Is there an adjustment on speedometer?

[integ3]

I've got close to stock size wheels and tires(205/50/15), and my speedo is a consistent 10 MPH off...it doesn't matter if i'm going 30 MPH or 70MPH it's about the same ammount off.

Anyone had this problem before?

Thanks.

[1Greyteg]

Ok so what year Teg is it?

What were your stock size tires? I'm guessing 195/55/15? If not what size did you have?

If that is your origional size, then the new speed with the new SMALLER diameter size tire will be 1.6% faster and your speedometer will as an example when it is at 60 MPH be actually traveling 59.0 MPH or Slower.

Smaller tires = raster rotation and a higher final drive Without actually changing the Final Frive.

But, who wants to run around on Smaller rims and tires? It's soo tre Cool to have the BIGGEST Rims of all!

A.

[SlapSmak]

to calculate outside diameter of a tire:
tire size is as follows:
example: 205/50R15
205= size of contact cross section + both sidewalls (inside and outside) in mm
50= percentage of total size the sidewall is (ratio)
15= size of rim tire goes onto
to get outside diameter, multiply first number times ratio number multiplied by 2 (two sidewalls) then add to rim diameter in mm.
205mm x .5= 102.5 x 2=205 + (25.4(number of mm in an inch) x 15)=586 mm = 23.07 inches outside diameter
same equation using a 195/55 15= 23.44 inches

difference in diameter is .9842%, less than 1 % difference, this should not lead to the problem you have with your speedo.
the 205/50r15 is a plus zero tire size to the 195/55r15. plus zero is defined as outside diameter being within +-2% of OEM

and how do you know your speedo is off? have you checked it against the mileage markers on the interstate with a tachymeter?
and no, thats not tachometer, a tachymeter measures work, jobs done in a time period and can be used to measure true speed by measuring the time it takes to travel 1 mile and convert that into miles per hour. the Tachymeter is often found on high dollar watches such as the Tag on my wrist.

[nov0798]

yea what the last guy said

[White98LS]

No, actually, NOT what the last guy said. Don't mean to be an ass or anything, but your calculations are wrong. Well, okay, they're right for finding the diameter, but what we need is the rolling circumference of the tire, or the distance traveled each time the wheel and tire make one revolution.

Circumference is the diameter (or two times the radius) times pi, 3.14159..... So you actually get a change of about 3%, not 1%. Which can make a significant difference. Plus Honda, as well as most car manufacturers, calibrates their speedos to read a couple of mph high. If you don't believe me, read the article in Car and Driver a couple of months ago. They tested dozens of different cars and the vast majority read high, especially German cars!

I think I have about +3mph error stock on my car, plus about +3% from my 195/55's on 14"s instead of 60's. So my car, as verified by every single readout thing that displays your speed that I have ever passed (about 12 different ones, multiple times with the same results), reads about 4-5mph high at 30-40mph, and about 5-7 high on the freeway. One of the reasons that I hate those idiotic "post your top speed" threads.

[SlapSmak]

White LS, you are an ass. the rolling circumference of each of those tires is respectively:
205/50/15=72.48"
195/55/15= 73.64"
using normal math still equals .98% difference, or to make it real easy on you, take the larger tire and convert it to miles, which is 5280 ft x 12 to convert to inches=63360 do the division to convert to number of rotations to go one mile:
63360/73.64= 860.4 rotations. now lets say that you are traveling at 60 mph, 1 mile a minute, which is 14.34 rotations a second. if the 205 is rotating at the same rate 14.34 rotations per second in one minute it will go 5196.82 ft, which by still doing normal math is 98% of a mile. still only a difference of +- 2%. It would take 5.86 seconds to finish the mile out, giving a total time of 65.86 seconds to go a mile, which on a speedo would be 54.66 MPH, a difference of 5.33 MPH, which STILL does not account for the difference he is showing on his speedo.
and to top it all off, this isnt a post your top speed thread , his question was wheather or not he can calibrate his speedo.
must suck not being able to read or do math. the american education system strikes again.

[White98LS]

Where did you get those numbers? I'm not saying you are necessarily wrong, I'm just wondering where exactly they came from. Why is my math not "normal" math? The equation to find the circumference of a circle is generally learned around 8th grade, I don't think it's that radical of a thing.

Yes, with your numbers that only amounts to +5mph and change, but half of my post was relating to the speedometer error that each car comes with from the factory. Factor in the average +3mph or so that Hondas tend to have from the factory at that speed, and you're getting close enough.

Also, I said "those" top speed threads. When did I say that this is one?

Wow, you're really funny with the whole American education thing. Gee, that hurt. : I was trying to not be an ass, maybe I ended up sounding like one, sorry but I had just been through a 16-hour day after Prom, so I was damn tired. But you obviously weren't even trying to not be an ass when you came up with something like that. For your information, I have a 1440 SAT and am one of about 30 freshmen admitted to the U.W. Business School. Yes, that's an institution in the United States, but whatever. I know what I can and can't do, and it's not your job to dismiss me (as well as almost everybody on this board) as being dumbed down by our society.

[integ3]

Uuuuum...thanks for the replies...or arguements. The reason why I know that i'm off by this much is because i've paced myself with a buddy of mine that has stock size wheels and tires on his 01' prelude. And plus, i've had this same size tire and wheel combonation on my 90' teg and was not this much off on my speedometer. Oh yeah, this is on a 1994 LS teg.

One more question, do our speedometers run off of a cable or is it electronic?

Thanks again.

[White98LS]

Sorry for the disputes. What size were the stock tires on the '90? I'm not sure at all but I think that the speedo is electronic. But I'm making that unsure based only off of the fact that when I installed my indiglo gauges (which burnt out and are no longer on there), there were only electronic plugs connected to the back of the cluster.

[SlapSmak]

94 has an electronic pickup. my GSR is off by about -5 MPH by clocking with the mileage markers and with a GPS. i dont think there is a way to calibrate. I have 205/50r15s on my Type R and it is -2MPH. My point was even with the .98% difference in tire size, it didnt account for 10 MPH difference in speedo calibration. sorry it took so long to reply, i couldnt regain my composure after the long day after prom comment. congrats on your 1440 SAT score dude you beat me by 10. maybe a good DOT COM will pick you up with your Business Degree once you graduate. Then again, the world needs ditch diggers too. the smart ones keep em straight.

[White98LS]

Good score, man. Yeah I'm gonna stay away from those dot-coms for sure. I'll stay with finance and investing.

It really kinda sucks that there isn't a way to calibrate the speedo. Cuz even if it's only reading 2% high because of tire size, that means your odometer is clocking faster than usual too, so we're all screwing ourselves for resale value. Okay, so it isn't a huge deal, but still, it sucks ya know?! It's worth it for the advantages though. At least it seems like you get better gas mileage! Actually, I kinda like that mine reads around 5mph high because that way when I think I'm speeding, I'm really not. The only thing is the parents forget every time they ride in it so I have to tell them why I'm going so fast by a cop.