Need some mentoring on how to convert Rpm to vehicle speed. I have a 53 3100 with a 54 truck engine and the 4.11 rear. I currently have 235/70/15 on all 4. I have tried the online converter posted here but no luck. I would like to know that at a RPM of 2000 what would my actual speed be. Thank you for you help.
Last edited by Peggy M; 11/07/20232:20 AM. Reason: added more info to the title
Your tires with that size turn 745 times per mile (got that from Tire Rack's specification page for a tire of that size). So at 2000 RPM engine speed, the tires would be turning 487 rpm (2000/4.11), or 0.65 miles per minute (487/745). Mulltiply that by 60 min per hour and you get 39 miles per hour.
Kevin 1951 Chevy 3100 work truck Follow this saga in Project Journal Photos 1929 Ford pickup restored from the ground up. | 1929 Ford Special Coupe (First car) Busting rust since the mid-60's If you're smart enough to take it apart, you darn well better be smart enough to put it back together.
I think we still need more info to make the calculator work out (guessing you are referring to the one in this Calculate RPM Tech Tip ).
What transmission are you using (output final drive)? If you have an overdrive transmission, that affects the output RPMs.
What is the overall height of your tire (not all 235/70/15's measure the same)?
EDIT: Kevin beat me to the punch. Still need to confirm on the questions I asked though as they can make a difference.
Last edited by Gdads51; 11/05/202311:55 PM. Reason: added info
~ Dan 1951 Chevy 3 window 3100 Follow this story in the DITY Gallery "My Grandpa Carl's Truck and How it Became Mine" 1966 Chevelle (Wife's Hot Rod) | 2013 Chevy Silverado (Current daily driver) US Army MSG Retired (1977-1998) | Com Fac Maint Lead Tech Retired (1998-2021)
rpm÷ratio (4.11) x tire circ (in feet)x 60 ÷ 5280. My 54 3100 3.90 rear, 7.5ft circumference tires... 2000÷3.9x7.5x60÷5280=43.8mph.
~~ Jethro 1954 3100 Back to Life In the Dity Gallery 1951 3100 (gone) / 1956 4400 (still in the neighborhood) / 1957 6400 with dump body (retired) / 1959 3100 panel (in the woods junked) / 1978 Custom Deluxe K10 / 1993 S-10 4.3 / 2004 Chevy Crew Cab / 1945 John Deere H / 1952 John Deere B / 1966 John Deere 2510 / 1967 John Deere 1020
Circumference = Pi X Diameter- - - -27" height X Pi (3.14) = 84.78 inches. Round off to 85 inches. 85 inches = 7.08 feet. 746 turns/mile.
It should be simple to plug un the figures from there with any of the online formulas. Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
Below is a screenshot of your “numbers” plugged into the calculator and computed result.
Looks like just a smidge over 39 MPH with given data.
Last edited by Gdads51; 11/06/20232:44 PM. Reason: spelling
~ Dan 1951 Chevy 3 window 3100 Follow this story in the DITY Gallery "My Grandpa Carl's Truck and How it Became Mine" 1966 Chevelle (Wife's Hot Rod) | 2013 Chevy Silverado (Current daily driver) US Army MSG Retired (1977-1998) | Com Fac Maint Lead Tech Retired (1998-2021)
Where is that calculator? Is it on this site somewhere?
1950 Chevrolet 3100 (Ol' Roy) 1939 Packard Standard Eight Coupe (The Phantom) | 1956 Cadillac Coupe de Ville (The Bismarck) | 1956 Cadillac Sixty Special Fleetwood (The Godfather) | 1966 Oldsmobile Toronado (The Purple Knif) | 1966 Ford Mustang (Little Red) | 1964 Ford Galaxie 500 coupe | 1979 Ford F-100 | 1976 Ford F-150 (Big Red) | 1995 Ford F-150 (Newt)
Results for the OP's question on the calculator that EchoBravoSierra posted.
Kevin 1951 Chevy 3100 work truck Follow this saga in Project Journal Photos 1929 Ford pickup restored from the ground up. | 1929 Ford Special Coupe (First car) Busting rust since the mid-60's If you're smart enough to take it apart, you darn well better be smart enough to put it back together.
Thank you all for the info and illustrations and site! This web site and member have a wealth of info. Haveing owned a 54 & 53 3100's in my younger years never worried much going down the road at 50mph and wondering about engine rpm. Thanks!
~ Dan 1951 Chevy 3 window 3100 Follow this story in the DITY Gallery "My Grandpa Carl's Truck and How it Became Mine" 1966 Chevelle (Wife's Hot Rod) | 2013 Chevy Silverado (Current daily driver) US Army MSG Retired (1977-1998) | Com Fac Maint Lead Tech Retired (1998-2021)
1950 Chevrolet 3100 (Ol' Roy) 1939 Packard Standard Eight Coupe (The Phantom) | 1956 Cadillac Coupe de Ville (The Bismarck) | 1956 Cadillac Sixty Special Fleetwood (The Godfather) | 1966 Oldsmobile Toronado (The Purple Knif) | 1966 Ford Mustang (Little Red) | 1964 Ford Galaxie 500 coupe | 1979 Ford F-100 | 1976 Ford F-150 (Big Red) | 1995 Ford F-150 (Newt)
I am curious as to why you would like to know specifically what speed you are going at 2000 RPM. There engines give more bang for the buck considerably above 2000 RPM. The sweet spot is between 2400 and 2600 RPM in my experience. Upwards of 3000 is not an issue either if you need to go highway speeds from time to time. These engines tend to lug at 2000 RPM.
1952 5-window - return to "as built" condition | 1950 3100 with a 235 and a T-5 transmission
Dave and everyone participating in this conversation. Since the conversation seems to be continuing, this topic is more related to your/our trucks “driveline” so I have moved the thread to the Driveline forum.
Best Regards! 😉
Last edited by Peggy M; 11/07/20233:48 AM.
~ Dan 1951 Chevy 3 window 3100 Follow this story in the DITY Gallery "My Grandpa Carl's Truck and How it Became Mine" 1966 Chevelle (Wife's Hot Rod) | 2013 Chevy Silverado (Current daily driver) US Army MSG Retired (1977-1998) | Com Fac Maint Lead Tech Retired (1998-2021)
Thanks to all for the input. I was trying to verify mph vs rpm in my truck.When I take the spped up to 50,55 my tack is reading in the range of 2500 to 2800. I usually try to keep under 3000 but it will takemore and not hesitate-----however the engine noise picks up quite a bit. I will do the download on cell as suggested------Happy Motoring to all!----Dave
Do you have a running tachometer in your truck? If so, download and use "Speed Box" (a GPS app) for your speedometer.
Craig
My '50 Chevy 3100 5 window, '62-235cu, 3:55 rear My truck ....... Respect The Rust If I'm not working on my truck, '65 m00stang or VW camper, I'm fishing with the wife or smoking Salmon.
Try making a run with the fan removed- - - -it's not needed above about 40 MPH anyway- - - -and I think you'll be able to figure out where the extra noise is coming from. Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
