CelicaQT

#1

Ok I need some info any of you guys/gals can give me. I just recently changed my tires bcus I wasn't getting any traction or handling on them during this winter season. Plus they were getting bald. I went from a 205/50R/15 to a 205/50R/15 and I read that your speedometer may be off?? SO I was wondering if anyone would know how to calculate how much I lost going to a lower radial?? Doing 80 on the freeway seems like i'm only going 70-75mph or doing 25-30mph doesn't seem like the actual speed either.

I got Yokos on them I was supposed to get Toyos ....long story....but regardless the handling and cornering on them is a lot smoother than my old worn out tires. Could it be that I'm just getting used to the new tires?

94TRDCeli

#2

dude you realise that you said you went from one tire to the exact same tire

CelicaQT

#3

Ohhhh oops..mah bad. I ment I had a 55R then went to a 50R. SOrry...i didn't realize it.

CelicaQT

#4

Ok well I think I mighta figured it out. I think the speedo differs when/if I'd be going to a bigger rim size. But since I'm still on 15's then maybe I'm just off by maybe 1 or 2.

3TST

#5

205x50x15 is the standard size so your speedo reading should be pretty accurate.
However, if you went for 205x55x15 then the speedo will be out but not by much. (sorry not sure how to calculate this).

95STCelica

#6

Speedometer reading : stock tire is 3.5% too slow..when your speedo reads 60 mph you are actually traveling 62.1

CelicaQT

#7

I found out that with the new tires on (50R's) that I'm going 3.29% Fast.
My friend told me to go to 7thgencivic.com and they had a Tire Size Calculator on their site.

going 60mph x 0.0329 = 1.974

So like 2 miles over...

Milds3vn

#8

Check this out to calculate any size changes... http://www.miata.net/garage/tirecalc.html

CelicaQT

#9

LOL ok I was told that also. Man seems like all of these tire calculators vary. It's hard to tell which is accurate.
Thanks for the link Mild. >>

95STCelica

#10

--Milds3vn+Feb 26, 2003 - 2:53 PM

QUOTE (Milds3vn @ Feb 26, 2003 - 2:53 PM)

Check this out to calculate any size changes... http://www.miata.net/garage/tirecalc.html

that's what i used

Neipas09

#11

Just set your cruise for 60.
When you hit a mile marker, start a stop watch.
In exactly 60secs your should pass the next marker.

If you don't then use D=T/V to figure your speed.
(i think that's the formula) >>

CelicaQT

#12

I don't have cruise...my ST didn't come with one! >>
Thanx for the info though...

95STCelica

#13

stupid ST's lol >>

Neipas09

#14

My ST came with it, so >> for me!

Zoom

#15

http://www.c5-corvette.com/tirecalc.htm

one more calculator;). I like because it also shows the odometer error, which is nice.

This post has been edited by Zoom: Mar 12, 2003 - 12:19 AM

CelicaQT

#16

I actually like that site better! It's got more info than the other sites I've gone to. Thanks Zoom. >>

SpedToe169

#17

Even with the stock size tires its still not very accurate. I've got GPS thats accurate to 0.1mph. Even with the stock size tires and wheels its about 4% off.

95STCelica

#18

That website made things a lot easier to understand, thanks >>

hioctane

#19

wow only 1.6% off with gts rims =)

Zoom

#20

SpedToe, with stock, is 4% off a high or low reading?

pflau

#21

yo if you really wanna find out for sure get someone with a GPS to sit in the car and check it for you. find a straight and level road.. go 60 using the cruise control.. and see what the GPS says..

my 205/55R15 is about half worn and my speedometer is dead on.

phil

presure2

#22

with the stock 15's on w/ 205/55's the spedo was right on its a mile or so off now with the 17's..

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Former Team 5SFTE pro member ;)13.6@108MPH, 5SFTE Powered