you are comparing S1 ally/steel to S2steel uprights, and the discussion was about the upright not the bearing bar issues with replacing them.
the steel s1/S2 uprights are the same design, and very poor because they lack the stiffness of the ally hub - look at the upright on an F1 car , or Le Mans - you can see the same ethos in the original S1 ally upright - stiffness is everything.... plus there is a simple bracket to get the toelink into double sheer which you cannot do on the steel - hence seeing several people bend or beak the bolt holding the toelink into the steel hub, and therefore the demand for original ally hubs to replace crap steel ones from people who have been pitched into the kitty litter from this issue.
The upper plinth bolts also fail fairly regularly with the only solution I've heard being to simply discard them periodically if you're on track a lot; if you take this approach with the outer toe link bolt too, then you're unlikely to break it unless you crash; if you crash something was going to break, and the outer toe link bolt is no worse than anything else. I replace my plinth bolts every other year, and replace any that are found to be under-torqued immediately.
To compare standard S1 alloy uprights with standard S1 steel uprights the bolt is in single shear on both; so unless you were going to fit the uprated toe link kit, the toe link arrangement is the same on both and both will fail/not fail much the same as one another. If you have alloy hubs and you're on track with sticky tyres then you have the option of fitting the uprated toe link kit which is an advantage, I agree.
I don't know much about metallurgy but I would expect the alloy to expand more than steel when hot. So whilst you can use this to your advantage when removing the old bearing, does it not also reduce the friction force on the bearing outer when the hub is properly hot (e.g. when on track with sticky tyres)? In this case the bearing might then shift or spin marginally in the hub and gradually fret away at the bearing tunnel in the hub. As soon as the bearing outer can move, the bearing will fail eventually and you won't be able to fix by replacing bearing. So whilst you can blame the loose bearings on people removing them without heat, you can also blame it on the hubs getting hot, I think.
I've seen this in action at Charade in France (an extreme example as it was a hot day, on an abrasive track, with people using sticky tyres). At the close of play I went around and wobbled the wheels on a load of SE S1 sheds (all old and thus alloy hubs). Each and every one had what appeared to be a loose bearing on several wheels. The next morning they were all tight. I can only assume this is down to the expansion of the hub, as the bearing itself will get tighter when hot, not looser, I think.
Regardless of whether you have alloy or steel you need to check the flanges when you replace the bearing - I've seen a couple of tapered ones, including on a car that is rarely tracked. Again, not knowing much about metallurgy I cannot say that the EP "harder steel" items are better than OEM or not, but given the OEM ones fail, I would fit the harder ones.
So the alloy hubs might be better if (a) you track it a lot (b) probably on sticky tyres (c) you fit the uprated toe link kit (d) you don't mind replacing the hub when the bearing tunnel is damaged. In all other cases the steel hubs are as good and have the advantage of being much harder to damage by hamfisted bearing swappery.
Cheers,
Robin
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