How fast was he really going?
Thread Starter
Le Mans Master
Joined: Mar 2002
Posts: 5,889
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From: Castro Valley Calif.
St. Jude Donor '03 thru '26
How fast was he really going?
I know a guy who met up with 30 or 40 of his Corvette buddies last nite, and on the way to the meeting point was running a clear stretch of freeway at an indicated 140 MPH. :eek: He swears he normally doesn't do this kinda thing, but it was a beautiful evening, he was running with a pack of 3 other cars, there was some great music playing and .......yada yada yada.............
Now my buddy tells me he knows he wasn't going that fast in reality, because he has 3.07s, and 315/35/17s on his A4 '87 Vert, and doesn't have a speedo gear correction yet. How can I figure out how fast this dumb schnizt was really going, so I can kick his azz? :lol:
Now my buddy tells me he knows he wasn't going that fast in reality, because he has 3.07s, and 315/35/17s on his A4 '87 Vert, and doesn't have a speedo gear correction yet. How can I figure out how fast this dumb schnizt was really going, so I can kick his azz? :lol:
Drifting
Joined: Apr 2003
Posts: 1,292
Likes: 2
Re: How fast was he really going? (Caboboy)
What gear and tyres is the speedo set up for? If it is a 2.59 gear, multiply the speed by 2.59 and divide the answer by 3.07.
140 x 2.59 / 3.07 = 118.
next the tyres. We need to know the height of the tyre the speedo thinks its got, and the height of the tyre you have actually got.
Height is proportional to circumference, which is how far the car travels each time the wheel goes round.
a 315/35 has a wall height of 110.25 mm, (35 per cent of 315)
Dunno what the original tyre was???, but this is the same as a 275/40, (40 per cent of 275 = 110), so maybe no correction required for the tyres.
(Oh, and I meant TIRE!!)
[Modified by britvette, 11:19 PM 6/22/2003]
140 x 2.59 / 3.07 = 118.
next the tyres. We need to know the height of the tyre the speedo thinks its got, and the height of the tyre you have actually got.
Height is proportional to circumference, which is how far the car travels each time the wheel goes round.
a 315/35 has a wall height of 110.25 mm, (35 per cent of 315)
Dunno what the original tyre was???, but this is the same as a 275/40, (40 per cent of 275 = 110), so maybe no correction required for the tyres.
(Oh, and I meant TIRE!!)
[Modified by britvette, 11:19 PM 6/22/2003]
