Hello Autopians. Welcome to another edition of Ask an Engineer. Let’s start off this week with a question from Pieter about why his car was only available with 20-inch wheels, then we’ll chat about whether crossovers are tougher than cars and about the AE86 Toyota’s handling.
Pieter lives in Belgium and he has got himself a very nice new Renault Grand Scenic as a company car. It’s not a car he would necessarily have chosen himself but a free car is a free car after all. His question relates to the tires, which are P195/55R20. Apparently the new Scenic comes only with this tire size regardless of trim level and he thought that was odd. He also wondered why his car might have been equipped with steel wheels instead of aluminum alloys and what difference that would have made.
Sticking With Your OEM Tires, Some Notes About Wheel Sizes
Well, Pieter, I too find the choice of 20” wheels across the board odd, but there could be a very good reason for this. I can’t look into the minds of the engineers and product planners at Renault but one reason to have a single tire size is that tire development is expensive and time consuming. If you can release a new vehicle with the same tire on all trim levels it saves a lot of time and money during development. A lot of effort is put into making sure the tires a car is sold with perform at the high levels a manufacturer specifies. This process can take over a year to complete and requires the tire manufacturer to make several “submissions” to the car company.
In each submission, the tire company will provide several hundred tires with different types of construction and rubber compounds. The constructions may vary in the way the steel and nylon belts are oriented, or what rubber compounds are used in the tread blocks. Each design will behave differently and the vehicle development engineers will then spend several weeks testing each of the tires to see which one works the best in the car. They will test each tire for cornering, stopping, and acceleration performance in dry and wet conditions. They will test the amount of noise a tire makes over various types of road surfaces. They will see how well the tire communicates road conditions through the steering system. Does the tire wander over minor road imperfections? Is it sensitive to ruts in the road? They may also test it on special machines to get an estimate of tire life.
Stick With OEM Rubber
All this can take several months to complete and it will usually happen about three times, with each successive submission refining the tire construction until hopefully by the third submission there is at least one construction that meets the targets set by the company for that particular vehicle. These targets, as well as many other vehicle targets, like cost, weight, fuel economy, vehicle size, etc. are set very early in a vehicle program to meet the expectations of the expected customer. The overall vehicle targets then get broken down into targets for each individual system, including the suspension and tires. Often the targets are based on vehicles made by the company’s competition, and also by doing a bit of guesswork on how the competition’s future products might improve — a process called “futuring.” You have to make some assumptions about how everyone else’s products are going to get better in the years it takes to bring a new car to market and make sure your product is as good or better than that. You don’t want to get into a situation where your new car is just as good as what your competition had four years earlier.
Once the engineers find a tire submission that meets (or even exceeds) the vehicle targets, that submission will be released for production. Since so much work has gone into choosing the right tire construction for a particular car, it is almost always advisable to replace your car’s tires with the same ones it came with. Round and black is not sufficient. All tires are absolutely NOT the same and choosing a non-OEM specified tire can have significant effects on the ride and handling of your car. It can also have a very strong effect on steering feel.
The tuning of the tire and the tuning of the steering system go hand-in-hand, as the rubber plays a big role in communicating the steering feel the manufacturer wants. That great steering feel and handling confidence your BMW 3 Series has can quickly disappear if you put some generic aftermarket tire on it. More importantly though, if the replacement tires don’t have the same amount of traction as the OEM tires, you could increase your stopping distances and hurt braking performance. Replace your car’s tires with the same brand and model it came with and you will likely be much happier in the long run.
Upselling
Now let’s get back to Pieter. The thing I find odd about the choice of a single tire size is that auto companies like to make money. Preferably lots of money. And one way to do this is to get your customers to buy extra things for their car. It’s called up-selling and one of the best up-selling items is wheels. Sell a base car with 18” dull wheels and your customers will spend thousands on optional 19” and 20” wheels because they just look better. If all your cars come with 20” wheels the look of the optional wheels is not nearly as different from the base wheels as it could be. Most manufacturers have calculated that the expense of the added tire development is more than offset by the profits from selling optional wheels and tires. Renault clearly felt differently in this case.
