Front brake Modification

I thought I saw a topic a while back about where someone mentioned drilling out the hole on the little black valve in a master cylinder? Can anyone verify that? Thanks.



Tim_S

Check Hobots posts.

hobot here, yes I took essentially all restriction out of the rubber booty 'valve'
and got nice improvement in other wise bone stock front disc. I was pensive I'd created some lurking danger but relieved to realize that All the sleeve kits completely remove this rubber valve/restrictor.

Its pretty tough rubber and drilling don't do much but rough up tiny hole, so restored to cherry red hot nail at least 1/16" dia and cleaned up hole more after that. Main reason I can see to retain the booty is as factory piston return spring tension spacer.

Seemed to give more one-one effect at pads from lever grip and definitely made it easier to lock up below 40 mph and squeal w/o lock up at hwy speeds.
Just guessing going by lore and scuttle butt that it was a way to have modern looking/selling disc but still about same performance as dang ole drum.

SS braid hose and RGM race lever and lightened disc add extra goodness to otherwise bone stock brake. But none of that for otherwise plain jane Trixie'72.

Thanks Hobot, I'll give it a try later this evening when I replace the seals. I'll have a report in a day or two.


Tim_S

Hobot......... I tried your suggestion and enlarged the tiny hole to about 1/16 or so. My lever has a bit more travel now. Not quite halfway back the the grip? A softer feel too. I compared the travel to the brembo master on my other bike and modification is a little softer feel. As it was raining most of the afternoon here today I couldn't try it out.
Soooo .... you all are my witness that if you don't hear from me again you'll know what happened :shock: ha ha
Testing begins next week ... :mrgreen:


Tim_S

hobot said:

hobot here, yes I took essentially all restriction out of the rubber booty 'valve'
and got nice improvement in other wise bone stock front disc. I was pensive I'd created some lurking danger but relieved to realize that All the sleeve kits completely remove this rubber valve/restrictor.

Its pretty tough rubber and drilling don't do much but rough up tiny hole, so restored to cherry red hot nail at least 1/16" dia and cleaned up hole more after that. Main reason I can see to retain the booty is as factory piston return spring tension spacer.

Seemed to give more one-one effect at pads from lever grip and definitely made it easier to lock up below 40 mph and squeal w/o lock up at hwy speeds.
Just guessing going by lore and scuttle butt that it was a way to have modern looking/selling disc but still about same performance as dang ole drum.

SS braid hose and RGM race lever and lightened disc add extra goodness to otherwise bone stock brake. But none of that for otherwise plain jane Trixie'72.

Click to expand...

What is the RGM race brake lever like? I have a sleeved master cylinder, but a Norvil race caliper. I have more lever travel, but not as much as I would with a stock caliper. Does the race brake lever bring the lever closer to the handlebar? Do you have a picture of it? I tried a MkIII brake lever, but it's much too close to the handlebar.

-Eric

I have the RGM race lever with Locheed racing caliper and stainless braided line and Dot5 fluid, the racing lever brings the lever back at rest and increases leverage but it does not touch the hand grip when applied strongly. I could do more mods but if the Norton gets too good a brake I will have problems going back to the drums on the Bsa's and Triumph. As it is I can get the tyre making noises easily.

Tim-S, best wishes on surviving our dangerous hobby horses. Yet rain slick or dry loose stuff is one of the best reasons I now have so little respect for super duper modern brakes or fat tires. Mysterious-revealing report that you got more factory lever travel w/o changing factory master cylinder to caliper size/hydraulic ratio's.
Even more intriguing you found it similar to moderately sleeved down m/c, yet so did I though, mysteriously un-revealing on 12 mm m/c bore, hmm.

Deadly seriously I find the spiffed up Norton disc-19"tire better in all conditions than moderns I've tried, including the tiny ones on off road bikes that suck on tarmac.

Deadly seriously I find basic spiffed up Lockheed to give normal scared-surprised human pilot ABS like 'security' from over the ton to 55 mph, then lock up ease with ABS forgiveness effort - mid 50's > 0, on great traction steeps/sweepers or wet grass to electrostatically repelling loose, nil friction grit, with tail light about mid back level. [** I NEVER trail brake if leaned nor HARD brake if forks turned ANY bit ] THE Gravel teaches All - only brake like racers if not going very fast so hardly need to brake anyway and could actually steer sharper just then ]

Absolute immediate danger no matter what speed encountering is Mud, especially if leaf covered. Never ever expect to cross that stuff, even with feet in it, EVER! Go instantly into emergency crisis freak out state as no way to slow to matter in time - best to speed way up and ski it while just matching power to keep rear turning a mere-ish tad faster than rear dragging a mere-ish tad from actual 'surface' speed.

