Stupid Pratfall

[SFSV650]

So I managed to toss the bike down the road while riding in a straight line on my way to work yesterday. I already feel pretty stupid, so I figured I might as well share. Handy diagram attached.

TL;DR : Enthusiasm exceeded traction.

I was headed downhill on a 3-lane, one way street when a car ahead started to make a right turn (on red) into my lane. Any rider paying attention had plenty of room to avoid him so let me start by saying I don't blame him at all. I decided that going around was a better plan than braking, so I opted for a nice wide arc to pass through the center lane and back around into my lane ahead of the car. Nothing as dramatic as what I've practiced with Z2 etc; I was going for a wide berth. I pushed left, switched lanes, all good.

As I pushed right on the bars to head back into my lane, I had a momentary feeling of a loss of control and quite suddenly I was on my back wondering where my bike went. The bike slid about 250' on it's right side and ended up in the left most lane. I slid about 100', almost entirely on my back.

I've pulled much more dramatic maneuvers at higher speeds without anything going wrong, so I was rather surprised. I was riding in an evasive commuter style, but I didn't feel like I was pushing the envelope.

Possible Contributing Factors

Cold Tires:
I was only about ten minutes from home, and I don't love these BT-023's. They've been a bit squirelly in turns and seem very harsh over bumps, but I've ignored that until yesterday. They still have 50%+ tread and 32/35 PSI.

Mystery Fluid:
There's a ~60' x 2' swathe of very slightly darker roadway around where I lost control. Heavy traffic prevented me from getting a good look at it, but it could easily be coolant or gasoline.

Uneven Concrete:
The road surface is slightly rippled and cracked just past the inflection point of the slope. I've seen much worse.

Speed / Throttle:
I was doing 30mph in 3rd gear and was rolling on some throttle as I went to go around. Probably more than I needed to. I wouldn't think it was enough to break traction, but maybe it was.

What I Think Happened
I got the front wheel very slightly off the ground for a brief moment (because of throttle input, the slope, and/or the rippled concrete) and then put it down ever so slightly cocked on to one of the ripples or on to the mystery liquid. Once it touched down the bike chucked me off to the right and went on it's merry way, more or less in the direction we had been going before the attempted steering input.

Room For Improvement

• Wait until I'm past the inflection point of any hill to get a better look at what I'll be working with (though the darker asphalt may have been hard to see even at 20mph)
• Switching back to PR3's. It probably wasn't the tires, but the bike felt less twitchy overall when I was running them before.
• Go slower (always). 30mph seemed safe and prudent, and gave me room to maneuver relative to the traffic behind me, but maybe it wasn't.
• Brake before making an evasive maneuver, so long as I don't end up surrendering my escape window to the traffic behind me.
• Do not attempt a two-step maneuver if there is a likely / possible change in conditions between step one and step two?
  
• :dunno
• Profit

 

[latindane]

Sounds like you were on a piece of road with reduced traction. Did you rely solely on countersteering to turn the bike? Your body position and inputs (besides countersteering) become rather important when things gets slippery. The better those are, the slighted the countersteering input needed, making it less likely to suddenly lose traction. :2cents

 

[Gary856]

Nice diagram - very clear.

Crash analysis rule # 1 - it's never the tire's fault (unless they blew up right before the crash), so eliminate that from the factors.

It seems you overloaded the front somehow with that maneuver. Did you transition from downhill to flat ground as you crossed the intersection so the front was heavily loaded/compressed, or was it downhill-flat intersection-downhill again so the front was momentarily unloaded as you went from the flat intersection to downhill again? How smoothly did you execute the left-right swing?

 

[SFSV650]

Nice diagram - very clear.

Thanks.

Crash analysis rule # 1 - it's never the tire's fault (unless they blew up right before the crash), so eliminate that from the factors.

Ok, will do.

It seems you overloaded the front somehow with that maneuver. Did you transition from downhill to flat ground as you crossed the intersection so the front was heavily loaded/compressed, or was it downhill-flat intersection-downhill again so the front was momentarily unloaded as you went from the flat intersection to downhill again? How smoothly did you execute the left-right swing?

The latter.

The intersection is not extremely steep. I rode through it again today, in the center lane, in a straight line. I noticed a very slight ripple as I went over the spot at which I lost control, but probably only because I was watching for it.

I believe the turn was executed quite smoothly; I was anticipating a very slight lean, maybe 5 to 10 degrees. Instead, very little input on the bars resulted in a huge amount of lean.

 

[i_am_the_koi]

Interesting to hear you say that about the BT-023's. I just put them on my bike after loving the previous ones I had on my last bike, but haven't ridden enough to be able to comment on feel yet.

