Improving performance of Hunter brakes?

[gouldsborough7]

Having been used to the high performance of my Skoda Octavia brakes, each time I get back into my Hunter I have to re-adjust braking distances and brain, as one might expect with old technology.

Recently, on braking, the car has developed a tendency to pull to the left. I mentioned this is a previous message, and got a few suggestions to check & sort this out. I will shortly be checking out all of the basics, and hopefully find that the cure will involve no more than a replacement of the off-side calliper. If this is the case, I will probably be tempted to replace both of them to ensure a balance. The front pads have stacks of lining material left, so do I keep them? Although they have done only 9,000mls, should I replace them with really some grippy stuff? With a low annual mileage, it wouldn't matter if the material wears down quicker than normal. Anyone know where to buy such pads?

The car was built with 1998 Ford technology, and still has drum brakes at the rear. So any changes to be there?

So then I got to thinking that possibly I should be thinking about beefing up the whole brake system? Compared to regular cars, the servo is quite small. I also read (in an old Forum message of 1995)somebody was suggesting an up-grade of master cylinder size.

So there's my dilemma - starting off with 'pulling to the left' and ending up with wholesale replacement of all or part of the brake system.

Has anybody got any fairly economical ideas on tweaking up my brakes?

Cheers
Mike

[CosworthCabrioLee]

Re: Improving performance of Hunter brakes?

Hi Mike,
Have you looked ath the idea of transplanting the braking system from a xr4x4 ? they have bigger brakes and discs on the back, This is what I intend to do this winter on my v8 there will also be a LSD diff getting fitted.

[dogoncrazy]

Re: Improving performance of Hunter brakes?

Mike
I never found the brakes to be inadequate on my cabrio, remember it's a lighter car than the donor it came from , so shouldn't be an issue in my opinion.

[Cabrio_Simon]

Re: Improving performance of Hunter brakes?

Mike,

I'd agree with Alan that the standard brakes should be more than adequate once they're sorted.

However, when building my car I upgraded to the bigger Sierra brakes fitted to the XR4's and some later cars:

http://www.flickr.com/photos/marlin_bmw_cabrio/sets/72157594349599658/

The front is quite easy to do as you will "just (!)" need the bigger 260mm discs, calipers and caliper mounting brackets.

I'm not 100% sure what's involved with changing the rear from drum to disc as I swapped my complete axle for the disc brake version (as it comes with the stronger 7.5" diff which I wanted with the higher power and torque of the BMW engine).

I also ended up swapping my master cylinder to the disc brake type as I didn't want to run the risk of the front to rear balance being wrong.

So it could be quite alot of work but certainly possible.

Simon

[mark_tinkler]

Re: Improving performance of Hunter brakes?

The Sierra range also includes ~280 or ~300 mm disc options depending on wheel sizes. At one time it was possible to get a set of brackets that allow the caliper from the 240 disc to be used with the larger discs. I was looking to see if these are still available and found this interesting page describing how a bracket could be made
http://www.lukeb.org/sierra/brakes.htm.

Making up a bracket of this type would give bigger brakes without the cost of new calipers. Need to check that the flexi hoses are not strained by increasing the distance from the caliper to the steering axis.

Might be worth a bit more research on the Ford Focus disc options to see if it's possible to get a ~280mm disc with extra 3mm space for the bracket. I think 280 is the largest possible with 15 inch wheels.

Increase in braking force from 240 to 280 discs should be approx 16%.

This is something that I've thought about a few times as I have an unfinished YKC roadster with 3.5 v8, but it will be quite a while before I actually try it, as I have XR4i donor and a lot of other things to do first.

[csjcarolyn]

Re: Improving performance of Hunter brakes?

Mike,
you need to be careful with changing the master cylinder size {in isolation?] as the braking force WILL decrease. pressure in the master cylinder = force/area while the brake force pushing the brake material onto the disc/drum is pressure times area. Just put in some imaginary figures then increase the diameter of the master cylinder and see what happens to the brake force.

Roger

[gouldsborough7]

Re: Improving performance of Hunter brakes?

Thanks Guys
On reflection, for the time being I will try and get the existing set-up working as well as possible. With the car pulling to the left on braking, my local garage has already identified that the offside front brake was less efficient than that on the nearside. The problem is not major, but shouldn't happen.

As a belt & braces exercise, I checked out both offside rear & front brakes over the weekend. I half-expected to find the slave cylinder & linings (drum) on the rear offside to be wet with hydraulic fluid, but all was well. Took the front calliper off, and pumped the brake pedal until the piston moved about 20mm. Wound it back with a big G-clamp, and repeated a few times. NO oil leak or other obvious problem! Put it all back together, drove up the road and no big surprise to find car still pulling to the left on braking.

