Topic: Vintage Disc Brakes with Modern Performance - How to Accomplish?

[noose74]

was this a plug and play swap? no need to modify anything? what bike and year do u have?

[tortelvis]

Biggest problem with "vintage" discs in the wet is that most are made from really poor material for a rotor to be made from. Hondas in particular use a nice shiny durable long lasting steel that looks great for longer, but just doesn't stop.

Sure you can cross drill them old things to help but the best thing is to take the old rotor and get the disc drilled off the centre carrier and then replace with some nice cast iron (galvanised) rotors and fit EBC HH sintered pads to the calipers.

You can improve this further with braided lines and a modern classic type master cylinder like the beautiful ones from AP and you'll have the bike standing on its nose in no time.

Now the catch....new cast iron machines rotors are hellishly expensive. These on the attacehd pic are on my 750 build and cost me $350 each! I have the same single rotor on my CB497 Bomber and it stops on a sixpence (or dime if you prefer

Oh come now, a sixpence? The last one I saw was in my Christmas pud!

[crazypj]

One problem I see if newer brakes are adapted to our bikes is you still have a small tire compared to a modered bike.

 That's the main problem, you need better tyres and be prepared to put up with very low life from them.
 Dual disc set up on CB550, stock brakes, 6,000 mile+ on front tyre.
Dual drilled disc, braided lines CB650 master cylinder, less than 4,000 miles on front tyre and it WILL howl to a top or leave 30+ yard black lines (or both when I'm feeling brave, but tyre wear gets down to 2,500ish  )
  For cheaper rotors, particularly if your going to machine them, Harley Davidson use much thinner rotor with a 2" center hole, the Suzuki is around 6.5" to mounting rivets. (couldn't find CB750 rotor to measure off hand)
 They should be available almost new on e-bay as lots of HD owners are more concerned with looks and take off stock parts (I've got a few pairs of HD rotors ready for conversions)
PJ

[flat_black_forever]

Upgrading to newer brake system is your best bet, if you have a machine shop at your disposal, you can change the bolt pattern on a newer set of rotors, mount up a 4 piston brembo caliper, and lock yer front wheel so fast yer on the ground before you even know what happened.

p.s it's only a stoppie if you know it's coming.

[svenD]

ILBIKES,hi
 nice kwacker, what will she do flatout.is she stable at high speed?does the fairing not impair stability?I had a GS 750 in the 70 ies horrible braking in the wet,fine when dry, i think stainless steel has something to do with it but not all,after all sohc hondas arnt nearly as bad in the wet in spite of stainless discs.I have a 77 z650 (single stainless disc) behaves just like the old GS worse luck!

[bert96]

was this a plug and play swap? no need to modify anything? what bike and year do u have?

 My bike is a cb750 k4 and the only mod needed to do this swap is to remove a couple of MM
 on the center of the disc it's almost a plug and play!

You need to modified the brake pad though.

[crustyxpunk]

having an old death trap is part of the fun right?  I would  be inclined to agree about slotting the pads to dispurse water and also a softer compound pad.

[ct_racer]

I understand that your looking for something in emergencies so you want to be able to just squeeze and stop.  Driving technique could also help in a wet situation.  Try just every so often kissing your brakes just to keep them preemptively warmed up and dry.  BMWs (cars) do this automatically when they sense water on the breaks.

[TomC]

Hi Stoppers
     A question: Can anyone tell me model & year of Honda that used a Mater cylinder that looks like the master cylinder used on my CB400F1 and Cb750F1 but is a smaller bore that 14mm?
          TomC in Ohio

[Jerry Rxman Griffin aka MuthaF'er]

Jerry

With all due respect, thinner ID hoses have no effect on hydraulic pressure.
That is a result of master cylinder bore vs caliper piston size.

Wasn't sure. I was thinking along the lines of same MC with same pressure and volume leading into a smaller volume within smaller lines possibly creating higher pressure at the terminal end. 

[754]

Just want to add,
 Drilled rotors, fishead showed a good example, are not always completly covering the swept area, this will cause problems in the wet.

HD rotors usually 5 bolt, so modding to a comstar may work. Also must point out there are 2 common ID, one approx 1.980, the other around 2.10.. could not count how many of these rotors and sprockets I have bored out on my mill..

[HondaMan]

I am not understanding the big differences in brake designs of 35 years ago and today's. Without changing appearance, how can I gain modern "wet" performance from the 35 year old design of the CB750 Honda and GT750 Suzuki?

