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Old 12-17-2008, 12:37 PM   #1
10Cup OP
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F800 GS Rear Shock Spring Replacement..

I could not find much about this project on ADV prior to starting. Did find some info on the F650 which helped somewhat. Here is a specific F800GS project on changing the rear shock spring.

I wanted my new F800GS to be about an inch lower so ordered in the Hyperpro shock spring. Here is what I ran into.

First spring is .150 smaller in diameter, it will fit ,but requires you to bevel the spring edges on the internal diameter on each end so that it will fit over the lower and upper spring centering washers. Not a big deal but definitely made for the F650GS or S and NOT the F800GS.

Changing out the springs was not too bad once you have a good spring compressor. I used the Harbor Freight compressor shown here. To those who might use it in the future, cost is $12 BUT it is made for larger car coil springs and you will have to grind down the ears for clearance on the BMW shock. Works ok but not the best.


Once compressed you can then simply slide down the preload assembly exposing a small retaining wire that rides in a grove on the shock body and the inner preload assembly sleeve rides up on it to capture it in place and lock the assembly.

Once the stock spring is off, putting on the new spring is easy since it is one inch shorter and you don't need a spring compresser with it.

As another point of information. Eye to eye, the stock shock is 17". A shock that is 16.4" on these same deminsions would have been perfect for my size and inseam.

Also found that with the Hyperpro spring the bikes rear sag is quite a bit more since this spring is a "rising rate" spring and not a straight would spring like the stock. This resulted in the bike being too low and the swing arm was almost straight horizontal when sitting on the bike.

So I machined an aluminum collar .400 thick and placed it under the lower spring locating washer. Result is the bike now is lowered only 1 inch with suites me best with a 32" inseam and 170 lbs. I then slid the forks up in the triple tree about an inch and the bike sits level and I feel much more in control being able to flat foot the bike.

Another point, the side stand now is "just right" and the bike has about a 10 degree tilt. So this conversion solved excessive lean angle as well. Center stand works fine too.

Have not had the opportunity to ride yet (29 degrees with ice here) but will post more when I do.

here are some pictures of the finished project.

Special aluminum collar machined to raise shock spring.


Side view of shock..


Total time on this project was about four hours, most of which was spent making the aluminum collar on my lathe.
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10Cup screwed with this post 12-17-2008 at 01:56 PM
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Old 12-17-2008, 06:37 PM   #2
Ed@Ford
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Unpleasant that BMW requires a spring compressor for spring removal.

In all your work, did you determine or learn spring rates on F650 and F800? Reason I ask is I have an F650 on order and every demo ride tells me the F650 needs the stiffer spring rate of the 800. Also F650 forks need help as well...just a bit stiffer.
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Old 12-17-2008, 07:26 PM   #3
kkug
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Do you think it is possible to machine a new grove for the clip ? And then another part of my question is --does it look posible to disassemble this shock so a longer top out spacer can be machined and installed ?

Is the Hyper pro spring rate close to the stock one ?


Thanks for taking this on !
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Old 12-18-2008, 06:32 AM   #4
nat_han
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Lower Suspension by 1"

hi guys!

i'm looking for an aftermarket brand(ohlins or wilburs would be great) rear shocks that is lower as compared to my stock F800GS one.

Any way of getting one now? need it lowered by about 2cm or 1" roughly...
cant flatfoot the bike with both legs down.. am using the low seat also..
thanks alot for any help rendered.
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Old 12-18-2008, 06:37 AM   #5
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Quote:
Originally Posted by Ed@Ford
Unpleasant that BMW requires a spring compressor for spring removal.

In all your work, did you determine or learn spring rates on F650 and F800? Reason I ask is I have an F650 on order and every demo ride tells me the F650 needs the stiffer spring rate of the 800. Also F650 forks need help as well...just a bit stiffer.
No, sorry I did not. But I suspect you are correct. Will be interesting to see if this spring with the rising rate wind works well or not.
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Old 12-18-2008, 06:40 AM   #6
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Quote:
Originally Posted by kkug
Do you think it is possible to machine a new grove for the clip ? And then another part of my question is --does it look possible to disassemble this shock so a longer top out spacer can be machined and installed ?

Is the Hyper pro spring rate close to the stock one ?


Thanks for taking this on !
First, no you would not want to machine on the shock body it is very thin and since it is internal to the sleeve that rides up to enclose it it would have to be done with additional collars. The collar could be put on top or bottom that part doesn't matter.

