Brake Up-grades MR2 Parts Vented Rotors Corolla Spacer Figs

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Petros
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Brake Up-grades MR2 Parts Vented Rotors Corolla Spacer Figs

Post by Petros » Sun Nov 01, 2009 12:46 am

I finally got around to putting on the vented disks on my '84 Tercel4wd, my stock pads were nearly gone so I thought this would be a good time to do the swap. I will post pictures later next week. Here is what parts I used to up-grade to vented front disk brakes and improved Master cylinder/booster:

(2) vented front rotors from a '92 Tercel
(2) home made aluminum shim/spacers 1/8" thick to get the correct off-set on the rotors
(2) MR2 front calipers L and R (from 1986)
(2) MR2 flex hoses with banjo fittings
(1) MR2 Master cyl. assembly (from 1986)
(1) MR2 power booster (from 1986)
(4) tie-wraps to secure the longer flex hoses
Brake fluid

I used the MR2 calipers because that is what I had, it is likely the '92 Tercel calipers would work exactly the same way, they look very similar (dimensionally the same and same dia. piston) but they are not the same part number. Also the Corolla caliper might be made to work, as well as the Corolla rotors, or the MR2 rotors, (both are the same thickness as the 4th gen Tercel rotors I used) but both of these rotors have larger center-line off-sets. This would require a 0.2 or .25 spacer instead of the .125 that I used (this larger spacer might mean you will need to install longer wheel studs, I did not on mine). Note that all of these rotors have the same 100mm x 4 lug pattern and are directly compatible with the Tercel bolt pattern.

I had searched a number different Toyota applications for a smaller dia. master cylinder to improve the braking ratio. The braking advantage is a direct ratio of master piston area to total wheel piston areas, the smaller the master cyl. piston dia. the better the braking power. Of all of the master cyl. with smaller piston dia. I inspected, none of them are a direct bolt on. All of them also have the brake lines mounted in different locations, making the adaptation more difficult. By luck I got an MR2 parts car to strip and found that, while the master cyl mounting is totally incompatible in the Tercel, the power booster mount and pedal attachment were identical to the Tercel, so the whole master cyl/power booster could be swapped over together as a unit. The MR2 master cyl. brake line location were also reasonably close and easy to adapt to the Tercel stock line locations as well. It just took a few new bends in the brake lines to get them to bolt up, otherwise same mounting and routing.

Note that changing the master cyl. dia. does not change the front to rear bias ratio, so I did not have to change the proportioning valve. My eventual plan is to try and adapt the MR2 rear disk brakes and calipers to the Tercel, and than I would either need to install the MR2 proportioning valve or install an aftermarket adjustable one.

With the 1/8" spacer shims everything bolted up perfectly. I had made some measurements and even a test fit of the 4th gen Tercel front rotors and at first it appeared they would bolt up without spacers. But it was too tight a fit unless you shave the inside brake pad down. It was easier just to make spacers, and it would allow longer pad life too. NAPA sells similar spacers for a very reasonable price, I made mine from some scrap aluminum stock I had in my stack of junk in the garage.

I had intended to do some dry road braking comparisons of 60-O mph braking distances of both before and after, using the same car and tire/wheel combination. But doing that accurately is not easy by yourself, and you need a level and strait stretch of road (of which we do not really have around here). Also, it was pouring down rain all day today, and wet weather stopping power is more a function of the tire design than brakes. I had to change my brake pads and was ready to do the whole swap over now, so I did not get a "before" stopping distance test in. I still may do an "after" test for you to compare with your own cars.

Based on pedal feel alone, this braking set-up is very much improved over the stock installation. I would estimate it takes about 25-30 percent less pedal pressure for the same stopping power, and the brakes are a lot more solid feeling. My Tercel4wd now brakes like a much heavier vehicle with bigger brakes and a bigger power booster. And a number of hard stops showed no hint of fade or overheating, unlike those flimsy little 11 mm thick front rotors that came on the Tercel4wd. I warped my share of stock rotors without even trying, that is hopefully a thing of the past.

Pictures to be fourth coming.
Last edited by Petros on Tue Jul 03, 2012 3:56 pm, edited 2 times in total.
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Re: Brake Up-grades

Post by Typrus » Sun Nov 01, 2009 2:50 am

Sounds awesome!
With the stock tire size, I could easily lock up all 4, but with the 205/55R15's it was very hard to lock them up, and you had to mash hard to get it to really stress the system.

With vented rotors, I'd imagine my 112-0 stops would have been much easier, and not resulted in smoking pads. lol.

