I have designed rear disc brakes for my 74 MGB. I'm not new to this so I know the benefits and pitfalls of rear disc brakes. My question here is about the master cylinder. Does the check valve for the rear circuit need to be removed on from the stock MGB master cylinder? I have everything mocked up to my satisfaction, just need to address the M/C before I install everything on the car..
On some of my conversions on other cars I did have to remove the internal check valve and then replace it with a 2psi external valve, on other MG's I could leave it in. I did do a research on rear disc conversions and have not found any mention about the M/C internal check valves in a MGB M/C.
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I don't think the MGB master has a residual check valve. People have had trouble with the brass H where the lines meet. I would do away with that and separate front and rear. I do like the aftermarket 2lb residual valves for disk brakes.
Seems to me the '74 had the MC with the big round cap. Later MCs had the rectangular reservoir and there was a built-in brake balance switch. Not sure about any check valves though.
Jim
Yep, My M/C has the round cap. The parts breakdown for the M/C does show check valves in the ports. I just can't find the values for those valves. I'm going to try it without mods and if I need to remove them, add 2lb inline valves. The valve in question is item 21. Since both are the same part number in the Moss catalog I doubt they are more than 2lb.
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Sounds to me like a good approach.
Jim
Started the install over the weekend and then it stalled out. Thought I had wheel seals and the discovered I only had one. Only got the right side done. Oh well something to do next weekend.
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Looking good Charles. Nice work.
Thanks, hope to get back on it tomorrow afternoon or Sunday afternoon.
Took the GT for a spirited test spin today. The brakes have a good firm pedal. Temps are 190 front 130 rear. I really dislike the Wagner PD900 pads. The box says ceramic but the pads feel and look like metallic. They squeal even when just driving down the road. I'm going to try something else next weekend. The rear brakes do not lock up first.
I need to make some adjustments with the park brake cables. That will be simple enough to rectify.
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Excellent work Charlie!
Found the noise. The anti-rattle shims that come with the PD900 pads were the cause of all of the ills. I rounded up another set that are a different shape and now the irritating racket is gone. The new shims hold the pads more securely. Rotor temps today were 90 rear and 160 front. The stops are straight and no surpries during vigorous brake application while turning.
When I get a chance I may experiment with some 38MM 240SX calipers that I have. That will be for another time.
I'm happy now.
1st 2 pics are the troublesome shims
last 2 are the good shims
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troublesome1.jpg
goodshim.jpg
good1.jpg
Cool! But, where in the world were you able to get just the anti-rattle shims? I've never seen them sold separate from the calipers or pads.
The hardware can be had at Rockauto and I'm sure at NAPA
http://www.rockauto.com/en/catalog/nissan,2002,sentra,2.5l+l4,1388112,brake+&+wheel+hub,disc+brake+hardware+kit,1736
In my case one set came with the calipers and the other with the pads
The next challenge is one of the reman calipers has inop park brake. Discovered the problem when I raised the car to check things over. With the park brake set the right was applied solidly, the left not. I want to see if I can discover the problem with the left side before I move on.
While fiddling today I made a proof of concept mounting for a 38MM 1998 Nissan 240SX rear caliper. The 240sx caliper requires a different offset for the axle bracket. I was able to make a simple 4 hole bracket attached to the bracket for the Sentra caliper. The alignment is good and it uses the same rotor. Basically it's 4 10mm holes spaced 115MM x 29mm with a cut out to clear the 240sx caliper cylinder.
The 38mm will give more bias to the rear at the expense of a little more pedal travel.
I decided to draw up the adapter. I'll make a template out of steel this weekend and give it a test fit on the car.
The adapter provides the required additional offset and move the the 240sx mount holes out for alignment with the existing rotor. I did add an additional hole that attaches to a nearby bolt for strength.
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I've had several folks ask about the change I'll be making to the Sentra caliper adapter bracket. I have attached a pic with some hand written notes. The changes are small. The bracket works well as is. The changes are just to clean up some details.
drawingchanges.jpg
Hi Charlie,
What details need to be cleaned up?
