ok, I have this problem for a while now... 95 VTEC 215/40/17 tires
I think this problem started to happen after I got my clutch (ACT) replaced with this mechanic... I know he does good work and all but it was my first time delt with him, now the problem is...

my speedo is off... reading shows faster at 0-50mph (but i'm actually below that speed) and reading shows slower at 50+ mph (ie. on highways when it says 75 but I'm actually going 85mph [tested many times with friends to verify]). Basically the speedo works just fine, it increase and decrease logically... it just giving out wrong speeds....grrr
so basically i've been driving by the RPM guage for quite a few months now...

I heard there's a speed sensor at the transmission up in the engine bay and there should be a speed gear too... but i'm not sure where it is and if i can take it out and have a look and fix/replace it because of my wrong speed reading problem... it's getting annoying

hmm you think he might have put it back wrong or it's just old and broke or what? also what needs to be done to get this fixed for a DIY?



Modified by MileHigh at 1:54 PM 9/22/2003

 

the VSS sensor is ran off a rod which is on a gear, and that gear is turned by the speedo ring which is on your Diff. If it broke or anything broke you would have known by some grinding nosie and/or your speedo wouldn't work either. And it doesn't sound like the VSS is going bad cause then your speedo-meter would jump every now and again.

The only thing i can think of is that the gear that turns the VSS, via the speedo ring is the wrong ratio. Or i could be totaly stupid and have no idea what i'm talking about. ITs just the only thing logical to me.

How long have you had the car and also this problem?

 

got the car in year 1997

so I'm still guessing it was the guy who did my clutch (which he had to take the transmission out) and messed up something with my speed sensor or the ring or whatever it was/were...

I didnt really notice my speedometer is bad until I got pulled over in May 2003 (wrote up 84 in a 70 zone... my speedo was reading 75)

I still dont quite understand what you're talking about sorry...

There are no grinding noise that I can hear from driver side when car is moving. Speedo doesnt jump neither.

 

Try and put your stock wheels and tires on and see if you still get the same result.

 

umm, your overall circumference and diameters are larger with those tires, that's why it's reading lower than your speed. your speedometer should be reading 3% slower with that size tire.

helps -> http://www.miata.net/garage/tirecalc.html

 

tire size isnt the problem here, I've been using these wheels 17" and tires 215/40 many many many years (6+years)

 

Kinda shitty picture but you can see the speed sensor on the bottom right. It is located under the throttle body on the tranny. It will have a plug going into the top and 2 tubes as well.
http://www.slhondaparts.com/im...9.jpg[/url]
If you decide to take it out don't pull those tubes until you know it's bad. It will screw with your speed sensitive steering.


Modified by Sephro at 3:59 PM 9/19/2003

 

i believe the size of the rim and tire do affect the gear ratio, and your speedometer reading will not be so acurate also. think the best way to tell how fast your going is by looking at the rpm, 85 and 75 is a big difference, 85 will be above 4000 rpm on 5th gear, and 75 will be below 4000 rpm on 5th gear, my speedometer jumps 45mph higher sometimes and sometimes its normal, i just look at my rpm to see how fast i am going now

 

I understand tire size does make a difference.... but that's not what i asked

 

i am pretty sure you entered the tire diameter size wrong, the stock wheel is 15, plus the tire difference theres no way it can be over 23, unless you have 18s on with 40-45 series tires, thats posible, other than that i dun see how u can have over 23inch of diameter, i get 60 at about 3000rpm, and 80 about 4000rpm

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by ZoNe_HKS &raquo;</TD></TR><TR><TD CLASS="quote">i am pretty sure you entered the tire diameter size wrong, the stock wheel is 15, plus the tire difference theres no way it can be over 23, unless you have 18s on with 40-45 series tires, thats posible, other than that i dun see how u can have over 23inch of diameter, i get 60 at about 3000rpm, and 80 about 4000rpm</TD></TR></TABLE>

you're PRETTY SURE about what I have on my car?

well, the center of the tires looks pretty much at a bit less than 12inches...

here's another chart...

of coz that's for brand spanking new tires

any more questions for me?
well, i answer your questions... but can anyone answer mine? hehe thx

 

come on, someone gotta know what's to do out there...