Don Walker's 2008 R6 low side crash analysis

I have both your dvd's and study them religiously!!! I have actually gotten pretty good at dialing my own suspension due to your clear explanations and demonstration of how a motorcycle suspension works.

I am writing you because i have a weird problem I just can't figure out. I am an avid rider and have 3 track days under my belt. I recently purchased a 2008 r6 and while riding it after setting sag, rebound, and compression I noticed that the bike will lean over to a certain degree and just stop. Now by this point I am not low enough to drag knee. When I try to lean the bike more it feels "squirrelly" if you will.

I tried leaning it more and more and alas I low sided. As I got to certain lean angle the bike just wouldn' go any further. I had to put some effort into making the bike lean over more. At this point the bike felt squirrelly and just fell down. It was more of a feeling that the bike just fell down as opposed to sliding away from me. I was wondering if you had any idea what causes this.

If you are too busy to offer any advice I totally understand. Its just that i hate getting advice from "know it alls" and would rather get some honest input from someone who understands motorcycle dynamics. Thanks!

REPLY

Hi Don,

Thanks for the email and the detailed explanation of what you are feeling with the bike in regards to lean and the good understanding you have of what happened when you low sided. That is the key part to understanding what happened and why.

When you set preload and compression too soft the front forks drop to a certain point and then cease to move. When that happens, the tire becomes the suspension and if you lean the bike too far you overload the tire, the side wall and then the edge collapse and the bike low sides falling in the direction of the turn so that you fall on it so to speak.

If the bike had gone away from you the low side crash would have been from too much gas taking weight away from the front wheel causing it to skid out away from the direction of the corner.

There are many other variables here, but I would reset your fork sag to 35mm and set the blue compression (low speed) to all the way shut and come back 12 clicks. Start with this settings and see how the front behaves.

NOTE:
1. If the rear sag is too tight it will shift the balance of the bike forward and drive the front wheel into the ground rather than along it. Check rear sag, including free sag to remove this from the equation.

2. If you have a larger than stock rear tire in place, this will pick the back of the bike up and change the balance point of the bike too.


SECOND EMAIL:

DON:
Hi Don,
Thanks Mr. Moss. I think I know what happened after reading your explanation. I checked my suspension again and rechecked some measurements. I had my front sag set at 28mm with really soft compression. So....tell me if this is right. Maybe my preload was too stiff with really soft compression turning the tire into the suspension. Basically with the fork preload being so high the front had no movement and with the soft compression it was "bottoming out" I did have a zip tie on there and the front travel had about an inch left, but I think because my preload was so hard that is what cause the problem. I'll try reseting the bike to your suggestions and let you know what happens.

Thanks Dave!


REPLY:
Hi Don,
Yes, that would be a very concise explanation. Too much preload (should be 35-38mm) with low speed compression at 16+ out would cause the forks to drop to a set point and then the tire is what you have for suspension. Once you overloaded the front tire the bars turned in and the low side happened.

You need to have the zip tie go to about 1/2 and inch left for street use.
Seems you have learned a great deal fro the DVD's!