Charles Durning's Journal --
Due to the Covid 19 scare I have plenty of time on my hands. Off and on there has been discussion about improving the front disc brakes for MGBs. There are pros and cons over the effectiveness and weight of any conversion. All points are valid and any conversion offers compromises as does the OEM design. What peaked my interest was the conversion using MGRV8 parts. At around $500, from suppliers, the conversion seems to be appealing. If the caliper is what I think it is, same as Rover SD1 or Princess, The piston surface area is equivalent to the piston surface area of the MGB caliper, no benefit there. Also, being a 4 piston caliper, the weight is greater. The benefit is the pressure is applied to a larger pad. The other concern is the weight of the rotor. Since I have no specs on the rotor is could be heavier than the MGB. The benefit I see with that conversion is better heat dissipation due to the vented rotor and larger pads with the braking effectiveness being about the same as the MGB. Correct me if I am wrong. There are several DIY projects that I have seen using Toyota truck 4 piston calipers and and Volvo 4 piston calipers. Those calipers have the same effective piston surface area as the MGB with added weight. I did look at a Toyota Prelude brake conversion that was teased on the British V8 forum. Though the piston surface area is slightly larger than the MGB is caliper is enormous and uses a rotor that is 7/8" wide. All very heavy and would require at least a 15" wheel to get a decent size rotor. On the plus side, the larger rotor and caliper piston could offer better braking performance. The problem with MGB front brake conversions is the design of the swing axle. That limits the way another caliper can be mounted. That got me to thinking. I decided to dig through the gold mine to see what I have. What I found were the parts I used when I converted the front brakes on the Morris Minor and the Chick Magnette. The caliper I dug out was from a 1995-1999 Nissan Sentra. It's very compact and has the same piston surface area as the MGB. The rotor I found was from a 1985 Toyota Cressida. Though the rotor is smaller than the MGB by .150" it is vented and fits the Sentra caliper. Comparing the weights with the MGB parts, the weight is the same as an assembly. MGB caliper is 7lbs, Sentra caliper is 5lbs. MGB rotor is 10lbs, Cressida rotor is 12lbs. The part to put this all together was the bracket I designed for the Morris. The Morris bracket did move the caliper out too far to fit the rotor. But as a test fit the concept has promise. All it took was to move in the caliper by 3/8" inch. Now the Sentra pads are near the outer edge of the rotor and the entire assembly fits nicely within my Minitor wheels. So what I have here is a brake conversion with about the same braking effectiveness as the MGB but with a vented rotor with no weight penalty. As an aside there are possibilities for those folks with 15" or 16" wheels to get better effectiveness using a larger rotor. One of the issues I found with using a larger caliper is the caliper makes contact with the suspension near full lock. I don't any practical way to avoid that problem. Since the Sentra caliper is more compact that problem can be avoided with a simple stop made into the mount bracket. Some may like that some may not. Here are the costs so far. The Cressida rotor PN 9911R can be found on Rock Auto for $13.00 each, The Sentra caliper L1792, L1793 can be found on Rock Auto for $40.00 each. The Sentra ceramic pads ZD668 can be found on Rock Auto for $9.00. I made the simple flat bracket from a piece of 1/4"x1.5" scrap steel and you may need some misc bolts and spacers to fit it all together. I have yet to work out the brake hose but a Rubber Bumper Midget front brake hose has promise. Aside from getting the parts, the pilot bore on the rotor needs to be enlarged to about 3" to clear the front hub. The rotor will be mounted outboard so a provision for set screws to locate the rotor on the hub will need to be drilled, countersunk, and tapped. The bracket can be mounted on either side if the caliper ears on the swivel axle. If mounted inboard you will need 2) 3/4" long spacers. If mounted outboard the Nissan caliper bracket will need a slight modification for clearance. Either way the caliper will be centered on the rotor. For about $125.00 (maybe less with some shopping) and some sweat equity you too can have vented front disc brakes using common parts available in North America. The cost of the conversion is awash if you are replacing all of the MGB brake parts anyway during a brake overhaul. All I have right now is the proof of concept. I'll do a test fit and shake down on the MGB as soon as all of the parts arrive. I do have a CAD drawing for the bracket I used on the Morris All you need to do is reduce the hole spacing to 3/8" and extend one end slightly to act as a turn stop.