Scott,
Double click on the drawing and you will see my hand written notes.
I now have a CAD drawing for the bracket for mounting the 2002 Nissan Sentra caliper to the tube type MGB rear axle. It will require a CAD viewer to see. The .dwg file can be converted to what ever file system is used for the cutter. Also there is a .jpg file. I have not had this part cut as I am satisfied with the original drawing. This drawing is modified to "square up" the caliper as it sits over the OD of the rotor. The top yellow line was maintained at 115MM. The lower yellow line was extended to 3 11/16". Have your machinist confirm those dimensions before cutting. All else remained the same. When I get time I will experiment with adapting the 1998 240SX rear caliper using the "U" shaped bracket above. That additional bracket provides the correct offset for the 240SX caliper.
Unfortunately I was not able to attach the .dwg file. Just e-mail me with your e-mail address and I'll send out the file.
CHARLIEPART5Dec23003.Layout1.jpg
I found a problem with the latest drawing. The hole where the 2 yellow lines intersect is still out of place. I'll see if I can get it redrawn.
The additional bracket for the 240sx caliper has to be changed. The difference is the spacing as shown in the pic. That spacing will also change on the Sentra bracket.
Yesterday I got a chance to make the adapter brackets for the 240sx calipers. Those brackets move the mount holes out and provide the necessary offset. As a precaution, I bolted and welded the 2 brackets together.
I took the GT out for a vigorous test drive with the 38mm bore 240SX rear calipers. The stopping is satisfying, Very little nose dive. almost flat. In checking the temps front to rear and they we within a couple of degrees front to rear. We had a steady rain all day yesterday so there were still patches of wet asphalt. The car braked well on both wet and dry pavement. In places where the pavement alternated between wet and dry the car behaved predictably. I even tried hard braking on a curve both wet and dry and the car behaved. No surprises. I had a buddy with me who has a stock1972 roadster. His gut feeling is the 38mm calipers may give a roadster a little too much rear bias. We'll try the 34mm Sentra calipers on his car sometime in the future.
The 240SX provides for a better routing for the hydraulic hose and the park brake cable, in my opinion. I did have to make a simple modification to the park brake lever by welding a small piece of metal to close off the open hook for the brake cable. That may not be necessary, I just wanted to be assured the cable end could not fall off the arm.
The Sentra 34mm calipers have some benefits in that the pads are longer than the 240sx pads. As I understand it longer pads may not give more stopping power but may have an advantage of lasting longer and operate cooler. The other benefit is the bracket is one piece. The disadvantage is the park brake lever has to be modified and the park brake cable ends up being very close to the boot bodywork.
The benefit for the 240sx caliper is the brake hose port is in a place for better routing of the hose and the park brake cable is in a better location. The disadvantage is the 2 piece bracket and the brake hose routing I used is close to a mount bolt which means the brake hose will have to be removed to change pads. There may be a workaround for that issue.
I had to remove the squealer from the inside pads because of interference with the adapter bracket I made. The bracket could be modified easily.
In the end, I like the 240sx calipers for the GT and the jury is out about those calipers on the roadster without adding a porp. valve.
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IMO, the wet pavement brake test should have shown if there was too much rear bias.
Hi Charlie,
For the Sentra 34mm calipers, you mention they are close to the body work. Would clocking the caliper at a different angle help with that? Nothing you mentioned about either caliper sounds like a show stopper though.
Thanks for keeping us informed. Great job!!
Scott
Scott,
The caliper is not close to the body work it's the park brake cable on the right side. In reality it just rubbed so all I needed was a little more clearance. I solved that problem with drilling another hole in the lever on the caliper. That brought the cable in enough to clear the boot floor.
It's suppose to rain this weekend so I'll take the GT out and see how the brakes react in the rain. We have some smooth roads out in the toolies so I can give it a brake test in the wet and on a curve. That should show any glaring balance issues.
I am having the drawing corrected so a laser cutter can cut out the bracket with the one stray hole in the right place. It would also be easy enough to make one from some 3/8 flat stock if you so choose.
