Changing tire sizes to bigger tires?
#16
07-24-2002, 06:03 PM
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My guess is it prolly has something to do with a 4x4 transfer case. Hi range / low range? I'm a 2WD driver so I can't say for sure.
When I entered my data for some typical winter tires for my Lightning, I got:
Old tire dia: 28.4
New tire dia: 30.0
Differential gearing: 3.73
New gear ratio: 3.53.
Which, according to my calculations, is correct (and just fine for winter driving). I just ignored the Hi/Low info. ymmv.
Anybody else?
When I entered my data for some typical winter tires for my Lightning, I got:
Old tire dia: 28.4
New tire dia: 30.0
Differential gearing: 3.73
New gear ratio: 3.53.
Which, according to my calculations, is correct (and just fine for winter driving). I just ignored the Hi/Low info. ymmv.
Anybody else?
#17
07-26-2002, 09:42 AM
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Check out this site to find out everything you need to know about tire size changes....
http://www.c5-corvette.com/tirecalc.htm
This is a good tire calculator for figuring the speedometer error and it can also calculate the effective (rearend) gearing change and RPM difference.
Hope this will help others.
http://www.c5-corvette.com/tirecalc.htm
This is a good tire calculator for figuring the speedometer error and it can also calculate the effective (rearend) gearing change and RPM difference.
Hope this will help others.
Last edited by TN_Triton; 07-26-2002 at 09:44 AM.
#18
07-28-2002, 09:44 AM
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Here it is in "layman" terms.
The more the driveshaft spins per revolution of the tire, the more power you percieve having (at 20 miles per hour, you will be a 2000rpms, while with lower (higher numerically)gears you'd be at 2500rpms. More power, and towing earlier. Factory Ford basically shows a 400 lb +/- for every jump in gearing.
Every time you raise or lower your tires by 1 inch, you should feel a subtle change in performance. A few inches will be significant, and power loss especially noticed on the highway, where altered aeordynamics come into play. I would just guestimate that 1 inch +/- = .30 of gearing loss or gain.
Realize that tire and rim weight also make a significant difference in vehicle handling. Going one or two plus sizes taller on a rim/ tire could add a few extra pounds per wheel-which may not seem like much-till you consider rotational mass (1-2 lbs heavier per r/t combo can be significant). This will negatively effect ride, handling, braking-though can increase traction and looks.
Compared to my old 97 (17's w/3.73), my old 2000 (17's w/3.55) and now my 98 with (16's and 3.73's) it feels like I have 4.11's!! At 75 mph I'm at nearly 2400 rpm's. I am looking to lower that number to around a 3.70, and will do so by adding an inch taller tire (and an inch wider).
Anyone want to buy some 6 month old 255/70 16 BFG all seasons...?
The more the driveshaft spins per revolution of the tire, the more power you percieve having (at 20 miles per hour, you will be a 2000rpms, while with lower (higher numerically)gears you'd be at 2500rpms. More power, and towing earlier. Factory Ford basically shows a 400 lb +/- for every jump in gearing.
Every time you raise or lower your tires by 1 inch, you should feel a subtle change in performance. A few inches will be significant, and power loss especially noticed on the highway, where altered aeordynamics come into play. I would just guestimate that 1 inch +/- = .30 of gearing loss or gain.
Realize that tire and rim weight also make a significant difference in vehicle handling. Going one or two plus sizes taller on a rim/ tire could add a few extra pounds per wheel-which may not seem like much-till you consider rotational mass (1-2 lbs heavier per r/t combo can be significant). This will negatively effect ride, handling, braking-though can increase traction and looks.
Compared to my old 97 (17's w/3.73), my old 2000 (17's w/3.55) and now my 98 with (16's and 3.73's) it feels like I have 4.11's!! At 75 mph I'm at nearly 2400 rpm's. I am looking to lower that number to around a 3.70, and will do so by adding an inch taller tire (and an inch wider).
Anyone want to buy some 6 month old 255/70 16 BFG all seasons...?