How many revs at 60mph?

[twobone]

Everyone has a different set of variables from tire size to rear axle and gear box.

 

I think I'm geared very low with my 185/60/13 tires and 4 speed box

 

At 60mph, what are your RPMs?

 

Mine is about 3,800

[bsimon]

For comparison...

 

3350@60MPH in Direct.

2900@60MPH in Over.

 

225/50/16

3.92 axle

 

I drive on the expressway in Direct unless I'm going faster than 80. Overdrive is just too friggin' noisy to be comfortable.

[dvl]

I'm predicting an engine speed of 3748 RPM for my car at 60mph (I'll verify when it's finally finished), with a 4 speed, 185/60/13 tires, and a 3.90 to 1 rear final drive ratio.

I hope this helps,

Dave

[Ian7]

Everyone has a different set of variables from tire size to rear axle and gear box.

 

I think I'm geared very low with my 185/60/13 tires and 4 speed box

 

At 60mph, what are your RPMs?

 

Mine is about 3,800

 

Very typical for a 4-speed Kent.

Your engine isnt happy down low anyway, its not a modern fuel-injected torque producer, and FormulaFord guys run them between 6000 and 7200.

[Kitcat]

TwoBone, at 3800 rpm my X-flow Cat w/5sp on 15" wheels was doing abt 75 mph. Fifth was a nice cruising gear.

[twobone]

I wish I was going 75! I thought I heard the top gear of a 4 speed and a 5 speed T9 were pretty much the same. Maybe I need a different rear axle ratio

[Kitcat]

Your 4th is same as my 4th, so my 5th is overdrive. Moving to bigger diameter wheels and or tires mite be simplest solution, tho you wld lose some acceleration. The rear tires on my Birkin are abt an 1/2 inch taller than the fronts (Toyos vs Avons)and handling is still excellent.

[bsimon]

I heard the top gear of a 4 speed and a 5 speed T9 were pretty much the same

 

Top gear in the T9 is an overdrive ratio. 4th is direct. Top gear in a Rocket box is direct.

[11Budlite]

My Birkin with 205/50-15 tires, 3.9 rear end, and .84 T9 5th gear is turning 2875 rpm at 60 mph.

 

Here's a couple good gearing calculators, one from member JohnCh.

 

[/url]http://www.throttle-steer.com/downloads.html

 

http://www.our-nest.co.uk/Caterham/html_files/Files.htm

[locost7018]

My 4 speed 1300cc xflow with 205/15 50 tires and a 3.90 diff turns 4200 @ 70mph. It really sings!!!! Would love to have a 5 speed. Russ

[sequential7]

3450 @ 60MPH, but that still leaves me with another 6,750 RPM to play with :drool:

[ihckb2]

How many of you have an accurate speedo? Chances are most are out at least 5 miles an hour. Do a 10 mile run with a GPS unit to check.

[twobone]

My 60mph reads at about 77mph. Of course that also means my odometer is spinning too fast to!

[JohnCh]

About 2650rpm at 60mph. My speedo is programmable based on tire circumference, and dead accurate up to 45mph according to our local radar signs. Doubt it gets into any significant error over the next 15-25 mph.

 

-John

[The Stig]

I added a cycle speedo to my previous car (actually the only one that worked) and it can be calibrated perfectly. Cheap too but wireless ones dont work as well.

[lancylad]

Has anyone ever used the gps speedometers?

[HOTTTCAR]

That's all I use on the RV. It also warns me if I am speeding , as if that were possible.

[lancylad]

My mechanical speedo has been acting up so I have been relying on the one on my tom tom gps. I am seriously thinking of buying an actual gps speedometer. Any suggestions would be welcome.

[HankMauel]

I've used the "friendly, advisory" radar on a dead straight section of road out of Sacramento. I got a calculated 18.5 mph per 1000 rpms. I have "vintage" sized tires...from the days when the tires were skinny and the drivers were fat .... 155 x 13 (80 section) tires with a 3.90 rear end. The BMC A 1275 with .010 over and a mild cam makes about 90 hp. In my