Awesome!
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Re: Brake Up-grades

Post by sdoan » Mon Nov 02, 2009 5:13 pm

Petros - sounds like you've done a lot of good work. And this is a great thread. Can't wait to see the write-up. Thanks

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Re: Brake Up-grades

Post by Petros » Thu Nov 05, 2009 9:58 pm

Below is the comparison of the different rotors. On the left is the stock 11mm thick solid rotors, in the center is the 25 mm vented disks from the '92 Tercel, and on the right is the 25 mm vented rotors from the '86 MR2. Notice how the hub part of the MR2 rotor is taller, giving it a different off-set. The Corolla rotors are similar to the MR2 rotors. I got the '92 rotors from a self service wrecking yard (the local Pull-A-Part) for about $6 each. You can also buy new ones for about $30 each. All have exactly the same bolt pattern.

Image
I was hoping the later Tercel rotors can be used without spacers since they are not at tall, but no such luck. I made spacer rings from 1/8" aluminum sheet. They go between the inside of the rotor center and the hub as shown in the photo below. It gives my front tires about 1/4 inch wider tracking, and I swear it improves handling.

Image
If you make your own spacers, make sure they fit all the way down flat against the inside of the rotor. It does not have to be super precision, but you do want it centered so it does not affect the balance. Aluminum will add minimum weight, transfer heat well, and it easy to hand work. I considered using four large washers, but this will not allow the heat to dissipate and without the hub fully supported, I suspect there is some risk of warping the rotors. To cut out the spacers I used a hole cutter and a hand held drill, but I made it a bit too large and ended up sanding down the outside diameter to fit. You can also just scribe a circle and cut it out with a hack saw or metal cutting blade in a hand held jig saw, and file by hand until it is reasonably smooth. The 1/8th inch thickness also did not require longer wheel studs.

Image
This photo compares the stock right side caliper from the Tercel4wd and the MR2. (The MR2 caliper on the right has the mounting bolts in the support bracket, the stock caliper uses exactly the same size and length bolts). Notice the larger space between the brake pads for the thicker vented rotor. Also notice how the stock flex hose threads directly into the caliper and the MR2 caliper requires a banjo fitting that is also at a different angle. The Tercel flex hose will thread into the MR2 caliper, but it will not seat properly and likely leak. The Tercel flex hose end has to seat against a taper to seal it, which the MR2 caliper does not have in the bottom of the threaded boring. I believe both calipers use the same disk brake pad, so you do not even have to order anything different to replace the pads.

Image
This is the stock installation, ready to come out. To remove:
1) loosen the wheel nuts, jack and securely support car on stands
2) Remove wheel, remove two 17 mm bolts that hold on the caliper assembly (this likely will require a large breaker bar or wrench extension).
3) Hang the caliper with string or wire, and pull off rotor. This may require a few taps with a rubber hammer, but should come loose with a little effort.
4) Install spacer and new rotor.
5) Remove 10mm brake line flare hose nut at wheel well mount.
6) Remove clip that holds flex hose to wheel well mount, this will allow you to remove the caliper and flex hose together.

Image
This is the vented disk assembly installed. You can see where the flex hose mounts on the wheel well. To install the new brake calipers:
1) Mount the caliper on the hub with the (2) 17mm bolts
2) Install the longer flex hose on the caliper with the banjo fitting, the manual recommends to use new copper washers but I have always reused the old one without problems (be sure to check for leaks if you reuse the old washers). Before you tighten down the fitting, position the fitting so the hose points toward the strut.
3) Install the other end of the flex hose to the brake line and than install the retainer clip. Before you install the retainer clip, twist the hose around so it will stay tucked in against the wheel well where the tire does not rub against the hose or the hose will not rub against the inside of the wheel well.
4) This type of longer flex hose was intended to have a bracket on the side of the strut, since the stock strut does not have such a bracket I used two large zip-ties to hold the hose against the strut. You have to position it so the strut can move from lock to lock and through the full range of travel so the flex hose does not rub against the tire or wheel well. If you switch to the heavy duty 2" dia struts from the Corolla All-trac, which I may still do, it will have the flex hose mount in the correct location, it mounts with the same type of clip as used at the end of the flex hose. You could also fabricate a metal mount that can be attached to the strut with a metal hose clamp. I think the two tie-wraps should work fine, but I will be checking it regularly to make sure it stays in-place without rubbing.

Image
Installation completed, now you just have to bleed the brakes in the normal way. At this point there will be no change in the pedal effort, nor in the front to rear braking bias, since these rotors are the same diameter and the caliper has the same size piston. They should be a bit more solid, and you will not warp or fade these vented brakes. The '87 and newer MR2 has larger dia. rotors and bigger calipers to match, as does the GTS Corolla, but I do not know if you can get that size rotor with the smaller off-set of the Tercel, so you would need 1/4" spacers to use the larger brakes, and longer wheel studs. It might worth considering if you want even bigger brakes, there are lots of high performance brake kits available for the MR2, including slotted and drilled rotors and heavy duty calipers..