What Renault HAS done here is offer a steel wheel as base and have an optional aluminum alloy wheel. Steel wheels are cheap to make so they help keep the base vehicle cost down but they have significant aesthetic limitations. That’s why most steel wheels come with hubcaps that make them look like alloy wheels. Hubcaps can fall off though, and they can crack and discolor, ultimately tending to look like cheap versions of the real thing. Steelies are also less stiff than aluminum wheels, which is bad for handling — perhaps not an issue for a Renault Grand Scenic, but it might be for some other cars.
So there you have it, Pieter. Enjoy your new free Grand Scenic. As they say, “drive the wheels off it”! En tot ziens.
Crossover Versus Car: Which Is Tougher?
Andrew P. asked a question regarding the “rugged” look of many crossovers and if this actually represents additional capacity in terms of durability versus the regular cars many of them are based on. Well, Andrew, the answer is “it depends.” It depends on the manufacturer and on the vehicle. Some manufacturers do use different durability testing cycles for their crossovers and some don’t. At one of the OEMs I worked for, SUVs, especially the large ones, had a durability test that was a hybrid between cars and trucks. It meant they were tougher than cars but not as tough as trucks. In other cases, though, there was a recognition that the crossover would see no more than mall duty and there was no need to build in the extra weight and cost required to meet a higher durability standard. It really depended on who the target customers were.
Where these vehicles really benefit from a durability standpoint is with their tires. The first line of defense against potholes and other road impacts is the tire, and the larger the tire, the better it is at absorbing those impacts and at protecting the rest of the car. The part of the tire size that matters here is the sidewall height since this is the rubber that gets deformed when you hit a pothole or other bump in the road. It’s very easy to figure out how much sidewall you have by looking at the tire size numbers. Take the first number in the tire size and multiply by the second number and then divide by 100. For example, a P225/50R19 tire will have a sidewall height equal to 225 X 50 / 100 = 112.5 mm.
Now take the 2022 Toyota Camry, which comes with P215/55R17 tires in base trim. That tire has a sidewall of 215 x 55 / 100 = 118.25 mm. The same year Highlander has a base tire of P235/65R18 which has a sidewall height equal to 235 X 65 / 100 = 152.75 mm. That extra 34.5 mm represents a significant extra cushion that the Highlander has before the edge of that pothole hits the rim and does some serious damage. It means that the Highlander tire will protect the rest of the car much better than the Camry tire driving over the same road. That’s not to say that the Camry tire will do a poor job. 118 mm is still more than enough to protect the car on most roads. It just means that it will take a much bigger impact to damage the Highlander than the Camry.
Why Can The Toyota AE86 Out-Handle The Honda Accord?
Jonathan asked me a question about the AE86 Toyota which has what appears to have a very basic suspension setup — MacPherson strut front and live axle rear, while the same era Honda Accord had double wishbones. The AE86 is by many considered to be a much better handling car than the Honda and Jonathan wonders why that might be given the difference in technology between the cars.
Well, Jonathan, what you are seeing is there is more to car ride and handling than just suspension choice. The AE86 may have had a basic suspension but it was designed from the beginning as a rear wheel drive (RWD) car while the Honda was always meant to be front wheel drive (FWD). Designing a FWD car means you make vehicle level decisions that favor a front heavy car. The heavy engine and transmission are all in front with the majority of the engine ahead of the front wheels. Since the transmission ends up slightly behind the engine and the front wheels must be inline with the output of the transmission, they end up further rearward. That’s why FWD cars often have so much front overhang. All this means a weight distribution around 60% front, or worse. That does not favor a well handling car. The AE86 on the other hand could push the front wheels forward because they weren’t tied to the transmission. The weight of the engine would be placed further rearward and the transmission was behind that. All that meant that the AE86 only carried 53.5% of its weight in the front. That’s a big difference and will definitely be felt in the handling of the car regardless of how sophisticated the suspension is.
Well that’s it for this week. Please keep those questions coming to askanengineer@autopian.com and I’ll do my best to keep this discussion lively and informative.
Excellent article. Tyres have always been an important safety consideration for me and OEM isnt the panacea. The experience with my recent cars:
Honda Insight Mk1 – OEM Bridgestone B391. Became unavailable in the UK – so Michelin Energy Saver – not as good on fuel economy.
VW Phaeton – OEM Dunlop SP Sport 01. Poor traction and poor resistance to aquaplanning. Replaced with Goodyear F1 Asymmetric. Then went full winter tyre – Goodyear Ultragrip Performance which lasted 4 years.
