SOHC.co.uk Forums > CB350/400
CB400F2 - front brake parts what's missing?
McCabe-Thiele (Ted):
The front brakes aside from the disc itself was all in bits in various boxes so yesterday decided to see what is obviously missing with a view to assembling the unit.
I have photographed what I have - so far I need the to replace the following that is apparent at first glance.
No mounting bolts or nut to attach the support to the front fork including associated washers. No bolts to clamp the two halves of the caliper together. The odd spring and long screw has no nut/end plus the screw is out of shape.
It came with a replacement piston as the old one is badly damaged - it has a brass coloured end part - I am assuming that that goes against one of the brake pads. I have no pin between two pads mentioned in the manual but the roll pin type locaters for the pads are OK. I have new DS pads with the nylon pad cushion. DS I guess will be able to supply the bits that I have mentioned as missing & the long bent screw.
Anything else I need to worry about - the caliper bore looks good I have no idea if the piston seal is the original or has been replaced - it looks as the design does not include what I would describe as a dust/water seal/bellow.
.
.
.
.front brake parts by Macabe Thiele, on Flickr
K2-K6:
"Anything else I need to worry about - the caliper bore looks good I have no idea if the piston seal is the original or has been replaced - it looks as the design does not include what I would describe as a dust/water seal/bellow."
Yep, there's a complete absence of weather/dust seal in these original designs. And one of the considerations in maintaining them.
Seal groove scrupulously clean, new ( soft and chewy :D seal) and silicone grease to assemble it is all that's needed.
The piston "cover" plate effectively tries to compensate for the caliper swinging in an arc due to pad wear. Tries to allow the moving pad to remain aligned to the disc rather than be skewed by the flat face of the piston as the caliper effectively moves in an arc. This partially successful, but a compromise certainly ;D
McCabe-Thiele (Ted):
--- Quote from: K2-K6 on October 12, 2020, 01:37:39 PM ---"Anything else I need to worry about - the caliper bore looks good I have no idea if the piston seal is the original or has been replaced - it looks as the design does not include what I would describe as a dust/water seal/bellow."
Yep, there's a complete absence of weather/dust seal in these original designs. And one of the considerations in maintaining them.
Seal groove scrupulously clean, new ( soft and chewy :D seal) and silicone grease to assemble it is all that's needed.
The piston "cover" plate effectively tries to compensate for the caliper swinging in an arc due to pad wear. Tries to allow the moving pad to remain aligned to the disc rather than be skewed by the flat face of the piston as the caliper effectively moves in an arc. This partially successful, but a compromise certainly ;D
--- End quote ---
Thanks for that info - the long bolt with a spring loaded adjustment screw seems a very odd thing to find on a disc brake as are the Pad A & Pad B set up. I guess twin pistons was just too expensive an option. It's not very self adjusting looking set up I have to say but assume it works reasonably well.
K2-K6:
Yes, bit of a peculiar design overall.
The screw holds the "static " pad only just clear of the disc so it's ready to be squeezed. Without it any disc runout would try and pull the caliper over and so push the piston back in and requiring the rider to pump the brake when needed.
Effectively a floating caliper as used on many cars nowadays (albeit on parallel sliding pins) principle isn't bad just a little compromised by having to swing.
The reason why, it's more of a "developmental" guess, but seems evolutionarily from drum brakes of the time (remember this type of caliper on the 750 was essentially the first mass produced, volume front disc brake) ie. It effectively mounts to a drum brake torque arm in it's layout, also possibly not having the clearance between fork leg, disc and spokes to get a opposed piston caliper in the gap. Early test bikes of the 750 showed more or less 450 DOHC cycle parts with drum brake fitted. So possibly that restricted architecture that forced something to fit in existing space.
Then of course it was easy for following designers to be more adventurous by pushing the forks outward and fitting larger caliper units.
McCabe-Thiele (Ted):
I didn't mention the odd split pin either! My pads didn't come with a split pin. Not sure what the purpose of the pin is?
Navigation
[0] Message Index
[#] Next page
Go to full version