Beisan S54 Exhaust Sprocket Hub Solution

[cobra]

One area I disagree is you don't know where in the fatigue life of the original hub you are. It could be 10 miles from cracking when you install the new oil pump disk. I would feel more comfortable replacing both parts, unless it was a super low mileage hub.

[sapote]

One area I disagree is you don't know where in the fatigue life of the original hub you are. It could be 10 miles from cracking when you install the new oil pump disk. I would feel more comfortable replacing both parts, unless it was a super low mileage hub.

I look at Beisan and OE hub design and they all have the sharp 90* corners at the base of the driving tabs. This causes stress raiser and crack. The tab corner should have radius which is common practice in metal making.
with radius base, to fully mate with the disk which should have chamfer holes. Even without chamfered holes the radius tabs still can insert but there is a gap in between hub and disk. The chamfered holes will have zero gap and less cantilever on the tabs.
Don't know if VAC hub has radius tabs or not.

[ethan]

OK, so Beisan new hubs don't have larger tabs to reduce clearance on the stock disk holes. It is very much the same result - tab to hole clearance - as stock hub on stock disk.
IOW, don't use Beisan hub on stock disk to reduce the holes clearance. Use VAC hub in this case.

But why wouldn't you just have Beisan drill your stock disk at the same time you purchase their hub? I can't imagine willingly giving VAC money at this stage in the game. The Beisan combination is even $50 cheaper.

[Obioban]

I look at Beisan and OE hub design and they all have the sharp 90* corners at the base of the driving tabs. This causes stress raiser and crack. The tab corner should have radius which is common practice in metal making.
with radius base, to fully mate with the disk which should have chamfer holes. Even without chamfered holes the radius tabs still can insert but there is a gap in between hub and disk. The chamfered holes will have zero gap and less cantilever on the tabs.
Don't know if VAC hub has radius tabs or not.

Given that a decade in we’ve seen zero failures with the Beisan solution, it seems sufficient

[Stilt]

I hate to be that guy but what's the relevance here? If there were issues in BS hub design, we'd hear about it .... I think we are safe so far.

[cobra]

I hate to be that guy but what's the relevance here? If there were issues in BS hub design, we'd hear about it .... I think we are safe so far.

No issues, just interesting discussion.
Raj was a very conservative guy that did insane amounts of research. He made it a point to understand why BMW did things the way they did, and learned that there is quite a lot of thought that went into every little part on our cars. He didn't want to diverge too much from the original design and accidentally compromise something else, so he just addressed the issue enough to stop failures and that was it.

[sapote]

Given that a decade in we’ve seen zero failures with the Beisan solution, it seems sufficient

I wonder for people that have been using Beisan hubs: is it mating to the smaller hole disk or anyone using it with the stock larger hole disk?
Of course the re-drilled smaller holes by itself would eliminate the tab breakage even if using with the "weak" OE hub, in theory.

[ethan]

I wonder for people that have been using Beisan hubs: is it mating to the smaller hole disk or anyone using it with the stock larger hole disk?
Of course the re-drilled smaller holes by itself would eliminate the tab breakage even of using with the "weak" OE hub, in theory.

Beisan says that you shouldn't buy their hub and use it with stock holes, so hopefully nobody is trying that. There isn't a tab breakage problem with either stock or Beisan hubs when used with redrilled disks. What's the concern here?