Ok, I will solve this argument once and for all. the tire does slip, and if it didn't, we wouldn't need any type of special compound. If the tire had infinite friction with the road surface... screw it, you folks wouldn't get it. Here is the deal, the only way that there is no tire slip at 200 mph is if there is no wind resistance. Aw frack, Ok, screw it, you folks are dumb if you don't believe in tire slip.

 

This bring to mind trying to explain valve overlap and VE. Now, do you believe that air has mass?...

Edit:
As soon as I wrote this, i thougt that it might help if you had some more "numbers", fictitious or other.
with a frontal area of 3.5 sq ft, you would be moving 57.75 pounds of air out of your way every second at 150 mph. This would equate to... drum roll...59400 lbs of air per hour. the only assumption that I have made is the frontal area, which I think is low. otherwise that super light air weighs in at a staggering .075 lbs per cubic foot, if my idiot brain is working right (75k lbs per million cubic feet)

 

I don't think anybody is arguing that tire slip doesn't exist. It just isn't the cause for the speedometer error that is built in. Don't need a radar to see my top speed. GPS is all you need. I'm on Michelin Pilot Powers, like many others here. I'm not comparing anything, nearly recording what my bike is capable of. Every one is likely to be slightly different.

 

I am certain that there was no claim that the tire slip was the sole cause of speedo discrepancies.

 

You are right, my bad. However, post 7 in this thead. It was stated that an online calculator proved that our bikes had a theoretical top speed of 183, but couldn't get past 159 due to tire slip. I verified that the speedometer error was mostly the same at 30mph as 140mph, possibly increasing 1/2 of 1% under very heavy throttle and sustained high speed. Therefore no tire-slip to speak of. Certainly not enough to account for our bike's inability to hit higher top speeds given enough HP. Oh, and my odometer readings are almost exactly what the GPS records, so assuming the odo was calibrated to the Dunlop 204 circumstance, there is not any discernible difference between the two tires.

 

ok, and that is where you go dumb. There is tire slip. Period. Final. Now, the earth being flat and all, that is true.

 

And you likewise. I have already stated that I am not claiming it does not exist. In fact it is a proven phenomena. It just has little a very small effect.

 

 

Eh ok, not much tire slip to speak of, lol. An amount so small as to have next to no effect besides tire wear.

 

http://ddl.stanford.edu/sites/defaul...rGerdesACC.pdf

And, lets talk about acceleration for a moment. When you are riding at, lets say, 180 mph, you are providing an acceleration force, even if the bike isn't accelerating. This is due in part to the large deceleration force that is being provided by wind and mechanical losses (including mechanical grip with the road). Net acceleration is naught, but there are two equal acceleration forces at that time, one in the positive (direction of travel) and one in the negative. If you can imagine, which I reserve my thoughts to your limitations, that the deceleration force, or rather the negative acceleration force, is rather large and that if it were to be applied to the rear tire alone while the bike were sitting with a locked rear wheel that there is a distinct possibility that the bike would slide across the pavement. Now, I dont have my handy dandy aerodynamic drag force calculator sitting in front of me, but when the bike puts out 100 horse to the wheel, and you limit the bikes acceleration with air to nothing, the tire will slip. Granted, the more aerodynamic, and faster the speed that the vehicle is moving in relation to the horsepower that it generates, the less slip will occur at said speed, or rather the percentage of slip will be lower, but the amount will likely be the same because the function of the acceleration force applied is the same. If you were to attach a 4x8 sheet of plywood to the front of the bike, the top speed would decrease, the slip percentage would increase. Given that the gp bikes of the old days were roughly 60 horse and could do the same speeds as the hawk, intuitively you can deduct that the drag on a modern bike is rather high by comparison. Between the two bikes, you can guess, hopefully with some degree of reasoning, that the modern bike is going to be achieving a much larger slip angle to achieve that speed. Now, what is the slip on our bikes? I think that depends on the speed, the wind angle, Cf, the Cd, and the horsepower applied ( or torque, HP just being a rate of application). What does that mean? Each scenario is going to warrant either a different calculation or measurement. So, get out there and check it out. plot out the gps speed vs displayed and watch the difference in the trend on gps, as it will show a non linear rate while it should in comparison to the displayed speed. Good luck, as science will win.

