1990 4 Piston Wilwood Caliper Upgrade

[CYBERFUKD]

I'm beginning my swap on my 1990 2WD. This is a racing truck, so we're upgrading to Cobra 13" rotor and wilwood calipers. This is going to be a learning process as I haven't been able to find much on this type of swap. The truck already has explorer discs on the rear. This is the biggest project I have taken on and any advice is welcome.

Given the difference in the piston size I'm almost certain a new master cylinder is in order. I've seen the recommendations for the old E-350 (I think). Going to need to figure that out.
RABS proportioning valve. I plan on remove this and replace it with an aftermarket.
Spindles: Pulled off a '97
Hub: Purchased new rotors for the truck and will plan to machine those into hubs. I haven't been able to find ANY Measurements. Would appreciate any info.
Adaptor bracket: we're going to fabricate the bracket out of high grade aluminum or steel. Aluminum is easy to work with but I do worry about corosion. We're going to mock everything up with wood and then order stock.
Braided steel lines will be on every corner.
For reference the cobra has 2 pistons with a total areal of ~3.2" these are 4.84", but clamp from both sides.
https://www.wilwood.com/Calipers/CaliperProd?itemno=120-13266&appid=0

 

[snoranger]

I’d think twice about aluminum for the brackets.
They tried that on the front brakes on the Saleen Explorer and failed. They all got recalled* and replaced with stock Explorer brakes.
It may work, but do you really want to take a chance with brakes?

*All except one vehicle that was shipped to somewhere in Europe... the owner refused to bring it in for the recall and made new brackets out of steel.

 

[CYBERFUKD]

Do you know why they failed? Almost every single bracket adaptor fabricator uses aluminum, so it’s not that crazy. However we currently have 33# 16” steel wheels with 245 tires on it so clearly weight on the corners isn’t the number one concern (these will be replace once know the correct spacing). Hopefully the spacing on the early 2000s Mustang GTs will fit. Theyre supposedly 17#. Which will make a significant difference in the unsprung weight and therefore handling of the truck.
I plan to get dream beams in the front. The rear is an 8.8 upside down.
Oh. And these are radial mount calipers. I believe the knuckle mounting points and caliper studs are all at 90°. We will grind them if we have to. We have precise measurements from Wilwood manuals and will just measure the knuckle. Drill and tap the brackets. Add spacers, voila. That’s why I’m not afraid of the aluminum, we’re just taking a block and drilling 4 holes in it. It’s gonna be F’n strong. Im pumped to get started.

 

[snoranger]

Why ask if you all ready made up your mind?

 

[CYBERFUKD]

Why ask if you all ready made up your mind?

I haven’t made up my mind. In my first post I said we’re still looking at aluminum and steel. I appreciate your feedback.

 

[snoranger]

I haven’t made up my mind. In my first post I said we’re still looking at aluminum and steel. I appreciate your feedback.

My main concern would be fatigue life. On a track only car, it’s a little different. You can fully inspect it before each use. On a street car, your not going to check your brakes everyday.

On such a small item I can’t see the weight difference meaning much of anything. Realistically, you’re looking at a 1-2 pound savings between the pair of brackets. Yes it’s unsprung weight, but it is a minimal amount.
My other concern would be dissimilar metals having the aluminum bolted to the steel knuckle could cause corrosion. That, combined with the heating and cooling the brakes go through could cause them to loosen up due to different expansion rates. I’m not an engineer or a metallurgist, so my advice is err on the side of caution.

 

[CYBERFUKD]

My main concern would be fatigue life. On a track only car, it’s a little different. You can fully inspect it before each use. On a street car, your not going to check your brakes everyday.

On such a small item I can’t see the weight difference meaning much of anything. Realistically, you’re looking at a 1-2 pound savings between the pair of brackets. Yes it’s unsprung weight, but it is a minimal amount.
My other concern would be dissimilar metals having the aluminum bolted to the steel knuckle could cause corrosion. That, combined with the heating and cooling the brakes go through could cause them to loosen up due to different expansion rates. I’m not an engineer or a metallurgist, so my advice is err on the side of caution.

Thanks. The steel and K.I.S.S. Does seem the best for long term reliability. Good point about the heat, that’s one I hadn’t considered.

 

[don4331]

Yet Wilwood makes their caliper mounts out of aluminium, with kits for F-350s.

Discussions on best alloy are all over the place - 5083 for best corrosion resistance, 7075/2024 for strength*, 6061 for best compromise. Then you get into the fancy Al-Li compounds when folks are trying to go light.​

​

*If you use 7075/2024, the bracket will need to be anodized or you will have corrosion issues.​

​

If you use steel for the bracket - haven't your just moved the dissimilar metal/thermal expansion issue to the mount/caliper interface instead of mount/hub? And there is far greater temperature delta at caliper/caliper is much more expensive to replace after corrosion than mount. Note: Mild steel isn't as strong as 7075/2024, and just about all the Al alloys are stronger than the cast iron of the knuckle. Just make sure you have enough thickness to ensure proper thread engagement of the mounting bolts/studs and don't over tighten.

