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  Topic Name: bike geometry for up and down hill--------- Reply #20 on: June 24, 2014, 09:46:55 AM
juanesunpescado


Posts: 38


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« Reply #20 on: June 24, 2014, 09:46:55 AM »

You know the phrase that non wine snobs use when drinking with wine snobs, something like "I don't know much, but I know what I like".

I like this: http://www.jonesbikes.com/production_framesets.html

I have the ti spaceframe. Frame bag space is limited, but the truss fork opens up a lot of fork storage options and since unloaded the front end feels light (because of short chain stays) I still feel pretty balanced.

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  Topic Name: bike geometry for up and down hill--------- Reply #21 on: June 24, 2014, 08:24:29 PM
chrisx


Location: Portland
Posts: 407


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« Reply #21 on: June 24, 2014, 08:24:29 PM »

symbiosis
n. noun
A close, prolonged association between two or more different organisms of different species that may, but does not necessarily, benefit each member.
A relationship of mutual benefit or dependence.

Zo; I am now contacting German scientists to analyze bicycle discusion for me.  Russian guy is telling me his German scientist is smarter than mine German scientist.  I am not thinking that.

I think I will have the Mexicans paint my old bicycle, while I wait for the German cogitation of the Australian nomenclature.  Conceivably; the Canadians will post photos of another bicycle endeavor while I scratch my head.

https://www.youtube.com/watch?v=nzciD09URjg
« Last Edit: June 24, 2014, 08:35:16 PM by chrisx » Logged

  Topic Name: bike geometry for up and down hill--------- Reply #22 on: June 25, 2014, 07:00:44 AM
juanesunpescado


Posts: 38


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« Reply #22 on: June 25, 2014, 07:00:44 AM »

perspicuous
adjective
not Chrisx ;-)
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  Topic Name: bike geometry for up and down hill--------- Reply #23 on: June 25, 2014, 11:07:33 AM
chrisx


Location: Portland
Posts: 407


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« Reply #23 on: June 25, 2014, 11:07:33 AM »

A well educated person could make a better decision
http://janheine.wordpress.com/2011/02/10/a-journey-of-discovery-part-4-front-end-geometry/

per·spic·u·ous  [per-spik-yoo-uhs]  Show IPA
adjective
1.
clearly expressed or presented; lucid.
2.
perspicacious.
Origin:
1470–80;  < Latin perspicuus  transparent, equivalent to perspic-,  stem of perspicere  to look or see through ( per- per- + -spicere,  combining form of specere  to look; see inspect) + -uus  deverbal adj. suffix

https://www.youtube.com/watch?v=yZVcRGB1KdQ
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  Topic Name: bike geometry for up and down hill--------- Reply #24 on: June 28, 2014, 05:10:46 AM
Jonathan


Location: Oviedo FL
Posts: 13


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« Reply #24 on: June 28, 2014, 05:10:46 AM »

Isolating head angle and fork rake/offset is a bit simplistic. Suspended bikes are also dynamic when being used so those numbers move all over the place anyway, especially when going down hill so I've never seen how calling out one number made sense. Fork options are limited anyway. We usually prefer x brand fork and choose a price point whithin that brand. Rarely do folks pick a fork offset when buying a fork which is why those numbers are often hard to find on consumer sites. When I build a road fork I can build the fork around what head tube angle I've designed into the frame to give the steering and front center dimension I'm after. On a mountain bike it's the same but fork choice is limited. You pick a geo that works for steering but the front center measure and where it places a rider between the wheels is probably more important for how a bike will travel down hill. That's my .02 on how I design a frame.
« Last Edit: June 28, 2014, 11:30:13 AM by Jonathan » Logged


  Topic Name: bike geometry for up and down hill--------- Reply #25 on: July 02, 2014, 12:15:39 AM
Adam Alphabet


Location: Vancouver, BC
Posts: 968


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« Reply #25 on: July 02, 2014, 12:15:39 AM »

Conceivably; the Canadians will post photos of another bicycle endeavor while I scratch my head.
https://www.youtube.com/watch?v=nzciD09URjg

From this weekend.... solo few days in the Chilcotins. Little Paradise Creek Trail, yup, get to descend alllll the way down there. scratch away.



* Little Paradise Top.JPG (278.53 KB, 992x744 - viewed 179 times.)

* Little Paradise Bottom.JPG (287.62 KB, 992x744 - viewed 174 times.)
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@adamalphabet

  Topic Name: bike geometry for up and down hill--------- Reply #26 on: July 05, 2014, 07:48:43 AM
james-o


Location: South-East, UK
Posts: 126


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« Reply #26 on: July 05, 2014, 07:48:43 AM »

Frame geometry is not the only thing to consider, you have to look at it wholistically.

Take the new Fsi 29 from Cannondale. They've re-written their book on what a fast and efficient 29 should be, slacker head angle (there's that slacker word again) but have mated it with a fork rake and length that matches the frame geo to meet their handling objectives. Shorter stays and an offset rear (think pugsley/moonlander) for stiffer rear wheel build and chainline improvement. System integration is what they call it, but I look at it as 2 components that are designed together. I'm not a dyed in the wool Cannondale fan, but I respect their engineering for performance based outcomes.

Head angle geos mean nothing if the fork is not matched to create a neutral handling front with positive caster.

Sounds like more and more brands are picking up on what Jeff Jones has advocated for many years. I can think of at least 4 or 5 brands switching on to the trail/HA balancing thing now, possibly helped along by the early Fox / GF G2 29er fork rake options.
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