I’m not putting this in Cafe Society, 'cos even though I saw it on Myth Busters, it’s not really about that show.
So, on a recent episode when trying to test the windows down vs. A/C debate, there were various comments akin to: it’s dangerous to run at 55mph on a race track; it’s exceptionally tiresome to run at 55mph on a race track; the experiment was done at 45 mph because the tires were at risk of exploding when running at 55mph.
So that the heck about a race track is so different than a regular road? Okay, the curves are banked – so what? Why’ll the tires blow? What’s going on here? I thought racetracks were designed to be safer and easier than public roads, hence the thrill of a grand prix.
I’ve spent some time on a racetrack, but only on motorcycles, never in a car.
That said, I’ve never heard anything like “the tires were at risk of exploding when running at 55mph.” What??? Unless there’s something really, really different about car tires, this strikes me as nonsense. Motorcycle tires are radial tires, just like car tires. Of course, the tire profile and rubber compounds are probably different, but still, the general idea is the same.
Slight variations in rubber compound and even tire pressure can make quite a difference in how a bike handles on the track, but the tires aren’t going to explode at 55 mph. Or 45. Or 155. Or whatever. Unless one is going so fast that one exceeds the speed rating of the tire, but then you’ll wipe out at the first turn anyway.
They were using SUVs, and pretty big ones at that (Ford Expedition?). My impression was that they were worried about a rollover accident if the tire blew.
I saw most of that episode, though I was doing some food work at the time and might have missed some details. It seemed like they missed several important steps needed to make the comparison accurate.
In my view from the kitchen, the vehicles appeared to be Ford Explorers. In the big flap over tires and Ford Explorers a while back, one of the factors was Ford’s spec for unusually low tire pressures (to make the ride softer.) Does the Exploder still specify that pressure? If so, that may have overtaxed their tires.
They didn’t say whether they used cruise control, but even if they did, the driving styles of these two crazy stuntmen could be quite different around that banked racetrack. They should have run two comparos, switching each car from A/C to open windows.
Did they use calibrated tanks? Typical modern fuel tanks are baffled for expansion, and the amount of fuel at “full” can vary by as much as two gallons in the same tank.
The driver in the A/C car griped about being cold. That made him look ill-informed. He could have dialed in some heat for comfort without affecting the operation of the A/C.
Overall, this was one of the lamest, most unscientific Mythbusters I have seen.
And one more thing - they should have had a third SUV running with AC off and windows closed, to truly measure the impact of drag.
This was the first one I’ve seen, and I’m not impressed. The way the dummy launch was set up almost guaranteed it would go straight down - it didn’t seem able to release until it was heading down. I missed the first part of the show, so maybe this was addressed then.
I didn’t see the show so I don’t know what track they were on but I do know that at Daytona raceway you “have” to be going “at least” 55 so you don’t slide down the embankment.
You don’t need special racing tires either as the pace cars for these races range from Pontiac Aztecs, Grand AMs, to just about any production car. And pace cars do about 55-60 on their pacing laps.
I could understand if they were using SUVs. Although the tires aren’t the problem. It’s the high center of gravity that’s the issue.
The races tracks I go to do not, under any circumstance, allow SUVs on the track. My Matrix is the tallest vehicle allowed (that I’ve seen) and I can take the track in excess of 80 mph (straight away) down to ~60 mph on the curves (and down to 20 mph on the hairpin).
My tires are road legal (and factory stock) Firestones.
Then you haven’t been watching the show for very long.
That’s not how it worked – they emptied the fuel tanks using a manual pump, then put exactly five gallons of gas in each tank. (I’m sure there was some residual fuel left over that bunged the experiment…)
It looked like they were using the 1/2-mile track at Altamont, and the corners were VERY flat…I’ll bet actual race cars have trouble with those corners at 55mph, let alone a top-heavy SUV! In any case, 45 vs. 55 makes a HUGE difference in wind resistance. They should have gone to So-Cal and rented the California Speedway (hey, it only gets used twice a year) and done tests at 55, 65 & 75 mph, which are the speeds normal drivers use.
(BTW, was I the only person waiting for the Hells Angels to show up and stab someone? No? I was? Ok…)
They pumped out “all” the gas and put 5 gallons in each car.
I agree though, it was very poorly designed test. Not only would the driving skills/properties be different, but there’s no guarantee the engines were tuned to perform identically. After one run they should have switched roles (i.e. turn the AC on in the other car) and run the test again. Also the lower speed (45mph) downplays the importance of air resistance.
By the way, is it possible that oval tracks harder on the tires because they are turning (and scrubbing) all the time? Seems to me it’d heat up the tires more severely than normal driving would.
