So I have 205/40/16's and my speedometer reads 83 when I'm going 75
This is in a stock 95 DX coupe. The only other thing I have changed that would affect this is I put in a cluster with a tach from an automatic (mine's a 5 spd)
I've read somewhere that 205/40/16s are less than 1% smaller than stock tires and I'm off by about 10%

Anyone have any ideas what it could be?

I searched but didn't see anything similar

TIA

 

Do you have indiglo gauges, or did you at one point? You could have messed up the needle.

 

it's gradually off, as in it's only off by 1-2 mph at 30 and gets worse from there so I don't see how the needle could be messed up. And no, I've never taken the needle off

 

How have you determined the speedo to be off? It sounds like it is just about right it not that far off

 

It's your wheels.........

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by instructor74 &raquo;</TD></TR><TR><TD CLASS="quote">How have you determined the speedo to be off? It sounds like it is just about right it not that far off </TD></TR></TABLE>
Yes, it's off! It was off like 4-5 mph when I was only going 45
I drove through a work zone with one of those radars that tell you how fast you're going. And the 75 was next to a car with a good speedo.
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by rniederlando &raquo;</TD></TR><TR><TD CLASS="quote">It's your wheels.........</TD></TR></TABLE>
What do you mean? Are 205/40/16 really 10% smaller than stock tires?

 

were the stock eg wheels 14's? the wheels would be my logical guess, but I'm also not sure how much larger the diameter of the wheel/tire is than stock. Just a thought

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by rniederlando &raquo;</TD></TR><TR><TD CLASS="quote">were the stock eg wheels 14's? the wheels would be my logical guess, but I'm also not sure how much larger the diameter of the wheel/tire is than stock. Just a thought</TD></TR></TABLE>

I thought that too but according to tire calculators the difference is .849%
That's why I'm confused

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote &raquo;</TD></TR><TR><TD CLASS="quote">
Actual Speed: 60 mph 100 km/h
Speedometer1: 60.5 mph 100. km/h

Speedometer Difference: - Speedometer Difference: 0.849% too fast
Diameter Difference: - Diameter Difference: 0.84%
</TD></TR></TABLE>

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by rniederlando &raquo;</TD></TR><TR><TD CLASS="quote">It's your wheels.........</TD></TR></TABLE>

honda calibrates the speedo to read slightly higher. you'll be going 78, speedo says 81. It's not this exact difference, however honda calibrates it this way so that they're are no discrepanincies (spelling owns me) when adhering to the speed limit. When upsizing to a 205/50/15 it's a 23.07" diameter compared to the stock ~22.7" diameter. This usually makes the speedo dead on. However when downsizing to your 22.46" diameter tire, it is going to amplify the stock difference.

If you'd like, whenever you get tires next you could run a 215/40/16 (if that size is available. This diameter is 22.77" which is very close to stock

 

It's definately your wheel size that's throwing your speedo off, that's why teh numbers get progressively larger as you go faster, at lower speeds the same ammount of rotations / minute of the wheels are closer together, but as you speed up the # of rotations / minute with each of those tire sizes being different gets wider and wider and wider as more and more ground is gained by the larger tires.

When you get up to 100mph you'll be WAY outta whack, and 120 (if your car can do it), so n and so forth.

This shouldn't even be a topic... - guarantee if you slap 14" steelies on their with a stock sidewall I do believe it'll be 100% accurate again (or as 100% as a honda speedo could be).

Don't forget the middle # is not a set number, it's a percentage of the width (the first number). So 205/40's aren't the same as 215/40's in either terms of width or sidewall size

 

Thanks, guys

I guess I'll buy different size tires next time

Would I be better off with 215/40/16 like Bense said or 205/45/16

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by wheelmanbg &raquo;</TD></TR><TR><TD CLASS="quote">Thanks, guys

I guess I'll buy different size tires next time

Would I be better off with 215/40/16 like Bense said or 205/45/16</TD></TR></TABLE>

205/45/16 is 23.26" 225/40/16 is 23.09" might wanna go with 225/40/16 for deal on accuracy if it will fit.

EDIT: I just checked tire rack, the only 225/40/16s that are available are competition tires. 215/40/16 is available in a few tires, as well as 205/45/16. I would go with 215/40/16 if i were you.

Which makes me think about going to 16s instead of 15s because there are more low profile tires available. 215/40/16 is 22.77" might be a good gearing advantage than 215/50/15s. hmmm

 

http://www.miata.net/garage/tirecalc.html

At the very bottom of the page it will show what percentage of error you have

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Bense &raquo;</TD></TR><TR><TD CLASS="quote">

205/45/16 is 23.26" 225/40/16 is 23.09" might wanna go with 225/40/16 for deal on accuracy if it will fit.

EDIT: I just checked tire rack, the only 225/40/16s that are available are competition tires. 215/40/16 is available in a few tires, as well as 205/45/16. I would go with 215/40/16 if i were you.

Which makes me think about going to 16s instead of 15s because there are more low profile tires available. 215/40/16 is 22.77" might be a good gearing advantage than 215/50/15s. hmmm</TD></TR></TABLE>

Thanks Bense You da man

Next time I buy tires I'll see if I can get 215/40/16s

 

i have a similar problem, so i'll post.

i'm about 5mph too fast (according to the radar things i drive by) my car is a 96 cx hatch with Fit steelies (From base fit, i believe 15") i have no idea what stock should have been for EK so u think this is why i'm a tad off?

 

oh and a bit to add, i changed gauge faces (stock to Si) so messing with the needle prob set it off a bit, i'm going to readjust and i hope it fixes the problem!