YACT: Aftermarket rims and our friend, the speedometer

[EyeMWing]

It's my understanding that the speedometer reads off axle RPM or somthing similar (And I don't see any other way to do it).

So, when riceboys change out their rims for "prettier", smaller rims and low profile tires, are they also knocking off the speedo's calibration, thereby helping themselves achieve more of an illusion of speed?

 

[amcdonald]

If you change the rim size you should be wise enough to get the spedometer recalibrated.

 

[minendo]

Originally posted by: amcdonald
If you change the rim size you should be wise enough to get the spedometer recalibrated.

These are the same "wise" guys that put huge bookshelf wings on their car. You tell me if they are wise enough.

 

[raptor13]

The speedometer will be off by the same percentage the outermost wheel/tire circumference increases when the rim change is made.

 

[MercenaryForHire]

Smaller rims? You've got that backwards. Riceboys and Blingers want them phat mAd tyt3 22" y0!

And yes, it does screw up your speedo readings if you go more than an inch off spec. Some cars apparently are calibrated for the default tire sizes (let's say the riceboy favourite - the Civic) - 15/16/17, and will scale properly for those. Anything larger and you'll skew your readings.

- M4H

 

[amcdonald]

Originally posted by: minendo

Originally posted by: amcdonald
If you change the rim size you should be wise enough to get the spedometer recalibrated.

These are the same "wise" guys that put huge bookshelf wings on their car. You tell me if they are wise enough.

We are all just jealous because our cars don't have wings ...or bookshelves.

 

Older vehicles had thier speedometers run off the transmission via cable, modern vehicles use a speed sensor, this transmits data to the PCM (Powertrain Control Module) which signals the electronic speedometer to register the correct reading.
Changing the circumference of the tire will alter the speedometer reading.

 

[xSauronx]

reminds me
our english class went to court one day, to observe the proceedings (traffic related that day)

one guy was clocked at 85mph in a 55mph zone
claimed he couldnt be going that fast because he had smaller rims on his car that, he claimed, wouldnt let him go even past 70mph... *sigh*

i think the judge wanted to kill him, he looked like he did anyway

 

[EyeMWing]

22"? Pffft. Dude, around here they put on little ass 12" shiz and lower it to the ground. Apparently some retard that flunked out of physics class started telling everyone that smaller wheels are easier for the transmission to spin at high RPM.

 

[PCboy]

Like those riceboys care if it makes their gearing taller or a skewed speedometer. For all I know, they need all the downforce they can get from those big wings while parking.

 

[MercenaryForHire]

Originally posted by: EyeMWing
22"? Pffft. Dude, around here they put on little ass 12" shiz and lower it to the ground. Apparently some retard that flunked out of physics class started telling everyone that smaller wheels are easier for the transmission to spin at high RPM.

Lucky you. I can't drive downtown these days without being blinding by some asshole's overchromed gargantuan rims. At least when they're scraping the ground, they can get hung up on speedbumps and sharp curbs.

- M4H

 

[Demon-Xanth]

To limit speed to 70MPH on the average car it'd take a wheel that's about half the diameter of the original. Also known as the brake disk/drums.

The cops and courts really don't care what your speedometer says, they only care what speed you're doing.

 

[ObiDon]

As long as you're smart enough to match your new tire/rim combo so that there's a minimal difference in the overall diameter of the new wheels, you shouldn't have to worry about it.

But, yeah, if you're putting some tiny gold-wire Daytons on your Honda then you should recalibrate.

 

[MercenaryForHire]

Required Riceboy Thread content:

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- M4H

 

[zixxer]

Originally posted by: EyeMWing
22"? Pffft. Dude, around here they put on little ass 12" shiz and lower it to the ground. Apparently some retard that flunked out of physics class started telling everyone that smaller wheels are easier for the transmission to spin at high RPM.

actually the reason 'ricers' 'use' smaller wheels is weight.

my 15inch wheels with good tires wiegh under 20 lbs.
19 inch wheels with good tires will put you in +35, nearing 40lbs.

also.. tires are cheaper.

i run 205/50/15 and my speedo is the same as stock.