profile and ground speed

[Corpsedealer]

does anyone know what the speed diference is between the standard rear profile and the next up? sorry cant find the piece of paper with sizes
on it.

[Batfink]

do you know the change in outter diameter? if so I could quickly tell you the spped change ratio

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if I have worked it out right then its for a 180/55 17 profile tyre the outter diameter should be:

(180x.55) x 2 = 198 + (17x25.4) = 629.8mm dia

the final hieght is determined by the 2 numbers 180/55 as it is the ratio of height to the width of each profile

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while a 180/50 17 tyre would give the final outter diameter of :

(180x.5) x 2 = 180 + (17x25.4) = 611.8

this means that if speed is set right for 180/55 then the 180/50 profile would be about 3% less in speed as each rotation is about 3% less in circumference which is 3% less movement forward

[Dale]

Corpes .. I think you will find the speed difference between the 50 and the 55 profile is probably less than the amount that the busa speedo is out anyway. The busa speedo reads fast as do all speedos I'm led to believe. In theory the 55 profile probably puts you a bit closer to the speedo reading than the factory 50 profile does. I could be wrong in my theories and I'm sure the masses will chime in and tell me so
The difference is in the handling and there is a thread on here somewhere discussing this. I prefer the 50 but others prefer the 55 .. each to their own.
Either way, the busa goes fast with a either a 50 or a 55 ..

[BikerBoy]

Corpse the difference is quite small - aprox +5km/h (on paper).
On street it's irelevant - PSI, compounds, friction, temps etc...change the equation.

If you're talking speedo accuracy - mines a +2T rear sprocket with a 55 profile and my speedo is +3km/h out (stock was +9km/h)

the http://www.gearingcommander.com/ website is good for figuring out this sort of stuff.........when Tony is offline and out riding

[Corpsedealer]

Thanks guys that was were I was heading. As I have lots of no riding time thanks to my own stupidity And the fact the Busa needs new rubber I thought that I might get the speedo closer as well, and the slight loss of take off speed wont hurt with me on it as I weigh absolutely nothing (me and bike 300kg MAX)

[Batfink]

So the gen 2 runs a standard rear 190/50 17?????

If you go to a 200/50 your actual speed will increase 1.6% while going to a 190/55 profile will increase 3%.. If you went all out to a 200/55 ( not sure if suitable) then you will have an effective total increase of about 4.8%

[Dale]

Tony, how do you come up with the extra using a 200 wide tyre?

Are you allowing for the bigger "bow" as you try and fit it to a standard rim.

If you used a 10mm wider rim wouldn't you get the same answer as a 190 on a standard rim ?

[cyndemgum]

Tony, how do you come up with the extra using a 200 wide tyre?

Are you allowing for the bigger "bow" as you try and fit it to a standard rim.

If you used a 10mm wider rim wouldn't you get the same answer as a 190 on a standard rim ?

Dale, google tyre aspect ratios and you will get the answer. Paul.

[Batfink]

Tony, how do you come up with the extra using a 200 wide tyre?

Are you allowing for the bigger "bow" as you try and fit it to a standard rim.

If you used a 10mm wider rim wouldn't you get the same answer as a 190 on a standard rim ?

The height of a tyre is in the profile numbers.... The first number refers the the widest part of the tire, not the rim width which for a 200/55 is 200mm and for a 190/55 is 190 mm etc.. The second number is the ratio to get the height eg 55=55% so the difference between a 190/55 and a 200/55 is

((190x.55) x 2 ) + (17x25.4).... This will work on a spreadsheet if all the brackets are confusing

((200x.55) x 2 ) + (17x25.4)...

I had to do some of the working out in my head cause I hate the iPads calculator so sorry if my final % is out.. Lol

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Tony, how do you come up with the extra using a 200 wide tyre?

Are you allowing for the bigger "bow" as you try and fit it to a standard rim.

If you used a 10mm wider rim wouldn't you get the same answer as a 190 on a standard rim ?

Dale, google tyre aspect ratios and you will get the answer. Paul.

I should read before every answer LOL. Thanks mate

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I might love numbers but I can be slow... For something interesting to all you dragsters

If you bike can handle a 5% increase to load changing to a 200/55 rear tire can effectively take nearly half a second off a 10 sec run....

[Dale]

Tony, how do you come up with the extra using a 200 wide tyre?

Are you allowing for the bigger "bow" as you try and fit it to a standard rim.

If you used a 10mm wider rim wouldn't you get the same answer as a 190 on a standard rim ?

Dale, google tyre aspect ratios and you will get the answer. Paul.

Well, there ya go ..
I always thought the 50 / 55 was "mm" in height, goes to show .. we are always learning all the time .. Thanks Paul (and Tony)

On a note .. I had a closer look at the numbers on my Michy PR3's .. The maximum load says 365kg .. My busa and me are nearly that, so what is the score when I put the mrs on the back?

[Corpsedealer]

Thats cool Dale I thought the 50 in 190x50 was the tyres wall height!
and some good mates of mine run a tyre business!!!!

[PostmanPete]

Thats cool Dale I thought the 50 in 190x50 was the tyres wall height!
and some good mates of mine run a tyre business!!!!

It is...... 50% of the 190mm width? Did I miss something?