They did a test with a scale model, and it was working a lot better. I think Buster was partially caught in the cage and didn’t release properly.
I have a trebuchet, and they are somewhat fiddly things to set up. On my very first fling, the projectile went backwards. I’m not at all surprised that their fling went so badly. Of course, in true Mythbusters style, it went catasrophically badly and they had only one chance at it. After the boom lift’s wheels broke off and the whole thing crashed into a heap, I was expecting some wag to holler out “Ready when you are, Cecil B!”
As for the MPG test- there were a lot of things they could have done better. Why didn’t they just DRAIN the tanks, rather than pump them out? Then run the cars to empty? Also, a sample size of one (one vehicle per tested variable) is just lousy. They should have repeated the test at least three more times - each driver would test each vehicle with each test method.
As far as the speed goes, when they were driving with the first test @ 55 MPH, the tires were squaling on the big ol’ Expedition. Since those SUV tires probably were not designed for continuous turning, they probably thought it would put too much stress on the sidewalls and increase the chance of a tire failure.
I personally don’t think there was any danger, but I think they had a “Better safe than sorry” attitude and decreased the second test to 45 MPH.
Their problem with the first test was that the computer they used measued airflow (probably by just plugging in to the OBD2 port and gathering metrics for mass air flow sensor). It did not measure true fuel consumption.
The problem with the second test has already been mentioned… two vehicles that can’t be gauranteed to be identical, no gaurantee the gas was pumped out to exactly the same level, etc.
I wondered why they just didn’t rig up something inline to the fuel line that just measured the gas volume passed through the gas line. It would have saved them a bunch of time, and they could have used the extra time to do the experiment 10 times and average the results.
As far as the boom experiment, my first though was “Hey, I want a free boom lift!”. I think after they proved it was not a likely myth, they just wanted an elaborate way to destroy the lift because it looks cool. I know I enjoyed watching the lift being destroyed. I think it would have thrown the dummy much farther if they would have welded a huge stop together to stop the boom arm at the optimal point for projecting the dummy.
Now we all know - want a piece of semi-exotic equipment on the cheap? Beat the bushes at the rental yards, looking for a used-up, broken-down machine. Of course, Mythbusters has a whole crew that scouts out stuff like that. Remember all those ping-pong balls from last week? They actually found someone that was willing to donate 600,000 balls.
Wait just a darned minute. So the danger was the “high” speed for the racetrack, and the race cars only go 65mph on the race track? What the heck kind of racing is done at this race track anyway, then? I start throwing a fit when traffic on the freeway gets under 65mph, and this is a race track?
I didn’t see that episode so I don’t know what kind of track they were on. I did much of my racing in classes requiring street legal tires. And we abused our tires far worse than they were designed. I don’t recall ever blowing a tire just from the force of the car going through a corner. And we used the cheapest wrecking yard tires we could find. The budget for that show is probably not very high and a producer probably didn’t want to take any risks.
The proper way to do the test would have been to put a fuel totalizer on the fuel line, then find a straight section of road somewhere and do speed runs in both directions to eliminate wind as a factor. Use the same vehicle. Something like this:
Run 1: Roll up windows, AC off. Five miles out, five miles back. 65 mph. Measure fuel flow.
Run 2: Roll down windows, AC off. Same distance. Measure fuel flow.
Run 3: Same as run 1, to correct for possible changes during the day (temperature, wind, etc).
Run 4: Windows up, AC On.
Run 5: Same as run 1
Run 6: Windows down, AC On.
Then repeat three times to get some reasonable data points. No need to rent a race track. Use the same vehicle for all runs. You should be able to get in 18 ten mile runs in a day of testing, considering downtime for adjustments, recording data, etc.
The thing about the Mythbusters is that these guys are pretty good backyard fabricators and tinkerers, and they are pretty creative at solving problems, but they are lousy scientists and they lack formal engineering knowledge. So sometimes they make real boneheaded errors. But they are honest in their limitations, and often correct their own mistakes in later shows. Some of their experiments are ingenious - I liked their quicksand making machine - clever design. And you’ve got to give them props for doing things like going into an old building and figuring out a way to work an old, rusted up elevator.
But best of all, they smash and blow up a lot of stuff. You can never go wrong smashing and blowing up a lot of stuff.
If the track was a high speed track, then they could be stressing the tires going around too slowly - the incline of a curve is set so that the force of the car going around the curve goes straight ‘down’ (perpendicular to the car) at a certain speed. Drive that track at a much lower speed, and you’re going to put stress on the sidewalls of the tires. I don’t know if that was the case here, since I haven’t seen the episode or the track.
