55.2-59 59 Disc brake conversion using Toyota parts

[BlouDon]

I intend attempting a disc brake conversion on my 59 Apache using Toyota parts, inexpensive & freely available from breaker yards (here in South Africa). It sounds like it should be a relatively inexpensive conversion - we'll see.... I should add that I'm hoping to be able to use the standard OEM 16" wheels that are fitted to the truck.

I'll document my trials and tribulations in this thread.

Whilst the drum brakes are acceptable, they do smell after a normal drive. Not sure if this is from lack of use or if my "laid back" driving style still pushes the brakes (I do not think I drive this truck beyond its capabilities), but I've decided that safety is not to be compromised on. This is why I fitted seat belts FWIW, and same applies to brakes.

Step 1: Convert from ball to tapered roller bearings.

Reading on this subject led me to conclude that it is indeed necessary to do this conversion to minimise lateral hub movement and thus ensure the brake pads of a disc setup will not be pressed away from the disc while not in use. Having the brake pads pressed away is really bad as this may result in braking not resulting from stepping on the brake pedal, requiring more depressing of the brake pedal.

A conversion kit RBK4759 arrived today from PerformanceOnline.com. Once I remove the hub, I'll first get the discs and calipers from a breaker yard and then I'll attempt the conversion.

The elegance of using the Toyota parts is that the existing hub can be used (saving $$$), I'm told, just by machining a tiny amount off the circumference of the wheel side of the hub to allow the Toyota disc (Cheap $$$) to slide over.

[dsraven]

check the inside diameter of the wheels against the assembled diameter of the disc and caliper assy. usually the issue with the old wheels is they are contoured differently on the back side so there is less room inside the wheel for the caliper and they end up rubbing the back side of the wheel or the wheel simply doesn't fit over the caliper to begin with. a newer wheel may fit and allow the same tire size. a toyota wheel may be the answer. if buying some wrecker parts you might ask about the wheels being included in the sale for a better deal if your old wheels don't fit over the toyota calipers. maybe even take an old wheel with you and check the fit at the wrecker before the parts are removed, then you know for sure. grab the brake master cylinder as well as the proportioning valve so the disc conversion uses all the balanced parts from the same vehicle. you would likely need to make the master cylinder fit your truck though. a lot of guys add power brakes at the same time. that can be a challenge if keeping the master cylinder under the floor because the booster needs to be smaller diameter. some guys will adapt a hydroboost down there instead or mount the booster on the firewall but then you need to modify the pedals etc, and put up with the booster under the hood.

[BlouDon]

Taking the spare wheel with and fitting it to the donor vehicle is a very good suggestion, thanks! I really want to retain the original look, so much that if the OEM wheels wont clear the calipers, I might reconsider the whole conversion idea. Although, the next question will be if a spacer between the hub and the wheel might solve the problem. The back wheels already sit 35mm wider each side due to the Ford axle I fitted, so front spacers might do good work then.

I am hoping that I won't have to fit a booster etc. But if I do, my E-type has ONLY a master cylinder that the brake pedal operates into (in front of the driver) and this then actuates a remote servo with a servo cylinder (mounted passenger side). I might use this setup if I do need a servo as then I fit the servo anywhere.

I realised with my C10 that like ignition, brakes is also a "system" - not just a bunch of parts thrown together.

[mr48chev]

I don't think you will have a problem with the 16 inch stock wheels. Although It looks like the diameter of the rotors might be 12.6 inches = 320 MM which might make it a tad tight.

Still I like that suggestion of trying one of your wheels on the donor rig before you pull the pieces off. I'd snag the caliper brackets off the donor too so that I had the basic bracket design and possibly be able to modify those brackets to bolt them on your spindles.

[BlouDon]

Step 2: Procure the parts required.

Today I purchased the calipers and discs which I'm hoping will do the trick. They come off a 2005 Toyota Hilux 2.7 VVTI. (I think you call them "mini trucks")

I did fit the wheel to the vehicle but that test was not 100% conclusive as the center hole of the OEM wheel was smaller than the what the vehicle hub required, so the wheel would not fit flush against the wheel face.

Step 3: Machine the hubs and fit the tapered bearings.

This weekend I intend removing/cleaning the hubs so I can hand them in on Monday for the required machining to allow the discs to fit over the hubs without interference. Then I will fit the tapered roller bearings and refit the drum brakes - just to see if this is possible.

[dsraven]

Take the rotors with you when you drop off the parts for machining. Clean down to clean steel at the critical areas.

[BlouDon]

Originally Posted by dsraven

Take the rotors with you when you drop off the parts for machining. Clean down to clean steel at the critical areas.

Yep, the plan is for a good rotor/hub fit such that "0" radial movement would be allowed. I suspect the Chev studs are smaller in diameter than the Toyota and thus the studs must only serve to retain the rotational position of the rotor, not in the radial position.

I did think of replacing the Chev studs with metric (to match the rears), but I want things to be easily reversible (a bit silly I know but there it is).

[dsraven]

the machinist is going to want to know the hole diameter of the rotor to ensure he machines the old truck hub to fit properly. I checked the napa site and this is the info I came up with for the hilux. hope that helps. looks ;ike the inside diameter of the center hole is 108mm.

Attributes
ABS Sensor Ring Included: No
Bolt Circle Diameter: 139.7
Bolt Hole Quantity: 6
Brand: NAPA
Center Hole Diameter: 108 mm
Directional or Non-Directional: Directional
Discard Thickness: 26
Grooved: No
Outside Diameter: 318.8
Solid Or Vented Type Rotor: Vented
Sub Brand: Ultra-Premium
Weight: 17.81

[mr48chev]

I don't see a reason not to go to studs that match the rears. That follows the keep it simple theory. That also keeps the lug nuts front and rear the same. One less headache to deal with.
You may need a spacer ring machined to keep the rotor hub centric That isn't a big deal except the money to pay to have it done. When you have everything apart and the calipers out that will all get figured out real quick.

