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Front knock over bumps, anyone figure out what causes it??

9K views 28 replies 19 participants last post by  Italian 
#1 ·
I know it's been discussed before. I get the knock over railway tracks but it's annoying. When I ride a gravel road and hit washboard it's very annoying. Sounds like it's from the forks. I installed sonic springs and heavier fork oil and it makes no difference. Has anyone ever solved this? By solved I mean "I did this and the knock is gone".
 
#2 ·
I have always noticed that the knock gets worse the colder it gets. In the hot summertime I don't hear it hardly at all, but I do in the spring or fall. It's possible that you need a lighter fork fluid? I say that because when it's cold, the oil is thicker and the noise is worse.


I am going to adjust the tension on the steering head bearings and see what happens. I'll report back afterwards.
 
#3 ·
Unfortunatly, all the Wee's do it, and nobody has come up with the reason and/or cure. I just got used to it.

It did disapate considerably with SonicSprings.

Cheers
 
#4 ·
Mine seems to have stayed about the same with the Sonics, it drives me nuts sometimes. It just feels/sounds like something is going to snap in the front end. I have come to live with and accept it but it still bothers me every now and then (especially on a washboard gravel road).
 
#5 ·
With the stock damining settings, I would heir the forks bottoming occasionally when hitting bumps a little to hard for the suspension. I adjusted the fork dampers to position 1 + one turn, and haven't really herd the forks bottom. The bike seems to handle better as well with these setting. After I get some other farkels, I will go to a stiffer sping to see how that effects things as well. What Sonic springs do you have? I know that they make after market damping valves, that are supposed to improve things in addition to the super brace.
 
#6 ·
You are changing the spring preload setting, not the damping which is not adjustable. That can help prevent bottoming as it takes a longer stroke to bottom the forks.
 
#7 ·
Thanks for the clarification! Originally, I thought the adjustment was for preload, but was reading a thread somewhere and they were stating that the adjustment was for damping and not preload :). Of course a quick look at the owners manual would have confirmed that its for preload. Either way, the adjustment did help quite a bit. :var_54:
 
#8 ·
I'm looking at a magazine article on the 650 that says the hammering is caused by the the fork topping out. It says the 650 uses a progressive rate spring while the 1000 has a single rate. Also the 1000 is a cartridge type while the 650 is a damper rod. Additionally, the 650 has 10mm less travel than the 1000. There's a reason the 1000 costs $3000 CDN more than the 650. In other words, the 650 has a budget suspension while the 1000 has some quality components and better engineering. All that being said, I've never noticed a clunk from my 650. Maybe I'm just not trying hard enough.


SS
 
#9 ·
I know it's not spring related. With the sonic .95 it's the same. Maybe fork oil weight but I get the best performance from the 15W. The knock was there with the 10W and you wouldn't want to go any lighter. The forks are not bottoming out. I only hear the noise on shape small bump like railway track or washboard on gravel roads. Almost sounds as if someone is taking a 10lb hammer and is beating on the tire. I don't believe that because the bike is cheap that they compromise the design of the front forks so we should accept it. I've had other cheap bikes before and they never made a clunking noise on washboard. Has anyone ever tried a warranty claim for the noise? How does Suzuki deal with customers who complain of this? :confused:
 
#10 ·
It definitely isn't bottoming. It's the sharpness of the bump, not the size. While the plan for the 1000's forks is better, the result is not so clear. Lighter weight and better specs favor the 650. Both can stand improvement. http://www.citybike.com/index.php?option=com_content&task=view&id=69&Itemid=27
Suzuki says the noise is normal. For once they are right. No harm is being done so it isn't a warranty issue.
 
#12 ·
Anyone with an interest in suspension tuning might want to check this site out. It has everything you ever wanted to know about springs, oil weight, etc.. http://www.strappe.com/suspension.html


SS
 
#13 ·
Knock gone...

