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Post by powerflite on Sept 25, 2007 10:51:53 GMT -8
I have a 68 Corona 2dr hardtop that I would like to convert to disc brakes on the front. Does anyone know if the newer Corona or Corolla parts will mount up to the original spindle or of any way to make this conversion possible? Thought I would check the body of knowledge first before I start tinkering around. Thanks in advance.
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Post by 68 Corona on Sept 25, 2007 15:59:10 GMT -8
Hello
You need to contact Carline Dincler: cdinkler@bellsouth.net He should be able to help. Good Luck
Luis
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Post by powerflite on Oct 3, 2007 9:10:10 GMT -8
I talked to Carlyn Dinkler. He told me that the 70-73 Corona disc brakes are a direct swap, but that you have to swap the steering knuckle as well, which means scouring around wrecking yards for a car that I can dismantle. Bogus.
Maybe I should manufacture my own disc brake knuckle with a built-in 2" drop instead. That way I could drop the front the right way and possibly use larger discs as well.
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Post by 68 Corona on Oct 4, 2007 12:22:38 GMT -8
Hello
I recieved this info from John a while back. Hope this can help you
Corona 1600S,s have the same brake calipers as series 1 e-type Jaguars, so when looking for pads or kits get the ones to suit a series 1 e-type jag. the hubs and rotors are not the same as the e-type jag. RT40's,RT51's etc and RT80/81's all have the same stub axle. I have upgraded the brakes on an RT56 5 door and an RT46 ute useing disk brakes from RT80/81's. It's a simple matter of getting the hubs, rotors, calipers, backing plates, proportioning valve, brake booster and associated plumbing. The only thing you have to do is put a dent in the inner gaurd to accomodate the booster and drill holes for the booster bracket and the proportioning valve (this is mounted on the fire wall). The pipe that ran from the small brass fitting on the chassis rail needs to be carfully bent up to join up with the newly mounted proportioning valve on the fire wall. The rest of the plumbing from the proportioning valve forward is from the RT80/81 (you need to make sure you get the brass junction mounted on the chassis rail of the RT80/81 to replace the RT40 one. In short the only thing you can use of the original RT40 stuff, forward of the proportioning valve is the pipes running from the junction to each of the flexible lines that run to the callipers (Note: This is assuming you do not already have a proporiting valve in the system already, some of the late drum brake RT40's have a proportioning valve mounted under body). I have made the mistake of taking the advise of some, that TA22 Celica stuff is the same, this is not the case. The rotors and hubs on early TA22 celicas are the same (Some TA22's have a larger stub axle and run bigger brakes). The backing plates and callipers are different to the RT80/81, even though at first glance they look the same and use the same pads as the RT80/81, Trust me on this one I still have a set of TA22 Callipers and backing plates sitting in my shed that I can't use. Hope this has been some help
John Good Luck. Keep me posted as I want to upgrade to.
Luis
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Post by coronadlux on Oct 19, 2007 11:29:14 GMT -8
I have done the swap. I used first generation celica hardware. All that was needed was to drill the holes on the bracket to make it fit. The bearing sizes are the same, so the brakes went on without a hitch.
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Post by powerflite on Feb 18, 2008 13:00:33 GMT -8
I finally picked up the disc brakes and front suspension from a '71 Corona 4dr in a wrecking yard in Mohave, CA. The rest of the car is still there and has many good parts on it. Supposedly, the motor turns over, but without a coil they haven't tried starting it. The website for it is: www.californiadeserttreasures.com/ShowItem.aspx?itemid=58
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Post by powerflite on Jul 11, 2008 15:12:13 GMT -8
I thought I would update info on this to clear up some things. The steering knuckle for the Corona drum and disc brakes are exactly the same. At least for '67-'73. All that was required was the calipers, brackets, backing plate, hubs and rotors. Converting to power brakes is nice, but not required. I removed the residual pressure valve from the front side of my master cylinder (just inside the line connection) and bolted it together with an aftermarket proportioning valve in the back at the location of the original valve just ahead of the rear axle. Non-power discs grab better with non-metalic brake pads.
If you wanted to make a conversion from scratch, all you would need is the caliper brackets, dust covers, and hubs. Buy the calipers and rotors new. Non-correct, but working covers and brackets would be relatively easy to reproduce, but the hubs are the hard part.
