Gearing

Message

VermilionX · Wed Sep 20, 2006 4:25 pm

DivideOverflow wrote: Basically, you will just end up with a gimped bike.

MakeCarsStandSTill · Wed Sep 20, 2006 4:27 pm

I dont think it wil make that big a difference, its only eleven more miles accoding to you

dflow

DivideOverflow · Wed Sep 20, 2006 11:14 pm

MakeCarsStandSTill wrote:I dont think it wil make that big a difference, its only eleven more miles accoding to you dflow

Your bike probably won't actually do 189 out of the box, that is what it is theoretically GEARED for though.

In reality, wind resistance will probably be too much, and you will run out of motor in 6th gear and not make it to redline.

bcarlson · Thu Sep 21, 2006 12:57 am

I think I posted something about this before. Drag will play a major role in high speeds; much more important than power, rolling resisance, or gearbox losses. If you want fast, the relationship between hp and MPH is 8:1. In other words to double your speed you need 8 times as much power (its a cubic relationship). Anyway heres an example.

HP = 95 (my puny ride), Cd = 0.5, frontal area = 6 sqft, max speed = 151.8 MPH

If I want 175 MPH in theory I could add power, change gears or reduce drag. Let's see what is cheaper to do.

I would need 145 hp to get 174 MPH. Adding 50 hp to a bike like mine is getting really expensive. More than an exhaust and opening the air box.

Lowering coefficient of drag to 0.33 gives 175MPH and would be tricky but attainable.

Finally, I could bebuild my gearbox with custom rations and screw up the balance of the bike and still not attain 175 because I would run out of power long before getting there.

Keep in mind this is a simple example and does not take into account rolling resistance or losses from the gearbox.

http://www.tonyfoale.com/Articles/Aerodynamics/AERO.htm

JCS · #25 Unread post by **JCS** » Thu Sep 21, 2006 1:46 am

If you want to shorten some gears and make some gears taller a simple sprocket change will not do it. You will have do go with a full tranny with new gear ratios. $$$$$$$$$$$$$$$$$

MakeCarsStandSTill · Thu Sep 21, 2006 9:36 am

y0 thats why the threads called gearing

,, I never mentioned changing sprockets

Kaiser Soze · Thu Sep 21, 2006 9:40 am

I hope someone catches your 200mph crash on video.

MakeCarsStandSTill · Thu Sep 21, 2006 10:34 am

Kaiser Soze · Thu Sep 21, 2006 11:11 am

Dude. Your first bike. Changing gearing to hit 200mph.

I'll feel bad for you, but it won't be a surprise.

VermilionX · Thu Sep 21, 2006 2:27 pm

Kaiser Soze wrote:Dude. Your first bike. Changing gearing to hit 200mph.

I'll feel bad for you, but it won't be a surprise.

it's not his 1st bike.

he has some smaller ones before the 1k.

and the limiter is set at 186mph. get a TRE 1st if you don' have it yet.