Topic: How can I get these brakes to stop better? ('75 750K)

[Jayelwin]

I've fully restored to pretty much stock my '75 and everything is great except the brakes. I recently picked up a 2007 BMW and it stops like it hit a brick wall at the slightest touch. Now in contrast I realize I really have to squeeze HARD and pray if I don't want to hit the guy in front of me when I'm on the 750. So I thought maybe I was spongy so I flushed and bled and now I'm running all new DOT3 fluid and it really only helped a little bit. When I squeeze hard I can see the caliper move a hair outwards.

Now I know you can't compare two pistons each on two vented disks to a single piston/solid disk in stopping power. Did people in the '70's just suffer with crappy brakes?

I can't recall what pads I have mounted but they're fairly new. Are there recommended pads with more bite? Is there something I can do to the disk to also stop better? I'd prefer to keep it all stock in appearance.

Thanks.

Josh

[MikeSimon]

Yes, I think with our 70s bikes we have to suffer with "crappy brakes". I did improve the stopping performance somewhat on my 78 R100S by using new and improved brake pads. Don't remember right now which brand it was. But in general, you will have to put up with this unless you redo the whole brake system, i.e.: dual rotors and different master cylinder. Then again, this is all part of riding a vintage bike. even with one of my CBXes, I have no ambition to keep up with a squid on a modern 600 crotch rocket. That's not why I have it.

[bryanj]

Its an early 70's bike and you are expecting too much.

Hoses good
Master cleaned and rebuilt
Caliper cleaned and rebuilt
Swinging pivot free and greased

Will get you the best possible.

If you don't believe me try an early 70's Triumph or Norton!!

[slikwilli420]

How about new calipers? Could adapt some Lockheed brakes easily and it would make a world of difference and look period.

[Kevin D]

you are expecting too much

+1

Here are some vendors offering modern and upgraded parts for our CB's. The front disc at David Silvers is advertised to be made with "modern materials" giving a "superior brake".
I would like to see some performance tests for these various items. The cast iron discs from RPE are a recent and tempting offering.
I have done exactly as BryanJ has suggested.

https://www.davidsilverspares.com/CB750K5-FOUR-1975-USA/part_273692/

http://www.slingshotcycles.com

http://www.vintagebrake.com/index.html

http://www.ebay.com.au/itm/Cast-Iron-Brake-Disc-Honda-CB750K-Four-1969-76-/272383743957?hash=item3f6b5617d5:g:qucAAOSwYIxX4Sp4

http://www.vinmoto.org/gallery/v/VinMoto-Garage/album03/Godfferys-Garage-123/

EDIT: almost forgot, I have braided stainless brake lines from HEL, and a phenolic brake piston from Godffrey, keeping stock look.

[Garage_guy_chris]

Could add a dual disc conversion...



On my bike im running:
-75-77 A/F 42mm calipers
-Drilled discs
-SBS HF Ceramic Brake Pads - 501HF
-Stainless braided dual lines from master
-02-09 VFR800 14mm master

It stops pretty good, I have ridden modern bikes and they are at least as good as most modern non supersport RR bikes

[Nic]

In the 70s we added another disc, it's soooo much better than one, I recently bought a cast iron disc and had it on one side and took the other off, still very disappointing, put the twins back on, very happy, very confident, sure, not like modern but as far as I'm concerned, good enough.

[scottly]

Dual discs using stock parts will double the braking. Any 750K rotor will fit, and in your case a K3-K6 caliper will match your K5 caliper. The stock 14 mm master cylinder will work fine. The only snag is the speedo drive, and there are several ways to do it. Dual disc conversions have been done this way since the '70s. 

[Nic]

Dual discs using stock parts will double the braking. Any 750K rotor will fit, and in your case a K3-K6 caliper will match your K5 caliper. The stock 14 mm master cylinder will work fine. The only snag is the speedo drive, and there are several ways to do it. Dual disc conversions have been done this way since the '70s. 

You say double the braking, I suppose that makes sense but IMO it feels much better than double. I just think double what the one disc does does not sound like it would still be enough?? To me the added disc really improves things.

[scottly]

I agree that a second disc is a very noticeable improvement, in fact you will likely only use about 150% of the 200% increase in braking unless in a panic-stop situation.

[Nic]

I agree that a second disc is a very noticeable improvement, in fact you will likely only use about 150% of the 200% increase in braking unless in a panic-stop situation.

Agree mate, when I had the single cast iron disc on I had to pull so hard on the lever, with the two Honda discs you don't have to use more than two fingers most of the time, beautiful feel too I reckon and that's with the stock caliper, ah, I mean M/C rebuilt, if I adjust the calipers so the inner pad is scraping the disc i get quite a firm lever, I prefer to de adjust it a bit so I get a little play in the lever and a nicer feel.
With only the one disc these bikes are unsafe.

[scottly]

When I fit the K7 front forks on my bike, I found that the dual K1 calipers wouldn't bolt up, so I mounted one of the cast iron rotors that came on the K1 setup with the K7 caliper, and was VERY disappointed the first time I needed to scrub off speed in a hurry!  

