“the car will not be going as fast as the speedo reads”
Is that NOT the very definition of AFFECTING the speedo accuracy/reading? Speedometers are there to measure the velocity of your vehicle…NOT to see/verify that they match up to whatever RPM’s the engine is turning
shadowfox, I meant that 3000 RPM is not dangerously high but seems high for 65 MPH. I have found out that it is about right for the Honda. He needs a 7th gear.
If you think low tires will effect the speedo readingm now is a good time for you to bow out gracefully.
Honda, Honda, If you put the car up on stands, put it in 6th gear and ran the engine at 3000 RPM. what would the speedo read? How fast would the car be moving?? What would the velocity be?
When the OP said that his car ran about 65 at 3000 RPM, that reading came from the wheels or transmission, not the velocity of the vehicle. How could it measure the velocity? does it have a sencor that reads the speed of the pavement going by? Or by the cracks in the street?
Is there not one person out there who will agree with me and tell these kooks the truth???
No, because you’re wrong again. Tire diameter does effect speedometer reading. You said so yourself, and then proceeded to argue with yourself again.
What you don’t seem to be getting is that 4mph translates to a very small change in the tachometer reading, no matter what the tire diameter is. So the 4mph difference between spec at 3000 and this car’s actual would still be read as 3000rpm, because tachometers aren’t scaled accurately enough for the driver to differentiate.
Please stop trying to prove that your wrong answers are right. The OP came here for answers about his car - which you admitted straight off you didn’t know anything about - not to see a big thread full of bullheaded fighting (and certainly not to see you busily calling people names. We are, after all, adults here - I hope). So far you have said that you don’t know anything about his car, 3000 RPM is high, 3000 RPM is not high, his car is operating as intended yet needs a 7th gear, tire pressure both does and does not effect speedometer reading, and other blatantly contradictory statements that don’t help the OP with his question, and make it patently obvious that you’ve decided to start a fight, and then dig your heels in when you are proven wrong over and over again.
I admit some error in this thread as well - I fed the troll. I won’t do that again - this is my last comment. The question has been answered. As long as the OP ignores your trolling, he’ll get what he needs from the thread.
Elly Firstly…Shadowfax is VERY SHARP…he knows his mechanical “stuff” as we say…More than quite well in fact, I can assure you of that. Beware openly challenging his knowledge and especially with ATTITUDE…as well as mine for that matter. If we make a mistake or are wrong we will admit it…We don’t need to BOW OUT IN SHAME as you suggest. We aren’t here to argue, but to provide ACCURATE info, when we have it… to the OP…to try and assist them… They don’t want to see us have silly arguments…Just as Shadow has stated.
Now…I know what you are TRYING to convey…I do…What you are trying to describe is that the Speedo is calibrated to the gear ratio in the transmission Speed sending unit (Which is BASED on the STOCK vehicle wheel/tire diameter… Right?..LOL…Right…See? I knew you knew this…lol
Now the next issue…Lets Answer your questions…lets get “TECHNICAL” up in here:
"Honda, Honda, If you put the car up on stands, put it in 6th gear and ran the engine at 3000 RPM. what would the speedo read?
–ANSWER-- It would READ whatever it was calibrated to read from the Trans Speed seding unit…Which was ALSO based on/calibrated to the FACTORY wheel/tire size/ final target diameter(circumference)
How fast would the car be moving?? --ANSWER-- As fast as the wheel and tire diameter (Circumference) DICTATE per RPM…not what the Speedo PROJECTS it to be moving
What would the velocity be? --ANSWER-- See Above
ON the OP’s vehicle…while he is driving and looking at his Speedo and RPM’s…in the real world…DRIVING…His wheel/tire diameter will affect his true speed and not always reflect what the SPeedo (says)/is projecting his speed to be…based on the stock wheel/tire size
Do you understand now?
Blackbird
"So the 4mph difference between spec at 3000 and this car’s actual would still be read as 3000rpm"
I have said the 4 mph is not significient. Dosen’t matter.
