Suspension Travel Troubles??

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Suspension Travel Troubles??

Postby glawrence2000 » Mon Nov 24, 2008 2:11 pm

Lads,

Why is it that suspension never seems to be able to travel the advertised amount?
For example; my White Brothers Magic 29er forks have an advertised travel of 110 mm. Yet even under the most extreme conditions the travel gauge (little black cable tie) never deflects that distance along the fork.

I have set the shock up as per the instructions, with the correct air and sag and rebound yet - nada. Even when I completely bleed the fork, it collapses to around 100 mm and you virtually have to stand on the thing to get the 110 mm out of it.

I have a similar issue with a DT Swiss rear shock which has a full travel of 6.5 cm which through the levers etc equates to 4 inches of travel. No matter what punishment I give it, max travel in the shock is around 5 - 5.5 CM. This equates to quite a bit less travel than one would expect (and pay for).
If I bleed this shock it goes to it's full travel no worries; but set up by the book with the right amount of sag; it never goes anywhere close to the limit.
So taking into consideration sag as a start point and the limit it reaches when set up correctly; does my 4" travel become more like 2 inches?

Similarly I have the same sort of issue with another (claimed) 100 mm air shock.

What's the deal here? Are we getting jipped into buying 80 mm shocks when we are thinking they are 100 mm, and 100 mm when we think we are getting 110 mm.

Any thoughts? Confirmations of my conspiracy?
Thanks heaps.
BMC 4Stroke 03. (web nazis won't let me put a third picture up :()
Voodoo Dambala 29er.
FELT AR4 Carbon.
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by BNA » Mon Nov 24, 2008 3:57 pm

BNA
 

Postby Kalgrm » Mon Nov 24, 2008 3:57 pm

G'day mate,

My first question is "But do you still enjoy the ride, even if you can't use all the suspension travel?" If so, don't worry about it. If not, maybe there really is a problem.

The amount of sag suggested is really only a suggestion - you can change that. You also have the choice of changing how much damping there is, so you can blow through all the travel if you like.

However, that little bit of room remaining in the travel serves a purpose. It's protection against that one big hit you'll put the bike through at some stage. If you regularly hit the end of the travel, you'll soon kill the shock absorber.

Basically, if you find yourself on track where you're always using all of your travel, you should consider getting a bike more suited to those tracks. 4" of travel is well suited to XC riding (I doubt I've every used all of mine in that application - and most likely won't). If you need more, get an "all mountain" design instead.

Cheers,
Graeme
Think outside the double triangle.
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Postby Bnej » Mon Nov 24, 2008 8:12 pm

Air shocks are progressive and some of the hate bottoming out.

Fox especially - they are very light at the start and ramp up quickly. I get about 80% travel on my F100s most of the time, very rarely use the last little bit.

This is part of the design of the shock. If you want a more linear rate, either a larger air volume or a coil spring shock is more suitable. Rock Shox provides a more linear rate air spring than Fox for example.

Some bikes also have a falling rate linkage that combined with a rising rate shock will give a linear spring rate.
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Postby glawrence2000 » Tue Nov 25, 2008 10:57 am

Understood - thank you both; but don't you think that they would put the bottom-out bumpers at the limits of the shock rather than in the advertised travel?

Having said this - all my shocks do perform admirably and seem to cope with my random riding. I don't think I need anymore suspension, (nor will wife or innercity townhouse cope with another bike inside :oops: ) just want to have what I'm supposed to have; else I could have stayed with my 80mm Marzoochi which did travel 80 mils being nice and linear.

Cheers.
Thanks heaps.
BMC 4Stroke 03. (web nazis won't let me put a third picture up :()
Voodoo Dambala 29er.
FELT AR4 Carbon.
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Postby Bnej » Tue Nov 25, 2008 7:51 pm

glawrence2000 wrote:Understood - thank you both; but don't you think that they would put the bottom-out bumpers at the limits of the shock rather than in the advertised travel?


There isn't a bumper stopping it, just the air spring gets smaller with the same amount of air, which progressively ramps up the spring rate.

Advertising 100mm (say) is correct in that it's the limit that the fork can travel. If they said 92mm give or take 10mm depending on your pressure settings then it would be a bit of an odd spec. ;)
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