How fast will my bike go if....

R7 · 03-13-05, 01:41 PM

it was in 6th gear which is a 0.808 ratio, had a 15/38 final drive (sprockets) and a rear tire circumference of 77 1/16" with a engine RPM of 10,500 rpm?

Also, what would the MPH difference be at every 500rpm intervals?

Anyone anyone?
Thanks

**highsider** · 03-13-05, 02:23 PM

A buck two-fitty.

R7 · 03-13-05, 02:35 PM

125? How did you come up with that?

I tried some of those ratio calculators online and entered the same info as i posted above and they said 357 mph, i tried it on 3 different ones and they all came up with the same number

**OreoGaborio** · 03-13-05, 02:38 PM

might wanna check if it's asking for the tire circumfrence or the tire diameter

R7 · 03-13-05, 02:42 PM

You can enter either or on those charts, the diameter is 24.5" and the circumference (they call it role out) is 77 1/16"

If 125 is correct, i'll be happy with that

A Orange bike will do OK at VIR

**OreoGaborio** · 03-13-05, 02:51 PM

http://www.cosportbikeclub.org/misc/SpeedCalc.html

give that a try

**highsider** · 03-13-05, 02:56 PM

....I have no idea, I was just busting your balls. I can't add past eight without taking my socks and my underwear off.

**smoothwaterman** · 03-13-05, 03:02 PM

38/15 sprockets
.808 6th gear
Tire diameter 24.53 / Circ. 77.0632027

10,500 rpm = 246.30 mph
10,000 rpm = 234.60
11,000 rpm = 258.0

Hope that helps.

If you can provide the following, I'll give you a complete spreadsheet. You should find it all in the owner's manual.

Example listed:
Primary Ratio 1.5200
Secondary Ratio 38 15 2.5333
1st Gear 35 13 2.6920
2nd Gear 29 15 1.9330
3rd Gear 32 20 1.6000
4th Gear 28 20 1.4000
5th Gear 27 21 1.2850
6th Gear 25 21 1.1900
Tire Diameter 24.50
Engine Redline 11,500

Peter

**smoothwaterman** · 03-13-05, 03:11 PM

That online calculator seems to be very close. (and a good link to bookmark)

The only difference I believe would be the actual tire mfg. differences in diameter/circumference for a certain size tire. ie - 17" dunlop and 17" michelin are not likely to be exact same.

Peter.

R7 · 03-13-05, 04:35 PM

Originally posted by OreoGaborio
http://www.cosportbikeclub.org/misc/SpeedCalc.html

give that a try

Awesome, thanks for the link

That's what i was looking for and it also provides the key to the whole ratio thing that i didn't considder, the primary reduction ratio

151.6 mph

**OreoGaborio** · 03-13-05, 04:38 PM

Originally posted by R7
Awesome, thanks for the link
That's what i was looking for and it also provides the key to the whole ratio thing that i didn't considder, the primary reduction ratio

151.6 mph

R7 · 03-13-05, 05:13 PM

OK, here's what i come up with, a little comparison if you will

2004 YZ 450 (my racebike) with the gearing i have on it does 114.6 mph (i was guessing 105-110mph) It has a 4spd transmission and has no problem pulling to the rev limiter in top gear

2004 KTM 450smc with the same final drive gearing as the YZ but with 2 extra gears up top, 151.6mph.. Question is, is the KTM motor as powerfull as the the YZ and will it be able to pull it up to the rev limiter in top gear? I doubt it at that speed and i'm not sure i want to test a tard out at those speeds

Anyway, looks like i'm leaving the R1 at home for the VIR trackday and taking a Orange bike

**OreoGaborio** · 03-13-05, 05:38 PM

fuck that, it's two days.... BRING BOTH

**smoothwaterman** · 03-13-05, 08:09 PM

Originally posted by R7
Awesome, thanks for the link
That's what i was looking for and it also provides the key to the whole ratio thing that i didn't considder, the primary reduction ratio

What is the primary ratio, 2.60? Apparently it's not 1.52.

