posted by j_crazy
my new company offers a Roth 401k and I'm 100% funding that option now and not putting anything into the pre-tax 401k route. the thought being i can use the principal i've contributed to bridge the gap from 50 (or whenever i retire) and 59.5 when i can start drawing the gains without penalty
It really needs to be based on a projection of your tax rate in retirement. If that's equal or higher than your current bracket, THEN you should fund a Roth. I've done a lot of analysis on this, and for a single person IMO that max is somewhere around $500k (in order to avoid RMDs making your SS taxable, taking into account property taxes, maybe mortgage interest and other deductions). Probably double that for married couples. Although lower if your house is paid off and you have low property taxes.
There are other games you can play, like massive backdoor conversions in the years between retirement and collecting SS (but, again, IMO you max your SS if you begin taking the lower amount at 62.5 because market gains meet or exceed the higher SS you get waiting longer to take the benefit). The taxable SS is a hard trap to avoid, because cap gains will also trigger that.
My employer also offers after-tax 401k contributions. Not every plan allows this, but I then immediately roll those over into a Roth IRA tax-free. Basically, I'm saving into a Roth IRA instead of a brokerage (which is otherwise subject to cap gains tax).
I still max out my pre-tax 401k contribution because I expect to be in a lower bracket in retirement. Not sure how long they will continue to allow backdoor conversions, but my plan in retirement would be to drain my brokerage first before collecting SS, and also backdoor conversions of 401k so my distributions are small enough to offset with deductions.