TRP RG957 Dual Pivot Brake Lever Compatibility

[CREPELLO]

I'm unable to find a clear indication of which brake controls are designed to go with this calliper. Can anyone advise please? I have come across reference of 2.5 lever ratio, although not on the TRP website.
http://upgradebikes.co.uk/catalogue/pro ... 3d01190e36

Would they be at all compatible with Campag Ultrashift brake levers?

EDIT: I would like to add that there seems a little ambiguity about brake lever/calliper compatibity, so feel free to make this a more general discussion. And if anyone would like to draw up a handy little compatibility chart, the sort of thing that CJ used to make for the old CTC , that would be very helpful indeed

[Valbrona]

Brake pull ratio used to be pretty uniform, only now some newer Shimano levers pull with a slightly different ratio. However, the general consensus is one of 'not worth thinking about'

[Brucey]

Prior to DP brakes becoming the norm, SP brakes used levers with an even shorter cable pull. Such levers are also much the best to use with many types of cantilever brakes. However in shimano STIs, it is pretty simple; all shimano STIs are meant for use with DP brakes. DP brakes fall into two categories (in shimano-speak);

1) Super SLR - all DPs '93-'08, (also some shimano models made subsequent to this)

2) New Super SLR - starting with Dura-Ace in '08

NSSLR cable pull is ~15-20% more than SSLR and the calipers have an increased MA to match the new cable pull. The lower cable tension results in lower friction losses and therefore better braking.

Shimano groupsets with NSSLR include

Dura-Ace...... 7900 (2008)
Ultegra ........6700 (2009)
105 .............5700 (2011)
Tiagra..........4600 (2012)
Sora............3500 (2013)

and (to date) all subsequent variants.

Shimano publish compatibility charts which suggest that some combinations of levers with non-matching calipers are permissible, [but AFAICT only those which give a low system MA] . One can only imagine that the brakes are liable to be a bit wooden with these combinations; it is generally better to stick to matching parts where possible.

A SSLR caliper can usually be identified by examining the geometry of the offset arm (the one with the low pivot). With the brake block set in the middle of the slot, a leverage of 2:1 (in that arm alone) is measured. In other words the distance from the pivot to the cable anchor is double the distance from the pivot to the brake block bolt.

By contrast NSSLR calipers have a higher leverage in the offset arm. In addition to that, there are smaller differences in the geometry of the fulcrum arrangement that shares the force/movement between the two arms. (On the basis of this I'd suggest that TRP RG957 are NSSLR calipers BTW)

A 15-20% variation in caliper MA may not sound like much but it isn't the only thing that affects the system; variations of at least this much can occur if brake blocks are at the top or bottom of the slots in the caliper.

If in doubt (quite likely since specs are not published) you can measure the actual caliper MA; measure the cable pull vs the movement of the brake blocks (in their set position) and divide the former by the latter. SSLR calipers have (with central brake blocks) an MA of ~1.5. By contrast NSSLR calipers have a higher MA than this.

Some combinations that may work 'OK-ish' are;

NSSLR levers with SSLR calipers provided the brake blocks are set in the top of the slots i.e. long drop calipers in a close-clearance frame.

SSLR levers with NSSLR calipers provided the brake blocks are set in the bottom of the slots i.e. the full caliper reach is used e.g. in a frame with decent mudguard clearances.

Combinations that won't work very well include;

NSSLR levers with SSLR calipers if the brake blocks are set in the bottom of the slots

SSLR levers with NSSLR calipers if the brake blocks are set in the top of the slots

The latter results in a powerful but spongy brake. How powerful...? Well, enough that grabbing a handful in a panic can throw you over the bars. [It is very likely that on a long wet descent, you could have the lever coming back to the handlebar, too.]

The former results in a rather wooden brake with low MA. Unfortunately it seems that this is all that shimano can offer at present; BR-650 calipers are the only decent quality long-reach calipers they sell. These are SSLR type and the only reason to buy them is so that you have enough reach, so they are almost inevitably used with the brake blocks near the bottom of the slots. When paired with NSSLR levers, the result can be rather underwhelming.

I think it is very likely that a Tektro or TRP brake of more recent design may offer a better long reach brake caliper / NSSLR combination. I have not measured many but it seemed to me that Tektro 359 model calipers are NSSLR compatible, for example.

If you do end up with a system with a low overall MA (such as is often found with NSSLR levers and BR-650 calipers for example) then some improvement can be obtained by using different brake blocks, eg swissstop ones. Other alternatives that are reputed to give a higher friction coefficient include BBB tristop and clark's gold. [However in some cases the wear rate is higher too.]

