Ironman Bike Pad, 140.6 Finishers Only

For me, the longer I travel, the less cushion I seem to want. I don't know why that makes sense for me, but I can't argue with my taint.

To answer your question though, I wore an ultra-thin chamois tri singlet for IM.

ETA2: Don't forget that a bike fit includes a size of chamois. If you wore a thick one for fitting and go thin, you need to compensate for that and vice versa.

First IM, I went with bike shorts and had all kinds of issues.  Second IM, I went with tri shorts and no issues. 

For the past 3 years, the ONLY bike shorts I have worn (regardless of bike) was a bib.  That was until yesterday.  I put on a pair of bike shorts to ride with friends.  I was miserable the entire time.  Time to get rid of them.  Tri shorts for me.  And the less padding the better--zoot has always been the best for me. 

There are tri shorts made for longer distances...they are sort of hybrid between tri and bike shorts.

Oomph brand with their distance pad is like that. They are more substantial than fleece tri short, shaped like bike chamois but not as big or thick and they are designed to dry quickly.

No choice on your poll for neither.

Ride lots in training and you'll figure out what works for you.

Answer: I don't even own a bike short...

good bike fit + right saddle is the key

I think fitness plays a key part in this.  If your sit bones start to hurt, it's probably not due to padding, but because your legs are tired and unable to push the pedals hard enough to take pressure off the saddle.  For me, lack of fitness, lots of coasting or light pedaling will tend to make my taint hurt even when wearing my Assos bib.

In my first IM I used a bib short with plenty of padding and had no issues and I was comfrtable (changed out of them for the run).  Been training in a bib short for all long rides for next IM - based on the comments here I may have to try my tri-shorts on my 100 miler this weekend and see if it is more comfortable... 

Some of De Soto's newer shorts have their "float pad" which is in-between the 400 mile short and a standard tri fleece.  And it's not bad to run in.

I'm always amazed at the number of people I see running the marathon in tri shorts!  If that is what you normally run in, than I guess that's ok but I run in running shorts. They are much cooler and more comfortable than tri shorts.  IMO it is well worth the investment of the 20 seconds it takes to change from bikng shorts (or tri shorts) into running short.

I also swam in jammers.  I had to change to biking shorts in T1 but I had to grease up the goods anyway so stipped the jammers for biking shorts.