Front wheel digging in on slow turns

I'm relatively new to front suspension so it took me a while to identify what was happening even though I recognised something right away.

Say for instance you're climbing quite slowly, bit of a struggle, you need to avoid something and make one of those quick flicks with the bars, short and sharp. At that point I feel the front dig and the suspension compress. Similar thing happens if I misjudge a corner and end up going too slow, the front cuts in too much because I'm not carrying enough speed ( is that oversteer or understeer?). Apart from becoming a better rider, can this be adjusted with an adjustment of fork pressure, tyre pressure or handlebar/stem length? I have increased the fork pressure a bit but I can't remember if that improved it :wacko:

There's nothing wrong with the bike by the way. I've noticed the same thing on other bikes I've hired.
 
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Location
Loch side.
Your fork's rebound setting is set for too slow. What is happening is that your fork is packing up and when it is very low (compressed), you are making a turn. That turn is done with a bike with an effectively steeper head tube angle which causes that digging in feeling when you turn. You don't say what type of fork it is but most of them have rebound settings. It is not a pressure issue at all, unless your sag is completely wrong and you experience what you describe all the time.

Edit: Packing up is when the fork compresses, through a series of bumps, faster than it can return. For instance, first bump is 5mm, recovery time is short before the second bump and the fork only returns 2mm. Second bump is 5mm, recovery time is short before the third bump and so forth.

If you stop, or hit level ground, it will "unpack" again.
 
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13 rider

Guru
Location
leicester
While riding on the road I find it easier to have the front suspension locked out. Are you talking about off road or road riding ? .is locking the suspension while on road an option for you
 
OP
C

Crackle

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Your fork's rebound setting is set for too slow. What is happening is that your fork is packing up and when it is very low (compressed), you are making a turn. That turn is done with a bike with an effectively steeper head tube angle which causes that digging in feeling when you turn. You don't say what type of fork it is but most of them have rebound settings. It is not a pressure issue at all, unless your sag is completely wrong and you experience what you describe all the time.

Edit: Packing up is when the fork compresses, through a series of bumps, faster than it can return. For instance, first bump is 5mm, recovery time is short before the second bump and the fork only returns 2mm. Second bump is 5mm, recovery time is short before the third bump and so forth.

If you stop, or hit level ground, it will "unpack" again.
That's the kind of info I was looking for. I've only very roughly set the rebound, so I obviously need to look at that again and see if I can improve things. They are x-fusion forks.

Edit: I initially set the fork pressure just according to weight and then altered it, taking some out after a few rides and I could see how much travel I was using. Rebound I set only on feel when I gave the forks a sharp push.
While riding on the road I find it easier to have the front suspension locked out. Are you talking about off road or road riding ? .is locking the suspension while on road an option for you
No, not on the road and it does lockout.
 
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GrumpyGregry

Here for rides.
When climbing lock it out. Last thing you need as you crawl up a bit-of-a-struggle-slope with the handlebars flapping from side to side is the steering geometry changing. Remember to unlock before you give it some beans on the other side though ;)

The only time I've had a fork pack up uphill was on the Trans-Cambrian when the air seals went pop. Downhill, yeah, my avoirdupois can make a badly setup fork packup at speed. Not pleasant at all.

tbh I struggling to visualise the problem from your description.But here goes...

It sounds as if you may not have enough weight over the front end of the bike, we used to say you should be kissing the stem on a low speed uphill climb, and/or you are overcorrecting your steering at low speed when the front wheel gets deflected. If the latter lower tyre pressures may help the tyre to deform and roll over an obstacle rather than bouncing and deflecting off it and making the bars move grossly.

What we really need is @Cubist He's quicker on the uptake than me and talks more sense off-road.
 
OP
C

Crackle

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When climbing lock it out. Last thing you need as you crawl up a bit-of-a-struggle-slope with the handlebars flapping from side to side is the steering geometry changing. Remember to unlock before you give it some beans on the other side though ;)

The only time I've had a fork pack up uphill was on the Trans-Cambrian when the air seals went pop. Downhill, yeah, my avoirdupois can make a badly setup fork packup at speed. Not pleasant at all.

tbh I struggling to visualise the problem from your description.But here goes...

