View Full Version : DIY master cylinder movement stop

06-19-2009, 11:23 PM
Yes I know this is on a right hand drive but with a little thought it will work on left hand drive also.

Ok there I was waiting patiently for some company to come out with a master cylinder movement stopper that I could buy in Thailand. I first thought this mod might belong in the mythbuster section but I got out my trusty carpenters square and put it in the engine bay and had Mrs. Claymore step on the brake pedal. Sure enough the master cylinder and the whole metal firewall section it's mounted on moved forward about 5 mm toward the engine bay. So I got tired of waiting and made one myself and it cost the grand total of less than $5.00 US.

Disclaimer: The following is provided as a GUIDE ONLY, and neither myself, nor Honda Fit forums take any responsibility for the outcome of someone else doing the following. You follow these steps at your own risk!

Parts needed: One 2 foot section of metal electricians wire conduit. Two perforated brackets about 1 foot long. One section of threaded rod 20 cm long. One bolt about 3-4 inches long and three nuts to fit bolt. Two or three assorted bolts and some assorted washers. All the above parts can be bought at your local hardware store for less than $5.00 US. If you can't find conduit try a construction job site as pieces 2 feet long are normally thrown away by electricians as they are too short to use or at an electrical supply store but you many have to buy a 6 foot length. Spray paint in the color of your choice is a nice added touch but not absolutely necessary.

Tools needed: A electric grindstone wheel makes things much easier but you could use metal files. Hacksaw, drill and bits, 10 mm wrench and two wrenches that fit the nuts for bolt you bought.

Skill needed: If you took any metal working classes in school or work on your own stuff and can drill holes and file and shape metal you can do this.

Time needed: It took me about an hour to cut and drill the conduit and another 1/2 -1 hour to grind the bolts. But it took two days to do while I painted the finished parts, but your car is not disabled so you can take all the time you need.


Here is a shot of the stuff you need if you never heard of them before.


Here is the cut and modified brackets and conduit ready for paint. You can also see what you need to do to the bolt, grind down the bolt head, and one nut so they slip inside the conduit. Grind the end to a pointed shape.


Here is what you have to do to one end of the lower conduit. Grind or file this shape so the another piece of conduit laid across the top sits square and won't slip off this piece. Conduit is pretty thin soft metal so it is easy to file.


Here is a closer view of how to modify the bolt. This is going to be the part that moves so you can adjust the length of the cylinder stopper.


Here are the finished parts painted and fitted ready to be installed. The lengths are not too important but just starting points that leave enough metal so you can file fit them better when you get going.


This is the "Heart" of this set up. When you look on the left side of engine bay (looking from the front) down near the bottom you will see the big engine mount.

Look to the front of this motor mount and you will see two holes already drilled in the painted part of the frame. The holes already have nuts welded inside so all you need to do is find a bolt that will screw into the hole closest to the engine and take the bolt with you to the hardware store and get a length of threaded rod the same thread and size of the bolt. Then to start everything off cut a length of the rod about 15.5 cm long and screw the cut end into this hole.


This shows a better view of the mount and two holes in the frame. It also shows where to put the washers under the lower piece of conduit with the fish mouthed cut section facing up. You need the washers to raise or lower the conduit so the upper piece "points" straight at the center of the front face of the master cylinder. (more later)


Here is the finished product so you get a better idea of what you are trying to do.

When you screw the threaded rod into the frame hole you will probably think claymore has gone off his rocker as it is very thin and springy and could never stop the master cylinder from moving. Here we go again back to high school physics classes (bet you didn't think you would ever use any of that stuff) and you can strengthen the rod with "Outside support" like the columns in old buildings in Rome. With the section of conduit slipped over the flimsy rod and a nut tightened down pulling up on the rod the conduit pushes down at the same time so the resistance to bending force of the rod, nut, and conduit is much greater than the rod or conduit alone.

In the upper left of the photo is the round end of the upper tube that I have filled with silicone from a tube, inside that end there is a nut that has bigger threads so it slides over the rod without threading it. The reason for the nut inside is to prevent the conduit from squashing down when you tighten the nut on top.

You can see in this photo what you are trying to do, that is trying to "aim" the upper tube like a gun straight at the dimple on the front of the master cylinder when building you just slide a washer on check it then add more until the top piece is level and pointing at the master cylinder.


With the fancy "column" supporting the upper rod up and down I needed to add another brace far from the pivot point of the threaded rod end to prevent lateral movement (sideways) to keep the pointed end of the adjustable bolt from slipping out of the small hole in the face of the master cylinder. So another piece of the perforated bracket material was run to the upper strut tower right next to where you screw in an aftermarket strut bar. Where the new bolt goes is a hole that is already there and just covered with a black plastic pop off cover, pop out this small plastic cover and put the bracket underneath with a nut holding it on.


In this photo you can see that I drilled a small hole for a small bolt for the lateral movement bracket but it was close because the bolt for adjustment is inside the conduit so if I had to do this over again I would just bend the new bracket around the outside of the conduit and secure it with a nut and bolt on the outside rather than drill this hole.

There it is the "Adjuster" the bolt and nut ground down and slid inside the conduit. The ground down section slides inside the conduit and keeps the bolt centered in the conduit. The first nut next to the face of the conduit is tightened so the pointed end of the bolt is forced SLIGHTLY into the hole on the front of the master cylinder but you do not want to over tighten this to the point you damage the master cylinder. I put it finger tight then 1/4 of a turn with a wrench and it doesn't move. Then just hold that nut in position with one wrench and tighten the second nut right up against the first locking them together.

Got the too many images message so will have to split this here.

06-19-2009, 11:24 PM
Part Two


Here is a top view with it all together. The second piece of perforated metal bracket is put going to an original bolt that holds in part of the headlight. Just unscrew the bolt, slide the bracket under the bolt head and screw it back down. The other end is cut and trimmed so one hole goes over the upper tube and onto the threaded rod and the nut is screwed down on top of this bracket that adds to the resistance to movement in the horizontal plane. My fuse box cover is off because with a strut bar installed it got me some added room to get the new bolt for the upper bracket put in place.


There it is finished! It is so small that you can hardly see it if you didn't know it was there. In my "Bad old days" I used to do some illegal street racing and always liked to run "Q" ship type cars that look stock and this mod fits right into that style.

Results: For less than $5.00 US you can build your own master cylinder movement stopper and guess what for me it was free as I already had these parts laying around my "car stuff" from other projects.

This one really works the master cylinder doesn't move at all. It was a bit of a pain because you have to put the pieces on check the fit then take them off and cut a little more several times but I have done that hard work and gave you some measurements to get started.

05-17-2011, 02:55 AM
Was thinking about the differences in GD vs GE since we are getting more and more GEs and it got me wondering. This type mod was very popular on the GDs when they first came out and a couple of parts manufactures have made brackets just to stop master cylinder movement. BUT I have never heard of one for GEs.

So the question is do GEs have movement in the master cylinder/firewall area or did people just forget about this type mod? Has anyone checked a GE and see if the master cylinder is moving?