“3000 RPM is high, 3000 RPM is not high”,
I said 3000 seemed high for 65 mph but not dangerously high
“his car is operating as intended yet needs a 7th gear”,
I said the car was operating as it was built, but could use a 7th gear
It looks like you are bowing out before soneone else tells you that you are wrong about low tire pressure.
Honda, Honda
“Now the next issue…ON the OP’s vehicle…while he is driving and looking at his speedo and rpm’s…in the real world…DRIVING…His wheel/tire diameter will affect his reading on his speedo…and his TRUE velocity of the car…moving thru the world…On his way to Dunkin Donuts…etc… LOL”
The wheel/tire diameter Will Not affect his reading on the speedemeter. You could put 20 inch wheels on the thing and the sppeedometer would read the same at 3K RPM (68.7) The car would be going faster than the speedometer is reading, tho.
A speedometer does not directly measure vehicle speed. It’s nothing more than a tachometer for a wheel. The distance traveled for one revolution of that wheel (it’s circumference) is then taken into consideration to calibrate the display on the speedometer. Regardless of the size or circumference of the tire/wheel combination the speedometer will always reflect the same speed for the same number of revolutions per minute of the measured wheel. The true speed of the vehicle will, of course change, with different size wheels, but as I said, that isn’t what the speedometer is measuring.
Speedometer / tachometer readings, then, will always be the same, because they’re really just measuring the same thing at different points.
A poorly inflated tire will have a smaller circumference and therefore cause the vehicle to be traveling less distance per revolution, but its ANGULAR VELOCITY (RPMs) at the same engine speed would be the same as if the tire were correctly inflated. That’s all determined by the transmission, not tire circumference.
This assumes, of course that the wheel with the speedometer connected to it is also a drive wheel. If, like a motorcycle, the speedometer were connected to a front wheel and the drive connected to a rear wheel the relationship is subject to change with the change in one tire’s size.
Elly’s right about this one particular point. It had to happen sooner or later……
I need NOBODY to describe what FINAL DRIVE means…RPM’s plus engine FINAL drive will turn a driveshaft at X revs/min… THE CIRCUMFERENCE (KEY KEY KEY WORD) OF THE WHEEL/TIRE THEN DICTATES HOW FAR…the vehicle travels PER WHEEL REVOLUTION…SO the LARGER THE CIRCUMFERENCE OF THE WHEEL/TIRE OVERALL…WILL ABSOPOSOLUTELY…AFFECT THE VELOCITY OF THE VEHICLE at the same given RPM…I DONT CARE WHAT THE NOW CONFUSED SPEEDO SAYS
Elly continues to restate, and rethink, and try to redescribe a concept that I AM 100% SOLID ON…and then change his story, backpeddle etc…Ad NAUSEUM… .
Elly did you think When we were talking about 20 in wheels…we also gave you the decrease in sidewall in the tire? IF so… You do not understand the word CIRCUMFERENCE…
DO-NOT try to describe this mathmatecal certainty to me…and if you DO…GET IT RIGHT…theres NO second place prize IN MATH
*** ALSO *** You said…
“The wheel/tire diameter Will Not affect his reading on the speedemeter. You could put 20 inch wheels on the thing and the sppeedometer would read the same at 3K RPM (68.7) The car would be going faster than the speedometer is reading, tho.”
— ANSWER — CORRECT— But this is NOT what we were talking ABOUT…the wheel tire/diameter (Circumference) WILL not affect the speedometers CONFUSED AND AFFECTED READING (THE POINT)…but we were talking about Speedo ERROR…and the wheel tire diameters AFFECT…and as such it HAS AFFECTED it by making it WRONG in relation to the vehicles ACTUAL SPEED… WHy do you keep restating and changing…stay on PREMISE…please… This is the definition of having AFFECTED the SPeedo…
Blackbird
Please skip all the other side stuff and re-read what JayWB wrote [and what I added in brackets]:
"Regardless of the size or circumference of the tire/wheel combination the speedometer will always reflect the same speed for the same number of revolutions per minute of the measured wheel [or the engine in a particular gear]. The true speed of the vehicle will, of course change, with different size wheels, but as I said, that isn’t what the speedometer is measuring. "
Texases and Shadowfax are correct. Honda 4 cylinder engines are typically geared to run at 3000+ RPM at highway speeds. I had a 1999 CRX Si that Was geared to turn 3000 RPM at exactly 100 kilometers per hr (62 mph). I made many cross- country trips in it, driving 70+ mph all day for several days. I put over 170k miles on that engine, at least 100k of which were high-rpm highway miles, and when I sold it the engine ran like the day it was built, in part because I took good care of it.
