New tire inceases top speed !

...a new, properly inflated tire has picked up a good 5mph in top gear...

...I don't know what that is in kph...

...I didn't notice stuff like this riding the Hayabusa(s)...

[ophic]

Originally Posted by Hapo

...a new, properly inflated tire has picked up a good 5mph in top gear...

...I don't know what that is in kph...

...I didn't notice stuff like this riding the Hayabusa(s)...

Probably more to do with the change in radius of the new tyre than any actual difference in speed. The speedo pickup is on the front wheel.

Although thinking about it, a slightly larger radius would read a slightly lower speed wouldn't it? As the circumference is slightly longer therefore the wheel would turn more slowly at any given road speed.

So it's 5mph + a bit!

And no-one cares what it is in kph...

[Bibio]

simple. busa has speed sensor on front sprocket, sv has speed sensor on front wheel. your new tyre is taller than your old one.

[ophic]

Originally Posted by Bibio

simple. busa has speed sensor on front sprocket, sv has speed sensor on front wheel. your new tyre is taller than your old one.

Would cause an error in the wrong direction.

[Bibio]

my speedo runs off the rear wheel and as the tyre wears down the speed decrease. with a fresh tyre its pretty much within 1mph lower than spaznav with old tyre its around 3mph lower.

either that or with the OP fitting a new tyre on the front has eased off the sensor drive so now showing the correct speed. thats if the OP has fitted a new front tyre.

[SV650rules]

Originally Posted by ophic

Would cause an error in the wrong direction.

That is very true, wheel would rotate more slowly for same road speed if circumference increased.

We are assuming Hapo went for same profile - if he went from a 120/70 to a 120/60 that would reduce rolling radius by a few %, If a different brand may be a bit flatter profile as well.

[ophic]

Originally Posted by Bibio

my speedo runs off the rear wheel and as the tyre wears down the speed decrease. with a fresh tyre its pretty much within 1mph lower than spaznav with old tyre its around 3mph lower.

That's a bit odd. As your wheel radius gets smaller, you'd have to maintain higher rpms to keep the same road speed in any given gear. Therefore, assuming all else is the same, the bike speedo should read higher with an old tyre.

If Hapo has changed his rear, that might account for it. Slightly higher gearing?

...I am running the same front...I have degraded my riding to the point where I now wear out the rear to front in a two to one ratio...

...the bike is just going faster...it is indicating a full 5mph more than before...

...I used to wear out the front tire more quickly than the rear, cupping it badly by being greedy with the brakes...

...I also tend to crash bikes the same way, cupping them rather badly as well, so I try to quit that **** these days...I have not even warped the stock rotors yet...!!!......

Originally Posted by Bibio

simple. busa has speed sensor on front sprocket, sv has speed sensor on front wheel. your new tyre is taller than your old one.

...well, yes...it is just that it make a much more noticeable difference compared to what I am used to or remember...

...I thought the difference/effect would be more theoretical than noticeable...

...being an actual (glorious Yankee *******) road criminal, the actual facts will not be theoretical, nor unnoticed/tested...

...in fact, the roads are warming up nicely, so please excuse me whilst I do a bit more testing...

...was that last bit all proper n' ****...???...

[Bibio]

change the height profile of the new tyre http://www.tyresizecalculator.com/ty...ror-calculator then look at the actual speeds. a 70 profile will give 103 a 60 profile will give 97.

or i could be wrong and my speedo is lying.