crowley:

lol thats complete disvirgining of the car na. i doubt d speedometer would even work again like i said, a wheel made for that car. a car comes with a 15" Wheel, nd programmed to take upto 18" of that same brand make, installing a 20" would void the calibrations. yea. nd if its a fully computerized car, might even lock the car. manufacturers dnt like u messing around with their cars.

adanny01:


Vehicle speed sensor is located in the transmission. Vehicle speed sensors are usually located at the transmission while wheel speed sensor is at the wheel.

Speedometer uses that of transmission (VSS).

ABS uses both (WSS and VSS)

Vehicle Stability Assist uses both too.

If either VSS or WSS goes bad, ABS and VSA stops working. If WSS goes bad speedometer is not affected.

erico2k2:

well I have been at work hence my very brief and short reply now Im home
I have read fru your quotes and that of crowly.I dont know how new your own car is so i cant say but Im going to use my car as an example and how its system works hope it thrwos more l ight into the VSS relative to it uses.
Now my car is a 2012 Range Rover sport Autobiography so comes fully loaded this is how the VSS works
Now the Variable Assist Power Steering (VAPS) system uses Vehicle Speed Sensor (VSS) input to regulate power steering pressures for higher assist at slow speeds, making parking lot maneuvers easier to perform. Honda does that by a pressure switch mounted on the pressure line between pump and steering rack. The switch senses a drop in pressure as you attempt to turn the steering at slow speeds, the ECM raises the idle speed. The system works better on cars equiped with electric trottle. The Anti-Lock Brake System (ABS) uses VSS information to determine when a wheel is locked up and releases pressure to that wheel to maintain directional stability. Some vehicles use separate sensors for the ABS, but it is common that the computer uses the information from the wheel sensors to act as a VSS. In my opinion, ABS uses both Wheel Speed Sensor and Vehicle speed sensor. Each wheel speed is compared to the vehicle speed and anyone short of the set threshold is considered locked. The ABS module kicks in. For example, many newer Ford vehicles use a rear axle mounted speed sensor for both ABS and computer related vehicle speed functions. Instrument Cluster (IC) and Hybrid Electric Cluster (HEC) modules use vehicle speed info for speedometer operation.I have a 2004 jeep liberty in Nigeria this is waht it uses as shown on that pic.
The vast majority newer Vehicle Speed Sensors are of the permanent magnet type, and function much the same as a CPS sensor. The sensors can be mounted either in the transmission case (like yours) or rear differential assembly(Jeep and Ford). Those in the transmission are typicaly gear driven, and those in the differential function by using a trigger wheel mounted with the ring gear. Both style sensors perform the same task.
I hope this is more clearer

Conner44:


Let's say we both go to berger and purchase a VW beetle each and are to use it to race the next day

You take yours home and prepare for the race while I take mine to ladipo and switch in 16" rimmed tyres before going home

Come the next day because I have larger tyres I will be faster than you even if both our speedometers read the same 120kmph

Why? Simply because I have larger tyres

Uncle ejoor, wat if the tires in the same car are not the sane size? Does it av any effect on the speed? Or let's say u have 19" at the rear and 16" front? Because from ur explanations 19" tires can overtake 16" tires fixed in the same car.

Assuming I didn't switch tyres we would be evenly matched in a race and It's that simple

Conner44:


Let's say we both go to berger and purchase a VW beetle each and are to use it to race the next day

You take yours home and prepare for the race while I take mine to ladipo and switch in 16" rimmed tyres before going home

Come the next day because I have larger tyres I will be faster than you even if both our speedometers read the same 120kmph

Why? Simply because I have larger tyres

Assuming I didn't switch tyres we would be evenly matched in a race and It's that simple

Gentlelife50:


Uncle ejoor, wat if the tires in the same car are not the same size? Does it av any effect on the speed? Or let's say u have 19" at the rear and 16" front? Because from ur explanations 19" tires can overtake 16" tires fixed in the same car.

erico2k2:

Gentlelife50:


Uncle ejoor, wat if the tires in the same car are not the same size? Does it av any effect on the speed? Or let's say u have 19" at the rear and 16" front? Because from ur explanations 19" tires can overtake 16" tires fixed in the same car.

Gentlelife50:


Uncle ejoor, wat if the tires in the same car are not the same size? Does it av any effect on the speed? Or let's say u have 19" at the rear and 16" front? Because from ur explanations 19" tires can overtake 16" tires fixed in the same car.

Conner44:


In this situation I believe the speed will be the determined by the wheels propelling the car. Like in your example if you're driving a front wheel drive vehicle and You have 16" in front then the car will move according to the size of those front wheels and the 19" rear wheels will just be dragged along

erico2k2:

Would you have different wheel size your car

Conner44:


some cars actually come with different wheel sizes for the front and rear but not our usual conventional types of cars.

I can't put different wheel sizes on a Toyota camry, it's never done

erico2k2:

Name one such car plz

Conner44:


I can't know the name because it's been a while I saw such cars and it was on tv. These cars are "old school" looking and actually vintage so they're unconventional.

Maybe if I rummage around in Google I can get a picture of one for you

erico2k2:

Unless you are talking about a tractor,I just upgraded to a 17 inch tyrs on my BMW, last week,I dont get flashes on the 40 m/hr speed cameras meaning my car maintained its usual speed with the speedo.