 

One good thing that came from this was the link 8451 posted to that gear calculator. That is one pretty cool tool.

 

WOW I didnt realize there was gonna be 3 pages worth of debate. Didnt get a chance to do another run with my gps this time. Been working on my wifes bike.

 

I'll give you another... Made by yours truly... All the Superhawk specifics already entered... You can change the formuales if you like...

 

Great, I'll check it out later tonight.

 

I guess I lied and do have a few more things to post here....

First I will say that I have really tried to change the way I write stuff (as this is my weakest form of communication) and have even been referred to as "hypersensitive" when someone disagrees with me. I have been trying but will never get to the level of some of the guys around here that are very good with the written word.

With that I will say that calling my post a bunch of BS, and sorry but where I am from and the time I am from, when you say "I'm not going to call BS but...." is calling it a bunch of BS and can be taking as being more than a touch rude.

Then to have it change to well you're right but the percentages you posted are not right without asking how or where they came from can also be taken as a bit rude which can make me become a bit crusty in my replies as it now fells a bit like nit picking not a discussion on the theory or physics of what is happening at the rear tire ....sorry for that.

So now that I have been told that I only know one bike and really don't know very much about bikes or the theory of what or how things work....well I guess I was wrong in trying to pass along so info from sources that some on here don't have access to.

I was asked to post links or proof to what I posted but was never asked where my info came from.

So here is how I learned about tire slip and why I use the 10% rule of thumb for speeds over 100mph.

Back in the day, as the kids say now, we were having some trouble setting up the race bikes. While trying to get the gearing right, the bikes just did respond the way the math or conventional thinking would suggest.

What I mean is, for example, you needed to hit 130mph down a straight before the next corner. By doing the math (tire size, gearing, engine rpm) we should have been hitting the proper speeds but were always going slower.

The I was introduced to Jim Allen. If that name is not familiar to some of you, here are some links for you Dunlop's Jim Allen Set To Retire | Cycle News Dunlop Dunlop Tire Test Interview with Jim Allen - YouTube

When I asked what his opinion was of our problem, I was asked if I was taking tire slip into account.... which lead to him explaining what it was and why it happened (and no I didn't record the conversation so I have no hard proof and you can choose to believe it or not) he also started explaining dual compound tires and a few other things....

Anyways, Jim told me that in order to overcome our issues we needed to gear the bike 10% higher to account for the tire slip.

Is this an exact number, No. As I have said it is a rule of thumb. There is no way to calculate an exact number as is constantly changing due to the outside forces acting on the bike.

Is it close, yes. If you look at the link to the gearing chart I posted and the radar speed tests done on the bike (I am talking about a SH here) you will see that using the 10% tire slip "rule" the numbers are real damn close.

It has been pointed out that the size of the rear tire isn't the same as what some people have on there bike now. Well yes that might be. The gearing chart and the radar speed tests were calculated using the stock tire (for the US) that came on the bike. So if you do not have a Dunlop 204 rear tire, then yes the numbers can and will be different but also the outcome of the tests or calculations will also be different.

So with that I will try to stay out of this discussion and also be careful of what topics I bring up.

Sorry if I offended anyone.

 

Wow 8541 I am impressed it took a big man to admit that, and I'm not being sarcastic. another factor in speedometer inaccuracy can be tire growth, some tires have very large growth when heated and traveling at high rates of speed. Not to mention if you are leaning the bike over which not only changes the tires diameter but also causes increased tire slip. Just my 2 cents.

 

No offense taken. You knowledge and opinions are invaluable here. Sometimes theories are tested by others, that's how new theories are formed. No disrespect intended.

