Improving performance of Hunter brakes?

[gouldsborough7]

Re: Improving performance of Hunter brakes?

Chris
The MOT guy identified that the nearside lower ball-joint was totally naff, and I ended up with a new wishbone with new rubber roll-bar bush and ball-joint. The offside passed the inspection OK. At the same time he adjusted the tracking I think to 0-2mm toe-out Sierra settings.

Peter
Tyre pressures appear to be a variable subject. Marlin quoted to me 18psi (which I used on my previous Berlinetta), the owner owner appeared to be working on 25psi, and a member quoted 22psi. So I have been using 22 psi all around as a reasonable compromise. For no particular reason, I have also changed the wheels/tyres around so that the best treads are on the front axle.

The discs look like new, and show no sign of running out-of-true or whatever when I spin the hubs. I cleaned up both discs thoroughly using cellulose thinners, to get rid every trace contamination, oil or whatever. Amazing the black gunge left on the rag! Still made no difference to performance!

Cheers
Mike

[lizbillings]

Re: Improving performance of Hunter brakes?

Hi Mike. When I got my Berlinetta it was on really old tyres which had stood for ages. Made a big difference braking with new ones and wheel balancing etc. regards Liz

[gouldsborough7]

Re: Improving performance of Hunter brakes?

Hi Liz
I agree with your thoughts, but when I apply the brakes on a dry surface the steering wheel will rotate very slightly to the left if not gripped firmly. It's not enough to present any danger, just something that shouldn't happen. Haven't tried it in the wet. Might do next time it rains.

Years ago, I drove any old Renault 10 which decided to pull really violently to the left (even without braking). I found out that the nearside front calliper had become virtually siezed up, so the solution was easy!

If the front discs were as easy to swap over as the rear drums, I would try this as an experiment. Then the car should tend to move to the right, and prove the point. Think I would need an extractor to yank them off.

Can anybody advise me on removing discs?

I'm come around to the way of thinking that perhaps there is some geometry problem. Perhaps the garage got the toe-out wrong - I will double-check this, as I have some kit that will measure this. It's only a simple telescopic device, but it might show up something.

Cheers
Mike

[greyV8pete]

Re: Improving performance of Hunter brakes?

Hi Mike.
I have always found the following to hold true. If the pull to the right / left is noticable when braking sharply look to the front brakes. If discs then often one side has air in and needs bleeding. If the pull to the right / left is more progressive and at speed it pulls more to one side the harder you press the pedal, then look to the rears. If rear drums then this is often due to uneven bedding in of new linings or rear oil seal leaking oil onto the linings as worst case scenario.

I have had a front caliper sieze on both my old Sierra and on my Hunter (same braking system) and amazingly in neither case was any pulling to one side a symptom. The Sierra siezure was only found during an MOT as the wheel couldn't be turnd by hand and the Hunter was evident by a strong smell of hot pads and lots of smoke when I stopped, about 3 miles after leaving home. Hope this helps. Peter.

[gouldsborough7]

Re: Improving performance of Hunter brakes?

Hi Peter
The pulling to the left is still identifiable whether braking lightly or with a vengeance. The left pull is now quite minor, and I can live with it if not cured. However, I like things to work just right, so perseverance is still 100%.

To summarise I did the following : 1) replaced both front callipers & pads, 2) replaced both rear slave cylinders (originals looked old but had not leaked, but thought SODS Law would make them leak in a few weeks!), 3) did not replace rear linings as they looked in good order, but gave them & drum interiors a good clean up with solvent, 4)thoroughly drained out old fluid and bled air out meticulously from new fluid using valved-tubing on bleed nipples.

I think the above work made some improvement, but did not eliminate the left pull entirely. Did wonder if the flexible pipes could be a factor in some way, but they are all braided and in good external order.

Got to be the joys of running a kit, albeit assembled by Marlin! Perhaps I should seek out a company to do a full geometry check, if such a service is readily available. Could it be that the chassis is crabbing in some way?

