Suspension dive under braking

What does the all knowing hove mind have to say on this then? My Revelation U-Turns on 120mm setting tend to go over half way through their travel on slowly slowly, ride the brakes, nearly going over the bar type decents. Other than that, the sag is set right, rebound seems good but I’ve not yet sorted the poploc for the compession dampening although I’m thinking that I wouldn’t have it turned on on the descents I’m talking about. Is it normal to use this much travel without hitting a bump?

air or coil?

This i an area I can predict a row 🙂

The poplock will prevent this happening but at the expense of bump absorption Basically it locks the fork out. braking always gives some dive. IMO live with it or increase the spring rate ( add air / harder spring).

People will tell you to use the poplock for this I bet.

Really steep stuff will transfer the majority of you weight onto the front end so further sag is to be expected.
If your happy with this and they function well in all other areas is there a problem?
A little bit of low speed will reduce dive on the brakes and through ‘rolling’ compressions/g outs.

transapp – Member
Is it normal to use this much travel without hitting a bump?

it’s not unusual.

hang on, there’s a gag here somewhere…

but seriously, it doesn’t sound that weird; the world-cup-Dh guys and girls sometimes run stiffer springs/more air to keep the front end up a bit on the steeper tracks like champery.

Hard braking puts a lot of force on the forks… Could be a wee bit of riding position too though, if you’re loading the front end up excessively.

You can use the poplock purely as a damping control rather than as a climbing aid, can be quite effective if you’re out on a ride and realise you’ve botched the positive pressure.

Sounds like the suspension is functioning correctly to me..

I don’t have a poploc on mine,but use about 1/3 on compression damping to reduce this problem.

Floodgate…?
I wouldn’t change the air/spring rate if sag is correct.
I would play around with floodgate-its an override function of the poplock – with pop lock on you can set the floodgate so it still compresses on big hits, but has more compression damping for climbs and descents like yours.

DrP

I kidded myself that I could get away with a standard spring in my Lyriks, far better now that I’ve changed to a firm spring, cheap, quick and really simple to do.

Don’t think I’ve lost any sensitivity to small bumps, just rides slightly higher and gives a bit more support, also feels a lot more reactive down rocky trails.(doesn’t pack down}

In air forks, I feel that I lose small bump sensitivity if I firm them up to take my weight.(don’t know about the latest air forks)

On that kind o descent i just get back off the saddle

Never tried ot myself bet there is loads on the net on this. This from a blog on te genesis alpitude

At first on slower, steeper, tighter trails the slightly divey fork could make things feel a bit on the steep side (I think the relatively low 12.2in BB height helped to keep the endos at bay). But after some helpful setup advice from James at Genesis Bikes the forks have been LOADS better. From his pointers I now run the forks quite hard (and with not so much pressure in the negative chamber) and with a smidgeon more rebound that I would typically. I have wound the Motion Control’s Lockout “blow-off” threshold almost all the way off and now when riding steeper, steppy stuff I flick the fork to Lockout position and the forks still compress but with a significantly stiffer action. No hyperactivity or diveyness. I instantly felt so much more confident and at ease with the bike on Stupid Stuff with the fork setup this way.”

1) That kind of descent, why are you riding the forks at 120mm? Wind ’em out to 150, and it’ll alter the balance of the bike so you’re not putting so much weight on the front. The extra travel means you won’t need to be quite so “slowly slowly” either! 😉

2)I have U-turn Revs too and find that I run them with quite a lot of floodgate and then turn the MoCo knob on one or two clicks from fully unlocked. Just gives that bit more low speed compression – otherwise they’re a bit overactive for my tastes.

TandemJeremy – Member

air or coil?

This i an area I can predict a row

The poplock will prevent this happening but at the expense of bump absorption Basically it locks the fork out. braking always gives some dive. IMO live with it or increase the spring rate ( add air / harder spring).

People will tell you to use the poplock for this I bet.

It doesn’t lock it out at all! I hope I meet you one day to demonstrate this and put it to bed! 😀

The other possible solution is preload on a coil fork (though not possible with u-turn coils unfortunately, or reducing the negative air pressure – not sure if this is possible on air u-turns or just dual airs). These increase the rate at the start of the stroke.

rretro – all the poplock does is put on massive amounts of compression damping (IE lockes the foirk out) with an adjustable blow off valve. I have several forks with it. I never use it. its very crude

The poplock will prevent this happening but at the expense of bump absorption

all the poplock does is put on massive amounts of compression damping (IE lockes the foirk out)

Right. Worms, can, open. Not on the 2011 models it seems, but full credit to Rockshox for selling £600+ forks with a user manual that has literally no set up information, or even tell you what the various adjustment bits are for. You get better instructions on a £30 clock radio.

