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Old 10-21-2007, 08:20 AM   #1
lkongo OP
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Question BMW G650XChallenge FRONT SUSPENSION

Hi!

My impression of the bikes front suspension is that it's hard at stock setting. One advice I got was "soften the compresion an increase rebound"

I soften the Compression and increased Rebound with a very bad result. The bike felt very unstable.

I'm not experienced with either riding nor suspension settings so after that I have read as much info I've found about suspension settings.

One rule of thumb I have found is to set the rebound first to avoid thinking that the compression is wrong.

I have finally got the suspension feeling better on my XChallenge and here are my conclusions this far:

-The stock Rebound is high on this bike.
-The spring is probably made for a rider that is heavier than my 72kg.

My present setting (still slowly decreasing the settings) is:
C= -4 from stock
R= -5 from stock

My free sag is 35mm which is on the high side of recommended (that's why I belive the spring is maybe a little stiff to my weight)

Race sag is 53-55mm which is somewhere around the recomendations I've read.

Mostly I use approx 50% of the travel and accasionally 70%. I'm not an aggressive rider though so it may go deeper if i would do a hard landing. It's difficult to see how much is used but I can fel the oil film to 190mm and clearly see it at half of the travel.

I will keep trying to improve the setting because it really makes a difference in both comfort and control.

I'm very interested in YOUR weight/skill level/setting and opinion about the front !!
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Old 10-26-2007, 11:51 AM   #2
lkongo OP
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I asked the Swedish BMW Tech. manager about the suspension and he said that the bikes suspension is made for a rider weighing 75kg.

Surprising in my opinion...

He also said that Öhlins has other springs for the fork.
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Old 10-27-2007, 02:39 AM   #3
shardzero
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I have done ramp to flat landings and use stock settings. Bike feels stable on 'pea' gravel, especially good on sand, good feed back on 'whoops'. The stock setting is probably firm but I think thats because the bike was designed for a reasonable amount of abuse. For road going softness maybe the country has better setups available. I am 69 kg and ride with 110 psi in the rear. That is hard, but I find the rear responds very nicely for me at this pressure. It probably is not useful to talk clicks and 'feel', as unless your riding the same substrate, are the same weight and similarly aggresive/placid your going to run into issues of relativity.

If your trying to smooth out minor roughness decrease the tyre pressure to low 20's high teens, depending on substrate and riding style/speed.
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Old 10-27-2007, 08:20 AM   #4
lkongo OP
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Quote:
Originally Posted by shardzero
I have done ramp to flat landings and use stock settings. Bike feels stable on 'pea' gravel, especially good on sand, good feed back on 'whoops'. The stock setting is probably firm but I think thats because the bike was designed for a reasonable amount of abuse. For road going softness maybe the country has better setups available. I am 69 kg and ride with 110 psi in the rear. That is hard, but I find the rear responds very nicely for me at this pressure. It probably is not useful to talk clicks and 'feel', as unless your riding the same substrate, are the same weight and similarly aggresive/placid your going to run into issues of relativity.

If your trying to smooth out minor roughness decrease the tyre pressure to low 20's high teens, depending on substrate and riding style/speed.
Good input, thanks!

When you say it's specially good for sand confirms that the front has a high rebound damping??

I also think it works very well i sand/whoops to when it works relatively slow.

On harder conditions where it has to work very fast (series of small holes for example) it doesn't work that good.

I have softened C to -6 and R still at -5 and I think this is the best setting for me so far.

I run the back at 90psi cold which is 105-110psi warm. Works good.
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Old 10-27-2007, 09:35 AM   #5
Max Kool
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Quote:
Originally Posted by lkongo
Good input, thanks!

[..]

I also think it works very well i sand/whoops to when it works relatively slow.

On harder conditions where it has to work very fast (series of small holes for example) it doesn't work that good.

I have exactly the same experience. I weigh around 100kgs and I feel the springs themselves are about right for my weight. I use around 90% of the available suspension travel, never bottoms out. In sand and other soft stuff I like the front, but on stones and rocks the front feels harsh. Riding on a railway bed (or other rocky stuff) is no fun. I have the feeling the low speed damping is quite ok, but the high speed damping is too much. I run the compression 5 clicks softer than stock, and the rebound 3 clicks softer.

Maybe I need to go down some more on both the compression and rebound?

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Old 10-27-2007, 02:49 PM   #6
lkongo OP
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Quote:
Originally Posted by Max Kool
I have exactly the same experience. I weigh around 100kgs and I feel the springs themselves are about right for my weight. I use around 90% of the available suspension travel, never bottoms out. In sand and other soft stuff I like the front, but on stones and rocks the front feels harsh. Riding on a railway bed (or other rocky stuff) is no fun. I have the feeling the low speed damping is quite ok, but the high speed damping is too much. I run the compression 5 clicks softer than stock, and the rebound 3 clicks softer.

Maybe I need to go down some more on both the compression and rebound?
What I got explained to me is that the Rebound controls the energy in the spring.

The rebound reduces speed both upwards and downwards of the travel, that's why many riders think the Compression is to high when the fork feels hard/harsch. The real problem may be that the rebound limits the speed of which the suspension moves.