 

One thing I have learned over the years of being on forums is it’s not so much how you mean something but how it’s interpreted. This applies for what you type as well as what you read. If you’re demeanor is that you are always 100% correct and that anyone who challenges you is an idiot then you’re going to take things one way. It sounds as though I’ve had some of the same issues as you when posting information on other forums. One thing that will always happen is if you start to slam someone they are going to get defensive, especially if you start doing it in other unrelated threads which is as I said there being very juvenile. But you know what we all have our moments.
A suggestion is take what’s being said at face value. When I said I’m not calling BS that’s all I meant by it. In my post I was skeptical of what you were saying and that skepticism came largely from the amount of slip you were claiming to be nearly 30mph worth.
The more the thread progressed and information was submitted I agreed with you were correct in that tire slip was a factor but still not to 30mph and you just took what I was saying as you were completely wrong which was nowhere near the case.
Then you go slam me in another thread where I asked a specific question about these bikes because I’ve never had the head off one questioning my ability and experience. I never said you only know stuff about one bike but I did say that just because you have specific knowledge of a particular bike doesn’t mean that someone else that doesn’t, doesn’t know anything either. So again you took what was posted and added your own twist.
I do appreciate you appearing to calm down a bit and start posting with a little more sense and willingness to talk about this in a civil manor rather than flying off the hook.
I find what you’ve posted here to be very informative as to why you came to what you believe and I do think that in the case of what you were doing a 10% increase in gearing would probably be a good rule of thumb, not so much that it will exactly compensate for the amount of slip happening, but to overcome it and then give a fudge factor. This makes perfect sense in using the 10% factor and you never said this before.
RZ, myself and the other na sayers were just trying to get a more realistic amount of slip that we could measure. RZ did an awesome job doing just that and showing the actual difference in nearly negligible when riding on the street. But then how often is the bike at WOT or max braking on the street vs. the track? So on the track it’s going to be much more prevalent. I think a part of the problem here is there are other factors at work here that also come into effect to get to your 10% rule on the track where we were trying to nail down a more exact reading for on the street so the data that was coming up was a bit off, hence the big debate.
I apologize if my first post in this thread ruffled your feathers Hawk, that certainly wasn’t the case. I love good debates like these where we can all learn something as long as everyone can keep a level head and not get all bent. Just sometimes those who are familiar with the subject have to let those who haven’t heard of it before work the ideas through their heads and get up to speed on it. Many times, like here, the initial thought is presented in one way, that there is 30mph worth of slip, and it seems so farfetched peoples’ initial reaction is that it’s BS, but once hashed out a bit we come to realize that the actual number is probably a fair bit less and the theory isn’t so farfetched after all.
By all means please stay engaged with the topic. The more you’ve opened up and given the info you’ve got the more it’s started to make sense how you’ve come to your conclusions and it’s helped the thought along.

 

All I will say is where did this 30mph of slip come from? I said 10% which is between 16 -17 mph on the speeds this bike is capable of. If your bike can hit 300mph well then you would have a bit more than 30MPH of slip but then those are not the speeds we are talking about.

As for your other thread, I still find it odd that someone with as much experience that you claim to have can't read a service manual.

Then As for opening up more, well when was I asked anything but to post links? No one asked any questions, just said I had to be wrong either with the theory or the numbers I used.

Add to it the gearing charts and top speed tests done with the same tire which show the error in speed is right at 10% or very close to it but still there is no way that I could be right


Also not one of the questions I asked was ever answered, so it did not feel like any type of discussion on my end, just a witch hunt.


Carry On

 

Your fist post in this thread. "The true top speed of a SH in in the 155-159 range. At these speeds the speedo will be buried well past the 180 mark." You went on to say the calculations say top of about 183 so yes I rounded up by 2-6mph.

As I stated in my other thread I didn’t see where it showed it in the manual, hence the question. Maybe I had just overlooked it. The manual I have access to is a scanned copy so the pages aren’t super clear, but I also looked on the fiche and couldn’t find anything about it there either, but you came off as a total *** in that thread.

You were asked for links. When you posted them I asked what the graphs were to represent as 100% slip seems to me the tire is going up in smoke. And how can you have 200% slip. I asked what these represent to better understand the graphs. I did give responses to many of your questions. But you just got bent and ignored them. I guess from your logic I could come to the same conclusion that you completely dismissed what I said just because you didn’t want to open your mind to it or other factors that could likely be at work and explain parts of your theory.

