Fork air gap

[arcticflipper]

Can anyone please tell me what the result will be if you change the airgap from 142mm to 150mm

The Wilbers setup requires a 150mm air gap, which I did.

Now if I were to make the airgap 142mm what would the result be?

The reason for asking is that I've noticed that the front wheel now starts loosing grip quicker in corners than when I still had the OEM springs and setup.

Not too sure but it might have something to do with the fact that we've had rain for the last week, and today was the first dry day. There might still be a lot of shit on the road i.e sand, oil etc.

Thanks

[pug]

Here in Athens after heavy rain the roads are better because they get washed of dust e.t.c. (assuming that there are no strong winds after the rain).

I think you used very light fork oil (2.5wt - am I right) and you don't have sufficient rebound damping.

Personally last time I used WP 7.5 wt @ 140 mm (down from Silkolene 10 w)and although its more comfy over bumps sometimes its twitchy when I am off the throttle from high rpm with low gear.

Anyway these are very subjective findings.

Just remember that when you fill the forks with oil you have to bleed the cartridge (by moving it up and down) until you do not have any gap at all in compression & rebound. Then you adjust oil height.

[arcticflipper]

Thanks, I used 5W oil, did the bleeding etc, now just wondering what the 150mm airgap does.

Why Wilbers were so specific on it must be 150mm airgap...

[shovelstrokeed]

The air gap acts as a supplemental spring. The larger the gap, the softer the spring rate. Decreasing the gap from 150 to 142 mm should slightly harshen the compression reaction of the fork just as if you had installed higher rate srpings.

[arcticflipper]

Will this then when lets say OEM springs with 150mm air gap then be more spongy against a more stiffer ride @ 142mm air gap?

[bartonmd]

Yes, you are correct, but only partly... Taking more air (the only thing that is able to compress in the "system") out of the forks by raising the air gap just basically makes the springs "more progressive." This is why you don't really need progressive springs in the front end of most bikes (and also why they told you to lower the air gap I'd guess). Since there is less air to compress, the more distance you compress the air, the quicker it becomes at a higher pressure, pushing back in the same direction the spring does, and acting like another spring.

Another way to think of it is: If you fill the forks all the way up with oil, they won't be able to compress at all because of the lack of anything in the system that will compress, whereas, they can compress when there is an air gap.

Any help?

Mike

[pug]

The air gap acts as a supplemental spring. The larger the gap, the softer the spring rate. Decreasing the gap from 150 to 142 mm should slightly harshen the compression reaction of the fork just as if you had installed higher rate srpings.

+1

Will this then when lets say OEM springs with 150mm air gap then be more spongy against a more stiffer ride @ 142mm air gap?

Bigger air gap=softer

smaller=harder

Change oil weight, adjust air gap @ +- 140 mm.

Also less air gap gives more bottoming resistance (which I experienced alot with OEM springs). Never go beyond manufacturer's specs while decreasing air gap 'cause hydraulic lock waits at the corner.

Did you check fork oil specs I gave you last year (Dec 23rd )

http://www.cbr1100xxforums.org/forum/viewt...er=asc&start=40

If you have trouble reading the tech terms I might be able (or others in this forum) to help.

[arcticflipper]

Just to verify that I'm understanding this correctly - Raising the air gap is if it was 142mm, you take the air gap down to 130mm for example - compressing the air in the gap at a higher level = harder ride, and lowering the air gap is taking it from 142mm to 150mm more air to compress = softer ride.

[bartonmd]

Mostly correct... It will feel about the same toward the long end of suspension travel, but the spring force (not the damping, or "harshness") goes way up as the forks compress.

mike

[arcticflipper]

pug, I will have to find out how the Putoline fork oil's compare in these charts, not too sure what I'm reading, but as soon as I get the comparison info I will come back for more info there.

Thanks to all for the info so far.

edit: Question on the oil weight:

Will a heavier weight fork oil 7.5 or 10w then mean that I need to take the air gap down from 150mm to 142mm or 143mm to achieve the same type of ride?

Will this not influence the static and loaded sag?

The experts from Putoline suggested that I look at a 7.5 or 10W oil instead of the 5W. Reason they gave me was that the XX is a heavy bike, and the 5W oil might not be heavy enough thus the front wheel loosing grip quicker now - does this sound right?

[bartonmd]

The XX is a heavy bike, but comes with, I believe, 7.5 weight from the factory and is WAY over-damped... I am running 5W and it's just perfect for me... althought I haven't tried the 2.5W...

You see, yes, the XX is heavy, but how the suspension reacts has a LOT more do to with the valving in the forks than the weight of the bike... You can have a 300lb bike with HUGE valving, and a 600lb bike with very small valving, and run the same weight oil in both of them and the 300lb bike will have softer damping...