Cheers
Mike

[greyV8pete]

Re: Improving performance of Hunter brakes?

Hi Mike. As you say the joys of running a kit car!
I have never had any success with valved bleed tubes as air just sucks back around the threads and into the hydraulic line when you release the brake pedal. I have heard that wrapping a small amount of PTFE tape (like the plumbers use) around the nipple threads can stop this but have never tried it. I always use an "assistant" these days, so I can nip the thing shut while the pedal is still down. I have tried the Gunsons Easi Bleed but you only get a trickle of fluid which doesn't purge all the nooks and crannies in the cylinders. The only really good one man bleed system that I have ever used was called Automatic Bleed Valves. Bit like a tyre valve but in the bleed nipples which were replacement units for the O/E ones. Unfortunately they are no longer made. Persevere with the bleeding a bit more with an assistant, as I am sure that therin lies your problem. Don't forget to brief them about holding the pedal down until you shout "UP" or you will suck more air in and things will get worse! Peter.

[gouldsborough7]

Re: Improving performance of Hunter brakes?

Hi Peter
My trick is to raise the jam-jar collecting the expelled brake-fluid higher than the bleed-nipple, so that the bottom of the jar (and hence the outlet of the pipe/valve between nipple & jar) is about 3 inches minimum above the nipple. I have a large block of wood which serves the purpose of holding the jar at this required height. So the nipple thread is always surcharged with fluid instead of air. A ring spanner is attached to the flats of the nipple throughout the procedure. When the tube (it's transparent) is without bubbles, I tighten up the nipple.

My valve/tube is part of a 4-pipe kit I bought some years ago, which was designed to allow all 4 nipples to be bled simultaneously. I prefer to do each one singly, and go around the car twice. On this occasion, I consumed the best part of 2 pints of new fluid, before I was satisfied that all air bubbles had been expelled.

The brake pedal goes down to a solid stop, whereas I believe if air was trapped in the brake pipes, the pedal would feel spongy.

Thanks for your interest

Cheers
Mike

[chris_cussen]

Re: Improving performance of Hunter brakes?

Mike
I'd still go for changing the discs. Its a relatively easy job.

1. Loosen the wheel nuts,
2. Jack up the car, and support on axle stands
3. Remove wheel
4. undo the two bolts (17mm I think) that hold the caliper to the hub (they are at the back). Be careful not to round the bolt heads as they might be tight. I use a socket with an extension bar to get the leverage required.
5. Slide the caliper off and suspend so that the flexi hose is not strained.
6. If there is a x-head screw visible undo it. It may round, if it does drill the head off, in my experince you don't need it anyway.
7. Pull the disc off the wheel studs. If it sticks persuade it with a few taps from a hammer from behind, rotating it 90 deg after a few bangs.
8. de-grease the new discs
9. Re-assemble in reverse order (to quote Haynes et al)
10. Don't forget to tighten the wheel nuts!

[gouldsborough7]

Re: Improving performance of Hunter brakes?

Thanks Chris
No problem with removing callipers etc as I have done it several times already, with copper grease in the right places on re-assembly. I was unsure about the way the discs were held on the car. So once the x-head screws are removed (assuming it has them), I am pleased that the discs come off much like the rear drums - probably assisted by my big rubber hammer! Didn't want to start mucking about with bearings.

My initial plan is to swap the discs over - left-right & right-left, which would at least confirm once and for all whether the pulling-to-the-left was a function of the discs or something else. Operating on opposite wheels, if there is a disc problem, the pulling-to-the-left should then go to the right. Having already done most of the dismantling/reassembly already, it shouldn't take much more that 1 hour to do the swap.

On safety grounds, I was willing to finance the new callipers, pads, fluid and slave cylinders (about £95 total). However, I drew the line at new discs if there was a likelihood of finding that no improvement was obtained. Don't know what they might cost, but are bound to be twice the first number I thought of!

