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914World.com _ 914World Garage _ Brake Master Cylinder Flex
Posted by: McMark Apr 7 2010, 10:33 AM
https://www.youtube.com/watch?v=CUdPmitJ9XQ
Took this video to post in my "Hold the phone!" build thread, but for those who might miss it, this is a repost.
Posted by: ConeDodger Apr 7 2010, 10:42 AM
Holy Moly! Don't we have a member vendor that has a weld in and bolt in brace?
Posted by: Racer Chris Apr 7 2010, 10:51 AM
I think I read that the bolt-in brace is no longer being made.
Some lucky WCR attendee may be receiving one of the weld-in braces though.
Posted by: rick 918-S Apr 7 2010, 10:57 AM
Fix your floor pan. It's cracked around the brace. Oh, then add the brace.
Posted by: McMark Apr 7 2010, 11:07 AM
Eh? 
I didn't see no cracking. 
Posted by: underthetire Apr 7 2010, 11:10 AM
Holly crap ! Think i'll make a support after seeing that.
Posted by: Root_Werks Apr 7 2010, 11:14 AM
Posted by: rick 918-S Apr 7 2010, 11:19 AM
Eh?
I didn't see no cracking.
Look around the curve of the brace as the master flexes. The brace is stable and the pan moves. I think I can even see light around it. I could be wrong...
Posted by: SirAndy Apr 7 2010, 11:20 AM
you'll be surprised
Nope ... I've seen this many times. They all flex.
Back in the old days, people welded a boxed section around the back of the mounting area.
Lots of work and ugly, but effective.
The clamp-on solution worked, but didn't seem 'right'.
I've been thinking about welding a tab on the steel cross-member that would allow you to bolt on a support bracket under the MC.
That way, if you need to replace the MC, you can just unbolt the bracket.
![popcorn[1].gif](style_emoticons/default/popcorn[1].gif)
Andy
Posted by: SirAndy Apr 7 2010, 11:22 AM
Look around the curve of the brace as the master flexes. The brace is stable and the pan moves. I think I can even see light around it. I could be wrong...
The metal flexes, but not because it's cracked. It's just a single layer of sheet-metal that will bend every time you hit the brakes.
All stock 914s do that ...
Andy
Posted by: ericread Apr 7 2010, 11:28 AM
There was also a bolt-on brace offered previously (I have no welding skills/eqiuipment). I have looked around but I cannot find it for sale anywhere. If anyone wants to make one, I'm first in line to purchase.
Eric
Posted by: McMark Apr 7 2010, 12:25 PM
Rick, the factory bracing/box which is under the pedal assembly is open on the forward face. That crack you're seeing is just how it is.
This is the 'repair' that I've seen done by another 914 guy. Weld a nut to the cross member and thread a bolt against the MC to brace it. It helps, but not as much as I would like. Time to try something else.
https://www.youtube.com/watch?v=d02D8jRn7T0
Posted by: McMark Apr 7 2010, 03:01 PM
Well, here's what it took to get it immobile. A sturdy brace in the vertical direction via a bar that bolts to the MC mount studs at one end and to a welded nut on the cross member. But this brace still moved forward and back, so I had to bring my original 'fix' back into contact with the MC to restrict horizontal movement. The other modifications I tried, still allowed some movement at the MC and didn't feel much more firm at the pedal. After getting this all done, the difference would pronounced at the pedal.
This is all rather ugly, so now I'll go back and replace everything with a cleaner, prettier setup.
https://www.youtube.com/watch?v=iIvAyozXx4Y
Posted by: rick 918-S Apr 7 2010, 03:09 PM
Ya, I know the brace is open. I was looking at the stamped edge. Must be the lighting. Glad it's not cracked. Your brace is working well.
Posted by: McMark Apr 7 2010, 03:11 PM
There is one of those U-slits under the pedal cluster. You know, the ones that are all over the floor pan. So there is light coming through there, but it's not rust or cracking. It's just factory holes. 
Attached image(s)
Posted by: Root_Werks Apr 7 2010, 03:16 PM
That's a good fix!
When mine's up in the air, I'll do something similar for sure.
Posted by: rick 918-S Apr 7 2010, 04:15 PM
There is one of those U-slits under the pedal cluster. You know, the ones that are all over the floor pan. So there is light coming through there, but it's not rust or cracking. It's just factory holes.
OH! I knew I saw light! That's right! Anywho... Nice brace!
Posted by: veltror Apr 7 2010, 04:15 PM
My floor is rotten so Marek is making up a triple skinned piece as in my thread...
Posted by: brant Apr 7 2010, 07:15 PM
fixing the flex is a good thing
it will help firm up the "feel"
we did this on our old car about 15 years ago
and on the new one when we built it 6 years ago also
here is the new ones method with lightening holes:
Attached thumbnail(s)
Posted by: brant Apr 7 2010, 07:16 PM
and:
Attached thumbnail(s)
Posted by: Racer Chris Apr 7 2010, 07:35 PM
Posted by: McMark Apr 7 2010, 08:29 PM
Chris, how do you change the MC?
Posted by: Racer Chris Apr 7 2010, 08:50 PM
Posted by: Racer Chris Apr 7 2010, 08:51 PM
Actually, the pictures are of a prototype.
