JM's Bikes: Hybrid Bike Chapter

Finished up machining the main pivot components!


Time to re-visit my list…

Slowly making our way

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What bearing size you ended up using?

6902
Small? maybe, time will tell

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This is the first time the bike has actually looked bike shaped. Very exciting. It’s mostly just tacked so lots of work left to do but seeing the project in this state gives me lots of motivation. We’re just starting to get good weather where I live so closing in on riding season.

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Great work. Looks amazing (love the horizontal CS and matching Seatstay/TT angle.

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frame welded. I couldn’t help myself haha

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I’m getting pretty close to finishing this project. I have a few more braze-ons, and I have to machine a collar for the seat post. Other than that, I am ready to start thinking about paint. I want to get some opinions

Main Triangle Color

  • Blue
  • Yellow
0 voters

Rear Triangle Color

  • Color matched rear triangle
  • contrasting (gray)
  • contrasting (black)
0 voters

See pictures below

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I vote signal yellow

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That was a lot of hard work. The only thing left to do now is paint.

@Jukka4130 The front triangle weighs 4.5 lbs and the rear weighs 3.8 lbs. So 8.3 total.

Now that the fabrication is complete I can reflect a little bit on the design/build.

Concerns and negatives

image
image

There were some issues with this method of attaching a shock mount. Because the edge of the tube is so close to where it’s being welded, it was very challenging to avoid peeling out. This would have been much better brazed. Also, the ‘end caps’ are not brazed steel as originally planned, but aluminum secured with Locitite 638. Because of the forces on this part, I’m not so worried about the caps popping out, but I do wonder if the aluminum might squish and deform over time.

Another concern is that the seat collar is aluminum and is held in by more Loctite 638. That stuff is pretty strong but time will tell if it’s strong enough.

Finally, there’s the quality of the welding and brazing. I’m not good at welding or brazing, but each welded joint is fully penetrated with no undercuts and each brazed joint has braze all the way around the joint with no deep pits. The inconsistency may cause stress risers and lead to this frame failing from fatigue far before most, but I don’t think it will fail on my first ride.

Things that worked well / positives

The main pivot is solid with no play. Assembly is a little tight, but that is the tradeoff I suppose.

When assembled, the bike is relatively aligned. At least to my eye, which is the level of precision I aim for :slight_smile:

Lastly, it looks awesome, which is something I care about.

My overall opinion is that there are some major weak points in the design and craftsmanship of this bike, however I don’t believe there are any so egregious that the bike would fail suddenly and catastrophicly on the trail (knock on wood). With the way I ride, I expect this bike will last a little while, until one day a crack develops somewhere or one of the aluminum parts begins to change shape. At which point, I will move on to my next bike. Only trail time will tell though, and no matter what happens, I’m still proud of myself for all the time and passion I put into this project.

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Excellent work!

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This is the color scheme I went with. I think it looks awesome. I have some more components and tuning to do before she’s ready for the trails.

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Looks so sick mate!

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First official ride around the block!

My first impressions are good. It doesn’t feel weird to ride on flat ground so it passes the first test. Maybe I can get it on some dirt tomorrow.

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First real ride on the new steed. No failures, and performed mostly how I imaged. I couldn’t stop smiling while riding it. I’m calling this bike the ‘Hog’ because it’s long, heavy and totally hogs down the trail.



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470 chainstays? Reach?
A few bikes I have liked the most have had long chainstays, but I have never tried longer than reach. Id like to test out longer ones on my bike reach=cs length.

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Beautiful! :heart: The two color scheme wase the right choice. That bike came out so good. It looks like a very fun ride!

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Great feeling getting that first ride in on a fresh build. Bike looks great.

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Thanks for the kind words buddies. The Hog has been treating me well. A little pop can shim in the seat post but aside from that there have been no issues. Just good riding.

I’m without a project now and thinking about my next frame. Time to change this thread from ‘JM’s Mountain Bike’ to ‘JM’s bikes’. I can’t have a thread title less than 15 characters so I had to juice it up.

Anyway, my stable consists of a road (touring) bike and my newly constructed mountain bike. A gravel/bikepacking bike would round things out nicely.

The thing is, I’ve never owned a gravel bike.

Here’s a video of me wishing I owned a gravel bike…

No experience on a gravel bike will make designing a little harder, but from my experience taking road touring bikes into deep water there are a few things that I wish for in those moments.

  • Thicker tires (obviously) - I see some gravel bikes now come with full on mtb tires, 2.3" and up. I like the idea of building a frame with clearance for these tires. I could always downsize if I choose.

  • Wider handlebars - Drop bars seem to be the norm, but I prefer flat bars on technical terrain. There’s a lot of weird alt bars to consider as well, which might give a good compromise between handling and multiple hand positions. Is a flat bar gravel bike considered a hybrid? :thinking:

  • Derailleur with clutch - I will use a mtb drivetrain, or possibly a gravel drivetrain like GRX if I find a used set for the right price.

  • Hydraulic disc brakes

There are some other things I’m not sure about.

  • 29 vs 27.5 - In my head, 29 seems like right choice. It’s the only wheel size for XC racing now days. However, I see many more 27.5 gravel bikes. Is this due to the desire to switch between narrower 700c tires without changing BB height? Is it to maintain as short a wheelbase as possible? There’s something I’m not fully understanding here.

  • Dropper post? - Of course this is opinion. But for those who ride gravel often, is this a feature you think is worth considering?

Aside from those parameters, the overall vision I have is a fully rigid bike for off pavement riding with a relaxed geometry for long days in the saddle. Speed is not a focus. If you have time on a gravel bike, please share your opinions with me.

To finish this post, here are some inspo pics. Mostly just for myself to look at and contemplate.



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Into this idea. A flat or alt-bar is my preferred bar for “gravel” riding which to me is essentially XC. Can defo reccomend designing around 2.3” rubber too. 27.5 or 29 doesn’t really matter for this kinda bike but if you don’t plan to swap wheel sizes then I would say 29” is the go! I would go as long as you can in the front centre unless you want to try drops one day. A dropper post is nice to have but not essential. There are a couple decent 27.2 options now as well. Below is a pic of my Crust Dreamer, which has seen 30,000km+ and many different builds. I ride a lot more trail now but this is probably the one bike I’d never sell.

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beautiful bike! I appreciate a well used machine. How do you like the swept bars for long rides? Do you ever wish you had more hand positions? I have done extensive touring with drop bars, and I’d say I use 70% hoods, 20% tops, and 10% drops. Not sure if I’d miss the options or not.

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