…SO the LARGER THE CIRCUMFERENCE OF THE WHEEL/TIRE OVERALL…WILL ABSOPOSOLUTELY…AFFECT THE VELOCITY OF THE VEHICLE at the same given RPM…
Yes, yes, yes. I have always agreed with that. BuT it will not affect the speedometer reading.
JayWb and circuitsmith are correct. jesmed, Honda, and Texases, and Shadowfax are wrong.
a
nd what the hell does this mean …"…we also gave you the decrease in sidewall in the tire? IF so…"…
Here is what I have said from the beginning of this argument: The relationship between the tach and the speedometer, in any given gear, will not change regardless of low tires or smaller wheels.
I have also said that 3000 RPM is correct for 65-69 MPH.
I do understand circumference, it is Pi x Diameter. But it will not affect the speedometer reading.
Cicumference is 2R x pi.
Pi x r squared is area of a circle.
Yeah, you are probably right. are you sure it is 2R tho?
Pi times diameter = circumference. The radius is 1/2 the diameter so it’s 2 x pi x r.
B.L.E. You said it was 2r x Pi, and Pi x Diameter, which is correct ,and then you said it’s 2 x pi x r. isn’t that different??
I have been accused of saying one thing and then another. Also that I don’t know what I am talking about. Well here are some of my posts;; Wherein did I change my opinion??
EllyEllisJanuary 9Edit Report
Man, I don’t know anything about your car but 3000 rpm seems mighty high!
EllyEllisJanuary 10Edit Report
According to FoDaddy’s chart the thing should run 68.7 MPH at 3000 RPM, as Texases has said.
If you want to dsrive a 4 cylinder with a manual tranny, you must go ahead and enjoy it.
EllyEllisJanuary 10Edit Report
A few years ago I bought a new Dodge pickup, and it would run 70 MPH at 1750 RPMs. I thot it was a little too high geared tho.
EllyEllisJanuary 11Edit Report
There is a misconception that high RPMs don’t hurt an engine too. 3000 is not really high but it surely don’t help the engine
EllyEllisJanuary 11Edit Report
The OP said 65 at 3000 rpm. Isn’t that close enough
Crap, I’d drive it in 4th and keep the RPMs up to 6000, no amount of speed will harm the engine!
Right, Shadowfax??
chunkyazian11:04AMReport
" Rod, don’t forget that a slower cruising engine have parts inside that rub harder"
Who came up with that idiotic idea??
EllyEllisJanuary 12Edit Report
Speedo error maybe but low tire pressure would not change the ratio of the RPM to the speedo. I can’t believe that a guy as inteligent as you would think that low tires would cause the speedo to read differently.
3000 rpm is not very high but I would not drive that hard all day long.
Isn’t there someone on here that could tell Texases that he is wrong about the low tires?? Low tires will cause the actual speed to be lower than the speedo reading, but would not affect the reading between the Tach and the speedo.
EllyEllisJanuary 13Edit Report
"4mph on the tach is going to be barely noticeable, which means that it’s perfectly within reason that the OP would report 3krpm at the wrong speed reading."
Absolutely!!
I said before that 4 MPG is insignificant. I will say again that low tire pressure will not affect the speedometer reading. !0 inch tires would not affect the speedometer reading.
The OPs car is operating as intended!!
EllyEllisJanuary 13Edit Report
I mean just that. Tire size has no effect on the speedometer reading. It is related to the RpM of the engine and transmission, no the tires.
