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Motorcycle Geometry – Steering vs. Grip

Something I learned in a bit more detail this year was the compromise and trade-offs between steering and traction. The ability of the bike to steer quickly versus the traction available at the rear of the bike and how that is affected when making geometry changes. There are a number of variables in dialing in suspension, but I like the idea from a very generalized standpoint of isolating geometry from suspension damping. Yes I know they're all intertwined together in some regard. However to try and keep things simple, I've wanted to find a geometry setup that works and then use the clickers (damping front and rear) to fine tune the bike from there. Every bike is different and each rider rides differently, so there's no correct answer that applies and works for everyone in this regard.

Since 2007, we've generally had the bike setup fairly aggressive; meaning that the rear was jacked up, standing the bike on its nose in a sense. This jacking up is done by adding rear ride height to the shock, in effect making it taller which puts more weight on the front of the bike. From a general standpoint this helps the bike turn quicker. Getting into turns and also finishing turns where you can get into the throttle sooner and get out of the corner sooner - accelerating to the next turn with more speed and an overall faster lap time. This can help solve a common problem of being leaned over too long waiting for the bike to turn and losing time because you can't get on the throttle quick enough.

Of course this a compromise. The downside to an aggressive geometry is that the bike can become unstable and twitchy. It's potentially not as balanced throughout and can make the bike harder to ride – sapping both confidence and speed. One thing I noticed more this year than previously, was that on the new R6, as we increased the length of the shock the connection I had to the rear of the tire (grip) wasn't there. The bike either felt unstable, unsettling, or just plain confidence-uninspiring when trying to get on the gas. I wasn't able to notice this until we had changed it, where there was an improvement in how that part of the bike felt.

We started the season off very aggressive compared to other guys running the same model bike. A long shock length and a significant amount of fork showing above the top triple clamp (which in effect drops the front-end down even further) was where we started. As we continued to work on the bike throughout the year, we took some length out of the shock and in essence, flattened the bike out a bit. At first I thought we had gone too much, as the bike didn't turn nearly as well as it had previously. We later split the difference and found what I thought was a great setup. The bike was still turning well and I could feel an improved amount of traction when getting on the gas. That coupled with acquiring the correct front springs by the end of the year really made the bike even easier to ride.

As we made these geometry changes, the rear grip was so improved in fact that I'd say I wasn't used to it. The '05 R6 we ran (a completely different bike altogether) was setup very aggressively. Looking back, so aggressive that I rode the bike a certain way because of it. Don't get me wrong – it was great. Just different. With the '08 R6, it's lighter and more nimble, so I think it can turn just as well without being over the top in terms of an aggressive geometry setup. This now means that I can get on the gas harder than I've been accustomed to without the previous issue of the rear tire stepping out. It's all very smooth and confidence inspiring. This point is confirmed when I look back at both 2008 and 2007. This past year, granted I had limited track time – but I had ideal/perfect traction nearly all the time. In 2007, I didn't. The bike moved around a lot more, sliding at times where I became comfortable with it – which is what's needed the faster you go. Lap times between the two bikes were very similar and in some cases, I went faster than I did on the old bike, while riding less aggressively than I did on the old bike. I'm sure you can see where I'm going with this ..

One point Garry brought up that made a lot of sense was how the geometry of a bike can affect your riding style. If you've seen any pictures on here of me, I'm generally not cranked over on the side of the bike compared to some. I'm more upright and I criticize myself all the time by saying I need to get my head out more and off the center of the bike. To the contrary, you see someone like Blake Kelly and he's cranked so far over off the bike, he looks like he's going to fall off it. Part of that I think is related to how the bike is setup. With a bike that steers sharply, you don't have to use your body to steer the bike quite as much. When the bike is more balanced and takes more work to steer, you've got to do everything you can to turn the thing – get up on the bike, get your knee out, head out, elbow out – whatever you can to turn the thing. As Garry pointed out, when you watch many of the AMA regulars, they're running a flatter bike in a sense, which gives better traction. In turn, they're cranked over just to turn the bike and get it around the track faster. It's a worthwhile trade-off primarily because of the added rear grip you get with a balanced motorcycle to drive hard out of the corner.

Of course you still need the bike to turn. The rider can't do it all himself. If it's wallowing or chattering, or doing other things that don't let it finish the turn, there's a whole other series of questions that go with that. I'm not a suspension expert by any means, but this is just based off my experiences. Usually at this level there's no guaranteed single answer to any suspension/chassis dilemma, but if nothing else, I feel I was able to better understand this relationship of steering versus grip throughout the year and can hopefully apply it to my own riding for faster speed and improved lap times next year.

Friday, October 24th, 2008 | POSTED AT: 6:15 AM
FILED UNDER: General