rpm at speed

[Guest captain nemo]

Nah, that guy who claimed 220 mph never even saw 200 - not even 150. These are all tall tales told under the influence of beer most of the time. I've only met one person I know of who I believe saw 150+ on an Aprilia Mille. I believe him and I believe he has the skill and the bike to do it. Any other story like this I throw out until I can see that the story, the guy and the bike all match. I bet the guys who can actually do it don't say much about it. This guy I know doesn't. It took my clever interrogation methods to get it out of him.

[al_roethlisberger]

...hrmmm, well I dunno. Certainly top-speed tales are often couched in embellishment, but 150-ish is very do-able.

 

Let's assume the suggested ~7% error in an OEM speedometer. My high-speed run years ago across the Nevada desert indicated at 155mph would be about 145. I think that's close enough And the bike had more left, I just shut it down as it wasn't safe, and I was running out of road

 

And of course, around that time we did that 160 mile run, in 80 minutes... so average speed was 120mph. Given that we had to go up a mountain for about 1/4 of the distance, who knows what the top speed was

 

I don't think it takes any great skill to go that fast, just a capable bike, a long-enough road, and luck.... lots of luck.

 

But I don't think I'll be doing any of that again.... just not very safe.

 

al

[callison]

It would take someone with a knowledge of calculus and the properties of the tire, but there ain't no way a stock street tire is going to expand very much at the speeds our bikes are capable of. The race boys have more info on this. http://www.rbracing-rsr.com/gearspeed.html

Street tires are assumed not to expand enough to account for, other tire types are. These radial tires we use are very well constrained by their material.

 

Searching on the web is fun... just not profitable. Culled this from the thunderace guys:

 

-----------------------------------------------------------------------------------

 

Re:Top Speed Accuracy - stock vs Sigma

Date: Thu, 17 Jun 1999 16:23:43 -0800

From: Lance_Keigwin@alliedtelesyn.com (Lance Keigwin)

Subject: Re:Top Speed Accuracy - stock vs Sigma

 

I doubt tire growth is responsible for more than 1% BC800 error. Someone on the

R1 list did the math on this a while back and it worked out to about that (based

on what some authority -- Dunlop? -- said about 207GP tire growth at very high

speed).

 

The BC700/800 is known to be extremely accurate to 170+ mph. (Within 1/10%,

according to a radar test.) So you can conclude that:

- your BC800 tire circumference measurment is off (but you said you verified its

accuracy at 35 and 63). Or,

- your gearing is not what you think. Or,

- Mark's nifty program is faulty. Or,

- Your tach is wrong. Or,

- your BC800 is faulty. Or,

- Tire growth at speed is enormous!

 

Since the stock speedo is off about 8% (according to your statement that stock

80 is really BC800 74mph) I suspect that the stock 168 is probably about what

the BC800 said it was: ~153. This is consistent with my measurements too.

 

Lance.

R1, 996, ZX6R, 400RR

AFM #805

 

____________________Reply Separator____________________

Author: loki@iaonline.com (Michael J. Hand)

 

Here is the situation:

 

Stock (engine/pipe wise) '97 YZF1000R Dyno'd at 125hp. (at 6,000

miles - has 13,500 now) Gearing change has been performed putting on a

530 chain, at same time going up 2 teeth on the rear sprocket (stock

size front). I am running fairly worn (5,500 miles) Dunlop D207

tires. (being replaced July 1st right before I take CLASS on July

6th). I have added a Sigma BC-800 cycle computer and tested it

against radar at 35mph and 63mph - dead accurate at those speeds.

 

BTW - at 74-75mph sigma speed, stock speedo is reading 80.

 

According to the handy little gearing program that Mark Panos has on

his site, I should be geared for about 171 at 11,500 rpm (red line) in

top gear.

 

Was on a straight road, flat, no wind - mirrors were folded back

running flat out. pulled to 11,200 (or so) RPM before my road was

getting short quickly. Stock speedo was reading 168 (or so) Sigma

read my max speed at 152.7

 

What gives? which was accurate? Is it possible that the sigma did not

compensate for tire growth and the stock speedo was more accurate at

that speed?

 

What do you think????

 

-----------------------------------------------------------------------------------

 

And Metzeler's input, but no speed specified:

 

Metzeler says the 880 was built in response to a request from American Iron Horse, a small-scale bike manufacturer of big V-Twin customs. It uses Metzeler’s patented 0-degree steel belt construction that limits tire growth at speed and aids stability. The limited tire growth, adds Metzeler, means that custom builders can mount a fender as close as one-quarter inch from the tire’s maximum-diameter specs, perfect for that low-riding look.

 

-----------------------------------------------------------------------------------

 

I'm just going to go with tire slippage as a function of the horsepower required to go fast encountering the road surface/tire interface traction coefficient. Wow! That almost sounded like I knew what I was talking about.

[Guest carlomoto]

I know the engine on my bike sounds very happy when I'm at 100mph. And when I roll off the throttle, it takes its own sweet time to slow down -- almost as if it's telling me "hey, not yet, pal." Oh, wait, the bike's an Italian, so I guess it's more like "ehi, che lei pensa lei fanno?!"

 

My only problem is when I'm at speed I have to concentrate so much on just trying to hold on and scope for cops that I've never paid attention to the tach.