I'll add to the mystery. Went on a 300 kilometre ride today down into Washington. The clunk was there when I stopped to pick up my buddy but after we turned around at Sedro Wooley and came up Chuckanut it was gone. No idea why. I do notice that if I apply the front breaks as I'm going over the sharp bumps the clunk is less pronounced or missing. This kind of thing bugs the hell out of me.:bom_furious3:
 
#15 ·
If it was the brake caliper then by applying the brakes it should go away. I'll give it a try. Probably not the brake caliper, the noise is more pronounced than what a caliper could probably produce.
 
#16 ·
I have spent a lot of time tracking down this "clunk" and even though I have no cure, I am certain that it is caused by the forks reaching thier full extent, as in when the wheel leaves the ground. I have driven over speed bumps that could not possibly bottom out the shocks and it seems to be when the wheel leaves the top of the bump that this most often occurs.
G.
 
#17 ·
You know that sounds about right! So if a guy added a really heavy weight fork oil to control rebound the noise should minimized. Not to leave the oil in but just an experiment. Also if the spring had no preload so that the spring did not "bang" as hard when it hit the end of it's travel.
 
#18 ·
Rebound

I was just getting ready to add the same comment when I read the last post.. if that's the source, then slowing the rebound "should" eliminate it.. on the 07 I had recently I rarely heard it though.. mostly when hitting the edge of my driveway, which is a 90 degree lip about 2.5 inches high.. even then I didn't hear it every time. I remember my 04 making the same noise.
 
#19 ·
I was just getting ready to add the same comment when I read the last post.. if that's the source, then slowing the rebound "should" eliminate it.. on the 07 I had recently I rarely heard it though.. mostly when hitting the edge of my driveway, which is a 90 degree lip about 2.5 inches high.. even then I didn't hear it every time. I remember my 04 making the same noise.
So how do we slow the rebound? Too bad a dampener like a piece of rubber couldn't be added to stop the metal to metal clunk. I hear the noise every time I ride mostly because I live on a country gravel road. I know that it doesn't cause any harm but it's annoying to hear a clunk on a bike that has 900 miles on it.
 
#22 ·
Solution for front end knocking on bump

Here's what i did to stop the famous front end knocking , i'm very satisfied :)


i did press the rivets ( 4 tons ) , there was at least 1 inch of vertical play wth each rivet when it was in the press and moving up and down the disk by hand

Sorry for the pics orientation it's impossible to make it right on this site
 

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#23 ·
more pics

There is no more play when the rivets are re-pressed, see the difference in the last picture, also, when stopped, there is no more loose feeling when you push front brakes and moving back and forth
 

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#24 · (Edited)
The front disks are designed to be a floating disk system. Granted if too loose there may be a lot of movement / a bit a rattle. Just take care that you don't cause a brake failure if you decide to re-crimp these rivets. Perhaps for a better understanding of the system, one should goggle floating front disk brake system. Example https://ebcbrakes.com/articles/the-facts-about-floating-motorcycle-rotors-or-discs-by-ebc-brakes/ and https://www.biketorqueracing.co.uk/pages/about/btr-tech-station/fixed-or-floating-brake-discs.htm
 
#25 ·
MY knock was being caused by the fender lift kit and 2 things were occurring.......first the fork wings on the fender were making contact with the fork brace, and second I was having a creaking sound occurring from the mounting point where the bolts went through the plastic holes in fender. Every time I hit a bump or even turned my bars I would hear a distinctive creak, I fixed the clearance on the fork brace to fender wings but the other annoying creaks even after many adjustments drove me nuts. I took off the fender raise kit this past weekend, front end is now quiet as a church fart.
 
#26 ·
Thanks for the answers

Thank you for the link, the rivets were pretty loose ( bike have 86 000 kms ) , i could clearly notice it when stopped and moving back and forth while holding the front brakes, i did test ride and passed on small speed bump at 40 km/h and the big knock is gone, feel much better
 
#27 ·
One more vote for springs. I switched to Cogent Dynamics DDC system and went along with their recommentation for new springs and their drop in cartridges, and voila, the "bonk" is gone. I believe its the springs banging against the fork tubes longitudinally. I made the switch 5 years ago and haven't heard the bang but once or twice since.
 
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