How fast am i going now?

[TypeRice]

Hey guys,

I recently got new rims for my ek.. 17" with 205/40 low profile tyres.

now that my rim is larger i feel my car is slightly slower in acceleration..
eg. i need to keep it in a lower gear for longer b4 i change etc...

ALso one other thing that worries me is.. am i actually going 60km/h when my speedometer points at 60km/h ??

thanks.

[SiReal]

yep .. my car slowed a fair bit when i went 15 to 17. heavier mass to get spinning.

good way to check is to borrow ur mates GPS device. roll at all the common speeds to get a guage of how much u r out.

for my car at 60 speedo, 60 GPS. 80 speedo, 78 GPS, 100speedo, 95GPS.

[wlee2]

Check out this thread.. theres a spreadsheet inthere download it and use it, put in your OEm tyre sizes and your new tyre sizes it should work it out for you

http://www.ozhonda.com/forum/showthread.php?p=556664#post556664

cheers

Wayne

[Limbo]

prob not. Your supose to get your speedo adjusted when you change the size of the rims & tyres but no-one ever does (correct me if you have!)

With larger rims yest acceleration is slower but once you get to a certain speed its pretty much the same. You can lower your tyre profile to get the same rolling diameter. Most tyre places will be able to tell you which size is closest.

The easiest way to check you speedo is if there is a speed checker in a school zone drive thru and see what it says and what your speedo says.
(Make sure you don't get fined!)
The less accurate way is do a constant speed and use the GPS it tells you how fast you are driving.

Then you will know how much roughly your out by

[TypeRice]

where can i get my speedo adjusted?
do mechanics do that ?

[aaronng]

Going from 185/60 R14 to 205/40 R17, you get a 3.12% increase in speedo reading. So that is not much difference. Rolling diameter is up by 18.2mm, so technically the cops can defect you if they felt like it.

[dsp26]

http://www.1010tires.com/tech.asp tells all.. should be a sticky.... kills the old miata site calculator plus its got offset calculator too as well as a guide of what tyres are available in what sizes and overall ratings :D

*cough sticky somehere please mod achoooo* :D:thumbsup:

[quang]

if you have an ek4 (15" 195/55), going to that size will put your speedo out by about 1-2% at each speed. i've cheked with a camera. its nothing too much to worry about. just means that at any speed you are not speeding (good thing). if you are going from another size like the 14" i'm not too sure unless the rolling diameters are the same acorss all eks.

[EK4R]

Larger tires means your speedo is running slower than stock so your could be actually doing 65 kph and your speedo is only reading 60kph so be sure to stay under the limit a bit or you could be over without knowing your true speed.



yep .. my car slowed a fair bit when i went 15 to 17.
for my car at 60 speedo, 60 GPS. 80 speedo, 78 GPS, 100speedo, 95GPS.

huh i am confused now.

claymore says bigger tyres your speedo should be slower. ie, at 100km/hr ur speedo reads 90

but Sireal is saying his bigger tyre made his speedo faster. ie, at 100km.hr your reads 105

[TypeRice]

i just gotta GPS and tested it around my streets so i didnt go excessive speeds.

60 speedo = 60 GPS
70 speedo = 65 GPS

I'll go out to the highway tomorow to test the higher speeds.

[Limbo]

huh i am confused now.

claymore says bigger tyres your speedo should be slower. ie, at 100km/hr ur speedo reads 90

but Sireal is saying his bigger tyre made his speedo faster. ie, at 100km.hr your reads 105


Yeah your speedo shows slower. i.e if your doing 100km in real speed, your speedo only shows 90km makes sense to me

Not sure where you get speedo adjusted just know that you are supose to and like arrong said they can defect your for it, but never heard of anyone getting yet

[EK4R]

Yeah your speedo shows slower. i.e if your doing 100km in real speed, your speedo only shows 90km makes sense to me


then why do sireal and type rice both say their's is showing more speed on their speedo compare to their actual speed on the GPS .

or did i misread