Problems with the FFS Hi Spec Rear Calipers ?

[bobbrown]

Very interesting

I think I know the reason why yours work well.
Yours are adjusted such that the position of the lever gives a good clamp load on the disc and does not need to go up one click which I think would be extremely difficult to achieve if not impossible with out breaking some thing like the lever.
So to some extent it is all in the adjustment of the cables and where the bite point is, as the cable adjustment is not the easiest thing to get to, it's not going to be the best way to sort this out but does prove a point that they work.

Bob

[ailwyn]

I have f.all idea on how the hand brake cables should be set, I've just aimed for them not to be applying pressure on the actuator when the hand brake is off... any slacker would seem to risk the cable disconnecting, any tighter and the brake would start to be on....

Is there/could there be such a thing as an idiots guide to adjusting the cables?

[saska]

You are still missing the point and putting far too much thought in to the length of the lever so I'll give you a clue.

Don't need the condescending attitude nor the (non-existent) clue. I don't need you to tell me braided cables have a stretch component -- any numpty knows that.
You made the current levers (not HiSpec) which have caused so many people to have problems, so I'd suggest you didn't put enough thought into the design of the levers, particularly its length but also the offset angle which is also way off. Now you want people to pay to fix the error. Don't even mind this, as long as it is a well thought out solution that will work well for everyone who has these rear calipers.
It's a great pity you can't be big enough to accept help when it's offered, but that is your choice. You're the one throwing your toys out of the pram because someone dared to question you.
Grow up and get over it.

For those who don't care about the detail -- have a think about this: the stock rear caliper handbrake lever has a radius 58mm long, Bob's Hispec lever is 33mm long. At 57% of the stock length what likelihood do you think there is of matching the clicks on the handbrake lever to obtain a decent handbrake force? If you've got to 'low' then you'd be right.
Match that with the difference between the SE and S2 handbrakes (they move the H/B cable different amounts per click) then you can see how a very few got lucky and a lot didn't. Either way it takes way too much effort.
I did a lot of measuring & research last weekend and I think the math & trig has already told me the correct answer, but I'll do some testing this weekend.
Think I'll keep plowing my own furrow -- anyone else can do as they please.

[ailwyn]

Think I'll keep plowing my own furrow -- anyone else can do as they please.

Does this mean you have a solution that you are willing to share and help out us less fortunate souls, or does it mean you have a solution and everyone else can go f*ck themselves

To be honest I don't give a s**t about who is to blame, I just want a solution... and SE or S2 is not the single failure or success factor, otherwise my car would now be clocking up the miles again.

There was a problem with the original caliper as both of mine were leaking, and in fairness to Bob I think he's quite substantially out of pocket from the hi-spec hijinks if there has been a cock-up on the levers then I don't mind paying a few pound extra to have it put right, from what I understand Bob is a) not in business doing this b) only human in my book that makes a faux pas/error/mistake/oversight or whatever forgivable.... hopefully we can solve this issue sooner rather than later? Then we can all get back on the road!

[saska]

Does this mean you have a solution that you are willing to share and help out us less fortunate souls, or does it mean you have a solution and everyone else can go f*ck themselves :?

It means I'm going to test the math and trig and see if it actually works well. If testing goes well, I'm happy to share the solution with any one.

So think about this:
1.The current lever is 33mm
2. It is angled 28 degrees away from the handbrake cable (lots of wasted effort there)
3. So assume that you'd like to make the handbrake lever 53mm (just for the hell of it)
4. The handbrake cable wouldn't reach that far.
5. now assume that you halved the handbrake lever offset angle to 14 degrees.
6. Lo and behold the cable will now reach the lever.
7. You now have 53mm of radius to play with rather than 33mm
8. Better than that the chord of movement is aligned with the cable, This means you can exert maximum force with minimum effort.

Think the lever needs to be an angled affair as it will have more strength. Also think the cable engagement should be more secure. The current arrangement is anything but.

[bobbrown]

Don't need the condescending attitude nor the (non-existent) clue. I don't need you to tell me braided cables have a stretch component -- any numpty knows that.

And you say I was being condesending! You may also want to revise the "braided cables" because they are not braided they are standard twisted wire construction 19 x 1 if I counted them correctly.

You made the current levers (not HiSpec) which have caused so many people to have problems, so I'd suggest you didn't put enough thought into the design of the levers, particularly its length but also the offset angle which is also way off.

You need to get your facts right before you make that kind of statement, I DID NOT make the levers Hi Spec did my only input on the levers was that it had to be able to accept the nipple end on our cables not the hook for an eye that they would other wise have supplied. It would have been easier if I had as I would not have had to chase Hi Spec when they sent them with the wrong levers and then have to wait for them to be made.
The only part I made up was the outer cable mounting to move the mount for the cable outer to clear the bolt on the top link.

