For those who mount their own tires ... important!

[ALANRIDER7]

Ufck oyu.

 

[Roundboy]

OHhhhh SHooot Alan!!! I forgot to tell you all the jokes I pulled at your shop the other day....like all the bolts I loosened and tools I hid..... uh maybe you should call me dude......like ASAP

 

[elskipador]

wow.......i get back from a week @ road america and this is what i see . i woulda' posted sooner, but you know i was, a, working @ the race track with a lot of the fastest guys in the country. so where to start? where to start?....... the beginning i guess. pete your mathmatical explaination is so over simplified its funny. you assume a lot of stuff that i know to be incorrect, from a real world stand point. 1st...by keeping the angles of the valve & wheel heavy spot @ 0 & 90 you've managed to keep both vectors in the positive grid. makes the math easier but isn't a good assumption to make as that isn't the case. you might have known this if you balanced and mounted as many tires as i have. usually on a aftermarket 16.5 wheel the light spot is between 170 & 190 degrees from the valve seem. on a OEM 17 in wheel its usually between 140 & 240. the quality on the OEM stuff isn't near as good as it is on the aftermarket stuff.
2nd.... you really need @ 3-d vector set up as this is only a problem when the wheel is rotating and the bike is moving. so you'd need a x,y & z. not just a 2-d vector.
3rd.... 15 degrees is a pretty slight spin. 30~60 is a much more problematic wheel spin. @ 30 degrees on a 16.5 rim the arc length of the spin would be 4.28~4.36 depending if the rim is a true 16.5 or a "undersized" 16.5. 2 seasons ago jake zemke spun a front almost 180 degrees.
4th.... you really have made this issuse seem so simply. however even @ a slow speed of 120mph the wheel is rotating @ around 256 ft/s @ that speed it takes only .025 seconds for it to complete 1 full rotation. your example doesn't even begin to touch on the complexities of whats going on out on the race track @ speed.

now since you consider yourself a "scientist" i would think that you would be familiar with the scientific method. http://www.pages.drexel.edu/~bcb25/scimeth/intro3.htm you do really well until you stop after step 3. you have no real world data......none. i highly doubt you can even recreate whats happenning out on the track when a rider spins a rim. but thats not really the point. the point is that just because you do a little paper work you think you've proven something. however you need to go back and do steps 4 & 5 of the method to really "prove" something.

i also find it funny that you question my education. i have a high shcool degree, as well as 2 college degrees. and yes pete i took physics in college, 4 semesters of lecture and lab. now i'm not gonna' try and say i was some great student, as i was usually in the b- ~ c+ range in lecture and a b ~ b+ in the labs. however i only took the stuff because i had too. pretty much the same on the math, though i had to take a lot more. i talked with a lot of the factory guys over the week about what they new about physics and i wasn't amazed by what they told me. ben spies superbike motor tuner jokingly said "i made it through the 11th grade....i think" he then told me he didn't know a lot about physics, as he was taught, in the real world, by other techs. steve may not be able to explain this and that in relation to physics, but he can make 1 of the most power superbike motors in the AMA. duhamel's motor tuner told me he barely made it through highschool, and math was never his strong point. he to can build a motor like few in the paddock. the other motor tuner and R&D guy did know a bit of physics, but said most of the time he just used computer programs to do the problems for him. he called it cheating.hayden's motor guy pretty much said the same thing, adding that most of the guys in the paddock came up the ole' skool way.....working and learning @ the track. he did say that from what hes seen the car world is where the physics and engineers are. the head mechanic for marty craggil said he didn't even need physics to build a good motor. the chassis guys where a little different, knowing a lot more trig and geometery, but physics was still not very common. so your insults seem a little off based as most in the industry don't even have college degrees.

now maybe i should have explained when we started doing this practice. it was @ laguna seca in 03 the 1st time i saw it. only on the world superbikes, which @ the time were going faster that the AMA bikes. i'm sure you know way more than that of the tuners @ the world superbike level, but i don't and accidentlly removed a rim balance weight. it was explained to me in laymens terms that it mattered. the 1st race of 04' we got the word from HQ to balance all the rims before mounting tires on them. that really sucked as we had to balance 500 some odd rims then mount tires and rebalance them. this is now the 3rd season of doing it and out in the real world it works. your little chart will not convince me otherwise, since, well, you have absolutely zero real world data to back it up.

i've got some pictures to go along with this story to back up what i say and raise a couple of new questions.....

 

[ALANRIDER7]

 

[elskipador]

ok the 1st pic is of a 16.5, i believe a JB-magtan. its a balanced rim, notice the silver spot on the left of the wheel, by the orange direction arrow. its a 7gram square, our weights are in 7gram chuncks. we started using special wheel weights this year. yes, i said special. some super adhesive stuff. takes the several hundred degree temps on the wheel surface. anyway i've been trying to get every single rim balance switched to the new style for the last couple of races. this pic shown the rim @ "settled" position. the heaviest spot @ the 6 o'clock position, the lightest spot @ 12 o'clock. notice that the tires yellow dot, light spot mark is @ the 3 o'clock instead of the 12. why? cause the tires are mass produced and a certain percentage will always be off. my CBR's cam timing was quite a bit off from the factory and its just a part of life. so if you end up with this tire and use petes method you may actually end up using more weight, depending how far each is off and the distance from the points. not to mention that if anything happens and somebody crashes the first thing they'll notice is the tires being "improperly" mounted. that'll be great for the insurance guys

 

[elskipador]

then i mark the true "light spot" its the gold mark @ the 12. the pictures tilted a little bit, as you can see from the horizon

 

[elskipador]

it took roughly 2, 7 gram, squares to balance. along with the other 7 gram rim balance. so about 21 gram total, plus the 1.5 inch duct tape.

