New Gear Calculator
Thread Starter
Race Director
Joined: Dec 2006
Posts: 12,393
Likes: 2,911
From: Fort Worth, Texas
You have more sidewall and speed, so can only speculate that it's off from tire growth...how much are we talking? Was the old calculator correct or which one do you use?
Race Director
Joined: Mar 2005
Posts: 11,549
Likes: 27
From: Southampton NJ
I wouldn't recommend shifting to 4th on the juice either, no matter how good the efficiency of a converter as everyone is going to have some. It's like prop slip on a boat if you do any fishing, my other hobby
That calculation is an indication of yours like I said w/o taking into account of tire growth which shouldn't be more than an inch overall at that speed on a radial with only 4.25" of sidewall IMO, but should remember the last 66' is an average mph for the trap speed so you'll actually going slightly faster when crossing the stripe at the end than what prints out on the slip. I like to think the small amount of tire growth offsets that.
That calculation is an indication of yours like I said w/o taking into account of tire growth which shouldn't be more than an inch overall at that speed on a radial with only 4.25" of sidewall IMO, but should remember the last 66' is an average mph for the trap speed so you'll actually going slightly faster when crossing the stripe at the end than what prints out on the slip. I like to think the small amount of tire growth offsets that.
Melting Slicks
Joined: Nov 2009
Posts: 2,536
Likes: 15
Using the "rounded" numbers you supplied. Looks like your converter is slipping 9% at the stripe (Unless you would like to debate the accuracy of the converter calculator also).
Which would make the gear/rpm calc off a little. But of course you know this and are just sitting back enjoying me jumping through hoops....
Which would make the gear/rpm calc off a little. But of course you know this and are just sitting back enjoying me jumping through hoops....
Race Director
Joined: Mar 2005
Posts: 11,549
Likes: 27
From: Southampton NJ
Using the "rounded" numbers you supplied. Looks like your converter is slipping 9% at the stripe (Unless you would like to debate the accuracy of the converter calculator also).
Which would make the gear/rpm calc off a little. But of course you know this and are just sitting back enjoying me jumping through hoops....
Which would make the gear/rpm calc off a little. But of course you know this and are just sitting back enjoying me jumping through hoops....
Thread Starter
Race Director
Joined: Dec 2006
Posts: 12,393
Likes: 2,911
From: Fort Worth, Texas
The latter, here's a calculator for it if interested.
http://www.mercuryracing.com/prop-slip-calculator/
Ventilation is commonly mistaken for cavitation which is what allows the prop to slip into its powerband like a stall converter in a car, hope that helps.
http://www.mercuryracing.com/prop-slip-calculator/
Ventilation is commonly mistaken for cavitation which is what allows the prop to slip into its powerband like a stall converter in a car, hope that helps.
Le Mans Master
Joined: Nov 2005
Posts: 7,060
Likes: 366
From: Kendall Park NJ
No, their calculator has my tires shrinking. It's off by a couple hundred rpm. I never used their old one. I just used one that I designed.
Le Mans Master
Joined: Nov 2005
Posts: 7,060
Likes: 366
From: Kendall Park NJ
I really did not want to go through the effort it would take to input all of the parameters. format the results to show the differences and then post them. They can determine why their calculator is incorrect.
Thread Starter
Race Director
Joined: Dec 2006
Posts: 12,393
Likes: 2,911
From: Fort Worth, Texas
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Le Mans Master
Joined: Nov 2005
Posts: 7,060
Likes: 366
From: Kendall Park NJ
If numbers are being rounded or truncated, then the results are grossly wrong.
Last edited by GARY2004Z06; Apr 14, 2015 at 07:34 AM.
Thread Starter
Race Director
Joined: Dec 2006
Posts: 12,393
Likes: 2,911
From: Fort Worth, Texas
There shouldn't be any slippage of the trans with a manual lol, the slippage is an option for those with an auto. There will always be some rounding going on, again I ask how much exactly does yours differ? Help a brotha out, you're normally not so vague...
