Dual 7" Servo

[peterux]

I think I have solved the puzzle of the 'Ford' Master cylinder part number.

After double checking and then realising my BMW master cylinder is actually a dual diameter bore size, I decided to go for a 22mm cylinder.

Based on a hunch that the Marlin supplied M/C it was off a Ford Sierra and Mike's info that it is a Bendix OE, I ordered a BMC4052 from Brakes International.
It arrived today and has the magic numbers 383059 on the side.
It's just like Jason's but with the outlets on the engine side.
It is manufactured by an Italian firm called Cifam. (www.cifam.it)
The logo on the M/c is Ci. It is Cifam part number 202-099.
The Cifam website and catalogue has lots of useful info with pictures, 'where else used' and other suppliers equivalent part numbers.
It is brand new in a sealed box and was delivered to my door about 42 hours after I placed the order!
Manufacturers packing date is 08/07/11 so nice fresh stock.
Total price was £57.96 inc. VAT and courier delivery.

Thanks to Robin for finding www.brakesint.co.uk

I'll be checking all the relevant measurements and post some pictures over the weekend.

...peter

PLEASE READ POST #525 below before ordering this M/C. THIS PART NUMBER MAY ONLY BE SUITABLE FOR CARS WITH DRUMS AT THE BACK

[mashtun]

Aha! So that logo on the side of mine is Ci! Well spotted, Peter

Mine is exactly the same model, sourced 18 months ago from the ebay seller Mike linked to up-thread.

Mark.

[Mike]

Originally Posted by peterux

I think I have solved the puzzle of the 'Ford' Master cylinder part number.

After double checking and then realising my BMW master cylinder is actually a dual diameter bore size, I decided to go for a 22mm cylinder.

Based on a hunch that the Marlin supplied M/C it was off a Ford Sierra and Mike's info that it is a Bendix OE, I ordered a BMC4052 from Brakes International.
It arrived today and has the magic numbers 383059 on the side.
It's just like Jason's but with the outlets on the engine side.
It is manufactured by an Italian firm called Cifam. (www.cifam.it)
The logo on the M/c is Ci. It is Cifam part number 202-099.
The Cifam website and catalogue has lots of useful info with pictures, 'where else used' and other suppliers equivalent part numbers.
It is brand new in a sealed box and was delivered to my door about 42 hours after I placed the order!
Manufacturers packing date is 08/07/11 so nice fresh stock.
Total price was £57.96 inc. VAT and courier delivery.

Thanks to Robin for finding www.brakesint.co.uk

I'll be checking all the relevant measurements and post some pictures over the weekend.

...peter

Peter

Can I ask a couple of questions so that others can consider their options?

Have you fitted standard BMW brake parts in the rest of your system?
Do you know the bore size of your original m/c? - you say it is dual diameter bore size? Are you suggesting the two bores are different sizes?

The reason I ask is you are negating a significant part of the impact of increasing the servo pressure, by opting for the larger bore master cylinder.

Robin has stated his BMW bore size is 20.6mm in his standard set up. I know it does not sound much different, but the pressure in the brake system transmitted by the bore is related to the surface area: the bottom line is the 22.2mm m/c will be 16% harder to press than the 20.6mm. This is significant, given the reason for going to all this trouble is to make the brake pedal easier on the leg muscles.

I chose the 22mm bore m/c as it matches the original Ford Sierra spec to go with my Ford Sierra brake set up. The dual servo gets closer to the original Ford 8" servo, so I should have a system as close to Ford's original spec as possible. By opting for the 22mm bore you are making yours 16% harder to press than in the donor BMW (using Robin's bore figure)


There are, of course, other considerations. The pedal travel on the 22mm bore will be 16% less than the 20.6mm bore and it may be felt that this is worth having - I am in no position to comment as I do not know what it feels like in a BMW based car.

I do not wish to suggest you have got it wrong, but others following this thread need to understand that all our cars are not the same, and that a m/c that works in a Ford set up will not necessarily perform the same in the BMW set up. All other things being the same in the brake set up, my preference would be to opt for a m/c with the same size bore as the donor?

Of course you can suggest Jason has fitted the 22mm bore in his BMW set up and is happy. Given the opportunity to do it again with a 20.6mm bore and 16% less effort, but longer pedal, what would he do next time?

Please take this as a constructive question, for the benefit of others who are still able to choose their set up.
Regards
Mike

[Mike]

Several of you have asked about reservoirs fitting the Sierra BMC. The photo below shows the standard Sierra reservoir on the left: on the right are reservoirs from Mk1 Fiestas. These fit the Sierra BMC.

In my Cabrio headroom above the reservoirs is my critical issue. The Sierra reservoir has a maximum depth of 85mm above the BMC - the Fiestas are 90mm.



Will either of these fit in a Sportster?
Would any one like to try the Fiesta option? They both need a home?

