Project Custom Hardtail Geometry Questions


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So, with Covid related spare time and boredom I've thought about Welding a Frame up. Has to have been about 20 years since I've TIG welded, but given I'm currently out of work for the forseeable future (Massage Therapist) it seems like a good time have a crack at doing something I've wanted to do forever (my Trade School Teacher used to fabricate Road Bikes and it looked pretty cool). I'm thinking a 29er Hardtail (130mm fork) for simplicty, and its something different than my Trail 27.5 Duallie. Looking for something to ride up and down Red Hills trails like Fall Line and Pins and Needles (I'm a conservative rider, keep the wheels pretty much on the ground, don't take on the bigger tracks down Eatons.) This is my first crack at the Geometry and would appreciate any feedback and opinions if anything looks like its out. I'm 170cm tall, and generally fit either a Small or Medium Frame, but I've only had a handful of bikes and don't really know what feels best re. Reach, Stack and Top Tube numbers.


chez le médecin
Dont know much about the numbers but I would use an existing modern frame if a friend has one that fits nicely , as a basis.
No need to reinvent the wheel so to speak and obviously use a straight oversized steerer tube with appropriate bearings since no one has off the shelf tapered tubes ?.
I have a Chameleon hardtail that seems good but there are plenty of frames out there.
Also allow plenty of room for a big back tyre if thats what you want, 1x front is the easiest.
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I did look at other bikes (online), mainly the Ragley BluePig in the end. Nova Cycles do good sets of tubes with the Headtube included, just assume I'm going to get reamed on current exchange rates and shipping times, by the time I get the parts I'll probably have forgotten about the project.


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From the one I had built a while back, I'd say the seat tube is quite steep. At sag your design would sit at ~77.3deg. Depending on your tastes, this isn't typically a problem when the seat is up (it's actually great for steep fireroad climbs, but can place a lot of weight on your hands and wrists if doing a lot of pedaling on the flat...) - reason I mention it is I've found with the dropper lowered the seat is more "in the way" than on previous bikes with slacker actual seat angles. My next design will have a slacker actual seat tube angle while keeping the steep effective angle, but it'll be several weeks at least until it arrives and I can offer real-world results of my experiment.

From the look of the head-angle you've selected I'm guessing you've already considered this - but if you're comparing geo to previous dual-susp bikes, remember to base your geo dimensions off geo at sag, otherwise everything will be off the second you climb aboard (longer reach, lower BB, steeper head-tube, etc...).

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Also, FWIW you don't have to worry about tapered head tubes so long as you allow for external headset cups in your design (effectively by allowing more A-to-C length). I think the 44mm ID head-tubes are most common size, and there is several brands of lower cups that will fit the tapered steerer forks.


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Thanks Beeb, might pull the Seat angle back a degree. You can get ZS44 cups that have pretty low stack height (4mm on ther bottom cup), I'm allowing for a 540mm axle to crown at the moment, it does seem to vary a lot depending on what fork you buy (looking at 130-140mm travel). So all the thought you put in to geometery can be wasted just by changing to a different brand fork/