Frankenbike

[gopha650b]

Hi There;
I recently upgraded to a full suspension trail bike with 26" wheels. My old hardtail is staring at me from the rafters of my garage. I have started to think about making it a 96'er single speed (just for ghits and shiggles), but I have a few questions.

-I assume to fit a 29 inch wheel all I have to do is change out the fork; correct??
-How badly will that affect the geometry of the bike? I'm not so much worried about "ride comfort" as I am about safety. Will changing the geometry affect the stress points in the frame? I plan mainly to use it is a "sometimes" trail bike and maybe just a cruiser for rides with the kids.
-Would I be better off making it a 650b6 'er?? is that safer?

The single speed conversion I can handle. I just thought I would see what peoples' thoughts were on changing the front end to 29".
Please share your thoughts good or bad...
Thanks
Mike

[Jisch]

I haven't done it, but I don't think it will put any unusual stress on the frame. If you neasure the axle to center (A-C) on your current fork, you should be able to figure out what a 29er fork might do to the geometry.

I have a rigid and a White Bros 80mm air fork (both 29er) for sale if you are interested.

[gopha650b]

Hi Jisch,
Thanks for your reply. Excuse my ignorance, I'm new at this; but axle to center (of what??)??
Also what are you asking for the forks respectively??
Thanks

[Jisch]

Oops, typo there, I meant axle to crown. You can just measure from your axle to where the steerer tube enters your bike frame. This is the variable distance when you change forks. If this distance changes too dramtically you will find the bike handling change for the worse - harder to keep the wheel down on climbs and a floppy feel when carving turns. I recently changed the fork on my 29er and I gained 20mm in the A-C distance and I really didn't notice it. Alternatively I have a 26er bike built for a 100mm fork and when I put a 120 mm fork on it, it really did change the way it rode in a bad way - backing the fork down to 110mm solved the problem - so small differences can wreak havoc on geometry.

I'd like to get $150 for the White Bros, $50 for the rigid fork (I'm not sure of the brand for the rigid fork, I'll check if interested). The White Bros has a Cane Creek crown race installed, I don't have a removal tool and in this case I think a removal tool would be necessary to not mess up the fork while taking it off (or just use a Cane Creek Headset and you'd be fine). The White Brothers fork works fine, I just wanted more travel for this bike.

John

[gopha650b]

Thanks again for the info. I think I will pass on the forks for now but will keep them in mind...
Happy Trails
Mike

[leebo]

Once you get your fork figured out, work on the cockpit. Think flat bar, and a lower rise stem than y0u have now.

[TheSlav]

like Jisch, I don't believe the increase in stress will really put the frame in any danger.

The increase in stress would be put mostly on the headset/headtube so to cover your bases you could upgrade to a beefier freeride headset.

I think possibly the most detrimental side effect to ride quality would be toe overlap getting out of hand, but you won't really know how that is going to pan out until you have the fork installed.

long story short...go for it.

oh and don't forget to report back.

[fog86]

I 69er'd my Surly 1X1 a few months back. The A-C on the stock 1X1 fork is just big enough to fit a 29er wheel and I swapped the stem for one with a lower rise, which kept the cockpit relatively unchanged.

At first, I felt a bit more tendency for the front wheel to washout in the loose stuff, but did not pin down whether that was due to a less aggressive tread profile on the 29er tire than I had on the 26er or the effective increase in head tube angle from the larger wheel. Now that it has been several months, I've either grown accustomed or sufficiently compensated and do not notice any adverse handling.

The increased bottom bracket height took a lot of rocks and roots out of play and the larger dia wheel has helped smooth some of the gnarlier transitions.

-Will

[gopha650b]

Hi There;
Thank you all for your input. I hadn't considered toe-overlap. That sounds like a trial and error deal, though. I think you have me convinced that this may be fun to do. Its going to be a budget build so it could take a few months. If and when it is completed I will keep you posted and post a picture. Its a cool light bike, I just hate to see it sitting there with nothing to do.
Thanks

[MMcG]

It would help to know the specific model frame you are trying to frankenbike. Some frames will be fine 69er-ed - others will suck balls no matter what fork you pair up with it. Trust me - I've experimented with various set ups on various frames. Some work great - others get all slacked out and you end up with major wheel flop.

[gopha650b]

The frame is about a 1996-97 Specialed Rockhopper A1 FS Comp.
Thanks

[gopha650b]

1996 Specialized Rockhopper A1 FS comp