Optimal Tire Pressure

[JoePah]

Interesting articles and algorithm to determine your bike tires' optimal tube pressure. I've always pumped my tires to the same pressure, based on the maximum allowable shown on the tirewall, to minimize flats... not the most efficient choice, apparently.

For my Stromer Elite with 1.75" tires, and the COMBINED rider and bike weight of 230 lbs, and a front/rear weight distribution of 40%/60%, the tire pressure should be:

• Front: 28 psig
• Rear: 80 psig

Seems kind of extreme asymmetric pressures, but I will try a 40 psi/70 psig scheme... As another example, for a 2.25 inch tire, the pressure would be:

• Front: 17 psig
• Rear: 53 psig

If the rider and bike weight was 260 lbs and the same tires:

• Front: 20 psig
• Rear: 60 psig.

Don't exceed max allowable pressure provided by the tire manufacturer, of course. As temperatures change outside (and warm up) air can expand in your tires and cause a blowout.

The Science:
According to Frank Berto and Jan Heine (of Bicycle Quarterly magazine), two top bicycle science guys, the most efficient bicycle tire pressure is one that gives you a 15% drop in tire height when you get on the bike. “This tire has too little air!” It’s squishy and hard to turn. “This tire has too MUCH air!” It loses energy bouncing off small surface irregularities. “This tire is JUST RIGHT!” Fifteen percent is the Mama Bear of tire drop.

Given that you want each tire to ‘drop’ 15%, and bikes don’t weight the front as much as the rear, you don’ t want the same amount of air in each tire. It seems obvious when you think about it, but it was revelation to me. Here's a user friendly spreadsheet and the general article.

 

[Aushiker]

According to Frank Berto and Jan Heine (of Bicycle Quarterly magazine), two top bicycle science guys, the most efficient bicycle tire pressure is one that gives you a 15% drop in tire height when you get on the bike.

Thanks for sharing. Will bookmark for later reading. With respect to Jan Heine a lot of people might dispute the statement, "top bicycle science guys" He is known for his interesting take on matters bicycle and of course his promotion in his testing of his own brand of tyres or what he sells. Still that said, interesting reading for sure and adds thoughts to the mill.

Regards
Andrew

 

[Charly Banana]

Interesting, but too complicated. I tried reading both of your links, but gave up. I usually set the pressure somewhere near the middle of the min and max tire pressure values stamped on the tire. Perhaps it's not optimum, but unless you are racing bicycles does it really matter that much as long as it's within the min and max recommended values? I don't know.

The same type of discussion occurs on the motorcycle forums and after reading so many different opinions, I still don't know what the correct pressure is for my motorcycle tires.

 

[Vern]

I'd worry more about flats than "optimal" tire pressure. I have gotten two flats, both when my tire pressure was slightly low. I now always keep my tires, both front and back, at 70 which is between the recommended settings 60-80. It's hard as heck but offers very little rolling resistance and no flats.

 

[JoePah]

I'd worry more about flats than "optimal" tire pressure. I have gotten two flats, both when my tire pressure was slightly low. I now always keep my tires, both front and back, at 70 which is between the recommended settings 60-80. It's hard as heck but offers very little rolling resistance and no flats.

Vern, I share your concern and I have also tried to keep pressure on the high end.. My feelings are that reducing the front tire pressure might improve the handling, and I don't really worry about flats on the front tire... Also like the idea of increasing rear tire pressure.

 

[Vern]

Vern, I share your concern and I have also tried to keep pressure on the high end.. My feelings are that reducing the front tire pressure might improve the handling, and I don't really worry about flats on the front tire... Also like the idea of increasing rear tire pressure.

I get it. I'll try it sometime!

 

[JoePah]

Interesting, but too complicated. I tried reading both of your links, but gave up. I usually set the pressure somewhere near the middle of the min and max tire pressure values stamped on the tire. Perhaps it's not optimum, but unless you are racing bicycles does it really matter that much as long as it's within the min and max recommended values? I don't know.

The same type of discussion occurs on the motorcycle forums and after reading so many different opinions, I still don't know what the correct pressure is for my motorcycle tires.

Sorry it didn't work out for you... The spreadsheet can be a little touchy. If you change only one parameter at a time and let it recalculate it should work.

Or give me your parameters and I can provide the results...