Hawk Front forks

[Vtunimog]

My front forks are too soft. I bottom out very easily and often on braking my front fender will rub on the tire as the forks are compressing too much. I drained the oil (the bike has less than 4 miles on it) in both forks, refilled with Lucal fork oil. Made sure the spacers were in place (looks to be cut pieces of thin-wall tubing) after sealing both forks I flexed the forks up and down to work oil thoughout the valves. Still about the same, I am not a terribly heavy rider (180 lbs or so)

Any ideas ?

[BlinGCS]

what weight fork oil did you use? try using a heavier oil.

[pete]

Put longer spacers in or replace the springs
or could try a bit more oil to reduce the air space..
At 180lbs " 81kgs" you should not be to heavy
for the standard suspension...

if you want to get carryed away... the very top holes
in the damping rods control the compression damping
they can be welded up and redrilled smaller to increass
the compression damping... slow the fork compression travel down
a thick oil will do the same but it also slows the rebound damping down..
welding the holes slows one action down with out effecting the other...



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[Megadan]

I am 260lbs of gigantic human and I have yet to bottom out my forks riding this bike on the inteded type of riding it was meant for.

So first question, as BlinGCS asked, what weight of fork oil did you use?
How much oil did you put in each fork? Each fork should have at least 210ml, or a 160-155mm compressed air gap as a baseline.

Second question. How much rider sag do you get on the front forks with your weight fully on the bike? This would be the amount the suspension compresses by just sitting on the bike. The Hawk has 8 inches of front suspension travel, so if we follow the basic 1 in 3 rule, the static rider sag on the front suspension should be around 2.5 to 3 inches from fully extended.

I bring this up because my Hawk's front suspension would sag over an inch under its own weight when held upright with the stock 15mm preload spacers in place. Add my weight to the bike and it would compress another 3+ , leaving me with less than half of the suspensions travel for compression, making it very likely that my forks would bottom out. I made my own preload spacers out of bronze pipe/tubing ( you can use aluminum, PVC, steel etc) that is 22mm or 7/8" diameter that are 35mm in length. This length of preload spacer stopped a majority of the static sag under the bikes weight as well as compressed more of the primary spring rate of the Hawks dual rate springs, bringing me closer to the heavier secondary rate during suspension travel. I have contemplated making 40mm spacers, but seeing as my bike is not used in rougher off-road scenarios, it has proved ample for my weight.

My current setup is 230ml of 15wt fork oil in each fork, leaving me a 105mm compressed air gap. This reduction of air gap creates a higher compression pneumatic spring rate as the forks compress. The risk of this is going with too little air gap can run the risk of blowing out the fork seals in a worst case scenario, and making for a harsh ride in the best case. To date I know of a couple bikes running 240ml of oil in their forks without any reported seal failures, but I don't know how heavily their bikes are used.

Unfortunately there are no fork spring alternatives for tuning them to rider weight, but tuning the preload on your bike to get an ideal rider sag will ensure you optimize the compression travel of the suspension. If you can get the help of a buddy, measure the forks from a fixed point like the bottom of the lower triple tree to the bottom of the fork with the forks fully extended. Then sit on the bike with all of your weight on it, and have them measure from the same points and figure the difference. If it is more than 3 inches shorter then you should consider making longer preload spacers. PVC tubing makes a great cheap and easy way to find the right size spacer, and if you feel like using metal you can translate that length to some tubing and make metal units.

[Megadan]

It should be noted that, no matter what you do, these forks aren't really ideal for heavy off road duty. If you are bottoming out because you are making the bike leave the ground, then they won't cope well with that abuse for long, and will likely keep bottoming out. This bike was really only intended for rough unpaved roads in lesser developed countries, and not for hardcore off-road adventures.

[Ariel Red Hunter]

Originally Posted by Vtunimog

My front forks are too soft. I bottom out very easily and often on braking my front fender will rub on the tire as the forks are compressing too much. I drained the oil (the bike has less than 4 miles on it) in both forks, refilled with Lucal fork oil. Made sure the spacers were in place (looks to be cut pieces of thin-wall tubing) after sealing both forks I flexed the forks up and down to work oil thoughout the valves. Still about the same, I am not a terribly heavy rider (180 lbs or so)

Any ideas ?

First thing is the wheel should not be touching the front fender even under full compression. So something was assembled wrong when mounting the front fender. Cheapest solution is go to CSC web site and get some new springs. Chinese quality control is a little behind the curve. 180 lbs. rider should not require longer spacers. One way to check the sack of the front forks is to use a piece of string, tied to the brake rotor, at the top, and mark the distance to the handlebars on the string with the bike on the center stand (full sag). Then, after making sure that the string is in the same position on the rotor, sit on the bike, pull up the string, and mark it again. The distance between them should be 3 inches, or a little less. If it is much over 3 inches, the springs are too soft. But you will get nowhere until that front fender issue is rectified...ARH

[timcosby]

are you sure you slid the all the way down in the trees when it was new? they come shipped with the forks 10 inches up in the trees.

[pete]

3" / 75mm rider sag is very soft for 8" / 200mm total travel forks
even in full offroad tune...
you should be looking for around the 2" / 50mm static sag
will give ok offroad complyance but not that soft that the
bike will wollow around while cornering on the road...

if you want full offroad tune you should be looking around 2.5" / 62mm
or just over....

Dirt...
1.25" / 30mm static sag = bike under it's own weight..( NO rider)
30% / 2.5" rider sag = with rider...

dirt/road..
1.25" / 30mm static sag...
35% / 2" rider sag...



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[Megadan]

Originally Posted by pete

3" / 75mm rider sag is very soft for 8" / 200mm total travel forks
even in full offroad tune...
you should be looking for around the 2" / 50mm static sag
will give ok offroad complyance but not that soft that the
bike will wollow around while cornering on the road...

if you want full offroad tune you should be looking around 2.5" / 62mm
or just over....

Dirt...
1.25" / 30mm static sag = bike under it's own weight..( NO rider)
30% / 2.5" rider sag = with rider...

dirt/road..
1.25" / 30mm static sag...
35% / 2" rider sag...



..

I agree with these numbers, but in order for me to achieve both the static and rider sag figures I would need heavier rate springs, so I compromised and aimed for a decent rider sag. I agree, the suspension is still a bit soft, but it's much better than stock.

[timcosby]

im still betting the forks are in the shipping location thats the only way to hit the front fender

[Ariel Red Hunter]

Originally Posted by timcosby

im still betting the forks are in the shipping location thats the only way to hit the front fender

Well I hope you are wrong, because if he is riding it that way, he's going to get thrown off into the pucker-brush sooner or later. If those forks are still in the shipping position, the rake and trail is so extreme the bike will be real twitchy....ARH