The oil weight will not influence the sag, but different air gap will... When you take down the air gap, you're basically making the "effective spring" stronger, so it will ride a bit higher, depending on what your sag is.

Mike

[Redbird]

...comes with, I believe, 7.5 weight from the factory and is WAY over-damped..

Stock fluid is Honda SS-8, which is 10w. Why Honda can't label the shit more clearly I don't know.

Agree on the over-damping.

[arcticflipper]

Thanks, this just shows me again how little South Africa knows about bikes and stuff.

I can't get a straight answer here about what I'm asking.

Would the front wheel slipping feeling be caused by too light fork oil?

I know there are various factors involved, i.e tire tread, rider positioning etc, but if the bike is running too light fork oil will this cause the forks to respond too quickly, thus the front wheel looses tracktion in corners quicker?

[Pete in PA]

This is some good stuff to know since I'll soon be doing My Hyperpro swap front and rear.

With my factory setup right now (with just the spring preload increased front and rear) if anything when the front hits a bump when leaned over it causes the tire to skip off the pavement and loose traction.

With a softer set up I'd think it would track the bumps better and maintain traction so I'm not sure what's going on with your setup.

Since you made changes to the front without changing the rear maybe there's less weight on the front now.

I'd check/set your rear spring preload.

BTW: Hyperpro's directions want the 7.5 wt. oil set at 140 mm. Fatory setting is 154 mm with 10 wt.

[arcticflipper]

I've spoken to a Putoline fork expert, and according to them they felt that the fork oil suggested (2.5W) and the one I used (5W) was too light for the conditions in South Africa.

They suggested that I sould not go under 7.5W, so I've changed the oil out again today, Getting pretty good with this now... lol

I've now used the same SS-8 wieght oil - 10W - Putoline.

The one thing I must say was that I was shocked at how fast the oil changes color. Only after 1 week, and the oil was allready starting to go black/brownish.

I mentioned this to the Putoline people, and they replied that the Putoline oil actuall helps to clean out any olde oil and deposits that might still be in the forks That was the reason for the color change. Their engine oil does the same thing.

I can't really comment on this, as I don't know. I will have to drain the oil again to verify this, after another week or so.

I've used the OEM airgap for this setup, to check if the handeling will be the same or better.

Have not yet been able to ride the bike to test it, but will go for a B/F run on Sunday morning.

Will keep you posted.

Oh, rechecked the static and loaded sag just to be 100% sure that averything is right.

The Putoline fork oil that I've used is a HPX10, this is displayed on the bottle, the previous one was HPX5

[blackhawkxx]

so I've changed the oil out again today, Getting pretty good with this now... lol  

Are you pulling the forks each time or are you draining from the bottom?

[bartonmd]

:roll: I still say that, if they are reccomending the factory weight, they don't know the XX very well... Your weather isn't that far off of ours is it?? If you were around the equator, I could see wanting a thicker oil for the hot weather, but you actually kind-of have a winter right??

Either way, I'm very happy with the 5W in the summer heat too (95 degrees F)...

mike

[firedlt]

This is an interesting topic, since I am about to change my springs and rear shock setup to the Wilbers. I have debated on the 2.5W or 5W. Wilbers recommends the 2.5W W 150 air gap. I weigh 175 around 185 with gear. I was think of the 5W and after reading the responses here probably will start with that. Interested in Flipper lean angle and road conditions why the front washes out. Also the relationship of rear setup Vs the front and did he raise the forks in the triple clamp to bring the front lower Vs the rear.?

[rodantking]

I have springs and oil in the mail. I am hoping to have it together for next weekend. I have never touch forks. Always got a dealer to do it. Time to get over the fear.

Anyone got a link on a how to.

Also on the air gap, it seams to me that if I use the same amount that comes out the air gap will stay stock. Is this true or do I need to buy a the tool to measure it with?

[arcticflipper]

Findings on the 10W fork oil:

I pull the forks every time I replace the oil, do not drain it from the bottom.

When I lowerd the front, I pushed the forks up in the tripple clamp. From 39mm to 46.5mm. This I did not like, the handeling was really bad. It could be that I lowered the bike too much in the front, thus changing the rake and also shifting the weight of the bike too much to the front.

What I found with this setup was that there was a much quicker turn response from the bike, but the overall ride was shit for me. The tail was way too light, and would spin or slide for nothing.

I've tried the 5W oil, and found that the front starts sliding way too quickly in corners, either I am leaning the bike too much, or the tires are just shit or the dampning isn't suitable.

