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I Ohlin-ized My SM - Rear Shock

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Well, my shock finally arrived yesterday. It is the reccomended shock sold by Ohlins for an SM. Ohlins P# SU 506. I added an adjustable preload add-on that with simply turning a small bolt, you can increase the prelead about 10mm on the spring. The down side to this is you have to have the preload close to correct before you mount the shock. The other issues is clearance with the adjuster and the oil breather box as it barely fits. As it is now, the adjuster is at the top and I think the collar it sits on and the adjuster can be swapped, moving the adjuster to a lower point that may not be so tight with the oil breather box. I also had the shock shortened internally by 11mm.

I had Kouba DRZ2's on the bike, they are reputed to lower it by 1.5" and the seat to ground height was perfect for me, although I also had excessive suspension sag. Before I started to do the shock swap and reinstallastion of the stock links, I took some measurements fron the 'bump' on the swing arm to the helmet lock (where the pin goes into the lock) I picked these arbitrary points as I felt they were duplicateable measuring points. This was all done with the back tire in the air, suspension at full extension.

With Kouba DRZ2's 22.25"

With Stock Links 23.5"

With Shortened Ohlins 22.5"

This means the 11mm shorter than stock shock netted a drop of appoximately 1" (25.4mm) which means at full extension, the linkage ratio is 2.31 to 1, far from the 5 to 1 that others have previously reported. I had been hoping for a 1.5" to 2" drop. I may get a longer spacer put in the shock

to lower it another .75 inches which means I need a spacer about 8mm shorter, for a total of 19mm. At least now I know the relationship.

OEM Travel is supposed to be 10.9" ( 276mm) and Ohlins advertises this shock to have a stroke of 124.5mm. If the travel measurement is from full extension to bump stop, the average ration becomes 2.22 to 1, right in line with my above calculations.

The desired amount of 19mm is only a loss shock travel of 15.3% so sometime, this will be done with moving of the adjuster.

I did not get to ride it as it began to rain as I was finishing up, but I snapped two pictures. I had to cut the side panel to provide access to the upper damping adjuster.

OhlinsPreloadAdjuster.jpg

OhlinsDampingAdjuster.jpg

I'll be sending the forks to Ohlins in a week or so to enable them to Ohlin-ize them too, just have to wait for them to return from Daytona.

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Looks good William.

The lowering bit, My S shock was 10 mm shorter, this lowered the back by nearly 50 mm.

But not the race sag, that only went down about 25 mm, because I used a stiffer spring to suit my fat ass.

I suspect this is what has effected yours as well.

To make sure (if your bothered) you need to measure the ride height with the suspension unloaded to be sure of the linkage ratio, with both shocks.

Neil. :applause: :applause: :lol:

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Hey Neil, all my measurements are with the rear tire off of the ground to prevent any variables from entering the equation. A 11mm shorter shock netted a drop of about 26MM (+/- 3mm as I was not going for 100% accuracy, just a close relative approximate).

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Yeah, I was a bit surprised when I took all the numbers today in the three configurations. I really though the ratio was between 3.6~4 to 1. The drop I was looking for is more like you experienced. Live and learn.

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Yeah, I was a bit surprised when I took all the numbers today in the three configurations. I really though the ratio was between 3.6~4 to 1. The drop I was looking for is more like you experienced. Live and learn.

Did you guys lower the front too so the overall geometry is closer to stock? Won't lowering the rear by the amounts you are talking about have a significant effect on the weight over the front wheel, front end feel, turn in speed and ability to hold a line in a corner. I am coming from a sportbike background but the same principles should apply.

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Did you guys lower the front too so the overall geometry is closer to stock? Won't lowering the rear by the amounts you are talking about have a significant effect on the weight over the front wheel, front end feel, turn in speed and ability to hold a line in a corner. I am coming from a sportbike background but the same principles should apply.

Did mine like this.

Neil. :applause: :applause: :lol:

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Did you guys lower the front too so the overall geometry is closer to stock? Won't lowering the rear by the amounts you are talking about have a significant effect on the weight over the front wheel, front end feel, turn in speed and ability to hold a line in a corner. I am coming from a sportbike background but the same principles should apply.

My forks are going next week to be lowered and have the 'Ohlins' magic done. I will probaly be sending the shock too to have it shortened a bit more. Not knowing the linkage ratio made this a bit of "Hit or Miss". Since Daytona is about to happen, the suspension guy is off to the races and it will be a few weeks till he returns so I have a little time to figure out the details.

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Well, just got back from the first ride with the Ohlins on back. Night and friggin' day. Bumps that jar the front are invisible in the back. On/off gas movement is greatly reduced. Much of the 'wallows' are gone too. It falls into the corners, in fact I found myself pulling back up it wanted to turn so very much. Man O' man, am I dynin; over here wanting my forks done right this very moment. I do nto think I can stand waiting to have this done till the end of March.

