I think that my speed if off. when I had a flat and a friend of mine followed me home I was showing that I was going 55 but he said that we were going 45. I was wondering if my speed sensor is off then will my RPMs be out? it seems like my RPMs change between 2.5k and about 2.8k while driving at 65mph, Im not sure of this but my RPMs seem to change.

 

If you are in neutral and parked are your RPMs off?

 

your friends car could be off also

in 5th gear your rpms should be

2000@50mph
3000@75
4000@100

check that and see if its off

 

Wow the manual trans cars sure have alot lower gearing. My 91 VG Auto is just a lil over 2k rpms at 65mph, 3100 rpms at 100 mph.

 

He also has a VE manual which is rated at a higher max also so things are gonna be different.

 

well I went out driving and at 50mph in 5th gear I was showing 2,000 RPM.

if my speed sensor is off will that make my RPMs wrong also?

my friends car is a new 2005 scion TC. he did get the upgraded 18s from the dealer and he asked about his speed being off when he first got them and they told him that getting the rims that he got would not do anything to change the speedometer. Im assuming its just a smaller sidewall tire.

it just seems that even if Im going 75mph on the highway (speed limit is 65) lots of people are passing me.

 

Speed sensor and tachometer are two seperate items.

 

MAXIMABOI, what is your tire size, and, are they new, well-used, or do u see the steel cables

i just changed my 205/50-16 recycled tires for brand new Hankook h405 215/55/16 and now my speedo is near perfect...(had 10mph diff @70 with the old ones)

and, if your tires are due to get replaced, you can have about a 1/2 inch difference in diameter, which will make a difference on the speedo

 

Also tire pressure affects distance & speed, (thus also mpg calculation.)

Somewhere around, there must be a measured standard. Ask local hiway ppl... Go there and drive, measure, look at u gauge. Accurate speed is quantified with distance & time...

How to adjust your gauge?

See http://www.cardomain.com/ride/748507/22

 

Krannick you are right I do need new tires. when I had my flat my friend drove behind me because my flashers wouldnt work and I didnt want to go any faster on the highway than 55 because thats what the speed rating the the spare was.

when he was behind me on the highway with me having my spare on thats when we had a 10mph difference between us. we havent done it since then. when we got to the tire shop to get my flat tire pluged I asked them about this and they said that with my spare on it wouldnt make my speedometer wrong.

 

if the spare tire was on the rear, he's right

but as wiking said, pressure will change it a little too

 

no the spare was on the front of the car.

I keep my tires at 32psi.

 

Not neccessarily correct. Every Upsize will change your speedometer rating. No matter what it is. Stock is calibrated to a certain rpm at the wheels thus getting your speed. But when you change the size the stock calibration is still set for 15" even though you'r runnin on 18's. Getting a smaller sidewall still wouldn't make it 100% perfect just tries to get it as close to stock as possible. When you change your tires pace him on the highway and see again. His speed is also offset.

 

Spare has a smaller tire diameter. Which tire was it I think the driver's side has the sensor on it.

 

it was the passengers side front tire that had the spare on it.