TimmyP’s frame underway

On to frame #18. I’ve known TimmyP for right around 12 years. We became friends when I moved up to Ned and began riding trails and dirt roads on the way to work in Boulder and back off the bus home. Those were the days when all we rode were singlespeeds and them were some good days. We are about the same height but Tim always chose a “large” frame and I always chose the “XL” and that describes our preferences to some extent – he likes a more nimble and quick steering bike whereas I’m preferential to a more ‘stable’ bike.

So here’s some notes on Timmy’s new 29er. This is a departure from the more slack frames I’ve been making recently and a return to more classic geometry of the good ole cross-country days and of those singlespeeds of the late 90’s early 2000’s. What that means is that it’s 71/73 head tube/seat tube angles but with a few tweaks. He’ll be using a Lefty 100mm XLR fork and SRAM XX1 for the drivetrain. He wants this bike to behave as nimble/quick/fast so it’ll get somewhat short chainstays at 17″ (425 effective) and steepened the seat tube angle to 73.5 degrees so he could use a Ti layback seatpost for some extra flex for the but-tocks. This is the best I believe you can get to ‘hardtail suspension’ – Ti layback post and a Ti-railed comfy saddle (or a Brooks). A slacker seat tube angle would help too but we’re going for something that’s quick to stand up on and pedal and has a different weight balance so I wanted to keep it steep. The offset seat tube offers a little bit more rear tire clearance and it steepens the STA that I set in the fixture to 74. But because of the offset & layback post the effective seat tube angle (BB center to top and center of saddle) is 73 degrees. I really am looking at setback and adjusting the STA to keep it constant between his hikes (horizontal distance from BB to center of saddle). The BB is 12″ high with 2.25″ tires to keep it low as I like to go on an MTB especially for the Rockies. It’ll have a bent and slightly ovalized double-butted top tube, beefier Paragon head tube, a sleeved seat tube, and internal cable routing for the rear brake and rear derailleur. No front derailleur to worry about thank Dog.

Notes on the mitering. You can use the phase ‘keeper’ on the Anvil MTMF if the tube isn’t TOO bent (see pic). I didn’t have the downtube in hand so I mitered the top tube this weekend, fit it, and end-milled the internal cable routing slots. I’m going to go in the head tube with the internal routing and not put any holes in the front of the top tube. I’ve been wanting to try this so Timmy, you’re the test dummy. I think it’ll actually be better and there should be plenty of room to get around the steerer tube. Just have to make the breather hole for the top tube pretty big.

Being mostly a TIG guy, I think I like using seat tube collars better than sleeves…less work and futzing with fixturing and you can use a larger diameter seat tube and still use a 27.2 post.

One Response

  1. […] i am beyond excited that my custom bicycle is now being created!   […]

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