Hey fellas (maybe more like zxappeal),

Anyone want to help me adjust my speedometer? I've noticed it's off by about 4-5MPH at the sub-45MPH range, and up to 8MPH off at the 75-85MPH range. I've heard it's just a little ring or something on the speedometer cable or something under the hood, but I'm not too skilled to play with it. This is my daily driver car, so it just needs to work... but I am certainly tired of losing "mileage" on my odometer when I'm driving to Duke and back every day for work... Can someone help?

And to think that i've been driving it like this for nearly 20K miles (so how many miles have I REALLY driven, then?)...

Or does it even affect the odometer (I would assume that they are tied together)?

thanks for the help, and the funny "niko you're gay as hell", etc., comments that are sure to follow as well

~niko ^_^

8/13/2005 10:23:12 AM

First of all...what kind of car is it?

What kind of changes have you made? Wheel size, etc...

My expertise ends with swapping out speedo drive pinions. Actual calibration is best left to somebody like Bradley's downtown.

8/13/2005 11:37:46 AM

well, it's a 1995 Honda del Sol, my little pride of joy

it had 13" wheels on it when we got it, and when I decided to upgrade the wheels, I went up to a 15" rim, but lowered the tire height to compensate, so they are pretty much the same overall diameter.... the current tire size is 195/50/15, and my best recollection of the 13's are 175/70/13's or something.

my first questions to those in the tire business have been answered with "ya gotta take it to a shop and they'll charge ya $100 to make it accurate.." is this seriously what people charge to change those little rings on the speedo cable?

I should add that it's always seemed a little off, even when we first got it (with the 13's..) so I'm kinda thinking that while changing the tires/wheels could impact it somewhat, it was already kinda off in the first place

[Edited on August 13, 2005 at 12:11 PM. Reason : ]

8/13/2005 12:09:46 PM

if the outside diameter is the same it really shouldnt have made any difference

8/13/2005 2:28:08 PM

Like ScHp said, same diameter means the same distance covered.

You should verify if your speedo is off, here's the cheap way:

Go 60mph on a highway and time yourself between mile markers. Ideally you should go 1 mile in 60 seconds.

If you go one mile and your stopwatch says like 65 seconds, then you are really going slower than 60mph.
If you go one mile and your stopwatch says like 55 seconds, they you are really going faster than 60mph.

Adjust your speedo and measure it again.

8/13/2005 2:31:36 PM

wheel diameter before is similar to wheel diameter after, but not quite =....

i'm running next to a "known-good" speedo in my wife's car... it's off, so I know that much.

But I do not know how to adjust my speedo.

Any help here?

8/13/2005 2:56:50 PM

It's electronic. No cable to the best of my knowledge. Uses hall-effect type speed sensor which plugs into the tranny where a speedo cable would usually go. Unfortunately, I don't know how to calibrate it.

8/13/2005 5:23:11 PM

so is it something that can possibly be reset then? Or is it "fixed"?

8/13/2005 5:33:20 PM

it can probably be fixed by the right person, or at least improved to be closer to accurate at speeds that matter...but it may not be worth messing with

8/13/2005 5:47:58 PM

ok, that's pretty much how I feel too, except for the fact that I'm wondering if it's affecting my odometer much...

8MPH off at higher speeds (which i do pretty much 90% of the time with my commute) x 30,000mi/year = pretty far off in the long run

Right?

8/13/2005 6:18:41 PM

off about 2900 miles per year

8/13/2005 10:10:34 PM

Compare the odometer to the mile markers too. The speedometer on my truck reads around 5 mph too high, but the odometer seems to be right, based on the mile markers (540 is a good place to check; they have markers every two tenths of a mile).

8/13/2005 11:48:14 PM

there is a lot of "theory" going on in this thread that isn't accurate.

when you change tire sizes, your speedometer gets off by a percentage. it doesn't matter how fast you are going, the odometer will always be off by a percentage.

if your speedometer reads 8mph slow at 75mpg, then it is off by 10.66%. 10.66% of 45MPH is 4.8MPH, which is the 4-5MPH you see it off at 45. you will notice that it is off at every speed, it is just more noticable at higher speeds where the percentage relates to a much faster speed that it is off.

now, if your speedometer is off by 10%, then when your odometer says you have gone 100 miles, you have in fact gone 110 if your speedo reads slow. if your speedo reads fast, then you have in fact only gone 90 miles.

oh, wanted to add that you can find the circumfrence of the stock tire and the circumfrence of your current tire, and your speedo will be off by the same percentage difference as the circumfrence of the two tires.

adjusting could be electronic or mechanical. if it is mechanical, you will need a new speedo gear to counteract the change in tire size. that will require parts (which may not exist for your specific tire size, or may be hard to come by and expensive) and labor to change.

if it is electronic, it can probably be fixed by reprogramming whatever computer controls the speedometer and odometer at best, or it will require a converter box at worst. who can do either of these, i have no idea. i'd try the dealer first, if that is too expensive, then try to find a message board related to your car that might could tell you who can do that sort of thing. you could also try asking at bradleys, the speedo shop at blunt and new bern (i think it's blunt) downtown.

if $100 is too much for you to fix it, then i'd suggest you just live with it, cause it isn't going to get much cheaper and could be much more depending on car.

[Edited on August 14, 2005 at 12:18 AM. Reason : .]

8/14/2005 12:17:47 AM