Engineering help required - not Ultima

[davejw]

Hi guys,

This is off topic not being an Ultima. I have a BMW Alpina Bi-Turbo (old K Reg 5 series...) and have just replaced the cast iron 4 pot calipers on the front to Brembo alloy calipers from the 840 CSI. I went Brembo as it was a straight swap.

The trouble is the master cylinder seems to be too small, so I have a very long pedal before proper contact is made. If I pump the pedal the brakes are amazing - as this is not the way to do things I need to re-engineer the master cylinder.

Current bore size is 1 inch and I've searched high and dry for a larger bore master cylinder without luck.

Does anyone know of a decent engineering outfit who could line bore the cylinder and machine a new piston? I'll have to sort out 'O'Rings but reckon this is modification would't be too difficult for someone with access to the right machinery and skills.

Anyone got any other suggestions?

Cheers,

Dave.

[gdr]

Assume your current set up has a single master cyl. for all 4 calipers. Could you fit a pair of master cylinders with balance bar? You'd need to size front and rear correctly to get basic balance OK of course.

[Hugger Z]

Can you get the master cylinder off that 840 CSI? It obviously was used with those brakes before and should work if it will fit on your current car. It ought to be worth a try. Or if you can at least find the specs on it, you would know what bore & stroke you need to try to develop.

>> Edited by Hugger Z on Wednesday 18th January 15:33

[andygtt]

Can you re-engineer the brake padal to reduce the ratio of the pedal? I did this the other way on my Ultima to make the clutch pedal longer and thus lighter.

[davefiddes]

davejw said:

Does anyone know of a decent engineering outfit who could line bore the cylinder and machine a new piston?

The cylinder walls on aluminium master cylinders are specially hardened. I think you'd have great difficulty finding somewhere capable of doing the appropriate work for a reasonable price. Finding a standard part that would fit or be made to fit is a better bet.

Dave