[TimTucker]

Looking ahead at next bike(s).

Current 20" is a Cannondale Cujo, which worked out great for us -- the freakishly large BB drop & short seat tube made it possible to start on the 20" a lot sooner than it otherwise would.

It also meant that the bike wound up with a normal-looking BB height when he got a little taller and we switched to a suspension fork.

Anyone have any suggestions of other 24" / 26" / 27.5" frames that have particularly short seat tubes and low bottom brackets / big drops from the rear axle to bottom bracket?

Added benefit if they can fit at least a 2.6" tire in back, but that's not necessarily a must.

Next step may be the 24" Cujo, but availability may be an issue and it seems like a waste to buy new when the only thing I really want is the frameset.

 

[rton20s]

Here are the figures from a few that I have in my 24" bike comparison spreadsheet. However, there are a lot of other specs that I would look at for selecting a bike beyond seat height.

Haro Beasley 24
ST: 305
BB Drop: 40

Scott Scale 24 Rigid
ST: 310
BB Drop: 40

Commencal Ramones 24
ST: 280
BB Drop: 30

Vitus 24 Plus Kids
ST: 335
BB Drop: 45

Haro Flightline 24+ DS
ST: 305
BB Drop: 45

Rocky Mountain Vertex Jr 24
ST: 310
BB Drop: 40

And I would look at the entire bike geometry, especially when considering a suspension fork upgrade. It would be good to know what the OE fork A2C and tire clearance are, as well as the same for whatever aftermarket fork you might consider (Suntour XCR 24 Air: 415mm/54mm, RST F1RST Air 24: 410mm/55mm) to account for the geometry and fitment changes you'll create.

 

[TimTucker]

Doing some measurements based on the stock photos and using the disc rotors as a reference point, here's what I'm seeing on the Cujo 24:
315mm ST
85mm BB drop
375mm A2C

The closest I've seen on adult frames is something like the Evil Chamois Hagar:
https://www.evil-bikes.com/a/bikes/chamois-hagar

Or the Chromag Doctahawk (with a shorter fork than the 180mm travel fork the geometry table is based on):
https://chromagbikes.com/products/frames-doctahawk

 

[BATRG3]

If you love the low BB height of the Cujo I won't say it's wrong. I got onto that theme a while ago when Isla bikes showed up. In the case of my kids, they grew faster than their motor control, and I was surprised to see them take better to longer cranks, which go hand in hand with higher BBs.

130mm cranks seem a little small to me for a 24+, but that's just my opinion, and it looks like the Cujo 24+ is pretty close in ergonomic geometry to by son's Timberjack 20+, which has 140mm cranks.

 

[TimTucker]

If you love the low BB height of the Cujo I won't say it's wrong. I got onto that theme a while ago when Isla bikes showed up. In the case of my kids, they grew faster than their motor control, and I was surprised to see them take better to longer cranks, which go hand in hand with higher BBs.

130mm cranks seem a little small to me for a 24+, but that's just my opinion, and it looks like the Cujo 24+ is pretty close in ergonomic geometry to by son's Timberjack 20+, which has 140mm cranks.

The big thing with the huge BB drop is that it turns into a somewhat "normal" drop + slacker head angle if you move to a suspension fork.

Most of the other frames I've looked wind up with a huge BB rise when you switch to a suspension fork.

I've been trying out shorter and shorter cranks on my own bikes for the past few years and have 140mm cranks now on my Stache now -- at this point I'm pretty well convinced that most everyone runs cranks that are far longer than optimal.

 

[rton20s]

The big thing with the huge BB drop is that it turns into a somewhat "normal" drop + slacker head angle if you move to a suspension fork.

And this is why I mentioned looking at the bike geometry as a whole. Yes, bikes with minimal BB drop can become an issue if the bike wasn't designed from the beginning to accommodate a suspension fork. What you really need to know is the A2C of the stock fork so that you can evaluate what a fork change will do to geometry. Taking a 24" bike like a Haro Beasley with a 356mm A2C and slapping on a 26" suspension fork is a horrible idea.

Most of the other frames I've looked wind up with a huge BB rise when you switch to a suspension fork.

