R Racing-Modified Internal-Reservoir Ohlins

Discussion in 'Trials' started by motobene, Jun 7, 2017.

  1. motobene

    motobene Motoing for 46 years

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    Starting a stand-alone thread on this. There is a related thread with similar name here:

    http://advrider.com/index.php?threads/sherco-ohlins-prototype-shock.1207385/

    ...but the subject matter is different. Same brand of shock for Sherco application, but the subject matter here is increasing the travel and performance of the OEM Ohlins with internal gas reservoir.

    Randy Lewis of R Racing has a modified non-remote-reservoir OEM Ohlins shock on its way for testing and evaluation.

    The Ohlins shock for Sherco Factory models has been around many years. It's a solid, reliable shock that tends to be a bit harsh during break-in, then works fairly well thereafter.

    The modification push resulted from discussions we have had. While not the Randy's R Racing longer travel remote reservoir shock, I was hoping for a tweaked and improved version of the internal-reservoir shock, based on some of the same principles employed in the long-travel shock, which are:

    - Added negative travel
    - Added positive travel
    - Shim-stack tweaks (re valving)
    - Softer spring

    When I get the shock I will take pix and do direct comparison rides to report on here.

    If the modded shock proves out, one could improve on the Factory Ohlins without buying a whole new shock. While it may not work quite as well as the long travel R Racing shock with remote reservoir and compression adjuster, the modified shock could result in a noticeable improvement over the standard-issue Ohlins without having to buy a whole new shock.
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  2. motobene

    motobene Motoing for 46 years

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    The shock arrived and I spent hours gathering data and doing testing.

    The below photo shows the OEM Sherco Factory models Ohlins on the top and the Randy Lewis-modified version on the bottom.

    IMG_20170610_143839.jpg

    As you can see, the available shock travel is significantly greater on the modified shock.

    The body has not been modified. One of the three spacers was removed to lengthen the shock only 6mm, and the bump cushion was shortened to 25mm from 40mm. This resulted in roughly 20mm more shock travel before bump-cushion contact. That's a significant change!

    I tested using the 60 N/mm spring that came with the shock. To prevent oversteer, I had to back preload off to 0.040" (1mm), which resulted in 1.19" (30.2mm) of rear-end sag under the bike's own weight.

    The usual free sag should be around 3/4" (19mm). Given the 'negative' travel addition and longer travel, more free sag best. Randy's recommended free sag was 0.875" (22.2mm), but I found that caused the bike's pitch to be butt high, which caused oversteer at my weight, 180 pounds (82 kg). I had to add more free sag to compensate, to get the steering to settle down.

    With the stock 64/65 N/mm spring, I expect the spring preload for correct steering at my weight to be from 0.5 to 1.0mm.

    So how does the shock work on my 2017 Sherco Factory 250? Given the addition of negative travel and low-preload initial travel, ground following and traction are superior with the modified shock.

    The feel is more plush and deep (less bony), especially when landing off obstacles and jumps.

    I think performance is superior in every way except rear-end hops, which require a stronger impulse for lift and a slight change in timing. I got used to both, quickly.


    Rear axle travel is increased from about 5-1/2" (140mm) to over 7" (178mm).

    Randy changed the rebound damping slightly on this shock. We're not sure yet what the end-result damping specs will be, but this shock works well.

    The internal DeCarbon gas separator piston is retained, so the modification does not entail a conversion to a gas-emulsion-type shock. On the latest Sherco-Scorpa (I'm not sure about the airbox-in-front models), the shock only fits body-end down given the close proximity of the frame strut. Gas emulsion does not work unless the body is oriented up.

    The modification is tricky given the nitrogen gas separator piston has to be in a very specific position during reassembly.

    I REALLY like this setup! It reduces the somewhat bony feel of the OEM Ohlins.
    I plan to do this mod to both my 2017s... or get Randy to do it for me :-)
    #2
  3. motobene

    motobene Motoing for 46 years

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    Gosh I thought this post would generate more interest, but I think perhaps the technical language may sound like Mars Attacks! dialogue to the majority? Ack ack ack ack!

    Several rides into the modified shock I continue to be very impressed! Much more plush and yummy!

    Randy said he wants me to keep the shock for a few months to fiddle with the settings and compete on the bike. Very happy to!

    I'm so impressed with increasing the travel that I will modify two Sachs ZF shocks I have in a similar way. The Sachs ZF takes Ohlins 12mm ID shims and when the piston is flipped over the right way and the damping is fixed, the longstanding standard GasGas shock works better than a stock Ohlins shock, in my humble opinion. Now it can work even better.

    I wish I could test the longer GasGas shocks on my Sherco, but I can't, and I no longer own a GasGas. But KrAzYOSUcowboy does, and one of the two Sachs shocks is his. I'll ask him if he wishes his rebuilt in the longer-travel direction.

    This investigation is getting very interesting... to me, anyway:jive
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  4. Zuendapp

    Zuendapp Been here awhile

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    Being from a Offroad and vintage motocross back ground, I am amazed that not more trials riders have there suspension tailored to better suite them. You can not convince me that a 250 Lbs. rider doesn’t need stiffer springs?Or a lighter fly weight rider need softer setup.

    I have read in the past that it is technique and skill, Of course if you have been riding trials for 20 plus years you have the skill and technique. Unfortunately many newer people to trials do not or will not ever have the 20 plus years experience. This is when the suspension setup makes for a more enjoyable and safer ride.

    The other explanation is cost, don’t need the Reiger or Ohlins shock. Maybe so, playing tiddlywinks is cheaper than trials. I would rather ride trials motorcycles, even though tiddlywinks is challenging.

