is a "Limited" edition, aimed at business use. The rest of the price difference can probably be chalked up to the novelty coefficient.

CelloMom, who is not an early adapter, prefers to wait until the kinks have been ironed out, and the price has come down once the widget has been made available to the masses. You can passively hope that this car will eventually make its way to American shores, or you can start talking to your Volvo dealer now to let them know that you want this baby!


Volvo V60 Estate, Turbo-Diesel vs. Plug-in Hybrid

TurboDiesel Plug-in Hybrid
Type DRIVe "Kinetic" "Pure Limited"
Year 2012 2012-2013
Emissions rating EURO5 "A"  
MSRP € 36,695 ($49,150) € 64,695 ($84,100)
CelloMom Rating *
Fuel Economy:
City/Hwy quoted 5.2 / 4.1 L/100km  
Avg. quoted 4.5L/100km (52mpg) 1.9L/100km (124mpg)
Avg. actual 39 mpg (Honest John) EST. 65-80 mpg

1.6L 4-cyl. turbo

2.4L 5-cyl. turbo
Power 115HP @ 3600rpm 215 HP (diesel)
70 HP (electric)
Gears 6-spd man 6-spd auto
Fuel Diesel Diesel
Length, mm(in) 4628mm (182.2in)  
Width, mm(in) 1865mm (73.4in)  
Height, mm(in) 1484mm (58.4)  
Weight, kg(lbs) 1537 kg (3389 lbs)  
Trunk volume, liters(cuft) 430 L (15.2 cuft)  
Turning radius, m(ft) 11.5m (37.7ft)  
Top speed, kph(mph) 190 kph (118mph)  

December 9, 2011

Can you do without the - now optional - spare tire?

Personally, CelloMom could do without the spare tire. But what about one for a new car? Very, very quietly, carmakers have stopped including a spare tire in their new vehicles. After all, taking things away can't be done with the same fanfare as when adding new features. Can you just see the ad? Cue deep male voice: "The NEW and IMPROVED Jeep Wrangler, now WITHOUT spare tire: because we want YOU to enjoy the extra 0.05 mpg!"

Most modern cars do get increased fuel efficiency when their rears are as smooth as possible - which is why they had the spare in the trunk.

Taking the spare out of the trunk decreases the total weight of the car by about 25lbs, or less than 1 percent of the total curb weight, from around 2500lbs for a small car like the Fiat 500, to over 4000lbs for a minivan. Don't buy the carmakers' tearful argument that they were driven to remove the spare tire by the harsh requirements of the new fuel efficiency standards: that argument doesn't wash.

What are your options? You can settle for the inflator kit that is offered for free. You can buy the optional "donut", a nearly-roadworthy torus that allows your car to limp to the nearest garage. You can buy a full-size spare tire, for up to $300. You can, on some models, opt for a set of "run-flat" tires, which can get you to the next garage even when completely flat, without damage to the rims. Those cost quite a bit more than $300.

There's the real argument: it's a cost-cutting measure. They make you pay $300 for something that they used to throw in standard and for free. And then they have the chutzpah to crow that there is suddenly SO much extra space in the trunk.

CelloMom will always opt for the full-sized spare. The roads and streets around where CelloMom lives are just not cleaned often enough or well enough. CelloMom is blessed with a flat tire about once a year, usually on some quiet road where it's nice that you can get yourself back on the road. CelloPlayer is getting pretty good at those tire bolts. If it ever happens on a highway it would be better to call AAA for help: it's just too dangerous to be messing around when just a few feet away traffic goes by at 65mph.

CelloMom found out about this spare tire issue when helping her dad buy a new car, over the summer in Holland, where he lives. He was offered, and refused, the option of the full-size spare. CelloMom was amazed. Here was a guy who is seriously into backup (that, anyway, is his excuse for owning three rather complete sets of tools). On one trip he brought a spare cylinder head; he put up with the teasing, until the spare ended up saving the trip. On certain road trips, like those in Indonesia, he is not happy until he gets at least two cars to go. With a spare tire in each car. And here he is saying no to a spare tire for his new car?

"You're just too stingy to cough up the 200 Euro", CelloMom said. We like to tell each other the truth. He turned around, and said,

"I haven't had a flat in forty years."

Whoa. CelloMom's dad loves his car. He regards it as an extension of himself. He digs the whole motel deal, where you can sleep right next to your car, but camping is better, because you can sleep in your car. He goes nowhere without that car, even though he lives in a country with excellent public transport and even better bike paths. He logs the miles. Okay, so Holland is a small place: but that's not where he rakes up the miles. Until CelloMom's mom passed away, they used to be on the road, all over Europe, for a minimum of five weeks a year. In a camper, mostly. By far their biggest vacation expense was gasoline.

