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PostPosted: Thu Aug 18, 2011 1:41 am 
Old School Hero
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Joined: Sun Mar 27, 2011 2:09 am
Posts: 235
Location: Hull, Humberside
MEASURING SUSPENSION TRAVEL:

FRONT SUSPENSION:
FITTING: Fit "A" Zip Tie (Cut off the excess end) to EACH UPPER fork leg.
USING: Push the zip ties to the bottom of each upper fork leg.

BEFORE RIDING, sit on your bike to check if your weight causes your suspension fork to sag, measure with a ruler the distance the zip tie has moved from the btm of the upper fork leg, then make a note of the sag (Eg 1cm to 2cm).
AFTER RIDING, measure with a ruler the distance the zip tie has moved from the btm of the upper fork leg, (If BEFORE riding your weight caused your suspension fork to sag, minus this from your total travel eg 8cm - 2cm = 6cm travel).
Image

NOTE: My forks (Rock Shox Judy TT), I ride at the hardest setting, with my weight 10.5 st, have zero sag/travel when I sit on my bike. When I ride approximate travel of my front suspension is as follows:
~ road riding, 2cm to 4cm
~ hard off road riding, upto 8cm

REAR SUSPENSION: (If your rear suspension air shock doesn't already have a rubber O-Ring for measuring suspension travel)
FITTING: Fit "A" Zip Tie (Cut off the excess end) to the shock body.
USING: Push the zip tie to the bottom of the shock body, hence sitting next to the shock air sleeve.
Image
BEFORE RIDING, sit on your bike to check if your weight causes your rear suspension air shock to sag, measure with a ruler the distance the zip tie has moved along the shock body, then make a note of the sag (Eg 1cm to 2cm).
AFTER RIDING, measure with a ruler the distance the zip tie has moved along the shock body, (If before riding your weight caused your rear suspension air shock to sag, minus this from your total travel eg 8cm - 2cm = 6cm travel).

If the above seems stating the obvious to some people, well it isn't obvious to those who don't know! An ironism, I know, the world is full of paradox's, suspension can be so good, you don't how much shock it's absorbing, also if suspension is set too soft, this could be ineffective as suspension bob maybe absorbing your energy.


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PostPosted: Thu Aug 18, 2011 9:24 am 
retrobike rider
retrobike rider
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Location: Yorkshire, England
All forks should have some sag when you sit on on, if it doesn't then it's setup wrong.

Most (I think, someone will correct) 80mm+ forks are designed to be set at ~25% sag. There is good reason for this as well, it keeps the forks in contact with the ground when there is a sudden drop in the road, rather than you going in to it.

I don't know what rear suspension should be set at but the user manual would tell you.


To get the sag you may need to alter the preload or some other fancy gubbins in modern forks. If it still will not drop then you need a lighter spring/different oil or they need a clean/service as they are sticking too much not allowing your weight to move them as they should.

If you find you're burning through the travel or not using it all then adjust the damping/spring setup to fit.


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PostPosted: Thu Aug 18, 2011 12:08 pm 
Dirt Disciple
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Joined: Mon Jun 28, 2010 8:03 pm
Posts: 93
Location: North Cornwall
I agree with fluffychicken that All forks should have some sag when you sit on ...

Its not just push bikes it all suspension...

We always setup motor trials bikes with a 3rd sag front and back and the main thing is to get the front and back working the same....


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PostPosted: Thu Aug 18, 2011 12:37 pm 
Old School Hero
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Joined: Sun Mar 27, 2011 2:09 am
Posts: 235
Location: Hull, Humberside
I sense some form of sarcasm here, obviously the Zip ties IF secured tightly will NOT drop to bottom of the suspension fork upper leg, AFTER front suspension fork travel, also IF the zip ties are secured adequately, so as AFTER movement the zip tie does not fall back to the lowest point (Hence this would happen if the zip tie was too loose).
And to contrary once the zip ties are adequately tight enough, the zip ties do not prevent/reduce travel, as the force to move the suspension is far greater then the friction that the zip ties will exert on the suspension fork upper legs.

However, perhaps your comments weren't sarcastic:

Well GEOMETRY and SUSPENSION softness/hardness/quickness/slowness is a subjective matter, not everybody knows what is best for themselves, but that suits my riding.

I understand your points, obviously riding terrain, the suspension travels significantly under impact/shock, any softer and too much travel bob during normal riding for my liking.

I personally think many people ride with their suspension far too soft, I'd rather it takes the edge off significant impacts, such as:
drop offs, jumps, dips, and uneven terrain, and reducing vibration to not noticeable, whilst NOT absorbing my cycling effort unnecessarily.


Perhaps this is because local terrain is a not fun balance of:
incredibly short descents,
unnecessarily long hills, and
renowned vertical cliffs that will surely be many peoples death, that many regard as challenges.

Well Hull certainly isn't the Pyrenees...... In fact the countryside near Hull it's like a sentence describing cycling in the countryside, only an insight, that was taken literally, or too seriously, that misunderstood sarcasm. Almost as if intentionally landscaped around such concept, but I’m sure neighbouring counties, hold as few pleasant surprises, such as lengthy enjoyable descents.


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PostPosted: Thu Aug 18, 2011 1:02 pm 
retrobike rider / Gold Trader
retrobike rider / Gold Trader
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Joined: Sat Jan 27, 2007 10:35 pm
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Location: The desolate flats of Cambridgeshire
I heard suspension travel was directly proportional to penis size.


