Radial brakes

[blow_away]

Morning All

Can someone explain this whole radial braking malarky to me? Specifically, why are radially mounted brake calipers and master cylinders better than non radial?

To give the full background, I have so far been happy with the standard brakes on my 1998 CBR600 track bike, especially after fitting the HEL lines. Then I had a go on my mates Aprilia RSV, which has a radial master cylinder, non radial calipers and floating Brembo discs and I was astonished at how much later I could brake, and how much extra feel the braking gave.

Last Friday at Mallory another mate turned up on his 2004 R1, he had upgraded the standard 16mm radial master cylinder to a Brembo 18/19mm cylinder and declared that his braking was much improved, and backed it up with his quickest ever times around Mallory (1:00:03). Being of an impetuous nature I bought his old standard Yam radial master cylinder, thinking that I'd chuck it on my bike and get some improvement. What I am now thinking, on reflection, is that I was too hasty - I will have to source a new brake reservoir, make it all fit and buy new brake lines.

Can anyone tell me if it is worth going to all this effort, or do I just stick the Yam parts on e-bay?

[thefatman]

It should help things a little bit. I stuck one on my vfr and it certainly didn't make them worse.

You can probably just reuse the old lines and bend them round to fit the new master cylinder, if not then you'll need one of these http://cgi.ebay.co.uk/ws/eBayISAPI.dll?Vie...em=160274554464. Project CUNT650 should have a spare reservoir for you if you need one.

[roadracer]

You'd need to see the stock cbr600 master cylinder size before fitting, it's usually written on it somewhere. Radial or normal makes no difference, it's the size of the bore and the leverage that definitely makes a difference. Radial will mean about 4/1000ths more direct input(i.e. fuck all and no-one will notice in a blind test).

You'd want to pinpoint what sort of feel you want from the brakes to decide what size master you want.

[thefatman]

You'd need to see the stock cbr600 master cylinder size before fitting, it's usually written on it somewhere. Radial or normal makes no difference, it's the size of the bore and the leverage that definitely makes a difference. Radial will mean about 4/1000ths more direct input(i.e. fuck all and no-one will notice in a blind test).

You'd want to pinpoint what sort of feel you want from the brakes to decide what size master you want.

CBR's are 14mm, the replacement 16mm. It takes a firmer pull at the lever for the same braking force, so you have to squeeze harder but it feels firmer.

[Muschi]

You'd want to pinpoint what sort of feel you want from the brakes to decide what size master you want.

this is true, as the ratio of the piston surfaces is important.

add the piston surfaces of all caliper pistons, then divide with the

master cylinders piston surface to obtain needed ratio.

one is asked to stay within a ratio from 23:1 ( lowest ) and about 30:1.

stock ducati 1098 is 28 : 1 for instance.

next thing to look after is the lever ratio, the second number you will

find printed on the master cylinder, as your friends 18x19 got a 19

mm lever ratio.

cheers.

[roadracer]

Yebbut what's the leverage axis on both?

Definitely wouldn't hurt to put the R1 master on, if only for the fact that it's newer!

Edit: To answer the original question, radial simply means that it mounts from a radiating point, like a wheel spoke for example. There is no benefit in calipers really, apart from disc size being easier to change without getting the flex of a single-arm mounted caliper when using slicks.

[David W]

The main advantage of a radial master cylinder is that the lever acts directly on the piston, rather than through a linkage so you get better feel from it, which in turn lets you run a bigger piston bore so you can have more power and the feel required to prevent locking up. All in my humble, etc...

Not sure what advantage radial calipers have. I'd love a set of Brembo Monoblocs for my SP2, but arguably for willy-waving blingness than anything else!

The ratio quoted is the distance between the lever pivot and the centre of the piston. A 19x20 m/cyl means the lever pivots 20mm away from the centre of the piston. A 19x18 means it's 18mm away, so a 19x20 lever has less leverage than the 19x18.

[Muschi]

Not sure what advantage radial calipers have.

with radial calipers, it is possible to mount different sizes of discs,

by using spacers to go under the calipers.

as a privateer at home, i found it easier to get them off to change

the wheel too.