I'll be sending the shock back to Thermosman (Mike Fitzgerald) to further shorten, probably another 19mm, to make the shock a total of 30mm shorter than OEM. That will end with the bike about 2.5" lower which is just right for my freakishly short legs. Funny, he wanted to shorten it 30mm but I told him not to. He should of talked me out of it. He must really believe the customer is always right.

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He must really believe the customer is always right.

I have spent a fair amount of time working in both Fishing tackle and Motorcycle shops.

We always used to say, "The Customer Is Always Right" but "Unfortunately The Customer Is Usually An Idiot".:cry:

Are you going to able to shorten the damper rod that much, without doing the same to the spring :applause:

Neil. :applause::lol::cry:

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I will be using a shorter, stiffer progressive fork spring and a shorter damper rod, if he cannot buy a rod the right length, he will make it. The guy doing the work has a stellar reputation as one of the best in the country. He set my rear shock exactly like I asked. Even the preload on it was spot on. LOL, now this idiot has to send the shock back to him to set the length to where he felt it should be based on my needs. He already has the spring on hand for the new length as he acquired it when he first put it together. My request to use a smaller spacer in the shock meant he had to get a longer spring, which he will take back.

Fortunately, UPS just visited and I got a bike lift. For once, both tires off the ground at the same time, stable, easy to deal with. Next week I'll pull the shock out, forks off and UPS them to him. My poor bike will be dangling for a few weeks. I hope it gets real cold and rainy every till the parts return.

I never said I knew a lot about suspensions. Turns out, I know just enough to look stupid!

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Don't feel bad Will, few of us know as much as we think we do, me included.

Usually we know enough to get out of trouble 99% of the time, the other 1%, well you just found it :cry:

And so did I, when I did my suspension, after lowering the forks to match the back, I then had to cut the spacers down, as I had gone to far.

I had underestimated the effect of the stiffer rear spring :cry:

Neil. :applause: :applause: :lol:

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LOL, actually, I do nto feel too bad. I knew I knew littel going into this particular project. Also, after having read so many posts on the linkage ratio's, with everyone being a bit vauge, I had a feeling dead on balls accuarcy was not going to happen. I know the ratio now, no dubts, if's and's or butt's! Anyway, after install, I need to have the remote preload adjust moved and you have to use a spring compressor to remove the spring. No ring nuts you can turn on this design.

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My poor bike will be dangling for a few weeks. I hope it gets real cold and rainy every till the parts return.

My DRZ has been in that state for over a month... and while it's been real cold and snowy it's still horrible. You did the opposite of what I did, but same effect. I should have done my own cams... would have been paranoidaly (Utah spelling) careful. Instead, thinking I'd screw it up... I let someone else screw it up.

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Well, I finally got my shock and the forks back from the suspension guy. I can touch with the balls of both of my feet! With the bike having been raised up in the air so long on the stand (about 1 foot off the ground) and now with the bike lowered, it looks funny, long and low. No chance to ride other than in the driveway as I did not get it together till late yesterday and my darned job actually wanted me to come in today (first time in six weeks!)

I have the forks at the OEM position (tubes raised about 1/4" at the line. I think I might try them flush, unless someone knows a reason I should not do that. None that I can think of.

Rear shock preload adjuster was moved to be right under the spring, almost no interference with the oil/air seperator. Had to tilt the little black box out from the frame maybe 1/4", basically insignificant. A few more tweaks and the suspension will be done.

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how short are your legs? I am thinking about getting a drz400s but worried it may be to tall for me. How much did both front and rear end up costing and how much travel do you have now? thanks

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how short are your legs? I am thinking about getting a drz400s but worried it may be to tall for me. How much did both front and rear end up costing and how much travel do you have now? thanks

I lowered close to 2", quite a bit but it should not be a issue now that the springs are correct for my weight and the fact the bike will be used on road 99%.

Cost is another issue. The Ohlins shock is a very pricey part, close to $800 for the shock, $200 for the adjuster add-on and was about $150.00 for the shortening. The total job cost was $1,150.00 The spring was free - whoopee. As functional as it is, it is also a bling bit, at least for me and my intended use.

I have not been billed for the frontend yet so no idea of the cost. A sm fork is quite different from an s fork. Call Racetech in your area for an estimate.

Could the same performance level of been achieved using the stock shock? Probably. The cost would of been like $200 (A guess). The preload adjuster is a real nice thing. Very easy to add about 15mm of preload.

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I don't know why I asked. I'm presently broke following the engine repairs/stroker, and my soon to be ex screwing me on the income tax this year.

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