Sorry that was sarcasm of course I meant inversely proportional.


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PostPosted: Thu Aug 18, 2011 4:00 pm 
retrobike rider
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Location: Yorkshire, England
No sarcasm at all and nothing to do with zip ties, just commenting on sag.

The sag is there to give the fork travel in the opposite direction so if you go over a dip (say a small hole) the fork extends into it then takes the sting out the other side. It should be no less stiff at that sag point than you would like as you alter other parts to get it back there.
It should reduce cycling efforts if setup and use properly but should keep you in contact with the ground and comfier with more control.

It's a far cry from the early 90's forks, like the RockShox MAG's I and many people on here still use where they where pretty much designed to take the tree stumps and rocks out with little thought for ground buzz and have next to no sag. (and travel as it goes ;)) but they're perfectly fine for anything around here even the quarries as tested some 16+ years back :lol:

You'll have to ask the modern riders how really modern things work though, my modern fork is a top end 1999 Bomber Air/Oil fork.
What does Iain have on his new bike ?


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 Post subject: Iain's MTB
PostPosted: Fri Aug 19, 2011 12:47 am 
Old School Hero
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Joined: Sun Mar 27, 2011 2:09 am
Posts: 235
Location: Hull, Humberside
Anyway Ben, Iain's MTB is a Gary Fisher Wahoo 2010

http://www.evanscycles.com/products/gar ... C#features

Different to the 2011 model
http://fisherbikes.com/bike/model/wahoo

Doesn't say what fork the 2010 has, I thoughr they were Bontrager or Suntour Coil something or other, well not Air forks.


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PostPosted: Sat Aug 20, 2011 2:09 am 
Old School Hero
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Joined: Sun Mar 27, 2011 2:09 am
Posts: 235
Location: Hull, Humberside
Here are some definitions of suspension, of MTB's:

PRELOAD: Softness/Hardness (Depends on rider weight, and terrain)

REBOUND: Quickness/Slowness (Of suspension movement)

LOCKOUT: Lock Out! (Minimum suspension movement)

Go on, put it better!

MOTOCROSSERS that buy MTB FULL SUS
Another thought years before MTB's had suspension, I rode Motocrossers and thought they were/are a lot of fun, with their soft suspension (Another thought wow suspension could do with that on a MTB), and in not having to exert any effort to gain momentum (Such as cycling effort), instead just twist accelerator with the handlebar grip.

But I wouldn't want suspension that soft on a MTB, as this pedal bob, would be counter productive in soaking up your efforts, that would be wasted energy.

I understand why many motocrossers, who buy MTB's run their suspension really soft, or have DH MTB's instead of XC MTB's, but perhaps this is because of what they are accustomed to, instead of what is a good productive setting for them, well a subjective area, but you could set up the PRELOAD right for them (Their weight), and tell them to adjust just the REBOUND, and tell them to use the LOCKOUT for uphills and even terrain flat tracks and roads.

Well Motocrossers to generalise don't talk much sense, to be fair.


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PostPosted: Sat Aug 20, 2011 12:23 pm 
Old School Grand Master

Joined: Sun Jun 27, 2010 9:37 am
Posts: 3976
srands wrote:
Here are some definitions of suspension, of MTB's:

PRELOAD: Softness/Hardness (Depends on rider weight, and terrain)

REBOUND: Quickness/Slowness (Of suspension movement)

LOCKOUT: Lock Out! (Minimum suspension movement)

Go on, put it better!

ok, preload sets sag not firmness, allthough it will have an effect if its a ramping set up rather than linear

rebound changes the speed of the fork extension not compression, thats compression adjustment. these can be split into high speed/slow speed circuits on high end forks

lock out, well yeah thats right.

But I wouldn't want suspension that soft on a MTB, as this pedal bob, would be counter productive in soaking up your efforts, that would be wasted energy.

I understand why many motocrossers, who buy MTB's run their suspension really soft, or have DH MTB's instead of XC MTB's, but perhaps this is because of what they are accustomed to, instead of what is a good productive setting for them, well a subjective area, but you could set up the PRELOAD right for them (Their weight), and tell them to adjust just the REBOUND, and tell them to use the LOCKOUT for uphills and even terrain flat tracks and roads.

Well Motocrossers to generalise don't talk much sense, to be fair.


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 Post subject:
PostPosted: Sat Aug 20, 2011 12:32 pm 
Moderator /Lincs, E & S Yorks Deputy AEC
Moderator /Lincs, E & S Yorks Deputy AEC
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Joined: Mon Nov 26, 2007 6:16 pm
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Location: RetroModding™ since 1988
What about low and high speed compression damping?

Also what about floodgate lockout blow off systems?

Low speed compression damping can eliminate pedal bob

High speed compression damping can stop the fork or shock spiking

Suspension sag should start at approx 25% for XC riding, 30% for trail riding & up to 40% for DH riding

This applies to both front and rear shocks

A lot of rear shocks already have low speed compression damping built into them so the pedal bob is drastically reduced

But too much low speed compression damping will reduce the small bump sensitivity of the fork/shock, meaning that the wheel will not always be in contact with the ground

Keeping your wheels in contact with the ground is what suspension is for, more ground contact = more control = faster riding


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