I'll see if I can post a pick of the redrilled lever this weekend.
Attached is a pic of the shortened lever. That provided enough clearance for the park brake cable. I did notice that the caliper does get close to the body in full compression. I did not find any evidence of the caliper contacting the body, however I did take the time to bend over the lip for additional clearance. If you choose to rotate the caliper down a bit that can be done with the Sentra caliper but not with the 240SX caliper. There is a clearance issue with the extension strap mount on the axle with the 240SX caliper.
Another change. I will change the flex hose to a shorter hose. 12 or 13 inches long should clean that up.
I did find a defective 240SX caliper. That is now changed out for another reman caliper. I took a vigorous test drive today and the temps are 145 degrees for both rears and 265 for both fronts. That coincides with the predicted brake balance of 67-33. It's raining now so I should be able to take it for a wet test drive in the morning.
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Unfortunately the streets were dry on Sunday. It may rain later this week so I'll give it another try then.
OK I'm happy with my rear disc brake conversion. Bob Harper in Australia was kind enough to correct the drawing for the Sentra/Sunny caliper bracket. The drawing has been checked and to the best of my knowledge it is correct. The dimensions have been changed to make it easier to layout on a piece of steel or aluminum with easy to locate reference points. I'm not going to develop this conversion any farther.
If anyone wants the drawing for the caliper bracket send me a PM with your e-mail address and I'll send the drawing along with part numbers for the caliper and rotors that I have used. As far as the additional bracket for the 240SX is concerned, it is easy to make at home out if 1/4" flat steel stock so I'm not going to commission a CAD drawing at this time. If someone wants to make a CAD drawing of the additional 240SX bracket feel free to do so and share. Also feel welcome to use the finished drawing as a basis for any rear disc brake conversion you care to undertake. All of the basics are there.
Charlie Durning
FYI. Using a spare prototype bracket I did a 34mm Sentra install on a 77 RBB roadster. There are a couple of challenges. All but one can be resolved easily. The biggest issue is the boot floor for that car is different from the CBB GT. There is interference between the park brake linkage and the boot floor. This weekend we are going to experiment with a different park brake lever on the caliper. Failing that the 34mm 240SX caliper will be a better choice since the park brake lever on the caliper is located close to the axle housing and not out the back.
We did take the car for a spirited test drive on a rainy day and we feel the 34mm caliper is well suited for the RBB roadster. We also took out the CBB GT and feel the 38mm 240Sx caliper is a good match for that car. The early 240sx, target date 1992, has a 34mm bore and the later 240SX, target date 1998, has a 38mm bore. Both will use the same add on caliper bracket since the exterior and mounting dimensions are exactly the same.
Resolved the park brake clearance on the 77RBB. Originally I was going to make a new arm for the caliper that would lower the attaching point. In the end I just shortened the flat arm on the caliper and that gave enough clearance. I also moved the attaching point for fiber flex for better alignment.
Latest drawing with corrections for Sentra caliper. It should print full size
MGB-Nissan_Bracket-1-page-005.jpg
I finally got around to rerouting the brake flex hose to the caliper. On the Sentra caliper the hose went straight in towards the center of the car and behind of the limit strap. I was just not happy with that. For the 240SX caliper i sent over and and in to the center of the car. I didn't care for that either. In reality I was using the hose available to me at the time. In doing further digging I found a vendor on eBay who will make custom brake hoses. For the Sentra conversion on the RBB car I had him make a pair of 18" long hoses with the banjo bent at 45 degrees. I thought the 18" hoses would also work for the 240SX. The 18" does fit the 240SX but a better choice would be 20". What the 45 degree bend does is allow the hose to be routed down the back of the caliper and then up and over the axle tube. That routing keeps the brake hose out of harms way. The pictures are for the 240Sx install on the CBB GT. The 18" hose for the 240SX ends up routing behind of the bump stop on the axle. A 20" hose would be better routed in front of the bump stop. With the Sentra caliper the 18" brake hose can be routed in front of the bump stop also.