Posted 2020-04-29 10:06:27 by charles durning
Due to the Covid 19 scare I have plenty of time on my hands. Off and on there has been discussion about improving the front disc brakes for MGBs. There are pros and cons over the effectiveness and weight of any conversion. All points are valid and any conversion offers compromises as does the OEM design. What peaked my interest was the conversion using MGRV8 parts. At around $500, from suppliers, the conversion seems to be appealing. If the caliper is what I think it is, same as Rover SD1 or Princess, The piston surface area is equivalent to the piston surface area of the MGB caliper, no benefit there. Also, being a 4 piston caliper, the weight is greater. The benefit is the pressure is applied to a larger pad. The other concern is the weight of the rotor. Since I have no specs on the rotor is could be heavier than the MGB. The benefit I see with that conversion is better heat dissipation due to the vented rotor and larger pads with the braking effectiveness being about the same as the MGB. Correct me if I am wrong. There are several DIY projects that I have seen using Toyota truck 4 piston calipers and and Volvo 4 piston calipers. Those calipers have the same effective piston surface area as the MGB with added weight. I did look at a Toyota Prelude brake conversion that was teased on the British V8 forum. Though the piston surface area is slightly larger than the MGB is caliper is enormous and uses a rotor that is 7/8" wide. All very heavy and would require at least a 15" wheel to get a decent size rotor. On the plus side, the larger rotor and caliper piston could offer better braking performance. The problem with MGB front brake conversions is the design of the swing axle. That limits the way another caliper can be mounted. That got me to thinking. I decided to dig through the gold mine to see what I have. What I found were the parts I used when I converted the front brakes on the Morris Minor and the Chick Magnette. The caliper I dug out was from a 1995-1999 Nissan Sentra. It's very compact and has the same piston surface area as the MGB. The rotor I found was from a 1985 Toyota Cressida. Though the rotor is smaller than the MGB by .150" it is vented and fits the Sentra caliper. Comparing the weights with the MGB parts, the weight is the same as an assembly. MGB caliper is 7lbs, Sentra caliper is 5lbs. MGB rotor is 10lbs, Cressida rotor is 12lbs. The part to put this all together was the bracket I designed for the Morris. The Morris bracket did move the caliper out too far to fit the rotor. But as a test fit the concept has promise. All it took was to move in the caliper by 3/8" inch. Now the Sentra pads are near the outer edge of the rotor and the entire assembly fits nicely within my Minitor wheels. So what I have here is a brake conversion with about the same braking effectiveness as the MGB but with a vented rotor with no weight penalty. As an aside there are possibilities for those folks with 15" or 16" wheels to get better effectiveness using a larger rotor. One of the issues I found with using a larger caliper is the caliper makes contact with the suspension near full lock. I don't any practical way to avoid that problem. Since the Sentra caliper is more compact that problem can be avoided with a simple stop made into the mount bracket. Some may like that some may not. Here are the costs so far. The Cressida rotor PN 9911R can be found on Rock Auto for $13.00 each, The Sentra caliper L1792, L1793 can be found on Rock Auto for $40.00 each. The Sentra ceramic pads ZD668 can be found on Rock Auto for $9.00. I made the simple flat bracket from a piece of 1/4"x1.5" scrap steel and you may need some misc bolts and spacers to fit it all together. I have yet to work out the brake hose but a Rubber Bumper Midget front brake hose has promise. Aside from getting the parts, the pilot bore on the rotor needs to be enlarged to about 3" to clear the front hub. The rotor will be mounted outboard so a provision for set screws to locate the rotor on the hub will need to be drilled, countersunk, and tapped. The bracket can be mounted on either side if the caliper ears on the swivel axle. If mounted inboard you will need 2) 3/4" long spacers. If mounted outboard the Nissan caliper bracket will need a slight modification for clearance. Either way the caliper will be centered on the rotor. For about $125.00 (maybe less with some shopping) and some sweat equity you too can have vented front disc brakes using common parts available in North America. The cost of the conversion is awash if you are replacing all of the MGB brake parts anyway during a brake overhaul. All I have right now is the proof of concept. I'll do a test fit and shake down on the MGB as soon as all of the parts arrive. I do have a CAD drawing for the bracket I used on the Morris All you need to do is reduce the hole spacing to 3/8" and extend one end slightly to act as a turn stop.
| Image may be NSFW. Clik here to view.  <assembled> | Image may be NSFW. Clik here to view.  <bracket proof> | Image may be NSFW. Clik here to view.  <caliper> |
| Image may be NSFW. Clik here to view.  <final bracket> | Image may be NSFW. Clik here to view.  <fit> | Image may be NSFW. Clik here to view.  <fit1> |
| Image may be NSFW. Clik here to view.  <side view> | Image may be NSFW. Clik here to view.  <steer angle> |
Posted 2020-04-29 10:06:27 by charles durning