[Nic]

When I fit the K7 front forks on my bike, I found that the dual K1 calipers wouldn't bolt up, so I mounted one of the cast iron rotors that came on the K1 setup with the K7 caliper, and was VERY disappointed the first time I needed to scrub off speed in a hurry!

Yeah, me too.

[PeWe]

It is dangerous to get used with another bike that have working brakes. CB750 must be ridden different, do not brake, see the openings and twist the throttle. Use gear box a lot and do not ride exact behind your buddies, must be displaced sideways.

I use DSS aftermarked MC (cost  like the repair kit for OEM MC) and their aftermarket disc. The right caliper holder must get 5mm spacers to make caliper parallel with rotor. Speedo cable routed outside fender.

[becken]

As per Michael at Vintage Brake, I installed Ferodo organic brake pads, a Galfer one piece brake hose and a 11mm Brembo master cylinder. I still am using the original single disc and am extremely happy with the front brake. The master cylinder has a mirror mount and a brake light switch built in.

[my name is nobody]

Its an early 70's bike and you are expecting too much.

Hoses good
Master cleaned and rebuilt
Caliper cleaned and rebuilt
Swinging pivot free and greased

Will get you the best possible.




This has been my experience with my K5. I'd think hose condition and expansion resistance
would have a noticeable effect on stopping ability. I haven't tried, but I'd expect mine would
 nearly lock the front wheel if asked. Dual disc or modern system comparison is apples to oranges
IMO..

[bryanj]

Forget the cast iron only difference is they work in the wet which locks the wheel and you fall off, got the tee shirt and video for that one

[slikwilli420]

Really odd that everyone dogs the cast iron option. Cast iron is a superior rotor material. SS is use on bikes because people don't like to see rusty brakes.

Make a few adapter plates and bolt on some Grimeca/AP Racing 2-piston calipers and you will wonder why you worried about the stock crap for so long. These calipers are superior to anything of the period and went on every race bike until the mid-80's. If you want ultimate period stopping power, look no further.

The issue with the stock caliper is the design, so nothing you can do will make it appreciably better. There is too much flex to expect them to perform like a better caliper.

If you want to improve further, ditch the stock SS disc, at least for a modern EBC replica. The stock SS was very prone to glazing and once that happens, no amount of caliper/pad pressure will help you stop.

Between brakes and suspension, you can really wake these bikes up, but need to be willing to drop a little coin to do it, or continue to live with the bike the way it was born.

[flybox1]

My dual front rotor setup was a huge improvement over stock.
14mm piston MC
Godfferys 4mm drilled rotors
SS lines from Slingshot.
EBC Organic pads FA013 (no, they do not squeal)

[Maximum Carnage]

I’ve been considering adding a second disc/caliper to my 1971 CB750, don’t mean to hijack but what other models will fit mine?

[Rookster]

The lockheed calipers are great but they don't fit on the stock front end.  There is about 1.5" between the disk and the spokes.  The lockheed caliper I have measures about 1.75" from the center line between the pads to the back of the caliper.  The CB750 forks are very narrow which limits the ability to use better 2 piston calipers.

Scott

[slikwilli420]

A GL1000 swap will fix that and more. Then you could either upgrade the calipers or use the GL ones. A bit of a rabbit hole, but to make these things really work properly that is what you are up against. Either that, or enjoy them for what they are, or buy a new bike.

[rotortiller]

You have a few of choices, increase the friction area, increase the caliper puck hydraulic working area,  up the hydraulic pressure or do various combos. LOL

Add a disk or fit alternate caliper
Different master with smaller piston.

[TwoTired]

In the era these bike were introduced, a disk brake that was sensitive was considered dangerous, as locking up the front wheel was not welcome, particularly in corners.
I think Honda made them the way they were as safety notion, as it is better to stay upright during hazard avoidance than slide on the foot pegs.  The older drum brakes people were transitioning from didn't have quick stopping power, even with high hand effort.

Be wary of old rubber brake lines that actually siphon off hydraulic pressure meant to move the brake puck, to allow the lines to expand in size.  With SS lines and a brake system refurb, I was able to get the front tire to squall if I really squeezed hard on the lever (all fingers).  Not sure I wish to ask more than that on a street bike with unreliable surface traction quality.

The edge of traction is about all I ever wanted from the front tire in an emergency braking maneuver.  Squealing is a nice audible warning to have, I think.

While two finger braking may be considered attractive.  Are panic avoidance stops conducive to two finger leisure operation?  I'd rather plan for the extreme at the expense of less effort in normal operation.  <- my viewpoint.

[scottly]

I’ve been considering adding a second disc/caliper to my 1971 CB750, don’t mean to hijack but what other models will fit mine?

You will need a caliper and mount from a K0-K2 750; from K3 up they used a different mount where the caliper mounts to the fork leg. The earlier style has a "C" shaped mount compared to the later "T" shaped mount. Any year 750K rotor will work.