rear back plates - rear slave cylinders

[YMJ]

Just stripped down the backplates of the racer to routinely replace the slave cylinders for the new season. And the new slaves don't fit.....on either side! The roll pin is located back-to-front .....or front-to-back. You know what I mean.
Anyway, no problem I thought. I've got another pair of new slaves in store. And guess what? They don't fit either.
One interesting point is that all three sets have different diameter pistons... 1/2", 5/8" and what looks like nearly 3/4" (they're the ones on the car at the moment).
I'd like to get the job done tonight. Is there a problem with simply drilling a new hole for the roll pin on the other side?

P.S. has anyone got a timeline for the backplate changes and for when the different diameter piston slaves were introduced?

[Spider]

The various roll pin locations where to prevent fitting the wrong size cylinder, but everyone just says 'it's in the wrong place' and drill them anyway!

A lot of the new cylinders are just enough out that even with the right bits, they still don't go straight on.

No problem in drilling them.

[rolesyboy]

I have a distant memory that they are for a Metro if the roll pin sits on the opposite side. Cheers. Mark

[rich@minispares.com]

there is no issue drilling either the back plate or cylinder to swop pin sides, some aftermarket cylinders used to have both sides drilled.

the back plates where made like this so that people couldn't fit one size cylinder to one side, and another to the other - or at least not without having to do something about it.

[YMJ]

Thanks all.
The drill has been taken out and is on charge......I mean.....how hard can it be?

[surfblue63]

Won't fitting cylinders with a different bore upset the brake balance. Surely if a smaller bore is fitted it will require less fluid volume to move the shoe the same amount?

Also the 3/4" bore are Rover ones from 1980's onwards.

[swifty]

If I'm using four pots up front I always use a smaller bore at the rear . This is because of using less fluid and therefore bringing up the pedal a bit . Works for me ... Ken

[Spider]

Won't fitting cylinders with a different bore upset the brake balance. Surely if a smaller bore is fitted it will require less fluid volume to move the shoe the same amount?

Yes, spot on I recon.

What's happened here over the years though is people do up grades from Drums to Discs and retain the original rear backing plates (I never bothered to change them), or replacement backing plates are fitted and rarely ones with the pin hole that matches the car.

Also the 3/4" bore are Rover ones from 1980's onwards.

They did still fit a variety of sizes, 4 I know of off hand were 9/16", 5/8", 11/16" and 3/4". I think there was also a 1/2" one too.

[Inno Cooper]

I think there was also a 1/2" one too.

Wasn't that one first fitted to the (british) 1275 GT when it got 8,4" discs?