I still feel you are missing something, once the pads have started to bite on to the disc then the caliper levers are not going to move any significant amount no matter what load you apply, if you think they can please feel free to explain how they are supposed to move.
The best position for this to occur is when the cable and lever are at a right angle to each other but there will always be slight variations and compromises have to be made and +/- 15 degrees is not going to have a major impact.
The travel on the cables is 4mm per click on the SE ratchet so once the caliper lever has come to a halt as the pads start to bite, how do you propose you get to the next tooth?
OK I know there will be a slight movement of the lever due to a number or things, caliper flex being one but this will not be any significant amount and certainly not 4mm which would be needed to get to the next tooth on the ratchet.
In the worse case with a 3mm diameter cable (with the current cable construction) to get 4mm of travel you need to input around 200/225kg to the cable and that is about 80/90kg on the lever, do not forget the load is split after the lever so each cable takes half the load that is being applied by the handbrake lever.

[saska]

See diagram below. The hand brake doesn't begin to really bite hard until the last 20% of lever arc.
With a 33mm lever that last 20% is 3.4mm of cable movement. I've measured the SE h/b cable at 4.3mm per click and the S2 at 5mm per click. So a good chance you can't get to a click within that last 20%
With a 53mm lever the last 20% is 5.6mm of cable movement. So you'll be able to get into that last 20% on both SE and S2
With a 66mm lever the last 20% is 7mm -- so you''re at nearly 2 clicks within the last 20% (depending upon where the first click within the last 20% occurs)
A 53mm will take 38% less effort than a 33mm
A 66mm will take 50% less effort than a 33mm (lever is twice the length)

[Alan_C]

It would seem from the previous posts that it is CRITICAL that the handbrake is adjusted correctly in that at full application the handbrake lever just clears a tooth on the ratchet. I think a lot of the issues are due to incorrect adjustment of the cables and compensator link rod, I didn't consider this before, I just removed the slack the same as I would have with the stock calipers. From Avonvilla's post, he has proved that the setup as suppled does work, but I also believe that a longer lever will very much help the situation by applying more force on the caliper lever for the same input force on the handbrake lever. The downside to a longer lever will more handbrake lever travel and even more critial settining up of the adjusters.

Elan M100 handbrake1.jpg

[bobbrown]

Alan beat me to it but this is what I was going to post

saska
So if you have just started to apply the handbrake but not with enough force to hold the car which means the pads have just started to bite on the disc and you are at a point the handbrake lever has arrived at a click how do you propose you get to the next click to apply more load to the caliper?

I did all these measurements in AutoCad and you are not far off but I still feel you are not addressing the fundamental problem which is getting from one ratchet tooth to the next once the brakes have started to be applied, if at this point there is not enough clamp load on the brakes to hold the car.

brake lever longer.jpg

I did look at this from the perspective of having more flexability in the system such that even if you were close to having the brakes fully applied, but not quite enough, you could still get to the next click and then have the brakes fully applied.

The angles and travel are only half the story as Alan is in my opinion correct, the handbrake needs to be fully applied at a ratchet tooth not in between teeth, it is not so critical at which one as any where between 2 and 5 clicks would be acceptable. Longer levers should make this easier to achieve and should give more flexability but is that the total answer?

[RayD]

You need to get your facts right before you make that kind of statement, I DID NOT make the levers

Bob,

I think there are more important things on this web site than getting your facts right.

It would be an easy mistake to think you had them made … or made them.

The fact that HiSpec made them isn’t the reason they are wrong.

While, as you say, it would have been easier if you had made them … you would have made them the same ... or similar … they would still have been wrong.

It wouldn’t have been easy for anyone to have spotted it in advance.

The action of the handbrake is mismatched with the action of the caliper lever and someone might come up with a simple solution to rectify it … Or come up with an observation that leads someone else to come up with the idea … it could be anyone if they were given the chance.

Someone might suggest having an appropriate spring in the line for instance … They might come up with anything.

While I’ve explained to people earlier that they will benefit from any amount of adjustment that will get them nearer to the point where the handbrake click coincides with the max braking effort at the caliper, unfortunately it won’t last due to wear on the pads … so it will still benefit from further work to save continuous adjustment

Ray

[bobbrown]

While, as you say, it would have been easier if you had made them … you would have made them the same ... or similar … they would still have been wrong.

That is all supposition, I can not say if I would have made them the same or not as that is all in the past, my only reason for saying it would have been easier if I had was to save on the time delays while Hi Spec made them.