[1project2many]

I did think of replacing the Chev studs with metric (to match the rears), but I want things to be easily reversible (a bit silly I know but there it is).

My advice as someone who has put more than enough work into making changes that can be easily reversed is... don't bother. It never happens. Once you modify the truck it never goes back. Either you or the next owner will drive it as-is for a number of years then decide to make more improvements further reducing the chance the vehicle will be returned to stock. A more realistic option for the brake swap is to secure replacement hubs and drums, crate those together with the brakes and backing plates, and clearly identify the parts inside in case someone truly wants to return the vehicle to original condition.

[dsraven]

1project makes a good point. stuff never seems to go back. good idea to source and machine a spare set to accept the roller bearings etc. it's more stuff to keep though and more money spent.
if you wanted to make the rear axle studs the same as the front you could check online, a site like hpaulin or napa etc. check the specs for the studs that are in the axles now, then look for something the same size at the press in area that also has the thread size you need. you could also drill the axles between the other studs to accept a stock old truck wheel stud, then remove the metric studs, the drums would still fit etc.

[mr48chev]

I don't see any need to ever go back to the oem studs on his hubs if he changes. In his part of the world Toyota pieces are easy to get and plentiful. Even for the if ever next person who owns it. BluDon just needs to (as we all should) put together a book on the truck that details all the items he has on the truck such as the lug studs if he changes them including parts numbers (receipts) for not only his later use but for someone else if case needs be. That can include exactly what the brake parts donor was and what mods were made to hub or rotor.

[BlouDon]

Today, I did some work on the Apache...

First thing was to remove the brake drum. Upon removing the drum I found the brake shoes were perfect, but the adjuster was installed the wrong way round. Glad I never tried to adjust the front brakes....

Then I found that the drum was riveted to the hub. Tried to grind the rivets away from the outside of the drum but concluded that I would have to drill them out. 8mm drill (5/16") did the job (after having drilled smaller pilot holes for accuracy. I also found that there was a very thin gasket (0.17mm) between the drum and the hub.

Test fitted the roller bearings on the hub and it all seems good.

Then I unbolted the backing plate from the spindle and started measuring things up. Drawing with today's measurements below.

I should add that the Performance Online kit comes with a very nice seal for the inside of the hub.

[BlouDon]

I should also add that I found the Apache hub diameter to be 171.8mm whereas the internal diameter of the Toyota disc was 170mm, so a tiny bit of machining of both faces will result in a very snug fit.

[BlouDon]

Today's work...

[BlouDon]

I intend having the bracket laser cut from 6061-T6 or 7075 Aluminium, 16mm thick.

[_Ogre]

great documentation for future use by others

has your truck been rebuilt previously?
from the looks of your drum, backing plate, springs and frame, everything is pretty clean
in michigan, everything is rusty, cuz we use salt on the roads in the winter

[BlouDon]

I recon my truck is a "survivor". Its had a light, thin blow-over.

Its present condition must be 99% original, but has had a very thorough clean. I also believe the inner wheel fenders were replaced by new. The truck spent most of its life in the "Karoo" and arid part of our country very similar (I think) to Arizona - extremely hot in summer, rather cool in winter (but still very dry) - hence very little rust. The underside of load bed tells the real story. The truck spent most of its 56k miles driving on dusty dirt roads - as can also be seen by the dust on the inside of the gauge cluster.

I still want to clean that...

[BlouDon]

Made a "bracket" from scrap wood to test fit everything.

First lesson was that the inner hole needs to be cut round on the sides to fit over the spindle.

Second lesson was that the lower bolt that holds the caliper to the bracket may have to be installed before the steering arm is attached to the spindle.

[BlouDon]

After having done the mock up, I've modified my bracket:

[_Ogre]

make sure you can bleed the air out of the calipers, i don't see a bleed screw on top

lower bolt that holds the caliper to the bracket

for the bolt and since you're familiar with cad, just rotate the bolt holes around the spindle center until you clear. it won't affect any brake geometry. you can also mount the caliper on back if it helps.

[BlouDon]

Originally Posted by _Ogre

make sure you can bleed the air out of the calipers, i don't see a bleed screw on top

Well spotted Ogre

I was using the right hand caliper in my mock-up. The left hand caliper (that I should have used) does have the bleed nipple at the top :-)

[57tailgater]

Your bracket drawing is looking better. I'd also put radii (like you did inside around the king pin boss) where your caliper mounting tabs are to reduce the chance of stress risers that can cause cracking. In addition, you said you were going to use aluminum for the brackets. I don't believe I have seen anyone do a kit like this with aluminum - it's always been steel. There are a lot of braking forces here. Have you considered that?

[BlouDon]

Quite right about the radii on the caliper mounts. They should also have radii. That is where either my CAD software won't allow me to do it, or its me not knowing how to do it. I tried to cater for that with the one annotation specifying "all corners" and will verbally instruct the laser cutters to add them.

I am NOT a mechanical engineer. I do have some electronic background, which is why I got this recommendation from a friend who is a highly competent, experienced, mechanical engineer. If it did not come from him, I would have disregarded the recommendation outright, but coming from him, I have no qualms accepting and implementing the recommendation.

[BlouDon]

Originally Posted by 57tailgater

I'd also put radii (like you did inside around the king pin boss) where your caliper mounting tabs are

Howzat?