Conner44:



What was your previous rim size?

also remember the speed difference would be minute depending on the ratio of your upgrade.

erico2k2:

15 inches, the tolerance in this cam is 2m/hr

Conner44:


Okay that's a big leap in rim size

Okay, so what about you old and new tyre profile? Can you tell us the dimensions for both the old and new ones

erico2k2:

Same thing 45

Conner44:


That's why your speed is still constant. You only increased your rims but used the same height of tyres. Now assuming you raised the tyre height by just an inch there would be a difference.

erico2k2:
,
Re read what you just wrote and do the maths, same aspect ration different rim size and re evaluate you reply.

Conner44:


Okay, I'm not an engineer so I will explain in layman terms as i understand it. In the picture below (it's just a rough hypothesis)

What you had under your car was fig. A

What you now have is fig. B

meanwhile assuming you did your upgrade as in fig. C, I'm certain your trusty speed camera would be telling you a different story

Take note of the dimensions as it changes. The tyres in fig. A & B both have the same ride height but that in fig. C is higher than they are

Conner44:


Okay, I'm not an engineer so I will explain in layman terms as i understand it. In the picture below (it's just a rough hypothesis)

What you had under your car was fig. A

What you now have is fig. B

meanwhile assuming you did your upgrade as in fig. C, I'm certain your trusty speed camera would be telling you a different story

Take note of the dimensions as it changes. The tyres in fig. A & B both have the same ride height but that in fig. C is higher than they are

erico2k2:

No Tyre has 5,4 and 3 as aspect ration as described by your drawing, what that means is 3,4,5 are teh % of height of that Tyre.

Conner44:


I see your diagram and I now understand what you meant. I don't really know dimensions so I used those figures just to convey my point. You would be faster because you've increased your ride height but the speed camera might not notice the difference because it will be minute

erico2k2:

The speed cameras do not use minutes, it just judge your speed, there are white lines marking on teh road and the camera show a laser o n this tract,, modern cameras use GPS to mark your speed on these locations too..The one on my way to work is 40 miles/hr with tolerance of just 2 Miles/hr, you do 42.1 miles/hr it flashes and you got a speeding ticket sent to you.,even if I Upgrade my tyres to 19 as Planning to do next week, I aint still going to utter my speedo.

Conner44:



In the context that I wrote "minute" I meant "very very small" and not the time variant.

Well there's no speed cameras in my country so I wouldn't know how those stuff work anyways. Let's wait till next time you upgrade for the final assessment but I still believe your speedometer won't correspond as it used to when you had the 15" rimmed wheels

Conner44:


Okay, I'm not an engineer so I will explain in layman terms as i understand it. In the picture below (it's just a rough hypothesis)

What you had under your car was fig. A

What you now have is fig. B

meanwhile assuming you did your upgrade as in fig. C, I'm certain your trusty speed camera would be telling you a different story

Take note of the dimensions as it changes. The tyres in fig. A & B both have the same ride height but that in fig. C is higher than they are

adanny01:


Very true. Thats the point i have been trying to make.

Diameter will look like

A=15+5=20
B=17+3=20
C=17+4=21
A and B will not affect speedometer but C will.

Circumference of a circle or wheel is equal to or same as the distance the circle or wheel will cover in one complete revolution.

C=2πr

Distance

A=2 x 3.142 x 10 = 62.84
B= same as A= 62.84
C= 2 x 3.142 x 10.5 = 65.98

Difference in distance covered for every totation is 65.98-62.84=3.142

For every complete tire rotation, tire C will be ahead of tire A and B with 3.142inches. This translates to 0.0798m.

62.84 in = 1.598m

A and B will cover 1km in 1000m/1.598m= 625.78 rotations

65.98in =1.676m

If C under goes the same rotation it will cover 625.78 x 1.676 = 1048.81m = 1.04881km

For every 1km C is ahead by 0.0488km or 48.8m.

When
A and B is traveling at 100km/h
C is travelling at 100 + (100x0.0488)= 100+4.88 =104.88km/h

Also every 1 hr, C is 4.88km ahead of A and B.

If A B C are to travel same journey say a 100km journey traveling at 100km/hr, A and B would arrive in 1hr while C will arrive in 104.88/100=60/x. If u simplify for x u get 57.21minutes.

Finally, the torque needed to rotate tire A/B and C cannot be the same. Therefore C would consume a proportional amount of fuel needed for A and B to cover same distance.

erico2k2:

The spedoo picks its readings from a sensor mounted 90 degrees to a sprocket withing the ABS module, the size of the tyres bears no significant to its reading unless you upgrade the ABS module by
A putting a bigger sprocket
B Puting a smaller sprocket then you can alter the speedo.
Read few pages back, we already covered this,I guess you just saw this now.

adanny01:


You covered it but i still dont agree to it.

I still maintain, that if you change the diameter of ur tires, your speedo becomes errornous and would need recalibration.

Speedometer, ABS, Vehicle stability sensors sensors all work the same way by measuring rotation but not distance. They all measure rotation along the drive line or hub. The speedo is calibrated with a fixed tire to know the speed that is a fact u refuse to accept but it is.

My car is a front wheel drive which has 4 ABS sensors. The front measures rotation of the CVT joint while the rear measures rotatiion of the hub. Speedometer sensor is located in the trasnmission.

The way ABS works is it tracks vehicle speed by means of the speed sensor located in the transmission. Say vehicle speed is 100km/h. But there are 4 ABS sensors in each wheel. They all should be doing 100km/h or there about. If one tire becomes 0km/h while the vehicle speed sensor reports 100km/h the wheel is considered locked and ABS kicks in.

Speedometer is independent of ABS but ABS is dependent on speedometer.