Recently I've encountered a few of those roadside radar operated speed indicators. I take these opportunities to try and verify my speedo. It appears to me that my speedo consistently reads about 4-mph too high.

Given that my observations are accurate, what would be the ideal tire size to correct this phenomenon?

 

Try this...

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

 

What tires are you using right now??

 

My stock tires were dead on, & even with the 235-45-17's I have now, it's still dead on compared to the road side speed radar units.

 

I'm on the original Michelins: HX MXM4 215-50 17

According to Tire Rack's site, these are the specs:

215/50VR17 93V XL 300 A A
1433lbs.
41psi
10/32nds
6-7.5"
7"
8.7"
NA
25.5"
819

That last number (819) is the revolutions per mile.

As I said earlier, the speedo seems to show 4-mph too fast. This is at low speed or higher speed. In other words, it isn't a percentage of true speed. Ergo, one must assume an average speed for computations. Lets assume a common highway speed of 50-mph. This would make an 8% error and one would look for a tire with about 754 rpm. This is unrealistic.

For instance, here is Bridgestone's Expedia:

255/45ZR17 SL 140 A A
1609lbs.
44psi
10/32nds
8.5-10"
9"
10.6"
9.7"
25.9"
820

Note that this tire is .4" larger diameter (and much wider) but has nearly identical rpm to the stock Michelins. This is very confusing.

Here is Dunlop's SP Sport 9000:

255/45ZR17 SL 280 A A
1653lbs.
51psi
10/32nds
NA
8.5"
10"
9.1"
26"
806

It's 26" diameter but has 806 rpm. This makes more sense.

It is also interesting to look at this Dunlop:

265/40ZR17 SL 280 A A
1565lbs.
51psi
10/32nds
9-10.5"
9.5"
10.7"
9"
25.4"
820

This one is almost identical to the stock tires but is much wider. Will it fit on the wheels and inside the fenders?

 

Of course there’s no guarantee that the RADAR device in those signs are better calibrated then the speedo in your car.
I don’t know if those things fall under the same scrutiny of the ones that are used by pigs to issue tickets.

Shawn S

 

i have verified that the CL-S with STOCK rims and tires runs about 3.5% fast and puts an extra 3.5% miles on your odometer....for example, if you drive an ACUTAL 1000 miles, your odometer says 1035...this fact has bothered me since day one as it will cause our warrenty to run out at an ACTUAL lower number....but what can we do?? put bigger tires on that essentially correct the problem but slow down the car....thats all we can do...or just live with the fact that its wrong...



by the way, this isnt euphoriaRSX, this is JIMCOL711 as im on my girlfreinds computer, sorry bout that, just didnt want you (SHAWN S) to think some newbie was trying to point anything out!! hehehe

 

First, why didn't you log in as yourself? Just curious...

Maybe your car is fast by 3.5%, but I don't think every CL-S produced is fast. I believe several members have gone out and tested their speedos against other cars speedos to verify. As Shawn said, the radar guns used to post speeds could be off. I doubt they're using high-tech guns to do something like this.

 

Over his GIRLFRIENDS house and he’s on ACL.COM,

Nothing better to do ???
What a Loser !!!

Shawn S

 

No lovin' for JimBob tonight!!! :P :pfawk:

 

And I think he’s purposely not replying to this so we think he's “gettin some”.

 

When the CLs a rockin', don't come a knockin'!

 

I remember reading an article about people getting screwd when they lease. it was with the current cl/tl/mdx's

 

My question would be, is there some way to recalibrate the speedometer?

Has anyone looked into this?

RUF

 

hahahahaha you guys crack me up, actually her and i live together and i posted that without realizing i was under her name, so i just edited it, hehehehe

 

oh, and yes, she does think im a loser when im on this friggin site all the time!!!! hahahaha