Forty years of car travel like that, and not one flat? Either he's improbably lucky, or the roads are just cleaner over there. Or both.

December 8, 2011

Keeping up the pressure

Since CelloMom has pledged to warm herself up in the mornings by moving rather than turning up the thermostat, the yard has started to look mighty tidy. The carport is next, but first it's the turn of the car itself, on which the tires are looking a bit soft.

See this widget?

It's a bike pump adapter; you can get it at your local bicycle store. CelloMom got hers at a Dutch market (veggies, flowers, bike parts; all you need really). It cost one Euro, which today is about $1.50, and tomorrow might be anything, depending on whether or not the Europeans manage to keep themselves together monetarily.

But we digress. The pump adapter, which usually lives in CelloMom's spare change purse, goes on the tire valve and makes it look like a bicycle tire valve. Out comes the bike pump, and in goes the air. When CelloMom was done it was suddenly no longer a crisp morning, but rather a mild day - very mild for December. Those tires really were soft; shouldn't have let it go this far.

For $1.50 (and a bike pump, which was already in the shed), you can save the $1 you need to feed the air pump at the gas station, plus $10, the daily cost of a gym membership, and a chunk of the heating bill for today. Now that's a win.

December 2, 2011

Bring back the light!

Check out this German jousting armour. This is Protection with a capital P! The plates are good and heavy. The helmet has slits for eye openings, to keep the knight's eyes from being gouged by the opponent's lance, as he is aiming to dislodge the crest from the helmet. If the opponent is wearing similar armour, his vision wasn't all that good, so aiming that lance is a tricky business.

Fast forward to the present: When buying cars, we check out the safety ratings, because in the case of an accident we need the frames of our cars to give protection to ourselves and to our children.

But times have changed. CelloMom can't remember the last time she saw a jousting knight thundering out of the woods and onto the two-lane roads in her town. Can you? -- So why are the windows by the back seat getting smaller by the year?

As an example, consider the Honda CR-V, one of those CUVs much favoured by women. One assumes that a decent fraction of those women are moms who use their CR-V for ferrying their children. In a 1998 CR-V children had a glorious view out of their window. As long as you were in a child seat, you could still see down to road level.

Those children would not be happy if their mom bought a 2011 CR-V to replace her old trusty one from 1998. Just as the kids have grown from tots to teens, the window area in the back row has shrunk - by quite a lot. The bottom of the window frame has been raised, and the top of the frame is lower. Not only that, the third window has shrunk to the size of an afterthought. Now that the children have grown to who knows what heights, they would have no trouble looking down to the road surface, but they couldn't see the sky without some creative contortions on their necks, or else they have to do what you keep telling them not to do, which is to slouch way down on their seats.

Why would a car designer do this? Surely not to please the children in the back seat, but rather their parents, who after all are the ones who have to sign the financing papers. It has been suggested that when the bottom of the window frame follows a rising line towards the rear of the car, it makes the car look more sporty. Hmm. CelloMom could do without that one. CelloMom is all for her self being sportier than her car.

So the top of the window frame follows a downward sloping line, from the front to the rear of the car. If the roof were made to slope that way also, there is a very good aerodynamic reason for it, since the downward curve actually contributes to the fuel efficiency. Some models just end up looking like a large gorilla has been sitting on the rear end of the roof. On cars like the Toyota Prius or the Honda Insight, not only does the curved-down roof look pretty, the outline of the car resembles a leaf which pleases the green-leaning buyers.

But what to think of a car of which the windows follow the downward curve, while the roof stays reasonably flat? The Toyota Matrix is one of many examples. The overall assembly looks pretty enough. But then you get a nagging feeling that it's only appearing to be aerodynamically correct without actually being so. Reminds you of those politically correct university science departments whose websites trumpet their women-friendliness but whose sole female faculty member can be found in a lab in the basement.

At last, in 2012 the Matrix has a roof that actually curves down, so that the line of the roof follows the line of the windows. But the children on that back seat had better not grow to basketball players. Besides, they've taken away the third window altogether, so sitting in the back now feels like occupying a cave. Because the bottom line of the window frame is still tilted up.

But - the whole point of a car ride is to look at the world outside. Even on the daily ride to school, somehow there is something interesting to see every day.

Children in the back of a 2012 Matrix can still try to peer through the front side windows, which have remained relatively high. The same cannot be said of the side windows of the new Range Rover Evoque, which are small front and back. It is not entirely clear what this car is supposed to evoke; to CelloMom it only brings to mind the image of two gorillas dallying on the Rover's roof all night, leaving at daylight completely satisfied - in the knowledge that they have ruined a perfectly good car. The Evoque resembles nothing so much as that medieval helmet with the slits. What are its owners so afraid of?