17 replies to this topic

[normini]

I shall change the brake system from diagonal split to front/rear split. The diagonal split system use MC GMC160, the front rear split system use GMC159. Both use the same repair set. What is the difference between the two master cylinders? I have GMC160. Do I need GMC159, or are thy interchangeable?

[Spider]

I think you'll find the only difference between these is one has Imperial Threads for the Tube Nuts and the other is Metric.

[normini]

In the link below, I found this:

". . . The same main casting was used on the GMC159 and GMC160 diagonal split master cylinder, so, externally, one can't tell the two versions apart. There are slight internal differences, such as one piston is slightly different, so these are not interchangeable with the GMC159, . . . ."

https://www.7ent.com...r-cylinder.html

 

On a German site I found an other explanation and a drawing.

https://www.mini-for...934-Inno-GMC159

 

It says that the part no. 15 should be removed from the lower position/front system to convert GMC160 to GMC159.

I am confused and would like to know what is correct.

In Norway I can get hold of used GMC160s, but GMC159 is hard to find I recon.

[Ethel]

Could be a residual pressure valve to reduce pedal travel by keeping the brakes from backing off fully. That wouldn't be very desirable on only one front brake in a diagonal split system!

[Spider]

Could be a residual pressure valve to reduce pedal travel by keeping the brakes from backing off fully. That wouldn't be very desirable on only one front brake in a diagonal split system!

 

The scant bit of info I have on these Cylinders suggests that there's a residual pressure valve, referred to as a 'trap' under both outlets on the front / rear split cylinder.

<Edit:- in the last year of production, the threads in these did change from Imperial to Metric, but, it appears that it was just the adaptors near item 15, that were changed. >

Edited by Moke Spider, 21 May 2020 - 08:57 PM.

[Ethel]

Interesting, wonder if that was just an Ozzie thing. I think they were careful with hydraulics here not to make anything metric that could accidentally be used to replace a superseded imperial component. 

[Spider]

Interesting, wonder if that was just an Ozzie thing. I think they were careful with hydraulics here not to make anything metric that could accidentally be used to replace a superseded imperial component. 

 

No, it was a UK-ish thing. We never had these Cylinders here, though, a very small few found their way on to Race Car to meet the regs of the day. There was a reference to the change in the threads on a fiche.

 

I agree with what you are saying re thread confusion, however the GMC 167 was fitted for front / rear split and GMC168 for diagonal spit however, the only difference between these cylinder is that the 167 has metric threads and the 168 imperial.

[croc7]

In the link below, I found this:
". . .

The same main casting was used on the GMC159 and GMC160 diagonal split master cylinder, so, externally, one can't tell the two versions apart. There are slight internal differences, such as one piston is slightly different, so these are not interchangeable with the GMC159, . . . ."

https://www.7ent.com...r-cylinder.html

On a German site I found an other explanation and a drawing.

https://www.mini-for...934-Inno-GMC159

It says that the part no. 15 should be removed from the lower position/front system to convert GMC160 to GMC159.

I am confused and would like to know what is correct.

In Norway I can get hold of used GMC160s, but GMC159 is hard to find I recon.

[croc7]

I have a GMC159 rebuilt and preserved with Castrol Red Rubber Grease if you are interested.

[normini]

I have a GMC159 rebuilt and preserved with Castrol Red Rubber Grease if you are interested.

PM sendt.

[normini]

My master cylinder, GMC160:

 Målsatt GMC160.JPG   31.33K   7 downloads

 Målsatt UNF.JPG   36.87K   6 downloads

 Målsatt pushrod.JPG   27.63K   8 downloads

 Målsatte stempler.JPG   42.21K   7 downloads

[normini]

I have got an other master cylinder. I am not sure if this could be a GMC159. The upper piston and the spring are different from my GMC160. The right piston and spring are fro my GMC160, for the diagonal split brake system. Could the left piston be GMC159 for the front/rear split system. It will be nice if someone can conclude on this subject.

The cylinders, lower pistons and piston linkages are equal.

 

 

 Upper pistons.JPG   25.49K   18 downloads

 

[Spider]

Just looking at the 2 pistons here, it appears that when fitted, the seals between the 2 types will 'park' at different heights within the cylinder - Am I seeing that right?

If that's the case, then I'm sure the ports between the cylinder and the Reservoir would also be at different heights too.

[normini]

The cylinder outlets and reservoir ports are equal.

Could it be that the rear slave cylinders will require less brake fluid than the front slave cylinders?

In a diagonal split system, fluid requirements will be equal for both systems.

[croc7]

Could be a residual pressure valve to reduce pedal travel by keeping the brakes from backing off fully. That wouldn't be very desirable on only one front brake in a diagonal split system!

The scant bit of info I have on these Cylinders suggests that there's a residual pressure valve, referred to as a 'trap' under both outlets on the front / rear split cylinder.

<Edit:- in the last year of production, the threads in these did change from Imperial to Metric, but, it appears that it was just the adaptors near item 15, that were changed. >