Ryninger

So it is generally accepted that going with larger tires will negatively effect fuel economy.

If a guy were to get a taller tire without getting a wider tire and he is running with 3.73's, say a 32" x 11" tire to a 34" x 11" tire, Is it out of line to expect an increase in economy? Since it would essentially be lowering his gear ratio. Would the contact patch be that much larger to negate this effect? For conversation sake lets say it is the same tire model just going taller...

givecjadollar

^^ Good question. I'd like to know this as well.

FloridaSnowman

negative, its a greater rotating circumfrence. it will require more effort to roll a 34 than a 31, width is the contact patch, like a foot print, it too slows you down but not as much as much as diameter. Atop the taller tire you now have an increase in vertical profile. You now have effectively become less aerodynamic. and created more drag. gears help, but it doesnt help your energy efficiency quotient

pcphorse118

I cant argue this. It makes sense and I dont have the energy to think if I could disprove this. The only question I have with this thinking is this:
How come when I ride my bikes, the ones with bigger tires seem to use less effort to move?

Obiously I am not thinking in terms of gears and bearings, Its just a general question.

FloridaSnowman

most smaller diameter wheels ie: BMX bicycles have 20" wheels, fixed gear bikes are usually made from stronger materials for more durable resistance to impacts of a failed stunt.
moutain/road bicycle have 24-28" wheels, and have any number of gear combinations. and are made of lighter materials for better energy efficiency on longer rides

pcphorse118

So if I had 2 fixed gear bikes with different wheels sizes, the smaller would then be more efficient. Thanks like I said just pondering.

schissler

that depends on what time of riding you were doing.

11screw50

well, I once had a 4 cyl. nissan (97) with 4.56's (I think, its been a while) and when I went from stock 235/75r15's (~29" tall) to 31x10.50's AT's, I actually did gain 2mpg on average. so it *can* happen but I wouldnt expect it.

Rsnake460

It is my understanding that a taller tire will raise the ratio of engine revolution to tire revolution. When in high gear, you are 1 to 1. (unless you have overdrive). So a taller tire takes a little longer to make 1 revolution to 1 engine rev. Result: higher gear ratio overall. ...Right? lol

bradseabridge

Yes that's correct. If you are doing mainly highway you may see a mpg boost because once you have the tire up to speed it's easy to keep it there which is why there may be a MPG boost. It's the stop and go and slowing down and picking up which is what kills the MPG.