Mini Sport Alloy 4 Pot Caliper Dust Seal Failure

I bought a pair of Alloy 4 Pot Calipers from Mini Sport. While installing them I noticed that the dust seals were loose in the body of the caliper. This is not a good thing! The dust seals were tight around the pistons, but were free to move out of the body of the caliper. As the pads wear, the pistons move out of the caliper and take the dust seals with them.

The dust seals protect the main hydrolic seals which are immediately underneath the dust seals. These upper seals consist of a two lipped rubber ring retained by a metal ring. The metal ring should be a tight fit in the caliper and the rubber ring should be snug on the piston. The later is true, however the former is not.

I had discussions with Mini Sport, and they suggested forcing the seals hard into the caliper. Apparently the calipers have a taper and that should retain the metal ring. I tried this, and it did work, for a while. However, every time I took the wheels off, more than one of the seals would have moved.

I called up Mini Sport, and they had a think about it, and finally suggested returning them to England. New Zealand Post lost the calipers somewhere between New Zealand and England! They eventually turned up 6 weeks overdue, and Mini Sport repaired them and returned them to me.

When they arrived, the first thing I noticed was one of the calipers had a small dent where the hose screws into it. This dent was about 2.5 mm long and reasonably deep. I didn't think that the copper washer would seal over the dent, and when the calipers were installed, they leaked from this point. I did the hose up as tight as I dared but they still leaked. I did not want to overtighten the hose, as the first thread had already been pulled up when I initially fitted them.

I solved this problem by placing some wet and dry sand paper on a sheet of glass (glass is generally very flat) and rubbing the caliper on it. This worked quite well, I filled the hose hole with rags to try and minimise filing entry. Then I forced out some of the fluid in the caliper to hopefully flush away all the filings. This wasn't totally successful, but it turned out not to matter:

I mounted the caliper for a second time, and after installing the pads I noticed that one of the dust seals was loose!!!! I'd just sent these calipers back to England to fix this very problem! Not only that but I had just purchased a $35 set of standard pads for them. They are metro pads and have the wires for the worn out pads warning light. I cut the wires off, so now I cannot return them.

I am totally happy with the performance of these calipers apart from the dust seal problem. However, I have given Mini Sport two chances to correctly assemble the calipers (when they first put them together and when they repaired them). They have failed both times to do the job, and this does not give me much confidence in them, and I asked for my money back.

I was not really expecting a full refund from Mini Sport, after all I had been using the calipers for 9 months. I spoke to Mick Holt at 3am in New Zealand time, and he agreed to refund the full purchase price. This did not happen, and when I queried why, and Mick said that he had said I would have any refund I had arranged with Chris Harper, the sales manager (I had made no arrangements with Chris). I don't think I would have missunderstood this, but the conversation occured at 3am, and I cannot be totally sure.

Chris Harper offered to refund half the original cost of the calipers plus the costs that I had incured shipping them back to England twice, or replacing the calipers and refunding the shipping costs. I was not pleased by this offer. I felt that depreciation by half in 9 months was not acceptable. I discussed this offer with the members of the mini-list, where signficant debate ensued. Opinion was divided between accepting the replacements, and demanding a full refund.

I emailed Mini Sport, offering to accept a 3/4 refund. They replied saying they would give me a FULL refund, plus shipping costs!! I cannot explain this, except perhaps the publicity on the mini-list was a factor. Mini Sport were aware of the discussions on the mini-list. I am very happy with this outcome.

If you wish to peruse the actual postings on the mini-list then surf over to the listquest archive. Search for my name (Tom Parker if you didn't catch it) and "Mini Sport" and you should find most of the postings, try "caliper" instead of Mini Sport and you should find the rest.

This is one of the calipers. Notice the scratches. They are so close to the inside of the wheels, that stones are a problem.

Here it is reasonably obvious that the left seal is sitting a little proud of the surface compared to the other. When I took them off, 2 months after I last pushed them down, 5 or 6 of the 8 seals were sitting up like this one.

Mini Sport sent me road pads, however these pads don't look like road pads, they require a LOT of pedal effort compared to the drums I had previously, and the 1275GT calipers with unknown pads that I'm currently using. Everyone I've shown them to says that they are a metallic pad, and they do need some warming up before they work to the full potential, although it is minimal. I have NEVER faded these pads, even after 20 minutes on a race track, when they smelt strongly inside the car Mini Sport say that the part number on the box, DP564 matches with the road pads they supply. A pity, as I'd like to know which material these ones have.

Notice also the top pad has the corners cut off. These pads are for the Metro 4 pot caliper, with the inner pad requiring the trimming.

I have ordered the KAD 4 pot calipers suitable for vented discs, mini driveflanges and 10" Steel wheels. I changed to vented discs as my current discs are well under the minimum thickness (aparently 8.6mm...), and vented discs are not significantly cheaper than non-vented.