Image
This is the back side of the stock Tercel4wd booster, and the MR2 booster on the right. This is the side that bolts to the firewall. The bolt pattern and length is identical, and the yoke that attaches to the brake pedal is also identical, allowing you to switch the master cylinder. I had to adjust the yoke location about a 1/4" so it was the same distance to the brake pedal mount. This controls the brake pedal height.

Image
This is the front side of the booster, the MR2 booster is on the right. I did not have the stock tercel4wd master cylinder handy to compare, but notice there are only two mounting bolts for the master cyl. on the stock Tercel. Also notice the vacuum line fitting in the booster is in a different location, it puts it close to the distributor but there was still plenty of clearance. The MR2 master cyl. has four mounting bolts, but by changing the booster, it allows you install the MR2 master cyl. This MR2 master cylinder is a superior design, and it is a smaller bore diameter, reducing the effort at the pedal for the same amount of stopping power.

Image
The stock master and booster removed. To remove:
1) Remove the trim panel under the steering wheel below the dash. About 5-6 phillips head screws. Remove the heater duct right behind the trim panel, one screw.
2) Remove the clevis pin and return spring from the top of the brake pedal to free the yoke from the pedal.
3) Remove the (4) 12 mm nuts from the firewall that holds the booster in place. This requires a deep socket.
4) From the engine compartment, remove the distributor to give you clearance (one 12mm bolt and the vac lines, I left it plugged in and flopped it over the top of the valve cover).
5) Unbolt the master cylinder bolts to free the line bracket under the master cylinder. Remove the flare hose nuts with 10mm open end wrench and unplug the fluid level indicator wire. Both the master cylinder and booster should come free.

Image
You will have to bend the brake lines out of the way temporarily. Than install the booster and master cylinder in the reverse order as above. I put sealant between the back of the booster and the firewall to prevent air or moisture leaks into the foot well area. You will have to carefully bend the brake lines (to prevent kinking) to line up with the MR2 master cylinder line locations. The rear line almost aligns, only a little tweaking required. The front line has to be bent over the top and aligned with the new location, as you can see in this photo. There is enough excess length to allow repositioning of the line.

Image
Installation complete, with the distributor back in place. I had to reset the timing of course, but there would have been no room to work without removing the distributor. I mounted the line support bracket onto the two lower master cylinder mounting bolts, they are the same distance apart as the stock master cyl, it just puts it about an inch or so lower. The only thing left to do now is to swap the connector for the low fluid indicator, or make an adapter connector. I moved the vacuum line mount on the fire wall over a few inches to prevent any sharp bends in the vacuum line, but I do not think it was really necessary. I bled both the brake lines first at the master cylinder to get all the air out of the master, and than at the front wheels. I did not even have to bleed the back brakes. The whole installation went better than I thought it would, no cutting or altering of parts or mounts, except to make the spacers.

I was going to clean and paint both the calipers and rotor hubs with bright red or orange heat paint so it would look cool, but with the MR2 alloy wheels I am using, you can not see them anyway. I also did not want to take the extra time. If I replace the wheels I may make the calipers look pretty. I be sure to post pictures here if I ever do.
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Re: Brake Up-grades

Post by ARCHINSTL » Fri Nov 06, 2009 4:35 am

WOW!
One of, if not, the best write-ups!
Thanks!
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Re: Brake Up-grades

Post by sdoan » Sat Nov 07, 2009 7:28 pm

Great write-up Petros. Easy to follow. I'm also tempted by your brake-booster MC combination. Thank you!

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Re: Brake Up-grades

Post by Neu » Sun Nov 08, 2009 1:28 am

Great write up.

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Re: Brake Up-grades

Post by Petros » Sun Nov 22, 2009 1:34 am

One other benefit I learned yesterday from the smaller dia. Master cylinder. I actually have enough braking power to stop the car on a steep hill even without the engine running. So even without the power booster energized by engine vacuum, I can still stop the car without having to stand on the brake pedal. That is a good safety feature.
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Re: Brake Up-grades

Post by SynthDesign » Mon Nov 23, 2009 11:01 pm

Great write up, Petros.

I have no idea how I missed it before I started mine.

It looks like the MR2 hoses are a bit shorter than the 92+ tercel units and didn't require modification. Nice.

I'm wondering if you have any pics of the caliper to knuckle mounting clearance. You made your spacers out of 1/8" AL(the equivalent of a thick washer), which I don't think is enough to clearance the newer tercel rotor and caliper on the T4WD hub properly. The rotor should be centered in the caliper bracket right(equal space on both sides of the rotor)?
If so and a thicker spacer is required, then the early MR2 calipers are a better choice possibly. A 5mm Spacers will require longer studs if factory Al wheels are used. With steelies it's questionable.
*88 and 89 MR2's have larger rotors, front and rear.

