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So I've been needing some new struts all around for a while now, and I decided that dropping a few hundred into stock parts might not be worth it so... BC Racing coilovers inbound!
The problem is that the fronts are a weld on body, which requires cutting the factory strut tube (same as T3 but BC has you do it yourself). Being that I drive an SA, I'd rather not cut up the less common SA strut tubes if my extra FB ones (S2 so they're still small bearing) will work just as well. If I recall correctly the only differences are up top and result in the SA assemblies being slightly taller. Is that the case? Would I be okay using the FB assemblies for the weld on coilovers? How much of a height difference are we talking? Any input appreciated.
Maybe buy a set of used S3 struts off the classifieds or epay? So you can have big bearings. Why go through all the trouble for smaller SA bearings?
When you get the BC kit all you reuse from your originals is the cast knuckle/spindle. You cut off and throw away the tube and spring perch. So the difference in height (SA tubes longer than FB tubes) is irrelevant. You're fine tuning the height front and rear anyway. Throw away those inferior SA struts.
Haha, okay hold on. I want to keep the SA struts intact since they're less common, that's really all I'm saying there. And yeah, I was essentially just asking about differences on the cast knuckle/spindle as indeed that's the only part reused. As long as those are the same - which it sounds like they are - that's all that matters.
As for S3 big bearings... I've heard a few times that the big bearing front setup is more prone to heat cracking, cracking in general, or just something to that extent. Now that's only something I've heard a couple times, no real world data on my end. That said, in the same discussions I've seen people say that both are basically equal when it comes down to stressing them, perhaps failing in different ways though. Again, I don't have a record of the conversation or anything, it's just something I remember hearing. Given that, I see no real benefit to going to an S3 setup, particularly when you consider I replaced the bearings, rotors, and all that fun stuff not even a month ago. So anyway, that's what I see. I also already have an extra S2 set just waiting for something to be done with them. Oh and I believe the T3 small-big-brake-kit only currently fits the small bearing spindle, although I believe they're working on a big bearing version as well.
Just for the sake of curiosity, what is the difference between the SA and FB upper strut assy? I want to say there was a change with the bushing/bearing design up top... I could be completely off though.
cut up the SA's... they changed the style bc the SA's were actually dangerous. unless they're in minty condition and you're saving them to sell to someone doing a period correct SA restore or put on display somewhere.... i'd hack em up my dude.
If you have the S2 struts, hack on those. Someone may want the SA ones or you may change your mind. The differences are the tube length as mentioned and the strut top, the shaft is different going into the strut top bearing. Otherwise identical I think. Are your SA struts original, as in never been opened or upgraded with inserts?
Never had an SA but I also have never heard about a danger. Only that they are slightly longer (14mm ?) And the rod is a different size (uses a different top hat / mount). And of course the small-bearing spindle which I assume is thinner than later big-bearing spindles.
The plot thickens! So what's dangerous about the calipers?
they dont work well, were known to fail. i'll see if i can find a few articles about them - there's a reason they were changed to the '81-'85 style. gimme a few, maybe tomorrow. i know i can find it
Ah ok.. I didn't think there was a real design difference. The calipers however are wedge style. Instead of the caliper riding on a couple pins/shafts/dowels it slides along a dovetail (more or less) Dovetail joints probably have a lot more surface area to have friction issues.. My guess. I had wedge calipers and found new calipers and swapped over to them.. I didn't really notice a difference but I guess this was another bean counter oversight made by Mazda. Hopefully sh00bs will have more details tomorrow or others will chime in.
Yeah the early SAs had old style wedge calipers but I have never heard about them being dangerous. They are harder to keep working right because the wedges are exposed to a lot of elements and not protected by boots like the pin setups in later SAs and 81-85.
Interesting note about the calipers. Thankfully I have the guide pin style (same as the FB's but with M10x1.25 brake lines) so that's a non issue.
Responding to t_g_farrell's question about whether they've ever been opened; no not to my knowledge. I have never done them, before me the car sat for 16 years, and I really doubt they would have been done before that. Of course over the three years I've had the car I've definitely noted they were failing, I simply didn't want to replace them until I could go to coilovers. At first they just squeaked, but now we're getting to the point where upon coming to a stop the car rocks back and forth a couple times, so yeah, not good.
Anyway, thanks for all the responses. Today I dug out the donor parts - they're looking a little rusty!
Overall not too bad, but the cast porition is certainly going to need some clean-up. Both rotors spins freely and without noise so I think we're in good shape here, although I'll still pull them off to make sure the bearing surface isn't damaged. Is there any reason why I shouldn't reuse the bearings on the SA (which will be less than three months old) when transferring everything from my current strut assemblies to the new ones? Seems like there wouldn't be an issue, just curious if that raises a flag for anyone.
SA struts are different in 2 ways than the later S2 FB design (*apart from obvious bearing sizes, which has been covered):
1) the strut tube on an SA is longer than FB by a small amount. With Tokico inserts, they give you a longer bushing to go under the gland nit to account for this difference. Both struts use an oil bath for better heat conducting from the insert to the strut body to dissipate heat.
B) the Strut Mount on SA does not turn with the strut. There are flats on the strut rod which mate with the Mount and prevent rotation. The FB Strut Mounts use a bearing to allow the strut rod to rotate in relation to the Mount. Unsure why this was changed, but could be due to better strut insert designs which don't work well when you cause the piston to rotate within the insert body.
This is why the Strut Mount stock numbers are different between SA and FB,
The OEM SA struts didn't have inserts, it was an oil filled chamber with a pistom rod in it if I remember right. Reading the manual, some SAs had cartridges. I know mine had the piston rod in oil before I installed cartridges. Its an old wives tail that the cartridges need oil added around them when reinstalled. The FSM explicitly states to skip steps 1 -5 (which includes adding oil) for struts with cartridges. Thats why I was asking about your original struts.
I've thought about going back to those original strut setup just to play with different weight oils to adjust the damping. Would be interesting.
Is there any reason why I shouldn't reuse the bearings on the SA (which will be less than three months old) when transferring everything from my current strut assemblies to the new ones? Seems like there wouldn't be an issue, just curious if that raises a flag for anyone.
As long as you keep the bearings matched to the rotors they were on the spindle with, should be no problem. The races get bedded in with the bearings, the spindle, not so much.
they dont work well, were known to fail. i'll see if i can find a few articles about them - there's a reason they were changed to the '81-'85 style. gimme a few, maybe tomorrow. i know i can find it
welp i may be bitting my tongue on this one and i feel foolish aha
i woulda put money on that i saw an article stating the wedge style was dangerous and there was a reason for the change. i tried searching and made a post on the 1st gen fb page without any luck. oh well, i'll take the L on this one i suppose,, SA brake on !
08-25-20, 02:10 PM
