Why are modern cars wearing such thick shoes?

RevRico wrote: I always thought it was to sell more expensive tires. Why sell someone 16s that would be perfectly capable when you can charge triple for 20"plus?

oddly, that's what I thought when we were shopping for SUVs for the wife recently. We ended up getting a CX-9 with the 20" wheels (got a better deal on the Grand Touring than the Touring we were really looking for), and I was a bit bitter about how much tires would cost.

But then I looked it up...the 20" sizes for that tire vs. the 18" sizes for the touring model....difference was like $10 or 20 per tire max depending on model. We put a full new set (including spare) on the CX-9 of the highest-rated tire in that size on Tire Rack for under $1k shipped and mounted. I paid that much or more for the 17" UHP tires on my WRX.....

Point being, not sure that "larger tires are way more expensive" argument holds water when it comes to regular street vehicles - though the big high-performance tires are pretty damn expensive.

Clearly fashion drives the larger diameter wheels despite the fact that performance deteriorates with higher unsprung weight, as does ride comfort with less rubber between you and the road.

The other thing it does is spur the purchase of 'big brake' kits because the perfectly safe stock brakes tend to look small within the giant wheels and people want a better look and then justify it with 'safety' as a reason.

It is an interesting question as to what diameter wheel represents the sweet spot for handling and comfort. I'd be inclined to thinks something in the 16" - 17" region, obviously with wider rims than on traditionally shod cars to accommodate wider rubber.

I own two modern sports cars - one has 245x45 - 18 and the other (on the rear) has 255x40 - 18. Owners of those cars frequently try and fit even wider tires under them, but the adhesion limits of decent performance tires in stock size don't warrant that unless you race that cars. IMHO.

irish44j wrote:

RevRico wrote: I always thought it was to sell more expensive tires. Why sell someone 16s that would be perfectly capable when you can charge triple for 20"plus?

oddly, that's what I thought when we were shopping for SUVs for the wife recently. We ended up getting a CX-9 with the 20" wheels (got a better deal on the Grand Touring than the Touring we were really looking for), and I was a bit bitter about how much tires would cost. But then I looked it up...the 20" sizes for that tire vs. the 18" sizes for the touring model....difference was like $10 or 20 per tire max depending on model. We put a full new set (including spare) on the CX-9 of the highest-rated tire in that size on Tire Rack for under $1k shipped and mounted. I paid that much or more for the 17" UHP tires on my WRX..... Point being, not sure that "larger tires are way more expensive" argument holds water when it comes to regular street vehicles - though the big high-performance tires are pretty damn expensive.

The wheels are pretty expensive, too. Although it is interesting, German cars have swung the pendulum from peanut butter metal to wheels that crack before they bend. Usually the tire is fine but there's a slow leak from a crack extending to the bead area.

irish44j wrote: Point being, not sure that "larger tires are way more expensive" argument holds water when it comes to regular street vehicles - though the big high-performance tires are pretty damn expensive.

I just tried one random example. ZII in 225/45-17 is $40/corner cheaper than 225/40-18

I'm not a huge fan of the crazy large diameter wheels. 4" of sidewall seems about optimal to me (23"tire on a 15 or 25" on a 17). The 20" wheels on the new Civic Type R seem absurd to me.

Bigger wheels and tires are heavier = more unsprung weight = worse ride quality on same suspension. Larger wheels and tires lead to vehicle weight increases... whole big cascade effect needed just by increasing the unsprung mass.

No regular passenger vehicle really needs wheels larger than 16" or 17". On my FR-S I went from stock nearly 21lb 17x7 wheels and 20lb 215/45-17 tires to 17lb 17x7.5 wheels and 19lb 205/45-17 tires. Dropped over 4lbs a corner, greatly improved grip (dry and wet), improved acceleration/responsiveness, noticeably improved ride quality, and car is more planted due to CG drop from smaller diameter tire. Don't need wide tires, skinny tires work just fine at improving grip over stock - tire compound is what gives grip, tire width has little to do with it.

When I look for tires, first criteria is desired compound level and second is weight. Will not buy a heavier than stock wheel or tire... must be stock or less weight. And I really don't want anything much larger than needed to clear the brake rotors.

20" wheels on a Civic is rediculous... as is their current ~3000lb weight.

Bigger wheels are heavier. Tires for said bigger wheels aren't necessarily though. In some cases, they're actually lighter. Now if you make the tire bigger overall, then that's where the weight gain comes in.

Vracer111 wrote: as is their current ~3000lb weight.

Not all that ridiculous for their size. They're not particularly small cars anymore.

rslifkin wrote: Bigger wheels are heavier. Tires for said bigger wheels aren't necessarily though. In some cases, they're actually lighter. Now if you make the tire bigger overall, then that's where the weight gain comes in.

Vracer111 wrote: as is their current ~3000lb weight.

Not all that ridiculous for their size. They're not particularly small cars anymore.

Correct, they really should be called an Accord now... have a much bigger presence than my FR-S when I park by them. Thought they actually were the new Accord when first came out. The '91 Civic 4 door sedan I had briefly weighed ~2200lbs.

In my opinion, the proportions on a lot of tires today look wrong. They are wider, but a lot taller, making them look tall and skinny by perspective. Most new Camaros and Mustangs look off to me, like they really need wider tires just to look right. Ultra low profile tires looked cool back when you only saw them on race cars. Now that every SUV and Minivan has them as an option, they look fake to me. I prefer the look of a bit of sidewall. And huge rims look silly with tiny brakes.

Vracer111 wrote: Bigger wheels and tires are heavier = more unsprung weight = worse ride quality on same suspension.

Not necessarily. I went from 17s to 20s on my '06 Mustang GT and suffered no ride quality issues, and I went from 16s to 19s on my 740iL and also suffered no ride loss on these east coast roads. Both cars felt better on road than they did before, too. And both looked worlds better to me, as well.