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Planning a Ti custom built road disc frame ... What do I need to consider?
I have the geometry ...
Fork Axel to Crown length
BB 68mm English
Rear Drop Out 135mm
Disc tabs on Seatstay
I am sure I have missed something? ...
Your preferences in ride quality and stiffness
All these make a difference in the shaping, wall thickness and butting of the individual tubes selected.
You talking to me?
I would recommend taking a look at rattleCAD | Free software downloads at SourceForge.net for a really easy to use CAD design tool to make sure your geometry is getting you where you want to go.
If you want to use fenders or racks I would consider moving the disc calipers to the chainstay.
Paragon Machine Works is a good place to look at all kinds of frame building bits and pieces when you get around to cable routing and the like.
Last edited by B2; 11-08-2012 at 07:24 AM.
First one home gets beer
73mm BB or you will have chainline issues with the 135 rear end..
And go with hydraulic, not cable based brake calipers.
“In an honest search for knowledge, you quite often have to abide by ignorance for an indefinite period.”
– Erwin Schrödinger, 1948
That's more personal preference than anything, not a definite OMG NEED HYDRAULIC. I have no problems with cable discs.
Originally Posted by AJL
Originally Posted by AJL
I've got six years on my commuter's BB7s. Maybe I don't know what I'm missing, but I like them a lot and see no need for improvement.
Originally Posted by GirchyGirchy
As for a new frame, I'd suggest having braze-ons for hydraulic, but since there are currently no integrated levers with master cylinders (well, that one weird-looking one) use the hydraulic braze-ons for now to run the cables fully housed. (Insist on compressionless brake housing.) Later, pull out the cables and housing, slide in the hoses and Bob's yer uncle.
Word on the street says the Big 3 have integrated hydraulic cylinders in the hoods ready to go, but waiting till next year for more disc frames to be on the market before introducing their hydraulic disc road groups. Just a *ahem* rumor.
When I had my bike made, I balked at discs because I wasn't sure what the technology would look like (135mm vs. 130mm rear spacing). Still unclear where the road groups are going. It seems 135 is still the standard.... for now. There needs to be more disc specific wheelsets on the market as well.
that is a point that I would not have even thought about. i wonder why lynskey does not use a wider bb for their cooper cx disc frame? makes sense that they should. do you know how bad the chainline would be with a 68? (i'm assuming an mtb frame has a 73mm bb width.)
Originally Posted by Stockli Boy
Ordered and Fitted for my Custom DEAN Titanium frame on Sept 17th, 2008. Finally got it in Oct, 2010!!!
I've had 4 custom ti bikes built over the years:
Specify maximum tyre size too - with fenders if needed - check front-centre dimension to minimise front wheel overlap. You'll appreciate the plushness of 1.5" tyres if riding lots of trails.
I've run a 135mm rear on a 68mm wide BB with discs for years- no worries - 73mm BB shell limits you to MTB cranksets. Avid BB7 are easy to fit and reliable with plenty enough power. Beside no-one makes a drop bar hydro lever yet.
Have hydro-hose clips rather than cable stops fitted for brakes and chainstay mounted rear brake.
Consider IS44 headtube - can accommodate taper or straight fork steerers.
Specify your fork length and offset.
Fender and rack eyelets weight next to nothing - you might appreciate the versatility at a later point.
If unsure about geometry, best to copy a proven design from a reknown builder.
This issue is entirely dependent on the crankset you intend to use...I don't believe there is a road crankset on the market that will work with a 73mm BB shell. If you want to be limited to an MTB crankset, go ahead with the 73mm BB shell.
Originally Posted by Ride-Fly
I've had a couple disc CX bikes that use a 68mm BB shell and road cranks with a 135mm rear hub spacing. Chainline is not an issue unless you're specing really short chainstays...which I doubt you are in this type of bike as it will really limit your tire clearance.
EDIT: I see that Monty Dog has answered while I was typing...
I second the 44mm ID headtube suggestion.
Also, tell the builder which crankset (ring size) you want to use. Be specific and don't just say "a cross crank." I'm speaking from a friend's personal experience here. Cross cranks can be 130mm BCD with a 38 tooth small ring as well as compact 110mm BCD and 34 or 36 tooth small ring.
Consider whether you ever want to race it as you currently cannot and unless the UCI does a complete backflip on their wheel rules, wont ever.
44mm ID headtube etc is a non issue for me as I can tell absolutely no difference in stiffness between 1 and 1/8th vs tapered. This is especially true for road bikes but I feel the same about their use on MTB.
IMO all of the latest must have updates (tapered HT, BB30, wider rear wheel spacing, through axles, disc brakes on road bikes etc) are just marketing hype.
My best advice will be to get something that you will love just as much in 20 years as you do when you get it.
Dont be sucked into the latest fad updates as these will be gone again in a few years to be replaced by some newer, even more faddish must have upgrade.
I wouldn't do this as youre more than likely not a professional frame builder and like they say a little knowledge is a dangerous thing.
Originally Posted by B2
You haven't mentioned the most important thing yet, the builder and your personal relationship with them.
Screw that up and all the drawing and internet forum discussion will mean little.
Choose a builder and enjoy the process, you are paying them to do what you're trying to get strangers to do for you.
Make a list of questions and then start calling on them.
Edit Signature here---------->
You talking to me?
I would never discount advice, expertise and opinions of any reputable frame builder. That is without a doubt is probably the most critical part of the equation for a successful build. For some, it's the only part of the equation and they just want to know when the frame will be done. For others though, part of the experience is going through all the variables with the builder together and making decisions jointly (there are options). Understanding the options and implications of each a little better would usually be viewed as a benefit.
Originally Posted by kiwisimon
The OP has already stated that they have a good idea of what they want regarding geometry. I was simply saying RattleCAD would be a good resource for inputting the variables the OP knows they want and then get a look at how all the rest of it all falls into place. It's actually a very cool program that could also be used to help one understand certain aspects better which could lead to discussion with the frame builder that wouldn't have occurred otherwise. It would help to have at least a "little" knowledge before you start plugging numbers in.
Last edited by B2; 11-17-2012 at 10:34 AM.
I thought Zinn's comments about hydralic vs. cable for disc brakes made sense. But as many have pointed out, there aren't any master cylinders for road brakes yet. There will be manufacturer specific ones in 2013, but nothing from Shimano, SRAM or Campy till some time after that. So it's a moot point ATM.
Originally Posted by brucew
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