Are you gonna space out the rear to to match the track width?
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Re: Brake Up-grades

Post by Petros » Tue Nov 24, 2009 11:44 am

No plans to shim out the rear, most cars do not have the same front and rear track width anyway. I might have to if I ever do the rear disk brake conversion. The 1/8" shim is about 3.2 mm think, not a lot less than the 5 mm. Mine has worked perfectly since I installed it, and I appreciate the extra braking capacity every time I step on the brakes.

I have not tried to put stock steel wheels on since my conversion, it a looks like it will fit. If I have to install the studded snow tiers this winter I will know, they are are on 13" steel (but I think they hare honda wheels). Right now I am using the 14" MR2 alloy wheels, no clearance problems.
'87 Tercel 4wd SR5 (current engine swap project)
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Re: Brake Up-grades

Post by skyerunner » Wed May 12, 2010 2:40 pm

This is going to be my next project... I do a lot of driving in the mountains, but just yesterday coming out of Whitney Portal, CA, got the brakes so hot that I barely brought it to a stop with also using the e-brake, and I was definitely being cautious and using as much engine braking as possible. So, if I don't have access to aluminum shim and a drill press, you mentioned that AutoZone or someone might carry parts that work?
Also what year range of MR2 and newer Tercel parts might work? The newer tercels are easier to find in pull a parts.
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Re: Brake Up-grades

Post by takza » Wed May 12, 2010 5:20 pm

Or....you could buy some new Chinese rotors...Advance Gold pads....clean the dust out of the rear brakes and make sure they are adjusted up....etc.

I came down out of the Big Horns with 600 lbs in my wagon....using engine braking....but you CAN'T just use 4th or 5th...you need to drop down into 3rd. Let it run up to 3K...brake down to 2K or so...rinse and repeat. This cycles the brakes...keeps them cool.

Not a lot of fun when you realize you are close to NO BRAKES.

Temp gauge was real cool due to pumping all the air thru when I got down.
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Re: Brake Up-grades

Post by Petros » Wed May 12, 2010 7:30 pm

skyrummer,

Whitney Portal you say? Man that brings back memories, it has been 30 years ago that I climbed the east face of Mount Whitney with some climbing buddies in early spring (lots of snow still around). Also climbed some of the nearby taller mountains. Lone pine peak, Mt. Russel, Mt. Muir, Olancha, and many others. That is a long steep road back down to the town of Lone Pine, real easy to over heat the brakes, likely your rotors are cracked and warped too.

The early years MR2 front calipers from 1983 to 1986 will bolt on. The '87 and newer are larger, these might fit but do not know for sure since I have not tried it. The mr2 rotors do not work without very large shims and longer studs because the off-set is so large, but the newer Tercel rotors have the smaller offset, and work with the MR2 calipers. Any of the first gen MR2 master and booster will fit. You have to change the master with the booster. The '92 and newer Tercel (the one with the transverse engine) rotors and calipers should also fit with minimal shim. It might be possible to use thick washers under the rotors on the wheel studs instead of the making shims, but it will take some grinding on the washers because of the small side clearance.
'87 Tercel 4wd SR5 (current engine swap project)
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Re: Brake Up-grades MR2 Components Vented Rotors

Post by hberdan » Thu May 13, 2010 6:00 pm

This is a great article, with fantastic info, thanks Petros.
I've overheated my brakes in the mountains once, driving back over Loveland Pass from a ski day at A-Basin. For some reason I didn't fully disengage the parking brake, prbly 'cause at that time the brake light switch was not working. Anyway, the brakes were overheating by the time I headed down the east side--I immediately realized what had happened, and released the parking brake -- but there was no where to pull over safely. I just used the tranny to keep the speed down, allowing those rear drums and shoes to cool off for a while, and the fluid to cool too. Was not scary, but just tedious. Braking resumed after rolling down about 1000' vertical, a bunch of switchbacks and a couple miles... Spooky enough.
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Re: Brake Up-grades MR2 Components Vented Rotors

Post by splatterdog » Thu May 13, 2010 7:51 pm

Rear brakes are often overlooked for stopping concerns. While this upgrade can certainly help, basics are a good place to start if your car doesn't stop well. 80's toyota's often had leaking wheel cylinders. 25 year old adjusters can be sticky/stuck too. Calipers are usually in need of a good clean and lube. More so if you drive in a high corrosion enviroment.

Flush and bleed with something better than dot3 couldn't hurt either. Some of these wagons could still have OE fluid in them! Coffee anyone?

Never buy cheap friction! I do not/will not get pads or shoes from the zone. Chinese rotors are hard to avoid these days, some are better than others. Who knows what ingredients they put in their pads. Lead seems to be a primary material in most everything they make. haha

Great post! Might want to add a "do at your own risk" disclaimer since this is safety related mod.

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