RGM lever is a bit longer but also recurved. It allows fingers further from pivot point, so more leverage with more travel per pad pressure, so softer more forgiving pilot effort to match grip desired. Also seemed to go closer to grip for more hand muscle leverage of full fisted tire-bike slowing. To get similar safety effort range on my SV650 I cut 2" off levers, but mainly for less often breaking off, but still dicey too easy lock up in surprises or slick conditions. RGM lever may also have better pivot point provided too.

I don't ride much to ever need brakes, knowing they are bikes' main down fall and about only reason bikes can't beat cars in turning races. So hobot goes rather slower than most into blinds and weird stuff but WTF faster than most, beyond any brake effect other than trip downs, fling ups or skewing on CoG. Only the ABS like Norton set up allows my state of emotions to match my grip effort for desired brake effects, about thoughlessly now. But I do have a forced into Programed In - Innate Reaction to grabbing brake in crisis,
***RED HOT BURNING ROD*** to let go of and steer wilder instead.

But I don't always have choice, black bulls, Bull Elk, dropped trailers to tree falls across path in down hill sharp turns, after dark on wet leaves. Best braking I think i ever did was coming off straight Gravel steep at night, no lights showing around the 100' bend so went in a bit faster than normal crisis state, to see dark blue no grill of a Chevy pu dead in middle of 10 foot wide path, with both doors wide open, and a fella standing behind each door, so no way around or even slamming into doors w/o serious injury, I hit both brakes enduring the ***SHEARING FIRE*** reflex keeping both tires barely making noise, no sliding - going absolutely straight, just missing grill to end up at passenger door face to face with a fella through open widow, holding his ding dong as my head light relfected backwards into clouds of dust flowing by us for added surreal air to it all.

Here's the spot in late daylight.


T140 tall bars, for ape hanger cruise ease that fooled the squids until I got head down between em. I dare ya to follow me home on ya chin close clip ons and over grabby momentum ladden dual discs.















Most may test their riding capactiy that day by speeding aroud to warm tires, not me I test braking to see how easy I wet my pants before flying over bars.
I expect Ms Peel to stop shorter than about any other bike as well as out turn em.
Objective measures someday.

Hobot...... Try some Decaf. Without sugar !

When eye put the brembo master on my MK3 I was using a Lockheed racing caliper from cafe racer. Stock disc, good pads and a stainless line and chrome remover from disc. The brembo wouldn't pump up no matter what I did. After a half quart of fluid I tried the stock caliper again and in two minutes I had a brake. I wasn't pushing enough fluid to that big caliper to make it work. It works just right now 8) .


Tim_S

Hey TIm, pictures please and steve that picture looks exactly like the roads I ride on regularly.

brithbike220 best wishes riding THE Gravel, all's well right up to when it ain't.
I've not crashed on THE Gravel paths in a couple of years, not counting goats, but I have crashed twice this year on pavement on a few yards hidden Grit while using a drum brake on '71 and my SV pulling up short in a friends drive way. You seem crazier than me so will let you lead the way if we take off together someday.

Well, I tried the hole enlargement mod and the brakes still work :lol: so after a couple hundred miles I've lived to tell you. I do have a little more travel in the lever now. It doesn't feel as "woody" or hard like they normally do. I like the new feeling better. Let's see how it holds up in the long term now...

No gravel roads just yet for me cuz the paint is still fresh on my tank ..


Tim_S

Tim_S said:

Hobot...... Try some Decaf. Without sugar !

When eye put the brembo master on my MK3 I was using a Lockheed racing caliper from cafe racer. Stock disc, good pads and a stainless line and chrome remover from disc. The brembo wouldn't pump up no matter what I did. After a half quart of fluid I tried the stock caliper again and in two minutes I had a brake. I wasn't pushing enough fluid to that big caliper to make it work. It works just right now 8) .


Tim_S

Click to expand...

It really doesn't matter, Brembo, Lockheed, whatever. If the master cylinder and caliper(s) are not sized correctly, you will not have optimum braking. Choosing the correct size of components is more important than the brand of components.

