tire rollout

[chad502ex]

besides gearing for racing, has anyone else considered tire roll-out?

tire roll-out is the distance a tire travels across the ground with one tire revolution.

consider this,... all things being equal- that is the rpm the same on two quads, the gearing the same on both quads, and plenty of power to boot on both quads, and the riders ability excluded- which quad would cross the line first- a 450R with 18" or 450R with 22"? see my point? If you have the power to drive bigger diameter tires, and can sacrifice handling a bit- in a sense you are able to use the tires to put you out front.

18" diameter roll-out = ~56in.
22" diameter roll-out = ~70in.

Any input welcomed...

Formulas:

rollout = tire height X PI

wheel rpm = (vehicle speed / 60) X (5280 / (rollout / 12))

engine rpm = wheel rpm X rear gear ratio X transmission gear ratio

chad502ex.com

[quadrcr161]

back years ago when i was racing flat track, we always measured the tires at the same air pressure and put the largest one on the outside. we would also "streatch" the tire the week between the races by inflating it quite a bit and letting it sit.

Originally posted by chad502ex
besides gearing for racing, has anyone else considered tire roll-out?

tire roll-out is the distance a tire travels across the ground with one tire revolution.

consider this,... all things being equal- that is the rpm the same on two quads, the gearing the same on both quads, and plenty of power to boot on both quads, and the riders ability excluded- which quad would cross the line first- a 450R with 18" or 450R with 22"? see my point? If you have the power to drive bigger diameter tires, and can sacrifice handling a bit- in a sense you are able to use the tires to put you out front.

18" diameter roll-out = ~56in.
22" diameter roll-out = ~70in.

Any input welcomed...

Formulas:

rollout = tire height X PI

wheel rpm = (vehicle speed / 60) X (5280 / (rollout / 12))

engine rpm = wheel rpm X rear gear ratio X transmission gear ratio

chad502ex.com

that all depends on how long the drag is, we have messed with that a bit, the bigger the tire the more momentum you will have, giving your quad a boost on the top end speed compaired to the smaller tires which are lighter, allowing you to accellerate quicker

but technically if you have a bike that has a lot of power compaired to a bike with equal power, being that only tire size differs, it would all depend on how long the drag is, because in 300ft, you might not even make 5th gear if your bike is really quick, making you want to use the smaller tires to push you into the lead, being that you will never hit your top end, im guessing that the bigger tires wouldnt have enough length in the track to catch up

but yes i understand what you are saying, but im thinking its all dependant on how long the track would be

because think about it this way, you are hitting 4th gear in a 300ft drag, not able to hit 5th, with the lighter/smaller tires you will be able to top out in your gear faster then the larger tires would be able to, but at the top end of each gear the bigger tires would actually be giving you more mph then the lighter tires, but the light tires may be able to make 5th gear by the end, and you only make 4th because the bigger tires slow you down more because of more weight, while with the light ones you can rip through the gears faster

just my 2 cents :macho

[rodenberg35]

wouldnt changing gears do the same thing?

Originally posted by rodenberg35
wouldnt changing gears do the same thing?

technically yes, but in a different way, with the difference of tires its a difference of momentum while with gearing it controls where your power will be, it would be like compairing a cam to a piston...the cam will control where your power actually is, like gears, while the piston will add torque and power with the higher compression, while when you go down with it you will lose torque and power, its just the opposite with tires....bigger size=more top end smaller=more accel

[450ar]

xxx you have know clue.
Ok break down the whole point of gears.
they are there to change how many revs of the crank per distance distance traveled. Or how power strokes per distance travled. Or in simplest terms, they change leverage.

A tire will also change leverage. A small tire has more leverage then a larger tire.

Ok heres the prove.
A 18inch tire will travel. 56.52 inches per one rev of the axle.
A 22 inche tire will travel 69.08 inches per one rev of the axle.
maby you cant see it yet.

how about if we fit all the pieces together.
Is this demo. the crank will drive the counter sprocket for simplisty.
quad "a" and "b"
A 14t 38t 18
So for every one turn of the crank. the quad will move. 20 icnhes
B 14 38 22
will move 25 inches.
if you want a to have the same "gearing" then you would need
15t 34t 18in would move 24. 25 inches.

Now can you see how tire size has more effect on accleration and speed then the gears do.

Originally posted by 450ar
xxx you have know clue.
Ok break down the whole point of gears.
they are there to change how many revs of the crank per distance distance traveled. Or how power strokes per distance travled. Or in simplest terms, they change leverage.

A tire will also change leverage. A small tire has more leverage then a larger tire.

Ok heres the prove.
A 18inch tire will travel. 56.52 inches per one rev of the axle.
A 22 inche tire will travel 69.08 inches per one rev of the axle.
maby you cant see it yet.

how about if we fit all the pieces together.
Is this demo. the crank will drive the counter sprocket for simplisty.
quad "a" and "b"
A 14t 38t 18
So for every one turn of the crank. the quad will move. 20 icnhes
B 14 38 22
will move 25 inches.
if you want a to have the same "gearing" then you would need
15t 34t 18in would move 24. 25 inches.

