Topic: Speed Sensor

[parkcaka]

Do you know where the speed sensor is?

Front or Back wheels? common sense says they should be on front wheels.

i am asking because if they are on front wheels I can keep the front tires stock but try something different (bigger wheels or tires) with back tires without having any speedometer miscalculations.

[DeepBlueGXP]

It's either on the back wheel or the transmission since when you do burn outs the speedometer goes up even though you are sitting still

[Treeman]

I thought these were generally on the transmission.

[Ben L]

That where it is in the car we built from scratch.

[parkcaka]

hehe i'm a cyclist how could I guess that

thanks guys.

[2kwk4u]

Be careful doing what you're trying to do.  I think your ABS might freak out.

[Gentleman Jack]

It's either on the back wheel or the transmission since when you do burn outs the speedometer goes up even though you are sitting still

I vote this the best answer solidly based in fact to ever have been given on this forum.

GJ

[clif]

Do you know where the speed sensor is?

Front or Back wheels? common sense says they should be on front wheels.

i am asking because if they are on front wheels I can keep the front tires stock but try something different (bigger wheels or tires) with back tires without having any speedometer miscalculations.

It is on the rear.  I know this because after I painted my calipers, a wire became abraided and freaked out the ABS system to the point that the car would not drive at a steady speed!  When I took it to the dealer, they showed me the clip that it pulled loose from.  After they repaired it under warranty,(several hundreds of dollars worth!) I tipped the mechanic who made no mention of my pretty caliper color in his writeup!  LOL

Clif

[Critterman]

Clif,  That is the wheel speed sensor you are talking about, not the input for the speedo.

So it really depends what parka is asking for.  Speedo input or wheel speed sensor.  Each wheel has a sensor that basically counts revolutions, when the revs of one wheel differ from the others by x% the braking system responds by releasing pressure on that wheel during braking (anti-lock) or in the case of traction control applying a bit of brake.

Speedo input is most likely a sensor in the tailshaft of the transmission.

Simple explination.  Engineers can if they like be more precise.

[clif]

Gotcha!  Thanks, I was not intending to give incorrect info!
Clif

[parkcaka]

Clif,  That is the wheel speed sensor you are talking about, not the input for the speedo.

So it really depends what parka is asking for.  Speedo input or wheel speed sensor.  Each wheel has a sensor that basically counts revolutions, when the revs of one wheel differ from the others by x% the braking system responds by releasing pressure on that wheel during braking (anti-lock) or in the case of traction control applying a bit of brake.

Speedo input is most likely a sensor in the tailshaft of the transmission.

Simple explination.  Engineers can if they like be more precise.

thanks.

I will put 19" wheels on all wheels and 265-40-19 tires on back wheels. The tire Size Calculator says that the total diameter of the tire is %2.5 longer than the stock 245-45-18 tire.

I will put 245-40-19 tires in the front so the diameter won't change from the stock diameter.

So if the sensor is in the front I will get perfect speedo reading.
if it is in the back I will have %2.5 error on speedo reading.

[Ben L]

Uhh.  

I think what people have been saying is that the speedo sensor is in the tailshaft of the transmission.  NOT the wheels.  That's what I read.  

I know you want to run those 19s so much that what people are trying to say may not be getting through.

The calculator I used shows the speedo being off more like 6.4% too slow for the rears, meaning the speedo will read 60 mph, but you will be going 63.8 mph.  The front tire change is minimal.  Like .1%,

But if the sensor is in the trans, I think the calibration difference is going to be a combination of front and rear.

Probably not enough to get worried about . . .

[Critterman]

I run 255x45x18's on my car, at 60 on the speedo I'm doing 62, 65 is 68, 70 is 74.  I am at 1-1.5% difference in size.

[parkcaka]

yes I'll put 19"s for sure. I was just trying to learn how much error I will get from the speedo.

i see that not much will differ since I'm not really measuring 0-60 etc.

thanks

[Ben L]

The difference won't go away because its KPH.

[parkcaka]

The difference won't go away because its KPH.

???

"i see that not much will differ since I'm not really measuring 0-60 etc."

what I meant is;

I am not a racer or try to measure precise 0-60 mph or 0-100 kph runs
so my speedometer reading 63kph when the real reading is 60kph is not a problem for me.
if it was 70 kph when the real speed is 60 kph, then it will be annoying.

on weekends some of my friends keep measuring their 0-60 runs everytime they do an upgrade. if that was the case I would have a problem. i was referencing to that.

[DaveOC]

I run 255x45x18's on my car, at 60 on the speedo I'm doing 62, 65 is 68, 70 is 74.  I am at 1-1.5% difference in size.

That's about the error in my speedo with absolutely stock wheels and tires (at least according to my GPS readout).

[2kwk4u]

You feeling OK today, BenL?  I don't follow the logic in your second to last post... or understand where the question popped up about KPH that you answered in your last post.  Maybe I'M the one that's not OK   

[Gentleman Jack]

You feeling OK today, BenL?  I don't follow the logic in your second to last post... or understand where the question popped up about KPH that you answered in your last post.  Maybe I'M the one that's not OK   

I think, but am not sure, that what BenL meant was this:

The difference won't go away because its KPH. 

Not to speak for him, but that is how I interpreted it, and I thought it was funny

GJ

[Sol Asylum]

FYI
According to the maintenance manual the vehicle speed sensor (VSS) is in the tail section of the transmission on the left hand side (manual trans).  The auto trans has the speed sensors internal of the transmission.  The speed sensors are a solid state device so most likely there is a way to calibrate the speed but that I don't know about for sure.

[Uranium-238]

I think Goat...errr...The Comedian told me the Lyndon can re-calibrate the speedometer. I'd imagine it wouldn't be too hard for a competent tuner. 

[Ben L]

You feeling OK today, BenL?  I don't follow the logic in your second to last post... or understand where the question popped up about KPH that you answered in your last post.  Maybe I'M the one that's not OK   

I don't know what came over me. . . .   After pointing out for the ?? time that the sensors are in the trans, NOT either wheel, I guess I just snapped.

I must have been on the iPad.

[Gentleman Jack]

Ben L,

are you sure?  My cousins aunt had a friend with a dog that knows a dog that lives with a guy that said he owned GM and he said it was in the spare tire?

GJ