Tire sizing and RPM
#1
Tire sizing and RPM
My truck has the 4.10's and when I cruise on the highway at 75, my RPM's are at 3,000 with the stock 235/75/15 tires! I want to stepup to some 31s or 32s. I basicaly want to know how much lower i can get the rpm's or how low they are gonna go. Is there some sort of conversion, or chart that anyone has, or what RPM does your truck run at? thanks
#2
#5
#6
bigger tires would definately help keep the rpm's down. Right now with 3.55's and 30" tires it reads exactly 2k RPMs at 60, which is 65 when you factor in speedo error. I've got some 25" burnout tires and they kill my top end, I hit the governor and people are still passin me like nobody's business. With the bigger tires the governor doesn't kick in till 100 actual mph.
here's a decent calculator for figuring out speedo error and stuff. And here is one for figuring out optimum rpm/tire size/gears. Hope this helps..
here's a decent calculator for figuring out speedo error and stuff. And here is one for figuring out optimum rpm/tire size/gears. Hope this helps..
#9
To figure the new RPM @ 75MPH after the tire switch, use this formula:
(old diameter/new diameter) x current RPM @ 75MPH.
You can get the actual tire diameter of a P-metric tire like your 235/75R15 from one of the calculators listed in the posts above.
Remember that most "inch size" tires are usually somewhat smaller than the marked size implies. A "31" is often 30.5~30.7" in diameter, for example. You can get an accurate diameter number from the manufacturer's website specs of the replacement tire you have chosen.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The required brake torque increase due to the tire size change will be equal to
[(new diameter/old diameter) - 1] x 100%
Your truck will still stop but you will need to apply about that much extra pressure to the pedal to make it happen.
(old diameter/new diameter) x current RPM @ 75MPH.
You can get the actual tire diameter of a P-metric tire like your 235/75R15 from one of the calculators listed in the posts above.
Remember that most "inch size" tires are usually somewhat smaller than the marked size implies. A "31" is often 30.5~30.7" in diameter, for example. You can get an accurate diameter number from the manufacturer's website specs of the replacement tire you have chosen.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The required brake torque increase due to the tire size change will be equal to
[(new diameter/old diameter) - 1] x 100%
Your truck will still stop but you will need to apply about that much extra pressure to the pedal to make it happen.
#12
#13
no try about $275 for alloy's let me get the links for ya
http://cgi.ebay.com/ebaymotors/ws/eB...981324050&rd=1
http://cgi.ebay.com/ebaymotors/ws/eB...981534496&rd=1
http://cgi.ebay.com/ebaymotors/ws/eB...981857409&rd=1
http://cgi.ebay.com/ebaymotors/ws/eB...981729963&rd=1
start buying....
http://cgi.ebay.com/ebaymotors/ws/eB...981324050&rd=1
http://cgi.ebay.com/ebaymotors/ws/eB...981534496&rd=1
http://cgi.ebay.com/ebaymotors/ws/eB...981857409&rd=1
http://cgi.ebay.com/ebaymotors/ws/eB...981729963&rd=1
start buying....
#16
Thread
Thread Starter
Forum
Replies
Last Post
TommyC
General Ford Ranger Discussion
13
02-19-2007 11:00 PM