Triode

I've wondered about this since I saw on TdF a rider - riding by himself - no one nearby, going thru a curve on a downhill section and he went down, after which the commentator said he "lost traction" on both wheels.

That happened this years TdF, following the incident the rider told the cameras " get the **** out of here" and they did. But the event was replayed several times.

Does this occur because the rider is coasting and not pedaling, hence no torque pulling him forward?

I saw a similar reference in another thread to "losing traction" on a descent and wondered just what is going on here.

BentLink

Lateral force was greater than road friction. It ain't traction for going forward, but for cornering, like when a car "drifts" or "gets sideways". This happened to me on a downhill when I hit fine gravel...not fun!

jmX

They lost traction. I'm not sure it can be explained any simpler than that. Is this even a real question?

Triode

Uhh, yeah. From a former motorcycle rider who has never had a motorcycle simply "lose traction" in a curve, where there is no debris, sand or gravel.

I have "lost traction" on a motorcycle on the asphalt only when there was sand, gravel or similar.

so, yeah, it's a "real" question.

merlinextraligh

The rider in question was Jens Voigt. The problem was that the road was quivering in fear underneath him causing the loss of traction.

Triode

That explains it pretty well.

So, do I understand that this can happen even if there is no grit, sand, gravel?

Maybe this is due to light weight of bike and rider, skinny tires - cornering at speed, not enough adhesion to the road

eippo1

Same thing with a motorcycle when you carry too much speed and attempt to change your direction. If your original force is more than the force that you're able to apply though the friction of your tires, then you keep going in the direction of the original force.
This can be exacerbated with braking kinda like in a cat 5 crit where the inside rider takes the turn with too much speed, hits the brakes at the apex and goes down across the turn taking the entire field with him (or her).

Triode

At times, on a motorcycle if you misjudge a turn - you can save it by dialing on full throttle - where the torque you are applying becomes the force that will overwhelm other forces - provided you don't pour on so much that the tire slips (loses traction)

I now remember that at the time I saw Jens Voigt go down, wondering if he had been pedaling hard if the torque applied would have helped him keep from going down.

I guess I'm just not used to thinking in terms of such skinny tires and such light weights as are involved with bicycles.

merlinextraligh

^you just can't produce enough torque on a bike, compared to a motorcycle, to "pull" yourself out of a problem.

byte_speed

Gravel certainly makes things worse, but if you try to corner too fast (motorcycle or bicycle), the sideways force on the wheel(s) exceeds their ability to stick to the road and they slide. If you are skillful enough and quick enough and lucky enough, you may not crash.

Ever see a motorcycle race? those guys are crazy good and they still crash, lots.

2manybikes

There are a lot of other people beside me in this world that can do a controlled slide on pavement on a motorcycle. There are a lot of people better at it than I am.
Road bicycles are not built to slide, but it can be done on pavement. Just go too fast for the corner.

Commodus

This is actually not true for motorbikes. Lots of people think it is though.

If you can accelerate out of a problem, you also could have simply saved yourself through steering alone. At no time does increasing your speed improve your handling.

Homebrew01

It's not specific to bikes. Cars, motorcycles, sneakers, hoofs ........... anything can lose traction if the lateral force exceeds the grip.

Mike F

duckracer

On the motorcycles, if you add throttle in a front end slide the rear will squat slightly which causes the front forks to extend taking some weight off the front tire. This is what allows it to maintain/regain traction. motorcycles have a very small contact patch and it can only handle so much load before the forces overcome the friction of the road surface and the tire contact patch. I have tucked the front while trail braking more than once and I have also saved a front slide by pushing my knee harder into the track to take weight off the front. That being said I have lost the rear twice by adding too much throttle trying to save a slide. Our road bikes with 700c tires have a contact patch about the size of a dime, it is amazing how much grip they have!

Triode

I think this is probably the biggest part. When I think about it that way, kinda stunning that they grip as well as they do.

RacerOne

It's equally amazing how fast it goes away when it does. Perfectly dry, smooth pavement in a Cat 5 (of course) race, one second I'm railing a turn, then smack my helmet on the ground. There was no transition or indication, just up, then down.

LesterOfPuppets

Try this turn @ 40 mph on your MC.



The bike race photog motorcycles typically lose a bit to good descenders in the turns, because they're not trying to win a race. They have to gun it in the straights to catch up.

DXchulo

https://www.youtube.com/watch?v=OWlcr4NJod4

(https://bicycling.com/blogs/hardlyser...jens-gets-mad/)

For the second one it looked like he either hit a slick spot in the road or he was braking too hard. You'll hear a lot of stories about the roads "melting" in the heat at the TDF.

LesterOfPuppets

If you'd rather watch videos of motorcycles just losing traction in turns you could just watch Faster. Fast forward this trailer to 1:55 to see a sequence with lots of loss of traction action.


Man, I think I'll watch this again tonight, it's been a while and it's an awesome movie!

JMR

Not to rain on your parade, but I would bet I would easily go around a corner at double the advisory speed on my m/c. In fact if I am riding on roads that I don't know very well, I use double the advisory speed as a good guide to what I can SAFELY go through the corner at.

To the OP, if you have never lost traction on a m/c without the aid of gravel/oil/water then you have not been riding hard enough! It does happen, but you have to be pushing pretty hard. It is much easier to reach this limit on a road bike (bicycle) due to the much smaller contact patch as a previous poster said.

JMR

LesterOfPuppets

Wow, that's pretty good, especially if you stay in lane before and after and are on the inside lane. I originally had 50 but tamed it down a bit. I've had my car around a 10mph hairpin at 40mph - inside lane and I stayed inside the lane prior and afterwards. 4 wheel drift! Fun as hell!

fogrider

yeah, the first one he completely missed the line. the second crash, as he said, he was trying to take it easy and braked too hard on the front wheel on a rough road and he leaned the bike too far. the roads there are just too narrow.

Runner 1

I wonder how light someone has to be before this becomes a problem.

On my beater 40 lbs mountain bike, I have no problem making ridiculously sharp turns where I nearly graze the ground. On my CAAD 10, however, I become slightly hesitant about leaning so far as I get the sensation that the bike is going to slip (it may not -- I just kind of wonder about it). I weigh 135 lbs. Do I need to worry, provided the ground is clean asphalt? (I'm looking for answers from experience, not conjecture).

Juan Foote

As a person who now walks around minus a left foot....

Please take that manner of motorcycle riding to the track or closed course. Skill has nothing to do with real world conditions and situations that you have no control over. Ride in an environment designed for it, with the proper gear, and with medical staff on hand to deal with situations that can and do occur. Public roads are no place to ride at the limits of you and your equipment. There are just too many freak unexpected occurances that can happen and end up hurting or killing someone, only yourself if you are very lucky.
Running around like a race driver on a motorcycle is just as bad for the image as riding down the wrong side of the road or sidewalk is for cycling. I don't mean to preach, just trust me I am living with the permanent result of my bad discretion. Be safe.