[jayRC3045]

Not sure what advantage radial calipers have. I'd love a set of Brembo Monoblocs for my SP2, but arguably for willy-waving blingness than anything else!

unless you go for proper monoblocs (race ones not road ones they put on ducs etc) i dont think you will see an inprovement , the last pre radial set up fitted to SP2/ blades are some of the best brakes fitted to a production bike IMO

[banoffee]

Have a GSXR1000 one on my slabby. Works well and you can pick them up quite cheaply

[banoffee]

oh and hel do a £10 adaptor for your brake lines so you don't have to replace them

[roadracer]

lets you run a bigger piston bore so you can have more power and the feel required to prevent locking up. All in my humble, etc...

Don't mean to kick you in the nuts Dave, but it's quite the opposite- a smaller bore is more powerful. The benefit of a bigger bore is to move more fluid, thus less lever travel. The trouble is, it's physically harder to push a bigger amount of fluid, which is where a stronger leverage is needed.

It's not about more powerful brakes, it's setting the brake lever travel for rider preference. For some reason many riders prefer only a small amount of travel-even myself. I don't know why, you get much less fatigue on a smaller master over race distance but it's the precise feel I like I think. It's important to choose the correct bore/leverage for your/my preferred braking style than for more power, which race pads offer anyway no matter what master you use. [wherethefuckisthethumbsupsmiley?]

[morepower]

OK.....Radial calipers are basically a cheaper way of producing brakes for a wider range of bikes. They all use 2 bolts which hold the calipers onto the fork bottoms usually with a location dowel to keep the calipers in place. The benefits are it is easier to change disc sizes without the need for expensive brackets and just spacers can be used. The bolts do have less shearing forces as the location dowel takes the main load. The flex issue many manufacturers mention are down to the use of this dowel to spread the load over a greater area and if traditional mounted calipers used a dowel for location then they would suffer a similar amount of flex. The biggest benefits would be through the use of a monoblock design like the ones used on the Yamaha R1's and top of the range Ducati's.

Radial master cylinders are more efficient at using the force we put through the lever as the pull is directly on the piston. The lever action is smoother and gives a better feel for the same size piston over the traditional way of operating the piston. There are no other gains over the same piston sizes. But the better feel is enough for most people. The best upgrade regarding a master cylinder is to get the lever so any fade you get under heavy use will still notallow the lever to travel all the way back to the bar. You need the smallest bore which will let you pull the lever as hard as possible but still keep the lever about 10mm away from the bar. When I say pull the lever hard I really do mean hard! If you have that bit of travel in reserve then if you get heat related fade then at least you will still have some more lever travel to try and stop that bit more. Getting this level of set up can mean playing with different ratio levers if you have a Bembo or using an adjustable ratio lever like the AP or ISR levers but once you find the set up you want it does make the bike feel better and you have more confidence in the bike.

The only fade you can do nothing about is where the pads get too hot and they release gasses and the pads push away from the disc. Now this is extreme and only likely to happen on track but this fade can only be cured with a change of pad compound. I have seen this fade with some carbon race pads! making changes to the lever or calipers will not help you need to change either or both the pads and/or discs.

The guy doing a 1.00 .03 lap is not really riding that hard at Mallory as a 1 minute lap is OK for a Novice racer and with a 2004 R1 it should be easy to do this lap time if you pay attention to your riding...But the better feel the guy had may have helped him feel more comfortable and made it easier to do those laps. Adam who started racing in roadstocks last year was lapping in the 57s bracket and found it was as easy to do those laps as it was doing the 1 minute laps a few months earlier. This was down to getting the whole bike set up to work and for him to be confident and comfortable with how the bike works.

[2639]

Morning All

Aft'noon. My 2p in your text.

Can someone explain this whole radial braking malarky to me? Specifically, why are radially mounted brake calipers and master cylinders better than non radial?

I'll have a go. Radial calipers are supported to the fork leg better. That is load is spread through 2 mounts at either end of the caliper. The load split will not be equal, but it is coped with far better than 2 mounts at one end. If something is coping better it could either be made lighter for the same strength, or it could be made more powerful/stronger for the same weight.

