Toy Civic

I am posting this thread for those "junior" or "younger" folks who are new to Hondas and Acuras. This may even apply to the pros out there who may be unaware of this issue. If you are already aware of this then disregard. I've been meaning to write this for a long time, but just haven't yet..........till now.

I have owned my 1995 Civic EX coupe with manual tranny since it was new. I soon discovered that my speedo was off by 10%. At the time I had the original tire size of 185/60/14. I discovered this problem on a long road trip. I was going 70mph, but other cars including highway patrolmen were flying right by me. So I slowed down to 60mph and timed myself between mile markers........1 minute 8 seconds. With an accurate speedo, the time should only be 1 minute. That meant that the speedo was reading faster than the actual vehicle speed. So I took it to my Honda dealer and demanded a fix. Their solution was to replace the speedo cluster. That did nothing. Their explanation to me was that Hondas "allowable" tolerance is plus or minus 10%. I took the car to a speedo calibration shop with dynamometer. It was confirmed that my speedo was reading 10% faster than the actual speeds from 20mph all the way to 80mph. So I then concluded a few issues with an inaccurate speedo:

1) If the speedo and odometer run off the same sensor (which I much later came to understand the vehicle speed sensor system in the tranny), then maybe the odometer is also off by 10%.

2) If the odometer is racking up miles faster, then warranty periods will expire earlier

3) When auto publications post performance data, that the 0-60 acceleration times may not be accurate........if they are going off the cars speedo only, and not some other measuring device.

4) The only upside to this is that one will be much less likely to get a speeding ticket. For years I ended up mentally compensating for the inaccurate speedo while driving. I did this till I upgraded my tire size about 6 years ago.

So the moral of the story is that one should seriously consider having their speedo accuracy checked at any speedo calibration shop with dyno. It is very likely that all 92-00 Civics and 94-01 Integras will also have this inaccuracy, especially with the original tire sizes with 14 or 15 inch rims, which many of the die hard Honda and Acura gurus stick with. The vehicle speed sensors in all these cars are designed the very same. The only difference I can see that could change things is the final drive in the tranny. All the Civics/Del Sols with any D series motor and tranny and all non-GSR Integras came with the 4.266 final drive gear or less. All the DOHC B series VTEC motors in Civics and Integras came with the 4.4 final drive gear, except for the JDM cars with the 4.78 final drive gear. If you know anything about these trannies, then you know that the little gear attached to the vehicle speed sensor spins off of a small ring gear that is pressed onto the differential.

There are only three solutions to adjust for the speedo inaccuracy:

1) Change the differential speedo ring gear to one with a smaller ratio to spin the VSS gear faster. Chances are that there is no part out there that will accomplish this. If there was, most aren't willing to tear apart the tranny.

2) Change the VSS gear to a smaller one so it will spin faster. Again, chances are that there is no part out there that will accomplish this. If there was, then changing this would be much easier since the VSS will come off the tranny easily without having to pull the tranny.

3) The easiest solution, which many have done anyway, is to change your tire size. I am using Toyo Proxes 4 205/40/17 tires. The overall rolling diameter is 23.5 inches. I now have a GSR motor with a hybrid Type R/LS manual tranny. The 5th gear and 4.266 final drive gear is Integra LS, while 1st through 4th gears are Type R. With this combo, my speedo accuracy is DEAD ON.

I know nothing about earlier Preludes, earlier Accords, earlier other Honda/Acura cars, or the current 2002 and newer Hondas and Acuras. Again, I'm only talking about 92-00 Civics and 94-01 Integras, which comprise a huge chunk of the Honda/Acura market. But if you have one of these other Honda/Acura models, then it is worth $20-$30 to get your speedo checked.

Again, smaller tire diameters will cause the speedo to read faster than actual speed, and bigger tire diameters will cause the speedo to read slower than actual speed. Since most cars have fixed ratio speed sensors built into the trannies and fuel injection systems, that there is little chance to correct any inaccuracy with replacement parts. You can only do that with older cars using non-electric cable type speedo drive systems.

A-series

Good job on the write up man. Nice to know it's not just a manufacturing error on a smaller # of hondas.
My '92 Civic EX speedo is off by about 4mph, with standard tire size. I realized this as I was passing one of those small "This is your speed" radar displays that are sometimes put up by speed limit signs in my area. I used to drive an '86 Accord LX that was off by 5mph with correct tire size, though badly worn.
I've noticed this problem on several other makes of cars though, either by driving them myself or from talking to their drivers. I used to think it was just something that tended to show up with age and that most new cars were spot on, with the occasional exception. My mom's Cougar was off by 3mph before it was even broken in. The speedo is off but the digital display is correct.

ahkeen

Wow after reading this i borrowed my friends GPS system which can tell u how fast u are going and my speed is just off by 3-5 mph, but im going to be putting back on my 17's back on my car after the winter. O btw toy civic how u like the toyo proxes 4 on ur car? i currently have falken ze512 and the road noise is horrible, i was thinking the proxes 4 will be better.

audie

Using a GPS my EK speedo indicates 4-5 mph (7% high) faster than actual speed at 70 mph (70 indicated is really 65) and is proportionaly more or less depending on speed. Must be why people were always passing me and I seldom got a ticket. However, the odometer reads about 1% low.

ahkeen

so the only way to correct this issue is changing ur tire size? cuz i have a automatic and im not sure how or where to change this final drive gear ratio. im planning on changing the size from 13's (stock) to 15's

Musicman

All 4 of my hondas are off, the 86 Crx is the most accurate but my 91 Crx, 94 Del sol and 98 Civic Ex, as well as my 92 Si hatchback were all off 4-6 mph. Tire size is the easiest fix.

CivicSiRacer

Your speedo should be off by a little. It is better that you are showing 70mph and actually going 65mph. While I could not read the original post since it's black on black.

Imagine you were going 70mph and you were actually going 75mph? You would or could always get a ticket for speeding.

Also as the seasons change your air pressures change your speedo reading and odomoeter since temperature changes the expansion or contraction.

When I had my odometer reset when I purchased a new one my friend who works at an odometer shop says they get the odometer reading within 1000-5000 miles since that is the error of change between seasons.

Now of course we are anal about all that and will check our air pressures reguarlly.

ahkeen

our honda speedo is deceiving us making us think we can keep up with other big players and then we can brag about how fast our lil hondas can go.

audie

On Hondas/Acuras the speedometer gear drives off of the differential housing which turns the same rpm as the tires. Final drive ratio makes no difference in this case. There are adjustable devices (speedohealer.com for example) available that will allow you correct your speedometer up or down by modifying the output of the vehicle speed sensor. This is fine if your odometer and speedometer of off by the same percentage otherwise your have to chose which one you most want to be correct. In my experience digital speedos are much more accurate and consistent (but I hate digital gages) than swing needle types yet none are perfect and anyone who expects them to be has lost touch with reality. Wait until you find out about tachometer lag.

ahkeen

lol tachmeter lag? wow! well my new rims + tires should be in next week, they are 15in 5zigen with falkens and i will see if the plus 2 size will make any difference from my 13in stock. i'll keep u guys posted and see if it is off only by 2-5 mph, or exactly the same.