Disc road frame for commuting

[jasonc]

Almost all my bits have arrived, enough to start building.

So far I have frame, forks, headset, stem, handlebars, seat post, brakes, BB cups and hubs. So pretty much only the full grouppo (minus brakes) and rims + spokes to come.

Going to try and start putting together this weekend

saddle?

My Brooks B17

phew. the insertive alternative didn't sound inviting

[barefoot]

So... moving right along with my proposed disc road build that I'm not doing yet... the fork.
...
evilBay is filled with these forks, for $180-200:

...
I'm finding a hard time thinking of a reason not to grab one of these forks, then design my frame to suit (ie take the "extra" length out of the head tube).

Damn my itchy trigger finger

I went with the branding variant as shown, with a subtle "Picasia" logo on the crown rather than garish "Trigon" logos down the fork legs. $180 delivered for a 460g full-carbon disc fork... can't argue too hard against that.

I also recently stumbled across most of a 9-speed Ultegra gruppo, from somebody who upgraded to 10-speed. The brifters are a bit quirky and the derailer has a few battle scars, but they'll transfer from my old bitsa roadie to the new disc roadie and do the job for a while at least, which will help spread the spend out.

So, really, I'm getting close to being only one frame short of a full build. And so, I'm now in serious frame detail design discussion with XACD and Titan Product. I think I'll go with XACD. Quoted US$800 delivered for a custom Ti disc brake CX frame, but they're known to start bumping up the extra charges once you start speccing anything more than the bare bones so it might stretch a bit closer to the $1k I was reckoning on.

Then the only bits I need to source are the brakes and sundries (cables, tape, probably a headset... most of the remainder can transfer from other bikes or the parts pile)... and a decent crankset/BB if I can sneak it under the radar

tim

[Reman]

Tim, any thoughts on brakes. We've all pretty much gone the BB7 route, so it would be interesting to hear your thoughts.

[barefoot]

Tim, any thoughts on brakes. We've all pretty much gone the BB7 route, so it would be interesting to hear your thoughts.

BB7 all the way. No question.

As I said a few pages ago... I have an Avid "BBDB" on the front of my old MTB, dating from before they called it a BB7 (and introduced lower models under it). The performance of that brake prompted me to get BB7s on my next MTB, and they worked flawlessly until the bike was stolen.

My current "good" MTB has hydraulics... and I'm ambivalent toward them. They work as well as... probably a bit better than... the BB7s. But if they stop working (as they did once when a bubble got into the wrong place), there's absolutely nothing I can do about it, in the field, using normal pocket tools. I don't carry a bleed kit with me. There's no agricultural hack I can do to fix a ruptured brake line or blown piston seal.

Hydraulics are of no interest to me on a road bike, even if they were available, and there ain't no better cable disc than a BB7.

tim

[barefoot]

XACD. Quoted US$800 delivered for a custom Ti disc brake CX frame, but they're known to start bumping up the extra charges once you start speccing anything more than the bare bones so it might stretch a bit closer to the $1k I was reckoning on.

...like an extra $135 to put the brake mount on the chainstay
We'll have to wait and see what that $135 gets me... waiting on drawings now.

tim

[barefoot]

waiting on drawings now.

(click for bigger pic)

That's the first iteration of a drawing with my geometry. Yes, it's a bit unusual, no it won't fit you

A few things to be changes - the seat stays in particular (I'll have them in 16mm tubing with S-bends instead of straight 19mm please). I'm not entirely convinced by those dropouts, but that seems to be about the best way to put a disc mount on the chainstay, which is where it should be if I want pannier and fender mounts at the rear dropout.

But I've identified a dilemma. Cable routing.

As shown, they've proposed both shift cables go around the left side of the head tube to a plain cable stop (then bare cables under the BB, traditional road bike style). The brake cable goes down under the right side of the down tube, in full-length housing (or hydro line, I guess), and over (?) the BB to the top of the LH chainstay.

