Adjustable dropouts for 24/26 inch frame

[Blacklabbikes]

Hi all.

I'm putting together a build list for a kids MTB that can grow a bit with the rider. I was hoping to find some 27inch/29er swapouts a-la santa cruz. Anyone know of a source? If all else fails it looks like a paragon slider will do the job perfectly well, just look a little less neat.
I'm going to run a rigid fork and allow for sus-geometry if I can get it to look a little less weird.

It's the first dual-wheelsize bike build for me so any tips on this kind of build welcome.

[Andrew R Stewart]

I would think the hubs of both 27.5 and the 29er wheels you might be running could be the same, therefore the drop outs could work with both wheel sets. I also would thing the BB drop (or rise with the 24" wheels) will prove to be a compromise point. As I understand the 27.5(+) and 29er swap arounds the outer diameters are very close, so BB heights remain similar as too the fork crown/tire clearances. But the proof in in the actual tire measurements you plan to use and the hubs specs. One can always build up the wheel sets to match hubwise. Andy

On a second reading of the OP I'm unsure if the plans are for 24" and 26" wheel swaps or 27.5 and 29er swaps. Sorry if my above reply seems a bit confused, because it is.

[Blacklabbikes]

My mistake.

I'm making a 24/26 inch wheel bike. I was wondering about using some dropouts off a 27/29 inch bike to help keep the rear triangle proportions tight.

[Andrew R Stewart]

I guess I'm still confused. What do the drop out choice have to do with stay length?

So two different wheel diameters on the same bike at the same time? I'm curious of your reasons. I know why others have done so and excepting rider fit issues (Terry bikes is the most common) the others chasing specific handling/ride quality goals didn't do this for long. Perhaps the Cannondale in the late 1980s (or was it the early 1990s) was the best known of this reason. Andy

[Blacklabbikes]

I am not thinking of running two wheel sizes at once. I'm building a frame to use 24 inch wheels to start with followed by 26 inch wheels when the child gets a bit bigger.

The point of having different dropouts for the two different wheel sizes (Santa Cruz Chameleon 7 Dropouts | Jungle Products Ltd) is that you can potentially alter the chainstay length and bottom bracket height when swapping.

In this use you would expect the cranks to lengthen between 24 and 26 inch modes so the bb drop is immaterial in terms of pedalstrike and the lower CoG on the child's bike arguably beneficial.
This leads me to sliding dropouts and also to wonder what others have done, as there is nothing new in framebuilding.

[ABiCi]

Maybe this frame by Nao Tomii helps answer the question?

Fugo’s Tomii Cycles Disc Dirt Machine | The Radavist

Tomii Cycles: Catching Up with Fugo | The Radavist

[Blacklabbikes]

Perfect! Thanks!

[Andrew R Stewart]

I am not thinking of running two wheel sizes at once. I'm building a frame to use 24 inch wheels to start with followed by 26 inch wheels when the child gets a bit bigger.

The point of having different dropouts for the two different wheel sizes (Santa Cruz Chameleon 7 Dropouts | Jungle Products Ltd) is that you can potentially alter the chainstay length and bottom bracket height when swapping.

In this use you would expect the cranks to lengthen between 24 and 26 inch modes so the bb drop is immaterial in terms of pedalstrike and the lower CoG on the child's bike arguably beneficial.
This leads me to sliding dropouts and also to wonder what others have done, as there is nothing new in framebuilding.

Thank you for the complete explanation. This is what I initially thought but it seems I over though/read the other posts... Andy