Changing to a 15/16 BMC. Rod length question???

[ZSaint]

I am installing 4-wheel disc brakes and a ZX 15/16 M/C. I have done the brake line switch, F/R. Here is my concern... I am concerned that the rod receiver hole is 1/4" deeper in the master cylinder than my stock 7/8" M/C. Has anyone done this switch and had problems with this additional rod length? Do I need a longer rod out of the booster to make up the difference in the depth of the rod in the M/C? I have a different booster rod from a ZX. Can I use that rod with my later model M/C and the '71 240 booster? I have done the search but no one speaks about this particular problem.

[LanceM]

I did the change on my 73 and had no problems with the 73 rod.

[ZSaint]

Thanks for this info. I will try it and see how it works. I am guessing the pedal ratio is fairly substantial so 1/4" will make a couple of inches in stroke difference. Maybe it will sort itself out with the new M/C.

[kinfish]

The rod between the brake booster and master cylinder interface should be adjustable and set so there is a small gap (.000 to .032) in the free state. If the gap is too big you will be consuming brake pedal movement to close the gap before the pistion in the master cylinder starts moving. Result is less than optimum brake system

I replaced the brake booster on my '71 240Z and the new rod was significantly longer than my original rod and could not be adjusted to achieve the desired gap. I fixed the issue by using the original rod with new booster.

[cj71z]

I swapped by brakes for the Toy 4 pots and the 15/16 master since my stock one was bad anyway. I first installed the master with no adjustment to the pushrod length. After I bled the system for an hour I still had no pedal so I adjusted the pushrod length about 1/8 inch or so. I thought this would be enough, but I still had a soft pedal and my brakes engaged low. Yesterday I adjusted the pushrod nearly another 1/4 inch, put it together and now my brakes are firm. My pushrod is nearly adjusted all the way out now, I thought it would be too much, but it seems to work great.

[ChrisA]

The rod between the brake booster and master cylinder interface should be adjustable and set so there is a small gap (.000 to .032) in the free state. If the gap is too big you will be consuming brake pedal movement to close the gap before the pistion in the master cylinder starts moving. Result is less than optimum brake system

I replaced the brake booster on my '71 240Z and the new rod was significantly longer than my original rod and could not be adjusted to achieve the desired gap. I fixed the issue by using the original rod with new booster.

Hi Ron, can you tell me what booster you went with? For my future reference.

Thanks,

Chris

[ZSaint]

I am still a few weeks from getting the engine finished. I still do not have S/S brake lines installed. I will use this info when I start bleeding the brakes. It sounds like there will be a problem. (I am using the stock booster, FYI.)