Optimum RPM at 70 mph?

[dmillsr3]

1987 Electra Glide
Trike conversion
Stock front pulley (34T I think) and stock rear pulley (70T confirmed)
Rear tires diameter 25.5. The stock rear tire should be about 25.7 in diameter.

My rpm at 70mph is 3500. I am thinking it should be about 3000 or a little less.

I think the best way to adjust would be a smaller rear pulley. I can find a 65 T pulley. But I don't know how to calculate the result. I can find plenty of rpm/mph/gear ratio calculators but I have NOT found one to take pulley size into consideration.

I could go to a taller tire but at more expense than a rear pulley.

Any suggestions or comments welcomed.

[FLTR2008TRIKE]

1987 Electra Glide
Trike conversion
Stock front pulley (34T I think) and stock rear pulley (70T confirmed)
Rear tires diameter 25.5. The stock rear tire should be about 25.7 in diameter.

My rpm at 70mph is 3500. I am thinking it should be about 3000 or a little less.

I think the best way to adjust would be a smaller rear pulley. I can find a 65 T pulley. But I don't know how to calculate the result. I can find plenty of rpm/mph/gear ratio calculators but I have NOT found one to take pulley size into consideration.

I could go to a taller tire but at more expense than a rear pulley.

Any suggestions or comments welcomed.

Here is a online calculator from Baker Transmissions >>> https://bakerdrivetrain.com/pages/ca...e-rpm-vs-speed

[dmillsr3]

Here is a online calculator from Baker Transmissions >>> https://bakerdrivetrain.com/pages/ca...e-rpm-vs-speed

Thanks, that's a big help. But to gear to get about 3000 rpm at 70, I would need a 61 tooth pulley. Not sure, but that would probably take a new belt also. At this point, I might go to taller tires and the best alternative.

Am I off on my calculations that I should be at about 3000 rpm instead of 3500 at 70?

[Lee H. Mann]

Don,
Optimum gearing can mean different things. With a trike and a stock evo engine you will need rpm's to do anything above 60 mph. If you change gear ratio to reduce cruising engine rpm you will lose any punch at 60 mph and hurt performance off the line. You can do engine mods that will improve performance such as cam and compression but you need rpm's regardless. 3000 rpm's at 70 mph will feel like you are pulling a log trailer.

Another option is a 6 speed transmission. You can gear your drivetrain down to give you off line performance and still have usable rpm's at highway speeds.

EXAMPLE: 2007 & 2008 FLH changed their gearing from a 70 tooth rear sprocket to a 66 tooth. They are real pigs (sorry to anyone owning a stocker) taking off after trike conversions. Changing the primary chain and gear really improved all around performance making it easier to take off and you can actually utilize 6th gear for pulling rather then to just save engine rpm's.

Different ways to skin the cat.

[gerald martin]

Don,
Optimum gearing can mean different things. With a trike and a stock evo engine you will need rpm's to do anything above 60 mph. If you change gear ratio to reduce cruising engine rpm you will lose any punch at 60 mph and hurt performance off the line. You can do engine mods that will improve performance such as cam and compression but you need rpm's regardless. 3000 rpm's at 70 mph will feel like you are pulling a log trailer.

Another option is a 6 speed transmission. You can gear your drivetrain down to give you off line performance and still have usable rpm's at highway speeds.

EXAMPLE: 2007 & 2008 FLH changed their gearing from a 70 tooth rear sprocket to a 66 tooth. They are real pigs (sorry to anyone owning a stocker) taking off after trike conversions. Changing the primary chain and gear really improved all around performance making it easier to take off and you can actually utilize 6th gear for pulling rather then to just save engine rpm's.

Different ways to skin the cat.

THANKS JIM
I was really thinking of building a trike with either a softail evo or a evo sportster. Your remarks on the RPMs and the speed made me think KEEP THE FREEWHEELER its all I need
Thanks
I really get a lot of great info from this forum

[dmillsr3]

Don,
Optimum gearing can mean different things. With a trike and a stock evo engine you will need rpm's to do anything above 60 mph. If you change gear ratio to reduce cruising engine rpm you will lose any punch at 60 mph and hurt performance off the line. You can do engine mods that will improve performance such as cam and compression but you need rpm's regardless. 3000 rpm's at 70 mph will feel like you are pulling a log trailer.
Another option is a 6 speed transmission. You can gear your drivetrain down to give you off line performance and still have usable rpm's at highway speeds.
Different ways to skin the cat.

Thanks once more for your advice. I plan to address engine mods or six speed transmission later this year. Trike is pulling strong up to 75 (haven't gone above that). Overall pleased with performance, but my MPG is kinda low--about 20 mpg. Thought mpg would be higher and thought getting the rpms down might help that, but I don't want to sacrifice that much performance.

[rhino 2]

Thanks once more for your advice. I plan to address engine mods or six speed transmission later this year. Trike is pulling strong up to 75 (haven't gone above that). Overall pleased with performance, but my MPG is kinda low--about 20 mpg. Thought mpg would be higher and thought getting the rpms down might help that, but I don't want to sacrifice that much performance.

The 6 speed trans, In my opinion will take care of most if not all of your problems...

[dmillsr3]

The 6 speed trans, In my opinion will take care of most if not all of your problems...

Will the final drive on the 6 speed be 1:1 or an overdrive gear?

[alienwulf]

At 80 I am pulling 3300 rpm's with a Crane Fireball 300 cam and ported heads. So it can be done gearing is stock. MPG is between 30 and 35 depending how I ride that's with an S&S carb. Evo's are good strong easy to work on motors.

[rhino 2]

Will the final drive on the 6 speed be 1:1 or an overdrive gear?

Over-drive...60mph Plus, on level ground..