I would suggest that if folk can measure the leverage of their offset arms on various calipers (with centrally mounted brake blocks), we can compile a useful list.

For starters

Tektro R536; 2:1

hth

cheers

[edited for typo as kindly pointed out above]

[Farrina]

Brucey,

At the risk of being considered a pedant (and I could in any event be wrong) ... but did you mean Shimano Dura Ace 7900 (as opposed to 9700 in your post typo?). I would not normally have mentioned anything, but am aware that the latest Dura Ace is in the 9000 range so there may scope for some confusion amongst those less knowledgable than you.

Blushingly yours

Alan

[Brucey]

quite so, fat finger (or fat brain cell...) syndrome I expect....

[calls for a Captain Mainwaring-esque " I'm glad you spotted that, Wilson..."... ]

I shall amend accordingly!

cheers

[CREPELLO]

Thanks for your detailed reply Brucey.

In measuring the cable pull and brake movement, can I just check that a measurement of one side should be taken and then doubled up to give the required figure for working out the pull ratio?

The thing that prompted me to bring this up was that the comic featured a review of a Shand Skinnymalinky utilising Campag powershifters (like Ultrashift in brake cable pull) pulling TRP 957's. http://www.shandcycles.com/bikes/skinnymalinky/

Now I know that Shimano Super SLR brakes can be matched to Campag Ergo's, not sure about newer Shimano DP's, but wondered if a specialist bike builder was willing to match these two components, maybe they would work afterall. But I've also seen pictures of them matched to the latest super duper SLR STI's, or whatever they're called.

I need to change my old RX100 long reach DP's. I don't know what's lacking in them. They have good cables, BBB Tri-stop pads and I've oiled the pivots, but they bite like a sick puppy from the Veloce Ultrashifts. Or a bit like middling canti's off STI's, not terrible, but distinctly underwhelming .
Using the same Campag levers with Shimano R650's on another bike, they are much more like a lively pup with a stick, even if they aren't the full grown dog.

[CREPELLO]

Brake pull ratio used to be pretty uniform, only now some newer Shimano levers pull with a slightly different ratio. However, the general consensus is one of 'not worth thinking about'

If there is a consensus, can you direct me to it please? I've come across some forum talk which seems more complimentary. The price is a little steep, but if they are on a par with Dura Ace or Record, then £50 per calliper doesn't seem too bad. The R550's are about £35 each

[Brucey]

In measuring the cable pull and brake movement, can I just check that a measurement of one side should be taken and then doubled up to give the required figure for working out the pull ratio?

the two sides don't move the same amount (yes, the wheel bends... ); it is easiest/best if you measure the cable pull vs the gap between the pads (with the wheel out or the caliper off)

The thing that prompted me to bring this up was that the comic featured a review of a Shand Skinnymalinky utilising Campag powershifters (like Ultrashift in brake cable pull) pulling TRP 957's. http://www.shandcycles.com/bikes/skinnymalinky/

Now I know that Shimano Super SLR brakes can be matched to Campag Ergo's, not sure about newer Shimano DP's, but wondered if a specialist bike builder was willing to match these two components, maybe they would work afterall. But I've also seen pictures of them matched to the latest super duper SLR STI's, or whatever they're called.

I need to change my old RX100 long reach DP's. I don't know what's lacking in them. They have good cables, BBB Tri-stop pads and I've oiled the pivots, but they bite like a sick puppy from the Veloce Ultrashifts. Or a bit like middling canti's off STI's, not terrible, but distinctly underwhelming .
Using the same Campag levers with Shimano R650's on another bike, they are much more like a lively pup with a stick, even if they aren't the full grown dog.

The exact MA of various campag brake levers is unknown to me but IIRC campag ergos don't have a variable MA in the brake lever, wheras nearly all shimano ones do. Thus for 'the same cable pull' Shimano brake levers may pull harder when the brake is on.

That small bike manufacturers play fast and loose with brake MA combinations doesn't surprise me; it isn't as if any of the component manufacturers are willing to make any recommendations regarding pairing of their parts with those of other manufacturers, even if they know perfectly well that there is no good 'one maker' solution for some bikes.

The thing that makes or breaks some of these combinations (including your RX100 vs BR-R650 conundrum) is -as well as unknown variations in cable condition/quality- very often where the brake blocks sit in the slots; quite small differences here can make a very large difference to the system MA.

cheers

[CREPELLO]

Sorry Brucey, I posted a longer reply, but it was lost in the ether. Anyway, I'll just add this picture I found on the web that might be informative...or not. New Ultegra SSLR compared to old SLR Tiagra (I think) Distinct difference in length of actuation arms.

