Know Your Average Stopping Distance?

[indianajo]

I have 26" discs, they're called rims. Of course high power bikes benefit from disc brakes, but there's no doubt in my experience that properly setup rim brakes are better than budget hydraulics. I'll stand my Tektro rim brakes with KoolStop eBike pads up against any disc or hydraulic on any $1500-$2000 wonder bike.

Rim brakes don't work in the rain after running through a puddle. My experience is that disk brakes do. Of course road tires present a limit to traction in the rain. I haven't skidded the knobby Kendas yet, been using them >11 years. There are 116 rain days/year in this climate.

 

[tomjasz]

Rim brakes don't work in the rain after running through a puddle. My experience is that disk brakes do. Of course road tires present a limit to traction in the rain. I haven't skidded the knobby Kendas yet, been using them >11 years. There are 116 rain days/year in this climate.

I find that some KoolStop pads do a decent job when wet. The caveat is rim wear. But I gave up all my 28-35MPH motors. I've actually gone backwards in terms of power and find 36V motors provide all I need and these days rarely ride over 15MPH. Time for me to slow down and smell the roses. My last 48V 1000W hub drive is being donated to a local fellow living on a shoestring. My MAC are capable of much more but 36V 20A is more than I need.

 

[Slow Rider]

There's a lot of skill involved in making panic stops and I'm willing to bet that a large majority of riders (me included) never practice them at high speed.

Here's another calculator. The only real takeaway from any braking calculator is that they follow the same general rule, increasing your speed by 50% increases your stopping distance 100%.

Science of Cycling: Steering + Activity | Exploratorium

www.exploratorium.edu

For example, here are some distances that the calculator generated.

15mph = 9 feet
20 mph = 15 feet
28mph = 30 feet
35mph = 47 feet

 

[Slow Rider]

Right, but the topic of this thread was whether or not ebikes are lacking safety due to inadequate brakes which I disagree.

You are correct that one of the topics being discussed is safety, but the title is "Knowing your Average Stopping Distance" and there are at least 10 posts talking about speed, stopping distance, and how long it takes to stop, so my post was on topic. In fact, you made the first comment, including "If you want to know the physics", which my post supported. So either both of our posts were on topic, or both were not.

 

[tomjasz]

All blather until you actually practice panic stops. Lots of ebikes are fitted with inadequate brakes.

 

[Slow Rider]

okay you're right.

My link provides physics by calculating weight as part of "coefficient of friction"
I'm not a physics person, but more weight = higher coefficient of friction, which is be used for braking.

Your link says weight is not much of concern,.. so I guess as long as the bike has good enough brake, maybe something that's strong enough that you can lock up your front wheel, the weight doesn't really matter?

In conclusion, there may not be significant difference between bicycle and ebike stopping distance? Since ebikes typically have slightly wider tires and good brakes.

LOL, the article I linked was referring to the difference between the weight of a drum and disc brake not being of concern to a "professional downhill bike", nothing to do about the rider weight itself. The calculator does have an "adhesion coefficient" if you want to play around with it.

It would be interesting for a physicist to take two bikes otherwise identical (same brakes, same rider, same tires), and calculate out the affect of the additional mass and greater coefficient of friction, and determine what the theoritical difference in stopping distance actually is.

 

[Manu]

The lower braking distance depends on several factors, speed, full weight, weather, type of terrain or ground, type of tire width, type of brakes (V or disc), type of disc and type of pads for the disc (resin / metal / semimetal / metal) and number of physical hydraulic pressure pistons, the most usual 2 pistons, the most extreme 4 for high speeds and large downhills.


you can have a road bike at 50 km / h with 90 kilograms of weight, in a dry and asphalt environment, with 203 mm disc front and rear, quad caliper, covers 700 x 25 = 20mm contact with the asphalto, for your eyes this is not the best, it is the best, the reality is that the brakes very easily exceed the ability of the tire to grab the asphalt and skid, it does not brake better.It is dangerous for you.
don't brake, skid



Within the disc brake categories you can see the environment for which it is intended, ride, XC, downhill ,

you can increase the standard one degree more but you cannot go from a standard of ride in brakes to put a downhill in ride bike, you will have what I wrote you before .


if you have a very powerful brake system, you need very powerful covers to be able to use those brakes and have a grip on the ground .

If your braking system exceeds your level of wheel grip, the wheel is immediately locked
don't brake, skid,

if on dry ground it does that ...... prepare for worse conditions .

 

[fooferdoggie]

T

If your braking system exceeds your level of wheel grip, the wheel is immediately locked
don't brake, skid,

if on dry ground it does that ...... prepare for worse conditions .

so true I have Magura MT4e and 180mm discs and I don't know if I would want more. braking. I have wrote the discs for a mile down hill with no issues on 14 % grade this morning. though I would not mind a 4 piston brake so I could use 1 finger to brake with.

 

[fooferdoggie]

so true I have Magura MT4e and 180mm discs and I don't know if I would want more. braking. I have wrote the discs for a mile down hill with no issues on 14 % grade this morning. though I would not mind a 4 piston brake so I could use 1 finger to brake with.

 

[Captain Slow]

I have noticed that I go through brake pads much faster on my ebike than on my other bikes. I believe it is due to the higher speed I'm travelling as well as the bike being significantly heavier. I am shocked at how often I have to replace brake pads on my Juiced CCS relative to my other bikes. Definitely there is significantly faster wear.

I would guess I can stop in roughly the same distance as my carbon road bike because instead of rim brakes I have hydraulic discs and the contact patch of the tire is much bigger.

 

[PDoz]

Four caliper disk brakes do not stop you any faster in a sudden emergency braking situation than two caliper disk brakes, using the same size rotors. What they do is build up less heat. This reduces fade due to pad and rotor overheating. This is important on extended downhill riding on mountain bikes which are heavier, spend more time going down hill in extreme conditions are allowed to accelerate and then braked hard repeatedly in downhill riding. Emergency stopping normally does not occur when the brakes are already overheated from constant, hard downhill use.

More importantly, our brake technology is currently better than tyre / suspension tech. You can stand the average emtb on it's nose and hold it there if you have enough traction - the skill / limiting factor us traction.

Sure, my old tech double piston brakes fade a little after about 20 mins of continuous panic...and a day of that can eat a set of organic pads ....nothing that can't be fixed by $20 sintered pads or $120 invested in 4 piston brakes.

Meanwhile...my 2.6 inch dhf's bite a lot harder than my daughters 2.35 's - so I'm more than comfortable riding the same distance behind her than I would on my oldbike. When I can keep up

 

[Captain Slow]

I'm using Tektro sintered/metallic pads. They're actually a metal ceramic compound.

I would estimate that I'm going through a set of front brake pads roughly every 1,500 km's and a set of rear pads every 2,500-3,000 km's. I do have a significant hill both ways on my commute and I ride in all conditions so I'm sure that accelerates the wear.

 

[Captain Slow]

Timpo is your terrain relatively flat or at least no big hills?

 

[Volt_Ampere]

The extra weight does increase stopping distance and wear on the brakes but it's not as much as he says because the weight comparison has to include the rider. So increased weight is no different than a 20 pound heavier rider. (and losing 10 lbs is cheaper than buying a bike that is 10 lbs lighter )