My daughter did a science project at school (she’s in the 5th grade). They sent home a sheet with ideas on what to do and strict rules about no stored chemical energy release experiments (I was thinking world record distance potato gun shot). One of the ideas was to measure the change in bounce of a ball at different air pressures, so why not record the change in mpg with changing tire pressures. My daughter figured if she involved Daddy’s new toy Insight she would get more help with the whole thing.
We ended up testing 3 cars at 3 tire pressures, one week for each pressure. The cars where a ’97 Civic HX (I put 250k on this one, now my wife drives it), ’04 Accord (this is my Mom’s car, Mom & Dad are retired now so the usage on this car is sporadic) and the ’06 Insight (I put 100 miles a day on this commuting). Hm, there seams to be a trend here. I showed my daughter the max tire pressure on the tire side wall and the manufactures recommended pressure in the door jamb. She set the pressure to 45 psi to start, we reduced it to 35 then 25 psi and recorded the miles traveled and gas used. She calculated the mpg and wrote up a report.
The Insight got:
60.75mpg @ 45psi
55.10mpg @ 35psi
54.97mpg @ 25psi
All three cars showed a similar trend in that there was a large improvement from 35 to 45 psi. I believe that this dose not reflect the true rolling resistance character of the tires as we had 2 days of rain during the 35 psi week also auto design text books suggest that a graph of the tire rolling resistance should be close to saturated at the max recommended pressure (meaning that the graph will be leveled off). My daughters’ data suggested that more pressure will continue to bring significant gains. I don’t think her project was ‘wrong’ as she reported the data she collected and it was the best data she could generate with the resources available.
Over all I was thrilled with her science project. Most of the kids did ‘watering plants with different liquids’ (Mt Dew was better than water from a water softener) and what brand of pop corn pops best (Pop Secret followed by Act 2). But then my opinion is probably a little biased.
We ended up testing 3 cars at 3 tire pressures, one week for each pressure. The cars where a ’97 Civic HX (I put 250k on this one, now my wife drives it), ’04 Accord (this is my Mom’s car, Mom & Dad are retired now so the usage on this car is sporadic) and the ’06 Insight (I put 100 miles a day on this commuting). Hm, there seams to be a trend here. I showed my daughter the max tire pressure on the tire side wall and the manufactures recommended pressure in the door jamb. She set the pressure to 45 psi to start, we reduced it to 35 then 25 psi and recorded the miles traveled and gas used. She calculated the mpg and wrote up a report.
The Insight got:
60.75mpg @ 45psi
55.10mpg @ 35psi
54.97mpg @ 25psi
All three cars showed a similar trend in that there was a large improvement from 35 to 45 psi. I believe that this dose not reflect the true rolling resistance character of the tires as we had 2 days of rain during the 35 psi week also auto design text books suggest that a graph of the tire rolling resistance should be close to saturated at the max recommended pressure (meaning that the graph will be leveled off). My daughters’ data suggested that more pressure will continue to bring significant gains. I don’t think her project was ‘wrong’ as she reported the data she collected and it was the best data she could generate with the resources available.
Over all I was thrilled with her science project. Most of the kids did ‘watering plants with different liquids’ (Mt Dew was better than water from a water softener) and what brand of pop corn pops best (Pop Secret followed by Act 2). But then my opinion is probably a little biased.