Mike

[peterux]

Originally Posted by Mike

Peter

Can I ask a couple of questions so that others can consider their options?

Have you fitted standard BMW brake parts in the rest of your system?
Do you know the bore size of your original m/c? - you say it is dual diameter bore size? Are you suggesting the two bores are different sizes?

The reason I ask is you are negating a significant part of the impact of increasing the servo pressure, by opting for the larger bore master cylinder.

Robin has stated his BMW bore size is 20.6mm in his standard set up. I know it does not sound much different, but the pressure in the brake system transmitted by the bore is related to the surface area: the bottom line is the 22.2mm m/c will be 16% harder to press than the 20.6mm. This is significant, given the reason for going to all this trouble is to make the brake pedal easier on the leg muscles.

I chose the 22mm bore m/c as it matches the original Ford Sierra spec to go with my Ford Sierra brake set up. The dual servo gets closer to the original Ford 8" servo, so I should have a system as close to Ford's original spec as possible. By opting for the 22mm bore you are making yours 16% harder to press than in the donor BMW (using Robin's bore figure)


There are, of course, other considerations. The pedal travel on the 22mm bore will be 16% less than the 20.6mm bore and it may be felt that this is worth having - I am in no position to comment as I do not know what it feels like in a BMW based car.

I do not wish to suggest you have got it wrong, but others following this thread need to understand that all our cars are not the same, and that a m/c that works in a Ford set up will not necessarily perform the same in the BMW set up. All other things being the same in the brake set up, my preference would be to opt for a m/c with the same size bore as the donor?

Of course you can suggest Jason has fitted the 22mm bore in his BMW set up and is happy. Given the opportunity to do it again with a 20.6mm bore and 16% less effort, but longer pedal, what would he do next time?

Please take this as a constructive question, for the benefit of others who are still able to choose their set up.
Regards
Mike

Hi Mike,

OK, no problem. Let me answer your questions and take you through my decision logic. (But only time will tell if I got it right )

My brakes currently are all standard BMW, but I am a little different to most BMW builders as my donor car was only a 2 litre so was fitted with drum brakes at the rear.
According to realoem there are lots of options fitted to these cars with some fitted with dual bore MC's 22,20/17,46MM.....others were fitted with 20.6mm,
but that's now irrelevant as I fitted a new MC that I bought as NOS from eBay.
Unusually for BMW parts, I can't read any part numbers on it but I can now see that the back section of my current one has a larger external diameter than the front. The front piston drives the real wheel cylinders which are quite small in volume so presumably Dr. BMW decided they needed less fluid than the front disk callipers.(for the same piston travel)
My longer term strategy is to upgrade the back axle brakes to disks (but don't tell my wife ), so I opted for the 22mm bore Sierra MC.
I was close to ordering a Cortina MC with the 20.6 bore but I was concerned that when all four wheels have disk callipers they might need too much pedal travel.

Can you see my logic?
...peter

[Patrick]

Looking good Mike

Originally Posted by peterux

Hi Mike,

OK, no problem. Let me answer your questions and take you through my decision logic. (But only time will tell if I got it right )

My brakes currently are all standard BMW, but I am a little different to most BMW builders as my donor car was only a 2 litre so was fitted with drum brakes at the rear.
According to realoem there are lots of options fitted to these cars with some fitted with dual bore MC's 22,20/17,46MM.....others were fitted with 20.6mm,
but that's now irrelevant as I fitted a new MC that I bought as NOS from eBay.
Unusually for BMW parts, I can't read any part numbers on it but I can now see that the back section of my current one has a larger external diameter than the front. The front piston drives the real wheel cylinders which are quite small in volume so presumably Dr. BMW decided they needed less fluid than the front disk callipers.(for the same piston travel)
My longer term strategy is to upgrade the back axle brakes to disks (but don't tell my wife ), so I opted for the 22mm bore Sierra MC.
I was close to ordering a Cortina MC with the 20.6 bore but I was concerned that when all four wheels have disk callipers they might need too much pedal travel.

Can you see my logic?
...peter

Mine is fitted with a dual bore 22,20/17,46MM and the rear brake (disk) have an extra pressure reduction fitted inline. I just wonder if it will upset the brake balance.

Looks like the 22 might be the better option especially if I swap out the front callipers for something more meaty in future.

[peterux]

Originally Posted by Patrick

Mine is fitted with a dual bore 22,20/17,46MM and the rear brake (disk) have an extra pressure reduction fitted inline. I just wonder if it will upset the brake balance.

Looks like the 22 might be the better option especially if I swap out the front callipers for something more meaty in future.

Yup, mine has the same BMW in-line pressure reducer.
We should be OK as we will have the same config as Jason's car which passed the IVA brake tests with the 22mm master cylinder fitted.