| Author | Message | ||
     Parrish R. Blackmon (Discoveryfl) Member Username: Discoveryfl Post Number: 75 Registered: 10-2002 |
What is the change in speedometer reading when running 235/85/16s on a 97 D1? I've heard that it can be as much as 5 miles per off. | ||
| Leslie N. Bright (Leslie) Senior Member Username: Leslie Post Number: 2305 Registered: 02-2002 |
Actually, the stock size was off on mine, and changing to a taller tire made it more accurate. Might want to compare against some other method of measuring speed..... -L | ||
| Rob Davison (Nosivad_bor) Senior Member Username: Nosivad_bor Post Number: 579 Registered: 02-2003 |
borrow a good GPS and take a trip dow nthe highway. take note of the real speed vs what is shown and do the math. i gave up doing the math and just use the GPS as the sped guage. rd | ||
| Joey (Joey4420) Member Username: Joey4420 Post Number: 88 Registered: 04-2003 |
You can also check your speed 'o' by driving 60 per speed 'o' down the interstate and check via mile markers. Use a stop watch and check via the following info. If you purchased larger tires for your light truck or sport utility vehicle, you should verify your speedometer accuracy to avoid unnecessary meetings with the local constable. Installing tires different than your vehicle’s original equipment tire size outside diameter may affect the accuracy of your vehicle’s speedometer and odometer. The chart (below) is provided to help determine speedometer accuracy. If you’re driving on a highway that has a mile marker every mile, it will allow you to determine your vehicle’s exact rate of speed. Follow the speed measuring instructions below: 1. Travel at a constant rate of speed on an open highway and have someone record the number of seconds it takes to travel exactly one measured mile. 2. On the chart, locate the number of seconds it took your vehicle to travel one mile. The speed indicated next to the number of seconds is the true average road speed of the vehicle. 3. Repeat the measurement several times and average the results. Recalibration of your speedometer is recommended if significant inaccuracy is noted. Seconds Per Mile Road Speed 50 72 51 71 52 69 53 68 54 67 55 65 56 64 57 63 58 62 59 61 60 60 61 59 62 58 63 57 64 56 65 55.4 66 54.5 67 54 68 53 69 42 | ||
| Land Rover Certified Used A**hole (Jason) Senior Member Username: Jason Post Number: 503 Registered: 04-2002 |
It's not necessarily going to be "off" by a set speed, like 5mph, but by a percentage. So if the larger tires cause a 10% error, at 30 mph, you'll be 3 mph off, at 50, 5 mph off, and at 100, 10 mph off. As mentioned earlier, use the timing methods or compare your odometer to the freeway milemarkers...then calculate a percent error...because the faster you travel the greater the mph difference will be. | ||
| Paul T. Schram (Paulschram) Senior Member Username: Paulschram Post Number: 1760 Registered: 02-2002 |
The use of a single mile allows for significant error. One should consider using the odometer and mile markers over a much longer travel distance, at a minimum, ten miles, better, 100 miles. I found my truck to be reading too slow by about 15% by calculation, mile markers, and GPS. | ||
| Joey (Joey4420) Member Username: Joey4420 Post Number: 89 Registered: 04-2003 |
When I did my testing, I did over a total of 10 miles, but tested every other mile. (gave me time to reset stopwatch and prepare for next mile. | ||
| michael burt (Mikeyb) Senior Member Username: Mikeyb Post Number: 310 Registered: 03-2002 |
before i threw my gps in the truck and really checked when i went from 255/65's to 265/75's i was constantly pissed off as to why everyone was driving so damn slow...after the gps i am thankfull all the police i passed did not throw me in jail. i was genually suprised how much a difference there was at 65 or 70 mph and i consider myself fortunate that on my last trip to new orleans the highway patrol did not recruit me to break big mud into little mud. mike |
