The Ford Barn

mleder · 01-21-2023, 02:32 PM

Could all math wizards tell me what for instance if my car has the 19" tires and with a 3.78 rear end and a set engine rpm that gets me 55 mph on that tire size with the same conditions what would the highway speed be with a 600 x 16" tires fitted to the car. For extra credit what tire size, make brand may get me closer to the highway speed of the 19" standard tire.

Dan in MI · 01-21-2023, 02:37 PM

Teacher always told me to do your own work.

https://purperformance.com/p-29669-rpm-calculator.html

lrf · 01-21-2023, 04:48 PM

My automotive teacher was my Dad who always said "stay away from old cars, they're nothing but trouble." I now own seven.

Synchro909 · 01-21-2023, 06:00 PM

Quote:

Originally Posted by mleder

Could all math wizards tell me what for instance if my car has the 19" tires and with a 3.78 rear end and a set engine rpm that gets me 55 mph on that tire size with the same conditions what would the highway speed be with a 600 x 16" tires fitted to the car. For extra credit what tire size, make brand may get me closer to the highway speed of the 19" standard tire.

54.035 mph.

Joe K · 01-21-2023, 06:39 PM

You should find the highway speeds "similar."

As it turns out the "exterior diameter" of the wheels are approximately the same. Fatter tires yields "taller" tires too.

I expect you could measure the circumference of each and thereby get REAL close to an actual ratio - but inflation pressure, or more accurately 'resilience' of the tire (i.e. "the squish") may differ slightly making circumference an approximation of actual "wheel ratio."

Joe K

GSleater · 01-21-2023, 10:12 PM

Sponsored Links (Register now to hide all advertisements)

I've found its roughly 5mph difference and that was using my GPS.

jack backer · 01-22-2023, 12:01 AM

285/75/16 31”diameter tire.. Amazon cheapies work for me

ronn · 01-22-2023, 04:25 AM

Joe K. well explained.

AL in NY · 01-22-2023, 12:15 PM

I use 225/75R16 tubeless radials on the 16" 1935 Ford wheels. The diameter is just an 1/8 inch difference then the stock 4.75/19 tires, so the speedometer is within one MPH of stock wheels and tires. Two big advantages here, better braking and handling plus no more tubes!!!!

I bought Westlake tires at Walmart, on sale for $70.00 each.

Tire height: 4.75x19 tire is 29.00 inches
285/75R16 is 32.8 inches
225/75R16 is 29.3 inches

01-21-2023, 02:32 PM	#1
mleder Senior Member Join Date: May 2010 Posts: 181	Highway speed 4.75 " x 19" tires vs 6.00 x 16" Could all math wizards tell me what for instance if my car has the 19" tires and with a 3.78 rear end and a set engine rpm that gets me 55 mph on that tire size with the same conditions what would the highway speed be with a 600 x 16" tires fitted to the car. For extra credit what tire size, make brand may get me closer to the highway speed of the 19" standard tire.

01-21-2023, 02:37 PM	#2
Dan in MI Member Join Date: May 2010 Location: Livonia, MI Posts: 80	Re: Highway speed 4.75 " x 19" tires vs 6.00 x 16" Teacher always told me to do your own work. https://purperformance.com/p-29669-rpm-calculator.html

01-21-2023, 04:48 PM	#3
lrf Senior Member Join Date: Jun 2019 Location: long beach ca Posts: 171	Re: Highway speed 4.75 " x 19" tires vs 6.00 x 16" My automotive teacher was my Dad who always said "stay away from old cars, they're nothing but trouble." I now own seven.

01-21-2023, 06:39 PM	#5
Joe K Senior Member Join Date: Jul 2010 Location: Cow Hampshire Posts: 4,188	Re: Highway speed 4.75 " x 19" tires vs 6.00 x 16" You should find the highway speeds "similar." As it turns out the "exterior diameter" of the wheels are approximately the same. Fatter tires yields "taller" tires too. I expect you could measure the circumference of each and thereby get REAL close to an actual ratio - but inflation pressure, or more accurately 'resilience' of the tire (i.e. "the squish") may differ slightly making circumference an approximation of actual "wheel ratio." Joe K __________________ Shudda kept the horse.

01-21-2023, 10:12 PM	#6
GSleater Junior Member Join Date: Oct 2021 Location: Burbank Washington Posts: 14	Re: Highway speed 4.75 " x 19" tires vs 6.00 x 16" Sponsored Links (Register now to hide all advertisements) I've found its roughly 5mph difference and that was using my GPS.

01-22-2023, 12:01 AM	#7
jack backer BANNED Join Date: Mar 2022 Location: Chenango Bridge NY Posts: 433	Re: Highway speed 4.75 " x 19" tires vs 6.00 x 16" 285/75/16 31”diameter tire.. Amazon cheapies work for me

01-22-2023, 04:25 AM	#8
ronn Senior Member Join Date: Feb 2011 Location: NNNNNNNNJJJJJJJJJJ Posts: 6,800	Re: Highway speed 4.75 " x 19" tires vs 6.00 x 16" Joe K. well explained.

01-22-2023, 12:15 PM	#9
AL in NY Senior Member Join Date: May 2010 Location: Southern Upstate New York Posts: 1,161	Re: Highway speed 4.75 " x 19" tires vs 6.00 x 16" I use 225/75R16 tubeless radials on the 16" 1935 Ford wheels. The diameter is just an 1/8 inch difference then the stock 4.75/19 tires, so the speedometer is within one MPH of stock wheels and tires. Two big advantages here, better braking and handling plus no more tubes!!!! I bought Westlake tires at Walmart, on sale for $70.00 each. Tire height: 4.75x19 tire is 29.00 inches 285/75R16 is 32.8 inches 225/75R16 is 29.3 inches __________________ AL in NY Last edited by AL in NY; 01-22-2023 at 12:35 PM.