Racing ratios for GeLo 2.5 SR
Posted: Tue Apr 19, 2022 12:23 pm
The ‘74 type 915/06 5-speed gearbox from my T is soon to be rebuilt for GeLo with racing ratios, Quaife LSD and oil pump (but no cooler) to replicate the 915/00 ‘box the SRs were fitted with. However Angus and I are debating which ratios we should fit. The stock 915/06 ‘box was fitted with the following:
1st: 11:35
2nd: 18:33
3rd: 23:29
4th: 27:25
5th: 29:31
Final drive: 7:31
With Michelin TB15s (18/60’s (F) and 23/62’s (R)) on 8 & 9” Fuchs, we want to achieve strong acceleration (which it should have with 270 bhp @ 7,800 rpm & 960 kgs) and good top speed for mainly A and B road driving as well as the odd trackday.
I have looked at the ‘Airfield’, ‘High speed circuit’ and ‘Nurburgring’ ratios in ‘Information…for Sports Purposes’ and see that the respective ratios are:
Airfield circuit:
1st: 14:37
2nd: 18:32
3rd: 22:29
4th: 26:26
5th: 28:23
Final drive: 6:32
High speed circuit:
1st: 15:36
2nd: 20:32
3rd: 23:28
4th: 26:26
5th: 28:23
Final drive: 7:31
Nurburgring:
1st: 14:37
2nd: 20:32
3rd: 22:29
4th: 25:27
5th: 27:25
Final drive: 7:31
Has anyone had any experience of these ratios for a ‘fast road’ application and what would the advice be to achieve good driveability and shifting?
1st: 11:35
2nd: 18:33
3rd: 23:29
4th: 27:25
5th: 29:31
Final drive: 7:31
With Michelin TB15s (18/60’s (F) and 23/62’s (R)) on 8 & 9” Fuchs, we want to achieve strong acceleration (which it should have with 270 bhp @ 7,800 rpm & 960 kgs) and good top speed for mainly A and B road driving as well as the odd trackday.
I have looked at the ‘Airfield’, ‘High speed circuit’ and ‘Nurburgring’ ratios in ‘Information…for Sports Purposes’ and see that the respective ratios are:
Airfield circuit:
1st: 14:37
2nd: 18:32
3rd: 22:29
4th: 26:26
5th: 28:23
Final drive: 6:32
High speed circuit:
1st: 15:36
2nd: 20:32
3rd: 23:28
4th: 26:26
5th: 28:23
Final drive: 7:31
Nurburgring:
1st: 14:37
2nd: 20:32
3rd: 22:29
4th: 25:27
5th: 27:25
Final drive: 7:31
Has anyone had any experience of these ratios for a ‘fast road’ application and what would the advice be to achieve good driveability and shifting?