Running two different sized wheels, at the same time...

[Dlevy05]

I know this forum is more geared towards road biking, but we do have an intelligent community of members, so I figure maybe someone either knows the answer or knows where to point me, to find one. Here's a question that's been floating around in my mind for the past few days, as I've begun to piece together a trail-bike based on a SOMA groove (26" wheels).

I remember (about 15 years ago) the "modern free-riders" of the time, were putting 24" wheels in the back, and 26" up front. The difference in wheel size apparently made the geometry of their frames more relaxed, the ride more forgiving, and made tasks like wheelies much easier. (If there's more to it, please fill me in.)

Lately, I haven't seen may people running different sized wheels, and the 24" wheels seem to have taken a backseat entirely to the 26's.

Has anyone here run a setup with a 26" wheel in back, and a 29" up front? If not, has anyone seen this, or heard of it being done? What was the end result like? Speculations are welcome, too. I don't have an intention of doing this myself (unless I have a lot more time and money on my hands, and the will to experiment) but I'm curious, nonetheless.

[pitcrew]

Yes, there are some bikes that are set up w/ a 26er rear and a 29er front. Generally referred to as a 69er.

When running a 24" rear wheel, the difference was generally made up with running a larger tire.

[Dlevy05]

Forgot to mention, Trek had a 69er, for '07, and '08. It's been discontinued since, but got rave reviews from what I've seen.

Something interesting though: the head tube angle was around 69 degrees. Relatively slack. If one were to modify a 26" bike with a HT angle of around 72, they'd probably wind up close to the geometry of the Trek 69er.

[RPS]

Speculations are welcome, too.
Why not just design in the desired geometry without such compromise? :confused:

[old_fat_and_slow]

That's the way they ran 'em in the old dayz.

What's the big problem?


http://i461.photobucket.com/albums/qq332/catchernrye/jokes/highwheel6v.jpg?t=1297463259

[fourflys]

other than for a downhill run, not real sure why you would want this... I have enough trouble keeping my 26" down in the front on some of the steeper stuff, I can't imagine a 29 in front and a 26 in back... The Trek was a Travis Brown creation and I think was a very specific purpose (dual slalom???)

[daylate$short]

I have seen a number of people do it. One option is to use a rigid front fork with approximately the same dropout to fork crown height as a 26" suspension fork so the geometry doesn't change as much. The claimed benefits are that the front wheel rolls better over stuff and has better grip, while the 26" rear wheel keeps the rotating weight down and gearing the same. Plus you can pick up some really nice 26" frames right now pretty cheap.

Personally I prefer a full 29er, but If I were going to do it, I'd put the bigger wheel on the back so I could just coast downhill most of the time. :)

[RPS]

I also prefer my front and back wheel the same.