My guess would be the longer bolt method like the Sugino Mighty Tour but you can go down to 28T on the 99. I have one in front of me. 52-49 double and my intention is to add on the 28. The rings are still made and Sheldon has them.
Previously people (Sheldon included!) have registered protest against the half step plus granny but I don't understand it. For a serious touring bike, no kickdown gear can be low enough in case you get tendonitus or the weather is really damp in the middle of nowhere on steep slopes. You just have to ride and that's that. As to the big rings, the feeling of having the perfect gear beats the nuisance of double shifts any day.
Joe B-Z
GNNJ
> Finally conceding to age and the advantages of triple cranksets. Can
anyone
> tell me how the inner ring attached on the Stronglight model 99? Were the
> triple arms the same as the double, and you simply bolted on another ring
> using longer bolts, with the inner ring supported only by the bolts? Or
did
> triple arms have a deeper "notch" on the inside of the spider, so that
both
> middle and inner ring were supported on the inside by the spider? Also,
do
> you have to use Stronglight triple chainring bolts or will TA or maybe
> something more generic work? I have several mod 99's, but I've never set
> one up as a triple.
>
> Regards,
>
> Jerry Moos
> Houston, TX