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I had a pair of brackets made from the latest drawing. I should be able to do a mock up on a spare housing to prove the drawing this weekend
Did a test fit. The laser cut brackets are a perfect fit. All I had to do was clean up the bolt holes and make a small radius so it would fit flush against the axle housing flange.
I have had several requests for clarification on the applications for the Rotor and calipers I have used for the disc conversion. Hope this is useful.
Rotor and Caliper Applications
Buyer's Guide : CENTRIC 12140024 Rotor
ACURA CL 1997
HONDA ACCORD 1991-1997
Please refer to catalog for application details.
38MM 240SX caliper applications
Buyer's Guide : BECK/ARNLEY 0771213S Caliper
NISSAN 240SX 1994-1998
Please refer to catalog for application details.
34MM 240sx caliper applications
Buyer's Guide : CENTRIC 14142512 Caliper
NISSAN 240SX 1989-1993
Please refer to catalog for application details.
34MM Sentra caliper applications
Buyer's Guide : A-1 CARDONE 19B2627B Caliper
INFINITI G20 2002
NISSAN SENTRA 2002-2006
Please refer to catalog for application details.
Manufactures names and part numbers are for reference only. Parts from any manufacture for the application will be suitable
Right and left calipers required
The pics below will show specifics on the Rotors and calipers
1992240sx.jpg
1998240sxcaliper.jpg
2002sentra.jpg
CE_12540024_1994HondaAccord.jpg
Lot of great info. Thanks, Charles!
Rhere have been questions about how the secondary bracket for the 240sx caliper and the Sentra bracket fit together. The secondaty SX bracket is attached to the inboard side of the Sentra bracket. That provides the necessary additional offset for the SX caliper. Hope this helps.
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Made a handy fixture for boring out the center hole in the caliper with a drill press. Found a 2.5" washer with a .75" hole. Used a 7/8" hole saw to make a bushing. Mounted the washer and bushing to a piece if wood that will also be a handle. The washer centers the rotor and the bushing guides the hole saw. Knock out a rotor in 2 minutes.
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I've had questions about fitment with wire wheels. I don't have a wire wheel so I cannot give a definitive answer. Hoewer ,here are some shots with a wire wheel hub. From that you should be able to discern if this will clear a wire wheel. The rear axle in my GT is a wire wheel axle. There may be some body clearance issues with the wire wheel axle that may not be an issue with a bolt on wheel axle. The conversion I did on a RBB roadster did not have any clearance issues other than the park levers had to be shortened for clearance with the boot floor withe the Sentra caliper. That is not an issue with the 240sx caliper. I'll post the sx caliper fitment with the WW hub later today.
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Here are pics of the 240SX fitment along with a pic with a WW hub
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Yesterday I had all of the parts and time all in one place. I made a new mock up and test fit the secondary bracket to be used with the more accurate Bob Harper drawing of the Sentra mount bracket. This 240SX bracket moves the caliper in slightly for better placement of the pads. The previous bracket placed the pads even with the OD of the rotor. This bracket places the pads at the outer edge of the contact surface of the rotor. Bob Harper has agreed to create the cad drawing of the bracket also. I will post when it is available. Attached is the more accurate drawings for those who want to go ahead and make their own bracket. One suggestion is to drill the 5th hole once the brackets are attached together on the axle. I was not able to establish a spot on accurate location for that hole. The attached drawing is a tracing from the mock up bracket. All other measurements are accurate.
Another consideration, my CBBGT is lowered by using 5 leaf rear springs and early roadster front springs and it does have a wire wheel rear axle. With 2 people and luggage it does bottom on the bump stop when hitting a harsh bump. Though measurements show adequate clearance it is very close. As a preventative measure I am adding an Energy Suspension 9.9117G to the bump stop on the axle. I'll get better measurements for the 2 CBB conversions I'll be doing in May. Those cars have not been lowered and have bolt on wheels which moves the caliper outboard in relation to the body. No issues are noted with the RBB roadster at normal ride height.