That's why one always should start setting the rebound where it feels the best and then work with the compression.

I've tried rebound as low as -7 but the front got a little "bumpy" (uncontrolled). -5 is where I have found the best so far.

Then offcourse a higher compression may need a higher rebound but the specialist I asked said that's mariginal.

Why not try -4/-5 in rebound and stock--/-2 in compression first to see if you where fooled of a to high rebound.

As I mentioned earlier I'm a beginner but what the specialist, I got advice from, said is very logical in my opinion.

Here is the guy I got some advice by mail from:

http://www.brucessuspension.com/kb4.htm
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Old 06-20-2010, 05:05 PM   #7
davesmyth
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A little Suspension Algebra for the G650X Challenge

Gentlemen,

I've been reading a lot of threads that advocate softening up the suspension to improve the ride of the G650X Challenge. To a certain extent, I agree; especially if you're going long distances on hardball or improved dirt roads. Soft suspension, however, doesn't solve the constant problem of fork dive, and is particularly bad for riding in sand and loose dirt. Here's what I've come up with, so please take it or leave it as you see fit:

BMW sets the Compression and Rebound at approximately +11 clicks from "0" (all the way counterclockwise to full stop). I don't know if this is true across the board, but that seems to be the general consensus. If these settings are made for a 75kg man, then it stands to reason that you can do a little Algebra and arrive at the perfect setting for your weight. I fiddled with the suspension to get the best road setting for me using Pirelli Scorpion Rally tires, front and rear (very aggressive knobby tires, but DOT approved). I arrived at +11 for Compression, and +9 for Rebound. Rear suspension was set to 114psi and "Soft" setting using the following equation: 85kg/ 97.2psi = 100kg/ x. x = 114psi. I used 85kg because 97.2psi is what BMW recommends for a 85kg man in the G650X Challenge Owner's Manual.

+11/ +9 (from "0") is fine for a 75kg man off-road, I suppose, but I weigh 100kg with riding gear. For whatever reason, my Compression adjustment has 23 clicks, while my Rebound adjustment has 25 clicks. Doing some quick math, I realized that my optimal road settings put my Compression at 48% of max, and my Rebound at 36% of max. That is a perfect 4:3 ratio, which made it very easy for me to adjust my off-road oriented setting for my weight. I set my Compression to +15 from "0" (75/11 = 100/ x; x = 15), and my Rebound to +12 from "0" (75/9 = 100/x; x = 12). I set my Rear Suspension to "Hard", and left the same air pressure at 114psi.

I took my trusty bike off-road and rode in the training area near my house. The sand out there is terrible, and with soft suspension, your nose dives and it is miserable going. With my harder settings, I was able to glide effortlessly through the sand. I accidentally hit a 3ft deep, 10ft long, and 4ft wide hole coming over a blind hill that I couldn't avoid. My suspension soaked it up like it was nothing! I also drove through a creek that had water crashing completely over the bike. The bike was totally submerged and made it through like it was the most normal thing in the world. I would estimate that the water was 3.5-4ft deep. My balls and ass definitely got wet!

On improved and gravel roads, the front wheel felt like it floated a bit, but I never felt like I was not in control. I was also moving down the road at 55-60mph (90-100kph). On the road, these suspension settings allowed for a smooth, firm ride with no headshakes until around 70mph (110kph). For the type of riding that I do 90% of the time, that is about ideal. If I want to ride longer distances and spend more time on hardball and improved dirt roads, I can adjust my settings easily back to my +11 C/ +9 D, change the Rear to the "Soft" setting and be good-to-go.

Suspension is a very personal thing, so you have to find what works best for your style of riding. I hope that these numbers provide you with a good start point for your own suspension adjustments. If you have any questions about how I arrived at my numbers, feel free to send me a PM.

Regards,
Dave

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Old 06-22-2010, 11:07 AM   #8
sideway5
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Quote:
Originally Posted by davesmyth
Gentlemen,

I've been reading a lot of threads that advocate softening up the suspension to improve the ride of the G650X Challenge. To a certain extent, I agree; especially if you're going long distances on hardball or improved dirt roads. Soft suspension, however, doesn't solve the constant problem of fork dive, and is particularly bad for riding in sand and loose dirt. Here's what I've come up with, so please take it or leave it as you see fit:

BMW sets the Compression and Rebound at approximately +11 clicks from "0" (all the way counterclockwise to full stop). I don't know if this is true across the board, but that seems to be the general consensus. If these settings are made for a 75kg man, then it stands to reason that you can do a little Algebra and arrive at the perfect setting for your weight. I fiddled with the suspension to get the best road setting for me using Pirelli Scorpion Rally tires, front and rear (very aggressive knobby tires, but DOT approved). I arrived at +11 for Compression, and +9 for Rebound. Rear suspension was set to 114psi and "Soft" setting using the following equation: 85kg/ 97.2psi = 100kg/ x. x = 114psi. I used 85kg because 97.2psi is what BMW recommends for a 85kg man in the G650X Challenge Owner's Manual.

