37z and speedometer

[beachbunny]

men,how far off is my speedo with 37z.
my leo pal turned his radar unit in and lets the youngsters run traffic

 

[elephantrider]

should be 4 to 5 off. 35's knock it off by 2 to 3.

 

[@JC]

The speedo was off a couple just with the factory 33s on my PW. It was way off with the 35 Nittos I replaced them with. I'd suggest yours could even be a little more than 5 with 37s.

 

[beachbunny]

+ or - ?

 

[elephantrider]

you will be going faster than the speedo reports.

 

[Dr__Bob]

Think about how things work. Your speedometer just measures how fast the wheels turn. That's all it knows. Your actual speed is determined by how fast your car/truck moves. As the diameter of your tires increases, each revolution will cover more ground. So at a given revolution frequency, your car/truck will go faster with increasing tire diameter. And it is linear: 37/33 = 1.12, so you'll be going 12% faster in actual speed with 37" vs 33" for a given reading on your speedometer. [Example: if your speedometer reads correctly with 33's, then at 65mph you'll actually be going 73 mph with 37's.]

 

[beachbunny]

got it , so with stock 35z that came on truck, new equation is 37/35=1.05, so speedo will be 5% less

 

[@JC]

Which Rams come with 35s stock?

 

[elephantrider]

the factory transforce tires are almost 35" .

 

[beachbunny]

i believe my power wagon did, bought it used with 37z

 

[johanh13]

Most of the RAMs come with either of these two tires; 33.2 to 33.4" tall...

 

[@JC]

the factory transforce tires are almost 35" .

Nope.

i believe my power wagon did, bought it used with 37z

And again, nope.

The funny thing is that the stock Duratracs on the PW are actually a hair smaller than the crappy Transfarce tires.

 

[txjfrosty]

factory power wagon tires are 285/70 17 - 32.7"

having said that... my speedo with 37's is off ~13%

50 mph on the speedo and I am really travelling at 56/57 mph

 

[Hstone556]

I Just bought a AEV ProCal Snap to fix my speedometer after I install 37s. I’m too old and not broke enough to justify half-assing my new truck. Seems like the easiest way, and also can adjust tpms threshold.


Sent from my iPhone using Tapatalk

 

[johanh13]

I Just bought a AEV ProCal Snap to fix my speedometer after I install 37s. I’m too old and not broke enough to justify half-assing my new truck. Seems like the easiest way, and also can adjust tpms threshold.


Sent from my iPhone using Tapatalk

Any photos of the 37's on your truck?

 

[Hstone556]

Any photos of the 37's on your truck?

Not yet, still waiting for the rest of my suspension to arrive, everything but the Shocks arrived last week.


Sent from my iPhone using Tapatalk