SOHC.co.uk Forums > CB350/400

Shitty front brake.

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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):

--- Quote from: TrickyMicky on April 11, 2026, 12:48:18 PM ---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!.

--- End quote ---

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  ;D ) 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

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