**Degsy** · 03-13-05, 08:11 PM

Originally posted by R7
OK, here's what i come up with, a little comparison if you will

2004 YZ 450 (my racebike) with the gearing i have on it does 114.6 mph (i was guessing 105-110mph) It has a 4spd transmission and has no problem pulling to the rev limiter in top gear

2004 KTM 450smc with the same final drive gearing as the YZ but with 2 extra gears up top, 151.6mph.. Question is, is the KTM motor as powerfull as the the YZ and will it be able to pull it up to the rev limiter in top gear? I doubt it at that speed and i'm not sure i want to test a tard out at those speeds

Anyway, looks like i'm leaving the R1 at home for the VIR trackday and taking a Orange bike

R7 man, c'mon. Bring the R7!!!

R7 · 03-13-05, 08:37 PM

Originally posted by smoothwaterman
What is the primary ratio, 2.60? Apparently it's not 1.52.

The primary on the YZ is 2.818 and on the KTM it's 2.3

R7 · 03-13-05, 08:39 PM

Originally posted by Degsy
R7 man, c'mon. Bring the R7!!!

I'd love to bring it but i can't

If something were to happen, i can't even get parts for it anymore

**busa413** · 03-14-05, 10:58 AM

I think the forumla and calculations you guys are using will give you the speed at which it can spin it's tire or spin a dyno. Real world speed is going to be different because you are going to be pushing against a wall of air which around 100MPH is much greater than people realize. The higher you go after that the harder and harder it gets. The power your engine produces will also vary depending on air quality and conditions.

**Idiotboy** · 03-14-05, 11:23 AM

I think lack of aerodynamics will keep you from going 151,but even 120-125 will be scary fast on a dirtbike.Are you putting the six-speed in there?

**TLRMan** · 03-14-05, 12:46 PM

Originally posted by Idiotboy
I think lack of aerodynamics will keep you from going 151,but even 120-125 will be scary fast on a dirtbike.Are you putting the six-speed in there?

and lack of horsepower....

Gear it so it won't pull anymore, and you are bouncing off the limiter....This will be your top speed...

**OreoGaborio** · 03-14-05, 01:46 PM

Originally posted by TLRMan
and lack of horsepower....
Gear it so it won't pull anymore, and you are bouncing off the limiter....This will be your top speed...

hehehe, well obviously that'll be his top speed if he's bouncin off the limiter...

wouldn't you rather gear it so it's at top speed right around peak power?

**beet** · 03-14-05, 01:50 PM

Originally posted by OreoGaborio
http://www.cosportbikeclub.org/misc/SpeedCalc.html

give that a try

**busa413** · 03-14-05, 01:55 PM

Originally posted by OreoGaborio
hehehe, well obviously that'll be his top speed if he's bouncin off the limiter...

wouldn't you rather gear it so it's at top speed right around peak power?

You will still continue accellerating past your peak power. At your peak power point you will just be accellerating at a higher rate. If you want maximum top speed you want to gear it so that you bring your high gear right to the redline.

**OreoGaborio** · 03-14-05, 02:00 PM

hmm... aight... i'm not well versed in the whole top speed thing other than what i've attained from a few years of flight training but i figured that if you geared it so you can't accelerate much more past peak power then that'll be the top speed you can achieve, since the engine is generating the most power it can to overcome the aerodynamic resistance.... but like i said, the only knowledge i have comes from flying, not bikes... just figured the same kinda thing would apply.

**busa413** · 03-14-05, 02:09 PM

The point of peak power in your rev band is the point that you are accelerating at the greatest rate, but your engine still makes power beyond this point. Your rate of acceleration won't be as great as it was in your peak power spot, but you will still be able to accelerate and gain more speed until you get to the point that your bikes engine can not overcome the wall of air due to aerodynamics.

How are you compairing this to the theory of flight, I'm just curious.

How fast will my bike go if....

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