Le Mans Master
Joined: Nov 2005
Posts: 7,060
Likes: 366
From: Kendall Park NJ
Trans Gear Ratio (1st) 2.66
Trans Gear Ratio (2nd) 1.78
Trans Gear Ratio (3rd) 1.30
Trans Gear Ratio (4th) 1.00
Shift RPM 8000
Trap Speed 148.00
Tire Height 27.0
Max Speed (1st Gear) 58.92
Initial RPM (2nd Gear) 5353
Max Speed (2nd Gear) 88.05
Initial RPM (3rd Gear) 5843
Max Speed (3rd Gear) 120.56
Initial RPM (4th Gear) 6154
RPM @ Trap Speed 7554
Here are the answers, now go plug them in and see what comes out.
Thread Starter
Race Director
Joined: Dec 2006
Posts: 12,393
Likes: 2,911
From: Fort Worth, Texas
Rear Gear Ratio 4.10
Trans Gear Ratio (1st) 2.66
Trans Gear Ratio (2nd) 1.78
Trans Gear Ratio (3rd) 1.30
Trans Gear Ratio (4th) 1.00
Shift RPM 8000
Trap Speed 148.00
Tire Height 27.0
Max Speed (1st Gear) 58.92
Initial RPM (2nd Gear) 5353
Max Speed (2nd Gear) 88.05
Initial RPM (3rd Gear) 5843
Max Speed (3rd Gear) 120.56
Initial RPM (4th Gear) 6154
RPM @ Trap Speed 7554
Here are the answers, now go plug them in and see what comes out.
Trans Gear Ratio (1st) 2.66
Trans Gear Ratio (2nd) 1.78
Trans Gear Ratio (3rd) 1.30
Trans Gear Ratio (4th) 1.00
Shift RPM 8000
Trap Speed 148.00
Tire Height 27.0
Max Speed (1st Gear) 58.92
Initial RPM (2nd Gear) 5353
Max Speed (2nd Gear) 88.05
Initial RPM (3rd Gear) 5843
Max Speed (3rd Gear) 120.56
Initial RPM (4th Gear) 6154
RPM @ Trap Speed 7554
Here are the answers, now go plug them in and see what comes out.
Gear 1 Max Speed - 57 MPH at 8000 RPM
Shifting at 8000 RPM puts you at 5300 RPM in Gear 2
Gear 2 Max Speed - 85 MPH at 8000 RPM
Shifting at 8000 RPM puts you at 5800 RPM in Gear 3
Gear 3 Max Speed - 117 MPH at 8000 RPM
Shifting at 8000 RPM puts you at 6200 RPM in Gear 4
Gear 4 Max Speed - 148 MPH at 7500 RPM
If the tire grows .5" from center (1" overall diameter) from centrifugal force, then the numbers look pretty close to your data...
Gear 1 Max Speed - 59 MPH at 8000 RPM
Shifting at 8000 RPM puts you at 5300 RPM in Gear 2
Gear 2 Max Speed - 89 MPH at 8000 RPM
Shifting at 8000 RPM puts you at 5900 RPM in Gear 3
Gear 3 Max Speed - 121 MPH at 8000 RPM
Shifting at 8000 RPM puts you at 6100 RPM in Gear 4
Gear 4 Max Speed - 148 MPH at 7600 RPM
Either way both are within differences of rounding up or down to nearest whole value on both mph and rpm, is your tire exactly 27.00" in diameter?
Le Mans Master
Joined: Nov 2005
Posts: 7,060
Likes: 366
From: Kendall Park NJ
Below is with a 27" tire, but how much does it grow? Something the calculator admittedly doesn't take into account as there are too many variables ie sidewall size/bias or radial
Gear 1 Max Speed - 57 MPH at 8000 RPM
Shifting at 8000 RPM puts you at 5300 RPM in Gear 2
Gear 2 Max Speed - 85 MPH at 8000 RPM
Shifting at 8000 RPM puts you at 5800 RPM in Gear 3
Gear 3 Max Speed - 117 MPH at 8000 RPM
Shifting at 8000 RPM puts you at 6200 RPM in Gear 4
Gear 4 Max Speed - 148 MPH at 7500 RPM
If the tire grows .5" from center (1" overall diameter) from centrifugal force, then the numbers look pretty close to your data...
