Emergency braking will wreck your tyres instantly?
 

Hi all,

Little backstory: had to brake super hard cause a car turned into the cycle lane unexpectedly, skidded for a few meters. Luckily I didn't come off and came to a safe stop.

Anyway this is how my tyres looked after, only had them 2 months, is this normal? For the tyre to shred right down to the next layer or tyre.
Just thought they might have a bit more longevity to them that's all. But if this is normal then fair, otherwise a little sad I have to buy replacements
https://cimg1.ibsrv.net/gimg/bikefor...fe4207e014.jpg

It's probably normal for that tire; some other makes and models offer greater longevity. That said, skidding will take its toll on any tire.

That is not abnormal, many of the best gripping tires will also have a very soft tread.

Seems surprising to me, too. I would not expect to see that on a Continental 5000 (my daily driver) and certainly never on a Gatorskin. But those Vittoria Corsa were stock on my bike when I bought it and I changed out of them because of a LOT of flats. Very smooth ride, but roadside repair took the fun out of them. Maybe just "too nice." dunno.

Yes skidding can introduce patches but I'm a bit surprised that one hard skid and 2 months of normal wear took it down to the casing like that. I understand that tire is not known for longevity but still.

I don't know that particular tire, but the Corsas are in general, very close to race tires. (For any quality tire, the manufacturer has decisions to make re: rolling resistance, weight, grip, flat protection and durability. These are basically slices out of the same pie. Increase one and you have to subtract from another(s). For those tires, the emphasis is on the first three. Again, I do not know your tire, but on many of the Corsas, the grip is excellent. Good grip is achieved with a softer rubber compound. Combine that with low weight and you get a thin tread that rubs off fast if you skid on it, something that may never happen in the life of a tire used for racing.

A question and comment: The tire kept you from hitting the car, yes? If so, just maybe it paid for itself. And the comment - modern brakes have more power than either needed or wanted in panic stops. Locking up the rear wheel is counter-productive in terms of stopping distance, bike control and rear tire life. Modifying or changing one's rear brake to be less effective sounds backwards but actually makes for a better, safer bike. I set my city bikes up with the well known French stoppers in front and a decent, but less powerful rear of different make entirely. In the '80s, all good bike ran full length housing for the rear brake that added "sponge" and detracted from the rear brake's power. In the '70s. manufacturers routinely set the rear breake higher than the front to lessen its power. In the early days of dual pivots, Campagnolo provided the older sidepull design for the rear brake. But "bike think" aka marketing changes with time. Brake power now rules. But as you have seen, brake power isn't entirely a blessing. Yes, it offers good fingertip control from the brake hoods and saves hands from tiring on long, steep descents. But when adrenaline takes over ...

I love almost all the Corsas I've used. In large part for the excellent grip. (I had a pair of older summer Corsas that were scary on the slippery, oily first rain of August. But the rest have been good tires and the wet weather specialty tires a treat in the Portland winter.) Many here prefer the longer wearing in general Continentals but I'll stick to the tires that might just save me a crash or two, even at routine drain to my wallet. And yes, I can kill all those Corsas with one slide like you did.

You get maximum braking when you DON'T skid.
You get maximum braking on the front since most your weight is transferring in that direction.
Practice your panic stops so you can perform one without a skid.

Funny story, I was riding to my son's elementary school to pick him up. Only a mile away, riding my coaster brake cruiser. Going down the hill to the school, a car pulled out in front of me, and I locked up the back (only!) brake, skidded for about 25ft, then heard "POP"!! I took ALL the rubber off, went right down to the tube. I was surprised - these were 2.125" balloon tires, essentially brand new.

I remember as a kid we'd have contests to see who could make the longest skid. Never blew a tire! I guess weighing 4x as much as I did then explains the difference :).

So, yes, ONE skid can trash your tire.

Panic is panic, which means that not a lot of thought goes into the reaction. The key to successful panic braking is, as Bill says, to practice, practice, practice to the point that your brain is wired directly to your grip muscles. Even then it's always iffy so rely on your road savvy to avoid the need to panic brake. PS: Glad that your incident only resulted in a bit of tire damage.

Makes you wonder why some fixie riders rely on the skid-stop technique for braking.

Looking t the photo, I suspect that the one skid wasn't the only factor. There seems to me a wear zone much longer than the few inches a single skid causes. So, either you rode the life out of a thin soft tread tire (certainly possible) or you have a history of overuse of the rear brake.

Going forward, consider a tire with harder longer life tread compound (at the cost of some traction, especially wet traction), and or try to change how you use the brakes. As noted earlier the front brake provides the vast bulk of braking power, and you achieve the shortest stopping distance when 90% or more of braking is from the front.

BTW- where you live has a material impact on tire life and you do best when you consider it. Roads in the Southeast tend to be "coarser" than up north and therefore tires wear faster. Temps also matter, and tires that offer great traction in the Northeast will suffer extremely short life on the hot pavements of the Southwest. Years ago when I marketed tubulars, we had a particular tire that was popular because of it's excellent wet traction. Things were great until I started selling them in places like Colorado, where long descents on hot pavements shredded them.

Does anybody use lesser brake pads on the rear brake? That could be a really simple way to improve the panic stop scenario.

