37:11 final drive and high rpm

[georgej]

My newly purchased '78 R80/7 seems to run at high rpm to me.I'm turning 5000 at 60 mph in 5th gear.the previous owner said the bike came with a 37:11 final drive from the factory and said it gives more power for two up riding. Any opinions/views on this?
George

[James.A]

My R75/5 turns 5000 RPM at 60mph (indicated) IN THIRD GEAR! Your final drive ratio works out to 3.36:1, mine works out to 3.2:1. That's not enough of a difference to account for your observation. At 5K in high gear, I'm travelling way north of 70mph. I'd guess that your speedo, or tach, or both are not calibrated correctly for your drivetrain.

[Boxerkuh]

I will guess that your speedo is not calibrated correctly or your tach is off. I have a 1986 R80 with a 37:11 final drive. For comparison in 5th gear my readings are:
5000 rpm = 80 + mph
3500 rpm = 60 mph

Hope that helps you....:eat :drink

[20774]

As previously noted, something's not reading right...check out this site to see what the standard values should be for the 37:11 (3.36) rear end:

http://www.largiader.com/articles/gearing/

Also, find a 5 mile section of Interstate highway where you can hold a steady speed, say 65mph, and time yourself across the distance. Do the math and compute mph to see how it matches to the speedo.

A 37:11 should be matched with a speedo with the numbers 1.244 according to:

http://pweb.jps.net/~snowbum/ringgears,etc.htm

This page shows that the R80/7 came with either the 32:10 or 37:11. I think the 37:11 is the stock European gearing while the 32:10 is probably meant for the US with the more wide open spaces.

http://www.ascycles.com/history_r80_7_data.aspx

[georgej]

Thanks to all of you for the replies. That European gearing makes sense. I will say I'm a little surprised by the fifth gear.I've been told in the past that a five speed transmission won't make much difference as compared to my 4 speed /5. Regardless I love the R80/7 especially compared to my R50/5.
George