I have a strong idea it's in the caliper design, but I'd like to hear what you have to say.

1) Dual disc won't do it alone - the GT750 has those from the factory and their "wet" performance is horrible - maybe worse than Honda's single CB750 Four's design.

2) Drilled disc don't solve the problem - a very good friend of mine has paid good money to have his rotors turned-down to 7mm thickness, ground on a flywheel surfacer for a x-hatch surface, and had them drilled - he still has dismal "wet" weather performance.

What can we do to gain-back that precious 2~3 seconds of stopping power when in the wet? Those seconds feel like minutes when a car, fallen tree, or animal is in your path. Those seconds can mean life and death when you're caught in the rain. The back will lock so easily and you simply must have front brakes to stop in a hurry. With stock, vintage brakes, the first few seconds are consumed "drying" the disc. With modern bikes, this is not the case - they grab and work almost instantly. Again, drilled disc are not the missing ingredient - there is something else.

I want to add that every modern bike made in the last 10 years has had fantastic brakes. My Nomad and ZRX are killer - wet or dry. By having reliable braking, you don't have to squeeze hard and even in the wet, I feel I have total control. Sure I do so with care and don't panic, but those fronts really help - standing water included. I need the secret for these old machines.

Thanks in advance.

Gordon

From the day:
1. Drill or slot the rotors, and only slightly bevel the edges of the new features, but smooth them to remove burrs.
2. Install stainless steel, braided brake lines.
3. Try to find some ceramic brake pads, they help a lot.

The modern bikes use more 'leverage' by using a smaller master cylinder piston and longer stroke, which increases the pad pressure. The holes in the disc let the water scrape away from the surfaces, and reduce squeak, to boot!

[RRRToolSolutions]

Hey Mark, Gordon here. Are you saying that adding a late-model resevoir to the existing single or double vintage caliper would make a big difference? The hybrid brakes on my Green H2 are killer, but  I did the whole drilled duals/steel lines/EX500 Ninja calipers and pads all at once, so I don't have any clue which made the biggest impact. I don't buy that earlier tire width issue - this 100/90/19 will slow so fast and so hard, I had to add internal spacing and the strongest Progressive fork springs just to keep the front fender from hitting the exhaust. That old-school tire will generate forces well beyond the stock forks. I'm even sure some deflection is occuring.

It should be easy enough to try this out. There are some rounded modern mastercylinders I could swap-in if it's that easy. This unit came from Parts Unlimited for $149. I'll move it to the Honda and give it a try.

 

[voxonda]

I know, from my own experience, that changing to a modern master can make a huge difference. As a commuterbike I own a 1987 VF1000F2, a big and bulky beast. The original brakes have a lot of problems, especially with the total weight ie. rider and bike. Just swapped the original master for a Brembo 16 mm, and the whole braking behaviour of the bike changed. I even let the pads in to see what a difference it would make.

[SOHC4 Cafe Racer Fan]

I've heard (but haven't seen) that Brembo still makes a period authentic (70's) dual disc system that you can upgrade to.  A friend who is a former Yoshimura GP mechanic has a DOHC bike that has it on the front.

If anyone has any 411 on this, please share.

[ev0lution7]

ya here is the EBC rotor you could paint that center piece black and have a GREAT looking part that apears stock! and is made out of way better material i am putting one on my CB 750

PN: MD1063RS from Dynoman.com

oooops had to edit i forgot to add in the pic

[HondaMan]

Hey Mark, Gordon here. Are you saying that adding a late-model resevoir to the existing single or double vintage caliper would make a big difference? The hybrid brakes on my Green H2 are killer, but  I did the whole drilled duals/steel lines/EX500 Ninja calipers and pads all at once, so I don't have any clue which made the biggest impact. I don't buy that earlier tire width issue - this 100/90/19 will slow so fast and so hard, I had to add internal spacing and the strongest Progressive fork springs just to keep the front fender from hitting the exhaust. That old-school tire will generate forces well beyond the stock forks. I'm even sure some deflection is occuring.

It should be easy enough to try this out. There are some rounded modern mastercylinders I could swap-in if it's that easy. This unit came from Parts Unlimited for $149. I'll move it to the Honda and give it a try.

