A QUESTION FOR YOU MATH GUYS

pastor scott.com · May 19, 2005

I have a question to ponder ?

If I order a vehicle with 16in rims or 17in rims but the axel ratio is the same, does that not change the over all final drive ratio by not allot but by a little. Meaning its takes more power to turn the factor 17 then the factory 16. If so is then your truck a hair quicker off the line with a 16in then a 17in.

to think of it , take this example; take your factory 16in rim and replace it with a 14in wheel , what would be the results?? would not the engine RPMs be higher at 55 with a 14in rim then a 16in wheel ?

hey also try this. Any 04 burbs with 3.73 gears , whats your RPM at 55 with 16in wheels and anyone with the same but 17in rims and factory tires whats your RPM at 55?

just for fun

Scott

asepgrad98 · May 19, 2005

just for fun, if your tires are 10% smaller you will have about 10% higher rpms. Mind boggaling isnt it.

Shaners · May 19, 2005

The size of the rim makes no difference at all... It's the size of the tire that really matters!

mmmikkke · May 19, 2005

Yeah, the outside diameter of the tire is all that matters. The engine doesn't know or care where the "wheel" changes from metal to rubber.

Hotwire · May 19, 2005

everybody is dead on w/ the height of the tire reply, but a bigger wheel does have a little more rotating mass, therefore will take a little hp away. i don't know if going from 16-17 would make that big of a difference unless the weight of the rim was significantly different. Think that's why all the racing slick manufacturers are sticking w/ 15" rim sizes and not really venturing outside of that area.

I've known a lot of people that have went to 20" rims and complained about them slowing the vehicle down, which I'd assume was the rotating mass of all that metal.

there's a bunch of calculators on the web that help figure stuff like this out if you look.

USA1Fan · May 19, 2005

Which is also why it's recommended that you get better / bigger brakes when you move to 20's or bigger. Those big wheels' extra mass doesn't just reduce power (acceleration), they also make the brakes work harder to slow things back down. These trucks already have spongey feeling pedals (at least on my '04 with factory 17's), so I'd feel unsafe with anything bigger if I didn't upgrade the brakes at the same time.

My long-term list of things-to-do-to-my-truck (prolly be called 'Ol Blue by the time I get around to all of 'em! ) has upgraded brakes and braided stainless steel brake lines on it.

fastdrvr23 · May 19, 2005

I have a question to ponder ?

If I order a vehicle with 16in rims or 17in rims but the axel ratio is the same, does that not change the over all final drive ratio by not allot but by a little. Meaning its takes more power to turn the factor 17 then the factory 16. If so is then your truck a hair quicker off the line with a 16in then a 17in.

to think of it , take this example; take your factory 16in rim and replace it with a 14in wheel , what would be the results?? would not the engine RPMs be higher at 55 with a 14in rim then a 16in wheel ?

hey also try this. Any 04 burbs with 3.73 gears , whats your RPM at 55 with 16in wheels and anyone with the same but 17in rims and factory tires whats your RPM at 55?

just for fun

Scott

<{POST_SNAPBACK}>

Maybe this will help:

http://www.dodgecharger.net/tech/RPM-Speed...Calculator.html

This has always been my favorite for tire size calculations:

http://www.miata.net/garage/tirecalc.html

JAMIEZ71 · May 19, 2005

As USA said a larger wheel such as going up to a 20" does take more power to start and stop it. That is why the trucks such as the SS and the Joe Gibbs truck have upgraded brakes. As far as the mileage difference I'm sure it's not enough to tell. As for final drive ratio a truck such as a Z71 normally had 265/75/r16 the new ones are coming with 265/70/r17. If you do the math on that it comes out to the same tire size so therefore same final drive ratio.