Will provide progress report.
Cheers
Mike

[chris_cussen]

Re: Improving performance of Hunter brakes?

I think you'll find they are quite cheap if you go to a decent motor factor. I had to replace discs and pads on my Ford Puma earlier this year and the total bill for both lost was less than £60

Good luck with your experiment.

[b_caswell]

Re: Improving performance of Hunter brakes?

Try deglazing the discs with emery cloth then
I would swap the disc over. Its possible they are not a pair. Friction value of the steel disc can vari. Another point could be the flexible hose may be swelling? or sometimes the inner lining of the hose can collapse and restrict the flow through the hose,

[greyV8pete]

Re: Improving performance of Hunter brakes?

Mike. Just had another thought. If you have the Teves type calipers have you checked the two guide pins on the carrier plates that carry the caliper assembly and allow it to float / centralise on both sides? I had poor braking after an upgrade and found that these were dry and binding (bit like a siezed piston in fact). Prise the dust covers out of the ends with a blunt screwdriver and use a 7mm allen key to remove them. (Special 7mm allen keys with a good long handle are available from motor factors). I used silicone grease on the pins and in the bores that they run in. Result, very much better and even braking and the new pads and discs have bedded in quite quickly and evenly. Peter.

[gouldsborough7]

Re: Improving performance of Hunter brakes?

Thanks guys for your ideas.
I had thought about deglazing the discs, and had in mind rigging up a large socket in an electric drill, and rotating the discs at slowish speed with a piece of fine emery paper rubbing each side for say half a minute.

Might try that first, and then if that does not effect any improvement move on to swapping the discs over, just to see if the pulling problem changes to the right.

I have been using a copper-based grease on the guide pins, and anything else that needs to slip, like the metal edges of the brake pads, where they contact the callipers. This grease is good, and sticks to the metal parts, wheel nuts or whatever almost indefinitely. I'll make sure that any reassembly will get another smear in the right places.

Will let you know how things go.
Cheers
Mike

[greyV8pete]

Re: Improving performance of Hunter brakes?

Much easier just to rub the discs lightly by hand using a circular motion, off the axle is easiest, ( like you are polishing the car) so you get some "circular scratches" across the disc. Your method will just put "scratches" around the disc which is not very effective for glaze busting. The circular "scratches" soon wear out but speed up bedding in of the pads. I use 60 grit emery otherwise if too fine you end up just polishing the disc not deglazing it.

Another thing to check if using new pads on old discs is that the extreme inner and outer edges of the braking area will not be flat like the new pads. There will be a small radius so you need to gently radius the new pads inner and outer diameters to match. Otherwise you will just be braking on the radius bit for a while which is like having no brakes at all!

The quick garage way to de-glaze disc brakes is to find an empty road and do a few emergency stops from 60mph to standstill. If the discs are glowing red after this you have done it correctly!
Keep at it you wil get there in the end! Peter.

[gouldsborough7]

Re: Improving performance of Hunter brakes?

OK Peter
Will try your method of glaze-busting. I plan to swap over the discs - left to right and vice versa, so I can add you method to the plan when the discs are on the bench. By swapping the discs over, I thought if nothing else the left-pull tendency should change to a right-pull.

After I follow your idea + mine, and the car brakes in a straight line, then job done!

Just another angle to the problem - I was a a kit-car meeting in Baldock, Herts local all-makes club, and a bunch of guys got very enthusiastic about my Hunter. Firstly the engine (Ford 2 litre DOHC 420i), but that another story!

Then talking to them about the brakes saga, one guy suggested the the new lower nearside wishbone did not match the design of the offside one. The new & old wishbones looked very similar, but not identical. His theory was that this might be causing the car to crab very slightly, and no amount of fine-tuning of the brakes would iron out that defect. He suggested I should accurately measure the wheel-base on both sides to verify his point.

I'll keep that idea on the back-burner for the time being. Will provide a follow-up on the disc fettling in a few days, domestic life permitting!

Cheers
Mike