But... I would quite like barrel adjusters for my derailers, at the cable stops on the downtube. And the traditionalist in me would rather see a shifter cable on each side. But then, what becomes of the brake cable?

I've had a very brief trawl of google images, and can't find any clear pictures of what others have done (although many seem to be going with internal cable routing, which doesn't interest me). I'll keep looking for clues.

CX bikes tend to have top-tube routed gear cables, which requires a MTB front derailer (top pull) or a pulley to use a road derailer (bottom pull) (and which precludes the use of barrel adjusters anyway). A seatstay mounted disc brake would just have the cable routed along the top tube.

Any ideas?

It's the problem with going for a Chitanium custom frame... you have to decide all the details... and if you get anything wrong, you can't blame the designer

tim

[barefoot]

This could be the go.


I mean, aside from the colour

Brake cable anchors down the middle, so I can have barrel adjusters either side.

I'd like to see a picture of how the brake cable squeezes between the bare front shifter cable and the downtube (then over the BB shell to the chainstay anchor). I'll have to have a good look at my bikes in the morning to see how much clearance there is there.

Another viable option:


Looks a little bit odd having the brake cable up there on top of the DT, but it would keep the cross-overs tidy.

tim

[toolonglegs]

CX bikes tend to have top-tube routed gear cables, which requires a MTB front derailer (top pull) or a pulley to use a road derailer (bottom pull) (and which precludes the use of barrel adjusters anyway). A seatstay mounted disc brake would just have the cable routed along the top tube.

Any ideas?

My bike runs normal DuraAce front deraileur with a pulley, the barrel adjuster is fitted on the back of the seat tube, but I never use it, find it easy to set up with cable tension at the deraileur itself, but it is there if ever I need it.

[barefoot]

It's the problem with going for a Chitanium custom frame... you have to decide all the details... and if you get anything wrong, you can't blame the designer

Well, the designer is going to have to accept the blame for whatever he got wrong, because he just clicked the trigger button for one of these:

(clicky through for big)

Oy vei, what have I done?

I'm promised to find out in about 4 weeks. Merry Christmas to me!

It came to US$1020 in the end - including freight and a Paypal fee add-on, in addition to the $135 dropouts and another $50 for brushed finish instead of sandblast.

Also in transit are $150 worth of BB7s, $180 worth of carbon MTB fork, $45 worth of (superseded) Cane Creek S8 headset, far too much worth of very pimpy cables. In the shed are $200 worth of half-built wheels.

That means I'd still need to find crankset, derailers, shifters, cassette, bars, seatpost, saddle, tyres and bar tape for ~$345 if I was going to slip in under my estimated $2k budget... which would be a serious struggle (especially considering the benchmark $800 105-equipped bikes are all out of stock at the moment)... although I can make do with existing bits for most of that, for a while at least.

I should be able to recoup a reasonable portion of that by offloading the two bikes that this will displace - that is, the remains of my bitsa roadie (once I pinch the parts I need to finish the build) and my Long Haul Trucker (which is a much more serious touring bike than I want or need right now). At least, that's the official story when the Minister for Defence finds out - I guess she'll notice it under the christmas tree

tim

[Reman]

Tim, glad to see you still believe in Santa!

[barefoot]

[JustJames]

That looks trouser-tentingly lovely!

[MichaelB]

Looks great barefoot.

Please weigh the frame for me.

What fork did you end up going with ?

There's nothing sweeter than a good weld. Work of art !!!

[barefoot]

Looks great barefoot.

Please weigh the frame for me.

What fork did you end up going with ?

There's nothing sweeter than a good weld. Work of art !!!

Bare frame is 1575g.

(the drop-out protector weighs about 20g )

That's not fly-weight, but it's not meant to be. All straight-gauge tubing, and there's a fair bit of material in those dropouts.

I went for, and designed around, the Trigon/Token/generic carbon MTB fork, as seen featured on your local eBay. I got a "Picasia" branded one, because the logos are more subtle. Uncut, it weighs in at 454g.