We added a little lip on the angle iron piece that prevents the MC from moving downwards under braking pressure.
Posted by: PRS914-6 Apr 7 2010, 09:02 PM
Here is my installation with a hydraulic clutch. It is quite simple to add some reinforcing with some scrap metal. It is attached to the suspension beam. Note the plate under both cylinders that is flanged.
Posted by: McMark Apr 7 2010, 09:15 PM
AHA! Chris, you were hiding the details from me! 
That's much better than what I did. 
I'll have to order one and swap in another cross beam.
I was wondering about that, but didn't want to offend.
Posted by: realred914 Apr 7 2010, 09:22 PM
you'll be surprised
Nope ... I've seen this many times. They all flex.
Back in the old days, people welded a boxed section around the back of the mounting area.
Lots of work and ugly, but effective.
The clamp-on solution worked, but didn't seem 'right'.
I've been thinking about welding a tab on the steel cross-member that would allow you to bolt on a support bracket under the MC.
That way, if you need to replace the MC, you can just unbolt the bracket.
Andyandy whats the clamp on solution look like, no welding needed at all would be nice!
Posted by: Eric_Shea Apr 8 2010, 08:50 PM
Mr. Burton and I have them on our cars. Chris makes the best set-up (as usual):
Posted by: rdauenhauer Apr 9 2010, 01:22 AM
Chris do you have a similar solution for those running an aluminum x-member?
Posted by: Racer Chris Apr 9 2010, 05:29 AM
Chris do you have a similar solution for those running an aluminum x-member?
I looked at it briefly but didn't come up with a good solution.
I don't consider the aluminum crossmember to be an upgrade so I doubt I'll ever install one.
Posted by: pcar916 Apr 9 2010, 06:10 AM
Obviously for those with big-brakes only, the Mercedes 23mm cylinder butts up the the stock crossmember.
It was slightly long, but all I had to do was grind off a bit from the end of the MC and add a thin, stiff plastic sheath around the cross-member and it was done. This is better, no movement at all. I've never looked at it's flex directly but it's GOT to be moving a little. Time for an inspection.
I'll climb under the car sooner than expected and check for wear.
Posted by: 396 Apr 9 2010, 08:17 AM
Obviously for those with big-brakes only, the Mercedes 23mm cylinder butts up the the stock crossmember.
It was slightly long, but all I had to do was grind off a bit from the end of the MC and add a thin, stiff plastic sheath around the cross-member and it was done. This is better, no movement at all. I've never looked at it's flex directly but it's GOT to be moving a little. Time for an inspection.
I'll climb under the car sooner than expected and check for wear.
Can you please post a picture so we can 'see' exactly what your referring too?
Thank you!
Posted by: realred914 Apr 9 2010, 10:43 AM
Mr. Burton and I have them on our cars. Chris makes the best set-up (as usual):
is the stud supposed to be crooked? looks that way in the photo?
anyone know whats up with the clamp on support andy mentioned? whats that like?
also how much foor pressure was required to get teh movement seem in the movie? was it a full force thing with you leg or a lesser force?
I guess if I was racing , the car would get a lot of full force breaking stops, but on regular street use, full force braking is not frequent.
does this failure happen often on street cazrs, or is this mainly a track/race car issue?
Posted by: SirAndy Apr 9 2010, 10:47 AM
does this failure happen often on street cazrs, or is this mainly a track/race car issue?
It's not a failure. All stock 914s do that.
As for the clamp on solution, it's been a while since i've seen the posts (several years?) but they are here somewhere.
Basically, it's a metal brace that is clamped to the cross-member and MC holding the MC in place.
Andy
Posted by: ConeDodger Apr 9 2010, 10:50 AM
The clamp on and weld on solution was made by one of our Member Vendors. You can cruise that forum and find it. This is what was used on the Grassroots Motorsports 914 Project car. I suspect that the member vendor no longer makes this since he has not spoken up.
Some level of this is happening all the time with every brake effort.
Posted by: realred914 Apr 9 2010, 10:52 AM
The clamp on and weld on solution was made by one of our Member Vendors. You can cruise that forum and find it. This is what was used on the Grassroots Motorsports 914 Project car. I suspect that the member vendor no longer makes this since he has not spoken up.
Some level of this is happening all the time with every brake effort.
thanks, I cuse I need to get mine and my friends cars checked on teh flex and any cracks.
a clamp on soulution would be nice, I got to take a look into that!
Posted by: pcar916 Apr 9 2010, 12:19 PM
I'll climb under the car sooner than expected and check for wear.
Can you please post a picture so we can 'see' exactly what your referring too?
Thank you!
Glad to. It'll be a couple of days but I'll post it when I get it!!
Posted by: Eric_Shea Apr 9 2010, 12:33 PM
Yes.
Posted by: d914 Apr 9 2010, 01:26 PM
I have a clamp version I will not be using.. I have to put another master in for the clutch so we'll weld something up or get chris's set up..
Posted by: Travis Neff Apr 9 2010, 02:22 PM
I used to make the clamp in units a while back.
Posted by: ericread Apr 11 2010, 08:44 PM
So is anybody out there going to make a bolt-on brace? I'm in for one when you do...
Eric Read
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