It wouldn’t have been easy for anyone to have spotted it in advance.

Whilst that is partly true the other issues with the calipers did not make things very easy.

While I’ve explained to people earlier that they will benefit from any amount of adjustment that will get them nearer to the point where the handbrake click coincides with the max braking effort at the caliper, unfortunately it won’t last due to wear on the pads … so it will still benefit from further work to save continuous adjustment.

Wear on the pads will not have any great effect on the position the hand brake engages at as the main caliper pistons move out as the pads wear and the amount of movement should remain much the same, you may get a small amount of variation but not a lot.

[saska]

So if you have just started to apply the handbrake but not with enough force to hold the car which means the pads have just started to bite on the disc and you are at a point the handbrake lever has arrived at a click how do you propose you get to the next click to apply more load to the caliper?

Assume that a particular click gets you to 80-84% of max -- with a 53mm lever you can still get another click at somewhere between 96-100% of max.
Next assume a particular click gets you to 85-95% of max and these don't hold the car -- though my investigations suggested that anything over 90% will hold on a steep incline -- but assume it doesn't hold. You then loosen off the cable just enough to allow you to get to the next click which will be over 95%. If your cables are already slack then taking up a few mm will also get you over 95% but without getting to the next click.
The real point about the longer lever is you don't have to do 'gorilla mode' to get the bugger over 95%

I did all these measurements in AutoCad and you are not far off but I still feel you are not addressing the fundamental problem which is getting from one ratchet tooth to the next once the brakes have started to be applied, if at this point there is not enough clamp load on the brakes to hold the car.

Thanks for the drawing -- it's very close to what I'd calculated -- I just did the rough sketch to simply demonstrate the point.
With regard to the lever design you're spot on with dumping the flat lever with a twist. In the rough sketch I did the other day I did a flat lever with a 90 deg angled block.
The angle will be stronger than flat. The block could be done such that the cable ferrule sits partially within the block meaning it can't come out -- and is less likely to rattle (which mine do). The drawing shows the cable entry into the block as 2 90 deg angles in the channel -- but this is only necessary to prevent the cable escaping the block if the slack in the cable was excessive enough to allow the ferrule end to extend beyond the block. Otherwise a straight vertical cable insert will work.
My only concern about using a longer lever is the deviation of the cable from its central path (33mm)

[bobbrown]

I'm not with you at all.
The first part of the movement may be something around 20 degrees of the motion of the lever under normal operation and will just be lost motion as the slack is taken up and the piston moves past the fluid port.
Once you have taken up this slack and have started to apply load to the lever then the movement on the lever to all intense and purposes stops whether you are at 10% load or 100% load. So if you are trying to work from the full off position to full on position that will not work as it is the last part of the travel that is of interest.
How do you get another 4mm or so of travel on the cable if the load is only at 10% and has engaged with a tooth on the ratchet?
Or on your original sketch you show a full on position, if there is say for the sake of argument a 20kg load on the cable at this point but to get the handbrake fully applied you need to get to a load of 70kg another 50 kg needs to be applied to the cable and are you saying the lever will still move because I would like to know how that is going to be achieved.

I did look at making the lever with an end similar to the original levers but that was getting complicated and required getting the bends just right and ment a left and a right hand version so was looking at a piece welded on the end with a slot to take the cable and a hole to accept the nipple, it can not come out as it is retained by the nipple and would have to have 8mm of slack to get it out if the cup is 8mm long. Or you could just crimp the slot down a bit which will stop the cable coming out.
The twisted lever is more than strong enough and if you care to do the calculations you can confirm this at it does not come close to the yield point at reasonable loads as we are not talking tonnes here but Kg of load. If you could get 100kg at the lever that is still only 250kg on the cable and far more than is required to apply the brakes.

lever end sm.jpg

You can not retain the original outer cable piece if the lever is extended as the angles go all to pot and it's easy enough to move it out, the trick is to have the cable as straight as possible when it exits the outer not introduce an unnecessary angle hence in my previous posts drawing it shows it moved out.

[RayD]

That is all supposition, I can not say if I would have made them the same or not as that is all in the past, my only reason for saying it would have been easier if I had was to save on the time delays while Hi Spec made them.

I understood what you were saying about the delays … and I understand it is clearly supposition … I’m saying you would have made them the same or similar, and that they would still have been wrong.

It wouldn’t have been easy for anyone to have spotted it in advance.

Whilst that is partly true the other issues with the calipers did not make things very easy.

It is entirely true. I was referring to this particular issue.