Edit to add:


I say "designed around" because it's longer than a standard road fork (420mm re: ~370), so I shortened the head tube to suit. That's not a problem for me because my main reason for going custom was to get a long enough head tube. Even with the 50mm fork correction it's still a 148mm head tube - it would have been about 200mm otherwise (which is kind of ridiculous on a 54cm frame with 500mm top tube, but that's just how I'm built). With a standard 100mm ~7° stem, I'll be in about the same position as I am now on my three drop-bar bikes, each with a ridiculous steep stem on a big stack of spacers. Long back, short arms... need the bars up high and short to be able to reach 'em.

It might be a fairly slow build from here... I need to offload at least one bike before I ask for spousal approval to order this one

tim

[Bentnose]

It might be a fairly slow build from here... I need to offload at least one bike before I ask for spousal approval to order this one

tim

Is that why its in the office and not the shed?

[barefoot]

Is that why its in the office and not the shed?

Precisely.

Can't get this kind of stuff delivered to home without arousing suspicion

tim

[MichaelB]

Not a bad weight for the frame there given it's all PG Ti tubing.

Looking fwd to more pics and data.

And what's the latest with reman's build - seems to have slowed .....

[Mulger bill]

That looks trouser-tentingly lovely!

Yep, what he said. Damn fine looking steed.

[Reman]

Not a bad weight for the frame there given it's all PG Ti tubing.

Looking fwd to more pics and data.

And what's the latest with reman's build - seems to have slowed .....

Ummmmm.....I've been busy riding it

Will update the bike build thread with final build things and a "review" and some pics.

Sneak preview...

[barefoot]

Well, the designer is going to have to accept the blame for whatever he got wrong, because he just clicked the trigger button for one of these:

(clicky through for big)

There was always going to be something

I really should have paid a bit more attention to those clearance dimensions around the crankset area. True to the standard disclaimer with XACD... you get what's on the drawing, whether or not that's what you really wanted.

I test fitted my 6750 Ultegra crankset yesterday. The inner ring hits the chainstay. I had a hunch it would, which is why I put them on. There's only a couple of mm in it, but we currently have an interference fit

If the stays weren't bent so much, to get around a hypothetical tyre that I have no intention of actually running, things would be just fine. The cranks themselves have plenty of clearance, it's just the 32T ring.

As a short-term solution, I think I'll build it up with an old square-taper RSX compact crankset I have in the heap, with a long spindle BB to push the chainline out a bit. That will work fine... but old solid-arm cranks and cartridge BBs are heavy bastards of things, and I've somehow turned into a bit of a weight weenie on this build.

For a long term solution... well, the short-term solution is to buy me some thinking time to work out what the long-term solution might be.

It used to be fairly common practice to push a dent in to the chainstay of a steel frame to get better crank or chainring clearance. I'm reluctant to do this, for fairly obvious reasons... and also because the problem area is just where the bridge is welded in, so deforming the shape of the tube there is going to stress the weld. Other options... maybe a triple crank, as is shown on the drawing, which would have a slightly wider chainline? Maybe figuring out some bodge with a Hollowtech 2 MTB BB, which (as far as I can tell) have narrower bearings and spacers, which can be left out to allow for a BB-mounted chain guide or front derailer or a wider BB shell. Maybe it would be possible to swap the spacers around to push the drive-side crank out a fraction (which would make the pedals assymetric... hmmm...).

Or any other suggested solutions from the assembled wisdom we have here.

Buggerbuggerbugger. Oh well.

tim

[MichaelB]

Not quite FUBAR, but close.

Hope you get it sorted

[barefoot]

Not quite FUBAR, but close.

Nah, nowhere near FUBAR. Just incompatible with the particular build kit I had planned.

It will work.

tim

[Reman]

Could you shim the BB out a little pushing the crank out a few mm?

[Crawf]

Yep try a few spacers.

[warthog1]

Is that why its in the office and not the shed?

Precisely.

Can't get this kind of stuff delivered to home without arousing suspicion

tim

You are a very brave and sneaky man

Love your work