    I have been intrigued by “R” Racings modified longer travel shocks. I can’t wait to read more on the “R” Racing Ohlins Sherco shock evaluation.
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  5. DRZBRI

    DRZBRI Bumblebeetuna!

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    you can borrow my gas gas if you want. It needs a new base gasket anyway. lol
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  6. motobene

    motobene Motoing for 46 years

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    I re valved and added some travel to a Sachs ZF shock today. It's being delivered tomorrow. Hope the customer likes the changes!

    The Ohlins is far easier to disassemble and add travel to. The Sacks has no spacers that can be removed, and the bump cushion is shorter on the Sachs, so not much of it can be pared back.

    It was a little here and there with a the Sachs, via machining three parts and modifying the bump cushion. I was able to eke out a whole 10mm more shaft travel:raindance
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  7. motobene

    motobene Motoing for 46 years

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    Trials suspension is pretty good, and works for a wide range of riders. Custom work can help, but we don't have a culture that promotes spending money on suspension. That is both good and bad.
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  8. Vintage pro

    Vintage pro Adventurer

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    Chris , make sure you test the std. 65nm spring just to my point of spring being overly stiff. On the TRS shock I built , I ended up with a 55nm spring , almost identical valving with almost no clicks in on the compression adjuster.
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  9. jonnyc21

    jonnyc21 Trials Ninja

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    I am sure on the edge of my chair for the next installment... :thumb
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  10. motomofo

    motomofo Been here awhile

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    I agree with you, but to also support Zuendapp's point of view... how many people who ride trials pay attention to how much sag they have? Very, very few. And it does make a difference. This is the first thing that anyone in any other motorcycle discipline focuses on during setup, yet trials riders typically ignore it.
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  11. jonnyc21

    jonnyc21 Trials Ninja

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    Its interesting that we don't really have a culture that promotes spending on things like suspension and similar adjustments as often as other motorcycle sports. Yet if you look at some of the top riders like Bou or Adam you see they have custom setups for more than just suspension. Even Pat has a modified setup, though not nearly as much so as the world level riders, with stiffer settings in the rear for the big hits and a stiffer clutch etc.

    I am not saying we should be setting our bikes up like Bou, Adam, or Pat... however if we are willing to dive in just a little more than we typically do as a trials community I would think it would help in the end. And even better would be share what you fine like motobene so we all get to see what works and doesn't we all get better togeather. And it might also attract a few riders from other disciplines who see trials as a black box of it will make you better but how?

    I will stop my rambling and let the thread get back to what its intended for. :freaky
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  12. Bronco638

    Bronco638 Nobody Home

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    I would love to tinker with my suspension because I'm pretty sure it's not set-up correctly, for me. However, I can read about stuff all day long but until I touch it with my fingers, it doesn't really sink in. I truly appreciate Chris' efforts and the fact that he takes time to post but, in this case, I'm still in the "suspension changes = black magic" mind set. I wish it lived closer to SW Oklahoma.....
    #12
  13. lineaway

    lineaway Long timer

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    Funny a video was just added to the link section at the top of the start up page. It was from Ryan Young talking suspension. what a 7 times National Champion and Sherco importer and one of the best trials trainers in the country. Watch it and see. Not once did he mention a measurement for sag. Just that you need just a little bit. I have been riding trials since 1972 and this was the first year that I bought a stiffer spring for my rear suspension. Granted I still worked alot to make the sispension to work correctly. The funny thing is I have lost more than 30 lbs since I installed the spring. At this rate I will be putting the stock one back on soon.
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  14. motobene

    motobene Motoing for 46 years

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    I like the fact that we keep it simple and don't geek out too much.

    Regarding sag in the rear, a great simplification is to ignore loaded percentages entirely and simply measure how much the rear fender drops under the bike's own weight.

    If you are a lard butt, 5/8" will do. If a fly weight 7/8" will do. Interpolate in between. If you go with a stiffer rear spring you may need less preload to get the 'butt drop' needed to retain more neutral (less hyper) steering.

    My current modified shock is and exception to the butt drop rule, having 1.4" of drop even with the softer 60 N/mm spring. The added negative and positive travel require this exception to preserve more neutral steering, the same stable steering I had on this same bike with stock Ohlins was 3/4".

    I will continue to repeat and emphasize steering characteristics as very connected to sag and bike saggital-plane bike pitch. You'll seldom hear that emphasis elsewhere.
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  15. motobene

    motobene Motoing for 46 years

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    Rode for an hour again last night.

    The simple mods are continuing to be superior and very noticeably pleasurable!

    After a few more ride hours I'll swap back to the stock Ohlins for recalibration. I am 95% sure at this point that my reaction to the stock Ohlins will be negative.

    It's hard to describe, but the ground compliance and obstacle soaking capabilities of the modified shock are very noticeably improved. The rear end has a deeper feel that lacks harsh bottoming. I've engaged in a certain perverse joy at attacking the sea of large fixed rocks the ranch has so many of. My skid plate isn't liking when I make small errors in line selection or balk when a lifting and placing of the front wheel from one big rock to another gets scary, but I am having some great :ricky
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  16. Tomnz

    Tomnz n00b

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    I wonder if this modification could be done to the trp sherco shock? I currently run one of these in my Scorpa and while it is significantly better than the standard shock it could be better
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  17. jonnyc21

    jonnyc21 Trials Ninja

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    All this talk of the R Racing modified Ohlins makes me want to try one... But I think I will have to be happy with what I have for a bit... :deal
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  18. Norman Foley

    Norman Foley Devotee of the Husqvarna

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    At least break it in first!:getiton
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