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how much is speedo off 35 bfgs

1K views 15 replies 12 participants last post by  lord_racer_x 
#1 ·
i have a 2500 with 35 bfgs does any one know how far off the speedo is going to be thanks
 
#4 ·
Take a GPS and check your speed on the dash against it and you will know how far you are off .... not only does the larger tires effect the speedo it also effects the ABS so if you plan on keeping the 35" tires on I would suggest getting the Dealership to reprogram your PCM for the ABS and Pinion Factor ... the only thing you will need is the Revs Per Mile of the tire for them to correctly calibrate it. Just my .02 ... I had this done on my 1500 for 35" and have tald many to do this cause it is well worth it
 
#7 ·
Mines off about 10% with my BFG KO 315/70/17's. When the speedo says 60 I'm going about 65-66 according to my GPS.
 
#9 ·
dslbrnr,

I hope you are wrong about DC not adjusting 06s for greater than P285s (about 33") because if my dealer won't reset my power wagon for the 35s that are going as soon as I get it, I'll be pretty upset with them!

Jim
 
#10 ·
give me a stock tire size and i'll give you an approximate answer (the exact difference depends on the tire rev per mile).
 
#11 ·
dslbrnr said:
The dealer can't go over a 285 tire on the 2006's. Apparently DC won't let them!
It could be that your dealership doesnt have the right updated software in there DRB for the 06 to change it so the easiest thing to tell you is that DC said they cant ... which is probably a line of Bull ;)
 
#13 ·
Stock Tire - 265/70R17 >Search Tires Tire 1 - 315/70R17 >Search Tires
Section Width: 10.43 in 265 mm
Section Width: 12.40 in 315 mm

Rim Diameter: 17 in 431.8 mm
Rim Diameter: 17 in 431.8 mm

Rim Width Range: 7 - 9 in
Rim Width Range: 8.5 - 10 in

Overall Diameter: 31.60 in 802.64 mm
Overall Diameter: 34.36 in 872.74 mm

Sidewall Height: 7.30 in 185.42 mm
Sidewall Height: 8.68 in 220.47 mm

Radius: 15.80 in 401.32 mm
Radius: 17.18 in 436.37 mm

Circumference: 99.27 in 2521.4 mm
Circumference: 107.9 in 2740.6 mm

Revs per Mile: 658.2
Revs per Mile: 605.3

Actual Speed: 60 mph 100 km/h
Speedometer1: 55.1 mph 91.9 km/h

Speedometer Difference: - Speedometer Difference: 8.739% too slow
Diameter Difference: - Diameter Difference: 8.04%

Jim
 
#14 · (Edited)
so do I tell the dealer to recalibrate the ABS and the Speedo? Two different things?

Also, how do u find out the Revs per Mile?
 
#15 ·
I have a 2005 Power Wagon with 4.56's.

I went from 33" to 35" tires. When my speedo reads 70, I am actually doing 75. This was tested by following someone.
 
#16 ·
Cant this size difference be calibrated with the SC programer? or would i still have to go to the dealer?
 
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