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PostPosted: Tue Feb 22, 2011 11:05 pm 
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I'm thinking of taking the Fox F100 forks off my Kona Hei Hei 100 and swapping them on to my hard-tail. To replace the F100s, I was debating changing to Fox F120s as the Hei Hei steers really fast and I've whacked the crank arms a few times going over rocks.

I think the F120 will raise the front end up a tad, slackening the head angle and will give a bit of extra ground clearance. On the back I have a Fox RP23, which gives 100mm travel. Any problems with having a bit more travel on the front rather than the back?

http://www.singletrackbikes.co.uk/produ ... _RP23_2010

SP[quote][/quote]


Last edited by Splatter Paint on Thu Feb 24, 2011 9:49 pm, edited 1 time in total.

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PostPosted: Tue Feb 22, 2011 11:08 pm 
Moderator /Lincs, E & S Yorks Deputy AEC
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So long as the frame is tough enough and it doesn't slacken the head angle too much it should be OK (20mm more axle to crown is roughly a 2° change in Head angle)

Quite a few bikes as std have different amounts of travel front & rear so it's not unusual to do it.


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PostPosted: Wed Feb 23, 2011 8:33 am 
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Andy B wrote:
So long as the frame is tough enough and it doesn't slacken the head angle too much it should be OK (20mm more axle to crown is roughly a 2° change in Head angle)

Quite a few bikes as std have different amounts of travel front & rear so it's not unusual to do it.


20mm is approximately a 1° head angle change, not 2°. It'll be fine, in my opinion.


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PostPosted: Wed Feb 23, 2011 9:40 am 
Moderator /Lincs, E & S Yorks Deputy AEC
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Andy R wrote:
Andy B wrote:
So long as the frame is tough enough and it doesn't slacken the head angle too much it should be OK (20mm more axle to crown is roughly a 2° change in Head angle)

Quite a few bikes as std have different amounts of travel front & rear so it's not unusual to do it.


20mm is approximately a 1° head angle change, not 2°. It'll be fine, in my opinion.
I was always led to believe that every 10mm change in axle to crown was a 1° change in head angle :?

Anyhoo, the bike should be fine with 20mm longer forks on it.


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PostPosted: Wed Feb 23, 2011 9:54 am 
retrobike rider
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Andy in 'Retro bike' 1" is about 1degree (technically standard frame and 20mm is 1deg, but 25mm after sag is really nearer the 1degree change)

Of wheelbase and other things will probably alter that relationship.

Though the move from 100 to 120 isn't a total of 20mm it's a tad less as you have a touch more sag.


Splatter, stick a ~2cm thick book under the front and sit and track stand and see how you like it ;) OR flatten you back tyre :lol:

Remember to re tweak you rear suspension if it needs it with the extra weight placed on it and change in initial seat angle (might not need it I'm rear sus illiterate)
Don't forget there are a lot more 'initial position' changes that just layback, effective top tube length changes, bb higher is about 1cm higher (as you want) etc..
oh I remeber a link, have a play http://bikegeo.muha.cc/


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PostPosted: Wed Feb 23, 2011 2:17 pm 
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If it's on the fast side and you're struggling for pedal clearance it should work well. Just check that the frame's warranted for it. I'd be tempted to nudge the saddle forward and drop the bars a bit lower to get yourself more over the front and work the fork more.


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PostPosted: Thu Feb 24, 2011 9:51 pm 
retrobike rider
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Good idea Fluffy Chicken, I'm going riding at the weekend, so before I go I'll raise the front end up 20mm on books and then see how it feels. Fox forks are crazy money now, so I'll need to keep an eye out for a bargain.

SP


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