actual speed of deuce

[JawSaw]

has anyone done the math on actual speed of deuce when you go to super single tires, i am running MICHELIN G20 PILOTE XL 15.5/80R20 when the speedo reads 30mph how fast am i actually going and what would it the speedo read for 55 mph any help would be appreciated john

 

[dmetalmiki]

At 1200x20 7 mph slow. At 1600x20 9 mph slow. Checked with my satnav. Simply STICK to 2000 rpm and enjoy the cruise whatever the end speed.

 

[frank8003]

Just put MotionX-GPS into your phone and record all trips forever for 99 cents.
It uses GPS and is accurate.
https://itunes.apple.com/us/app/motionx-gps-drive/id328095974?mt=8

 

[Kaiser67M715]

with what speedometer cable ratio? I believe and probably wrong, but its a 1:187 for 11.00x20 tires, and 1:200 for 9.00x20 tires.

depending on that and actual overall diameter of the tire you can range from as little as a 3% to as much as a 12%(I think, math might be off) difference.

I have actually used a permanet marker and marked 30, 40, 55 and 65 on trucks that have incorrectly reading speedos(most due to tire sizes)- takes two seconds to find one of the speed traps, or follow a friend using a car with an accurate speedo, then mark your speedo after some steady driving.

If you wish to get real crafty, you can actually make a new face and install it-no clue how hard it would be to pull apart a military speedo though

 

[Kaiser67M715]

Just put MotionX-GPS into your phone and record all trips forever for 99 cents.
It uses GPS and is accurate.
https://itunes.apple.com/us/app/motionx-gps-drive/id328095974?mt=8

Cool, you want to buy me the phone and a plan so I can use that app?

just playin with ya, but not everyone has a smartphone, or Iphone

 

[frank8003]

not everyone has a smartphone, or Iphone

or IPad .........................................
It is just that the day I got my Deuce I was given an old hand me down iPhone.
Even a NEW one now is <200 bucks which is way less than I spent on brake parts alone.
Now a few years later, I would not be without the thing.
So I suggest to get your girl, the kids, or GrandPop, or friend that has one to go for a ride and record accurately. You don't have to buy one. They can email you all the trips and results.
We used it in the Deuce, GTO, Corvette, 9C1, Volt, Camaro, and various friends wheels too. The thing don't lie.

I don't want you to buy anything
I just want you to know how fast you are going
I present My apologies .....

 

[dilligaf13]

Borrow someone's Garmin GPS or smartphone. I'm no tech-tard but the smartphone is handy. I don't know how many times I've looked at the TMs on my phone while I'm working on my truck or when I'm just killing time somewhere....

 

[dependable]

So you have to have apps in the cloud to know your speed? Relying on someone's tracking system?

Oh heck. I'll leave it at that for now.

 

[sigo]

Did everyone forget about cheap accurate handheld GPSs? You don't need a phone, smart or otherwise. Just buy a cheap used handheld Garmin, Magellan, etc GPS. It'll give you accurate speed and log your trip. No subscription, no fees, no apps, and no cloud involved. One time cost (plus AA batteries).

 

[Recovry4x4]

A while back I spent $20 on Ebay getting an older Garmin Nuvi. It works splendidly and saves the blower battery. I do have a couple of speedo apps but the $20 special is perfect for the job.

 

[armytruck63]

It's like the movie "Dumb and Dumber", only it's "Slow and Slower".

The M35A2 I had would do 57 MPH flat out with stock 9.00 X 20 tires, but that was 100 RPM over redline. I only tired that once. I cruised at 52 to 53 MPH.

 

[turnkey]

If it goes faster than you can run, then it is fast enough for a M35A2.

 

[gringeltaube]

.......its a 1:187 for 11.00x20 tires, and 1:200 for 9.00x20 tires.

Almost right.... Just the other way around: it is a 1:0.187 ratio for 9.00-20s and 1:0.200 for 11.00-20s.


G.

 

[swbradley1]

I just read the thread and got my old Galaxy 3 Android and put DigiHUD on it. I have it on my Galaxy 5 and it is a cool free app.

 

[rustystud]

So you have to have apps in the cloud to know your speed? Relying on someone's tracking system?

Oh heck. I'll leave it at that for now.

I agree with Dependable. I don't like anyone tracking me ! I gave up my smart phone 2 years ago and don't miss it at all now. I spent the first 45 years of my life without a mobile phone and plan on spending the rest of my life without one .
Also for those who are trying to calculate there speed remember, the speedo-head can in itself be a very inaccurate device . That's why the police used to spend a lot of money getting there speedo-heads calibrated on a yearly basis.

 

[Bob H]

has anyone done the math on actual speed of deuce when you go to super single tires, i am running MICHELIN G20 PILOTE XL 15.5/80R20 when the speedo reads 30mph how fast am i actually going and what would it the speedo read for 55 mph any help would be appreciated john

Easy, your tire is about 12.5% bigger than stock, your speedo will be off by that 12.5%
So at 55 indicated you'd be going almost 62 mph

 

[m-35tom]

rpm = (168 * mph * ratio ) / radius

Where:

"rpm" is engine speed in rpm
"mph" is road speed in mph
"ratio" is product of all ratios, in your case
ratio = 0.79 * 1.0 * 6.72 = 5.309
"radius" is the distance from the ground to the center of the axle shaft.

Or if you want to solve for mph then equation is:

mph = ( rpm * radius) / ( 168 * ratio)

of course your tach can also be inaccurate so use a gps.
there are also overdrive kits available.