I just realized something. Im going to buy 17" wheels soon and with the bigger size let alone the extra weight will it affect how the speed is being read on the speedometer? Will I have to reset my ecu or will it automatically reset itself somehow?

 

yes it will. If you really need to know your exact speed the apexi speed meter has a option on it to fix that.

 

Isn't it the tire size that will affect your speedo, not the actual wheel size?

 

as long as the overall diameter of the tire is the same, it will not noticeably affect your speedo. rim size does not matter.

just make sure you do the correct plus-size tire, and you'll be fine.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by philadd &raquo;</TD></TR><TR><TD CLASS="quote">as long as the overall diameter of the tire is the same, it will not noticeably affect your speedo. rim size does not matter.

</TD></TR></TABLE>

The diameter of the stock tire is smaller than the ones im getting. It would be 195 compared to 215 so its somewhat different.....

 

I have 19's on my accord wagon, and i had my cousin who is a Illinois State Trooper clock me and i was actually under the speedlimit that my tach was posting.
Be aware that the faster you go, that will change for some reason. He clocked me at 60, and i was at 65.

 

What's the stock tire size and new tire size? (full description, like: 195-70-15 to 215-45-17...)

the 195 is just width...

better yet, what year accord do you have? i can figure up what size tires wouldn't affect your speedo...

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by philadd &raquo;</TD></TR><TR><TD CLASS="quote">What's the stock tire size and new tire size? (full description, like: 195-70-15 to 215-45-17...)

the 195 is just width...

better yet, what year accord do you have? i can figure up what size tires wouldn't affect your speedo...</TD></TR></TABLE>

stock 195/60/15
new 215/40/17

Its a 94 accord....

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Jeff_Chicago &raquo;</TD></TR><TR><TD CLASS="quote">I have 19's on my accord wagon, and i had my cousin who is a Illinois State Trooper clock me and i was actually under the speedlimit that my tach was posting.
Be aware that the faster you go, that will change for some reason. He clocked me at 60, and i was at 65.
</TD></TR></TABLE>

Same with me and im only on 18's. The construction sites usually have that lil sign that tells you your speed and im always 5 mph off. I dont know if it can vary at different speeds or stay at a constant 5 over.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by hondaracin24 &raquo;</TD></TR><TR><TD CLASS="quote">

stock 195/60/15
new 215/40/17

Its a 94 accord....</TD></TR></TABLE>

205-40-17 is a little smaller, and your speedo will read a little faster than you are really going. my guess is that at highway speeds it could read between 5 and 10 mph off.

if you want to avoid this problem, i would say to go with a 215-45-17 tire. this is almost exactly the same overall diameter, and thus your speedo won't be off. the slightly thicker sidewall will also help soak up the bumps, cause trust me, 40 series tires can be rough...

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

Same with me and im only on 18's. The construction sites usually have that lil sign that tells you your speed and im always 5 mph off. I dont know if it can vary at different speeds or stay at a constant 5 over.</TD></TR></TABLE>

ya know... i've never found a radar (cop, or one of those speed read-outs on the side of the road) that's ever shown the same speed as my spedometer. and that's on both my stock rims and my 17s.

 

Okay, we need to restart this whole thing. There is so much crap in here.

Speedo accuracy is determined by OVERALL TIRE DIAMETER. This is the total distance from the bottom of the tire to the top of the tire when mounted on the wheel.

Of course your speedo accuracy will get worse the faster you go. It is a PERCENTAGE, not a set number. The higher the speed, the further off.

Here is how far off your speedo will be at 60 mph. Thanks to whalentire.com.

 

http://www.1010tires.com/TireSizeCalculator.asp

215/45-17 would be a closer fit, and is what is typically recommended when going from 195/60-15.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by phoenixitc &raquo;</TD></TR><TR><TD CLASS="quote">http://www.1010tires.com/TireSizeCalculator.asp

215/45-17 would be a closer fit, and is what is typically recommended when going from 195/60-15.</TD></TR></TABLE>

After looking at the link and h2290's link technically the speedometer would really be off only by a mph or 2. How is that possible when the overall diameter is larger?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by philadd &raquo;</TD></TR><TR><TD CLASS="quote">
if you want to avoid this problem, i would say to go with a 215-45-17 tire. this is almost exactly the same overall diameter, and thus your speedo won't be off. the slightly thicker sidewall will also help soak up the bumps, cause trust me, 40 series tires can be rough...
</TD></TR></TABLE>

what do mean that 40 series can be rough as opposed to 45. Is that much of a difference to change the performance of the car. I getting so many different opinions here its making it all the more confusing.........

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by hondaracin24 &raquo;</TD></TR><TR><TD CLASS="quote">

what do mean that 40 series can be rough as opposed to 45. Is that much of a difference to change the performance of the car. I getting so many different opinions here its making it all the more confusing......... </TD></TR></TABLE>

40s have a shorter sidewall height thus making it a little less flexible and thusly having a rougher (harsher) ride. Some people use the 45 series to have the taller sidewall to have a little more flex and bump absorption. If you look at tirerack.com you'll see that the recommended tire is a 45 but that doesn't mean you can't use the 40. Some people want the 40 for possibly better cornering. A lot depends on what you want with the ride characteristics.

 

A 45 series would be closer to your original tire diameter as stated before. Here is a how a speedo gets off:

Look at a very small go kart tire. For it to move 60 mph it would have to make a ton of rotations because each rotation only covers a small distance. Now a big tractor tire would make many less rotations to go 60 mph because it moves so far with every full rotation. Your speed is based on the number of tire rotations. So if you change the size of the tire the distance it covers with each rotation will be different than what the car thinks and cover more or less ground than what your speedo thinks it should. Result: Speedo is off.

Maybe someone can find a better explanation on the net but that is the best I can think of without getting too deep.

Also: The series of the tire is the height of the sidewall(distance from the inside part touching the wheel to the very outside part) as a percentage of the width. Theh first number is the width, say 205 mm. So a 50 series tire would have a 102.5 mm sidewall height (50%). A 40 series tire would be a bit smaller sidewall and a 60 series a bit taller. A 45 is taller than a 40 and therefore soaks up more bumps and also, in this application, matches your original overall tire diameter better.


Sorry for the long post guys.

 

I think I get what you mean now. Thanks for everyones help......