Roundabout Lowside. Cold & Wet Road Caused It?

[akima]

Link to original page on YouTube.

The rider commented:

Basically what happens when you lean over too much on a cold wet day. Luckily I am okay and will hopefully be back on the road before too long.

I thought I'd post the video here, as his stated cause of the crash (cold, wet and too much lean angle) didn't seem satisfactory to me. I like to understand what causes crashes so I can avoid making the same mistake.

His speed was 29mph entering the roundabout. He brought his speed up to 33mph while leaning over. After his tyres lost grip you can glimpse his dash displaying 36mph. I didn't get the sense he gave it much throttle, so presumably the jump from 33 to 36 was just the wheels spinning up faster after they broke free of the surface.

He had 1 finger on the front brake lever. Did he grab it? I noticed his back light flash on just before he turned steeply in. How hard did he brake? Did this upset the suspension? Did he get throttle jolt (I can get this quite badly on my bike) when he switched from decelerating to accelerating?

I'm guessing he was holding the bars too tightly which didn't allow the bars to turn by themselves to account for his lean angle and any imperfections in the road surface; this overloaded the available grip of the front tyre causing the front wheel to tuck.

Anyone got any better ideas or observations?

[DannoXYZ]

Yes, too much throttle and power for the wet road. Just because the display went from 33mph to 36mph, doesn't mean that little power was applied. He could've been at 100% throttle and there was only enough traction to allow a 33 -> 36mph acceleration. That 36mph may just have been the limit. Doesn't matter if he was at 25% or 50% or 100% throttle, anything over the traction limit was too much.

To help with these situations, keep the bike as upright as possible. Lean the body inwards while keeping the bike upright. Then when too much power is applied, it would just spin the back tyre. However, the bike will be stable and will go in a straight line with the back tyre spinning. In this case, it doesn't matter how much or how little traction there is, the back tyre can be spinning at 36mph or 100mph, it will still be much more stable than when leaned over.

[Wanderer]

It's hard to admit when we just make a mistake.

Instead we blame it on tires, cold, wet, traffic, other riders or anything else that will make us forget that we are the cause of our suffering.

[Chocula]

The cause of the crash was the riders lack of judgement.

There are some nit-picky contributing factors such as:

1. Riding to fast for conditions
2. Lean angle was excessive for conditions
3. Transition did not appear smooth
4. Multiple steering corrections while leaned
5. Bad line leading to steering correction near traction limit
6. Crossed up body position
7. Wet road
8. Possible cold tires

He probably went through that intersections riding that way many times under better conditions without any problems. Take away one or 2 of the above issues (speed being the most relevant) and he likely would have been fine.

It was not the road conditions that caused the crash, rather the lack of judgement and not making adjustments to compensate for the existing conditions.

[csmith12]

imho... there is no mystery here

You have to watch it at least 2 times to figger it out. We have been told time and time and time and time and time again that turning + throttle will put you on your tail. I am sure the surface conditions didn't help, but it is not an excuse for the rider.

Watch it AND hear it... you will know. Poor chap, but he was geared to the T...

[adouglas]

"It almost sounds too simple, but it's true: What you do is what happens; what you don't do, doesn't happen.

"Motorcycles don't do anything by themselves. They don't win races or lose them; they don't make mistakess or do anything right. Everything that happens during a ride depend solely on the rider." -- Keith Code, A Twist of the Wrist Vol. 1

[akima]

Originally Posted by csmith12

imho... there is no mystery here

You have to watch it at least 2 times to figger it out. We have been told time and time and time and time and time again that turning + throttle will put you on your tail. I am sure the surface conditions didn't help, but it is not an excuse for the rider.

Watch it AND hear it... you will know. Poor chap, but he was geared to the T...

So you think the primary factor was him giving the bike too much throttle?

What about the factors that Chocula mentioned? Do you think giving it too much throttle played a much bigger role than those factors?

Personally, I didn't see that his speed was excessive. I don't think I would have taken that roundabout any slower than he did.

