Skills: Keith Code on Traction

[Captain]

He stops a little short (he has a course to sell) but interesting nontheless:

http://i3.photobucket.com/albums/y93/GBM2004/Traction.jpg

[lilninja]

Nice find Captain although it doesnt really tell us all that much but I love reading keith code articles so I enjoyed it.

[RIPPERTON]

Heres a 3D model of rear tire geometry that I knocked up a couple of years ago and unleashed it on the Oroads crowd.
It was mostly shoulder shrugging but its cool to ponder for the mechanically minded at least.
It may explain the extraordinary lean angles of MotoGP bikes.
Or it may not.

http://i37.photobucket.com/albums/e62/ripperton_2008/REARCONTACTPATCH.jpg

http://i37.photobucket.com/albums/e62/ripperton_2008/REARCONTACTPATCHcrop.jpg

http://i37.photobucket.com/albums/e62/ripperton_2008/REARTIRECONTACTPATCH-1.jpg

http://i37.photobucket.com/albums/e62/ripperton_2008/REARTIREWIREFRAME.jpg

http://i37.photobucket.com/albums/e62/ripperton_2008/REARCONTACTPATCH-2.jpg

[Zee]

How'd ya figure out the contact patch dimensions, Rip? ...so many variables, isn't there...guess ya just use averages aye? but still, without a physical foot print, that would be a bitch to calculate...with deflection and all. Looks impressive!

[Loco976]

very nice to ponder indeed

appreciate the work, thanks man

[RIPPERTON]

How'd ya figure out the contact patch dimensions, Rip? ...so many variables, isn't there...guess ya just use averages aye? but still, without a physical foot print, that would be a bitch to calculate...with deflection and all. Looks impressive!

The shape of the contact patch isnt really what Im getting at here and yes there are a lot of variables.
The main point is the fact that the rear wheel is actually doing as much turning as the front wheel.
Its a fluke that it happens because whoever decided long ago to put a fatter tire on the rear probly had no idea that it was going to tilt the rear wheel axis like it does. They were just thinking about more traction.
BTW Im trying to find Keith Codes Email. Anyone know ?

[jasonbw]

I think with stuff like that you should talk to someone like Greg, who owns GMD computrack, he's a genius when it comes to motorcycle geometery and he's in Sydney. Google his name, it'd be interesting to hear his thoughts on that.

Have I understood this right, during cornering the rear wheel is distorted approx 1 degree into the turn?

P.s. Nice find Capt'n, if anyone would like to read more of Keiths work pop into his site, linked off this post: http://www.nswroadandtrackbikes.com/forums/showthread.php?t=2706&highlight=bands+traction

[Captain]

Brilliant Jason, thanks :ayyy:


Everyone wants to have the stickiest rubber they can afford but it isn’t sticky until they can put the big load on the tires. Most riders would do better and learn heaps more about traction with something lesser than full race, factory rider developed tires. Why? They don’t have to put the big loads on the tires to start to experience the bands of traction as listed above.

I remember changing tyres on the ol' blackbird. The OEM's were shit, and getting worse and I went over to a new set of Pilot Powers. I remember thinking that in some ways I preferred the old ones, they were more 'predictable' in that they would slip and slide, and they did so at relatively low speeds so that they 'tempered' the riding - whereas the new better tyres had a more 'violent' behaviour. With the old crappy tyres, I did in fact get some practice in handling the bike whilst the rear wheel spun (under acceleration). The new tyres, on the other hand, if they ever slipped (bump in the road etc) not only were the speeds and acceleration higher, but when they gripped they did so very violently. Does that make sense?

I think Keith expresses this well.

[Captain]

I wish we had more technical / technique posts. Anyone has anything else?