Now can you see how tire size has more effect on accleration and speed then the gears do.

most people have no idea what you just said, im just trying to simplify it out for them in a way to understand it much easier, you dont have to critisize me with every statement i make when you are unaware y i made the statement

[kgbg]

LMAO!
Chad,
Roll out is a very critical factor for allthe sand hil shooters.
I run a 69" roll out on tire, currently, but do not have much data saying that its the best choice, yet.
One interesting thing about roll out is that it is not actually tire height x 3.14 (EDIT tire height on the tire, not measured). Wheel width has a large effect. Wheel speed has a big effect. A 22" tire on a 8" wheel has quite a bit of room to grow as it speeds up. Just am assumption, but I would guess my 22" on a 8x8 wheel (double buff, trip. would "grow" more), when the engine is at 9000RPM's are more like 71" rollout. SO if one were to get super technical on it, you would have to consider what wheel speed you wanted what roll out at.

[aci clay]

u guys are all forgetting how much wheelspin and traction makes in determining acceleration. most of the time its not top speed but corner to corner acceleration that wins races.

Originally posted by aci clay
u guys are all forgetting how much wheelspin and traction makes in determining acceleration. most of the time its not top speed but corner to corner acceleration that wins races.

no no no, hes talking about a drag race, not a actuall race i believe, but if he is thinking actuall race then ya your definantly right

[ThumPIN_450R]

22's will not work on an mx track they sit way to high and will never get through the center of the turn no matter what the roll out is if you can get throught the center of the turn faster you can come out of the turn faster which in turn lets you start down the straight away faster which will give you more speed all the way down the straight into the next turn too do it all again. In drag racing rollout may be the most important thing with tires but in mx traction and handling are the most important thing to me and a 22" tire will not ever handle like an 18

[chad502ex]

Originally posted by 450ar
xxx you have know clue.
Ok break down the whole point of gears.
they are there to change how many revs of the crank per distance distance traveled. Or how power strokes per distance travled. Or in simplest terms, they change leverage.

A tire will also change leverage. A small tire has more leverage then a larger tire.

Ok heres the prove.
A 18inch tire will travel. 56.52 inches per one rev of the axle.
A 22 inche tire will travel 69.08 inches per one rev of the axle.
maby you cant see it yet.

how about if we fit all the pieces together.
Is this demo. the crank will drive the counter sprocket for simplisty.
quad "a" and "b"
A 14t 38t 18
So for every one turn of the crank. the quad will move. 20 icnhes
B 14 38 22
will move 25 inches.
if you want a to have the same "gearing" then you would need
15t 34t 18in would move 24. 25 inches.

Now can you see how tire size has more effect on accleration and speed then the gears do.

very good info here.

Kam,
I hope you were not "LMAO" towards me! I was only interested in drummin up the point of tire size pulling the vehicle ahead of the pack if the rider can find some balance of all the variables (being gearing, tire diameter, skill, ect). You point in tire swell was something that i hadn't concerned, but centrifical force on tire would definitely change roll-out. It's probally why dragsters tires are so big up front and in the rear, huh?

[kgbg]

Nah, I was LMAO at the wrong info being offered above.

I am going to get a chance to try some 72" and somr 67" roll out tires on Memorial day weekend.

[chad502ex]

Originally posted by kgbg
Nah, I was LMAO at the wrong info being offered above.

I am going to get a chance to try some 72" and somr 67" roll out tires on Memorial day weekend.

kewl!

Ya the 530R with EFI and turbo has 72" rollout tires too!

;)

[450ar]

I tried to keep it simple and leave tire growth out of it, And i see that there is a differnce in termimalogy, which can be expected, since alot of us are on different parts of the country.

Tire growth is kinda like adding an variable ratio gear. the higher the speed the larger the outside, and increase in topspeed. while at lower speeds it stays smaller to give you more torque.

Originally posted by 450ar
I tried to keep it simple and leave tire growth out of it, And i see that there is a differnce in termimalogy, which can be expected, since alot of us are on different parts of the country.

Tire growth is kinda like adding an variable ratio gear. the higher the speed the larger the outside, and increase in topspeed. while at lower speeds it stays smaller to give you more torque.

wouldnt tire pressure come into play also then?

[chad502ex]

Originally posted by XxHonda_RacerxX
wouldnt tire pressure come into play also then?

yes, on the front and rear

[shaneb]

In the sand the tire roll out (diameter) makes a big diff ...

With a big dia tire you get two nice things.
But you also need to had a narrow rim so that your tire top is round and not flat

One the tire will tend to dig less and it will stay on top of the sand. I also think that having a curved paddle(becuse the tire top is round) gives your a better bite into the sand

Two as your speed increases the tires can float up out of the sand. And becuse your tire is round as the tire floats out it pulls the paddles our of the sand (becuase your tire top is round)

Also the longer rolout give you traction with the penalty (top end drag) of an extra paddle


Here is another fact. I would guess you only need 4 times the traction to get out of the hole compared to when you are moving.

The setup above is about as close as you can get variable traction tire


my setup: 505ex 8 paddle 22x12x8 on a 6 inch wide rim.

I have a 4 inch arm and I groved the paddles down to half height.


This setup give me a competeive launch with the bikes that race on the hill at dumont and glamis