Gear 1 Max Speed - 59 MPH at 8000 RPM
Shifting at 8000 RPM puts you at 5300 RPM in Gear 2
Gear 2 Max Speed - 89 MPH at 8000 RPM
Shifting at 8000 RPM puts you at 5900 RPM in Gear 3
Gear 3 Max Speed - 121 MPH at 8000 RPM
Shifting at 8000 RPM puts you at 6100 RPM in Gear 4
Gear 4 Max Speed - 148 MPH at 7600 RPM
Either way both are within differences of rounding up or down to nearest whole value on both mph and rpm, is your tire exactly 27.00" in diameter?
Gear 1 Max Speed - 57 MPH at 8000 RPM
Shifting at 8000 RPM puts you at 5300 RPM in Gear 2
Gear 2 Max Speed - 85 MPH at 8000 RPM
Shifting at 8000 RPM puts you at 5800 RPM in Gear 3
Gear 3 Max Speed - 117 MPH at 8000 RPM
Shifting at 8000 RPM puts you at 6200 RPM in Gear 4
Gear 4 Max Speed - 148 MPH at 7500 RPM
If the tire grows .5" from center (1" overall diameter) from centrifugal force, then the numbers look pretty close to your data...
Gear 1 Max Speed - 59 MPH at 8000 RPM
Shifting at 8000 RPM puts you at 5300 RPM in Gear 2
Gear 2 Max Speed - 89 MPH at 8000 RPM
Shifting at 8000 RPM puts you at 5900 RPM in Gear 3
Gear 3 Max Speed - 121 MPH at 8000 RPM
Shifting at 8000 RPM puts you at 6100 RPM in Gear 4
Gear 4 Max Speed - 148 MPH at 7600 RPM
Either way both are within differences of rounding up or down to nearest whole value on both mph and rpm, is your tire exactly 27.00" in diameter?
Here's a Wallace Racing Calculator.
Calculate RPM for given MPH, Rear Gear Ratio and Trans Gear Ratio
Enter MPH: 148
Enter Tire Diameter: 27"
Enter Rear Gear Ratio: 4.10:1
Enter Trans Gear Ratio: 1.00:1
Result -- 7,551 rpm
Here's another one from TCI.
Enter MPH, The Tire Height in Inches, The Rearend Ratio, Trans Ratio, & Converter Slip %
RPM = (Rearend Ratio * MPH * 336.136 * Trans Ratio * (1 + (Conv Slip% / 100))) / Tire Height
MPH 148
Tire Height 27
Rearend Ratio 4.10
Trans Ratio 1.00
Conv Slip 0%
RPM = 7554.345
Here's their calculator.
Quick Facts
Gear 1 Max Speed - 57 MPH at 8000 RPM
Shifting at 8000 RPM puts you at 5300 RPM in Gear 2
Gear 2 Max Speed - 85 MPH at 8000 RPM
Shifting at 8000 RPM puts you at 5800 RPM in Gear 3
Gear 3 Max Speed - 117 MPH at 8000 RPM
Shifting at 8000 RPM puts you at 6200 RPM in Gear 4
Gear 4 Max Speed - 152 MPH at 8000 RPM
Shifting at 8000 RPM puts you at 5900 RPM in Gear 5
Gear 5 Max Speed - 205 MPH at 8000 RPM
Shifting at 8000 RPM puts you at 5400 RPM in Gear 6
Gear 6 Max Speed - 304 MPH at 8000 RPM
Cruising RPM at 70MPH in Gear 6 is 1800
Gear 1
700
5
800
6
900
6
1000
7
1100
8
1200
9
1300
9
1400
10
1500
11
1600
11
1700
12
1800
13
1900
14
2000
14
2100
15
2200
16
2300
16
2400
17
2500
18
2600
19
2700
19
2800
20
2900
21
3000
21
3100
22
3200
23
3300
24
3400
24
3500
25
3600
26
3700
26
3800
27
3900
28
