any subaru front hubs fit for AWD BRZ/FRS?

[aesthetect]

Short version:
Building an all electric AWD BRZ or FRS. Does anybody know if WRX (or any other model subaru) hubs will bolt in to FRS/BRZ steering knuckles? They look extreeeeeemely similar but I can't find any more specific info.

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Detailed version:
I'm planning an electric car build which will be all wheel drive. BRZ/FRS is on my short list of donors to use as a foundation, being a good fit as far as space needed for batteries and motors - significantly better than WRX actually (since i know that will come up ).

problem is obviously front drive/axles/knuckles - most specifically awd hubs fitting in the knuckles or not. doing some research the BRZ/FRS knuckles and hubs look almost identical to all other similar year subarus, biggest difference is that it is rear steer, compared to wrxs etc having steering rack in front of xmember. so swapping knuckles straight away wouldnt work (and swapping sides will screw up ackerman).

main question then is will any other AWD subaru hubs potentially bolt in to BRZ/FRS knuckles?? does anybody have any info on the hub bolt pattern or bearing diameter/length measurements? worst case is to fabricate front knuckles which is doable but just that at that point other chassis become better options.

it does look like there is room to clear the axles, at least not with any more forward/rearward angle than other subarus have on front axles. chopping/channeling subframe or rails is no problem of course, but would seek to retain the factory geometry/components.

next option would be swap WRX knuckles if possible and just put steering rack in front but would ultimately depend on other similarities in balljoint/upright geometry etc. thoughts on that?

have searched and the only thing ive found was actually on this site - where prime motoring built a AWD FRS using RB26, and posted the info below, but I have not gotten any response to emails/messages from them. they indicate having built custom coilovers, hubs and wheel bearings, i presume they mean the whole knuckle, not quite clear in photos (maybe you guys have a better eye). they also abandoned the AWD and swapped in a k-series or something before too long and then sold it so their experience makes me a bit unsure.

Originally Posted by PrimeMotoring

Before everyone asks how we got the four wheel drive to work. Let me just say it involved A LOT of cutting and welding. The center diff and propshaft require a nice piece of passenger side floor to be trimmed. Subframe had to be boxed out and modified to make the axles clear with enough room to allow them to move when cornering. Custom coilovers were made along with hubs and wheel bearings.

THANK YOU!

[ichitaka05]

Originally Posted by aesthetect

Short version:
Building an all electric AWD BRZ or FRS. Does anybody know if WRX (or any other model subaru) hubs will bolt in to FRS/BRZ steering knuckles? They look extreeeeeemely similar but I can't find any more specific info.

Toyota made 86X to test it as a Rally. iirc they used FA20 from current WRX and still made it AWD. Issue w this is front axles gotta be "Y" shape instead of "T" shape like other AWD Subaru. So I'm assuming you can equip current Impreza hubs & bearing (if you wanna keep it 5x100 bolt pattern)

[aesthetect]

Thanks! I don’t follow you on the axle shapes though, usually they’re just straight with two CV joints (?)
ie: (diff) =o——-o= (wheel). Did you mean control arms?

[fatoni]

No offense intended but if you have to ask these kinda questions on a forum, maybe you shouldn't dive into such a complicated project.

[ichitaka05]

Originally Posted by aesthetect

Thanks! I don’t follow you on the axle shapes though, usually they’re just straight with two CV joints (?)
ie: (diff) =o——-o= (wheel). Did you mean control arms?

K, let me explain lil better. Using crappy Window Paint lol
Most Subaru engine trans setup looks like this:


Red box is the engine. Blue box is the trans. You see sticks sticking out on both side are cv axles & on the bottom is the drive shaft. This is why it’s called “T” design.

If you’re going to put electric motor (single motor design instead of each wheel motors design) in the same spot as current BRZ area for trans to be able to connect to the hub, it’ll become like this:


As you can see, cv axles need to be angled more and looks like “Y” instead of “T”. Of course current WRX/STI are more toward “Y” than “T”, but it’s not as an extreme as if you try to do AWD on BRZ. This why you don’t see ppl try to make AWD BRZ using WRX engine & trans, cuz they have more stuff to worry.