Assuming there are no snags, as a test I'm tempted to swap the callipers left-right & right-left, together with their respective pads. The car should then pull to the right on braking, shouldn't it? - pointing to either calliper or pad defect. If still pulling to left, that will eliminate the brakes, and then what?

In terms of improving brake efficiency, I remember in my early driving days owning a Hillman Imp Sports with a tweaked up engine. This was before disc brakes were the norm, and it had drums all around. However, Chrysler had fitted this model with green Ferodo linings. This improved the stopping power somewhat, but they wore out in less than 10,000mls and were seriously more expensive than the standard stuff. I wonder whether the equivalent Ferodo linings are available with pads? Anybody know?

Cheers
Mike

[chris_cussen]

Re: Improving performance of Hunter brakes?

Mike,
the problem you will have if you swap the calipers over is that the bleed nipples will be on the bottom and not the top, and you will have great difficulty in bleeding them effectively.

If it was me, assuming the discs themselves look OK I'd change the front pads, and if that didn't cure it change the left caliper.

[h_m_cumming]

Re: Improving performance of Hunter brakes?

I had a similar problem when I first built my Roadster, and it was a disc, new, that was at fault.I swaped the pads first then the discs before it moved to the other side, then swaped the pads back to prove it was the disc. My motor factors changed the pair under guarantee even although I'd bought them about six months earlier.

[gouldsborough7]

Re: Improving performance of Hunter brakes?

Thanks Chris/Hugh
Not having checked out the geometry of the callipers, I guessed there might be a problem in doing a swap over, but didn't know exactly what.

I think part of the problem might be that the car has only done 9,000 miles in 11 years, and spent some of this time in storage. The pads have stacks of lining material, but due to age they might not be offering the same grip as each other. Similarly, the callipers have done very little work, but one piston might for example be tighter in its bore than the other, and behaving differently in operation. I've no idea whether the brake fluid has ever been changed, but it is on my list to do as a No.1 priority.

I might bite the bullet and change both callipers and pads. Your messages were well-timed as I am just about to visit my favourite motor-shop! Will let you know how things work out.

Cheers
Mike

Cheers
Mike

[gouldsborough7]

Re: Improving performance of Hunter brakes?

Follow-up:
I took the plunge and replaced front pads & callipers, renewed brake-fluid, and while the car was on blocks replaced rear slave cylinders as well. The slaves are fairly cheap, and I could guarantee that in a few weeks the old rusty-looking ones would have started to leak! The rear linings were in good nick, and there was no reason to change these.

On a test run, I was disappointed that the car still tends to pull to one side on braking, but there was a slight improvement. The consolation was that all the crucial bits and brake-fluid are new, so that should make for reliable stopping for a few years.

So, still pulling very slightly to left when braking, but it shouldn't! Got to thinking that this may be influenced by having had the nearside lower wishbone & ball-joint replaced by my local garage (the offside passed their inspection). As part of this operation, they adjusted the tracking setting. The man said that the original setting was drastically toeing-out.

Could the pulling left be as result of different reactions of the 2 halves of the front suspension, when the brakes are applied? If the nearside wheel moves fractionally backwards as compared to the offide, wouldn't that cause the slightly pulling-to-left problem? I am just clutching at straws, and perhaps another member has more expert ideas on this?


Cheers
Mike

[chris_cussen]

Re: Improving performance of Hunter brakes?

Well going by a process of elimination the only major component of the braking system you haven't changed is the front discs.....

I have experienced some degree of pulling to one side when a suspension component has been not done up tight enough, which caused the wheel to move and point in an odd direction, so maybe you need to check all the track rod ends, suspension joints and rubber bushes.

If you could persuade a MOT station to put the car on the MOT brake test rollers it will show that there is uneven breaking force across an axle. If it isn't that then it must be a suspension geometry problem.


Sorry I can't be more positive.

[gouldsborough7]

Re: Improving performance of Hunter brakes?

Hi Chris
My local MOT village garage did do a rolling road test on the front wheels, prior to my taking the plunge on replacements. The garage guy identified the nearside calliper as working better than that of the offside. This made some sense, and not wishing to 'spoil the ship for a ha'pence of tar' I replaced both pads & callipers, plus fluid change as I had no idea how old it was.

The discs look almost new, as my car has only done 9,000 miles, but spread over 11 years! So that lead me think of non-matching of wishbone performance - offside v nearside. Perhaps the rubber bushes between the rollbar ends and the wishbones are behaving differently? I'll do some checking of the components as you suggested.

Cheers
Mike

[chris_cussen]

Re: Improving performance of Hunter brakes?

Since you have uneven braking effort I'd suspect the discs as the only item left, see Hugh Cumming's post above.

If its been through a recent MOT they should have checked the suspension components for excessive wear or movement.
Chris

[Peterx]

Re: Improving performance of Hunter brakes?

I'm sure you have, but have you checked your tyre pressures are all correct?