Wear on the pads will not have any great effect on the position the hand brake engages at as the main caliper pistons move out as the pads wear and the amount of movement should remain much the same, you may get a small amount of variation but not a lot.

At the present time, with the set up, the precise point at which the hand brake clicks are in tune with the caliper movement will be affected by wear on the pads … I know it’s only small Bob … and hopefully if a better solution doesn’t turn up it will be something people can live with. I didn’t mention as a criticism, I was adding it publicly to what I'd said privately about the adjustment.

The main point I was trying to get over was that I think it would be better if more people were encouraged to put their views forward without having them disassembled each time.

Regardless of who’s doing the writing there’ll always be some of it that someone else could see as not entirely correct.

Ray

[RayD]

I wonder if this general idea would work with a spring tuned to the required load ... or would the spring strengh be unavailable at a suitable size?

CIMG8226.JPG

Ray

[bobbrown]

You'll have real problems finding a suitable spring as it need to be of the correct rate kg/mm and the figures required for this are quite high for a small spring.
You are looking for a spring with a rate of something around the 25 kg/mm plus.
Thrown in to that mix how are you going to get a spring on the end with out removing the nipple of are you thinking of one that slips over the nipple with a retainer slotted behind it, me thinks gets clunky even if you could find a spring.
last but not least most springs do not like being taken to 100% deflection unless specifcally designed to do so and are usually square section in that application.

Thus continues the debate with no real resolution, and to think all I said was I was going to make a longer lever prototype to test. If it didn't work then it would have been back to the drawing board and would not have cost anybody any money but that opened this can of worms.

[RayD]

I’m sure you’re right about the chances of finding a suitable spring Bob.

Had it been practical it would have been one of the few things to bring the handbrake and caliper mechanisms together and apply an element of auto adjustment.

With regard to nipple I was thinking a split ring held together with a circlip or something … thinking the cupped type slotted washer wouldn’t be up to the job, as you say.

Does the 100% deflection come into it? … the way I was imagining it it wouldn’t have been fully compressed but still applying the required load onto the caliper lever and taking up the spare movement on the cable.

It’s probably too farfetched.

Ray

[saska]

I'm not with you at all.
The first part of the movement may be something around 20 degrees of the motion of the lever under normal operation and will just be lost motion as the slack is taken up and the piston moves past the fluid port.
Once you have taken up this slack and have started to apply load to the lever then the movement on the lever to all intense and purposes stops whether you are at 10% load or 100% load. So if you are trying to work from the full off position to full on position that will not work as it is the last part of the travel that is of interest.
How do you get another 4mm or so of travel on the cable if the load is only at 10% and has engaged with a tooth on the ratchet?

Ok maybe I'm not being clear -- at end is photo of s2 on a steep incline (fields through fence in front of bonnet are level). The handbrake is engaged 4 clicks which takes a lot of effort. I then jacked up the car, engaged the 4 clicks and measured the lever angle. I then used maul grips to see if the lever would move more. It did but not much and I estimated the handbrake lever (without mauls) was at 95% of its full travel. Moving it the last amount took moderate effort using 8" mauls in an awkward position.
Removed the handbrake cables from the calipers and operated the lever using the maul grips. Then used a long screwdriver in a disk slot to try to move the disk. At 80% on lever you can only just move the disk. At 90% of lever movement it is locked solid. The lever is harder to move above 80% but it isn't much harder to move it over 90% than it is over 80%.
So if you just installed a 53mm lever and did nothing to adjust the cables then there will be a click available that puts you somewhere in the 80-100% of lever movement. Since the 80-100% region is 5.6mm of lever movement then if the click puts you in the low 80s you'll still have another click on the lever (4.3mm on SE, 5mm on S2). That click will put you well over 90%
If, on the other hand, your click put you at say 88% of lever movement then you've not got enough lever movement for another click and the handbrake isn't on hard enough. In this instance you'll have to adjust the cables. Either shorter or longer. so if your cables are already a bit slack then shorten by 2-3mm and the same click puts you well over 90%. If you cables aren't slack then loosen them off by 2-3mm and you'll then get another click which will put you well over 90%.

Or on your original sketch you show a full on position, if there is say for the sake of argument a 20kg load on the cable at this point but to get the handbrake fully applied you need to get to a load of 70kg another 50 kg needs to be applied to the cable and are you saying the lever will still move because I would like to know how that is going to be achieved.

