Speedometer
Thread Starter
Joined: Jan 2006
Posts: 25
Speedometer
Does anybody else think they have this? I believe that my speedometer is way off. When I'm going down the highway, I'll look to see that I'm doing between 75 & 80, yet I'm not flying by traffic and some peolpe still pass me.
I read an article in Car & Driver about a year ago about the manufacturers having a 2-5% error. Well 5% at 75 is only 4 MPH and I don't think I'm doing even 70.
Does anybody think that Ford might have calibrated all their Mustang speedos for the GT's 17" rims in a cost saving method to avoid a recalibration for the V6's 16 inchers?
I read an article in Car & Driver about a year ago about the manufacturers having a 2-5% error. Well 5% at 75 is only 4 MPH and I don't think I'm doing even 70.
Does anybody think that Ford might have calibrated all their Mustang speedos for the GT's 17" rims in a cost saving method to avoid a recalibration for the V6's 16 inchers?
2nd Gear Member
Joined: Feb 2006
Posts: 376
From:
RE: Speedometer
If it helps, i recently posted a question about switching from my stock 16" rims to stock 17" wheels. My question was will i have to get my speedometer re-calibrated. I had a few people reply that the outer diameter of the 17" tires used on the 17" wheels is actually the same as the outer diameter as the 16" tires. Even though the rims are bigger, the sidewall of the tires used is a lower profile making the outer diameter the same. So, in theory, this should not have any impact on the speedometer. hope that helps.
5th Gear Member
Joined: Sep 2005
Posts: 2,486
From:
RE: Speedometer
ORIGINAL: Moonbaby1973
If it helps, i recently posted a question about switching from my stock 16" rims to stock 17" wheels. My question was will i have to get my speedometer re-calibrated. I had a few people reply that the outer diameter of the 17" tires used on the 17" wheels is actually the same as the outer diameter as the 16" tires. Even though the rims are bigger, the sidewall of the tires used is a lower profile making the outer diameter the same. So, in theory, this should not have any impact on the speedometer. hope that helps.
If it helps, i recently posted a question about switching from my stock 16" rims to stock 17" wheels. My question was will i have to get my speedometer re-calibrated. I had a few people reply that the outer diameter of the 17" tires used on the 17" wheels is actually the same as the outer diameter as the 16" tires. Even though the rims are bigger, the sidewall of the tires used is a lower profile making the outer diameter the same. So, in theory, this should not have any impact on the speedometer. hope that helps.
1st Gear Member
Joined: Jan 2006
Posts: 54
From:
RE: Speedometer
"i can vouch for that... i got my 17" takeoffs from saleen, and when i was putting them on i decided to take a look- and they were the same height. Needless to say the take-off's were wider... and better looking, but same hieght=no speedo calibration."
Well I also bought the Saleen GT take off Bullitt rims and Pirellis, and after I took off the 16" stock BF Goodrich tires, I had to raise the car another 1" or so with the jack before I could put the 17" tires on the lug nuts. That makes the think the overall height with the 17" tires is indeed a bit taller
Well I also bought the Saleen GT take off Bullitt rims and Pirellis, and after I took off the 16" stock BF Goodrich tires, I had to raise the car another 1" or so with the jack before I could put the 17" tires on the lug nuts. That makes the think the overall height with the 17" tires is indeed a bit taller
5th Gear Member
Joined: Sep 2005
Posts: 2,486
From:
RE: Speedometer
ORIGINAL: StreetRod Steve
"i can vouch for that... i got my 17" takeoffs from saleen, and when i was putting them on i decided to take a look- and they were the same height. Needless to say the take-off's were wider... and better looking, but same hieght=no speedo calibration."
Well I also bought the Saleen GT take off Bullitt rims and Pirellis, and after I took off the 16" stock BF Goodrich tires, I had to raise the car another 1" or so with the jack before I could put the 17" tires on the lug nuts. That makes the think the overall height with the 17" tires is indeed a bit taller
"i can vouch for that... i got my 17" takeoffs from saleen, and when i was putting them on i decided to take a look- and they were the same height. Needless to say the take-off's were wider... and better looking, but same hieght=no speedo calibration."
Well I also bought the Saleen GT take off Bullitt rims and Pirellis, and after I took off the 16" stock BF Goodrich tires, I had to raise the car another 1" or so with the jack before I could put the 17" tires on the lug nuts. That makes the think the overall height with the 17" tires is indeed a bit taller
1st Gear Member
Joined: Dec 2005
Posts: 107
From:
RE: Speedometer
Hi,
The 16" (BF GOODRICH TRACTION T/A 215/65/16) dia is at 27" and the 17" ( Pireli P-Zero Nero tires size 235/55/17 ) is at 27.2" .
That means only 7/10 of 1% on circumference, meaning at 75 MPH stock, with the 17", you'll go at 75.5 MPH, peanuts.
If you want to find out tire comparaison, go to this site where you can compare your stock size versus any other, you'll find many valuable infos. Have fun
http://www.miata.net/garage/tirecalc.html
GTCS1
The 16" (BF GOODRICH TRACTION T/A 215/65/16) dia is at 27" and the 17" ( Pireli P-Zero Nero tires size 235/55/17 ) is at 27.2" .
That means only 7/10 of 1% on circumference, meaning at 75 MPH stock, with the 17", you'll go at 75.5 MPH, peanuts.
If you want to find out tire comparaison, go to this site where you can compare your stock size versus any other, you'll find many valuable infos. Have fun
http://www.miata.net/garage/tirecalc.html
GTCS1
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