To resolve that, you’re more than welcome to try like GTR (R32~34) style trans... but it’s not cheap and gotta do hellova a lot more work.

[aesthetect]

Ah I follow you (thanks very much for the drawings!) - I should have said, won’t be using an OEM style transmission at all - so front ‘diff’ placement is an entirely different and open matter here. the only limitation or decisive factor is the rear control arm mount, and making sure the axle misses it, so axle will have a slight angle rearward for this.

Originally Posted by ichitaka05

K, let me explain lil better. Using crappy Window Paint lol
Most Subaru engine trans setup looks like this:

Red box is the engine. Blue box is the trans. You see sticks sticking out on both side are cv axles & on the bottom is the drive shaft. This is why it’s called “T” design.

If you’re going to put electric motor (single motor design instead of each wheel motors design) in the same spot as current BRZ area for trans to be able to connect to the hub, it’ll become like this:

As you can see, cv axles need to be angled more and looks like “Y” instead of “T”. Of course current WRX/STI are more toward “Y” than “T”, but it’s not as an extreme as if you try to do AWD on BRZ. This why you don’t see ppl try to make AWD BRZ using WRX engine & trans, cuz they have more stuff to worry.

To resolve that, you’re more than welcome to try like GTR (R32~34) style trans... but it’s not cheap and gotta do hellova a lot more work.

[aesthetect]

Originally Posted by fatoni

No offense intended but if you have to ask these kinda questions on a forum, maybe you shouldn't dive into such a complicated project.

I’m just trying to figure out if AWD subaru hubs can be easily made to fit before I commit to a chassis. because it looks like they could, but if not and I have to make custom knuckles I have other chassis options I would rather go with. Figure people here might have had some of these partin their hand or side by side at some point and that knowledge would help greatly in this planning phase.

[ichitaka05]

Originally Posted by aesthetect

Ah I follow you (thanks very much for the drawings!) - I should have said, won’t be using an OEM style transmission at all - so front ‘diff’ placement is an entirely different and open matter here. the only limitation or decisive factor is the rear control arm mount, and making sure the axle misses it, so axle will have a slight angle rearward for this.

If that's the case, then yeah front control arm will be an issue... but hub and most of other parts can be replaced w other Subaru cars.

GL

[aesthetect]

Originally Posted by ichitaka05

If that's the case, then yeah front control arm will be an issue... but hub and most of other parts can be replaced w other Subaru cars.

GL

So hubs can be interchanged??

But even dodging the control arm mount it looks like the angle on axles won’t be any worse than on the ‘Y’ shaped subaru arrangements you mentioned fortunately though.

[ichitaka05]

Originally Posted by aesthetect

So hubs can be interchanged??

But even dodging the control arm mount it looks like the angle on axles won’t be any worse than on the ‘Y’ shaped subaru arrangements you mentioned fortunately though.

Chances of changing to any Subaru 5x100 hub (like current Impreza other older Subaru models) are high. Cuz iirc current hub is same design as current Impreza hub. Only difference is one is close holes vs other is open holes (for bearings).

[aesthetect]

thanks! they really look extremely similar which i think is what led me to feel the need to dig deeper and try to find out for certain. honestly I figured it would something like common knowledge but of course there are substantial obstacles to setup AWD in these cars with any sort of regular powertrain so I guess that’s why not

[aesthetect]

Originally Posted by ichitaka05

Cuz iirc current hub is same design as current Impreza hub. Only difference is one is close holes vs other is open holes (for bearings).

sorry just re-read and FYI they are definitely significantly different just in that the BRZ is the only subaru thats rear steer (steering rack behind front wheel axis); but again, the hubs themselves look extremely similar...


anyhow, I'll give it up now and keep moving forward, I just thought someone might know this offhand. thanks for your help.