Saleen Explorer bracket's issue was the holes to mount to the knuckle and the holes for the caliper studs were too close together. I mounted existing Ford caliper using what Wilwood refers to as "lug centric" brackets. My adapters are steel, but then all the other parts are cast iron, so aluminium didn't make sense.

When you turn the hubs, you want to stay just over 6" diameter - i.e. keep the flange on the rotor. If you machine off the flange, the studs will fail the cast. I'll see if I can find some pre-install pictures of mine.

 

[CYBERFUKD]

Yet Wilwood makes their caliper mounts out of aluminium, with kits for F-350s.

Discussions on best alloy are all over the place - 5083 for best corrosion resistance, 7075/2024 for strength*, 6061 for best compromise. Then you get into the fancy Al-Li compounds when folks are trying to go light.​

​

*If you use 7075/2024, the bracket will need to be anodized or you will have corrosion issues.​

​

If you use steel for the bracket - haven't your just moved the dissimilar metal/thermal expansion issue to the mount/caliper interface instead of mount/hub? And there is far greater temperature delta at caliper/caliper is much more expensive to replace after corrosion than mount. Note: Mild steel isn't as strong as 7075/2024, and just about all the Al alloys are stronger than the cast iron of the knuckle. Just make sure you have enough thickness to ensure proper thread engagement of the mounting bolts/studs and don't over tighten.

Saleen Explorer bracket's issue was the holes to mount to the knuckle and the holes for the caliper studs were too close together. I mounted existing Ford caliper using what Wilwood refers to as "lug centric" brackets. My adapters are steel, but then all the other parts are cast iron, so aluminium didn't make sense.

When you turn the hubs, you want to stay just over 6" diameter - i.e. keep the flange on the rotor. If you machine off the flange, the studs will fail the cast. I'll see if I can find some pre-install pictures of mine.

Thanks. I’ve been taking lots of measurements. I’m planning on cutting off where the rotor starts. Like you said justo over 6” the whole way. I think the bracket is gonna be at least

1” thick.

 

[pjtoledo]

do your wheels have enough clearance for the calipers? the shallow hat of the Cobra rotors will push the caliper deeper into the wheel.

 

[CYBERFUKD]

do your wheels have enough clearance for the calipers? the shallow hat of the Cobra rotors will push the caliper deeper into the wheel.

That’s a TBD. I may need to find another solution for rotors or wheels. Trying to stay away from spacers if possible.

 

[CYBERFUKD]

Yet Wilwood makes their caliper mounts out of aluminium, with kits for F-350s.

Discussions on best alloy are all over the place - 5083 for best corrosion resistance, 7075/2024 for strength*, 6061 for best compromise. Then you get into the fancy Al-Li compounds when folks are trying to go light.​

​

*If you use 7075/2024, the bracket will need to be anodized or you will have corrosion issues.​

​

If you use steel for the bracket - haven't your just moved the dissimilar metal/thermal expansion issue to the mount/caliper interface instead of mount/hub? And there is far greater temperature delta at caliper/caliper is much more expensive to replace after corrosion than mount. Note: Mild steel isn't as strong as 7075/2024, and just about all the Al alloys are stronger than the cast iron of the knuckle. Just make sure you have enough thickness to ensure proper thread engagement of the mounting bolts/studs and don't over tighten.

Saleen Explorer bracket's issue was the holes to mount to the knuckle and the holes for the caliper studs were too close together. I mounted existing Ford caliper using what Wilwood refers to as "lug centric" brackets. My adapters are steel, but then all the other parts are cast iron, so aluminium didn't make sense.

When you turn the hubs, you want to stay just over 6" diameter - i.e. keep the flange on the rotor. If you machine off the flange, the studs will fail the cast. I'll see if I can find some pre-install pictures of mine.

When you say keep the flange, what are you referring to. I was planning on just having a cylindrical hub...

 

[don4331]

Like this - turned Ranger hub

Not like this (Mustang hub)

You can probably shorten the "skirt" a little but you need it for structural integrity. If you turn it down to the 5.5" diameter of a Mustang hub the studs will crack the hub, and you will doing it again. The Ranger hub isn't thicker at the studs, like the Mustang hub is.

 

[CYBERFUKD]

Perfect. Thanks. I’m planning on keeping it at the ~6.1”

 

[Dirtman]

Brakes help slow you down.