Caliper Referbishment

The brakes fitted to my LC are AP Racing units. The front’s are a 4 pot caliper with a 330mm vented disk, whilst the rears are a two pot design and a 300mm vented disk. For about the last five years, the car has had all its main services done by Welch’s in Bristol. About a two years ago, they advised that both the front and rear brake disks were getting to the point where they needed replacing. Shortly afterwards, a heavy vibration from the rear developed during braking. Because I live about an hour from Bristol, I took the car to a local garage to diagnose the problem. The cause was a broken rear brake disk – The webbing that connects the two sides of the vented disk had cracked, causing the two halves of the disk to spread apart, resulting in the vibration during moderate/heavy braking. The disk’s had to be replaced, so whilst they were at it, I got them to replace both the main rear brake pads, and the handbrake shoes.

It came as a bit of a shock when I was told the cost of the parts. New rear disks are about £600 a pair, whilst the pads are around £100. The only reasonable bits are the handbrake shoes, which apparently are the same as any other Carlton, and cost about £20. I had no time to search for cheaper equivalents, so I just got the credit card out and coughed up the dosh. At the end of the job I was advised that the brake caliper pistons were starting to corrode, and that I ought to try and find replacement piston and seal kits. I decided to do some research into this and the front brakes, which were going to need doing in a few months as well.

First stop my local Vauxhall Dealership. They were very helpful, but told me that replacement piston/seal kits are not available for the LC. You have to buy the complete caliper, and they are £500+ each. I went straight home to inspect both the front and rear calipers. All 12 pistons (8 front and 4 back) were in a similar state, and would all need replacing. What seems to happen is that as the brake pads wear, the pistons push further and further out of the caliper. The harsh environment around the brakes causes the chrome plating on the piston to be damaged. Once the chrome coating has been breached, the piston starts to rust. This in itself isn’t a problem, but when you fit new brake pads, the piston has to be pushed back into the caliper. If the corrosion is severe, this can damage the seals and/or bore in the caliper, and in extreme cases, lead to loss of brake fluid around the internal seals. I made a few measurements on my car, so that I could start phoning around for information.

Next stop my local motor factors. Again they were helpful. They discovered that the rear brake pads are the same size and shape as the front pads on a 1973 Mini. This means that even my local Halfords stock pads for the rear ! The only thing to be aware of is that the material used for the pad is different, so braking may be impaired. You may be better off using competition pads, which are available from companies such as Mintex or Ferrodo. Since the rear brakes are responsible for less than 30% of the braking effect, I think that £20 for these is a much better idea than £100+ for Vauxhall ones.

But when it came to the front’s they were unable to help. Ferrodo do/did list the front brake pad in their catalogue, but when an attempt was made to order it, they said the part number didn’t exist. The motor factors were also AP Lockheed stockists, but they do not handle AP Racing equipment. They told me that AP Racing and AP Lockheed are two completely separate companies, and couldn’t tell me where I might get AP Racing gear.

So next stop, the Internet, to search for AP Racing. Success ! AP Racing have about 10 distributors in the UK. I rang the first on the list and they said they could supply the parts and gave me prices. However, when I attempted to place an order I discovered that they didn’t have some of the parts in stock, and they would be on 4-8 weeks delivery. So I rang some other distributors. One of them told me that the original brake disk thickness was 32mm, and that the minimum permissible thickness was around 30mm. Since mine were only 28mm, I should stop using the car until I had them replaced! I rang Welch’s to ask what the workshop manual said the minimum thickness should be. They were either unwilling or unable to tell me (the former I suspect), and told me that the check they perform during a service is only a visual one.

Eventually I rang BG Developments (see below), and spoke to Dave Buchholz. He was extremely helpful, and even sent me a list of the parts I would need to completely overhaul the front calipers and brakes. All of the parts were cheaper that the first dealer by 10% or so – another rip-off merchant trading on the exclusiveness of the LC !. The original list of parts and part numbers is available here. Since then, Dave B has sent me a revised 2000 price list, which is shown below. (prices excl. VAT & delivery):

Part Number	Description	Cost Each	Quantity Rqd	Total Cost
CP3930-2P	Brake Rotor & Bell Assembly - r/h	£293.38	1	£293.38
CP3930-3P	Brake Rotor & Bell Assembly - l/h	£293.38	1	£293.38

Part Number	Description	Cost Each	Quantity Rqd	Total Cost
CP3930-840P	Brake Disk Rotor - r/h	£195.13	1	£195.13
CP3930-841P	Brake Disk Rotor - l/h	£195.13	1	£195.13
CP2494-6	Disk/Bell Mounting Kit	£10.45	2	£20.90

The original disks on my LC were marked 9KK, and were a single piece design. I am told, but cannot confirm, that if you order the replacement disks from Vauxhall, they also now supply a two piece Bell/Disk design. This costs about £413+VAT (£485) a pair.

The Brake disk detailed above consists of an outer rotor (CP3930-840/841) and a central mounting bell (BGMB920). The bell is not supplied by AP Racing, but is made to order by BG Developments, so whoever you get your parts from will have to make or source an equivalent. The bell is bolted to the disk using 12 bolts supplied in the CP2494-6 mounting kit. If you are buying the disks for the first time, then you can buy the set ready assembled as CP3930-2/3. On subsequent replacements, you only need buy the rotors and bolts.

