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Author Topic: Bike Handling: Geometery Questions  (Read 2086 times)

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Offline Pariah

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Bike Handling: Geometery Questions
« on: March 08, 2011, 07:49:58 AM »
So does a 71 degree head angle make much difference when compared to a 70 degree head angle?  If so how noticable is that difference?  What affect does it have on the ride?  What about wheel base say 44"  vs 44.5" - does an extra half inch matter?  How about chain stay length?  longer vs. shorter?
 
 
 
 
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Offline mellowme17

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Re: Bike Handling: Geometery Questions
« Reply #1 on: March 08, 2011, 08:08:07 AM »
it all matters to me.... the reason why i have been through so many frames...
don’t forget about the seat tube angle as well.
the carbon rigid i was riding had a head angle of 72degree as my redline is closer to 70.
the rigid was much more twitchy, very fast handling but was not confidence inspiring in the steeper technical stuff..
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Offline Pariah

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Re: Bike Handling: Geometery Questions
« Reply #2 on: March 08, 2011, 08:13:38 AM »
good info - the seat tube angle on the bikes I am considering are the same as what I currently own - no change.  The head tubes change is only 1 degree from 70 to 71 so I figure its not much of a change, will it truly be noticable?  I currently run my stem in a -10degree rise so its already lowering me postion to more over the front wheel vs. more upright...
 
thanks for the input, My goal is a fast handling bike, less effort to make sharp corners at speed, ect...
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Offline mellowme17

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Re: Bike Handling: Geometery Questions
« Reply #3 on: March 08, 2011, 08:30:10 AM »
well…. Handling is all subjective to the rider…. People will say slacker angles will be slower and steep is what you want… personally I believe frame selection is like tire selection… try out as many as you can to find what fits best… when I can get the frame  I want the HA will be 69degrees with chain stays around 16.7 to 16.5 and tire clearance for 2.4’s
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Offline chainslap

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Re: Bike Handling: Geometery Questions
« Reply #4 on: March 08, 2011, 08:31:59 AM »
One degree will be noticeable.  Ride a bike with adjustable fork travel and you can demonstrate this.  I usually ride the Epiphany at 120 and occasionally at 100 rather than the full 140,  it makes it a lot more snappy in the turns.  Remember that these angles will be effected by the sag settings, some specs reflect sag others do not.  The chain stay length matters as well, especially on a 29er.  The shorter it is, the quicker it will turn.  Bigger wheels make it hard to shorten this up.  Max tire size and front der. mounting are often obstacles.  What bike are you replacing? What frames are you looking at?

Offline Pariah

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Re: Bike Handling: Geometery Questions
« Reply #5 on: March 08, 2011, 08:43:49 AM »
the anthem X and the Truth frames...  vs. the handling of my Epiphany
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Offline Orion_134

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Re: Bike Handling: Geometery Questions
« Reply #6 on: March 08, 2011, 08:48:01 AM »
When I changed from 80 to 100mm travel on the front of my 71* HT bike, it slackened it up (to what I don't know) but it wasn't noticeable.  YMMV.
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Offline chainslap

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Re: Bike Handling: Geometery Questions
« Reply #7 on: March 08, 2011, 09:02:56 AM »
Swaping the Float 140 for a F120 will make a difference and loose a bit of weight.  I would bet that the Epiphany is more like 69 deg at 140.  If I had to choose 1 travel setting on that bike, the 120 would be a no brainer.  If I remember correctly, Art traded in his Epiphany for a Truth.  Probably a good person to ask on that front.

Offline Redriderpro

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Re: Bike Handling: Geometery Questions
« Reply #8 on: March 08, 2011, 09:09:21 AM »
Run the EPI in 100 mm fork mode ( like you would have on either 100 mm equipped bike you're looking at) and it will turn much faster than at 120 or 140.
 
I suspect one of the reasons the new Epi has 140 mm of rear travel  Vs the older ones with 130 mm,is because of people having problems turning it with a Talas fork in the 140 setting. ( My bud Tom is a good example)
 
Sag in the fork or shock can change cornering greatly. Try this, run 10-15 more psi in you shock than you usually do, with the 140 fork setting. Quicker turning will be the result.( along with a harsher ride)
Or, run 10 psi less in the fork, again you will see quicker turning.
 
Both of those changes will make the straight line at speed and steep stuff less stable though.
 
Narrower bars and or a lower stem will quicken up the steering as well.
 
* One's cornering style can also overcome common assumptions about bike geomentery.
I'd be willing to bet that there are some people on 6" travel bikes that corner as fast as just about anyone on a 4" travel bike with steeper angles.
 
Bottom line: Ride as many different bikes as possible, set up for you weight/fit and buy the one that does what is most important to you with the least amount of effort. ( Numbers, measurements are not everything) 
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Offline Alan

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Re: Bike Handling: Geometery Questions
« Reply #9 on: March 08, 2011, 10:28:03 AM »
If you want to experiment with headtube angle Cane Creek makes this headset where you can adjust the angle:  http://www.canecreek.com/component-headsets?browse=Complete&name=AngleSet

Offline Redriderpro

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Re: Bike Handling: Geometery Questions
« Reply #10 on: March 08, 2011, 10:49:08 AM »
Kevein got "newbikeitis"... just a new headset aint gonna be the cure
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Offline mellowme17

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Re: Bike Handling: Geometery Questions
« Reply #11 on: March 08, 2011, 10:58:59 AM »
If you want to experiment with headtube angle Cane Creek makes this headset where you can adjust the angle:  http://www.canecreek.com/component-headsets?browse=Complete&name=AngleSet


Dont think that would fit his bike...
you would probably be happier with the truth....  but might miss that extra travel...
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Offline $irWattZZZZ

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Re: Bike Handling: Geometery Questions
« Reply #12 on: March 08, 2011, 11:22:49 AM »
Did you test ride an X at Alfia?

Offline Pariah

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Re: Bike Handling: Geometery Questions
« Reply #13 on: March 08, 2011, 12:33:17 PM »
sure did scott - it shifted for *, pinch flat the front in the 1st 5 minutes, walked to trail head, had them fix that...then got a flat on the rear on the way out of rollercoaster
 
 
maybe had all of 15-20 minuteson the bike before saying screw it.... 
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Offline $irWattZZZZ

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Re: Bike Handling: Geometery Questions
« Reply #14 on: March 08, 2011, 01:14:35 PM »
sure did scott - it shifted for *, pinch flat the front in the 1st 5 minutes, walked to trail head, had them fix that...then got a flat on the rear on the way out of rollercoaster
 
 
maybe had all of 15-20 minuteson the bike before saying screw it....
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