I have the same issue blowing through the travel at 150mm. This is with the air spring at 140psi, compared to 120psi on my Pikes. 140mm represents about 20% sag for me, but they are difficult to set up as there seems to be a lot of stiction being new. So, comments:

On my dual position Revs there is no -ve air chamber. The +ve seems to need a lot more air than the Pikes, so I assume the volume is much greater, or has +ve and -ve set from the top cap. If the chamber is bigger this could mean needing to go to a much higher pressure as it won’t ramp up the same when compressing?

The gate on the right leg does NOT lock the fork. Having played around with the compression knob (which does not seem to make a lot of difference) and the gate it appears that the gate controls the point at which the compression setting is bypassed.

Compression on lock, gate on min – no lockout
Compression on min, gate on max – no lockout
Compression on lock, gate on max – lockout

Sooo, I think the correct set up technique is as follows:
1) Ignore static sag set up. Set compression and gate to min, then play around with air pressure so that you just get max travel on very steep slow speed hits.
2) Set compression to where you want it to prevent blow through on high speed hits
3) Set gate either to full, or roughly to correspond with the number of click of compression

Comments?

Everything in biking is a compromise, so if you try and dial out brake dive with compression damping or more pressure the fork won’t work as well elsewhere.

I tend to compensate for brake dive with weight shift and have the fork setup with the correct sag and very little damping. Might get dive on the steep bits, but it works a lot better on fast rocky stuff.

Apples and chairs. and roundabouts.

Weight back more, more low speed compression damping to deal with rider input. Poss slightly faster rebound to prevent fork packing down under repeated impacts while weighted.

1) That kind of descent, why are you riding the forks at 120mm? Wind ’em out to 150, and it’ll alter the balance of the bike so you’re not putting so much weight on the front. The extra travel means you won’t need to be quite so “slowly slowly” either!

eh? you don’t need more travel to ride steeper descents and it’ll only really help when riding rougher faster ones.

I wouldn’t change the air/spring rate if sag is correct.

I would! The dual air setting guidelines printed on my (100mm) rebas are way under sprung for my weight and the way I ride. They dive like **** if set to the suggested settings so I run somewhere around 20psi more in each chamber (this obviously also results in less static sag), But being an air spring I find they need to be set-up to sit higher in their travel than coil to remain high in the midstroke during use. because of this (and the more progressive nature of the air spring deep into the travel) I find to get the same firm feel as an X-firm coil they simply can’t be set-up to bottom as easily as the coil spring would. Bottoming out isn’t everything and 90/95mm travel is enough for anything for me.

I put heavier oil in my Revs so I could keep the compression open and didnt really use the floodgate. Stops brake dive and using all the travel on little drop. Slows rebound down aswell, which isnt a bad thing IME.

Sounds like he’s got them set so they give “full travel once a ride” to me…..

😉

you’re overthinking it!

Right, I’ve got some Revs from some year or other, and they have a lever on them, but I don’t know exactly what combination of poploc/blowoff/mission control/super duper whatever it is.

There is a knob on the bar-mounted lever that controls how locked out the fork is when you lock it out, by varying the compression damping. There’s a knob on the fork that controls how hard you have to hit it before it’ll loosen up.

So by setting those two, when I flick the switch it gets very stiff but will still move a bit when I hit something big. I use it either for road riding or for very steep arse over the back stuff, because it stops the fork diving but still gives a little cushioning. It’s quite clever actually 🙂

eh? you don’t need more travel to ride steeper descents and it’ll only really help when riding rougher faster ones

No but the extra length gained by winding out will help significantly…

no it won’t, you’re clearly just a bit shit at riding steep stuff

TandemJeremy – Member

rretro – all the poplock does is put on massive amounts of compression damping (IE lockes the foirk out) with an adjustable blow off valve. I have several forks with it. I never use it. its very crude

I don’t think it’s crude, it allows for a reasonable amount of tuning although simple in implementation.

