I browsed these up while looking for something else on flickr:

http://www.flickr.com/photos/95459034@N ... 7/sizes/l/

http://www.flickr.com/photos/95459034@N ... 1/sizes/l/

For all the madness of a unique wheel size (and I say that as a Moultoneer) the Tachyon looks like a fun, versatile bike. Anybody here ever ride one? How did the flipflop stem work? Like an Ahead stem on a quill convertor?

In case anyone's tempted, there's a Continuum closing today on eBay.de

http://cgi.ebay.de/ws/eBayISAPI.dll?Vie ... 0225982523

"the seating position of a mountain bike, but all of the advantages of 700D Cross-over wheels ..."

Ironic that the 650B craze might actually make these viable again.

a strange brew indeed - now of course, I bloody well want one...

700D was one of Bill Duehring's best ideas while he was the VP of Product at GT. Problem was that the industry was so damned competitive back then that no other bike lines hopped on this idea. If they had there wouldn;t be such a big rooha over 650B. 700D ERD is 587 and 650B ERD is 584. I haven't tried to see if a 650B will stretch onto a 700D rim. GT had three Hybrid models with 700D wheels. The Tachyon was the dropbar model with the flip flop stem and Suntour Command shifters. It was a bike before its time. (I know a guy that toured Africa for a year on one). The Continuum and Cirque were upright handlebar models. The Cirque had a 7005 aluminum frame w/Shimano 700CX components and the Continuum was the lower end chromoly model. GT had Araya produce the RM-20 cross-section rims for these models and IRC produced three models of tires in the 700D size....a 1.4" slick, 1.4" connecting ridge knobby and a 2.0" knobby. GT also produced their Quatrefoil Tandems in the 700D size. I have a 92 model in fact and use it with both the slick tires and the 2.0 knobby's. The 700D tires still show up on eBay once in a while. I managed to find a couple spare pairs this past year. I do want to try a 650B just to see if it fits. If you were to pick up one of these GT 700D models and did need new wheels, tires or rims one could easily switch over to 650B wheels without having any issues with the brakes hitting the rims.

looks vaguely familiar to me......

always wanted a tachyon, scarce bike int UK I believe

heres one of the German forum

Thanks for the comments and further information. I've always had a soft spot for drop-barred mountain bikes, and some of the variants that appeared (Specialized Rock Combo, Bridgestone XO) before the industry decided that a hybrid was a heavy 700c flat-barred roadster with mountain bike gears and brakes. Those were more creative times.

My first mtb - a GT Team Avalanche - was lined up for a conversion to drops (and a trip to Africa) but was stolen before I could carry out the plan. I think if I'd known about the Tachyon at the time I would have been tempted, but the 700D thing would, I hope, have scared me off.

I'm still stunned that I accidently built a bike almost excatly like this and had been riding it for the last 6 years or so..... (I'd never seen an mtb with drops before let alone the tachyon)

I'm gonna build one - a mate has an older cromo GT, I have the flipflop stem and forks - expect a 26" wheeled version on these pages soon.

I now have a GT Quattrafoil Tandem with 700D wheels that needs an original fork......just incase someone has one kicking about!

A few guys at MTBR have tried the 650B tires on the 700D rims and they do bead up ok.

interesting, can you tell me exactly which amberwall tyres are in the pic? They look good

You can still buy the rims on ebay - rm20 700Ds (I almost bought them before I realised they weren't 26" as I was about to hit 'confirm'!). The odd smoke tyre comes up every now and then too.

That purple bike is tidy and the fact that the 650B tyres will fit should make these a great bike to own.

Seen the odd Tachyon for sale didn't out em cos
didn't think anyone wouldbe interested.

The didn't make smokes to fit the 700D rim. All the original 700D tires were made by IRC. They made Smokes in the 700x45C size to fit the Overdrive and Overdrive Comp from Diamond Back that were around at the same time.
Araya made the 700D rims in both the RM-20 anodized and RM-17 silver, with both versions 32 holes.

Those are NOS IRC 700D x 2.0's.. The also made a 700 x 1.4" connecting ridge knobby and a 700 x 1.4" 90 lb slick