 

[elskipador]

next i jerked the rim balance weight, and tape off.

 

[elskipador]

then i re-balanced the whole package with just a "tire" weight. it now took 4, 7 gram, peice, thats 28grams total. pete's "math" says i should always use less, but in the real world that isn't always the case.

 

[elskipador]

however that was the odd ball. i repeated the same thing with 3 other rims. of those the 1 above was the only 1 to take more weight, when the rim and tire were balanced as a package. the other 3 required the same total weight, just split, and the 12 o'clock position moved a slight bit. never once did the rim balance method have more weight total.

 

[elskipador]

heres a couple more pics of tires that the true light spot is not quite perfect. a lot of them are, but there is a margine of error with production and such.

 

[elskipador]

another odd thing that happens from time to time when balancing is that the heavy spot will actually settle @ the 12 o'clock. i really have no idea why this happens and couldn't get it on film, as you only know its happened once you move it to check and then it will always settle in the normal way. i think we did 2000~2200 balances over the week, theres 3 of us. i saw it happen twice.

the point i'm trying to make is that pete's over-simplified example doesn't come close to actually explaining whats going on @ speed, and doesn't take into account the oddities of production and manufactoring. and therfore pete shouldn't go around giving what he calls important balancing information about a product he has no ties to. if you want to do it right do it like the pros in the industry do.

for anybody in this thread that said those over @ dunlop are slackers...... are you kidding me? slackers?!?! right. 18 superbike championships, pretty much total domination of the AMA road-race seriers, 250 gp, world-superbike (before the pirelli spec thing) and making gains in moto-gp. hell even in the AFM and WSMC we have a great record for wins. you seriously think this comes from a bunch of slackers? puhleeze

 

[bxr140]

another odd thing that happens from time to time when balancing is that the heavy spot will actually settle @ the 12 o'clock. i really have no idea why this happens...

My guess is it was spun at just the right speed to "stop" at the 12'o (effectively no "moment" around the axle), and there was enough friction in the system to hold it there.

Two questions: 1, When you "re-balanced" without the wheel-only weight and found that you needed more weight, did you re-position the tire so the light dot was at the true "heavy spot" of the rim? Or did you leave the dot at the valve?

2. Does any of this really prove the initial post "wrong"?

 

[elskipador]

i left it there. yeah what would have happened had i put the dot where the light spot on the rim was? considering that the tire in questions has the real light spot close to 45 degrees from it?

 

[bxr140]

i left it there. yeah what would have happened had i put the dot where the light spot on the rim was? considering that the tire in questions has the real light spot close to 45 degrees from it?

I don't know, that's why I'm asking.

Unless I missed something, that was the original point of the original post.

 

[elskipador]

Unless I missed something.

yeah the fact that the little yellow dot isn't always the lightest spot.

 

[TWF]

yeah the fact that the little yellow dot isn't always the lightest spot.

so,what is yellow dot for and why?

 

[pvd]

skipzilla-

it would really have helped your argument out a lot more if your example illustrated something other than the limitations of you balancing technique.

1. assuming that the minimum balancing unit to be 7 grams is downright comical given the level precision we are talking about in this thread.

2. i'll be the first one to admit that you are probably exeptional at predicting the approximate location of a balancing weight and it's approximate mass, but you are not not nearly as precise as would be required for your example to have that much merit (especially combined with point #1)

a dynamic balance, computer postitioning, and weights at least down to the gram would do the trick. oh wait, you guys don't do that! that means that you are doing a 'good enough' job. i wonder if this is createing most of the problems that you keep talking about? or is it the fact that you can't keep the tire from slipping on the rim? it's a bit of both of course.

now, with regard to your other points regarding 15 degrees of spin not being enough to show what really happens to a balanced wheel when the tire spins. i used 15 degrees since it would give some good mixed expressions and odd degreees. of course, we know without thinking what happens at 180 degrees of spin. don't we? i figured that you may be a little out of practice with the rudementary arithmatic so i even posted a graph and the equation in a prior post:

without focusing at all on the other foolishness that you may want to consider removing (kinda makes you sound silly), we come to this statement:

yeah, the fact that the little yellow dot isn't always the lightest spot.

this being the case, of course, and you knowing this, you still felt the urgent need to come down on my post about basic backyard tire balancing? so what was the point? really?

your point was, not that what i said was wrong, but that you were jeolous that i posted something like that before you and for that you tried to bring me down. that is truely low.

re-read this whole thread. you deserve us all an apology.

 

[daventura]

In before the lock.

 

[afm199]

Pete: Your'e a self appointed expert. Skippy is paid to be one. Guess who I want working on my bike.