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R&D: Gen 1 Brat 5-lug Conversion


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Hello everyone, 
I'm on a mission to 5-lug swap my 1981 BRAT. The goal is not to make any modifications to the existing BRAT components. If it has to be made or cut, it has to be removable. 

I've been following the Subarino videos and website for some time now. Dave said they had yet to do a lot of research on the Gen 1, so I didn't bother buying their kit. I've decided to make my own. 

I've purchased backing plates, rotors, and brake calipers from a 1994 Subaru Impreza(GC8). This era seems to be the most versatile for this type of swap, and parts are readily available. 

For reference, I've attached a 3D rendering of the 5-lug hub and backing plate centering ring. Remember, these are not final, and I still have some minor tweaks to make. 

I went to test fit my backing plate centering ring today. While the ring works, the backing plate hits the BRAT trailing arm/control arm, where the caliper bolts to the backing plate. 

I'm curious to see what others have done or if anyone has some ideas. I was under the assumption that the Impreza backing plate would work, but I just realized the Gen 2 cars have a different style trailing arm/control arm. 

I appreciate any input and plan to share my updates and final materials once done!

XT6 Rear Hub Reman v7.png

 

 

Rear Trailing Arm #2.jpg

Edited by stephen115
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4 minutes ago, el_freddo said:

If you can fit Gen2 BRAT brakes you can fit the Subarino 5 stud brake kit 😉 

There may be some slight differences with the hand brake cable etc. 

Do Gen2 Brat Brakes swap directly over? 

 

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5 minutes ago, el_freddo said:

If you can fit Gen2 BRAT brakes you can fit the Subarino 5 stud brake kit 😉 

There may be some slight differences with the hand brake cable etc. 

Do the gen2 Brat brakes swap right over? 

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9 hours ago, stephen115 said:

Do the gen2 Brat brakes swap right over? 

I don’t know mate, I don’t have a gen1 to play with and they’re quite scarce around this part of the world. 

It would be a cheap way to find out if the 5 stud conversion would fit - you’d need to ensure the rear stub axles fit the gen2’s drum brakes as the fabricated rear hubs adapt the EA81 stub axle to the EJ 5 stud pattern - if this works that’s a major hurdle over come. 

If not maybe the EA81 rear swing/trailing arm can be swapped in. Big maybe though. 

Once the rear is sorted the next thing is to ensure the front control arms can be reamed out to accept the larger EJ ball joint. 

From there it’s working out the master cylinder situation as you’d definitely want to upgrade that to EJ spec! 

Lastly and probably the most frustrating bit is sorting the front CV shafts. It’s probably best to go custom here for ease of just getting it done. 

There are ppl who have fitted EJ brakes to the Gen1 brat. I believe over here in Oz a fella had an emerald green one that had the brakes and an EJ fitted, I just can’t remember if it was EJ turbo. I’ll see what I can find. 

How’d you come up with the designs? You must be good with cad! Something I’d like to learn more about with complex components. 

Cheers 

Bennie

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14 hours ago, el_freddo said:

I don’t know mate, I don’t have a gen1 to play with and they’re quite scarce around this part of the world. 

It would be a cheap way to find out if the 5 stud conversion would fit - you’d need to ensure the rear stub axles fit the gen2’s drum brakes as the fabricated rear hubs adapt the EA81 stub axle to the EJ 5 stud pattern - if this works that’s a major hurdle over come. 

If not maybe the EA81 rear swing/trailing arm can be swapped in. Big maybe though. 

Once the rear is sorted the next thing is to ensure the front control arms can be reamed out to accept the larger EJ ball joint. 

From there it’s working out the master cylinder situation as you’d definitely want to upgrade that to EJ spec! 

Lastly and probably the most frustrating bit is sorting the front CV shafts. It’s probably best to go custom here for ease of just getting it done. 

There are ppl who have fitted EJ brakes to the Gen1 brat. I believe over here in Oz a fella had an emerald green one that had the brakes and an EJ fitted, I just can’t remember if it was EJ turbo. I’ll see what I can find. 

How’d you come up with the designs? You must be good with cad! Something I’d like to learn more about with complex components. 

Cheers 

Bennie

Thanks, Bennie. 

I've been doing a lot of research over the past few months. It all made sense until I realized the EJ backing plate hit the trailing arm of the gen 1 brat. That doesn't appear to be an issue on the gen 2. So a minor work around. 

RX and GL's came with rear disc brakes. If I can get my hands on a set of those that would be great. Then all I'll need to do is make the 5 lug hub and find a rotor that will work with the caliper. Shouldn't be too hard to find. 

Another thought is to make a 25mm spacer for the EJ backing plate. This would provide enough distance to clear the trailing arm. Which brings up another question. Would it space it too far to where the hub won't fit? All things I need to find out. 

 

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18 hours ago, el_freddo said:

How’d you come up with the designs? You must be good with cad! Something I’d like to learn more about with complex components. 

Cheers 

Bennie

I found an old thread on here that shared the dimension of the XT6 hubs. I then modified it from there to suit the Gen1. There are a lot of similarites. The spline count is the same 27T. 

Thank you! I use Fusion 360 and have been learning on my own for about a year now. Much to learn. 

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I was able to successfully print the backing plate spacer this weekend. It's 20mm thick and spaces the backing plate just enough to clear the BRAT trailing/control arm. I also printed version 2 of the rear hub. Everything mounts up nicely, I just need to install the caliper and check spacing. 

Edited by stephen115
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43 minutes ago, el_freddo said:

If you’re spacing out the backing plate you’ll need to space out the hub to line up the disc. 

No chance of modifying the backing place to avoid the swing arm? Got pics? 

Cheers 

Bennie

Correct. I did a dry test last night and I'll have to add a little to the hub to make it work. Maybe 5mm. See attached pictures below. Reached my photo limit so had to provide links. 

I do want to play around with modifying the backing plate. I'll look at that this week. 

Edited by stephen115
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  • 4 weeks later...

Well.. I've run into a little bit of an issue. 

I've developed the final version of the rear hub, but the only machine shop in town that can do internal splines wants $1,500.00... I'm not complaining about the price, I'm sure it's worth it for the maount of time they will have to put into it. However, there has to be another way. 

If only I knew the actual dimensions of the Gen 1 Brat rear CV splines I would be able to cut that fee in half. 

I've been working off the attached drawing that was posted on USMB over a decade ago by a guy in Australia. The issue I have is I don't speak mandarin, and the spline dimensions don't seem to be on the drawing. Unless I'm missing somthing. 

Thoughts? 

XT6 Hub Draft (2).png

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G’day Stephen, 

I checked out those pics, thanks for the permission to view them! 

I can’t work out what it is on the backing plate that fouls on the swing arm - as this is the reason for this whole effort isn’t it? 

Time to learn Mandarin? Or get one of those fancy translator apps?

Cheers 

Bennie

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