Tech Question...What will fitting a shorter rear shock do to my head angle?

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Tech Question...What will fitting a shorter rear shock do to my head angle?

13 posts & 8 voices | Started 4 months ago by bloodyshins | Latest reply from bloodyshins

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bloodyshins - Member

Hi Guys, I'm cuttently riding a Giant reign X with a fox vanilla RC on it. I love the bike but I'm looking to make it a bit more playful and 'hoppable' by fitting an air shock.

Now for the tricky bit. I have an old Kona dawg frame gathering dust and I'm thinking of trying the Fox RP3 from the Kona in the Giant. The giant is designed around a 200mm shock with a 57mm stroke. The Air shock from the Kona is 190mm long with a 50mm stroke.

Ive figured out that due to the 3:1 leverage ratio of the Giant, the shorter stroke shoke will give me 150mm trave (I'm happy to loose 20mm) but what will the loss of 10mm from the shock length do to the head angle? The bike currenly sits at 68 degrees...

Any clever people able to help me out?

Posted 4 months ago #
Conan257 - Member

You're talking of a 20mm drop in terms of the rear wheel, over a wheelbase of around 1100mm....

Can't be bothered with the maths, but I think about 2 degree's is what you could expect...

Bear in mind the BB will drop by a little as well.

Posted 4 months ago #
float - Member

and your wheel will hit the seat tube

Posted 4 months ago #
Conan257 - Member

The final point for the wheel will only be 9mm further up/forward than it is normally... That shouldn't make a massive difference

Posted 4 months ago #
goodgrief - Member

Posted 4 months ago #
STATO - Member

I tried it with a Kona Stab Primo a few years back, dropped .5" from shock length and stroke so no bottomout issues tho. Generally it rode nicer due to the slack angles and lengthened wheelbase but kept striking the pedals a lot. Id imagine you should be ok with 10mm drop and as you have less travel youll prob set it up to have less sag so overall the static (when seated) change wont be drastic. Give it a shot.

Posted 4 months ago #
DrP - Member

The head angle will be 'a bit' slacker, the rear wheel will end up 9mm closer to the seat tube.
On some bikes, that's game over....

DrP

Posted 4 months ago #
bloodyshins - Member

Cheers guys, I think I'll give it a go... I've got nothing to loose. Float, I don't think the wheel will hit the seat tube as the stroke of the shock is 7mm less, so that means it should bottom out only 3mm closer I think, I'll obviously cycle the shock with no air in it to be sure.

Posted 4 months ago #
Conan257 - Member

It'll bottom out 3mm higher up in terms of the shock, then you need to add the leverage ratio in as well...

Still, shouldn't be an issue.

Posted 4 months ago #
Northwind - Member

Test clearance first, there's plenty of well-packaged bikes that won't tolerate any reduction of shock length, and Giant tend to make very well packaged bikes.

Posted 4 months ago #
Rickos - Member

Just check it won't strike anything at full travel with all the air out of the shock. If it doesn't then it'll be nice. Slacker, lower BB and good fun. Did a similar thing with a Kona Howler, although it was a 200x50 swapped out for a 190x50.

Posted 4 months ago #
Northwind - Member

Oh and remember it can't just not hit, it needs a bit of extra room for mud and flex. Don't arsk me how I knows, I just knows, also don't ask about the sticker covering the paint damage on my Hemlock.

Posted 4 months ago #
bloodyshins - Member

So I fitted it... there are no clearance issues whatsoever, ifact it bottoms out a good 20mm before the wheel would hit the seat tube (there is a brace on the rear triangle that would hit first anyway). It looks very slack, a quick bomb up the road makes me think its going to be a lot of fun, very easy to hop about. Although with that head angle and lack of travel adjust forks I doubt I'll hve much controll of my direction on the cilmbs... Should be interesting.

Posted 4 months ago #

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