Problems with the FFS Hi Spec Rear Calipers ?

[ailwyn]

Things are underway at my end... will let you know when I have any firm info.

If it is just going to be adapting the handbrake cable then I can't see that being a large cost, although I agree an undesirable one. If the worst case scenario is a new set of cables is likely to be around the same price as OEM replacements (~£90).

I don't have any firm information to go on as yet so anything is just speculation.

Ailwyn

[bobbrown]

It has take a little bit of time energy and effort to get to the causes of these problems and I think we have a solution!

I'll start with the problems:
The leak is due to the position of two seals within the caliper, I did some measuring and some drawings to see how it was possible for the seal to leak

Hi Spec seal layout.jpg

As you can see the two seals over lap and this allow the O ring to drop into the groove the other seal occupies this means that the O ring is not sealing correctly. Hi Spec were not aware this problem existed but came about due to slight changes in the design over the years they have been making this caliper and was not picked up.

The hand brake lever and the force required to apply the handbrake is in some part due to the spring on the top as this is quite a stiff spring so not only do you have to apply pressure to the fluid you also have to compress a spring. The spring also has an issue with its travel and I can not be totally sure but may be getting close to if not actually being coil bound when the handbrake is applied.

The seal getting cut is due to the seal getting extruded into the fluid port and then getting a small nick cut in the leading edge when the fluid is pressurised.


The fix

fix.jpg

Hi-Spec are going to be making up some new caliper bodies that will be 3 to 4mm deeper that allow the O ring to be moved back and also some new pistons so that the two seals no longer overlap.
They are so going to look into the spring and the implications but by moving everything 3 to 4 mm it should mean that the position of the spring and or the spring it’s self can be changed such that the force required on the handbrake lever is much reduced.
As far as the seal is getting nipped, I have asked them to chamfer the fluid port such that there is not a sharp edge to it which is more in line with what AP racing do with their handbrake cylinders for race and rally application. This should reduce if not eliminate the problem of applying the handbrake while there is pressure in the system, which I for one could not really get my head around till now having looked at them closely.

They are going to be making 5 initial pairs of modified bodies to prove these modifications work and as I have two pairs here I am going to use those to test them along with Ailwyn’s who has been following my progress that leave two other pairs.
I think a couple of you have reverted to the originals so they will be easy to send and get the modified body sorted.
If you send them to me I will take them all down to Hi Spec and check that all the modifications have been carried and then let them sort them out and return them.
I will supply them with caliper colours of all of them supplied to date so that once these modified calipers are proven the rest can be done.

Bob

[bobbrown]

One other point.

This does still leave people with the option of getting Hi Spec to change the caliper completely for ones with a spot caliper built in or have the original ones supplied modified.
The ones with a built in spot caliper are not designed to stop the car when it is on the move as the pads are small they are only designed to hold the car when stopped so no handbrake turns.

The spot type calipers can be of the same radial design as the ones already supplied but the hand brake cables will not fit and would require some work to make them do so if at all possible which I do not know as I have not seen where the cable comes out in relation to the caliper.
I had to get Hi Spec to make the original ones supplied with the handbrake in a particular orientation this orientation was not in their range at the time so they had to be something of a special.

I personally have never been happy with most of the pseudo (spot) type calipers as they are not really designed to stop the car at any sort of speed, due in the main to the size of the pads and the fact the friction material would be exposed to a lot of heat that has to be dissipated by a relatively small item.

Bob

[ashm]

I seem to recall some cars having outboard discs for the footbrake and inboard drums for the handbrake... now there's a project for you!
Adam

[rip]

I seem to recall some cars having outboard discs for the footbrake and inboard drums for the handbrake... now there's a project for you!
Adam

GM cars too.
My old 1989 Cavalier for instance....

[bobbrown]

I seem to recall some cars having outboard discs for the footbrake and inboard drums for the handbrake... now there's a project for you!
Adam

Looked at that option but there is now way of getting them in as the hub carrier gets in the way!

[Gazza]

Bob

My RED ones are fitted to my car as you know. So what is the plan, how long will i be without rear brakes? Should i wait until it is tested before removing them and giving them to you?

Am i right in saying that the calipers will be completely new or are they just replacing the internals?

Cheers, Gary

[bobbrown]

Bob

My RED ones are fitted to my car as you know. So what is the plan, how long will i be without rear brakes? Should i wait until it is tested before removing them and giving them to you?