[csmith12]

If.... he was an experience rider

I don't think he was going to fast.
He did have a line that wasn't ideal, but was workable
He did make steering corrections (throttle + steering)
Can't say if his tires were cold or not???
Wet/damp pavement I am sure was a factor
At the speeds in the video, being crossed up doesn't help but isn't the cause either... perhaps a contributing factor
Too much lean angle? Dunno for sure, vid is unclear but doesn't lead to that conclusion

Adding lean + throttle = skidmarks....

Are there reasons why he had to add lean? sure! The video starts out with him shaking his head that something isn't right. I don't know for sure what that is. imho, these are self fulfilling prophecies. Learning to catch them early enough is what is hard. :\

[greg737]

Those roundabouts in Britain, Scotland and Ireland can be soooooooo sketchy. Often the type of pavement in the roundabout is different from the roads leading into and out of it, they seem to be surfaced with a type of blacktop that's meant to last a long time and just like tires that are meant to last there's not as much traction Did you see how large the aggregate was in the pavement​of the roundabout? I've had some scary experiences with roundabouts.

[akima]

Originally Posted by greg737

Did you see how large the aggregate was in the pavement​of the roundabout?

What do you mean by "the aggregate"? I haven't heard that word used in that context before.

[Panda]

Originally Posted by csmith12

..and time and time and time and time again that turning + throttle will put you on your tail.

This is what I see too. Throttle + increasing lean angle and it puts him on his ass.

[adouglas]

Originally Posted by akima

What do you mean by "the aggregate"? I haven't heard that word used in that context before.

Size of the rocks in the road surface.

[DannoXYZ]

Originally Posted by csmith12

Adding lean + throttle = skidmarks....

Not on wet pavement Even on dry, you have to have quite a slide to leave skidmarks, either the tyre's going sideways a lot or it's spinning a lot. Takes less than that for a low-side.

[DannoXYZ]

I think the line chosen made it worse. He veers to the left when entering the roundabout, than sharply turns right. If he had hugged the right side more, he wouldn't have needed to steer so suddenly and caused large weight-shift and lean.

[greg737]

Originally Posted by akima

What do you mean by "the aggregate"? I haven't heard that word used in that context before.

In British English, the word 'asphalt' is used to refer to a mixture of mineral aggregate and asphalt/bitumen (also called tarmac in common parlance)

You can use a wide variety of mineral types as aggregate for making an asphalt (tarmac) mixture.

A while back the governments of some islands in the pacific decided to use crushed-up coral as the aggregate. You can still find some of these roads today, like in the quieter parts of Guam. As these coral-aggregate roads weathered and wore under usage (traffic) the exposed bits of coral became polished (like little pieces of jewelry) and you wouldn't believe how slick these roads are, especially when it rains.

On Andersen AFB at the north end of Guam there are old, worn coral-aggregate roads that are hard to walk or run on when they're wet.

[DannoXYZ]

Heck, at end of Market here in S.F., there's some tile sidewalks around Embarcadero buildings that's treacherous even when dry! When it rains, I walk in street to avoid falling!!!

[akima]

Originally Posted by greg737

In British English, the word 'asphalt' is used to refer to a mixture of mineral aggregate and asphalt/bitumen (also called tarmac in common parlance)

You can use a wide variety of mineral types as aggregate for making an asphalt (tarmac) mixture.

A while back the governments of some islands in the pacific decided to use crushed-up coral as the aggregate. You can still find some of these roads today, like in the quieter parts of Guam. As these coral-aggregate roads weathered and wore under usage (traffic) the exposed bits of coral became polished (like little pieces of jewelry) and you wouldn't believe how slick these roads are, especially when it rains.

On Andersen AFB at the north end of Guam there are old, worn coral-aggregate roads that are hard to walk or run on when they're wet.

Woah. I had no idea this was a thing. Is it possible to visually discern coral-tarmac from non-coral-tarmac?

[greg737]

Originally Posted by akima

Woah. I had no idea this was a thing. Is it possible to visually discern coral-tarmac from non-coral-tarmac?

Yes, wherever the coral aggregate is exposed it is white(-ish). If you get down really close to it, feeling the surface of an individual piece with a fingernail you find that it is smooth as glass.

On Andersen AFB (circa 1990's was my timeframe) slip-n-fall injuries on these old roads were so common that a warning about the situation was included in the mass "incoming brief" given at the base auditorium to personnel temporarily stationed.