650b-converted Specialized Rock Combo

[franklyn]

I have been looking for a rugged winter bike that rides decently for a while. The GT Tachyon was an interesting machine, but the ride feel was lackluster. I picked up a 84' Specialized Stumpjumper, which weighs like an anchor and was also too small for me. After selling the stumpjumper I came across this Rock Combo. I updated the parts where needed, and converted it to use 650b wheels. This is the first 26->650b conversion I did (I have done several 700c->650b conversion in the past). Since I had a pair of V-brake levers lying around, and was able to sell the stock Shimano cantilever brakes that came with the bike, I bought a pair of V-brakes to use on this bike. The run-of-the-mill Tektro mountain v-brakes work with pads at the top of the slots. But the same brakes does not have enough reach for the fork, so I got some Promax P-1 BMX V-brakes, which have 35mm of vertical pad adjustments and the pads easily reach the rim.

I ran a couple of errands around town and the brakes work effectively and quietly. The bike actually rides very well and lighter than it is; it doesn't have the weighing-down feeling I experienced on the GT. I outfitted it with a rear rack and a Carradice Super C seatbag for now, and needs to put a pair of fenders on for the winter. The 36mm Hutchinson tires go on for now, but I also have a pair of Rivendell Fatty Rumpkins waiting for some trail action.

here are some pictures of the bike.

best,
Franklyn
Berkeley, CA

[Steve Chan]

   Those Rock Combos are interesting bikes, but are kind of rare and it wasn't clear what distinguished it from the lower end MB series. Any sense of what makes it feel lighter than the stumpy? Just the geometry?

   Steve

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[franklyn]

The 84' Stumpy is a klunker, and physically weighs more than the 89 rock combo; I didn't spend too much time riding the stumpy as it was too small, so don't know how it rides. Based on the UK-version of Specialized's 89' catalog, the Stumpies that year used Tange Prestige tubings, whereas the Rock Combo, along with the Rockhoppers, used triple-butted CrMo tubings; the hard rock used straight gauge stuff.

best,
Franklyn

[satanas]

On Sunday, December 8, 2013 11:47:34 AM UTC+10, franklyn wrote:

The 84' Stumpy is a klunker, and physically weighs more than the 89 rock combo; I didn't spend too much time riding the stumpy as it was too small, so don't know how it rides. Based on the UK-version of Specialized's 89' catalog, the Stumpies that year used Tange Prestige tubings, whereas the Rock Combo, along with the Rockhoppers, used triple-butted CrMo tubings; the hard rock used straight gauge stuff.

We used to sell Specialized back then. IMO the Prestige Stumpjumpers rode really well, bettered only by the S-Works Steel frames, which were basically unobtainable here in Oz. The Rockhoppers weren't too far behind the Stumpjumpers in ride quality IME. Diamondbacks from that era are also decent, Marin a bit stiffer but good geometry and handling.

Later,

Stephen 

[Greg Weiner]

Hi Franklyn,

I'm curious; what motivated the conversion? Were you hoping to improve some aspect of the RockCombo's handling, or did you just happen to have an extra set of 650B wheels on hand and wanted to experiment?

And now that you've converted it, can you comment on how it handles differently than with 26" wheels? Better, worse, the same?

Thanks,
Greg Weiner
SF CA

[franklyn]

Greg,

I only have 650b bikes/wheels, so when I started looking for a winter bike, I was only looking for bikes/framesets that can use 650b wheels. 650b-specific framesets that fit my criteria--steel, non-disc-brake, cheap, decent quality--are hard to find. I was going to look for another 700c frameset to convert when I came upon a set of pictures from the now defunct shop Renaissance (here is an example) depicting a 650b-converted 80's stumpjumper. I thought these 80's mountain bikes, some of them very well-constructed and can be very inexpensively acquired, are good candidates for my purpose.

So far from my riding around my office and doing errands, the converted Rock Combo rides noticeably better than my last beater bike--the GT Tachyon, which was built specifically for the 700d wheel size--very close to 650b.

Franklyn

[rcnute]

I have not tried a Rock Combo--but I love the "beater" Tachyon I got from Franklyn... :)

Ryan