If the OP has skidded the tire before, that increases the chanced of it rolling to the area of the previous skid before locking up again, and accelerating the problem.

IME no, but historically bike and brake geometry was such that the rear brake offered less leverage to the rider, so some proportioning was designed in. I've no idea whether this was intentional or serendipitous. That said, tire protection is of the least concern, and in an adrenaline fueled panic stop, the natural braking process would have so much weight shifted off the rear wheel, that any skidding would cause minimal tire wear.

As I posted earlier, the tire wear seems to indicate an over reliance on rear braking, and if that's the case it's a question of the rider's learning to trust the front brake more. Sadly, so many newer riders still get "death" warnings about how front brakes will cause endos, and are therefore conditioned to develop bad braking skills.

Yep. This is the theory behind ABS in cars. I learned in freshman physics that the coefficient of static friction is always greater than that of kinetic friction.

It’s probably the tire, I really like those, but they are not durable. I’ve got Gatorskins on my coaster brake bike, and I skid them all the time, cause it’s fun, no noticeable wear yet.
Tim

https://cimg9.ibsrv.net/gimg/bikefor...3349cd702.jpeg

About 15 years ago, the local fix gear shop bought some VIttoria? winter tires. Tough and good stoppers. I bought a pair for my workhorse commuter fix gear. Next time back at the shop the owner told me he'd sent his remaining stock back. Reason? The fix gear crowd were returning them, saying they were getting injured trying to stop with them!

I love that. Using only a poor stopping rear wheel to stop, then avoiding the tires that maximize that poor stopping power because - they stop too well.

I sure hope the bike that your kid was on, when riding home, had two brakes... Andy

A few minutes reflection as to what I just wrote- My point was to hope you don't ride your kid home on your bike that has only a rear brake. And that you could/should teaching your kid how to use their front brake.

Very few of riders are taught how to ride their bikes. Sure, we learn how to balance and pedal early on (usually). But how to handle the bike beyond initial balance, how to use their brakes (note plural), how to position their body to better counter forces (or even absorb road shock), how to shift smoothly (and before the need becomes frantic) is rarely sought out.

The actual theoretical maximum deceleration occurs when the center of gravity is directly over the contact patch and the only force action on the contact patch is gravity. From a practical standpoint, however, this is not a good practice for a couple of reasons. First, you’ve turned the bike into a unicycle with a pivot in the middle. Second, and more importantly, the bike and rider are at the limit where going beyond that limit is going pivot the CG around the handlebars and the rider is going to fall to the ground.

From a practical standpoint, the best braking practice is to maintain two rolling wheels for best control. You may lose a little deceleration (but not much) but you remain in better control with both wheels on the ground. If the rear wheel lifts and the rear wheel begins to slide, get off the front brake to bring the rear wheel back in contact with the ground. Rolling deceleration is maintained and the rider doesn’t risk pitch over.

Additionally, you can almost double the deceleration by pushing back and dropping down. A rider seated in the “normal position” can achieve 0.5g of deceleration before the bike goes to the point of pitch over. Pushing the CG rearward and downward about 4” each increases the deceleration to a little less than 1g. An incline will decrease both of those number which is why mountain bike riders almost alway push off the back of the saddle when braking.

You don’t need a weaker brake on the rear, you just need to use your brakes more effectively.

Pushing your butt back off the seat allows you to lock your elbows and takes weak muscles out of the equation.
Just a few practice "panic stops" will make future "panic stops" much less panicky.

Some tyres seem to be more susceptible to that kind of damage than others. I used to ride Conti 4 Season tyres as they are excellent all-rounders. However, after wrecking two, one practically new, with emergency stops I decided to try out Michelin Pro 4 Endurance. These have very similar characteristics to the Conti's but, so far, I've not had the same issue with them.

The theory behind ABS is vehicle control, not maximum braking. ABS allows one to maintain steering control, but it increases stopping distance. Maximum braking/minimum stopping distance is achieved via threshold braking (the point just before lock-up)...ABS takes the vehicle to the point of threshold braking, then releases the brakes momentarily, then reapplies, then releases, etc.

That has nothing to do with maximum deceleration. You can lock your elbows without pushing back on the saddle and that will not increase deceleration. Moving the center of gravity will. It’s a fluke of our high center of gravity mode of travel. Tandems, for example, can’t be pitched over because the center of gravity is further back, making lifting the rear wheel high enough to go over the handlebars impossible.

The latter part of that statement may have been true in the early days of ABS, but modern ABS systems can and will stop in shorter distances than humans.

No, but I use Campagnolo differential brakes (dual pivot front, side pull rear). The main benefit is the slightly greater clearance in the rear, but I don't mind that the rear, which I mainly use to scrub speed on hills, has a bit less power. I also ride with my front brake on my right hand and rear on my nondominant left (but don't feel like rehashing the pros/cons of that choice).

I'm glad you posted that video, because I was going to as well. Not in correction to anything posted here about bicycle brakes, but just as an interesting journey into the physics of tire slip and how a very slightly slipping tire develops MORE braking than one that has zero slip. Of course, this condition can almost never truly exist on a bicycle because we don't have near as fine a control over brake modulation that we'd need...and the notion that keeping the tires from sliding on the pavement for best braking is absolutely true for us. But modern ABS on vehicles is nonetheless very interesting to study.