VW Golf Clubsport S – OEM Michelin Pilot Sport Cups 2 Brilliant when warm, sticks like glue. Replaced with Pilot Sport 4S for winter/general all round use.
Renault Espace – I cant remember the OEM, but has been fitted with Continental Winter Contact TS830P for the last 8 years – the best tyre for cold and wet, bit squishy when warm.
When I bought my 2013 MINI new in December 2012 it came with runflat tires. Within the first month I had to replace one that caught a large nail and was “unrepairable” at either the dealer or a local tire place. About 12,000 miles later the runflats were showing excessive tread wear and had to be replaced. At about 48,000 miles now (I mostly drive this car locally and work from home) the replacement non-runflat Pirellis I bought are holding up just fine. I even bought a full size spare on a cheap steelie that I keep in the back of the car and have it rotated among the others on a regular basis. No problems at all.
Aside from the faster wear of the runflats, the ride of the car was also negatively affected. It’s so much better to drive.
I understand the whole concept of the OEM material tire supplied and the desire to replace tha; however, if one of the metric targets that the company has on the list is to provide shitty marshmallowy tires that I totally disagree. One of the greatest decisions I ever made was to replace the OEM tires on my 1g focus with a quality non shitty tire and it was smoother and quieter and better. After multiple sets gone through on our RAV I again confirmed the good non OEM was better.
Lesson here is that the OEM tire was picked to satisfy all engineered concepts. That is correct, but what’s not added is especially the budget desired by the bean counting engineers, and how fast the tire goes off and wears out is NOT their concern. It’s the buyers wear item as far as they care. So, get what you want, just don’t get cheapest shit, and don’t get the hardest long wear rated.
Counterpoint: Sometimes the OEM tires are hot garbage.
Example: Mazda CX-5, purchased used with 10,500 on the odo. The OEM tires (Geolandars) were down to 4/32 and noisy as fuck. The treadwear rating was 280. That’s not a typo. Replaced with Toyo Q/Ts which are much quieter (but a flyover by an F-4 would be quieter).
Nother example: Dodge Challenger, came with Michelin MXM4s which should have been good but weren’t. Downright unsafe in the rain and not much better dry. Also didn’t fit the rim very well. I’m convinced they re-labeled a 215- width tire as a 235, made it out of cast iron and molded the tread at half depth. After 30,000 miles they still had full tread, which was only 6/32 to begin with.
I don’t know this for a fact, but I’m convinced that tire manufacturers have “special” versions of their tires that they only sell to OEMs.
Yup yup.
Oem tires meet oem specs. Changing tires changes specs, but that may not be a bad thing if oem compromised based on target market (aka lowest cost) or used tires to make up for poor/archaic fuel economy choices further up the drive train (aka eco tires to make up for cutting cost on re-engineering the engine).
On top of that, oem tire choices represent what was possible to balance and forsee at the time of design (which is what, 4years before production). In a 10 year old car, should you see if there is a better balance based on tech change? I’d say yeah.
How about on my 27yr car originally sold with 195/55r15s? Should I buy 1995 tires or equivalent? Or could I do a lot better for less money buying something else? (spoiler, I went 235/45r17 and have experimented with a number of tires, summer tires are fun but not worth the wear and delicacy imo.)
All black donuts may not be the same, but you shouldn’t be wedded to 5, 15, 25, or 35yo engineering decisions which may actually have been marketing decisions.
For a new car? Sure, you probably can’t beat the couple mil they dropped 4 years ago. But you may also be willing to compromise as David says below, esp. When you can’t even sense the compromise.
I agree that cars are engineered for a specific tire, but in the article you mention it’s not necessarily the best tire, but the best tire for the budget and a range of compromises. You could theoretically buy a better tire than OEM that focuses on your priorities, because you’re not constrained to a budget and trying to meet competing benchmarks in economy, comfort, wear, handling, weather, noise, RFT, etc.