Ideally we'd go for lighter option, especially since the caliper is 'unsprung'. If we went 'lighter' we could reduce the steered inertia of the disks by using smaller diameter ones, have less moment over the tyre, but retain the same braking by having better brakes.

Better will also come by having less flex in the body of the caliper. Cos the mounts of the caliper have an easier job the remaining metal could be put in optimum places without worrying about weight too much. 1970's 2 pot calipers expand quite a lot when hard braking is applied. That is the pads squeeze in... the caliper metal moves out. If you have a 50-75 mic it'd be interesting to measure how much.

However all this is a tad theoretical. Riders and fashion tend to bugger things up. Fashion, due to willy size being directly linked to disk diameter, and let no heretic tell you otherwise. 1000 Blades went up 5 or 10 mm in dia after they were first fitted with radial calipers. Riders might be responsible for this subliminally. The vast majority of us cannot reach the limit of quite modest brake set ups. Worse, after coaching in 'safe' environment we still refuse to apply brakes harder. I think Joe Average is then tricked into staying with 50% braking effort and applies it to steadily better braking systems.

To give the full background, I have so far been happy with the standard brakes on my 1998 CBR600 track bike, especially after fitting the HEL lines. Then I had a go on my mates Aprilia RSV, which has a radial master cylinder, non radial calipers and floating Brembo discs and I was astonished at how much later I could brake, and how much extra feel the braking gave.

I like Honda brakes. We agree on what constitutes good feel. But I'd also agree that the Brembo stuff fitted to a lot of Italian stuff is even better for feel. NB: my idea of good feel isn't for many. I assume the CBR is an FX, 300mm twin disk and 4 pot calipers. As std it could easily lift its back wheel over its front several times until it gets too warm. At which point go up a grade of fluid, if the problem persists duct air or fit 'race' pads.

Last Friday at Mallory another mate turned up on his 2004 R1, he had upgraded the standard 16mm radial master cylinder to a Brembo 18/19mm cylinder and declared that his braking was much improved, and backed it up with his quickest ever times around Mallory (1:00:03). Being of an impetuous nature I bought his old standard Yam radial master cylinder, thinking that I'd chuck it on my bike and get some improvement. What I am now thinking, on reflection, is that I was too hasty - I will have to source a new brake reservoir, make it all fit and buy new brake lines.

Some people, me included, just like shiny bits. Nothing really wrong with it. But a lot of lads could take a stock 04 R1 several seconds under a minute lap of Mallory. That said I find my R1 brakes a bit lacking, I'm not conviced it requires a bigger m/cyl to improve it. I am looking to find a 15mm one from some Aprilia's - this is 1mm smaller than stock. It's £160 new via Harris.

Can anyone tell me if it is worth going to all this effort, or do I just stick the Yam parts on e-bay?

There's nowt to lose bar a few quid. But you could try finding definate brtaking marker and practice sqeezing the lever harder, then you could see if this 'squeeze' could be applied faster. You could also try moving the master cylinder inward a bit to gain some leverage.

Reservoirs are easy, any will do. Try Ducati. Thier small pots are cheap, sub £10.

Lastly no one's mentioned the other stuff. Such as wheelbase / c of g / wheelbase / ride height / spring rate / compression damping (oh and rider) will factor with brakes. But tyres are easy to change and see. What tyre and what pressure are you running? If a track orientated tyre is rucking up then things are good - sorry not got a pic to save a 1000 words.

[David W]

Don't mean to kick you in the nuts Dave, but it's quite the opposite- a smaller bore is more powerful. The benefit of a bigger bore is to move more fluid, thus less lever travel. The trouble is, it's physically harder to push a bigger amount of fluid, which is where a stronger leverage is needed.

Yeh, you're right. I was getting it a bit arse about face. What I was trying to say (badly) was that a Radial m/cyl meant you could have the lever acting directly on the piston rather than via a linkage. Improving the feel of the whole thing and giving the improved leverage you mention.

[blow_away]

OK guys, thanks for all the replies, great and in depth as usual!

I am not near the bike so I can't see the m/cyl, so I will have to do the maths later. I had a quick play with Muschi's formula using assumed master cylinder size and it looks good.

