The rear tire always skids when I panic stop


I live in the Pacific Northwest and the roads are always wet right now. On every ride I will have a panic stop and the rear wheel will skid. I have been riding bikes for 35 years and have always had the habit of squeezing both levers for maximum braking. But these new fangled disk brakes are so powerful that I am locking up the rear wheel with very little effort. I am thinking I might just buy some slick tires for maximum contact with the road. Is anybody else having this problem?
That phenomenon is well known in the automotive industry. Braking causes weight transfer to the front, the rear tends to lift and lock and then lose control. Before the era of ABS technology, they dealt with it by reducing the braking force at the rear to prevent rear skid and made the front stronger (with larger and vented front disk and non vented rear disks in most cars now). Same principle is now seen on many e-bikes where the front disks are slightly larger than the rear. The car industry further refined it with ABS technology where each wheel is prevented to lock independently.
Try using only a couple fingers on brake lever. Disc brakes are very responsive to lever movement. Right now I'm learning how to not rest my fingers on St2 brake lever. As only the slightest pressure activates regenerative braking.
Definitely recommend you train yourself to perform emergency stops under safe conditions and develop muscle memory and instinct, before you need to do a real one. It'll pay off in spades later.
Hi @siclmn, I remember having this feeling too when switching from rim brakes to mechanical disc brakes and now with hydraulics it's even touchier. A couple of things come to mind... I now brake with just one or two fingers and have trained myself not to pull so hard, as @britannic said, it might just be a matter of practice and building muscle memory. The second idea that comes to mind is asking your local bike shop to clean your brakes. I found that after visiting one shop a while back my cleaner brakes went from locking up to being smoother, quieter and almost slower than before. I had to actually hold them for a while as they didn't lock (which I actually disliked but could be good in your situation). I guess this isn't super helpful, just sharing some of my experiences. Also, I've seen with some mechanical brakes on bikes I reviewed where there's an inline spring antilock thing that ensures you won't lock up. You cans see it on the fifth image for the Revelo Flex here. They call it an Inline Power Modulator from Shimano and it looks like Tektro has one too called the A.M.S.

Being that you posted this in the Stromer forum I'm going to guess that you have a Stromer. A couple of items you might want to consider. First I would check the regen settings, keep in mind that your pulling both brakes and the motor is slowing you down on top of that. This could cause your brake to lock up prematurely if the regen is set to high.

You should also try to use the front brake a bit more than the rear. I think most riders are used to using the rear brake out of fear of flipping over the handlebars, but the front brake actually has more stopping power, especially when coupled with regen on the rear wheel.

Let me know if you'd like help with the details on adjusting regen and I can locate the tech docs. Be safe out there!
It's the technique, not the bike or the equipment. Your front wheel has 80% of the stopping power, the rear is 20% and if you grab both equally you will lock the rear, every time. Harley riders do this A LOT! Think of the rear brake as a stabilizer, not your primary braking force. Front to slow, rear to stabilize. That's all there is to it. People fear the front brake because they are afraid it will lock up and they will go down. The key to braking any 2-wheeler is to stop in a straight line not when the bike is leaned.
Saddle higher than the handlebar and full suspension fork = Handlebar is diving whilst sharp breaking. Most body weight on the wrists. Less weight on the rear wheel = rear tire skids...


Now try the same on this bike:


BTW: Even full motor brake mode on a ST2s will not lead to a skidding rear wheel.