[Closed] Shimano 4 pots - underwhelming

They have more initial bite, but still plenty of modulation, and require less physical effort to get all the power. Was the brake ‘meh’ before the calliper swap? Is it the lever? What is the lever?

Did you bed the pads in?

I have xt 2pot and hope 4 pot. I tried the guides on a mates Capra and almost got sent over the bars by the instant power! Much more initial grab than mine. Down a hill they had the same power, it just came on differently.

The lever is the xt m8000 the bike came with and it worked fine, i just fancied a change to 4 pot for the shits and giggles. I get a good bite with the yellow block but it doesn't bite when the wheel is in. I have tried pumping the lever of couple of times with the block out to advance the pistons but no joy. I am bleeding using Marshys method that has always worked before. I might need to go a proper ride to bed everything in and maybe rebleed (only been up and down the street so far). Just wondering how others got on.

Run the pads through a few heat cycles to ensure that the new pads are well prep'd.

My experience between 2 and 4 pot brakes is that the initial bit of 4 pot is a little less but the power is is greater. Also the amount of required lever pressure is less. I seem to remember an article somewhere explaining all of this, it made sense to me at the time but I don't remember the details.

Are the 4 pot calipers compatible with the levers from the 2 pot brakes? I mean I know they can be connected up just fine, but is the master cylinder in the lever of the correct surface area to drive the 4 pistons in the caliper correctly?

If shimano don't say that this is a supported combination then (assuming all bled correctly) this is probably why they're a bit rubbish.

As per Marshy's video, wet and rub the brake pads together and rinse they'll be mainly bedded in, does sound like a bedding in issue currently.

You have 4 pistons being moved now instead of just 2, so there might be a bit more give in the lever...pressure is spread across the 4 pistons, whereas on the 2-pot system, it just has 2 opposing pistons being pushed.

Make sure pads are properly bedded in.

I run the older XT 4-pots and they have a giggle-indicing amount of power, which is handy as I'm a bit of a heffer.

Do a quick lever bleed using the funnel now and you'll find a few bubbles come up. As they're XT levers check the bite point adjust screw too.
The 4 pots don't bite quite as sharply as the 2 pots but do have the strength as others have said. They just feel a bit different from the 2 pots. To me it's like having most of the Shimano bite with more modulation afterwards.

Sounds like bedding in to me. If they need bleeding, they'll feel spongy. If they feel firm then they don't need bleeding.

I've got the cheap 4 Pot MT500 brakes and they are pretty excellent. I am 80kg and when they are bed in and bled the power is phenomenal, to the point where I am not really sure that I could actually benefit from any more power.

One thing I have noticed is that 4 piston brakes take more maintenance to keep them running really sweet. Need to bleed them more regularly, and they tend to need more caliper alignment to keep them running perfectly as they have twice as many pistons working in unison.

I've just put some zee calipers on M8000 levers and had the first ride this weekend. Initial contact doesn't seem as harsh as 2 pots but there is definitely more power available. Certainly stops quickly and it is very easy to lock the rear so I may go down a rotor size at the back. The rear bedded in quickly as you would expect and the front had the wheel complaining under heavy application on 1:6 road descent when bedding in.

I bled with a cup, lever as far away from the bar as possible and free stroke screw wound out. The rotors had been used with sintered pads before so I cleaned them with IPA first. The pads were Disco Brakes copper free.

Worn disc can cause this.

Shimano discs go concave with wear, and only the top third and bottom third of the brake track will do anything until the pads are worn convex to match, which takes longer than flat, flush surfaces.

Get a known straight edge, say, steel rule or verniers and lay it across the disc, you'll be able to see. Or, take the pads out and look at them. The wear pattern is obvious.

One thing I have noticed is that 4 piston brakes take more maintenance to keep them running really sweet.

I don't recognise this from my own experience.

from reading the original post, it sounds like you bought all the component parts separate and built them up from scratch, could the cause be an element of hamfistery??

No disrespect meant by the way 🙂

For what it's worth, i've been running the old Deore 4 pots for over 12 months now and those things are mega powerful.

Got XT version (same calliper) - no shortage of power, so a bleed and/or bedding in issue I suspect.

Hamfistery...how dare you🤣. It was only a caliper swap. I only  bought a new brake hose as bike discount said on their link with the caliper it was needed....it wasn't, as the caliper came with the banjo bolt (they dont tell you that!) so I used the existing hose and just changed the banjo.In all seriousness I will see how they bed in after a ride. Rotors are fine but i did clean them with isopropyl so they may need a bit of pad material laid back down on them again. Its probably a bit of that and maybe another bit of a bleed. I was just expecting to be launched into orbit when grabbing a handful of lever..but alas I feel I just stop no better than i did before. Hopefully they will bed in nice.

Cheers.

Mate has xt 4 pots and i have m8000 2 pots. The levers look slightly different. Maybe double check compatability, it could be how much fluid they move with what degree of pull.

Can we finally put to bed the incorrect information about levers pushing different amounts of fluid? I’ve used various Shimano levers with 2 and 4 pot brakes and there is no difference. I’ll repeat that - no difference.

If you don’t believe me, then look at the fact that many of Shimano’s 2 and 4 pot brakes share the same lever.

So, to answer the original question - something is wrong with your brakes if they don’t feel powerful, as Shimano 4 pots are some of the most powerful available. The problem, though, WILL NOT BE YOUR LEVERS.

JP

Assuming they are servowave, and aren’t leaky.

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I'm going with pads not bedded in, I changed a two pot caliper for a four pot and it was far more powerful, but like all brakes it takes time to bed in the pads.

I’m going with pads not bedded in

It does sound that way.

I know Shimano have different disc thicknesses for different brakes, could this be factor? Similarly they also have two different sizes of brake pipe/tube.

I fi d Shimano brakes ok to point and then they have a frustrating period before you have to junk them.

Rotor thickness shouldn't affect brake performance with new pads unless they are binding (i.e. the rotor is too thick to fit the pads in).

Brake hose should have no effect so long as it's not leaking.

If it's a bleed problem, you will have a soft lever feel. If they are properly bled, the lever should be very firm once the pads start to bite.

If you have a solid feel at the lever but they lack power, either they haven't bedded in properly or the pads have been contaminated when you bled them. I would remove the pads, clean them with dish detergent and boiling water, then sand the contact surfaces, then do the same with the rotor. Then refit the pads, find a big hill, and bed them in by speeding up to 15 mph or so, then braking hard for several seconds, speeding up again, and repeating. You should feel the brakes improve after 10 cycles or so as the pads bed in.

.......so everyone who said pads needed bedding in, raise your hand. Well done, go to the top of the class.

Went a ride today, first down hill section I took it handy and they seemed OKish, then there was a long downhill fire road that let me do a good 4 or 5 fast hard pulls and by the bottom of this they were much better, performed well for rest of ride after that.

normally I can bed my pads in with a spin outside the house, these just needed more oomph.

Cheers all.