MG Sports Cars

Thought you might be interested in seeing what I've done to switch to a dual brake system in my '67. When I built this project I put a lot of time (some would say too much time!) in the brakes. 12.19" solid discs in the rear and 12.19" vented discs in the front all with Wilwood Dynalite calipers. Theses are some serious big brakes. But almost anything we do that involves changing axles or front suspensions results in some sort of brake bias change. I had gotten around my changes with a brake proportioning valve but the results were not what I wanted. For example I could set the valve to give me proper bias under strong braking, but due to the nature of the proportioning valve, I was still over braked on the rear axle under slight to moderate braking; the rear discs were designed to stop a bigger car. I felt the best system would allow me to set the bias as needed. After looking at the archives, I found several dual master cylinder set-ups using a balance bar that seemed to fit the bill. Of course I always have to do things the hard way and I decided to see if I could set-up my Tilton balance bar in the stock MGB brake/clutch pedestal. Here are some pictures of the result:

this picture shows the placement to the three cylinders in the widened body of the the brake tower



this shows the completed installation with remote master cylinder reservoirs. The larger is a dual reservoir from a Mitsubishi and the smaller is the clutch master cylinder reservoir from a Honda Civic.

I re-plumbed the the front brake lines to get them away from exhaust and used AN fittings with stainless steel brake lines. I finished the project today, bled the lines and test drove the car. I am very pleased with the results so far and am looking forward to tuning the bias as soon as the salt is off the streets.....cj



Edited 1 time(s). Last edit at 02/27/2009 10:27AM by 67MGBV8.

Chris,

I am contemplating this mod too. Good looking execution -- well done!

Do you have pics of the modification of the brake tower in progress? I assume you kept the pedals in the relative position and offset the master cylinters to each side, correct?

What master cylinder bore sizes did you choose?

Where did you set up your proportioning valve (within reach in the cockpit)?

Thanks,

Johnny

Oh, I just took a look at your "How it was done" photos and I see you have the proportioning valve on the underside of the dash on the passenger side. Looks like lots of neat aluminum fabrication you've done.

Here's another for you to consider:









Done 30 years back, it isn't as slick as the ones done using store bought parts, and not as slick as something I'd do today either, but it has worked well. The screw is a 1/2" hardened square headed jackscrew, much tougher and more resistant to bending than what is more readily available, but also capable of being broken, though I can't see how that would be possible in this application. But, if it was screwed into a 1" thick steel deck and you nailed it sideways with the full swing of a 10 lb sledge hammer I think you just might be able to snap it off if you hit it hard enough. I haven't tried it. I managed to bend 1/2" all-thread before I fitted this screw. Probably the sensible piece would be grade 8 if you could find something suitable, as it would definitely bend before breaking. The jackscrew is probably grade 11 or higher. I slitted a 1/2" nut and turned it for a press fit into the inner race of a spherical bearing with a slight lip on one side. This was positioned on the screw with stud-lock and the bearing was then pressed over it, locking the assembly in place. A 9/16" 1/2" drive socket was then pinned to the head and a flex drive terminated by a 9/16" fitting slips into the socket when the cover is attached. The flex drive terminates in a large walnut knob on the dashboard.

I find that just a turn or so will tune the brakes between wet or dry road conditions. It also helps greatly when upgrading the brakes by making it easier to maintain balance.

Jim

Johnny, The pedals come through the firewall in the original locations, and bolt to the pedal box as in the original. The clutch pedal arm was bent about 1/2" to the left to align with the offset cylinder and the brake pedal arm is modified by welding the Tilton balance bar sleeve centered on the arm. This location allows the two brake cylinders, spaced 2.5" apart to fit in the widened housing. I had a proportioning valve but have removed it because it will not be needed to balance the system. The rear master cylinder is 3/4" and the front is 5/8". Master cylinder size will be dictated by the brake slave cylinders you are using.

perhaps these pictures will show this.



rear view showing spacing of cylinders. box measures 7"x3"x 1.5" deep. note that only the clutch pushrod has clearance to go through the box.


front view showing how cylinders mount in modified box


photo showing how modified box is attached to pedal mount


photo showing how the cover was modified. slot allows balance to be adjusted (a portion of this has been opened up to allow the tightening of the lock nut) slot will be covered with vinyl tape once proper bias has been set.

