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-   -   BMW G650XChallenge FRONT SUSPENSION (http://www.advrider.com/forums/showthread.php?t=277533)

lkongo 10-21-2007 09:20 AM

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 !!

lkongo 10-26-2007 12:51 PM

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 Íhlins has other springs for the fork.

shardzero 10-27-2007 03:39 AM

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.

lkongo 10-27-2007 09:20 AM

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.

Max Kool 10-27-2007 10:35 AM

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?

lkongo 10-27-2007 03:49 PM

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

Sonymalc 11-25-2007 05:55 PM

My current front settigns are -4 on compression and +2 on rebound. So far the front feels good but I am still experminting with it.

GB 11-25-2007 05:57 PM

It'll be nice to be able to dial in my front suspension at long last..... when I get my X-C.. :thumb

:lurk

Dirt Hugger 11-28-2007 05:05 AM

Headshake anyone?
 
Just a question about setting up the XChallenge for road use (some commuting during the week) :norton

I weigh just under 100kg with full kit, currently have the back at 110psi cold, which seems correct according to the all-knowing bubble, rebound at "comfort"...

Have the front compression at max minus 5 clicks, and rebound at max minus 5 clicks (quite a hard setup as was suggested by the dealer)

The bike feels OK at speeds under 110 km/h on the tarmac, but I can detect the beginning of a headshake when going faster than this. :eek1 Tyre pressure is 1.9 front, 2.2 back, stock Metzeler Saharas.

What have you guys found to be a good road setup, especially the guys tipping the scales at about 100kg's?

Max Kool 11-28-2007 05:48 AM

I haven't ridden the stock Sahara's, but I do know the Xchallenge is very sucseptible to its tires. Especially the rear one. When I bought mine it had Michelin Enduro III and IV tires and at 22 psi it would shake its head at anything above 70 mph.

I changed the rear for a Michelin Baja and it was gone. Completely.

GB 11-28-2007 06:32 AM

I've ridden the bike in stock form, stock tires at 150 km/h without the slightest hint of any shake or shimmy or anything else.. awesome ride!

lkongo 11-28-2007 11:50 AM

Quote:

Originally Posted by Gadget Boy
I've ridden the bike in stock form, stock tires at 150 km/h without the slightest hint of any shake or shimmy or anything else.. awesome ride!

+1

I have taken my X to 180km/h on the display (maybe 165-170 in reality??) with the wind from behind and no headshake. Tyres: Pirelli MT21.

Dirt Hugger 01-03-2008 06:44 AM

Think I found it
 
Quote:

Originally Posted by Dirt Hugger
Just a question about setting up the XChallenge for road use (some commuting during the week) :norton

I weigh just under 100kg with full kit, currently have the back at 110psi cold, which seems correct according to the all-knowing bubble, rebound at "comfort"...

Have the front compression at max minus 5 clicks, and rebound at max minus 5 clicks (quite a hard setup as was suggested by the dealer)

The bike feels OK at speeds under 110 km/h on the tarmac, but I can detect the beginning of a headshake when going faster than this. :eek1 Tyre pressure is 1.9 front, 2.2 back, stock Metzeler Saharas.

What have you guys found to be a good road setup, especially the guys tipping the scales at about 100kg's?

During the past few weeks I have experimented with the pressure of the rear shock. It seems to have quite an influence on the headshake/nervous handling above 110 km/h I had previously mentioned.

Seems like when the rear is pumped too hard, the nervousness is more pronounced. When setting the rear sag to 90-100mm (cold) no headshake or unstable behaviour (this translates to about 105psi in the shock). I have also reverted to the default front fork compression and rebound settings.

My conclusion is that a overly hard rear shock increases the steering angle up to a point where the handling becomes quite nervous on tarmac at highway speeds, which makes sense...

Ah, the joys of getting to know the personality of a new steed... :lol3

Metteke 01-06-2008 05:23 AM

I had my level bubble replaced under warranty (since the original one was placed wrong), and what I notice now is that according to the new setup of the bubble, I had to let air out the rear! And yes, for me, it is really better. We have a lot of nasty small deep holes because of tractors and farmers cuttings and stuff, and it takes them super-soft. Like they are not there!:clap
Ok, I do not jump, nor do I ride on an MX-like track... But for me, it works.
Suspension in the front is way up soft, something like Ikongo's setting (R -5, compression -5 I think) Works well for me and my riding... (smooth, not aggressive and fast flat drifting, no big jumps)


Quote:

Originally Posted by Dirt Hugger
During the past few weeks I have experimented with the pressure of the rear shock. It seems to have quite an influence on the headshake/nervous handling above 110 km/h I had previously mentioned.

Seems like when the rear is pumped too hard, the nervousness is more pronounced. When setting the rear sag to 90-100mm (cold) no headshake or unstable behaviour (this translates to about 105psi in the shock). I have also reverted to the default front fork compression and rebound settings.

My conclusion is that a overly hard rear shock increases the steering angle up to a point where the handling becomes quite nervous on tarmac at highway speeds, which makes sense...

Ah, the joys of getting to know the personality of a new steed... :lol3


johan 10-24-2008 05:57 AM

Anyone had any progress on the whole front suspension debacle on the X? Compresses way too much on breaking, and harsh on fast movements (e.g fast riding on bad gravel and rocky roads)

Is there some holy grail to fix this (I don't mind sending it for service etc)? I love the bike, but this bit annoys me


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