The Hyper pro spring is a rising rate spring so it is not comparable to the straight wound stock spring but I do know that the initial compression is less than the stock spring and as such you get more initial compression.
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Old 12-19-2008, 01:34 PM   #7
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Laugh

Rode this new set up about 180 miles in the Ozark back roads and fire service roads today and have to say it is awesome! The lower ride height also saved my bacon on one road I found impassable due to heavy rocks and mud. Several of the roads are very rough and though the suspension used it's full compression several times both front (with stock springs) and rear with the Hyperpro modified it never bottomed out and performed flawlessly.

I am very happy with this set up. Now I just have to get my Corbin seat and I will be able to ride a lot more miles.......this seat really hurts your but.....and other things..

Mike

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Old 12-19-2008, 08:19 PM   #8
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Good stuff

Mike,
Thanks for taking the time to show what you did. Looks like you got the results you were expecting. I was following your thread closely because my 30 " inseam is challenged sometimes when offroad.

If you get a chance, post a photo of you sitting on the bike showing your reach.
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Old 12-20-2008, 07:37 AM   #9
nat_han
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Am i able to custom an order for a spring length that is only 30mm shorter instead of the 50mm one that mkspear has used?

the bike is slightly too high for comfort...
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Old 12-20-2008, 09:23 AM   #10
itsatdm
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MKspear, how is the rebound characteristics with the Hyperpro. I find the stock shock does not have enough rebound control. Feels "bouncey"
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Old 12-20-2008, 12:22 PM   #11
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Quote:
Originally Posted by divingbiker
Mike,
Thanks for taking the time to show what you did. Looks like you got the results you were expecting. I was following your thread closely because my 30 " inseam is challenged sometimes when off road.

If you get a chance, post a photo of you sitting on the bike showing your reach.
Darrell, here is a picture of me on the standard seat. 32" inseam. Knees slightly bent. I have about 10lbs in the tail bag but have plenty of preload adjustment left. I am only using about half of what is available right now. I can go lower or higher with ride height.

Please excuse my dirty bike ...

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Old 12-20-2008, 12:25 PM   #12
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Quote:
Originally Posted by itsatdm
MKspear, how is the rebound characteristics with the Hyperpro. I find the stock shock does not have enough rebound control. Feels "bouncey"
I have not found that to be the case at all. In fact I am at one and a half turns out from full rebound. I set it like the manual says all the way to the right until it stops and then turn back counter clockwise a turn and a half. So far I am very pleased. Keep in mind however that it has been very cool which will effect damping, it may be totally different in the heat.
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Old 12-20-2008, 12:32 PM   #13
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Quote:
Originally Posted by nat_Han
Am i able to custom an order for a spring length that is only 30mm shorter instead of the 50mm one that mkspear has used?

the bike is slightly too high for comfort...
Actually I did not have that option and just used the 40mm lowering shock spring that Hyperpro offered. It is a full inch shorter than stock so I made a .400 thick spacer to place under it. A spring that would be 30mm shorter is almost the same (1.18") shorter. I would suggest you try to find one that is only 12mm shorter (.47") and then you would not need the spacer under it. IF you can find one. Also take into account is the spring straight wound or progressive. Mine is what Hyperpro calls rising rate (similar to progressive) and this gives you a little more initial sag when you get on the bike but quickly catches up with more resistance as the spring is compresses further. Seems to be the way to go. My ride is smoother but does not bottom out either.

I have the front forks slide up about 1/2" in the triple trees too.

So far so good.
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Old 12-20-2008, 10:53 PM   #14
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Quote:
Originally Posted by mkspear
Actually I did not have that option and just used the 40mm lowering shock spring that Hyperpro offered. It is a full inch shorter than stock so I made a .400 thick spacer to place under it. A spring that would be 30mm shorter is almost the same (1.18") shorter. I would suggest you try to find one that is only 12mm shorter (.47") and then you would not need the spacer under it. IF you can find one. Also take into account is the spring straight wound or progressive. Mine is what Hyperpro calls rising rate (similar to progressive) and this gives you a little more initial sag when you get on the bike but quickly catches up with more resistance as the spring is compresses further. Seems to be the way to go. My ride is smoother but does not bottom out either.

I have the front forks slide up about 1/2" in the triple trees too.

So far so good.
thanks for the help.
i'm looking to order the 50mm lower shock spring..might consider the front fork springs but dunno the price as yet and whether they help in my riding as current OEM ones are very new as well...

i am guessing that i'm shorter than u with smaller in-seam so i'd go with the 50mm kit. not sure if the bike would look like a "cruiser" type after the change. care to add your opinions? just afraid that the bike's handling and looks would be screwed after installing the lowering kit.
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Old 12-20-2008, 11:19 PM   #15
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I want to lower my bike about an inch and am looking for a shorter rear spring. Where can I get a shorter rear spring? I can't seem to find the hyperpro spring for the F8GS available anywhere on line.
Thanks,
Mike
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