 

[SFSV650]

They're not bad tires by any stretch of the imagination, and they've got great tread and shape left after 6,000 miles (without much squaring off by being upright most of the time) but I've had the unnerving impression that they're hopping/skipping laterally ever so slightly in turns in the twisties, they pull and push back through the bars in tight urban turns, and they have a tendency to pull to one side or the other when cold or when braking, especially on raggedy pavement. :dunno

I don't think they're responsible for the incident above, but it is off putting.

 

[RickM]

They're not bad tires by any stretch of the imagination, and they've got great tread and shape left after 6,000 miles (without much squaring off by being upright most of the time) but I've had the unnerving impression that they're hopping/skipping laterally ever so slightly in turns in the twisties, they pull and push back through the bars in tight urban turns, and they have a tendency to pull to one side or the other when cold or when braking, especially on raggedy pavement. :dunno

I don't think they're responsible for the incident above, but it is off putting.

That's really completely opposite of what I felt with bt-023. On my bike they were very neutral. I think in your case it's likely suspension or alignment is the culprit; Especially the pulling to one side.

 

[tzrider]

OP, are you able to say which tire slid first? Alternatively, which direction was your head pointed relative to your slide when you hit the ground?

 

[Enchanter]

That's really completely opposite of what I felt with bt-023. On my bike they were very neutral. I think in your case it's likely suspension or alignment is the culprit; Especially the pulling to one side.

If suspension or alignment were the primary factor, why didn't he crash the previous day or week?

 

[RickM]

If suspension or alignment were the primary factor, why didn't he crash the previous day or week?

Sorry for the thread tangent. I was responding to his comments about the tires. I don't think suspension or alignment caused OP to crash. OP doesn't think the tires were the reason either.

 

[Enchanter]

Sorry for the thread tangent. I was responding to his comments about the tires. I don't think suspension or alignment caused OP to crash. OP doesn't think the tires were the reason either.

I don't think it's the tires either.

 

[afm199]

Sounds like you were on a piece of road with reduced traction. Did you rely solely on countersteering to turn the bike? Your body position and inputs (besides countersteering) become rather important when things gets slippery. The better those are, the slighted the countersteering input needed, making it less likely to suddenly lose traction. :2cents

this countersteering alone will put you on your ass sooner or later.

 

[SFSV650]

OP, are you able to say which tire slid first? Alternatively, which direction was your head pointed relative to your slide when you hit the ground?

I'd have to assume it was the front, though I have no way of knowing.

I looked a little to the left as I went to execute the swerve, then looked back around to the right ahead of the car as I went to correct course. I was wondering why I was looking at the line of parked cars (being further to the right than I wanted to be looking) but the bike had already tipped way over at that point.

When I hit the ground I was looking left at the right side of the tank, then up, then over my left shoulder watching my bike. :facepalm

 

[Underdog]

Could you have tried to use your front brakes while swerving?

 

[Enchanter]

Could you have tried to use your front brakes while swerving?

Swerving requires a very large amount of traction and leaves very little left over for braking. Generally you should not brake and swerve at the same time. Brake then swerve, or swerve then brake.

 

[SFSV650]

Could you have tried to use your front brakes while swerving?

No, if anything that would make things worse.

I had a large space to escape into, I didn't want to find out if I could stop before the turning car (I probably could have, but then again I might not, especially if he decided to stop mid-turn), and I didn't want the wall of traffic behind to catch up. I was committed to going around; a maneuver which has saved me many times before.

Also, 'swerve' is too violent a term for what I was doing. I was aiming to trace a wide arc, not flick the bike I was weaving a line through cones.

 

[Underdog]

Swerving requires a very large amount of traction and leaves very little left over for braking. Generally you should not brake and swerve at the same time. Brake then swerve, or swerve then brake.

I realize that.
My feeling is that while the OP has been focused entirely on that black patch of the road, his front brakes were applied WHILE changing trajectory.

 

[Enchanter]

I realize that.
My feeling is that while the OP has been focused entirely on that black patch of the road, his front brakes were applied WHILE changing trajectory.

Ah, you're asking if he did that rather than if it is possible to do. Makes sense now.

 

[SFSV650]

I realize that.
My feeling is that while the OP has been focused entirely on that black patch of the road, his front brakes were applied WHILE changing trajectory.

Oh, gotcha.
No brakes, front nor rear.

 

[kongjie]

I realize this isn't on topic as crash analysis, more related to collision avoidance. Sometimes--depending on the location of nearby businesses, etc.--these right-turning cars are desperate to immediately move over to the leftmost lane in order to make a left/u-turn at the next light.

That kind of car behavior makes swerving around the entering car more risky than braking, at times.