XxHaimBondxX

I had to brake hard this morning to avoid a dog. I noticed the rear tire slid, causing the bike to turn sideways and me roll over it. These are rim brakes, wheels are true. Rear tire doesn't have as much thread as the front, but still has plenty. Dry, clean pavement. Not sure what other info required to assess this. I feel like if bike stopped straight, I wouldn't have fallen over, since I wasn't moving very fast.

maddog34

i doubt the bike had anything to do with which way you skidded...

check wheel alignment in relation to the frame
check wheel "dish"
check fork alignment to the rest of the bike.
check your lean when you panic and turn at the same time to avoid a dog, possum, or any other thing that induces a panic stop.

Iride01 

If you lock the rear wheel up and the front wheel is braking but still rotating, then your bike frame is going to rotate around the steerer tube in one direction or the other.

When a wheel is locked up, there is less braking force between the tire and pavement than a wheel that is just being braked hard but not locked up or skidding.

Andrew R Stewart 

You unknowingly made the rear wheel both lock up and to skid off to one side. Were you also applying the front brake? Were you able to shift your butt rearwards? Had you explored your bike's ability to stop quickly before this time?

One of the techniques we teach in our Safe Riding classes is the emergency stop. This requires strong but sensible use of the front brake and shifting one's butt rearwards to keep the rear wheel planted. Helping the riders get over their fear of the front brake is a big part of this. Andy

XxHaimBondxX

Don't remember my butt position, but due lack of training, I doubt I reacted properly with it. I did pull on both brakes at the same time fearlessly. Last time sliding situation occurred was in the fall, so I attributed it to dead leaves and debris on the ground.

Should I adjust my rear brake to require more effort to pull?

Iride01 

I'd just get use to modulating the force you put on your brake levers. As well as moving your weight back on the saddle as another mentioned.

It took me a while to learn how not to lock up the rear wheel every time I did a panic stop when I went from rim brakes to disc brakes. Sometimes I felt like my frame was 90° to my direction of travel. And other times when I didn't keep my front wheel pointed in the actual direction of travel, I wound up bouncing down the MUP on my side. Luckily, I too just had to get up and brush myself off.

Only if the brake lever felt like an on/off switch where there was no in-between, would I try to adjust the brakes to have less force.

FBinNY 

Nothing in the bike itself would gave caused this.

When you hard braked, the bike's weight distribution changed, with the load on the rear wheel dropping to near zero. That lowered the rear traction allowing the wheel to slide sideways. Since the front was restrained by the brake, the bike wanted to swing around it.

If this were a car, you would have done a spin, but since you're on two wheels that didn't happen. Instead, the bike swinging changed the ine of forces, so you had nothing to stop your body from continuing forward and crashing to earth.

For future reference, once you feel the rear slipping, ease up on the front to recover the slide, or worst case do a slide fall.

maddog34

"Tread" had nothing to do with the skidding.. When a tire contacts pavement, the rubber creates "friction" as it conforms to the rock surface.. Tread only figures in when water, ice, or dirt is presented to the tire surface. Excessively open "tread" creates less friction with a paved surface, and less TRACTION. Look at a Drag racing "slick"... no Tread.. Indy car or Nascar tire? No Tread... When do you see tread on a race tire? During wet or loose surface conditions. The Best Pavement Traction is provided by a soft rubber compound and a sandpaper-like Surface to contact. A soft compound will speed up the conforming process... soft tires also wear out quickly... The rubber compounds used are a Compromise between Max Traction and Reduced Wear.

SIPING is used on Ice/snow tires to Present a million little Cutting Edges to the surface.... the increased PRESSURE created by each edge kinda MELTS it's way into the ice ! Rally Snow tires are purposely Narrow to INCREASE CONTACT PRESSURE... on perfect snow conditions, they actually provide MORE traction than a Gravel Rally tire on loose gravel !... WAY hooked up!

Large Grooves in tire surfaces Pump Water toward the edge of the tire, away from the central area... the Central grooving hits first, the deep grooves then moves the water outward... this is why the "arrows" on a tread surface always face to the front when looking at the top of the tire...

"Knobby" tires increase pressure and allow room for softer material to Move away inthe hope that firmer material is found beneaththe soft surface... and, in extreme conditions, the knobs will act like little baby shovels and you are then propelled forward by the same principle that lifts a rocket into space.. "Action/Reaction.. the weight of the flung off mud becomes your propulsion.... with a bit of good ol' friction too, if your tire was lucky in digging down to the good stuff.