It sounds as if you may not have enough weight over the front end of the bike, we used to say you should be kissing the stem on a low speed uphill climb, and/or you are overcorrecting your steering at low speed when the front wheel gets deflected. If the latter lower tyre pressures may help the tyre to deform and roll over an obstacle rather than bouncing and deflecting off it and making the bars move grossly.

What we really need is @Cubist He's quicker on the uptake than me and talks more sense off-road.
I'm still not a 100% certain of the exact circumstances and I don't want to overegg it, it's not huge, I just want to know if I can improve it. I can't lock out as I'm riding up over stepped 4" sleepers. Well I could, I used to ride it on my rigid but the effort to climb and get the bike over the sleepers, was, well, fekkin hard, there's no comparison to letting the forks take it. I did lower the stack height a while back and I naturally lean forward when climbing but I'll examine that next time I go grunt my way up it.

I might be being picky but I thought I'd ask.

Edit: front tyre pressure is about 25.
 

Levo-Lon

Guru
Set your sag to 25% in attack postion and as above on the rebound.
tyre pressure will also be trial and error but try around 30psi and then 25psI etc.
once you find the sweet spot jobs a good un
 

Cubist

Still wavin'
Location
Ovver 'thill
It does sound like its packing down, as your weight is forward as you're turning in. Rebound damping is always a matter of personal taste and riding style, but you can get somewhere near by riding off a kerb or a little drop and seeing how the fork recovers its stroke. Ideally you want something that recovers pretty fast without bouncing or topping out, but that's easier said than done without trial and error. Also, 29ers do have a steepish head angle thanks to their geometry, so you might need to consider a weight shift.... Neutral through tight turns, and try to keep your weight central over the BB.

The slant has a very supportive mid stroke, and if your pressures are right then you shouldn't get too much dive. Try it at 25% sag as @meta lon suggests. Oh, and try to carry as much speed as those clown wheels allow.......:o)
 
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OP
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Crackle

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I spent a bit of time re-setting things. 25% sag in attack position; check. This equates to about 80psi, which roughly agrees with the weight chart on the forks. I think I started at 80, went to 90, then dropped to 70, so now back at 80. Rebound is set in the top third now as opposed to about 50%. The response is not linear though and the top third is quite a bit sharper than 50%. Hopefully repeat the last ride on it sometime late next week and see if it feels better.
 
Location
Loch side.
I spent a bit of time re-setting things. 25% sag in attack position; check. This equates to about 80psi, which roughly agrees with the weight chart on the forks. I think I started at 80, went to 90, then dropped to 70, so now back at 80. Rebound is set in the top third now as opposed to about 50%. The response is not linear though and the top third is quite a bit sharper than 50%. Hopefully repeat the last ride on it sometime late next week and see if it feels better.
I'm not sure what action of the fork you say is not linear.
Those forks have a fluid damper that acts exactly the same anywhere in the stroke, therefore damping is linear.
However, because it is not a coil spring fork but an air spring, the spring itself is not linear and becomes harder (the spring rate decreases) as the fork is compressed. Soft at first, then harder and harder as it is compressed.
I suspect that you suspect the damping is not linear. This will confuse you in getting to the right setting. It is perfectly linear.
 
OP
C

Crackle

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I'm not sure what action of the fork you say is not linear.
Those forks have a fluid damper that acts exactly the same anywhere in the stroke, therefore damping is linear.
However, because it is not a coil spring fork but an air spring, the spring itself is not linear and becomes harder (the spring rate decreases) as the fork is compressed. Soft at first, then harder and harder as it is compressed.
I suspect that you suspect the damping is not linear. This will confuse you in getting to the right setting. It is perfectly linear.
The rebound setting doesn't seem to be linear, no issue with the damping.
 
OP
C

Crackle

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Rebound is damping. You get two types of damping. Compression Damping and Rebound damping. The way the mechanism works is linear.
Like I said, it didn't seem to respond in a linear way when I was adjusting it. 2 or 3 clicks into the top third of adjustment seemed to make more of a difference than in the middle. I went up and down a few times to be sure but I'm just adjusting this on feel, I could be wrong. I also read online that the lockout was not effective until the forks had been ridden a few times. I found this to be the case myself. I was on the verge of taking it back when it began working properly, so perhaps there's an element of bedding in going on.
 
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