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Bob Harper was kind enough to draw up both a PDF and a DXF CAD drawing of the secondary 240SX bracket. The DXF file is laser cutter ready. If anyone wants a copy just PM me your e-mail address and I'll send it right out. I have not commissioned any brackets based upon the drawings, however, the drawings do match my tracings of the prototype bracket.
The question has been asked about increased pedal travel. There is some additional pedal travel though I would not consider the additional travel as disconcerting.
My master cylinder shot craps on me, I was expecting it since it would lose the front circuit occasionally. While I had the system open I took the opportunity to install a pair of 2 psi residual check valves. The valves did make a difference and brought the pedal to almost the original position. I would say try without and see what you think. If you feel the travel is too long, installing the residual valves may be the answer.
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I have posted my closing comments on this conversion here
https://www.mgexp.com/journal/geezer/16968
Unless there are further questions I am putting this to rest
Charles,
A question about the connections at the brake lines. How did you make the connection from the MGB brake line to the Datsun or Nissan caliper ? One is British threads and the others metric
Werner
Hello Charles I'm new on this site and have just found your post's about disc brakes on mgb and was wondering how thick the mounting plate you made was. Regards Robin
VernerVC, Nibor1,
I apologize, it's been awhile since I visited this forum.
Yes the Nissan caliper is metric. The flex hose I used has a compatible banjo end for the caliper and the other end is -3 inverted flare for a 3/8-24 thread inverted flare nut. The hard line has an inverted (double) flare on the 3/16" pipe.
The primary bracket is made of 3/8" flat steel and the secondary bracket is 1/4". I have positive feedback from one fellow who made the brackets from aluminum.
Hope that helps
'I have positive feedback from one fellow who made the brackets from aluminum. That is interesting. I can cut aluminum much easier. I am curious what thickness he used.
Carl,
I'm using 1/2" 6061 aluminum for my rear caliper brackets. Different set-up than the OP, with Wilwood calipers on a Mopar rear end but no issues with the brackets at all.
Bill
As a general rule I'd expect that anything over 5/16" should be adequate. Probably the biggest issue is having adequate depth of thread in the aluminum part.
Jim
I hadn't thought about threading the aluminum. I am sure y'all would say to use fine thread.
Or steel thread inserts. The one who used Charles design probably used the thicker dimension and milled down to the thinner. Anything under 3/8" I'd use steel if 3/8" or thicker aluminum would be fine.
For lightest weight nutserts would be another option.
Jim
Yeah, I forgot to mention that I also installed heli-coils for the caliper mounted bolts.
Bill
I used a version of Charlie's design on my rear axle. Works great! Just an FYI, the caliper brackets on the Honda Civic calipers I used are threaded so you don't need thread's in the fabricated brackets, just holes.
Thanks for that info, Scott!
I just saw the comments about threading the brackets. None are threaded and I used nuts and bolts. The caliper factory bracket is threaded so that bolt goes through a drilled hole into the factory caliper bracket..
FWIW I did weld the 2 brackets together, along with using the bolts and nuts, just for my satisfaction.
It has been awhile since I have posted here. Just thought I would update this thread. Tim Nagy is now making the brackets for the rear disc conversion. If interested, contact him directly.
Rear brackets available here
morspeedperformance@gmail.com
http://morspeedperformance.tgnagy.com/rearDisk.cfm
Good to know. Thanks, Charles! Tim, as well. :)
There is one thing that we should have addressed on page one but I think we were too lost in the nuts and bolts to think about, and that's the whole question of whether or not it's a good idea to use disc brakes at the rear in the first place. There are valid arguments both ways of course but I think it's worth discussing.
One view is that the drum brakes are perfectly fine and don't need to be messed with. I think that's valid. Here is something that isn't usually considered: Drum brakes are self actuating. This is particularly important when they are used as a parking brake because it means less pull is required at the handbrake lever to get the same holding power. With discs you need every possible mechanical advantage to achieve the same thing and any single detail can derail the effort.
Jim