As I think molgrips refers to above, there is a version of the poploc with a blue dial which adjusts how much compression damping is set without affecting the locked position. Essentially giving you the same amount of control as with the fork-top controls but a bit more convenience.

no it won’t, you’re clearly just a bit shit at riding steep stuff

Have you seen him ride steep descents then? Seems a bit harsh of a comment to make based on literary evidence alone.

Winding out the travel will help with riding steep descents. The axle to crown length will increase with the increased travel and put the riders weight further back and also slacken the head angle.

…and raise the BB which we all know always makes a bike more stable and nicer to ride 🙄

less weight over the front wheel is not always a good thing even on very steep terrain

My Revs feel too soft also. Generally run them at 120-130 on the HT (which translates to about 110 when i’m on the bike), only dropping them to get the bike in the car or if I spy some jumps while out and about.

In an ideal world i’d get a firmer spring in there, but I can’t be arsed. My cheap work-around for brake dive is to use more back brake and less front.

I am talking about very steep stuff – as steep as you can ride. So arse over the back of the saddle, slower than walking pace, that kind of thing.

Higher BB impedes manoeuvrability at speed, but it’s not significant in this scenario. You go over the bars when your centre of gravity is further forward than your front wheel. Winding the forks out helps to prevent this IME, as does reducing dive.

molgrips – Member

I am talking shite againFTFY 😉

Dunno about you but as steep as I can ride can’t be ridden slower than walking pace for more than about a bike length or so.

You go over the bars when your centre of gravity is further forward than your front wheel. Winding the forks out helps to prevent this IME, as does reducing dive.

Actually when your CofG is further forward than the bike’s CofG I think. But going over the bars can also be caused by a sudden stop that halts the bike but not you – the slower you’re going the more likely this becomes.

BUT, back to the OP, what is the correct set up for new Revs to stop them diving, as 20% static sag and compression set half way still blows through the travel too easily

Buy some RS Boxxers..

fit to bike..

WINNER!

Dunno about you but as steep as I can ride can’t be ridden slower than walking pace for more than about a bike length or so

Depends on the trail innit.

Smooth chute – yeah.

Very tight and rocky – no.

Captain – depends on the bike really. Some bikes put your weight such that you don’t weight the forks much and don’t get much sag, until you hit something steep and then blam. I’ve had the same fork on different bikes feel completely different.

Just experiment. You haven’t got that many choices on Revs have you? Try more air and more negative air (you do have negative air on those don’t you?)

So 120-150mm travel at front therefore a total of 30mm increase in A2C height, so maybe 15mm at the BB. Ok half an inch ish is quite a lot of an increase in BB height depending on the OPs frames geometry and BB height however personally, dependant on the frame geometry (and what travel fork the frame is adjusted for) I would trade a slacker HA and longer travel over a slightly high BB for riding the steep and deep.

If the fork is sitting in to the travel that far anyway then I doubt the extra 30mm of A2C is going to raise the BB much beyond what it would be static.

To be honest its hard to find one fork setup that will suit all riding conditions, to a certain extent you need to be tuning your suspension to each track you’re riding. If you’re riding tracks where that are a lot of steep descents then you might have to add a little more air to to prevent dive at the expense of small bumps sensitivity on the rest of the trail.

Try more air and more negative air (you do have negative air on those don’t you?)

Nope, not on the dual position air. That’s why I struggling to get the right setup as I had it all sorted on my Pikes

I would trade a slacker HA and longer travel over a slightly high BB for riding the steep and deep.

Completely agree, which is why you don’t want the fork diving too much when it’s just steep – need to keep travel available for hitting stuff

Blimey, didn’t think I’d get that sort of response!

They are 2008 Revs, 100-130mm adjust dual air. My weight’s in the right place (I have a small idea about how to get a bike down a hill)
If I wind it out to full travel, I’ll lose time when I’m past the relativly short steep section as I’ll want to wind them back in again. Plus, sometimes you don’t know the trail so you can’t set up ready for a specific section so looking for a best compromise setup.
It appears that the result is ‘deal with it’ and ‘whats the problem’ surrounded by some willy waving and you know nothing posts.
Typical STW then!
Oh, and TandomJ, not often I think this but you were right!

transapp – its one of the subjects guaranteed to get a row going!