Traction 101, Module 1

XxHaimBondxX

I feel like if I did that, I'd be getting a notice from lady's attorney right about now, since I stopped merely inches from the dog.

Sy Reene

What side of your bike do you mount your mini pump?

XxHaimBondxX

I have a frame bag with tools, pump and spare tube. I believe it's somewhat equally distributed.

XxHaimBondxX

I was thinking of variables, so there's one less to consider. Come to think of it, I hold steering wheel with my left hand, therefore, it makes sense my left hand will pull automatically, since it's the easiest motion.

Bill Kapaun

Then you'll know who had the unrestrained dog and to sue for any injuries to you or your bike.

maddog34

i always skidded my Stingray rear tire to the right.. i'm left legged. which leg do you choose to kick with, mostly?

and then, there's the panic steering variable...you probably went for the easiest possible route to avoid the pooch.

as to the lawyer thing... if the dog was off-leash.. sue for a new tire, repairs, and any medical expenses.. Just kidding... spit happens. and be happy it wasn't a German Shep named Rommel. (paper route, 1967, Lake Grove Oregon, along Upper Boone's Ferry Road, about 5:30 in the morning... every day of the week...) Ajax Ammonia in a squirt gun taught him to not attack me....After three applications, he'd just stay in the yard and bark a lot.... i'd used the bike's chainring as a weapon before the ammonia training sessions began... they hurt.

FBinNY 

The ability to avoid collision by braking is limited. It's often better to stay off the brakes and try to steer out of trouble. It's best to stay alert and ride within control, and/or stay aware of escape paths for when surprises happen.

I know that some people like to walk dogs on long leads, so there's always the possibility of a dog suddenly running out with the lead blocking your options. OTOH the lady and dog didn't jump from a helicopter, so you should have been aware of the potential and ready to steer or stop and avoid the crash safely.

You are the captain of your ship and need to avoid the shoals. This will come more easily with experience.


.

79pmooney

XxHaimBondxX, go out to a parking lot or empty stretch of road and practice braking with the rear brake. First, rear brake only; braking hard enough to skid. Learn where the skid point is. Then start using some front brake. Get to know how much less rear brake pressure it take to skid. Then more front brake. Then a full hard stop with the front brake. Here you will see that just touching the rear brake will start a skid.

This is by far the best way to learn how much rear brake you can use. And note - stopping in a straight line on level ground is good conditions for the rear brake. If you are turning, things go bad much sooner. Downhill also reduces the amount of rear brake you can use.

grumpus

Forget about the back brake in an emergency stop, going straight in the dry on a good surface - using only the front brake will stop you just as quick with minimal risk of skidding the back end. When you brake with only the front brake your mass tries to rotate around the tyre contact patch, so you'll want to duck down, brace your arms and hang back off the saddle; doing this stops you going over the handlebar and puts all your weight on the front tyre improving its grip. In an emergency the rear brake should only be used with care in slippery conditions when it would be more hazardous to use the front brake hard, and sharing the load between both brakes reduces the risk of a front wheel skid.

mpetry912 

the more I read this thread it almost has to be a wheel not centered in the frame or a frame alignment problem.

/markp

FBinNY 

Then your need more work in reading comprehension. A solid plurality, if not most posts discuss failure to maintain control when braking.

Even the direction of the skid is not a mechanical issue. Just as with a car, the direction of rear rear wheel slide is determined by steering input.

As you approached the dog, you automatically (and unconsciously) started thinking about both steering and braking. If you saw an escape path to the left, you would have started that way even as you applied the brakes.

Left steering with brakes applied means rear wheel skids to the right. Had you considered steering to the right, you would have skidded to the left.

All of this happens unconsciously, but with experience, you develop preset reactions and greater mastery over situations like this.

It's like when you learned to walk. As a toddler, it was simple, trip then fall. Each fall helps condition your brain and you stumble and recover instead a d of falling. In a short while, you become good at maintaining balance and actually falling becomes the exception.

Chuck M 

The second reply in this thread pretty much explained what happened. It is like what happens in a car when the emergency brake is pulled locking up the rear tires.

In the OP's case, this skid was likely due to the dog not being controlled, the rider not anticipating that the animal could be unpredictable and poor braking technique.

LarrySellerz

The only “mechanical” solution here is to make your front brake stronger, but chances are you just didn’t grab the front brake enough. Bike going to the side when skidding the back tire is normal.

id go with making the front brake stronger before making the rear brake weaker, and if it looks like the front brake is plenty strong then there isn’t a mechanical fix for your problem.

darn dogs.