Has anyone done that mod and tried the brake in direct comparison to the CNW Brembo mastercylinder ? I had a sleeved oem MC but I still didn't think it was that great so I replaced the oem MC with the Brembo. The Brembo (with/ss brake lines/Ferodo pads/rebuilt the caliper) brought the bike to current stopping ability levels - limts are based on the tires. Feels pretty much like my Ducati 996 did (though without the tire stickiness up front) - excellent.

BUT...if this mod being discussed can make the oem MC do that, I would put it back on just to have the oem switchgear, etc. Or does a sleeved oem MC already have had that restriction removed as part of the sleeving process? If so, IMO there is no comparison between the sleeved oem and the Brembo.



"I was pensive" - Nice use of a cool word! You don't see/hear it much!

Ms Peel best brake so far was sleeved Lockheed m/c, SS hose, RGM lever and l.5 lb lighter factory rotor. I liked it better than the one finger moderns I've tried and stoppied on - mostly by accidental surprise that ended up extending stopping distance d/t back off not to fall down forward, but was fun at gas stations to lift tail and drop back on last pull down from 3-4 mph, where opened rubber restrictor Trixie even, would just stop shorter about throwing me over bars.

Only 110 size tire traction was Peel's limiting factor and way way more easy to control that in bad conditions surprises. Peel could lock tire on panic grips over 100 mph, I never had to do that as picked places wisely but sure did practice it and get to use that fear-skill going 90 or so seeing a vehicle approaching to enter across my path a 100 yds ahead so slam down till 40's mph, too often to have the car either scratch out delaying its expected time across my lane or they just don't care and pull out slow anyway, but I'm able to finish a complete short stop or slowed enough can dodge around them even going off edge. Racing is childs play compared to what I get to deal with just trying to get somewhere safe as can. I get scared a whole bunch all the time, so much so, just pushing limits in nice spots is relaxing thrilling, not terrorizing. I never scare myself racing around,
I know better than that and so should you all.

i became rather pensive hoping on my SV650 after a flat on way back on Peel, as had to watch out for surprise stoppies on SV going by Peel's normal sense of slow down for blinds i innately do each/every time religiously unless not in a state of mind fearing damnation in ever lasting hell from a truck grill or tree fall impact. I know I can stop better on Ms Peel than anything else but maybe them new scooters with both brakes tied in by computerized ABS. Sports bikes are so forward biaised mass to tame their only advantage, straight line sprints, they have shot themselves in foot by too easy stoppies on too powerful brakes on similar front tire patch size as all the rest of us.

Someday I'll get 0>100>0 data to really compare for others to know what I already do in spades. BTW the best braking by far is done straight upright, or SPLAT!
If you still think like mis led moderns to apply brake while leaned, LOL, fine if going so slow as racers into turns on too rigid moderns or too flexy un linked old isolastics. I know better the hard way. Best use of brake in turns is usually the rear weak one, to get rear swung out when going slow as supermotard racers or to snatch a hi side save up of a low side down corner when going a bit faster than modern racers and hitting grit just then. Brakes in those condition have no speed change effect to matter. All's I can say is if you need brakes while still leaned you are going too fast into the turn to begin with and risking all for such little to gain. Fun in turns is to speed up in them not slow down, sheeze.

MexM, the sleeved mc doesn't have the mod. Your using whatever new seal kit is required for it. The new downsized bore is what gives you the new 'feel'. Both my bikes have a SS line and good brake pads. But only my MK III bike has a Brembo 13 mm mc. Now both my bikes have the same, feel,,,, so to speak.

Tim_S

http://www.vintagebrake.com/mastercylinder.htm



Here are somi interesting ratios
we used them when building specials mixing car components and bike bits on our outfits
Seems to work

From reading the many brake posts (other threads), I get the impression that some think if they change to a Brembo or other top line brake components they will improve braking. Not necessarily so. If the ratio of caliper to master cylinder is not correct you may end up with a poorer performing disc brake than you started with. If you are contemplating upgrading the front disc brake, give Mike Morse at Vintage Brake a call.

I have a 11mm Gremica master with a Gremica copy of a Lockheed 2P racing caliper, SS brake line and 12" floating rotor. This gives me a ratio of ~27:1, caliper to master. I'll put that brake up against most any other I've ridden.