As usual, your work is really exceptional Chris! Very, very well done.

---

I think this is a bit simpler though: standard "long" Wilwood pedals, installed on a raised platform...

(A detailed article on this MGB GT V8 racecar is coming soon!)

That's nice Curtis, but if you don't want to tear down your car to weld up the support box Chris' and Jim's solutions look like a good way to go. I just got a spare pedal assembly for my Midget and will be starting to fab up a similar pedal arrangment for it this spring. Trying to copy this race car setup I found on line that bolts into the stock location.





Edited 1 time(s). Last edit at 02/25/2009 04:52PM by Bill Young.

Good point, Bill, about being able to do this without cutting and welding the firewall. I notice Jim's modification to fit three Lockheed cylinders in requires the the bonnet hinge be cut out! There is just not much room in that little space, and I got it done by pushing the clutch and one brake cylinder as close together as possible and by using remote fluid reservoirs. I tuned the pedals to hung in just about the stock locations and have pretty much a stock feel to them. Here's a picture with the cover in place taken on the day I test drove last Sunday.




Edited 1 time(s). Last edit at 02/26/2009 09:35AM by 67MGBV8.

That's not entirely accurate Chris. The bonnet hinge remains perfectly usable as are all three attachment points and I did in fact use it at one point in between forward tilt bonnets when I temporarily went back to a stock hood. The sheet metal that is trimmed out at the bottom right of the hinge opening allows space for the extra cylinder but without affecting the bonnet.

I like your system and didn't mean to imply otherwise. Although I managed to retain the stock (or near stock) master cylinders, you have a more compact arrangement, partly because it does not use discrete pivots for each M/C, but mainly because of the smaller cross bar and related parts. Use of a 3/8 bar and fine threads instead of 1/2" and coarse threads means that the threaded pivots can be between 1/2" and 5/8" diameter rather than 1" as I used and the yokes they turn in can be about 3/4" wide instead of 1-1/4". That saves at least a half inch on the width and there are ways to save even more right in that location. In addition, a smaller diameter cross bar means a smaller spherical bearing can be used for the same limits of angular misalignment and the whole thing becomes more compact. In fact, it wouldn't be all that difficult to incorporate the advantages of both systems and end up with a very compact package using the Girling cylinders. You might even move the clutch M/C over a bit by moving the side panel out and reversing the foot, but I don't know if it could be made to fit into the stock space without trimming sheet metal or not. Might be possible though.

Jim

Jim,

Sometime when we get together I would like to pursue this type of mod to the TR4A, for safety's sake as much as anything else. Of course it is a little different than the B. There is probably a little more room there.

Dan

No problem, dig out your spare parts and we'll have a go at it.

Jim

Jim, no offense taken and no offense intended. This is the type of mod that I think we will see more of because almost every power upgrade these days is using a different axle/brake set-up. Brake bias is such an important aspect of enjoying the performance of these cars, not to mention safety. You mentioned moving the clutch master cylinder over. I did move the cylinder about 1/2" to the left side. Perhaps it doesn't show too well in the photo, but if you look closely you'll see the dogleg bent into the upper arm of the clutch pedal. This effectively shortens the arm slightly, and could be compensated for by lowering the cylinder mounting point. I added weld metal to the top of the arm and re-drilled the pivot pin hole. Another factor in my mod was that I wanted to use the same bolt holes that come through the firewall to mount the back of the pedal box, so the total width of the cylinder spacing is limited by the fact that the arms are bent back in on each side so as to align with the original holes. One could mount the Girling cylinders a little closer together by sawing off the side of the mounting flanges, but I found I could get everything to fit. Other nice cylinder options that might work better are the compact Tilton series 75 and the AP racing cylinders (both with remote reservoirs) , the downside of these cylinders is the price! I think this picture shows the clutch pedal modification a little more clearly:

Chris, I did notice the bow in the side, but didn't catch the dogleg in the clutch arm. Do you think we could get another half inch out of it by bending the feet back the other way on that side? Just on the M/C side of the mount. The shorter arm length might be offset with a 1/16" increase in cylinder diameter if needed as long as alignment was OK. Or welded up and redrilled as you did. That would add up to close to 1-1/2" all together and just might eliminate the need to cut sheet metal. If more compactness is needed I have a couple of other ideas on how we could get it.

I also used the original bolt holes, but added an extra outside bracket. It's not really needed, especially if the discrete arm pivots aren't used, or if just one is used to the inside for stability. I think up-down movement may need to be controlled if a remote cable is attached, but maybe not. Most of the cutting was done to give clearance for the firewall tab on the extra side bracket. The extra bracket also made the mounting a little more rigid but I'm not sure if you'd be able to feel the difference. It doesn't give a bit though.

Although they are a pain to change out, not particularly convenient to fill, and sometimes hard to find in the right configuration and bore size I do still like the Girling cylinders better than remote units. They too have gotten a bit expensive, but not what the Tilton and such cost I'm sure.

Jim

Jim, get ready for a shock. Those Girling's aren't cheap. Pegasus lists the Girling with integral resevoir at 98.99 and the remote resevoir version at $84. Tilton cylinders which can be either integral or remote resevoir are listed at $79 and the compact version at $98. Speedway shows "US Brake" master cylinders at $55 and Wilwood with integral resevoirs at $58 and universals at $67. For my application I think I'll go with the Wilwood universals.

Jim, I'm not sure I catch your drift. Do you mean can we get another 1/2" on the clutch side in order to use cylinders with integral reservoirs? Perhaps that would work, but i found that the size of the firewall indention pretty much keeps us from using 3 each integral reservoirs in that area. One thing I didn't do was look at keeping the cylinders in the same plane as the original Lockheed cylinders. I moved everything back about a inch and a half so that the push-rod length would stay pretty much as supplied by Girling. Once you move the cylinders back to the firewall by 1.5" forget about filling a reservoir that close to the firewall. That little pocket just gets shorter and shorter as you go aft. The sweetest looking option to me was the AP Racing cylinders, but they were pricey!



Edited 1 time(s). Last edit at 02/26/2009 10:31PM by 67MGBV8.

Keeping the integral reservoirs was what I was after, whether Girling, Tilton or whoever. Obviously lower cost is better. Only thing is, the less aftermarket parts are used the easier it usually is to track down replacements in ten years when they are needed. Even with that, I've had several different varieties of cylinders on mine. For example look at the angled mounts on two of them. They used at least 3 different angles. Vertical, and for some odd reason just shy of vertical which makes one of those look weird. None of the ones in the photo are the right one. The distance back to the reservoir varied, and last time I bought one it used a clamp on plastic reservoir which was too big and had to be heated and dimpled in. But nowadays I'm pretty optimistic that the right ones are probably stocked by Moss and others. Getting the exact same thing in a different bore size could be a challenge though.

I kept the original mounting plane and the original push rod. That meant the pivot assembly had to be further forward and because of the size of the components I had to put a bulge in the cover. I think that could be avoided though with the smaller parts, the rods could be shortened slightly, and with those steps maybe we could keep the original mounting plane. I don't know. But I'll try to look at it again later today.

Jim

Integral resevoirs make sense for a MGB where the cylinders are level, but on a Midget they angle upwards and you lose effective resevoir volumn with the integral ones. After looking at both of your setups I'm going to try to move the three cylinders a bit towards the center of the car compared to the setup I posted the photo of, I need the clearance on the outside for the throttle cable and windshield wiper cable. I can go probably about 1/2 to 3/4" to both sides and fit everything in I think and still access the mounting bolts. Hopefullly I can get it done before June, but if not it can wait a bit.