4000
29
4100
29
4200
30
4300
31
4400
31
4500
32
4600
33
4700
34
4800
34
4900
35
5000
36
5100
36
5200
37
5300
38
5400
39
5500
39
5600
40
5700
41
5800
41
5900
42
6000
43
6100
44
6200
44
6300
45
6400
46
6500
46
6600
47
6700
48
6800
49
6900
49
7000
50
7100
51
7200
51
7300
52
7400
53
7500
54
7600
54
7700
55
7800
56
7900
56
8000
57
Gear 2
700
7
800
9
900
10
1000
11
1100
12
1200
13
1300
14
1400
15
1500
16
1600
17
1700
18
1800
19
1900
20
2000
21
2100
22
2200
23
2300
25
2400
26
2500
27
2600
28
2700
29
2800
30
2900
31
3000
32
3100
33
3200
34
3300
35
3400
36
3500
37
3600
38
3700
40
3800
41
3900
42
4000
43
4100
44
4200
45
4300
46
4400
47
4500
48
4600
49
4700
50
4800
51
4900
52
5000
53
5100
54
5200
56
5300
57
5400
58
5500
59
5600
60
5700
61
5800
62
5900
63
6000
64
6100
65
6200
66
6300
67
6400
68
6500
69
6600
70
6700
72
6800
73
6900
74
7000
75
7100
76
7200
77
7300
78
7400
79
7500
80
7600
81
7700
82
7800
83
7900
84
8000
85
Gear 3
700
10
800
12
900
13
1000
15
1100
16
1200
18
1300
19
1400
20
1500
22
1600
23
1700
25
1800
26
1900
28
2000
29
2100
31
2200
32
2300
34
2400
35
2500
37
2600
38
2700
39
2800
41
2900
42
3000
44
3100
45
3200
47
3300
48
3400
50
3500
51
3600
53
3700
54
3800
56
3900
57
4000
58
4100
60
4200
61
4300
63
4400
64
4500
66
4600
67
4700
69
4800
70
4900
72
5000
73
5100
75
5200
76
5300
77
5400
79
5500
80
5600
82
5700
83
5800
85
5900
86
6000
88
6100
89
6200
91
6300
92
6400
94
6500
95
6600
96
6700
98
6800
99
6900
101
7000
102
7100
104
7200
105
7300
107
7400
108
7500
110
7600
111
7700
113
7800
114
7900
115
8000
117
Gear 4
700
13
800
15
900
17
1000
19
1100
21
1200
23
1300
25
1400
27
1500
29
1600
30
1700
32
1800
34
1900
36
2000
38
2100
40
2200
42
2300
44
2400
46
2500
48
2600
49
2700
51
2800
53
2900
55
3000
57
3100
59
3200
61
3300
63
3400
65
3500
67
3600
68
3700
70
3800
72
3900
74
4000
76
4100
78
4200
80
4300
82
4400
84
4500
86
4600
87
4700
89
4800
91
4900
93
5000
95
5100
97
5200
99
5300
101
5400
103
5500
105
5600
106
5700
108
5800
110
5900
112
6000
114
6100
116
6200
118
6300
120
6400
122
6500
124
6600
125
6700
127
6800
129
6900
131
7000
133
7100
135
7200
137
7300
139
7400
141
7500
143
7600
144
7700
146
7800
148
Last edited by GARY2004Z06; Apr 15, 2015 at 07:07 AM.
Race Director
Joined: Mar 2005
Posts: 11,549
Likes: 27
From: Southampton NJ
They show 7800 rpm (not 7500) for 148 mph with a 27" tire. 246 rpm is a substantial difference. My calculator does not assume growth either. How many times must I say that they are WRONG?
Here's a Wallace Racing Calculator.
Calculate RPM for given MPH, Rear Gear Ratio and Trans Gear Ratio
Enter MPH: 148
Enter Tire Diameter: 27"
Enter Rear Gear Ratio: 4.10:1
Enter Trans Gear Ratio: 1.00:1
Result -- 7,551 rpm
Here's another one from TCI.
