Street Twin Brakes

Hydraulics is all very similar to a set of levers and leverage ratios.
What is the diameter of the standard master cylinder?

A 2 pot to 3 pot conversion will need more fluid volume movement for the same caliper piston travel.
A smaller master will provide more lever travel and an increased leverage ratio i.e. easier to apply more pressure, but, this may be at the risk of the lever coming to the bars.

HH pads in a standard Nissin 2 pot caliper provide a nice upgrade to OE.

 

So going from a diameter of 11mm to 14mm will push more fluid for the same stroke however, the leverage ratio will have now gone down so more force will be required. This may improve feedback if the current combination is too grabby for example.

It all depends exactly what you're after?

Better brakes is a very ambiguous term and everything is a compromise.

Think the above through and try to describe, as specific as you can, what you want to actually achieve?

 

So is it a straight fit from the older CB1000R abs model?

Here's mine from 7 years or so ago.

 

I'd be really interested to know how you get on with the conversion, as @Eldon has suggested what has changed in lever travel, sense of bite etc..

I've bought the same (along with some EBC FA388 Organic pads) but I've not got round to fitting them yet (garage still too cold).

As @Eldon has said brake feel is subjective, but I find my Street Cup's front brake rather vague and feels like it requires a lot of squeeze to get the retardation I'm looking for, and yet the rear brake is much better, so much so I find myself relying on it to make up for what's not happening up front (often using it more he brakes as standard).

I'm used to front brakes that only require two fingers on the brake and that certainly isn't true of Triumph's standard set up.

 

Do the brake levers now come closer to the grips for the same stopping power as @Eldon has suggested might happen?

And if/when you fit the T595 master cylinder, please could you give a part number for it and show us a picture of the set up at the bars?

 

After reading through this thread am I correct in assuming the front 3-pot calliper from a Honda CB1000R is the same as fitted to the Bonneville Scrambler? Therefore either is a direct fit on the Street Twin (or Street Cup)?
I'm asking because a used CB1000R calliper might be a bit cheaper than a brand new Scrambler calliper imported from Italy.

RevPaul, when you get round to fitting the 3-pot please let me (us) know your opinion. Perhaps you could put on an extra pair of thermals and get in that garage soon, before I forget all about this potential upgrade, which tends to happen at my age

 

T

@beerkat be aware the older CB1000R was offered with two different front brake setups.
Without abs and with.

Without abs - radial calipers were fitted with m10 bolts but I can't remember the manufacturer. Looking at owners viewpoints as I used to be on a Honda forum, these were the inferior option quality wise.

With abs - these are what we are interested in here and were made by Nissin. These were not radially mounted and held by m8 bolts..

On a fairly recent search a nice pair ........were going for £450 secondhand

 

The switch to a 4 pot Brembo front caliper from 2019> on the ST and SS was accompanied by a larger 12.7mm master cylinder. Can't comment on the braking performance of earlier bikes but you can practically stand the thing on it's nose using two fingers with the Brembo setup.

 

I have just got a cb1000r caliper from ebay for my street twin. The piston surface area of a standard 2 piston caliper of a Gen1 Street Twin is 1145.2 Sq/mm. The Honda caliper comes in at 1361.9 Sq/mm. So the Honda caliper is an improvement but, at first glance, not much compared to the Brembo fitted to the Gen2 Street Twin. Although I'm no expert in this field, I can see why the standard master cylinder still works well.

However, I paid £60 for my caliper and it's mounting bracket from a breakers. I also have an ebc floating disc for a Street Cup coming at about £150. I never thought the standard front brake was as bad as some would suggest in the first place so £210 and a bit of brake fluid for a simple brake upgrade seems dirt cheap to me. Should match nicely my full stage1 engine/airbox, decat and straight through V&H performance upgrades. 2820 Hagons with 8.5n/mm front springs compliment.

Thanks for the idea mate, nice one - the brake upgrade was the last thing on the list and I was gagging at the £650 Brembo kit cost.

 

I'm not sure I'm following your reasoning and understanding of engineering, but if you're happy then that's all that matters.

Greater ( presumably your measurements are external) surface area is only one part of the equation, master cylinder volume and the ratio to caliper volume need to be correct to provide adequate leverage WITHOUT excessive travel.

When people use words like " improvement" I usually smile as there is no such thing as a free lunch.

 

Agree. I make the assumption that, for the caliper, larger pistons equals force applied evenly and with potentially more power/friction. I'm no expert on this but my logic is if there wasn't an advantage performance bikes and cars would have 'basic' breaking solutions.

I'm a mechanical engineer and not a hydrolic or brakes expert - far from it! My surface area calculations based on the piston sizes was the only way my amateur mind could compare the 2 calipers in question and start rationalising the choices and try and understand the limits of the standard master cylinder. I'm sure there is an equation that links the hydrolic pressure pushed by the master cylinder, volume of the fluid pushed, size of the pistons, temperature (and maybe other factors) to the 'grab' of a braking system. Feel, as has been said is subjective and a matter for personal taste. For me it is about how quickly I can stop. The feel, well, I'll get used to that.

My major problem is I can't be bothered to do this deep research myself!! So, like most who use forums, I build on the experience of others and try to make sense of it. Anyway, if our friend above says his lever action is adequate that is good enough for me to give it a go. I do have a 14mm Triumph master cylinder in the shed but I suspect/guess it will be a hard pull. Anyway, based on my lack of knowledge it's trial and error! Fortunately I have the time.