so far i've seen 163 indicated im pushing 250ish ready to ride. i think if i had the room the 172 is possible. the tach needle was vibrating something fierce but i am guessing i was within a few hundred rpm of the 10500 limit in the stock ecm
Slaughter: With the addition of wind resistance, rev limit off the dyno will NOT be the same speed as it was on the dyno. That's physics.
Blake: Stock setup or not, the mathematical top speed of a bike can not be achieved unless wind resistance and dynamic resistance is 0. If dynos some how calculate wind resistance and add that limiting factor to their drag wheel then the "top" speed is achievable, however I doubt the dyno is that smart.
This is the exact same thing as dropping a feather and a hammer from a given height. Theoretically, they should absolutely hit the ground at the same time, no matter their mass. In real life though, due to wind resistance, the hammer will always hit the ground first.
However, if you're on the moon...the results are a bit different.
And you all know how dead on the stock speedos are,right?? 180hp, won't do it without good aero package. T-man, nearly all sportbikes have terrible aerodynamics,they are concerned with looks. The worst part is the tail as good aero likes to have the air meet behind the bike cleanly. Like the old Buell RR bikes. The new rules at Bonneville have really emphasized this as the bikes taking advantage of the new tails have picked up some serious MPH---sit on bikes are at the 274 and up range. We bought a new tail for next year.
You'd be wrong. Although I'd grant you that the dyno is only one part of it. I know a fellow who once crafted a brilliant program that would take dyno information, air characteristics, elevation, coefficient of friction of salt with various moisture content, wheel spin and all sorts of things who was able, given sufficient data for a bike, to predict quite accurately how fast it would go.
These discussions tend to evolve into groups that who include lots of folks with opinions and folks with data gained of experience.
Court, you're not talking about a dyno. I was. So, I'm not wrong. Thanks.
Anyone, with enough time and patience one could reproduce the 1125R's specific coefficient of friction and every other needed variable and use that to get a somewhat reliable output via a modeling program. That's not the question or the problem. We're talking about guys putting their bikes on dynos, getting a top speed readout and thinking that's how fast their bike will go. It's BS.
It's not "BS" or as originally stated "pure bullshit" if the bike has the HP to run into the rev limit in top gear. The only discrepancy then being speed lost to rear wheel spin, not a huge factor for most bikes running on good pavement.
The speedo for the 1125R, like most bikes these days, is just a sensor reading tranny output speed, so it would not account for any rear wheel spin.
From sport bike rider MAG 2008 Buell " Performance Roll-ons: 60-80 mph/3.15 sec.; 80-100 mph/3.27 sec. Quarter-mile: 10.45 sec. @ 133.9 mph Top speed: 162.0 mph Fuel consumption: 24-30 mpg, 27.1 mpg average "
Blake, that I can sort of agree with you on. However, with the horsepower to get to that rev limit, you are then limited to the mechanics of the bike. Hence:
MPH=(rpm/fdr)(Do*pi/12)(60/5280)
For the Buell that equals about 162.4mph mechanically limited. So unless you change gearing, you're not going over 163mph...even in perfect conditions with more horsepower.
Anyone going over 162.4mph "indicated" isn't going the speed they think.
This bike in stock form will NOT go as fast as the dyno says, even with 300bhp. It's not mechanically possible.
Your rear wheel diameter is too small. I just went out to my garage, measured a spare bald Corsa 3 on XB rim 180/55/17, and got about 76.5 inches. That makes your real minimum diameter (on a bald tire, a new tire would be bigger) about 24.35, and your real top speed at rev limiter is 169.5mph. Give it a tire that isn't on the cords, and you are in the upper 170's bone stock.
I do agree that the dyno is BS, as most vehicles are overgeared for better fuel economy, but you would never be able to hit that top speed. Buell's are among the few that will top out at redline in top gear.
Froggy: That measurement is straight from my bike with a Rosso Corsa that is basically brand new in the center (my track tire). My math, oddly enough, links up exactly with what Buell reported as the bike's top speed (or within a very small percentage). Go figure.
Blake: Mechanics definitely don't change, you're correct, but why then would dynos be predicting such significant differences over the mechanical top speed (sometimes as much as 9 MPH?). Tire differences perhaps? Or possibly that the dynos aren't predicting it correctly?
D_Adams: That could be possible.
Also, has anyone recorded a high speed run, say north of 140MPH with correlating GPS data? How accurate is the speedometer/VSS on the 1125R? That would be interesting to see.
I know I hit 157 on mine in very cold conditions on a very flat road. I was just south of the redline in 6th gear and the bike pretty much had nothing left. Then again, it was on the way to get the VSS replaced because it had been reading 0 periodically...
All I'm saying is that you shouldn't trust your local dyno guy to give you top speed readings. Go out to your garage, measure your rear's diameter and plug it into the equation...that's your top speed.
Or bring it to the Texas Mile in Goliad this month
There are at least three factors that can render your equation less than accurate.
1. The rear tire contact patch effectively reduces the tire radius from axle center to pavement. It is that effective radius not the gross tire diameter that governs the rear wheel rotation versus speed relation.
2. As Dean notes, some tires can experience significant stretching (growth in diameter) at high speeds.
3. Accuracy in measuring the rear tire diameter, or more appropriately per #1, the effective rear tire drive radius.
Neat trick to finding the effective drve radius: Put a small dab of white paint onto the center of the rear tire at the back end of the bike; mount up and gently ride about twenty feet, just enough to leave two paint marks on the floor/pavement. Measure the center to center distance between the two marks; divide by 2P to get the effective radius.
I don't remember where I saw it, but it was a pic of a front tire and the damage it did to the fender. At rest, it looked fine and didn't appear that it would cause problems. At speed, it stretched and literally ate away the center of the front fender until there was nothing left but back in the pits, there was what appeared to be plenty of clearance between the tire and (what was left of it) fender again. I don't know how big the gap was, but I assume it was maybe 1/4" or a little more between the tire and fender. I'm only guessing that the rear would do the same and some tires will do it more than others.
All I need is more road.. and id like a new helmet and some nice pants and ill go for more... I'm interested now. Because I only weigh 140 maybe 145lbs and I can hit 145-150mph no problem! Like if I was bein lazy crusin in 6th going 80 mph and crack it. I'm gone. Don't even need to drop down gears.
Blake: Yes, I'd agree with all of those assumptions. Your number 1 assumption would actually lower mechanical top speed. Considering most riders are over 150lbs, I'd imagine at least a quarter to half inch deflection in rear tire. Fact is, at speed it would be a dynamic measurement due to road surface.
Dean: Do you remember how fast the tire was spinning? It seems to me that you would have to get a tire spinning pretty fast to see a lot of warpage like that. I'm thinking of drag racing funnys and how much their tires deform.
No, don't know the speed, but it was on a road course somewhere. I think the fender was white, pretty sure I saw the pic on here somewhere. I don't remember all the details, it could be that an incorrect size tire was mounted on the rim, I really don't know for sure. What I do know is, some tires will grow at speed. The drag slicks on a top fuel dragster is a perfect example.
Dragster tires are designed to distort like they do. Amazing to see.
I kinda doubt that sport bike street tires expand in diameter much at all. Kevlar is not stretchy stuff. I could be wrong. I have heard stories of racing slicks reportedly expanding at high temperature and high speed. I've not witnessed it first hand though.