Enter MPH, The Tire Height in Inches, The Rearend Ratio, Trans Ratio, & Converter Slip %
RPM = (Rearend Ratio * MPH * 336.136 * Trans Ratio * (1 + (Conv Slip% / 100))) / Tire Height
MPH 148
Tire Height 27
Rearend Ratio 4.10
Trans Ratio 1.00
Conv Slip 0%
RPM = 7554.345
Here's their calculator.
Quick Facts
Gear 1 Max Speed - 57 MPH at 8000 RPM
Shifting at 8000 RPM puts you at 5300 RPM in Gear 2
Gear 2 Max Speed - 85 MPH at 8000 RPM
Shifting at 8000 RPM puts you at 5800 RPM in Gear 3
Gear 3 Max Speed - 117 MPH at 8000 RPM
Shifting at 8000 RPM puts you at 6200 RPM in Gear 4
Gear 4 Max Speed - 152 MPH at 8000 RPM
Shifting at 8000 RPM puts you at 5900 RPM in Gear 5
Gear 5 Max Speed - 205 MPH at 8000 RPM
Shifting at 8000 RPM puts you at 5400 RPM in Gear 6
Gear 6 Max Speed - 304 MPH at 8000 RPM
Cruising RPM at 70MPH in Gear 6 is 1800
Gear 1
700
5
800
6
900
6
1000
7
1100
8
1200
9
1300
9
1400
10
1500
11
1600
11
1700
12
1800
13
1900
14
2000
14
2100
15
2200
16
2300
16
2400
17
2500
18
2600
19
2700
19
2800
20
2900
21
3000
21
3100
22
3200
23
3300
24
3400
24
3500
25
3600
26
3700
26
3800
27
3900
28
4000
29
4100
29
4200
30
4300
31
4400
31
4500
32
4600
33
4700
34
4800
34
4900
35
5000
36
5100
36
5200
37
5300
38
5400
39
5500
39
5600
40
5700
41
5800
41
5900
42
6000
43
6100
44
6200
44
6300
45
6400
46
6500
46
6600
47
6700
48
6800
49
6900
49
7000
50
7100
51
7200
51
7300
52
7400
53
7500
54
7600
54
7700
55
7800
56
7900
56
8000
57
Gear 2
700
7
800
9
900
10
1000
11
1100
12
1200
13
1300
14
1400
15
1500
16
1600
17
1700
18
1800
19
1900
20
2000
21
2100
22
2200
23
2300
25
2400
26
2500
27
2600
28
2700
29
2800
30
2900
31
3000
32
3100
33
3200
34
3300
35
3400
36
3500
37
3600
38
3700
40
3800
41
3900
42
4000
43
4100
44
4200
45
4300
46
4400
47
4500
48
4600
49
4700
50
4800
51
4900
52
5000
53
5100
54
5200
56
5300
57
5400
58
5500
59
5600
60
5700
61
5800
62
5900
63
6000
64
6100
65
6200
66
6300
67
6400
68
6500
69
6600
70
6700
72
6800
73
6900
74
7000
75
7100
76
7200
77
7300
78
7400
79
7500
80
7600
81
7700
82
7800
83
7900
84
8000
85
Gear 3
700
10
800
12
900
13
1000
15
1100
16
1200
18
1300
19
1400
20
1500
22
1600
23
1700
25
1800
26
1900
28
2000
29
2100
31
2200
32
2300
34
2400
35
2500
37
2600
38
2700
39
2800
41
2900
42
3000
44
3100
45
3200
47
3300
48
3400
50
3500
51
3600
53
3700
54
3800
56
3900
57
4000
58
4100
60
4200
61
4300
63
4400
64
4500
66
4600
67
4700
69
4800
70
4900
72
5000
73
5100
75
5200
76
5300
77
5400
79
5500
80
5600
82
5700
83
5800
85
5900
86
6000
88
6100
89
6200
91
6300
92
6400
94
6500
95
6600
96
6700
98
6800
99
6900
101
7000
102
7100
104
7200
105
7300
107
7400
108
7500
110
7600
111
7700
113
7800
114
7900
115
8000
117
Gear 4
700
13
800
15
900
17
1000
19
1100
21
1200
23
1300
25
1400
27
1500
29
1600
30
1700
32
1800
34
1900
36
2000
38
2100
40
2200
42
2300
44
2400
46
2500
48
2600
49
2700
51
2800
53
2900
55
3000
57
3100
59
3200
61
3300
63
3400
65
3500
67
3600
68
3700
70
3800
72
3900
74
4000
76
4100
78
4200
80
4300
82
4400
84
4500
86
4600
87
4700
89
4800
91
4900
93
5000
95
5100
97
5200
99
5300
101
5400
103
5500
105
5600
106
5700
108
5800
110
5900
112
6000
114
6100
116
6200
118
6300
120
6400
122
6500
124
6600
125
6700
127
6800
129
6900
131
7000
133
7100
135
7200
137
7300
139
7400
141
7500
143
7600
144
7700
146
7800
148
Here's a Wallace Racing Calculator.
