Author Topic: a thinner,lighter repro front brake rotor work on a CB350/400F front wheel ?  (Read 8264 times)

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Offline grcamna2

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I have a CB400F front wheel w/ stock 4 bolt mount front rotor and wondered if anyone makes a repro that mounts with the same dimensions/size,etc. but is thinner/lighter ? The stock disc is heavy stainless and i think an improvement(lightened cast iron?) would help.
« Last Edit: October 27, 2016, 07:07:36 AM by grcamna2 »
75' CB400F/'bunch o' parts' & 81' CB125S modded to a 'CB200S'
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Offline flybox1

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Offline grcamna2

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75' CB400F/'bunch o' parts' & 81' CB125S modded to a 'CB200S'
  I love the small ones too !
Do your BEST...nobody can take that away from you.

Offline Godffery

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Offline 754

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Cast iron and stainless pretty close to same weight.. I think I would run a much thinner Stainless , than a really  thin cast iron..
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Offline Bodi

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Why does Honda specify minimum thickness 6mm - if this is a stock disk thinned to 4mm, what makes it immune to that specification?

Offline grcamna2

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Why does Honda specify minimum thickness 6mm - if this is a stock disk thinned to 4mm, what makes it immune to that specification?

I wouldn't even mind if it was just drilled w/o being thinned,I guess it would still be lighter.
« Last Edit: October 27, 2016, 03:01:13 PM by grcamna2 »
75' CB400F/'bunch o' parts' & 81' CB125S modded to a 'CB200S'
  I love the small ones too !
Do your BEST...nobody can take that away from you.

Offline robvangulik

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Just drilling  made 1 disc 750 grams lighter, so both discs together made a difference of 1,5 kilogram.

Offline slikwilli420

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Why does Honda specify minimum thickness 6mm - if this is a stock disk thinned to 4mm, what makes it immune to that specification?

Using two of them.
All you gotta do is do what you gotta do.

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Offline MoMo

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Bill, I have a pattern to drill a 400f rotor.  I've done a couple, doesn't take all that long and eats up one cobalt bit.   If you like I'd drill yours gratis...Larry

Offline 754

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Honda over engineers everything, partly due to liability.
Pretty sure they like the piston to not go out further than need be...
Honda does not recommend it, but as with most racing stuff , there is always some sacrifice...so probably shorter component life. Hi performance modded stuff should be inspected more frequently than stock.

Note how thin most rotor are now, and many are floaters to avoid warping..? Stock Honda discs from the seventies are Stone Age...
Maker of the WELDLESS 750 Frame Kit
dodogas99@gmail.com
Kelowna B.C.       Canada

My next bike will be a ..ANFOB.....

It's All part of the ADVENTURE...

73 836cc.. Green, had it for 3 decades!!
Lost quite a few CB 750's along the way

Offline grcamna2

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Honda over engineers everything, partly due to liability.
Pretty sure they like the piston to not go out further than need be...
Honda does not recommend it, but as with most racing stuff , there is always some sacrifice...so probably shorter component life. Hi performance modded stuff should be inspected more frequently than stock.

Note how thin most rotor are now, and many are floaters to avoid warping..? Stock Honda discs from the seventies are Stone Age...

The stock are heavy but they sure have lot's of extra life built into them  8)
75' CB400F/'bunch o' parts' & 81' CB125S modded to a 'CB200S'
  I love the small ones too !
Do your BEST...nobody can take that away from you.

Offline Godffery

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Why does Honda specify minimum thickness 6mm - if this is a stock disk thinned to 4mm, what makes it immune to that specification?
Brake Rotors were relatively new technology in the 1970's so they erred on the side of caution, by the late 70's early 80's they already started getting thinner and drilled.  I have done allot of these and found that 4.3mm is the "Sweet spot" and now I do all my drilled & thinned rotors to that thickness. Also; the number, size & location of holes is critical as well.