I haven't examined a ton, but I have a few. Most recently is the Vitus Kids 24+ that we just got for my son. The A2C of the stock rigid fork is 400mm. This is the exact A2C of a Suntour XCR 24 Air with 25% sag and 5mm more A2C than the RST F1RST Air 24 with 25% sag. Changing over to 26" Manitou Markhor with 80mm travel and 25% sag is +16mm A2C. These translate to 0mm, -1.9mm and +6.1mm BB height changes respectively. Even that 6.1mm rise isn't "huge" in my book.

The bigger issue with a bike like the Vitus, or any bike running 2.6" or wider tires is that the only 24" fork that can handle a tire that big with proper clearance is the Manitou JUNIT. Otherwise, you'll be lucky to squeeze in a 2.4" tire. Swapping out to a 2.4" tire lowers the BB by 7.5mm. If you go with the cheaper and more common 2.1" tires it will lower the BB by 14.5mm.

So, yes, I always try to evaluate how potential changes to a bike will impact geometry as a whole. And we haven't even touched on things like seat tube angles and the potential of using angle adjusting headsets.

 

[TimTucker]

I'm pretty much just looking at the Junit fork, which is 500mm A2C for the 24" 145mm version, which would raise things up quite a bit more than the Suntour.

I really like the Cane Creek Viscoset damping headset uppers for reducing wheel wobble & decreasing the effort to keep the bike going in a straight line over rocks & roots, so that would preclude using most of the angle adjusting headsets.

 

[nobody special]

I'm pretty much just looking at the Junit fork, which is 500mm A2C for the 24" 145mm version, which would raise things up quite a bit more than the Suntour.

I really like the Cane Creek Viscoset damping headset uppers for reducing wheel wobble & decreasing the effort to keep the bike going in a straight line over rocks & roots, so that would preclude using most of the angle adjusting headsets.

My 7YO daughter is very short, I think she is less than the 10th percentile. Roughly 44.5" tall at age 7, almost 8. The shortest standover, long wheelbase, 24" bike I could find with a tapered headset was the Rocky Mountain Growler Jr 24. Bottom bracket drop was 40 and seat tube height was 300. She fits on it pretty well. After swapping the fork to the 100mm J-Unit the head tube dropped a few mm. She is only about 50 lbs, she almost never uses more than 80mm of travel on that fork, I think I have about 20 psi in it now and all the valving is open. With the J-Unit, new headset, tubeless, and a Rocket Ron on the back, the bike is about 26 lbs. Front tire is still the Vee Crown Gem 24x2.6, it actually works really well for our local trails.

The chainline is kind of lousy and the drive train was junk, otherwise i am actually pretty happy with the bike overall. I also swapped on 130mm Spawn square taper cranks and they were a big improvement.

Couple pics, ignore the frowny face, her brother was trying to aggravate her. 🙄

 

[TimTucker]

My 7YO daughter is very short, I think she is less than the 10th percentile. Roughly 44.5" tall at age 7, almost 8. The shortest standover, long wheelbase, 24" bike I could find with a tapered headset was the Rocky Mountain Growler Jr 24. Bottom bracket drop was 40 and seat tube height was 300. She fits on it pretty well. After swapping the fork to the 100mm J-Unit the head tube dropped a few mm. She is only about 50 lbs, she almost never uses more than 80mm of travel on that fork, I think I have about 20 psi in it now and all the valving is open. With the J-Unit, new headset, tubeless, and a Rocket Ron on the back, the bike is about 26 lbs. Front tire is still the Vee Crown Gem 24x2.6, it actually works really well for our local trails.

The chainline is kind of lousy and the drive train was junk, otherwise i am actually pretty happy with the bike overall. I also swapped on 130mm Spawn square taper cranks and they were a big improvement.

Just did a quick comparison of Cujo vs. Reaper:
* Reaper has a slightly shorter seat tube, but not as much BB drop

* Net result is the Cujo has a height from ground to the top of the seat tube that's slightly lower than the Reaper in stock config & about the same if you were to put on a fork with the same A2C as the Reaper

 

[OlavMe]

Im currently in the same situation. Our 7 year old, went straight from the balance bike to the Islabike Beinn small (20) 2,5 years ago, and she is now about to outgrow it. Been hunting high and low after XXS 26 frames/bikes. Ended up yesterday with buying the Vpace max 26. 330mm seat tube, 70mm bb drop. The Vpace website is in german only, but apparently they do answer e-mails and ship worldwide. I found and bought my frame used at pinkbike.

Frame only is about 349 eur plus shipping