Shitty front brake.

[ComfySofa]

Hi there, not been on for a while. Still got the bike, doesnt get used much atall but its my old man's bike so its not going anywhere in the near [or far] future....anyway...ive resto modded mine a little bit [all documented somewhere on here] - as above the front brake is pretty shit....is there an alternative, resto mod or something from another model which does the job a bit better....i have changed the master cylinder for something a bit newer (i had to as i switched all the switch gear to motogadget).

If not its not the end of the world, just wondered...ironically the rear drum brake is fucking awesome...

[Bryanj]

Only easy mod is complete front end  from a 400 twin, the 400 is the odd ball for front end among the fours, its the same as the 250/360 G5

[taysidedragon]

My 400f front brake is OK. It'll never be the same as a modern opposed piston, double disc brake. There is a good long thread on here about improving the front brake, worth a read.

Basically, overhaul the front caliper, make sure that the piston, seal and bore are all clean.
Clean the friction surfaces of the disc with fine emery cloth and wipe after with white spirit and dry. Reassemble with good brake pads such as EBC Organic or Brembo. Braided brake hoses expand less than old style rubber hoses so give more bite, IMO.
Adjust the brake pivot as per the manual. Test ride, find a quiet road and bed the new pads in.

Should be a better brake than you have now.

[McCabe-Thiele (Ted)]

Yes the single front disc brake on a 400 is never going to feel like a modern twin disc set up with multiple caliper pistons.

That said with correct adjustments, free pivots plus modern friction materials they can work satisfactorily.
I guess most owners of older bikes have developed appropriate riding styles with anticipation skills to match the  older braking ability. I found the DS master cylinder improved the general feel of the front brakes with much reduced free play.

[TrickyMicky]

When you say that you changed the master cyclinder for something newer, did you check that the bore size is the same as the original?  If the bore size is bigger, then it will need more lever pressure to achieve a brake force.  If you apply 50lbs force to a piston of 1/2 sq. inch you will get a line pressure of 100PSI.  If the piston has an area of 1 sq. inch then you will only get line pressre of 50PS!.

[Mikep328]

The front brake CAN be pretty good.  As noted there are threads re this and a search will find some fairly lengthy ones.  I managed to get my front brake from "worse than the rear brake" (yes, really), to perfectly acceptable using all stock gear other than new non-expanding brake lines.  The key is to use the best pads for the job and correctly bed in the new pads.  I tried 5 different types of pads and found the best on my 400F to be Vesrah organic. 

FWIW, the stopping distance for the 400F from a magazine road test back in the day is IDENTICAL to the stopping distance on one of the midsize 2021 Hondas - can't recall which one but that info is also in the threads on the front brake.  IOW, the idea that these bikes always had poor brakes is an internet revision of history.

[McCabe-Thiele (Ted)]

When you say that you changed the master cyclinder for something newer, did you check that the bore size is the same as the original?  If the bore size is bigger, then it will need more lever pressure to achieve a brake force.  If you apply 50lbs force to a piston of 1/2 sq. inch you will get a line pressure of 100PSI.  If the piston has an area of 1 sq. inch then you will only get line pressre of 50PS!.

Pretty sure the bore size is a tad larger, someone here will know the difference, I have no difficulty in applying any extra pressure, the reduction in free play was well worth it. My old master cylinder was corroded and seized. I have new standard brake hoses not braided with Silicone brake fluid.

[ComfySofa]

Thanks for all the replies....it had seized up so i did clean it out as it was binding...when i did the initial renovation i got the caliper blasted and powder coated. Its a few years ago but i did get the softtest pads i could get as its not doing any miles as such. The master cylinder i think is from a cbr of some sort (Roo recommended the one ive got on there)

It could be that its not bedded in. Im not expecting it to stop on a dime but the moment its almost non existant but as the back brake is so good its not the end of the world....as for replacing the whole front end...maybe a little bit of overkill but the i do like upgrades (thanks for the tip Bryan) and again thanks again for the engine rebuild back then...still, very much appreciated.!

[K2-K6]

As already noted, details in other threads discuss at length.

If not certain of caliper status though, ANY impairment of piston seal and it's ability to function correctly (both in pressure & withdrawing piston) will play havoc with the brake getting anywhere near its potential.

That seal groove must be scrupulously clean to work correctly. If the piston doesn't retract on pressure release from letting brake lever go, it'll always drag, heat the disc, glaze both disc and pad surfaces and never give real bite that's anything convincing in brake terms.

I assemble using silicone grease on that seal (different opinions available  ) that to exclude any incidental water/moisture accumulation from use and storage.  Ultimately this controls the corrosion potential at that site, unlike using brake fluid for assembly.  These caliper have no real weather seal there, unlike many more current caliper design. It's all down to that assembly integrity. 

You can see the effect on a MOT brake tester, car or bike, when calipers are free to work as they should. That's as opposed to example with compromise in piston stiction during use.

Built correctly, it'll brake through storage periods too, compromised though, and it'll largely be ineffective at any use time.

These system have design and potential to function well, but without braking power in significant excess, they'll show any compromise easily.

[Bryanj]

My mot tester always commented that the front wheel of the hondas i took in always span freely when lifted off the floor

[Athame57]

I feel the 400/4 has brakes that suit it myself.  I had to slam on the anchors in a hurry just the other day, yet another London food delivery bike jumping the lights, they will even do that without lights at night. Perhaps I should not bother braking? 

[Johnny4428]

One rule for food delivery drivers and another for us law abiding citizens.😜