My BMW came with HORRIBLE Pirelli Cinturato run flats. I couldn’t wait to get rid of them for Michelin Pilot Sport AS4 that are better in every conceivable metric I care about. I don’t want RFT. I don’t care about economy. Handling and comfort were my top priorities and the Michelins deliver
My 2003 Miata came with terrible tires for a sporty car. They chose Bridgestone Turanza tires. They were just completely wrong. Those tires killed anything resembling steering feel. The handling was super squishy and unsettled. Why make a car that’s supposed to corner well and then put land barge tires on it? I was really happy when they wore out so I could get something more appropriate.
So I’m all in favor of getting tires that make sense for my priorities, not the priorities of the design team.
My question as a response to that is if the advice is to stick to OEM, what about winter tires? My 335xi came OEM with Bridgestone runflats which were fine, but about $100/each more than a non-OEM but still high-end brand name option. They were also summer tires, and BMW does not offer an OEM winter tire, so sticking to your advice I would be screwed. Sure don’t get an off-brand with a name like GreatBestMileStar but I swapped the Bridgestones with non-RFT Conti Extremecontact Sports and now to a higher traction Bridgestone “extreme performance summer” tire and improved both handling and tread life each time, why is that a bad thing (other than not having run-flats)?
So……
I shouldnt upgrade the tyres on my 2005 Toyota Echo/Yaris? with 175/55r14’s? I would think a good 15″ aluminium rim would be equal to or better than stock, as a 15″ was an option on the “upscale” Echo/Yaris. And I think a good all weather tyre would be a wise option too, no?
Thank you for your input Huibert! I didn’t know OEM’s put this much effort into tire selection. I Always guessed that the rubber installed on new cars was an economical choice. Most customers probable don’t even notice the tire brand and model when they buy a new car.
Like the majority here in the comments, I can’t fully agree with your sentiment that OEM rubber is always the way to go. I had some good experiences, like this Renault Grand Scenic which has Continental All Season Contact’s, a great tire and an excellent choice for the Belgian climate.
But I also had some real crappy rubber on brand new cars. A great example was my previous company car, a fully decked out Opel Astra.
Fun fact, David had a go behind the wheel of this car. Hi David! Congrats to you and your colleagues on this gem of a new website!!!
Back to the story: The car was delivered with horrible Bridgestone Turanza tires. They were ok in warm and dry weather, but the moment it started to get wet and/or cold, they lost all their affinity with the road surface. Granted these were summer tires, even so, you expect some grip to remain. I still have nightmares from the one time these tires met snow…
Anyways, I made sure they wore quickly and was real happy when the OEM Opel dealer replaced them with Continental Contact Sport’s. BTW, I did not ask them for this specific tire. They made that choice! I don’t know how it is in the states, but in Belgium I’m under the impression that most OEM dealers stick to one tire brand of choice. Which makes your argument of sticking with OEM rubber practically impossible for most people in this country.
Obviously it’s no AE86, but from a handling perspective the 3rd-gen Accord is no slouch. Those double-wishbones and the excellent speed-sensitive power steering make them a joy to drive. Small wonder it was the best-selling car in America for 1989.
Extra props for using the hatchback version in the image. An ’88 hatch like that got me all through college.
I work for GM and I will say that the Michelins they are putting on their cars now are absolute trash, horrible road noise, and need replaced by 30k miles I have seen this on over 250 cars from the last 3 model years I do not know what GM is doing with Michelin but they are not doing a good job, The Continental pro contacts they are using are fantastic. Seeing how these Michelins have been will keep me from ever buying a set of their tires.
I want to ask an engineer this thought. Why the hell does GM think they need to use plastic oil pans and plastic drain plugs on their turbo engines, an absolute joke and an absolute mess for our floors.
We would like to hear from a TESLA fan boy about their experience with the Huibert optionized OEM tire experience. But probably won’t. Maybe PNG here?
As the resident pedant, the title should include “car’s” between “your” and “tires”, otherwise the “it” in “it came with” has nothing to refer to.
“I am a big fan of Michelin and will always get their tires. ”
I am as well and have the same goal. My Accord came with Michelin Energy Savers as OEM and I loved them. They stayed very consistent throughout their 70k lifetime. The Accord is now on its third set and they are still awesome.
Unfortunately Michelin is not always an option. I have that issue with my Mazda so I’ve had to go with non-Michelins. My latest choice was Continental PureContacts. So far they have been at least on par with the Energy Savers and much better than the Goodyear Eagle GTs they replaced (Don’t get me started on the noisy Radar tires the car was wearing when I bought it, nor the Coopers that started great but got noisy and wore out within a couple of years).