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Post by Carlyn Dinkler on Jul 13, 2008 4:19:09 GMT -8
Good information on the conversion to front disc brakes. I had never done a conversion and I mistakenly assumed the RT8#/9# (1970-73 Corona) steering knuckles had the mounting ears for the disc brake calipers like the RT6#/7# (1969-72 Corona Mark II) ones that I more familiar with. For the RT6#/7# there were steering knuckles for front disc brakes with mounting ears and without for front drum brakes (I have never had an RT6#/7# with front drums).. The steering knuckles (43211-20010) were the same 1965-73 on the Coronas.
There was an earlier disc brake system (see the earlier post Oct 4, 2007) used on the Corona 1600S, etc. but parts for this are not generally available. The tubing for this does not show a proportional and the part number on the M/C is 47200-20051/52 is a different part number from the single M/C's used on the RT43/52. The 47200-20051/52 is a single circuit (not tandem) master cylinder as were most on RT4#/5# outside the USA/Canada. It would be good to know the specs on the 47200-20051/52 M/C. Toyota used 14" wheels with this system possibly for clearance.
So to make the conversion to front disc brakes on the RT43/52, you would need to have the following major parts (and all the associated hardware): 43512-20032 disc's 43511-20915 hubs TMD (discontinued from Toyota) 47781-20030/47703-20010 dust shield RH TMD 47782-20030/47704-20010 dust shield LH TMD 47751-20030 caliper mounting bracket RH TMD 47752-20030 caliper mounting bracket LH TMD 47710-20060/61/52 caliper assy RH TMD 47720-20060/61/52 caliper assy LH TMD
Per Powerflite, if I understood correctly, using the standard tandem brake M/C which is 3/4" dia., he removed the valve assembly on the front outlet to the disc brakes (you have to remove the brake line, un-screw the plug the line screws into & remove the valve & spring). The valve is to slow the return of brake fluid from the wheel cylinder so you can 'pump' the drum brakes to make-up for some shoe wear, but is not used on disc brakes.
Powerflite then replace the factory proportioning valve with an aftermarket valve.
Powerflite, please tell why you replace the proportioning valve instead or using the original, and where you can buy the replacement, and any other details I may have missed.
The 1965-70 RT43/52 used a 3/4" diameter brake master cylinder while the 1970-73 RT8#/9# used a 7/8" diameter master cylinder, and I wonder what difference this makes? I believe that here was a remote power brake booster used on some of the 1965-70 Coronas because of lack of room to use the booster between the firewall & M/C but at this minute, I do not know where to look.
If only a few people want to make this conversion, the parts are out there (I have some stock of disc's & caliper assemblies), and the rest would be found in junk yards, and on eBay. It would be nice to have all the parts available in a kit, but someone would have to make about 200 kits, maybe in China, and you never know if you can sell enough to recoup your initial costs.
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Post by powerflite on Jul 21, 2008 18:10:37 GMT -8
Carlyn, the difference in master cylinder size has little to do with disc vs. drum, but more to do with power brakes vs. non-power. With power brakes, you don't need to worry about how hard it is to press the brakes so a larger diameter will provide more fluid so that your pedal travels less. If you use a large diameter master without power, it is too difficult to actuate the brakes with adequate force. A smaller diameter makes it easier to push.
The original proportioning valve for disc brakes is mounted on the firewall and to use it, a lot of re-plumbing is required for the front and rear wheels as well as having to drill into your firewall. Replacing the original drum brake valve (in the back) with an adjustable one, eliminates a lot of this trouble and gives you adjustability. The only drawback to this approach is that the single valve in the back is more of a rear pressure reducer and doesn't really proportion the force front to back so it is a little harder to push set up like this. Adjustable valves can be purchased at Summit, Stainless Steel Brakes, or Master Power Brakes, etc. They use pipe thread connections so you can adapt to the lines.
If you want to use the original valve; which is arguably better, don't forget to remove the original drum valve in the back just ahead of the rear axle or else you will be cutting the rear pressure too much. That is, assuming that Toyota didn't design the system to use both of them when they switched to discs. I didn't check the rear of this '71 to see if that is the case.
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