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Old 05-04-2005, 07:44 PM   #1
lpcassie OP
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640 Suspension question

Noob question- I picked up a '05 640 about a month ago and I got it in me today to set the rear sag. I'm kind of a light weight(bout 150lbs in my b-day suit) and have a limited inseam(31"), so I figured that softening up the spring might give me a little more purchase at stoplights. I think the stock spring is set up for someone around 175lbs. To make a long story short when I adjusted it to the recommended total sag (90mm +/- 15mm) I found that the rear ride height sag now exceeded the recommended limit. (recommended 15-20mm) I was at about double that. So what I did was kind of compromise, I decreased the total sag to about 80mm which left my rear ride height sag at around 30mm. I was wondering if all these settings are just guidelines or if I should concentrate on keeping one or the other within the suggested limits? I didn't get to test ride it after I changed the sag today because it was raining(lame excuse). Hopefully tommorow!
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Old 05-04-2005, 07:54 PM   #2
ram1000
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Not only are they just guidelines, but they are guidelines for the optimal suspension effect on a motocross track. The ideal set up is that you would bottom your suspension on the hardest jump or bump you have hte ability to take. The lighter you are the less chance of bottoming, but the harder you ride the more cahnce of bottoming. If the rear of the bike sets lower you can compensate for this by lifting the fork tubes into the tripple clamps till the adjuster touches the handlebars. I am 6'1" and have my tubes slide up lowering the bike about 5/8 of an inch. This makes it steer faster, although if the rear is lowered it will not be much different that the stock steering geometry.
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Old 05-04-2005, 08:09 PM   #3
Renazco
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Even at your weight you need to consider front end dive into corners and such as well as a faster rebound . I'm no expert by no means but the suspension feels spongy enough as it is for a 175# person. WP in harmony with KTM set parameters for adjusting the suspension and warn against over stiffening.

I would say, play around with the front or rear first so you can actually feel the changes being made. Go from one extreeme to the other to see what the suspension is doing and this will pretty much give you a guide.
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Old 05-04-2005, 08:16 PM   #4
lpcassie OP
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Thanks for the input. If it ever stops raining in California this spring I might get a chance to test out the advice.
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Old 05-05-2005, 07:27 AM   #5
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Quote:
Originally Posted by lpcassie
I was wondering if all these settings are just guidelines or if I should concentrate on keeping one or the other within the suggested limits?
i am going to disagree with ram1000 on this. i don't think they are just "guidelines".

the shock manual is pretty clear on this point. I don't have it in front of me right now but it doesnt sound like they are inferring its a range for optimal effects, MX or otherwise. To me it sounds like they are laying down the min/maximums.

It states fairly clearly that the operator is to change the spring if the sag doesnt fall within the stated parameters. I think that if you don't stay inside the guidelines you are likely unduly taxing the shock and decreasing its lifespan. At some point I bet the adjustment and operation would reach the possibility of catastrophic failure.

If in doubt contact a suspension tuning shop; don't trust a bunch of blow hards on the net. replacements are EXPENSIVE!
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Old 05-05-2005, 01:24 PM   #6
clintnz
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My '03 640 was, according to the manual, set up for a 70kg (155 lb) rider, I am 71 kg & it certainly felt about right. There have been no suspension changes to the '05 (AFAIK) so your bike most likely came out of the factory already set up for your weight.

Cheers
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Old 05-05-2005, 01:30 PM   #7
lpcassie OP
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Thanks Mr Popscicle, I took your advice and called Aftershocks in Palo Alto and spoke with the owner. (probably what I should have done in the first place) He said for that model shock the static sag is the most important measurement, He sets it a 22mm.
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Old 05-05-2005, 01:32 PM   #8
meat popsicle
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Quote:
Originally Posted by lpcassie
Thanks Mr Popscicle, I took your advice and called Aftershocks in Palo Alto and spoke with the owner. (probably what I should have done in the first place) He said for that model shock the static sag is the most important measurement, He sets it a 22mm.
Glad to be of service cassie (?). Wish I could afford to pay those people to upgrade my suspension - I am 200 +gear... rides kinda like a 72 cadillac.