If its only occasional then maybe do use the poplock and accept rubbish compliance in that situation. Or accept the dive and enjoy a supple fork

Suspension set up is always a compromise. Personally I like a really supple active fork so put up with excessive dive occasionally

from here

http://forums.mtbr.com/showthread.php?p=1498056&highlight=Floodgate+-+please+explain…%21#post1498056

I am seeing some posts claiming that the floodgate can be set up to resist bottoming. Perhaps I am misunderstanding them, but the floodgate does NOT help resist bottoming. All the floodgate can do is BYPASS (turn off) the compression circut. Whatever you have the compression dial set to is the maximum compression dampening you are going to get. Setting the floodgate fully firm simply means it is NOT going to bypass the compression damper. and what you have left is a simple “unshimmed” damper with no high speed blow off. It is not progressive in the sense of being possition sensitive (it does not ramp up at the end of the stroke) but it does “spike” at higher shaft speeds, thus feeling harsh. I guess you could call that “bottoming resistance”, but that is not what the term generally refers to.

The floodgate opens up when a certain amount of pressure builds up at the compression damper. The floodgate adjustment adjusts how much pressure (or resistance) is required to do so. A firm (clockwise) setting means that it requires a lot of pressure to open the floodgate. Two things increase the pressure at the damper: The size of the damper hole (which is what the compression adjustment changes) and the speed of the fluid pushing through it. Smaller hole (which is a high, clockwise compression dampening setting) and faster moving fluid (faster moving shaft) means more pressure. So here is how this can play out in 4 different scenarios:

1) With the compression all the way open (lowest or counterclockwise setting) the floodgate setting makes little difference because the fluid (and therefore the fork shaft) have to move incredibly fast to build up enough pressure to open the floodgate. The floodgate must be set to full soft (counter clockwise, lowering the pressure needed to override the compression damper) in order to have any effect. So what you have is very little compression dampening until you have a big, fast hit, and then you have even less. Personally, I don’t see why anyone would want this (compression and floodgate both at min). You’d may as well just loose the compression damper and the floodgate altogether, and save some weight and money. Plus, as I will explain below, the lockout feature is also now totally useless.

2) With a more moderate compression setting, with the Floodgate set to open at higher fork (an fluid) speed you have something like Marzocchi’s HSCV that overrides the damper just as it reaches the fluid speed that causes spiking. I used this setting for a while and it felt a lot like my `03 Z1 FR.

3) With a high compression setting (small damper hole), pressure builds up very easily at lower fluid speeds. The floodgate is set up to open at pretty low fuid speeds. This gives you a fork that resists bobbing and diving fairly well, but opens seamlessly up for any bumps. This is my favorite setup.

4) When you “lock out” the fork you are essentially closing the compression damper, so no fluid gets through. Any force the shock experiences will translate to pressure at the compression damper. This is where the setting of the floodgate is most noticable. Full firm setting means the shock is going to be very difficult to move. It is truely locked out. As you lighten it up though, the compression damper is easier to override and the fork can be set to feel locked out, but it will react to larger hits. As you get to the really light settings, the fork has more of a “platform” feel to it. However, I don’t think it is accurate to say it’s like most platform shocks. Once the floodgate is open you have no control over the compression dampening characteristics. Most platform shocks that I am familiar with have some well though out compression dampening circuts that are in effect even after the platform is breached. For example, Manitou SPV shocks have a compression circut that ramps up at the end of the stroke to resist bottoming, and often you can adjust how much it ramps up.

The trick thing about the floodgate setting is that it has a different result when your fork is locked and unlocked. The compression/floodgate setting that works well in the unlocked position (scenarios #1, 2, 3) may not have the floodgate setting you want when you lock the fork (scenario #4, if you ever do that). For example, for my unlocked setting I run high compression with a very light floodgate setting (scenario 3). I think this is the best feel for me. However, this means that when I use the lockout, the floodgate opens up more easily than I would like. It’s not a lockout at all. However, I do notice a little more resistance to movement, and it can be a useful feature when going down something REALLY steep, and it helps me launch drops and jumps more easily. I use it less and less, however, and I am considering trying to ditch the poplock altogether. For people using #1 and #2, however, the locked out setting (#4) will perform much more like a lockout.

The RS forks I have with poplock don’t work anything like that.

TandemJeremy – Member

The RS forks I have with poplock don’t work anything like that.

My last 5 pairs have done 😉 As I mentioned though, you need to set the blue dial to an intermediate position rather that fully locked as with the el-cheapo standard poploc.

Setup 2 or 3 on Kapusta’s post linked from MTBR is very supple, but still resists diving.