"up gears" question By jake aka:ventoscoot (Read 2,166 times)

[jake aka:ventoscoot]

Pretty much the last mod I want to do is to "up gear" my final drive. I am looking at the 15t and 18t options. Any advice would be great. I am looking as always for mid-top end and good 55-60 cruising speed. I pretty much have that now, but figure the gears will help me get there and stay there better.

[jake aka:ventoscoot]

oops, posted in the wrong forum. that is what I get for posting late, when I am tired.

[Alleyoop]

Jake,
Hard to say without knowing how many teeth your current gears are. But if you go 3 More Teeth on the small gear and 3 Less Teeth on the big gear it should pick up from 11-14mph. If you go 2 More on the small gear and 2 Less on the big gear it is about 8mph gain.
Alleyoop

[dannicus]

Nov 6, 2010 9:14:04 GMT -6 Alleyoop said:

Jake,
But if you go 3 More Teeth on the small gear and 3 Less Teeth on the big gear it should pick up from 11-14mph. If you go 2 More on the small gear and 2 Less on the big gear it is about 8mph gain.
Alleyoop

Keep in mind this is based on gearing, not power. You won't actually pick up top end. (unless you're going down hill ;D)

[royldoc]

Keep in mind this is based on gearing, not power. You won't actually pick up top end. (unless you're going down hill ;D) [/quote]


Have to disagree. If your engine is turning 6500 rpm at 45 mph and you put a taller gear in you will gain more speed at same engine rpm.


Roy

[erictheviking666]

I just checked out the prices on Scrappydog.com, he is incredibly cheap! Only $39.95 that's a sweet deal! I can't believe how cheap they are being that 6 to 8 months ago you couldn't buy those in the US for a QMB139. Enviromoto was the first I'm aware of but now Scrappydog must have one sweet vendor on those to be able to sell it for that.

[Alleyoop]

Rolyldoc,
You are right on Bro, I am an Old Hot Rodder and know all about what gearing will do. High gears in a car will out run one with low gears. They may beat you up to a certain point from start up but the one with the High Gear will catch up and pass your butt:)

Ever hear the song LITTLE NASH RAMBLER-- at the end of the song he say How do you get this car out of SECOND GEAR(HAHA).
Alleyoop

[royldoc]

Hey ally I've tweaked a few cars in my days also. Got into radio control cars and raced them for a long time. Even raced yard tractors for a while. Man that's fun.


Roy

[royldoc]

Ya taller gears will give ya more top end speed just takes more road to get their.


Roy

[dannicus]

It shouldn't come as a suprise to u guys that to go faster, it requires more power. All you can do is try to gear for the engine to pull top speed at peak power rpm. These bikes put out around 9hp max, probably around 8 at the wheel. The max speed you can hope for is probably gonna be way shy of a true 65mph with stock output regardless of gearing. Gear it much taller, and you'll never reach peak horsepower. You'll lose top speed AND acceleration. Simple physics.

[ScooterRider]

Dannicus is correct. Simple physics applies here. Example; hop onto a 18-speed bicycle starting in a lower drive sprocket, switch then onto higher one and see how your legs will feel. You'll need more power to gain the speed.
In the end, one with more power ….wins!

[jake aka:ventoscoot]

on the more power end, see my sig with the 160cc top end, ported head, high lift cam, UNI filter, and custom big header exhaust.

[robb]

From what I read , Jake; Danicus says you are due for an upgear. I'm glad he agrees with us.
All kidding aside , the gears someone needs when they live on top of a mountain aren't the best gears for someone living in Kansas, unless the person in Kansas wants to be gear bound at 40-45mph. A stock scooter may not be able to use more extra gearing than the tallest tire it can run. A tweaked to the max scooter could probably use a bit more. I think Dannicus is wrong on one point though. You need to be geared to max speed at a point beyond max power. The math breaks down in the real world. Geared to max speed at max power means if you hit a larger than average hill or have more than a slight headwind you are instantly falling out of peak power and it spirals down from there. If you are geared for max at 1,000 to 2,000 rpms beyond peak power you are being forced closer to peak power when wind and hills slow you down. My $.02 from 26 years wrenching Robb

[dannicus]

@ robb,

You're right. That's a good suggestion on how find gearing to suit more situations. My suggestion was based on flat ground with no headwinnd and no extra chilidog for lunch. It's always a tradeoff when you have to deal with things like hills. Like you basically said, gearing to tackle hills is not ideal for reaching max speed on the flats. The math doesn't break down, tho. There are just more factors to consider. Also, the OP never told us what rpm he is presently turning at the target 55, so we don't know wether he actually needs to go taller.

[Alleyoop]

Well right now the Trike really starts to pull right at 6000 rpms and the 3" taller tires really kick in right around 30mph. It gets up to 35-40 pretty quickly and you can then feel the speed start to build up with the taller tires. Then I crank on it just a little more and reach 50-55 mph at around 6600-6900 rpms and I back off the throttle and it holds 50mph at 5500 rpms. If there is a little wind behind me I can even drop the rpms down to 5000 and it will run at 50mph. If there is a good head wind then I have to be at 6000rpms to hold 50mph.

With the taller gearing once the weight is rolling at the same rpms It should be rolling at Least 55 at the same rpms. Taller Gearing comes in once the intial weight has been moved a certain distance. Some compensatiion can be done by now using a 1 to 1 1/2 gram Lighter weights to keep the belt in the mid-range longer as well as getting higher rpms.
Alleyoop