Join Date: Jan 2006
Location: New Mexico, USA
Bikes: 19 road bikes & 1 Track bike
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Any Shimano 9-speed cassette would fit the 8-speed hub, if you already have 9-speed barend shifters which you plan to use. Otherwise, I suppose you could change out all the spacers on the 8-speed cassette to 9-speed spacers and you would just have an additional non-functioning notch in the indexing.
With a new 9-speed cassette you could also add an 11 tooth cog for your top gear and still have all the other cogs the same as are currently on the 8-speed. --- By doing this, using a 53t chainring, this would give you a 126 inch gear versus just the 116" now on the 8-speed... or, put in other terms, pedaling at 100 rpm you would hit 37.7 mph versus just 34.5 mph with the 12t cog when pedaling at the same cadence. .... AND, ironically, most 9-speed cassettes are actually lighter than comparable 8-speeds.
Any crank you want to use should work. However, I've seen some TT bikes set up with 42x52 rings rather than the rider's usual 39x53... just because he did not need the lower gears which the 39t chainring offered, and also with longer crank arms than the rider usually used (175 mm versus 170). Unfortunately, I've only seen chainrings correctly paired with these two combinations - at least for Shimano.
David Millar used only a single 53t chainring and no front derailleur. However he also screwed up at the start of that particular TT race and accidentally slipped the chain off without the front derailleur to catch and re-align it, so he actually lost time in spite of lightening his bike.
By the way, that stem on that bike looks like it is setting the bar rather high for a TT bike... but that should be easy enough to change out.