Calculate RPM for given MPH, Rear Gear Ratio and Trans Gear Ratio
Enter MPH: 148
Enter Tire Diameter: 27"
Enter Rear Gear Ratio: 4.10:1
Enter Trans Gear Ratio: 1.00:1
Result -- 7,551 rpm
Here's another one from TCI.
Enter MPH, The Tire Height in Inches, The Rearend Ratio, Trans Ratio, & Converter Slip %
RPM = (Rearend Ratio * MPH * 336.136 * Trans Ratio * (1 + (Conv Slip% / 100))) / Tire Height
MPH 148
Tire Height 27
Rearend Ratio 4.10
Trans Ratio 1.00
Conv Slip 0%
RPM = 7554.345
Here's their calculator.
Quick Facts
Gear 1 Max Speed - 57 MPH at 8000 RPM
Shifting at 8000 RPM puts you at 5300 RPM in Gear 2
Gear 2 Max Speed - 85 MPH at 8000 RPM
Shifting at 8000 RPM puts you at 5800 RPM in Gear 3
Gear 3 Max Speed - 117 MPH at 8000 RPM
Shifting at 8000 RPM puts you at 6200 RPM in Gear 4
Gear 4 Max Speed - 152 MPH at 8000 RPM
Shifting at 8000 RPM puts you at 5900 RPM in Gear 5
Gear 5 Max Speed - 205 MPH at 8000 RPM
Shifting at 8000 RPM puts you at 5400 RPM in Gear 6
Gear 6 Max Speed - 304 MPH at 8000 RPM
Cruising RPM at 70MPH in Gear 6 is 1800
Gear 1
700
5
800
6
900
6
1000
7
1100
8
1200
9
1300
9
1400
10
1500
11
1600
11
1700
12
1800
13
1900
14
2000
14
2100
15
2200
16
2300
16
2400
17
2500
18
2600
19
2700
19
2800
20
2900
21
3000
21
3100
22
3200
23
3300
24
3400
24
3500
25
3600
26
3700
26
3800
27
3900
28
4000
29
4100
29
4200
30
4300
31
4400
31
4500
32
4600
33
4700
34
4800
34
4900
35
5000
36
5100
36
5200
37
5300
38
5400
39
5500
39
5600
40
5700
41
5800
41
5900
42
6000
43
6100
44
6200
44
6300
45
6400
46
6500
46
6600
47
6700
48
6800
49
6900
49
7000
50
7100
51
7200
51
7300
52
7400
53
7500
54
7600
54
7700
55
7800
56
7900
56
8000
57
Gear 2
700
7
800
9
900
10
1000
11
1100
12
1200
13
1300
14
1400
15
1500
16
1600
17
1700
18
1800
19
1900
20
2000
21
2100
22
2200
23
2300
25
2400
26
2500
27
2600
28
2700
29
2800
30
2900
31
3000
32
3100
33
3200
34
3300
35
3400
36
3500
37
3600
38
3700
40
3800
41
3900
42
4000
43
4100
44
4200
45
4300
46
4400
47
4500
48
4600
49
4700
50
4800
51
4900
52
5000
53
5100
54
5200
56
5300
57
5400
58
5500
59
5600
60
5700
61
5800
62
5900
63
6000
64
6100
65
6200
66
6300
67
6400
68
6500
69
6600
70
6700
72
6800
73
6900
74
7000
75
7100
76
7200
77
7300
78
7400
79
7500
80
7600
81
7700
82
7800
83
7900
84
8000
85
Gear 3
700
10
800
12
900
13
1000
15
1100
16
1200
18
1300
19
1400
20
1500
22
1600
23
1700
25
1800
26
1900
28
2000
29
2100
31
2200
32
2300
34
2400
35
2500
37
2600
38
2700
39
2800
41
2900
42
3000
44
3100
45
3200
47
3300
48
3400
50
3500
51
3600
53
3700
54
3800
56
3900
57
4000
58
4100
60
4200
61
4300
63
4400
64
4500
66
4600
67
4700
69
4800
70
4900
72
5000
