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Hi all

Anyone know exactly which Mini (or other) seals were used in the Taffspeed inboard hydraulic conversions?

I was very kindly supplied a couple of spares by a fellow Lambretta enthusiast a number of years ago but have only now rebuilt the brake and fitted it to a bike. Whilst the seals looked like a like for like swap, I've struggled to bleed it and now find that the seal is allowing fluid past the piston in the slave cylinder.

Upon inspection, the inner and outer diameters of the seals look the same but the thickness of the seals is slightly different. The old one that I took out looks to be approx 3.1mm thick, whereas the new one is more like 2.6mm thick. Whilst this could be an issue with the seal swelling over time, I doubt that to be the case as the other dimensions are very much the same; I.D. and O.D.

Perhaps I should be talking to Mini spares suppliers, as I note that they list different part numbers for different models. Whilst they all appear to be much the same, the minor differences could well be the cause of my current issue. NB: The current seal will allow slight pressure to build but it soon fades and fluid is being forced past the seal... so it is very close to doing its job, just not quite!

Any historical detail that anyone can offer would be much appreciated.

TIA

I would go to hydraulic engineering supplier they should be able to match the seals

Hi Adam
I had a similar problem recently and Mike Gervin came up with the idea of ever so slighly boring out the inside of the slave cylinder to a standard metric size of commonly available seal & piston.

It's worked a treat and I can replacd the seal every 12 months in the knowledge I can easily get new seals and/or pistons now.

He's a clever lad

missing lynx wrote:I would go to hydraulic engineering supplier they should be able to match the seals

+1

Thanks for the responses guys.

It looks as though inaccurate seal manufacture may be playing a part in this problem as seals that should all be the same spec are measuring anywhere between 2.5mm thick to 3.2mm, which may be affecting how they distort under hydraulic pressure. Well, let's hope that is the case, in which case swapping to the correct thickness seal may resolve the issue.

I have more seals + new piston on order so will let you know how I get on, as it might help others out too.

Cheers

If you get hold of Bob West he might know. Failing that Paul Baker or Ralph Remnant might be able to give you a point in the right direction.

Well, looks as though I've sorted it (hopefully). A few things to note:

1. Yes, the Mini Metro Turbo seals and pistons are the right ones, but do keep an eye out for the thickness varying too much. I looked out the correct thickness one, approx 3.2mm.
2. Once the lever would take pressure I noted that the biting point was very late in lever swing, with full travel being covered before much pressure could be applied. Right, I have to confess that I'm using this with a hidden (semi hydraulic) master cylinder, which are often a lit 'spongy' but not this bad! Upon inspection I noted that there was a considerable misalignment between cable stop and plunger/piston lever, meaning that much of the lever movement was being spent just to take up the slack to bring it back on alignment. To rectify this issue I have spaced out the lever pivot so that it is better aligned and with less slack. The result is that it now bites much sooner and completes brake operation before running out of lever travel.

3. Thank god for Dot 5 silicon fluid, which Dave Webster put me onto many years ago. Without it it probably have no paint left on my bike!

Well, first impression, after a short test ride is that it now works really rather well. Not quite as 'amazing' as my similar DJ version on another bike, but it may improve as it beds in (new pads on an old disc).

Thanks all, the help/info/advice is all much appreciated.