Your opinion on top speed/RPMs

Ok, so I think I have finally figured out exactly what I want to do for my build.
My question to you is... With the GXH50 having this power curve:


...and a setup basically exactly like the SBP setup what will be my maximum possible speed at what RPM.

I'm trying to figure this out so that I can choose the correct gear ratios before I purchase the gears.

With the help of Jim Donovan at MaxTorque.com I have been able to figure a lot of things out..he is a real stand up individual; I would recommend doing business with him to anyone. He pointed me to a speed calculator on his website which I pretty much totally revamped. My best guestimate is that after the 6000 RPM range the torque loss in the curve is going to be the major limiting factor preventing me from going any farther.

Here is a picture of my calculations with what I am guessing will be the bikes maximum speed(about 225lbs total is my guess of the weight):


(I could be way off though as I really don't know what the heck I'm talking about..also, I don't intend to ride at these speeds, I'm just making sure that if I can, and I want to, then I'll be able to. So please let's keep the yelling about me killing myself to a minimum )

Remember, this is the absolute maximum speed I think I might be able to get close to, if you think I might be able to get to a higher speed at 6K RPMs then I will reduce the ratio to reach that speed, but if you don't think I will be able to get any where near that speed then I will increase the ratio to reflect the median speed that everyone thinks I could reach. Additionally, if you think I might be able to reach that speed but that it will be closer to 7K RPMs I will change the ratios accordingly and so on and so forth.

Here is a link to the speed calculator just in case anyone wants to use it.

I think that's about it for now, thanks a ton for any help and happy ridin!

P.s. I fixed the typo in the calculator...

Um, where is the attachment??

Sorry, I had to edit that...they wont let you upload an excel file. PM me your email and I'll send it to you.

There is a link to the calculator now if you want to use it.

With a shift kit, 11 tooth jackshaft sprocket and 5 speed rear 26" bike I top out at 32 mph at about 6000rpm. Engine vibs just won't let it rev any faster.
Good luck

Fantastic info, thank you! I'm assuming that's with the same engine. Is the total weight of you and the setup about the same?

Works great on paper, Have you talked to Walt Disney about it? Bike is going two fast for the frame. No, No, No. The Carb/Firb Frame is not the same. Steel/ wiil hold up.

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Thanks for the post but honestly that doesn't help me out too much...I believe the frame is aluminum. The speed I'm thinking is far too high, as it is right now I'm thinking about adjusting the ratios down around 40mph unless someone chimes in with some solid info to the contrary.

You have not figured in how much horsepower it takes to move this combination at speed. If you do not include that, you can gear the up far enough that, theoretically, 1 hp would result in 300 mph- but we all know that will not happen. There is more to it that gearing. Why don't bicycles have 80 tooth front sprockets with 12 tooth rear so we can all pedal at highway speeds? To defeat all the forces, wind, friction, gravity, etc.- you will need closer to 5 hp to get to 50 mph.

With 2.5hp, you can get around 40 mph with proper gearing, but not much more no matter what ratios you plug in. There is just not enough power to get the engine to spin fast enough to get close to 50 mph.

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HoughMade at WIRED.com: http://www.wired.com/cars/coolwheels...memade_bicycle

This I know and that was the point of this post..to see just how fast a 2.5HP GXH50 would push me. Now that I have a good idea of that, thanks to your post on the other website I will be able to choose a gearing that at my lowest rear ratio I am only traveling at or around 40MPH at the given RPM range which will give me optimum power throughout the entire gear range.

Thank you so much for your help HoughMade, I think I have the info I needed