Offline grcamna2

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Why does Honda specify minimum thickness 6mm - if this is a stock disk thinned to 4mm, what makes it immune to that specification?
Brake Rotors were relatively new technology in the 1970's so they erred on the side of caution, by the late 70's early 80's they already started getting thinner and drilled.  I have done allot of these and found that 4.3mm is the "Sweet spot" and now I do all my drilled & thinned rotors to that thickness. Also; the number, size & location of holes is critical as well.

Thanks Jeff,PM sent.
75' CB400F/'bunch o' parts' & 81' CB125S modded to a 'CB200S'
  I love the small ones too !
Do your BEST...nobody can take that away from you.

Offline Godffery

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Why does Honda specify minimum thickness 6mm - if this is a stock disk thinned to 4mm, what makes it immune to that specification?
Brake Rotors were relatively new technology in the 1970's so they erred on the side of caution, by the late 70's early 80's they already started getting thinner and drilled.  I have done allot of these and found that 4.3mm is the "Sweet spot" and now I do all my drilled & thinned rotors to that thickness. Also; the number, size & location of holes is critical as well.
Thanks Jeff,PM sent.
If you sent a PM to me, I don't think I got it...?  If you'd like, you can contact me directly at jstephens7@wi.rr.com 
« Last Edit: October 29, 2016, 03:47:39 PM by Godffery »

Offline grcamna2

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I'm still waiting for a reply to my last email Jeff,thanks.
75' CB400F/'bunch o' parts' & 81' CB125S modded to a 'CB200S'
  I love the small ones too !
Do your BEST...nobody can take that away from you.

Offline Godffery

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I'm still waiting for a reply to my last email Jeff,thanks.
Oh, ok. Got that and just replied.

Offline grcamna2

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I'm still waiting for a reply to my last email Jeff,thanks.
Oh, ok. Got that and just replied.

thanks
75' CB400F/'bunch o' parts' & 81' CB125S modded to a 'CB200S'
  I love the small ones too !
Do your BEST...nobody can take that away from you.

Online RAFster122s

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Slotted will help with water evacuation for wet braking improvement while brake performance can be improved with proper application of holes for gas and material evacuation.
David- back in the desert SW!

Offline sixthwisconsin

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I have Jeffs rotors on both my 550 & 750f.
Highly recommended.



« Last Edit: November 04, 2016, 08:48:46 AM by sixthwisconsin »

Offline grcamna2

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Those look good sixthW  8) I'm purchasing from Godfferry also.
These oem machined rotors are looking like a much better choice than some chinese repro.
« Last Edit: November 03, 2016, 08:41:46 PM by grcamna2 »
75' CB400F/'bunch o' parts' & 81' CB125S modded to a 'CB200S'
  I love the small ones too !
Do your BEST...nobody can take that away from you.

Offline Godffery

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 Thanks for posting Pix, I always love to see these on the bikes!
I hope to be starting an album of Customer builds on my web site soon, I trust you won't mind me using these Photos...? 

Offline sixthwisconsin

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Let me get you a couple of beauty shots of the whole bikes complete. If the OP doesn't mind, I'll just post them here for you to grab.

Offline grcamna2

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Let me get you a couple of beauty shots of the whole bikes complete. If the OP doesn't mind, I'll just post them here for you to grab.

Sure,love to see them myself.
75' CB400F/'bunch o' parts' & 81' CB125S modded to a 'CB200S'
  I love the small ones too !
Do your BEST...nobody can take that away from you.

Offline flybox1

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'78 750K (F3 engine) PD42b's, Modified airbox w/K&N  filter, 40/110 jets, 1 needle shim, IMS@ 1 turn out. Kerker + Cone 18" QuietCore

Past Bikes
1974 550K0 (stock), 1973 CB350F (stock), 1983 Yamaha XS400K (POS)
77/78 cool 2 member #3
"Knowledge without mileage equals bullsh!t" - Henry Rollins

"This is my CB. There are many like it, but this one is mine…"