If you find you can’t go with Michelins I suggest Continentals.
I was told by an Big 3 engineer a while back that the OEM tires have extra tough requirements such as a strict runout requirement that the tire manufacturer does not have to meet when they sell that same tire to the public so u may not get the same performance if u replace the OEM tires with the same ones.
The tires article is deeply misleading. I’m not here to say I know better than an OE engineer because I don’t. OE tires are—at best—a snapshot of what’s available at the time the vehicle was designed. Even assuming OE tires are the objective best (a questionable concept given the often incompatible design goals), they are unlikely to be the best 5 years later. Just because a certain tire was OE for a 2001 Porsche 996 absolutely does not mean that it is the best tire for the car *twenty years later*.
I think this whole argument can be solved with the addition of “if price is your primary concern” to this article. Because price is ABSOLUTELY a huge issue for the oem. And given a tire that checks the boxes and one that is clearly better but is $5 more, the check the boxes tire will be chosen 100% of the time.
As a consumer I want the best replacement tire for my car, and I’m shopping on performance first and price second. Because within about $25 per tire (in other words that’s the price difference I don’t worry about) or so the price is way less important than the performance characteristics that I care about.
Agree that replacing with OEM replacements makes sense for most people. I’ve tried buying the deal-of-the-day tires once and got burned badly. So I try to stick with bigger brand, identical size and hopefully same model. Look at consumer reports before moving to a different model. Always seems like replacements last much longer.
Wondering about airless though – when available, will they offer a significant improvement when replacing original tires? How about an article?
Rootwyrm, Cost is most definitely part of the compromise tire engineers have to make but it is not necessarily the dominant one. Keep in mind that tire manufacturers will make deals with OEM’s on price where they make very little if any profit on the hope that all those owners will buy their aftermarket tires a few years later. Aftermarket is where the money is!
Wow! The passion around this topic is fantastic! I love it! Though I certainly didn’t mean to start a fire storm.
Engineering is a game of compromises and tire development is no different. The compromises tire engineers have to deal with are numerous and the end result will never satisfy everybody. The idea is to satisfy the largest number of customers possible and offend as few as possible. This is true not just for tires but every other aspect of the car as well. Of course, the “customers” tire engineers have to satisfy include the finance department and while cost is not always the dominant factor for them to consider, it will always be there. cost must be taken into consideration otherwise a Civic would cost far too much and no one would buy it.
The balance tire engineers have to make also depends on the model and trim level. A base Mustang and a top off the line GT will have different targets and while cost might be the dominant factor on the base car, it may be much further down the list on the GT.
For those of you that replaced your tires and found aftermarket tires were significantly better, I say “good on you”. Go for it, but remember that you were probably replacing worn out tires with new rubber and those will always feel better. Also keep in mind that tire engineers need to consider all use cases, not just the normal ones you may encounter on your daily drives. Emergency handling in the wet may be something you never encounter, but it is something tire engineers most definitely take into consideration. That new tire you bought may be better then OEM in normal conditions but may fall on its face in extreme situations. If you’re lucky you will never have to find that out.
Keep those comments coming though. This is an awesome discussion and exactly what The Autopian is all about.
As the Autopian is a haven for ex-Jalops, it’s normal to see passion around tires! It’s the best cost/performance upgrade you can make!
The compromise I made was getting rid of my Goodyear run flat tires. They made the ride too stiff, and the steering feel horrible. I know I’m boned if I have a puncture as I have no spare, but it’s a risk I’m willing to take. Ever since I’ve been running Michelin PS4 my car’s better on track (understeer was a bitch) and the steering feel is better. The wear rate is great too: I’ve been torturing them for tree years on track! No idea about economy though, but it’s not my main concern.
My OEM runflats barely made it to 12,000 miles. And the ride quality was a nuisance. Like you I use non-runflats and I even carry a full size spare that I’ve never needed!
When concerns about ride comfort and tire noise are foremost in the equation, you can be that handling an grip slide down the slope a bit. As an enthusiast, I can live with more noise and less comfort to get a better tire. And no, worn out tires only degrade in tread grip functions. If you are arguing that the structure of the tire has broken down from usage, you are making a very shitty tire.