If tires are low or you have undersized tires, the car will not be going as fast as the speedo reads, but the speedo will match up with the RPM of the engine.The wheel/tire diameter Will Not affect his reading on the speedemeter. You could put 20 inch wheels on the thing and the sppeedometer would read the same at 3K RPM (68.7) The car would be going faster than the speedometer is reading, tho.
The wheel/tire diameter Will Not affect his reading on the speedemeter. You could put 20 inch wheels on the thing and the sppeedometer would read the same at 3K RPM (68.7) The car would be going faster than the speedometer is reading, tho.
EllyEllis11:26AMEdit Report
…SO the LARGER THE CIRCUMFERENCE OF THE WHEEL/TIRE OVERALL…WILL ABSOPOSOLUTELY…AFFECT THE VELOCITY OF THE VEHICLE at the same given RPM…
Yes, yes, yes. I have always agreed with that. BuT it will not affect the speedometer reading.
JayWb and circuitsmith are correct. jesmed, Honda, and Texases, and Shadowfax are wrong.
I do understand circumference, it is Pi x Diameter. But it will not affect the speedometer reading.
EllyEllis11:56AMEdit Report
Yeah, you are probably right. are you sure it is 2R tho?
EllyEllis1:16PMEdit Report
B.L.E. You said it was 2r x Pi, and Pi x Diameter, which is correct, and then you said it’s 2 x pi x r. isn’t that different??
Now i rest my case!!
Here are some quotes from sone other guys on here
Honda BlackbirdJanuary 11Report
3000+ at 65mph in a 6sp TSX…does sound rather high to me…in fact if I had to guess…I think you may be in FOURTH GEAR.
.Honda BlackbirdJanuary 11Report
Hmmm…then what gives here? Does the OP have different wheels? Low low profile tires? If its good for 69 at 3K… Speedo error?
Shadowfax
"As for the 65/69 discrepency, I’d say speedo error combined with low tire pressure is probably to blame."
shadowfaxJanuary 13Report
We’re talking about a 4mph difference. Speedo error and low tire pressure could easily explain a 4mph high reading on the speedo
shadowfaxJanuary 13Report
No, because you’re wrong again. Tire diameter does effect speedometer reading. You said so yourself, and then proceeded to argue with yourself again.
Honda BlackbirdJanuary 13Report
Elly Firstly…Shadowfax is VERY SHARP…he knows his mechanical “stuff” as we say…
Honda Blackbird9:09AMReport
I need NOBODY to describe what FINAL DRIVE means…RPM’s plus engine FINAL drive will turn a driveshaft at X revs/min… THE CIRCUMFERENCE (KEY KEY KEY WORD) OF THE WHEEL/TIRE THEN DICTATES HOW FAR…the vehicle travels PER WHEEL REVOLUTION…SO the LARGER THE CIRCUMFERENCE OF THE WHEEL/TIRE OVERALL…WILL ABSOPOSOLUTELY…AFFECT THE VELOCITY OF THE VEHICLE at the same given RPM…"
This isn’t what he said Jan 13 above.
NOW HE IS TALKING ABOUT THE VELOCITY OF THE VEHICLE, NOT THE SPEEDO READING, AS HE WAS BEFORE…Now he is talking out of the other side of his mouth! He is correct now.
The OPs car is doing just fine. It should run 3000 rpm at 68.7 mph, and if it isn’t, there might be a little error in the tach or the speedo, not enough to matter. I personally would not want to run it at 3000 rpm all day long, but that is just my way of pampering a car. I don’t turn corners on 2 wheels, and I don’t shift an automatic like it was a manual and I don’t drag race. I drive a 3.3 liter engine, who could I beat? (well I also have a 4/6 liter Lincoln)
The size of the tire or a low tire will not affect the speedometer. The speedometer might not be right tho if the tires are of a different size or are low. If a Speedometer is supposed to read 68.7 MPH at 3K RPM. low or smaller tires wont; change that!
Well this has been fun, all you old pros hang in there, you are right sometimes!!
LOL>…I think we all get it…we are just using different ways to say the same thing…or something…I can see you get it too…
Its an AFFECT…of the EFFECT I believe that we are talkin bout