The two piece brake disk works out about the same price as the Vauxhall equivalent. The advantage of the two piece design is that when the disks need replacing again, you only need to buy new disks and new bolts. This will be considerably cheaper that a complete new Vauxhall kit. You can also get different disks if you want drilled/grooved ones. I was advised not to use them by BG Developments. The grooves increase the amount of brake noise, and also increase the amount of break pad wear. The reduced surface area and uneven surface can also cause the disks to overheat and warp after a few thousand miles. They may be OK for touring cars, but they only do 50 miles between services!

BG Developments can also supply brake pads (Part number CP3215-167-3432F) for about £100 a set which are supposed to be the same material as the Vauxhall ones. The only difference is that they don’t have the brake pad wear sensors. This didn’t bother me as I check the pads regularly anyway. If you decide the same, carefully detach the sensors from your existing pads and fix them securely to the suspension . Don’t break them off or remove them completely, or you will end up with the dashboard warning light permanently on. I would strongly advise any LC owner to keep a spare set of brake pads in the garage, so that when they need replacing you can do it yourself, or get a local garage to do it for you.

Part Number	Description	Cost Each	Quantity Rqd	Total Cost
CP2667-153	Piston 1.50x33,3STL-SIB	£12.70	4	£50.80
CP3395-149	Piston 36,0x33,0STL-SIB	£12.70	4	£50.80
CP2370-2	Piston Seal - 1.50 STD	£2.14	4	£8.56
CP3395-181	Piston Seal - 36,0 STD	£2.14	4	£8.56
3853-742	Wiper Seal - 36.0	£2.14	4	£8.56
3865-742	Wiper Seal - 1.50	£2.14	4	£8.56
CP3395-147	Wiper Seal Retainer 38.1	£7.69	4	£30.76
CP4100-112	Wiper Seal Retaine 36.0r	£7.69	4	£30.76
CP4100-113	Bleadscrew-M10	£0.56	4	£2.24

The pistons I ordered were standard chrome over steel ones, which is what I think the STL-SIB suffix to the part numbers means. I have recently noticed that the pistons are starting to rust again. I believe that it is possible to get alloy pistons, which should not rust, and so may be a better bet. As soon as I get more information on these, I'll post part numbers and prices. I am also lead to believe that it is possible to get high temperature seals. Notice the seals listed above have a STD suffix. The AP Racing web site says that if your brake caliper temperature exceeds 240 degC you should replace the seals. Since my fluid has boiled on a couple of track days, and brake fluid has a boiling point of about 260 DegC, then higher spec seals may be a good idea. Again, I'll post part numbers and prices as soon as I have them.

I ordered all the parts and gave them to my local garage to do the work. They told me I should also replace the brake fluid because the boiling point was well below 200 degrees C. It should be 240+. I rang Welch’s to check if they had replaced the fluid at the last service. I was shocked to discover that they had never changed the fluid – ever! Apparently, the fluid isn’t changed routinely at the service because it only needs changing every 12 months, regardless of mileage. And because the services are at 9000 mile intervals, they can’t tell if the fluid has been replaced in the last year. They are supposed to ask you at the service if you want the fluid replaced, but no-one has ever asked me. If you own an LC, get your garage to check the fluid NOW, before you end up in a hedge (or worse). AP Racing can supply race spec brake fluid at a price, but I just got the garage to use DOT 5.1 fluid, which is available from almost any garage or motor factors.

During the replacement, the garage also checked the run-out on the new disk when fitted to the car using a dial gauge. They found an excessive amount on one side (about 4 thou I think from memory) which could not be cured by rotating the disk on the hub. They thought that a new disk ought to be a lot less that that (less than 1 thou ? ). After several days investigation, measuring the new disk and bell, it turned out that this was due to a worn front wheel baring, so I had both barings replaced as well.

Since this work has been carried out, I have also had the rear calipers overhauled. I let the garage order the parts for this so I don’t have the details on the original part numbers and prices. All I can say is that the pistons/seals/retainers were a similar price as those on the front. However, Dave B has also supplied me with a list of the current prices (May 2000), which is reproduced below. You can also buy rear pads made from the same material as the Vauxhall ones from BG Developments, if you don’t want to use Mintex/Ferrodo/Halfords ones.

Part Number	Description	Cost Each	Quantity Rqd	Total Cost
CP4100-114	Piston 1.25x29,5STL-SIB	£12.50	4	£50.00
CP2414-117	Piston Seal - 1.25 STD	£2.14	4	£8.56
CP3477-105	Wiper Seal -1.25	£2.14	4	£8.56
CP4100-115	Wiper Seal Retainer 31.75	£3.62	4	£14.48

In summary, I cannot advise anyone on the suitability or wisdom in using the parts described above. To the best of my knowledge, the information is correct, but you use it at your own risk. Whilst a car is still in warranty, you should probably continue to use genuine Vauxhall/Opel/GM replacement parts. I am not a qualified mechanic or brake technician, so some of my assumptions and comments may be inaccurate or incorrect. If in doubt, get some specialist advice.