This wasn't my experience using maul grips -- it doesn't take more force to get it there than to hold it there. This view also accords with current experience with present lever -- those who can get a decent handbrake are getting the lever over 90% albeit it takes too much effort.
Will digest the rest of your thoughts on the lever design later -- I've a busy day and it's chucking it down :(

[bobbrown]

Here are my calculations of the forces involved and will probably go straight over the heads of most

The load applied at the handbrake lever to the cables is multiplied by 5 due to the ratio on the lever but is then halved as it is acting on two cables so effectively it is a ratio of 2.5:1
I have only worked the figures for one set up and although the others may be slightly different I do not think the differance will have that much of an impact.

Assuming a reasonable input load is 30kg which should be reasonable to obtain ignoring any mechanical losses and assuming a Pad Coefficient of friction of 0.35 with a 256mm diameter disc

With a 2:1 ratio on the rear caliper and an input load of 30kg the pressure in the caliper is 26 bar which should give something in the order of 83 kgf on the rollers.
With a 2:1 ratio on the rear caliper and an input load of 50kg the pressure in the caliper is 52 bar which should give something in the order of 139 kgf on the rollers.

With a 3:1 ratio on the rear caliper and an input load of 30kg the pressure in the caliper is 39 bar which should give something in the order of 125 kgf on the rollers.
With a 3:1 ratio on the rear caliper and an input load of 50kg the pressure in the caliper is 65 bar which should give something in the order of 207 kgf on the rollers.

With a 4:1 ratio on the rear caliper and an input load of 30kg the pressure in the caliper is 52 bar which should give something in the order of 166 kgf on the rollers.
With a 4:1 ratio on the rear caliper and an input load of 50kg the pressure in the caliper is 86 bar which should give something in the order of 277kgf on the rollers.

It assumes on an MOT the tyres can still grip at the higher loads which is unlikely to be the case and it may well be that slip starts to occur around the 150 kgf mark but is tyre dependant.
The 16% required for the MOT should be around 100 to 110 kgf and 150 kgf should give about 23%


Now although it seems easy to obtain a good handbrake there is a problem getting the lever to be at a ratchet tooth when you are at these loads as once the brakes have started to be applied then the movement on the handbrake lever is limited as the caliper levers will not to all intense and purposes move, they will certainly not move enough to get from one ratchet tooth to the next.
The cables will impart some spring effect but they will not stretch enough to get between teeth,
e.g. assuming a ratio on the caliper levers of 4:1, the load on the handbrake lever is 15 kgf then the force on the rear wheels is 77 kgf which is not enough to get to a reasonable figure you need to input say another 20 kgf this means the cables will stretch something around 1mm not enough to get to the next click. If the input is increased from the 15 kgf to say 50 kgf then the cables will stretch around 1.6 mm, still not enough.

So if the aim is to get to a minimum at the wheel contact patch of around 130 kgf and the maximum is going to be limited by the caliper pressure say 85 Bar which equates to 277 kgf with input loads of between 25 kgf and 50 kgf then there is around 25 kgf to play with.
This gives 1 mm in the cable so it may be possible to adjust the cables with in these limits and I do not think the pad wear will have that much of an effect.
To explain pad wear the main caliper pistons move out as the pads wear and they have a running clearance when the brakes are off.
As a general rule a caliper piston moves about 0.2 mm from off to on, this has to allow for any compression in the pad and any deflection within the caliper such that the pads do not drag when the brakes are released. If the gap is larger than 0.2 mm due to pad wear say 0.25 mm the piston will move out by that amount but only return to a gap of 0.2 mm this is all due to the main piston seals which distort for a small amount of the travel and then allow the piston to move past them and pull the piston back once the pressure is released.
0.05mm in terms of the small caliper piston is 0.4mm and about 1.5 degrees (1.5mm) at the caliper lever, that assumes that the foot brake has not moved the main caliper pistons prior to the application of the hand brake which is unlikely so pad wear could be ignored unless you come to a stop on the handbrake alone.

Back to the problem at hand, the requirement is to get about 2 to 3mm of movement into the cables from input loads of between 30 to 50 kgf.
I have a couple of thoughts on this
1. To allow the lever to flex and act like a spring and will do some test to see if it is possible
2. Add a spring to the system and probably the best place to put it is between the cable outer and the cable outer support. This can be achieved with disc springs and would require the minimal amount of space but some careful calculations need to be done to get the correct spring rate.

The first option is by far the easiest to do, if it is achievable within the stress limits of the material as it needs to move with out exceeding the yield point other wise permanent deformation will occur.
The calculations are quite complex for a flat springs and I’m not sure there is enough length for this to work.
The prototype work should give a better idea just what needs to be done hence the reasons for doing a prototype.

[RayD]

And if you decided to keep it all in one place and incorporate a longer lever with a spring capsule … this might be useful.

Spring holder2.jpg

Ray