Thus I've changed the fork oil out to 10W Putoline HPX10 fork oil with 142mm air gap and the Wilbers springs 0.90 Nm spring and OEM 39mm fork spacing.

It is still sumer here by us, but also remember South Africa does not have the best of roads or road conditions around.

I immediately could feel a big difference in the handeling. The bike was much more stable in the corners, and I could actually puch the bike through the corners at higher speeds than before.

I will also say that I think the 7.5 W oil would not have been bad either.

PLEASE REMEMBER THAT I DID NOT DO ANY VALVING ON THE FORKS.

I ALSO STILL HAVE THE OEM REAR SHOCK.

I also found that the front is now a lot stiffer, and I don't think the 150mm air gap would have been bad either. This might make the ride a little softer, but I don't know if it would have been the best option for our road conditions here.

I will try the 7.5W oil at a later stage to get a comparison against the 10W with 150mm air gap.

Basically for me the 10W oil worked much better than the 5W, the bike feels solid going into turns, and during the turn. No more front stepping out, hesitation fron the bike etc.

I've also found that with the 10W oil the bike feels so much more smoother over bumps and stuff.

I have not placed a 6mm shim on the rear shock.

I hope this helps anyone.

I still have the K-tech linear springs 0.90Nm that I will do valving with on the forks, to get a comparison with these. I will send them in to be done, as I don't have a clue on how to do the valving.

To do the forks isn't that bad, it is just very time consuming due to the oil draining from the forks. This took me the longest, trying to get as much old oil out as possible.

I will try to upload as much info with pictures on how to remove the forks as soon as I can.

There is one warning you need to take note of. CHECK THE PATH OF ALL WIRING AND CABLES BEFORE YOU REMOVE THE FORKS!

This seems to work for me, and might not give another person the same experience. I only weigh in at 70 KG's, and we do not have great roads or road surfaces in South Africa.

The 5W oil is very responsive, and much quicker than the 10W, but too quick for our road conditions in my opinion. Even they racer boys here in SA uses 5W with valving done for their race setup's. Please bear this in mind.

[Warchild]

I have springs and oil in the mail. I am hoping to have it together for next weekend. I have never touch forks. Always got a dealer to do it. Time to get over the fear.

Anyone got a link on a how to.

Installing the Wilbers Fork springs

[bartonmd]

Flipper,

Use whatever you want, but 10W is what it comes from the factory with, and it was OK for REEEALLY smooth roads and such, but when the roads got bumpy, the 10W oil would rattle my teeth out, and the front tire would skip and stuff over bumps because of too much damping... After switching to 5W, I could probably go to 2.5W and be better on the bumpy roads, but the 5W oil is SOOO much better than the 10W for bumpy/choppy roads because the front forks actually move up and down when they hit a bump, as opposed to transfering 90% of the energy up into the sprung part of the bike...

Just my, and several others' experiences...

Mike

[arcticflipper]

I'm not disagreeing with this, I'm only posting what I found worked better for me. I would still like to try the 7.5W oil with a 150mm air gap. The 5W was little bit too light for me. As I mentioned, I found that it did not give enough dampning for me in corners, front wheel sliding out.

What I write here is my opinion and feelings with regards to what I found when I tested the different oils. This does not mean that it is carved in stone, or that it will be the same for someone else.

This is solely my opinion and ride experiences with the various oil weights etc.

I didn't like the feel the 5W gave me, and preffered the 10W up to now from what I've tested and used so far. I still would like to change to 7.5W with 150mm air gap, but before I do that, I would like to test the 10W with 150mm air gap. At current I have 142mm air gap.

I can say that the suspension is a lot stiffer, harder than what it was with the 5W, but I preffer a stiffer/harder suspension. I think the 7.5W will be a really good compromise on the suspension, but I still need to test it first.

Like I said before. This is solely my opinion with regards to the ride experience I had with the 5W and 10W fork oils. I also do not know if this has anything to do with it, but I ride a European 2002 XX, not a US one, thus all my experience is based on that bike.

[bartonmd]

Flipper,

Use whatever you want,

Mike

[shovelstrokeed]

Flipper,

A suggestion, your weight at 70kg is on the light side for a 0.9 spring and this may be where you are running into a problem. I use a 1.0 spring and I weigh 110 kg.

With a too heavy spring, the suspension will feel too stiff and under damped with the lighter oil. I would suggest a .85 or even a .8 spring with the 142 mm air gap and 5w oil. I think you will be more pleased with the result.

You state that the roads there are a bit rough and it is more compliance you seek rather than less to help cope with this.

Get the spring rate right, set the sag and then work on fine tuning the damping with fork oil. I think you'll find a much better ride and traction as a result.