73
5100
75
5200
76
5300
77
5400
79
5500
80
5600
82
5700
83
5800
85
5900
86
6000
88
6100
89
6200
91
6300
92
6400
94
6500
95
6600
96
6700
98
6800
99
6900
101
7000
102
7100
104
7200
105
7300
107
7400
108
7500
110
7600
111
7700
113
7800
114
7900
115
8000
117
Gear 4
700
13
800
15
900
17
1000
19
1100
21
1200
23
1300
25
1400
27
1500
29
1600
30
1700
32
1800
34
1900
36
2000
38
2100
40
2200
42
2300
44
2400
46
2500
48
2600
49
2700
51
2800
53
2900
55
3000
57
3100
59
3200
61
3300
63
3400
65
3500
67
3600
68
3700
70
3800
72
3900
74
4000
76
4100
78
4200
80
4300
82
4400
84
4500
86
4600
87
4700
89
4800
91
4900
93
5000
95
5100
97
5200
99
5300
101
5400
103
5500
105
5600
106
5700
108
5800
110
5900
112
6000
114
6100
116
6200
118
6300
120
6400
122
6500
124
6600
125
6700
127
6800
129
6900
131
7000
133
7100
135
7200
137
7300
139
7400
141
7500
143
7600
144
7700
146
7800
148
Thread Starter
Race Director
Joined: Dec 2006
Posts: 12,393
Likes: 2,911
From: Fort Worth, Texas
Waiting to here back from rounding down in formula, he's busy tuning beachbums 9.8 c6z and I'm not around...
https://www.corvetteforum.com/forums...bondurant.html
https://www.corvetteforum.com/forums...bondurant.html
Thread Starter
Race Director
Joined: Dec 2006
Posts: 12,393
Likes: 2,911
From: Fort Worth, Texas
After talking to James about the calculations, it's been changed to where it's pretty much spot on with the others now. He originally took 3% off the tire diameter as that's the shrunken radius of his 28" slick at 10psi on his 5.50 ls turbo stang since the tire isn't perfectly round when sitting on the ground under cars weight and doesn't actually have 87.92" of rollout. It just so happens that the growth appears to be about the same as you point out on the data log you provided being 3% of 27 is .81", 3% of 148 is ~144mph and 3% of 7550 is ~225rpm.
Last edited by PRE-Z06; Apr 16, 2015 at 11:14 PM.
Race Director
Joined: Mar 2005
Posts: 11,549
Likes: 27
From: Southampton NJ
Thread Starter
Race Director
Joined: Dec 2006
Posts: 12,393
Likes: 2,911
From: Fort Worth, Texas
3rd Gear
Joined: Jan 2014
Posts: 3
Likes: 0
I had programmed in a 3% reduction in tire height as that was what got my cars closest to perfect @ 80mph (a good halfway point IMO). Since everyone wants it to line up with all of the other gear/speed calculators I took that 3% reduction away.
I made this to help others out and any suggestions for additional features or fixes would be appreciated.
Thanks,
James Karger
I made this to help others out and any suggestions for additional features or fixes would be appreciated.
Thanks,
James Karger