As I remember reading Michelin and Honda teamed up on the Ridgeline to make a specific version of the LTX. Loved mine and loved the tires.
On the other hand, I’ve seen several new cars come with different brand but same size tires. From what I’ve seen manufacturers will use whatever holds air unless you’re talking about a specific vehicle that requires a specific tire with specific capabilities. Tires are a minor hobby of mine. A little research will reveal different SKUs between OEM and aftermarket tires and between different aftermarket retailers so shopping closely will pay in the long run. By and large you get what you pay for.
If you’re shopping for an econobox you’re going to find X brand 205 70 15 tires. If you’re shopping for the latest 911 GT3 you will most likely find a specific brand with a specific SKU and woe be unto them who deviate from that. You may find yourself on the wrong side of a hedge.
On 95% of vehicles you’re better off going with the same or similar size tire in a Michelin or something comparable. Unless you have a steady source for Huangjin Goodround Tyres, don’t fret about changing brands too much.
Tires have evolved a great deal since I started driving 43 years ago, but I’m pretty sure that the main concern for auto manufacturers is still cost.
The last new car I bought was a 2010 Mustang, and the OEM tires lasted 25,000 miles. I looked into replacing them with the same model, even though I was dissatisfied with the wear. I discovered that the Goodrich tires it came with weren’t even offered for sale to the public, they were only sold to Ford. The closest model to OEM I could find was well over $100 a tire.
Needless to say, I opted to go with a less costly tire that still met the factory specs. They lasted 50,000 miles, as did the next set. Also, I didn’t notice any difference in handling other than the fact that the car rode better on new tires.
OEM KO2’s are miles ahead of the KO2’s your local shop will sell you and it shows.
OTOH, the OEM P Zeros that came on 2011-2017 Mustang’s with the Brembo/Performance packages are awful, awful tires and somehow managed to provide less grip in suboptimal weather than more aggressive 200TW tires while simultaneously proving inferior in warm weather to less aggressive 300TW tires.
I don’t think you can actually make a blanket statement on the superiority of OEM tires considering that for the vast majority of mass-market automobiles, cost to the OEM is a major deciding factor.
Huibert,
Maybe there is an answer out there for this situation… Was purchasing a 22 Atlas Cross Sport, dealer did not have what I wanted on the lot but could dealer trade for one very close- great, get it coming. EVERY Atlas and Atlas Cross Sport on their lot, their other two locations as well as photos on multiple dealers sites up to 2 states away (the trading dealer was within 200 miles but did not have “my” vehicle with actual photos) came with Pirelli Scorpion Zero AS (255/50/20) tires. Seriously every single one.
Now a week later mine arrives with Goodyear tires. I ask why no Pirellis but get no good answer. I actually mostly trust them as have had previous good experiences with them so I take delivery. They are OEM tires which in my experience are “eh” anyway and this is a second vehicle that won’t get a ton of miles anyway. But need the room and towing it offers.
So we get some light snow and sleet overnight and I spend most of my commute literally sliding all over. #@$%#&%#
Now I’m pissed, including at myself. Now the Pirelli tires may not have done any better, who knows? But I look both tires up on Discount Tire and find the Pirellis sell for $275 per while the Goodyear “Assurance Finesse” were at $105 per! These two tires are clearly not comparable yet both state they are OEM for my specific model and trim. As I seriously felt unsafe from the drive to work, I called my local shop whom I have worked with for years and traded them off that same day for a tire I have had very good experiences with on two prior SUVs. The dealer even took care of me to the tune of about 2/3 of what I paid for the switch as VW Customer Care did not in fact Care or have a good answer/explanation, although I did have to push a little. I have been back a few times for some minor issues and still every Atlas I see has Pirelli tires.
In the end I am happy but I don’t believe OEM spec tires are more than a cost compromise. And in this case truly just an absolute crap tire. As always, YMMV.
What happens when you have “basic” OEM tires (a base model) and want to replace them with something a bit better?
See tire testing on Tire Rack (which should be an advertiser on this site!)
In the need to compromise on tire development what the engineers pick is still only useful to a majority of owners across the country. Having great summer tires for the Texas summer is awesome. Just not if those same tires have to get through a Minnesota winter. Tire needs are as much about personal needs as they are location.