+11/ +9 (from "0") is fine for a 75kg man off-road, I suppose, but I weigh 100kg with riding gear. For whatever reason, my Compression adjustment has 23 clicks, while my Rebound adjustment has 25 clicks. Doing some quick math, I realized that my optimal road settings put my Compression at 48% of max, and my Rebound at 36% of max. That is a perfect 4:3 ratio, which made it very easy for me to adjust my off-road oriented setting for my weight. I set my Compression to +15 from "0" (75/11 = 100/ x; x = 15), and my Rebound to +12 from "0" (75/9 = 100/x; x = 12). I set my Rear Suspension to "Hard", and left the same air pressure at 114psi.

I took my trusty bike off-road and rode in the training area near my house. The sand out there is terrible, and with soft suspension, your nose dives and it is miserable going. With my harder settings, I was able to glide effortlessly through the sand. I accidentally hit a 3ft deep, 10ft long, and 4ft wide hole coming over a blind hill that I couldn't avoid. My suspension soaked it up like it was nothing! I also drove through a creek that had water crashing completely over the bike. The bike was totally submerged and made it through like it was the most normal thing in the world. I would estimate that the water was 3.5-4ft deep. My balls and ass definitely got wet!

On improved and gravel roads, the front wheel felt like it floated a bit, but I never felt like I was not in control. I was also moving down the road at 55-60mph (90-100kph). On the road, these suspension settings allowed for a smooth, firm ride with no headshakes until around 70mph (110kph). For the type of riding that I do 90% of the time, that is about ideal. If I want to ride longer distances and spend more time on hardball and improved dirt roads, I can adjust my settings easily back to my +11 C/ +9 D, change the Rear to the "Soft" setting and be good-to-go.

Suspension is a very personal thing, so you have to find what works best for your style of riding. I hope that these numbers provide you with a good start point for your own suspension adjustments. If you have any questions about how I arrived at my numbers, feel free to send me a PM.

Regards,
Dave
The reasoning behind the setting for the rear shock I can totally dig, but you misinterpret the front settings imho. The compression and rebound settings has nothing to do with rider weight per se. What these settings do is simply limit the speed of which the fork is allowed to compress or retract and their setting is ultimately determined by your riding style and to the terrain you ride. They provide a dampening effect to the spring which is the actual component that according to BMW is chosen to suit a 75kg rider. So in essence, if you weigh significantly more or less than 75kg you really should consider replacing the spring with a proper one for your weight. That being said, your setting for the fork may be excellent, but your "math" to get there was somewhat strange.

Happy riding!
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Old 07-11-2011, 10:42 AM   #9
Cycle61
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Well, got the rear end aired up properly now. What a difference!! The bike now actually sits at it's intended height, and consequently the front end is feeling far better. Fresh oil and some knob twiddling and we should be good to go for a couple weeks, at least.

Edit: use is going to be mostly on-road, so I'm probably not anywhere near as critical as some riders.
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Old 08-14-2012, 12:58 PM   #10
FinnDuro
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Quote:
Originally Posted by cobrakai View Post
I don't necessarily need pictures, just to know if they are threaded inside or not.
No such threading needed to add to the axle clamps. The compression valve is actually threaded into the cartridge fork tube that sits inside the fork slider tubes. Kind of hard to explain, but it all makes sense once you actually see a fork disassembled for the first time.

YouTube fork seal change videos, check them out.
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Old 05-10-2013, 12:13 PM   #11
gsstampeder
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Left damper unit

Need some advise from the wise...had my x-c in for fork seals and some other work and the tech called to tell me my left damper unit was pooched. The part from Max's is $350, plus shipping to me. Is there another solution? I'm not opposed to upgrading the forks with others, but I'm not sure of availability to locate replacement upgrades. Any suggestions?
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Old 05-10-2013, 09:34 PM   #12
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Quote:
Originally Posted by gsstampeder View Post
Need some advise from the wise...had my x-c in for fork seals and some other work and the tech called to tell me my left damper unit was pooched. The part from Max's is $350, plus shipping to me. Is there another solution? I'm not opposed to upgrading the forks with others, but I'm not sure of availability to locate replacement upgrades. Any suggestions?
ping inmate mbfj40, he had a complete set of forks for less than that one part.
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Old 05-11-2013, 05:30 AM   #13
gsstampeder
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Quote:
Originally Posted by aprilian View Post
ping inmate mbfj40, he had a complete set of forks for less than that one part.
Thanks, I checked the thread and I believe his forks came off an X=Country. I have an X-Challenge and I think the travel is less on an x-country....????
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Old 05-11-2013, 07:49 AM   #14
Colebatch
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Quote:
Originally Posted by gsstampeder View Post
Thanks, I checked the thread and I believe his forks came off an X=Country. I have an X-Challenge and I think the travel is less on an x-country....????
X-Challenge has 270mm fork travel
2007-2008 X-Country has 240mm
2009 X-Country has 220mm
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Old 02-11-2014, 11:55 AM   #15
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About to go ahead with the machining of my axle clamps. Does anybody have any pictures of the bottom of the clamp with the adjuster in place. Would like to know if the adjuster sticks out at all
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