Bike Geometry and Ride

[Miq]

@SirMike1983 its interesting because all the handling advantages are still there off road (where you might need them even more desperately than on pavement) with the trade off being the ground clearance to BB and pedal strikes.

 

[J-wagon]

Just for kicks I measured BB height of few other 26er mtbs, full rigid:
1983 Trek 850 11.75"
1988 schwinn high sierra 11.75"
Haro, mongoose, univega various years 1987 - 1994, range 11.5 to 12"

29er XC mtbs:
2012 niner air 9 carbon, 12"
2012 specialized stumpy ht sworks, 12.5" (unsagged with 90mm front fork).

As for BB hitting rocks etc, usually my chainring will hit since it sits much lower. So I prefer small front sprockets on mtb klunker builds eg 16t to 18t skiptooth, avoid hits rolling rocks, small logs, etc. But primarily small front better gear ratio singlespeed up steep hills.

 

[SKPC]

Look carefully at J-wagons various machine builds, page 7, post #69. He clearly rides a lot, modern and old.(see his carbon 29-er mtb rocket) You will notice that no matter where his seat is, modern or old, his bars and hands are positioned slightly above or below his seat height and for the most part in front of his head tube. This keeps him in the center-forward position on his bikes, which is a good thing when trying to up the performance levels beyond the bike path. Necessary. The up-in-the-air hands "apehanger" position, while comfortable, limits your ability to stand up quickly to accelerate or climb and the front end of the bike will want to "lift" or there will be no room to comfortably position yourself forward over the front wheel without your hands and bars getting in the way. If off-road riding a custom built prewar 26-er frame, your hands should ideally be in front of the frames' head tube. Hands high in the air and swept back certainly feel good in the flats cruising, but don't expect this to help the bike perform better.
In regard to the 21st Century Hawthorne, it is a unicorn bike. It started as a Long wheelbase 1931 28-er frame/fork. Long rear stays on the frame allowed fat 26' rear wheel but the fork did not. I went 26" by installing the shorter custom Shelby front end. The result is a very low BB height, super steep angles for both seat and head tube while maintaining a longish wheelbase. Understand also this bicycle was initially fitted with an original 28-er fork. In total, the frame's angles, overall light weight and fast wheels make the bike ride like no other 26-er I have. Clipped in, over the BB and "in the pocket" is how I fit this bike. Result? Rocket. Catching or joining groups of roadies in packs at 20mph in the flats is easy with this bike. The front Shelby fork issue of splaying out when standing up has been recently resolved to a large degree as I installed a heavier spring with more preload on it.🛠️ The cool thing about building your old steel frames/forks up is that you can choose your parts to specifically create a bike that fits you and the position you need for the riding you do.

 

[J-wagon]

1950 JC Higgins Colorflow klunkerette. A fun ride. Capability wise, requires more effort to maintain out of saddle pedaling,so use low gear ratio 1.6 seated climbs. Pedal strikes common. I would not attempt small drops on it. Doesn't feel right for technical handling. But plenty of standover clearance.

Wheelbase c-c, 44. 5"
HT angle 73 deg
HT length 5.375"
Fork rake/offset, 3"
Stack 20.875"
Reach 17"
ETT 23.375"
ST angle 72 deg
BB hgt 10.25“
BB drop 2.75"

Of note, fork missing beehive springer assembly, didn't know it at the time, thought normal. Wheel sits lower and further out. Makes wheelbase longer, fork offset more, trail shorter, smidge steeper HT angle. Turns out I think makes steering more responsive.

Below pic shows how fork and wheel is suppose to be

 

[Miq]

Thanks @J-wagon, more stuff to think about. It's a really unique set up. Those Bullmoose bars put your hands in front of the entire headtube it looks like. The 3" offset is also much bigger than the other bikes we've looked at but is offset somewhat by the steeper head tube angle. It is kind of amazing how well it all works out being so different than the original design intent with the Beehive springer. The BB height and drop are ridiculous. I can understand the common pedal strikes but also the fun of riding a bike with a very low center of gravity and tons of stand over room.

As for BB hitting rocks etc, usually my chainring will hit since it sits much lower. So I prefer small front sprockets on mtb klunker builds eg 16t to 18t skiptooth, avoid hits rolling rocks, small logs, etc. But primarily small front better gear ratio singlespeed up steep hills.

I am with you there. I've had to replace chainrings with missing teeth on my MTBs with all the exposed rock out here. 😀 It's pretty clear the gearing in vintage bikes is somewhat whack the more we talk about it.

..... don't even get me started on the "downhill only" gearing bikes had until the mid-late 50's.

I've been liking the small 40T front chainring on my Klunkmaster paired with the 3 speed.

@SKPC I see what you are saying about the hand position in relation to the seat and I have an idea I want to try to compare bikes directly. I'll work on it. Thank you for continuing to add to your ride evaluation of the 21st Century Hawthorne. I updated the chart.

The first klunker I built with my grandfather in the early 80s by ripping the fenders off a girls Schwinn and racing my buddies through the woods in PA. Your Klunkerette brings back good memories @J-wagon.

 

[Miq]

I know it's not perfect but this is close to showing a good comparison of the two @J-wagon bikes we've been discussing. I tried lining up the heads.

The JC Higgins big offset pushes the front wheel a little further forward than your Snyder Fastback. It looks like the stack and reach are similar in the photos too but you can see how your saddle and grips are more forward on the Colorflow. It seems like your whole body would be closer to the front wheel of the Colorflow but the big offset helps counter act that. The angles of the pics and sizes are not exact so it gets a little goofy looking at the back of the bike, but I think this transparent overlay is pretty cool for direct comparisons of your bikes @J-wagon. They are both set up for you so it seems reasonable to overlay them.

 

[J-wagon]

Wow. Cool overlay!
I remember pushing down bullmoose as far as possible for lower position. Now I see 1950 klunkerette has longer HT. I guess this is one situation HT length plays out with fit.

On 1936 Snyder, I used to have 7 seatpost reversed with saddle further back, post bent back when rolling step features. Fastback exposes lots of post. Turned 7 post around, less weight behind rear triangle. Turns out forward position not bad. Less stretched out, easier to jump out of saddle for standing climbs, and easier to slide weight back for small drops 👍👍

 

[Miq]

Yea, it looks like the grips to saddle distance of the Fastback is a little tighter with your center of gravity a bit more forward, closer to the BB. Nice that you can slide way back on that saddle when you need to for downhills but also stand quickly, more forward of the BB, to climb. Thanks for your impressions of that trade off between how the two bikes are set up.

None of those differences show up from the frame geometry numbers alone.