 

There are several later-model masters out there that were "racing" masters. Basically, they all did the same things: smaller piston with longer stroke geometry on the lever (i.e., more "leverage" and 'feel'), steel braided lines above the fork's right-angle hose joint, and  another piece of braided hose for the lower half. Yosh had one, Rocky Cycle sold a different one, and I saw some in the early 1908s that had no brand, but were just mounted on a peg at the local hi-perf bike shop. They reportedly worked well on the several riders who frequented the place (the old "Motorcycle Parts Center" on Sheridan, for you Denverites...). I saw them on Beemers, CB750, CB500/550 cafe bikes, and at least one KZ1000 that was also cafe'd. It used to be a local mountain rider's hangout, and the owner and manager were good friends of mine, so I got to see lots of cool stuff!    They even sold a dozen different pre-drilled disks to fit most of the popular mountain rider's bikes, all were in stainless steel. At the time, I rode over dual Honda discs myself (wouldn't mind that again), but the wetness problem was real. I used to ride in the rain with one finger draped over the brake lever to keep them warmed and drier when in traffic. That worked OK, just takes concentration. My other 750 friends with drilled discs from Tempo (3/2 patterns) and slotted discs (don't know the builder) reported almost no wet slip, as theirs grabbed right away.

What I wish to do: groove the discs instead of full drilling. I might just have found a disk to do that with...

[voxonda]

I've heard (but haven't seen) that Brembo still makes a period authentic (70's) dual disc system that you can upgrade to.  A friend who is a former Yoshimura GP mechanic has a DOHC bike that has it on the front.

If anyone has any 411 on this, please share.

On my latest projektbuild, a replica of a '73 endurance racer, I use a vintage Brembo 15mm master with the calipers of the K7 and turned down and drilled Honda disks. I make my own pistons for the calipers with a small special trick to enlarge the diametre of the piston. Did that back in the days and still works. But best still is to swap everything for something modern, but I want to stay in touch with the ol'days.
Will shoot some pic's.

[Tim2005]

The single biggest simple improvement I have found is to install some semi-sintered pads, they eliminate the wet weather lag and improve all round performance too. After a few hundred miles things get even better as they scrub away the old polished surface of the disc. Only downside is the brake dust seems harder to clean off the rims...but I can put up with that. 

[Deltarider]

semi-sintered pads

I know sintered brakepads, I know non-sintered brakepads, but what are semi-sintered pads? What brand is that?
I have some EBCpads (FA13) lying around. Are they sintered? Are they kevlar? Is Kevlar the same as ceramic?

[HondaMan]

The single biggest simple improvement I have found is to install some semi-sintered pads, they eliminate the wet weather lag and improve all round performance too. After a few hundred miles things get even better as they scrub away the old polished surface of the disc. Only downside is the brake dust seems harder to clean off the rims...but I can put up with that. 

Yes, those sintered pads were great! They only needed about 1/2 turn of the disc to grab when soaking wet, a fine improvement. They also scrub the glaze from the disc, stopping squeak. I used up 2 sets on mine.
But, I haven't seen them since the early 1990s. 

[Tim2005]

I think FA13s are Kevlar, whereas sintered & semi-sintered are bronze (semi-'s have less bronze, it's mixed with the normal organic material). I don't know if you can buy sintered/semi-sintered anywhere, I couldn't find any so had some sets made up several years back. That wasn't cheap, but was cheaper than changing calipers or discs.

[Ricky_Racer]

Bert96, you said " My bike is a cb750 k4 and the only mod needed to do this swap is to remove a couple of MM on the center of the disc it's almost a plug and play!  You need to modified the brake pad though."

Could you elaborate on how the brake pad (or caliper assembly) needs to modified to fit late floating rotors?  Thanks.  RR

[Terry in Australia]

I've got drilled dual discs, stainless braided lines and an F2 MC on my K1, and they work very well indeed, wet or dry. While I was waiting for the F2 MC rebuild Kit I used a late model Suzuki GSXR1000 MC, and it worked even better, but looked kinda weird on a laid back "Kruiser".

What's the difference between an older MC with a larger than standard piston (i.e., my set up) and a modern MC with a smaller piston, but longer stroke? Cheers, Terry.

[bert96]

Bert96, you said " My bike is a cb750 k4 and the only mod needed to do this swap is to remove a couple of MM on the center of the disc it's almost a plug and play!  You need to modified the brake pad though."

Could you elaborate on how the brake pad (or caliper assembly) needs to modified to fit late floating rotors?  Thanks.  RR

I just cut a little bit of the pad to clear the rivets on the disc,no mod on the calipers.