Is the arm length informative as to how well any given DP calliper is going to perform with a certain brake lever?

I haven't found a good front on view of the TRP 957, but my impression from various views is that the actuation arm is longer and not shorter, therefore might work well with Campag levers...

[ChrisButch]

For what it's worth, I've been using these calipers for a year or so now with Shimano pre-STI Aero levers, with excellent results.

[Brucey]

New Ultegra SSLR compared to old SLR Tiagra .... but my impression from various views is that the actuation arm is longer and not shorter, therefore might work well with Campag levers...

NSSLR calipers typically have a longer offset arm (pinch bolt to pivot) and a shorter distance from pivot to brake block. Divide the former by the latter and you should get around 2.5:1 for NSSLR (vs ~2.0:1 for SSLR)

The way these brakes work it usually ends up that the non-offset arm has an MA of about 1:1 and the offset arm has an MA of either ~2:1 (SSLR) or ~2.5:1 (NSSLR). The overall caliper MA is (roughly) an average of the two arms, thus about 1.5:1 or ~1.75:1 respectively.

These figures are about right [u]when the brake blocks are in the middle of the slots[/I] but if they are not then the caliper MA can go up or down significantly.

Note that 'SLR' was first used to describe the arrangement of biasing springs used in the final generations of SP brakes. All DP calipers (to 2008) have used Super SLR (S-SLR or SSLR) and the latest ones use 'New Super SLR' (NSSLR).

However even Shimano are not consistent about how they use these terms. On the same page I have seen mention of both 'super SLR and New Super SLR' when really only the latter should apply, so it is easy to get confused.

For what it's worth, I've been using these calipers for a year or so now with Shimano pre-STI Aero levers, with excellent results.

such levers could well be SSLR lever pull (which model are they? IIRC only one or two models of shimano Aero lever were ever plain 'SLR' rather than 'SSLR') and if so they can give a good brake with NSSLR calipers provided the brake blocks are in the lower half of the slots.

cheers

[CREPELLO]

I've got to admit Brucey, all those figures...my head hurts a little bit. But I see there is also another thread viewtopic.php?f=5&t=104490&start=30 that is also causing considerable reflection on what exactly is going on with this whole brake pull leverage subject. Which can only be a good thing. We haven't discussed this matter nearly enough IMO (although I'd rather it wasn't me that was discussing it in such detail ).

I do want to point out (I will regret this ...)

NSSLR calipers typically have a longer offset arm (pinch bolt to pivot) and a shorter distance from pivot to brake block

Really? So the picture I included above distinctly shows a shorter 'offest arm' (what I'm calling an actuation arm) on the newer 6800 calliper than the older 4500 calliper
Not saying you're wrong, but I'm still confused..

[CREPELLO]

At this point, nice big pictures may help...or is it just me (and Mick F ) ?

[CREPELLO]

For what it's worth, I've been using these calipers for a year or so now with Shimano pre-STI Aero levers, with excellent results.

Thanks Chris - very useful to know. Weren't Shimano most aero levers spec'd SLR? In which case, if the TRP 957's work with those and Shand Cycles spec them, perhaps they are alright with old spec brake levers after all?

[Brucey]

...I do want to point out (I will regret this ...)

NSSLR calipers typically have a longer offset arm (pinch bolt to pivot) and a shorter distance from pivot to brake block

Really? So the picture I included above distinctly shows a shorter 'offest arm' (what I'm calling an actuation arm) on the newer 6800 calliper than the older 4500 calliper
Not saying you're wrong, but I'm still confused..

ah, my comment was in reference to something that looks like a DP caliper, but slightly different. The 6800 caliper is a different wee beastie; they call it a 'Symmetric Dual Pivot' but really it would be better named a 'Twin Pivot'; the offset arm has a similar MA to a conventional DP caliper but instead of the other arm pivoting about the centrebolt, it rotates about a second pivot which is a mirror image position of the one for the offset arm. This in reality makes it a more honest copy of the old Altenburger 'synchron' brake, and even more like a centre-pull than a conventional DP brake, just with a different actuation mechanism.

The gives the second arm a higher MA (about 1.5:1 I think) which means that taken with the offset arm's MA of ~2.0:1 the average MA is around 1.75:1 or something for the caliper as a whole. In point of fact the one in your picture has the brake blocks at the bottom of the slots, so its MA is somewhat less than it could be, on a really close-clearance frame. I have seen a lot of bikes with these brakes where they didn't use the brake 'properly' (but did allow a little more clearance for tyres etc). [This might help explain Pete's comment in the other thread about his 6800 brakes being slightly less good than the campag DP ones..]

cheers