The bike is a CBR 600 FW 1998 (steel frame) 2 piston floating caliper. The fluid is new, DOT 4 Rock Oil. The HEL lines were fitted about April this year. I am using blue sintered Nissin pads, which I have always liked the "feel" of. The bike does stoppies no problem.

I think I am going to give it a try, should be able to get it done in time for the PB day at Oulton. I have the old rear brake fluid reservoir which I should be able to use. If I don't like it, I can always go back to standard and sell the bits on.

I'll let you know how I get on.

Big Thanks all

[morepower]

OK guys, thanks for all the replies, great and in depth as usual!

The bike is a CBR 600 FW 1998 (steel frame) 2 piston floating caliper. The fluid is new, DOT 4 Rock Oil. The HEL lines were fitted about April this year. I am using blue sintered Nissin pads, which I have always liked the "feel" of. The bike does stoppies no problem.

I'll let you know how I get on.

Big Thanks all

A 14mm bore should be fine with that set up. Yamaha R1 blue spots use 14mm and the lever is a bit soft with the stock master cylinder but it will be fine with the CBR calipers.

[FazerMonkey]

Edit.......removed.

[blow_away]

I did promise an update...............

Phoned HEL for the brake lines, being the magpie I am I just had to have the stainless steel bleed nipples as well

I decided to leave my existing set up as it is, it can go on the spare bike. Dug out the manky spare calipers, cleaned them up and all looked as good as new. Dry fitted lever and master cylinder, lines, new caliper bolts (see other thread). There is an issue with the top of the brake lever touching the clocks at full right hand lock, I decided to live with it rather than start cutting up the clock surround. All I needed was a brake reservoir, oh look, there's one, fitted to the back brake! One cardboard bracket later and everything is ready to go for real. The reservoir is REALLY close to the fairing but it does not touch. So I make up a stainless bracket, tighten everything up and bleed the brakes with fresh fluid. Lever feels great. Stick bike in van and head to Oulton Park for the PB track day.

At Oulton I see Jon, the guy I got the master cylinder from. "Have you fitted it yet?" I feel a warm glow of pride as I show off my handiwork. "These brakes feel really spongy" says Jon. They were rock solid when I left Bristol, so maybe bouncing around in the van has revealed a hidden air pocket, so I re-bleed the brakes.

After the sighting laps, the lever is really spongy again, bleed them AGAIN but surely that will be the last of the air? Next session, same again

Then the penny drops - the brake reservoir outlet spigot is on the left hand side of the cylinder due to the way it sits when mounted as Mr Nissin designed it to. When a numpty in a shed fits it elsewhere, it lets the air in every time the leans bike to the right! Lesson one - these guys spend millions designing this stuff to be right for a reason

It's too late in the day to swap back to the old setup, especially as Dan is using the bike as well. I warn him to take it steady, which he does with considerably more style than I can muster. The brakes do feel great for the first lap or so...........

Back home, I order a new brake reservior from Morepower. Further updates once fitted.

[rossm]

Have you got a picture to show quite what you mean with the spigot out of the left hand side (I'm having a brain fart) causing air to get in?

[blow_away]

No pics I'm afraid, had to move the bike due to the local thieving scum

Ron Ayers to the rescue

Part 5 on the fiche. In order to make it all line up, I had to turn the pot so the spigot was on the left hand side

[vtr-1000]

OK guys, thanks for all the replies, great and in depth as usual!

I am not near the bike so I can't see the m/cyl, so I will have to do the maths later. I had a quick play with Muschi's formula using assumed master cylinder size and it looks good.

The bike is a CBR 600 FW 1998 (steel frame) 2 piston floating caliper. The fluid is new, DOT 4 Rock Oil. The HEL lines were fitted about April this year. I am using blue sintered Nissin pads, which I have always liked the "feel" of. The bike does stoppies no problem.

I think I am going to give it a try, should be able to get it done in time for the PB day at Oulton. I have the old rear brake fluid reservoir which I should be able to use. If I don't like it, I can always go back to standard and sell the bits on.

I'll let you know how I get on.

Big Thanks all

sell the new master cylinder on gaybay and get a pair of old blade or firestorm nissin four pots(they bolt straight on)re-seal your stanard cbr master cylinder and i think you'll have a very good brake.end of chat!