xeris

I want to fully understand what happened and why. I really want to learn from this as I never want to come close to this on the street again.
Just finishing an S turn to the left and I encounter a radar trap (no indication of radar signal, but going fast enough to get noticed). I'm still leaned over some just past the apex, I over react a bit and get on the front brakes a little too abruptly. Apparently not hard enough to low side, but I'm not really conscious of everything as it was happening, although I do remember the tire(s) howling. The bike then instantly stands up and I get a very scary tank slapper. I really thought I was going to go down. I did not, the cop must have been looking elsewhere so I got to go home and wash my pants.
I drove by a little latter that morning and there was a 5' long skid mark right where the fun started.
So after thinking about it for a day and a half I've concluded that I was on the rear brake (too hard) and locked the rear wheel, the rear stepped out and when I regained traction I almost high sided. Does analysis sound right?
The other question is about the strange marks on the front tire. I'm guessing they are a result of the tank slapper. I think I should check the wheel alignment. This is new to me so tell me what you think. The tire is rubbed pretty good leading up to a faint patch of red (I'm guessing Italian Red), two cuts with a thin tag of rubber on one of them, followed by a silvery smear. It is on the left side of the front tire. Did the tire and forks flex enough to make contact? Like I said I want to learn from this so any help would be greatly appreciated.

jerryh

Great job hanging on to it!

quillinsmat

i'm no expert but that sure looks like a paint smear to me. Is there any marking on the inside of your fender?

Jonar

well it seems you didnt get over your chicken strip, so my guess is cold tires (?) and some sharp weight shifting (S turn and hard braking). With these marks on the front tire I dont think you locked the rear, there are many ways the rear can step out, locking -imho- is by far the most controllable and memorable. Looks like the front lost traction first, then regained, resulting in the tank slap.

xeris

I've looked under the fender but can't see any marks. I pretty sure there is, but will have to remove the fender for a good look. Seems clear that the tire rubbed on the fork and fender. Curious about what moved enough to cause it. I don't have enough experience to have seen such before. I'm guessing that when the wheel was full lock right the force on the tire compressed the right fork leg enough for contact to happen.

You are right. This is what I initially thought because of the really poor brake application and the resulting sound from the tire. I figured that if I locked the front that badly I would have washed out the front and low sided. I guess not. The tires should have been warm enough as I had been riding for almost an hour. I need to get a lot better at brake control under
surprise situations. I need to work on the forks as well.

jerryh

Sticky caliper piston(s)? Wouldn't think you'd grab that much front brake. Check over that bike thoroughly

xeris

Well you wouldn't think so but I am really a novice rider. I read and study riding techniques and practice them. I try not ride too far above my skill set but in a surprise situation I'm still not there.
I don't think that the caliper is to blame. I have been practicing hard braking (straight line) from speed trying to develop feel for impending lock-up and the brakes feel like they are functioning normally. That's good advice and worth a check. I also am going to check the wheel/fork alignment.
I want to do some track days.

smokinjoe73

You were on the rear brake mid corner? I would stop that practice.

Is your bike stock? Is there anything else to rub against at full lock and bottomed out?

You can for sure lock the front and keep going. I have done it often. The trick is to form the habit of doing a grab and release of the front brake to let it regrab.

And moto gods? If its truth you seek, then I would be thanking the one true God.


I would check tire pressure. Hard tires slide much easier. The hardest trick in riding is NOT tensing up in these moments. Stay loose on the bike and avoid harsh inputs (including chopping the throttle). Counter intuitive but vital to stay upright.
Sounds like you coulda slid both ends. You should avoid that too.

xeris

Thanks for the input Joe.
The turn is gradual enough that at the speed I was going, 70+/- there is no need to brake. The only time I use a small amount rear brake is just before applying the front to help keep the rear from jacking up as much. It is a technique that is suggested in a book by Nick Ienatsch. He does state that the use of this method is controversial.
Since I have had time to think this out, and the feed back I've received, it seems unlikely in the panic situation I put my self in I would have even touched the rear brake at all. I think that I just jerked the front lever. That simple. Smooth I was not. I feel very fourtunate not have crashed, especially right in front of the local LEO.
I appreciate the input. It has helped sort this out in my head.

ChikinLady1011

regardless of the reasons why it happened, there is no way there is enough give inbetween the wheel and the fender to rub like that, especially on a worn tire. Check your front bearing, check spacers, check everything that bolts together in the front and make sure it's right. I checked mine after looking at that picture, and have more than 1/2" of space. Plus, forks compress above the fender and wouldn't change there space. Especially on the side like that, it looks like it might be a spacing issue which would make me start with anything related to that front axle. Please look over it thoroughly...I'm sure that was scary as hell.

jerryh

Bearings and spacers...great thought! Also hardware on upper and lower triple clamps

xeris

Thanks for the suggestions. I'm going to pull the front wheel off and have look at all the components. Though the forks compress above the fender, if enough side force is applied to the tire/wheel the perpendicular relationship between the axle and fork would change because the forks can work independently, one would extend and the other would compress causing the wheel to be on a slightly different plane than the forks. That is my thinking on the rub marks. If that was the cause that is a lot of stress, so yeah I'll look at everything.

That is funny. Ya got to know your limitations.

xeris

Just a follow up.
While I was riding over to my shop to pull the wheel off and inspect, I noticed that the alignment marks on the yoke and frame were out.
I don't have V blocks or a dial indicator so I had to eyeball the runout on the axle. Not very precise as spec is .20 mm. Nothing obvious there. No marks on the axle or spacers. Put the wheel on my balancer to check run out on the wheel (made a makeshift indicator) that showed to be near perfect. Without a dial indicator I have no value, but I would say that the whole assembly is still in spec. The rub marks on the tire were from the fender alone. It was about 3" along the outside edge.
Reset the the steering alignment and went for a ride. The feel in the bars seemed to be more neutral. This could just be placebo effect as the bike always feels faster and smoother after an oil change, detailing, new turn signals, etc.

smokinjoe73

Good old placebos. I need some of those.

Chalk it up to hamfistedness and apply the brakes smoother next time. Always be ready to release the lever. It can really save you.

RobertLever