# 650b GT tandem



## muddybuddy (Jan 31, 2007)

Ok, it not a 650b its actually a 700d, which is some stupid size that only GT used for a couple years. But as luck would have it, it is more or less the same thing as a 650b, so now I have some options to keep it running. 

Here's my question: Its not suspension corrected and I have an ATC Racing fork I would like to put on it. I figure with the fork set up for four inches of travel, and with one inch of sag, would it be worth putting a 26" wheel on the front to get the front down 3/4" closer to stock and maintain handling, or am I just over analyzing it?


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## Trails4Two (May 12, 2008)

My guess is over-analysing. But you are missing the option of analysing your tire size and effect. You could go crazy measuring the height of a 1.95, 2.2, 2.35, and 2.5 tire and working that into the equation...Try it with the original and see how it feels, and save the big math for winter. Of course a 26 front would be easy to find, so you could try both. The ATC has one of the lowest ATC numbers anyway, so you won't be too tall.


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## muddybuddy (Jan 31, 2007)

What would the ATC distance be on an ATC fork set up for 4" of travel?


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## TandemNut (Mar 12, 2004)

muddybuddy said:


> What would the ATC distance be on an ATC fork set up for 4" of travel?


Approximately 469mm.


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## muddybuddy (Jan 31, 2007)

BigNut said:


> Approximately 469mm.


Really? Thats only about 2-1/2 inches taller than the rigid fork on there now.


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## DeeEight (Jan 13, 2004)

That's because most people don't think about the clearance that most rigid forks had over the top of a stock tire. You also btw have to allow for the fact a ATC being designed for a 26" diameter tire, won't neccessarily have the crown/brace clearance needed for a 650B/700D which are about 27.5" diameter.


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## muddybuddy (Jan 31, 2007)

The brace is adjustible. So I shouldn't have a problem there. But when I go through the fork I may have to figure a way to limit the travel to prevent contact with the crown. 

Ah, the joys of oddball projects...:madman:


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## Trails4Two (May 12, 2008)

*ATC adjusts*

Much will depend on how long your head tube is. I went through a year of playing with an ATC (26'). If your headtube is short, you will get away with a much lower standover. When we sold our ATC it went to a cannondale (long head tube) and we had to get leg extenders for it. It is a very easy fork to work on. You could create a travel limiter pretty easily, or they could make one for you. For the swap from 4" to 5", all I had to do was open it up and replace on rod. The bottom brace is adjustable (don't over torque the bolts though!) and if you are running a 20mm axle, Dean at ATC said you could actually just eliminate the lower brace. I was not brave enough to try that...


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## Plum (Sep 14, 2004)

muddybuddy said:


> The brace is adjustible. So I shouldn't have a problem there. But when I go through the fork I may have to figure a way to limit the travel to prevent contact with the crown.
> 
> Ah, the joys of oddball projects...:madman:


Hey Muddybuddy, did you end up swapping forks? I'm looking for a fork now for my GT 700d/650b bike as well and I'm interested to see if the longer fork worked out or not.

I'm thinking with the longer wheelbase of a tandem, that the longer fork A-C height won't be as much of an issue as it would be with a single bike, but then again, it might hurt an already compromised situation with the tandem handling.

I think I'm staying with a rigid fork for now, but I'll be going to a disc fork instead of the stocker.

Plum


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## muddybuddy (Jan 31, 2007)

Plum said:


> Hey Muddybuddy, did you end up swapping forks? I'm looking for a fork now for my GT 700d/650b bike as well and I'm interested to see if the longer fork worked out or not.
> Plum


I went through it and got it set up but needed a longer steerer tube, then got side tracked with other projects. Plans right now are to get it together by spring.


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