engine speed vs gear

[LEN_LEEB@domain.elided]

     Quentin asks:
     ...if I know gear ratios can I calculate what engine speed I need to 
     attain if I am changing to a lower gear?
     
     eg If I am travelling in fourth at 3,000 rpm what rpm would I need to
     maintain the same road speed in third
     
     It just depends on the gear ratios; in my spider the transmission 
     ratios are:
     1st ... 3.32 
     2nd ... 1.99
     3rd ... 1.35
     4th ... 1.00
     5th ... 0.79
     So, if I am in 4th at 3,000 (1.00 to 1 gear ratio), I need 1.35 times 
     that many rpms for 3rd gear, or 4050 rpm to precisely match speeds, 
     and save wear on my synchros.
     If I were changing from any other gear, my formula is "new gear 
     divided by old gear, times RPM." In the example above,
               1.35/1.00 * 3000 = 4050. 
     If upshifting, you would reduce rpm's from 4050 to 3000.
     Enjoy shifting and matching speeds!
     Len

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