The disc brakes on my last 3 mountain bikes have been so good that with 1 finger I can lock my front wheel.

I'm unable to do that with any of my rim braked road/tri bikes.

I'm not "pro disc brake on the road", in fact I don't think they are necessary on the road, but my disc brakes on my mountain bike are so good I could throw myself off if I brake too hard.

Interesting. That's definitely not the initial experience I'm having. I need to really crank down on the levers to lock up the rear wheel.

What type of disc brakes did you go with? Mechanical or Hydraulic?

Do they feel spongy at all? Or maybe just not grippy?

I've had a mix of Shimano levers/calipers. I've had Shimano M486, M505 and M8000 all of which have been excellent but have also always had good shimano rotors.

Ultegra 8070 hydraulic calipers with Ultegra R800 rotors.

Not spongy. Definitely not grippy. I haven't tried cleaning the rotors but assumed they were ready to go since Excel set the bike up before shipping.

Sounds like something is wrong. Did you bed in the pads?

Nope. Just put everything together and literally went for a lap around the block to check it out. What's the process?

What I just learned is you never spray WD40 on your chain, in the direction of the brake disc. I though for sure the hydraulic fluid had leaked out, and I could not lock up the brake anymore. But a friend said the pads just soak up any lube like that, and they are dead after that. Haven't changed them yet, waiting for him to come over for a beer. I know I will screw it up, I have learned everything about these brakes the hard way thus far...

Something is definitely wrong. I can stop on a dime w/ discs

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IG -frebay | Strava

That's what I was expecting. I'll get my local mobile bike mechanic to stop by and check it out.

I remember my first disc brakes on a mountain bike years ago. I was descending wondering what all the fuss was about as they were performing just as you describe. It was probably half way through the second descent that they bed in and nearly through me over the front. Night and day difference! Awesome stopping power. I would imagine it would take a lot longer to bed in on the road or gravel trails. I don’t know of any tricks to speed up the process. Maybe you just need to find a big hill to generate some heat?!

my bet is this was not done...

or this is mechanical disc which can be quite picky to level pull setup and housings used

Bedding in the pads doesn't affect initial bite. It's done to evaporate the binders in the slurry from which brake pads are extruded. If you don't do this, the binders heat up and outgas under sustained braking which creates a film between pad and rotor. Manifests itself as a drop in braking power the longer the brakes are applied. ETA: you generally don't need to do a specific bedding protocol on street vehicles because braking during normal driving will evaporate the binders at a slow rate that doesn't impact braking performance. Same should be true for bicycles - unless your very first application of the brakes is on a long descent, the less critical braking beforehand takes care of the binders. Race cars/bikes it's necessary, there often isn't enough shorter braking done before the need for a sustained deceleration.

I'd guess contaminant on the pads/rotors as other posters have said.

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Brian

Gonna buy a fast car, put on my lead boots, take a long, long drive
I may end up spending all my money, but I'll still be alive

You absolutely need to bed them in. It takes dozens of progressively faster brakes to a near stop to get them right. You do not want to hard brake to a stop with the pads touching the disc or it'll howl till that lump of pad material wears back. Once they get a nice sheen of pad material on the discs, they'll work as everyone describes above. Carbon clinchers will be no match for well sorted discs.

...and also as said above, keep all oils/lubes/grease away from the discs (including from your fingers). If you do so accidentally, fully clean them before hitting the brakes.

Finally, yes, as you said...be careful not to pull them when the wheel is out. You can get plastic spacers to jam in there, but anything thick enough to wedge in without falling out will work. You can sometimes get away with pressing them back in, but a quick bleed is a good idea.

Enjoy the RLT! I have a BSB for CX and it is a great ride. I have definitely thrown myself over the bars in a hard brake. Oh look, I'm racing that same course on Saturday...

My disc brakes have exceeded my expectations on how good braking is.

However, they scare the crap out of me if i have to service them. The mechanic said “oh they are just like car brakes” ... and I laughed and said i don’t know how those work either :-P

Hope mechanic gets you sorted

#1 isn’t exactly a news flash, you can pry to caliper open and it’ll reset.

Google the protocol to bed the brake pads in.

Did an edit as you were typing - less demanding braking will take care of this. So unless you just put in new pads before a downhill race, shouldn't be necessary. I campaigned a Formula Ford for a few years, and yeah, always bedded new pads. For me, maybe 5 or 6 sustained brake applications with easy cruise between and after the last one did the job.

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Brian

Gonna buy a fast car, put on my lead boots, take a long, long drive
I may end up spending all my money, but I'll still be alive

I bet the op has air in his lines. Bleed them. He should also bed the brakes.

Possible but not likely. Air in the lines would result in a spongy brake lever as the air compresses. My lever feel is firm but there is just no grip. It's currently like shitty pads on carbon clinchers in the rain - you are squeezing hard but not getting much out of them. I'll try the bedding process but need a massive improvement to meet expectations.

IME doing brake jobs on cars, your symptoms sound like bad pad material. But, given your prior post, your pads are Ultegra.

Also, I am not sure that "bedding in" could remotely work on a bike. When you do the process on a car, you are doing max braking a few times to generate major heat on the pads & rotors to transfer some pad material to the rotors. I do not think you can generate that much heat on a bike.

I would not discount air in the lines.

The other thing I would try is clean the rotor and pad surfaces with an aggressive solvent.

Is there a reason you are using road rotors and calipers on a mountain bike?

I see the rotor comes in a 140mm and 160mm. Which ones do you have?

It's a gravel bike but regardless, I have to trust Niner for putting together a decent build package with appropriate parts. These are 140mm.

I missed the part about it being a Gravel bike, I saw Niner RDO and I thought mountain bike. That makes sense.

Why do we need to second guess everything? The manufacturers think that bedding in works so that should be the course of action. The OP can read the instructions for their brakes, follow them and report back. Until they report back everything else is just talk.