BTW, you don't have to be so formal around here; call me meat.
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Old 05-05-2005, 02:20 PM   #9
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I'm with bo and meat mixed together .

The best thing you can do is play with your suspension settings to find out what's BEST FOR YOU. I say start at the recommended/factory settings. Adjust your static & race sag. Take note of those settings and then go ride your favorite trail & street.

Start making changes to the settings and see if that helps or hurts how the ride goes. But, like re-jetting, try to make only one change at a time.

Eventually you'll find the setting(s) you like best.

Personally, I have mine all set in a compromise. I almost always have side panniers on while on the street, but everything comes off if I'm going to riding in some tight trails. To prevent me from having to readjust the rear shock every time I drop the luggage, I measured sag both loaded and 'naked'. Set it for the middle. I'm happy with the way it works.

I little psi change in the tires & a few clicks up front and it runs/handles just fine for my desert riding conditions. When the day is over and I'm riding home via the highway, the psi gets returned & the clickers are set back to 'street'.

No hassle.
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Old 05-05-2005, 04:15 PM   #10
lpcassie OP
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Talking

Thanks for the input. Ive been dicking around with it for the past 3 hours and I think Im where I want to be for now. Im a little over the 22mm recommended static sag but I dropped my triple clamps down about 5/8 in. on my forks. This combination lowered my seat height a little bit so Ive got a little better purchase at a standstill. The front end is a little more responsive and the rear isnt so jarring in the rough stuff. I might buzz it down to Hollister tomorrow morning to give it a workout. Thanks again, great website!!
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Old 05-05-2005, 06:23 PM   #11
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Quote:
Originally Posted by lpcassie
I might buzz it down to Hollister tomorrow morning to give it a workout. Thanks again, great website!!
If you are going to hollister, you are just a wee bit shy of "clear creek", and from what i hear its a fantastic place (long as its not dusty). search for it on the web, it is supposedly just past Pinnacles on the 25 (though I didnt see a sign last time thru...).

Hello from San Jose check out the regional west forum for local rides and such. don't forget to sign in and show us a pic of the bike in the KTM threads; it's kinda like dogs sniffin eachother...
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Old 05-03-2009, 11:17 AM   #12
makazica
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Help me understand!

First of all, I admit that I am maybe a bit dumb and unaducated about the topic, but I'm having a little trouble understanding the pic below.

On the pic there are two lines on the upper part of the shock absorber, and the distance between them is called A. A = 27mm.

I'm having trouble understanding what A is. The difference between the fully extended spring and, in this case, the basic setting for preload??

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Old 05-03-2009, 11:50 AM   #13
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I'm also a shorter light weight but for whatever reason I have some long sticks. So I can tippy toe my bike. All geared up, I'm fine. But when I first got my bike I loosened the rear a bit and called it good. I tend to ride hard enough that I dont want a spongy ride anyways. Although the front is almost to soft sometimes but I attribute that to the freaking huge fuel tank holding 4+ gallons of fuel.
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Old 05-03-2009, 12:27 PM   #14
Luke
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Quote:
Originally Posted by makazica
First of all, I admit that I am maybe a bit dumb and unaducated about the topic, but I'm having a little trouble understanding the pic below.

On the pic there are two lines on the upper part of the shock absorber, and the distance between them is called A. A = 27mm.

I'm having trouble understanding what A is. The difference between the fully extended spring and, in this case, the basic setting for preload??

A is the amount the spring is compressed when the shock absorber is fully extended. To set it, remove the spring from the shock and measure the length. It should be about 260mm. Then install the spring on the shock and adjust the preload collars so the spring is 27mm shorter- or about 233mm.

Edit: note that the conversion is wrong. 27mm is 1.1 inches, not 0.9
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Old 05-03-2009, 12:48 PM   #15
makazica
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Thanks Luke....that's the answer I was looking for. Now it makes sense.
Do I really have to remove the spring to measure its length or is it good enough to go with the specifications listed for my spring.....?

Thanks again!
M.
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