Just had to replace my second tire due to hitting a chuck hole. One on the freeway in San Diego and the recent one in a parking lot at low speed. Never happened before in over 50 years of driving. These 185-55-16 tires seem to be fragile! One was Bridgestone, the other Dunlop. 33psi/tire. Is this common? All 4 now carry road hazard from Sam's Club.
Thanks!
Jack H
2009 Sport

 

That does seem odd. But at highway speeds if you hit it dead on that is a lot of force. How hot was it? I'm sure the driving psi was higher than the resting psi.

 

I had to freaking google WTH was a "chuck hole."

Anyway, depending on the diameter of the hole, you can actually avoid damage by going FASTER (more horizontal speed allows you to "skip" over small enough holes). Of course, going super slow can avoid damage from ANY diameter hole (unless they're really deep, which can potentially damage other parts if they hit the ground). It has all to do with how you hit the far edge of the hole. Imagine you accidentally walking into a wall of a building. Hurts, right? Now, what would happen if you walked into the pointy corner? When you go fast enough on a smaller hole, the wheel doesn't have enough time to drop into the hole for angle needed for that edge to do damage (you'd basically glance of the edge).

Bigger holes would require you to go faster for the same effect (if you could actually go that fast), but it's usually easier just to slow down... or better yet, swerve around it.

Which is all the more reason to keep longer distances between you and the guy in front of you (so you can see the crap on the ground).

I lost one Dunlop tire going about 25-30 mph on a turn (curve, not actual turn) when I hit a hole in the road.

 

I'm skeptical on that. If we were just talking about a tire rolling on its own, maybe. But as part of a suspension, its got a spring pushing it down with a good bit of force, 834lbs of force plus the force of gravity on the tire. It should accelerate much faster than 9.8 m/s2. (Admittedly, this is a little exaggerated, as the shock dampen the acceleration, but it'll still be pretty fast initially.)

 

the question is... what is the impact angle of the wheel/tire onto the edge of the pothole?

There was a hole near a friend's place (it's been since patched)... when I drove moderately fast over it (30 mph), I felt it no different from a little road bump.

But on another occasion, when I was trying to "crawl" over it at about 10-15 mph, the impact was very jarring. My back actually hurt for a few seconds.

 

Again, I'd be shocked if the angle that the tire hits is different. That said, more though says that the two speeds could have two different weight transfers for the wheel. Less car weight on that corner means it can come up faster. That might explain it.

 

Put me down for one. You can add me on the stat sheet. Left front tire ended up with a sidewall blister after hitting a pothole a while back.

Probably could've chanced it and stretch the usage but decided just to go ahead and replace the blistered tire. I'm running stock Sports rims so I can only imagine those with +1's and +2's. Sure doesn't take much. There's a few bent rims on this forum too.

 

Also try to not hit the brakes when you notice a pothole. It's hard to stop the reaction but when hitting the brakes it shifts weight forward and puts tremendous load on the front tires. This in turn causes a blowout.

 

First one 70mph on I-8 in San Diego, created large bulge on side wall. Towed car over mountains to Yuma before noticed. Second in Grand Rapids at <10mph following several cars into parking lot, cut tire at rim. Flat when I came out from appointment. Never saw either hole. Thanks.
Jack H

 

i was in milwaukee for a friend's wedding. I was going 40mph in 115 degree heat, hit a pothole and blew a whole in the sidewall. The pos dunlop had 10k miles on it. i opted to upgrade my tire size to 205/50/R16.

 

Good point to make. Gravity really has little to do with it. The standard Fit spring rate is some 300 pounds per inch force and that will unwind your tire much faster than you can drive over that pothole at legal speeds. If the pothole is deep enough and you're driving 60 mph, 88 ft/sec, and the pothole is only 18" across, in the 0.17 seconds it takes to cross the pothole that tire will drop at least 2.9 feet. Not only is your forward speed punishing the tire the spring is really punishing the tire as it rams the tire into the edge of the pothole. Thed solution is either miss the pothole or buy truck tires.

PS for the inclined. force = mass times acceleration.
where the mass is w/g or say 60 lb for tire wheel and hub, and g=32.16 fps2
the force is 324 lb average; 800 lb at ride height, o at full extension.
ascceleration of the tire dowsnward is 173 fps2. In 0.17 seconds thats 2.95 feet. Yes, I know its generalized but it states the point: you can't really drive fast enough to keep the tire from impacting the top edge of the pothole and if its sharp enough the tire in gone, perhaps the wheel as well.
Few potholes are more than 6" deep so obviously the tire will strike the pothole edge hard enough to burst the tire and break or severely dent a wheel. THe only thing that 'saves' the tire is that it doesn't get in a hole so deep that the tirfe is flattened against the rim; in that cvase tire destruction is almost assured.

 

Lordy, 115 degrees in Milwaukee for Pete's sake. WTF is going on this summer? Spent some of July with the family in central Missouri and damn do those corn fields look sad.

 

Like. Prior to reading this I would have argued that in some cases you can indeed go faster. But now I think it's just a perceived lower impact.

BTW I think it's not the tires, it's the wheels. They're big so they leave less sidewall room. Ask any BMW owner with 19s ... Also my wife has a record of killing tires just in this way so I bought the wheel/tire protection. They may regret selling it to us!

 

his math leaves a lot out. The spring force works like a spring (duh) so the force exerted is directly proportional to the extension and has a high spring constant. The shock has a slowing "drag" effect proportional to either the vertical speed of the wheel or speed squared.

It's a differential equation to solve all that. Nasty enough that I'd need to pull out my dynamics book to solve it. Though to be fair, it's a pretty common equation.

All that said, I again think its about weight transfer and much more complex. If the wheel is at full extension and the rest of the car is unmoved, then the wheel can more easily come back up rather then deform on the edge. If the car has time to shift forward, then it's like hitting a bump. If the car has time to start shifting forward but not reach equilibrium, then the car has some downward energy pushing down on the wheel extra hard. Ie the wheel first has to push the car back up from falling some before it can start to go over the hump itself. Taking all that into account makes it hard to give a best answer.

 

Sounds dirty to me. Who is chuck, and why are we discussing his holes?


Anyways, here in Cleveland, we call them pot holes, and they will swallow your wheel. I've never had one ruin a tire like that. I have had them so bad that the front of my car scraped the ground tho. Another reason why I haven't lowered mine yet.

 

Replace chuck with pot

 

Don't forget inertia when it starts to fall.

 

Setting up the force equation takes that into account. To a large extent, newtons first law (the law of inertia) is really just a special case of the second law (F = ma). But within the assumption of an inertial reference frame, if you setup an F = ma equation, you're account for inertia.

 

Geez! Haven't read such a detailed analysis of potholes...

Leave it to a bunch of engineers to change a light bulb and the room will probably stay dark for a week... But with enough data to support why the room went dark and why the light bulb burned out... Cheers!

 

I ain't no dirty engineer. I'm a proper physicist.