Am i right in saying that the calipers will be completely new or are they just replacing the internals?

Cheers, Gary

I would wait for the moment.
Hi spec are going to be re designing the inboard half of the caliper and making it 4mm deeper so that half has to be manufactured along with some of the internal bits. I was told 2 to 3 weeks to get the new bits made as prototypes and then there is the job of getting them the right colours so knowing Hi Spec say 4 weeks.
Once this is completed and proven then they can make the rest (around 25 pairs) and I will give them a list with all the colours on so they can get them made once they are made it should not take them long to turn round a pair of calipers but from the time they leave you to them returning should be 4 to 5 days.
Mind you as you are so close to Hi Spec you could take them off and have them modified while you wait.

Bob

[Gazza]

Bob

So you are saying they will re use the outside of the calliper that you see through the wheel? Only as mine says AP Racing which i would like to keep.

Gazza

[bobbrown]

Bob

So you are saying they will re use the outside of the calliper that you see through the wheel? Only as mine says AP Racing which i would like to keep.

Gazza

Did think that may be useful not sure what Hi Spec will make of it when they go back.

[bobbrown]

An update on the situation.

Hi Spec are having a special tool made to cut the chamfer in the bore for the main seal and are waiting on that arriving they said it should be there this week and they hope to have the first batch done week comencing 22nd.

Bob

[Alan_C]

Hi Bob,

Thanks for the updates. I'm stuck in India for the next 5 weeks or so, hopefully home before Christmas. If the modified caliper parts become available I'll get mine returned to you or Hi-Spec (or whatever system gets worked out) once I'm back in the UK. Mind you, knowing Hi-Spec I'll be home before the new parts are ready anyway.....

[Monty]

An update on the situation.

Hi Spec are having a special tool made to cut the chamfer in the bore for the main seal and are waiting on that arriving they said it should be there this week and they hope to have the first batch done week comencing 22nd.

Bob

Thats good news, does that mean we get new calipers? I`ve got to make sure there for the thinner disk

[Steve A]

Thanks for the update Bob

[bobbrown]

Thats good news, does that mean we get new calipers? I`ve got to make sure there for the thinner disk

The calipers remain the same the only parts that change are the inboard caliper body and the piston, the positioning and the gap for the disc remain the same so what comes off goes back on.

Bob

[Avonvilla]

Any news on this ? Mines starting leaking so it's basically off the road now and it's my main car these days

[bobbrown]

Still waiting on Hi Spec getting the first ones/prototypes done, they should be ready this week BUT it is Hi Spec!
I know they needed to get a new tool made to cut the groove in the bore but that was three + weeks ago.

I will chase them

Bob

[Avonvilla]

Still waiting on Hi Spec getting the first ones/prototypes done, they should be ready this week BUT it is Hi Spec!
I know they needed to get a new tool made to cut the groove in the bore but that was three + weeks ago.

I will chase them

Bob

Thanks.

[bobbrown]

ha!
Spoke to Hi-Spec and they are now saying next week now, so much for the week or two I was first told.
Once these are done and tested then they will be producing a batch ready for changing over on returned calipers.
Note: only send back the calipers and do not include the part I added for the handbrake cable and it may be an idea to mark the pads so you can put them back in the same position.

This list is not a complete list of all the calipers that are out there but will use this as a starting point so they have these colours ready once the testing is complete.

1. Ailwyn (Gold) being done now part of the test group.
2. Ailwyn (Black)
3. Monty (silver)
4. saska (black, 256mm vented, 16"BBS, std H/B cables)
5- Dico (silver, 256mm vented, 16" BBS, Bobs H/B cables)
6. Richard (Red, 256mm vented, 16" BBS, Bobs H/B cables)
7. MPx (Gold, 256mm grooved, 16" BBS, Bobs H/B cables)
8. Gazza (Red, 256mm Drilled, 16" BBS, Bobs H/B Cables) small leak already and not done 1000 miles.
9. Avonvilla (Black, 256mm Grooved, 16" BBS, std H/B cables(i think!))
10. whippit ( red , 256mm vented, 16" BBS, std H/B cables)
11. Paulwatkins (gold)
12. Router (red)
13. Alan C (red)
14. G UK (Gold)
15. alexg (black)

Now there was one other set that Hi Spec have just need to work out who’s they are to many PM's and emails.

[Steve A]

Now there was one other set that Hi Spec have just need to work out who’s they are to many PM's and emails.

Erm would it be my red set