Do bigger (=taller, more rolling diameter, not necessarily wider) tires promote a 'better' ride over road imperfection (potholes, dips, etc.)

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Mar 2, 2011
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All else being equal* will a bigger tire handle road imperfections better? The idea is that road imperfections will seem 'smaller.'

Imagine a giant tire going over a pothole mostly undisturbed but a smaller tire may well be swallowed up.

Practically speaking, your larger tire will most likely have more sidewall, be wider, it will likely also add more rotational unsprung weight and be further away from the axis which hurts braking and acceleration and be tougher on your suspension system to handle, you will be limited by the size of the wheel well. Practically speaking, you might get away with adding an inch or two of extra rolling diameter in your tires. Hypothetically speaking though, it seems like your bigger tire will handle road imperfections better, even assuming that the sidewall remains the same (because you're using a larger wheel) and the unsprung weight remains the same (because your larger wheels are made of carbon fiber, let's say...)

Thoughts?
 
According to the reports I've read and reviews of cars with both size tires, it seems to be the opposite. Most reviewers seem to say that the larger tires ride worse and give worse fuel economy. It may be due to the fact that the larger tires have smaller sidewalls, or maybe less flex, I don't know.
 
Taller as in higher aspect ratio are probably more likely to rely more on air volume to support the mass of the vehicle.

Lower profile tires and run flat tires are more likely to rely more of the structure of the tire to support the mass.

The tire relying more on air volume will absorb more of those imperfections compared to the one using the structure of the tire to support more of the mass.

But I'm neither a tire engineer, nor do I play one on TV and I did NOT stay at a Holiday Inn Express last night.
 
Almost universally, the taller the sidewall the better the ride. I experience this almost daily in using various cars in my fleet that have vastly different sidewall heights over the pitted roads in the Northeast. My first experiences with this happened nearly 20 years ago when i was test driving used Toyota Avalons back to back. At the time, large rims were 17“ wheels on many cars. At first I couldn’t figure out why multiple nearly identical Avalons rode and sounded so different. Finally figured out that the quiet/soft riding ones used 16” wheels, while the others were using 17” wheels. It made a very noticeable difference to be sure. Sure, there are cases where that is not so much the case, with the right suspension tuning and chassis tuning….but generally taller sidewall=more comfy ride.
 
There are a few different factors. A tire with more sidewall will ride better, generally. With that said, if the tire has a larger overall diameter it will impact your gear ratio, and will most likely be heavier. The larger diameter and increase in weight will impact handling, braking, and acceleration. This of course varies depending on the load range and weight compared to the tires being replaced.
 
There are a few different factors. A tire with more sidewall will ride better, generally. With that said, if the tire has a larger overall diameter it will impact your gear ratio, and will most likely be heavier. The larger diameter and increase in weight will impact handling, braking, and acceleration. This of course varies depending on the load range and weight compared to the tires being replaced.

No joke there! I just put on some 205/65-16 snow tires onto our sentra that takese 205/55-16. It does ride quite a bit nicer but the fuel economy had a pretty huge drop! I used to be able to get like 38-40 driving to work. It's been 27-31 this week!
 
It would seem logical that a larger outer diameter tire/wheel would roll over imperfections with less impact due to the greater arc length.

I remember back in the late 70's when Honda motorcycles put 23" front wheels on their dirt bikes (as opposed to the typical 21") precisely for the benefit of reducing jolts and impact.
 
No joke there! I just put on some 205/65-16 snow tires onto our sentra that takese 205/55-16. It does ride quite a bit nicer but the fuel economy had a pretty huge drop! I used to be able to get like 38-40 driving to work. It's been 27-31 this week!
Did you adjust your mileage calcs for the larger tire circumference?

With the Focus, I put on some 195/65R15 used Michelin defender (8/32) all seasons this summer from 195/60R15 goodyear Eagle-RSA's (4/32) and noticed better mileage without adjusting my calcs, a bit better ride too. The defenders are actually a bit lighter as well. Also my car is a manual and top gear is to low for good mileage, so dropping the rpms with larger diameter tires helps a bit. If your car is an automatic, it's probably geared for near maximum mileage with stock diameter tires and larger tires will cause more downshifting and may hurt mileage.

In the mountain bike world the change from 26" diameter tires to 29" tires is accepted to be much faster in rough terrain, and the 29" has less rolling resistance on smoother trails which helps keep momentum up which is a larger factor than the slightly better acceleration of a 26" wheel.
 
I didn't adjust the mileage calc for the larger tires, good point. I should be used to doing that from so many years of having to do it on the Jeep. But it has to cruise at a slightly higher RPM a lot of the time with the bigger tires on it. It's a CVT so it doesn't have to drop an entire gear and REALLY get a lot of revs. But it used to be like 2000 at 70 now it's 2200 at 70.

The Grand marquis is on larger tires as well - 225/60-16 to 215/70-16 but it still pulls in OD with the torque conveter locked up. Guess that's the advantage of having a V8
 
larger sidewall =
1. better traction in poor conditions
2. smoother ride
3. worse handling

larger diameter =
1. better traction
2. lower rolling resistance
3. slight ride improvement over cracks or depressions in roadway

ride quality on identical tires will be determined by sidewall more than diameter.
 
A tire with more sidewall will ride better, generally.

Not generally.

Yes, if you go from 225/45 R17 to 225/50 R16 (smaller rim size, more sidewall height, similar or same load index, same sort of tire) it'll surely ride smoother. However, if you go from 225/45 R17 to 235/45 R17 (same rim size, slightly more sidewall height, but higher load rating simultaneously, same sort of tire) it'll ride worse.

I did such 'tire width upgrades' several times. The increased LI you automatically get when going wider inevitably destroys any possible gain in ride. So if you really want to improve ride you also need a smaller rim diameter. I see this way too often overlooked.
That said, another important point is the type of tire. UHPs are commonly stiffer compared to touring tires. Different brands ride different. Enough stuff for a 20 page discussion.
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Night and day difference between 285/75/18 (11.25 x 35 on a 18x8" wheel) and 295/55/20 (11.6 x 33" on a 20x10" wheel) both inflated to 70 psi.
 
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