Again I apologize if I offended you before, now let’s discuss as adults and no pout off in the corner like children.

 

Trying to cool this thread down a bit.....

 

Is this kinda like the "I am sorry you are a (fill in blank)"? I think you have made it very clear that you aren't sorry for anything. Maybe it is just how I interpret this.

 

Visualizing a no slip physical world has been almost as fun as following this thread. lol

 

I'm right there with you......

 

How about a frictionless no slip physical world? nice!

 

true true

 

Guys all I wanted to do was post what I got the bike up to on the speedo on that day, not start a debate with what seem to be no end in sight. I know just about all speedo's are off from one degree to another. I also know there are other variables to take into account. But by using a gps is a damn good sure fire way to get a true speed. And that is what I am planing on doing. Also my top speed run wasnt from a standing start but from a 55 mph roll starting in 2nd gear.

 

I asked about the 30MPH figure because you stated that the slip was between 9-18mph in post # 13

I also state in post #7 that a completely stock bile will run out of steam at 9800 RPM which then implies that the top speed would be 174mph, sorry if that was to confusing.

Then you will notice in all my examples I state calculated top speed & true top speed as established by a radar gun. Not what you would read on the speedo.

In your rush to prove I have to be wrong I guess you overlooked that fact.

Also you have overlooked post #15 where rz stated that his speedo error was 7%. Now I don't know if he has stock gearing and by his stated tire size being a touch smaller than the stock 204 it does make sense his numbers are a little bigger than the 4% speedo error I have calculated.


So when you add the 4-7% speedo error to the 10% tire slip, yes the speedo will be buried past 180 MPH at the terminal velocity of the bike.

I will do the math for you.... at an indicated 185 if you subtract 14% (10%tire slip and 4% speedo error) you would have the speedo reading 25.9 MPH fast for a true speed of..... 159.1
If you use the larger 7% that rz noted then you have a total of 17% error so at and indicated 185 you would have an error of 31.4 MPH for a true speed of 153.6

 

Quote:

Originally Posted by 8541Hawk

I asked about the 30MPH figure because you stated that the slip was between 9-18mph in post # 13

I'm not the only one in this thread that's said I don't believe 10% is accurate and others have said tire slip doesn't exist. However you feel the need to single me out and slam me personally not only here but in other threads. I'm not sure what your deal is, whether it's just that I'm a newer member, or maybe you feel threatened or what. I think we've hashed out the he said she said b.s. enough. Let's get back to the facts at hand.

Something else I haven't seen anyone mention yet is, if this phenomenon is happening if you are WOT at a top speed of 158 actual and 175 indicated and you let off the throttle your indicated speed and RPM should drop down to less than 158 +- the percentage your speedo is off because now you are in braking slippage which would have a negative effect. It would be like if the clutch were slipping and you back off the throttle the RPM would drop as it catches again.

 

As most of your reply isn't even worth dealing with I will just touch on a couple of points:

I made my comments because you were throwing 30mph around as your proof I had to be wrong so if you did understand the radar gun why did you base your numbers on what the speedo says because this is what you said:

So not only were you taking things out of contest but you also decided to "round up" by adding to the true figure which really looks like an attempt to manipulate the data to try to prove I have to be wrong.

Another question, why is it that rz posted data (on offense, just an honest question) is taken at Gospel truth with no proof? I saw no video or picture or data download, just another member posting numbers. Then these numbers are used to say, once again, I have to be wrong. If I have to post exact numbers and have reams of proof why does no one else? That is why I said this conversation is a witch hunt not a discussion.

You asked where I got the tire size, From my Dunlop data. So its just like rz'z odo data..... you can choose to believe it or not, I no longer care.

So here is a question for you, lets see if you decide to answer for once.
Why is the calculated top speed 8.5-13% (depending on which figure you use, 174 or183) slower than what the bike can actually do? Before you start with it's the tire size, the radar tests were done with Dunlop 204's so unless you can prove they are a different size then why are the numbers posted wrong but others here can round numbers to suit there opinions or post data with no proof and it is taken as fact?