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Ohlins fork question

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Prsv View Drop Down
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    Posted: 14 Feb 2016 at 19:49
Serviced my factory ohlins today spacer off spring still in took oil level before draining 100 mm. flushed with parafin let them drain for a good hour, put 500 cc oil in each leg and only had 130 mm level spring in fully compressed damper rod down. Manual states 500 cc should give 85 mm, added 50 cc approx went for 95 mm level.

Am I missing something or does that sound about right.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Spoonz Quote  Post ReplyReply Direct Link To This Post Posted: 14 Feb 2016 at 20:04
Originally posted by Prsv Prsv wrote:

Serviced my factory ohlins today spacer off spring still in took oil level before draining 100 mm. flushed with parafin let them drain for a good hour, put 500 cc oil in each leg and only had 130 mm level spring in fully compressed damper rod down. Manual states 500 cc should give 85 mm, added 50 cc approx went for 95 mm level.

Am I missing something or does that sound about right.
Always go by the level not the amount. The damper rod should be raised when measuring as that is it's natural position when the fork is assembled, if it's lowered it will add to the mass in the oil bath which will then drop when you assemble the fork and rod is raised.  You will need to pump the rod (slowly) before measuring to evacuate the air in the cartridge.
 
Last time I did ohlins I used more than 500cc in each leg so I wouldn't read too much into the amount as long as it's not hugely wrong.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Prsv Quote  Post ReplyReply Direct Link To This Post Posted: 14 Feb 2016 at 20:17
Ahh didn't know damper rod had to be up taking displacement into account probably would of been nearer 100 mm then. Have you ever replaced bushes inside fork had fair bit of play on one.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Spoonz Quote  Post ReplyReply Direct Link To This Post Posted: 14 Feb 2016 at 20:24
Originally posted by Prsv Prsv wrote:

Ahh didn't know damper rod had to be up taking displacement into account probably would of been nearer 85 mm then. Have you ever replaced bushes inside fork had fair bit of play on one.
 
I replaced the lower bushes on mine once as I could feel a knocking in one leg but it turned out not to be the bushes in the end. The lower ones are fairly easy as access is pretty good.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Prsv Quote  Post ReplyReply Direct Link To This Post Posted: 14 Feb 2016 at 20:45
What was the knocking, I could hear play thought it was coming from top bush when moving fork bottom and holding tube. Put magnetic dial gauge on had 0.08 mm play, when stripped bushes looked good no wear marks put it down to oil clearance.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Spoonz Quote  Post ReplyReply Direct Link To This Post Posted: 14 Feb 2016 at 20:52
It was coming from the top cap which was incorrectly shimmed from the factory.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Prsv Quote  Post ReplyReply Direct Link To This Post Posted: 15 Feb 2016 at 13:20
So what air gap is a good base setting in ohlins then. The springs
had 2 marks lines on face of springs no other markings 242 mm long thinking they are not standard or is that how ohlins marks them.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Spoonz Quote  Post ReplyReply Direct Link To This Post Posted: 15 Feb 2016 at 16:01
Depends on the individual really. The smaller the air gap the faster the damping rate ramps up as the fork compresses. If you have too much oil the damping ramps up way to early and will over ride your compression damping way before the end of travel, too little and the forks won't ramp up enough and will bottom.
 
Getting that happy medium depends on your weight and riding style and the oil thickness. Best just to experiment and find a best setting. for me I found the oem air gap of 85mm meant I couldn't get anywhere near full travel even with minimal compression damping.
 
If I'm honest I prefer the radial showa forks to the Ohlins from a road use point of view. The Ohlins are a bit more track focused and a bit harsh on the road for me as they come from the factory.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote m9rko Quote  Post ReplyReply Direct Link To This Post Posted: 15 Feb 2016 at 17:37
I serviced mine recently and went for 85mm gap (everything installed except top washer, damper rod all the way in). I was told by some reputable people that this was a good base setting Smile I used just over 500ml in each fork leg.
www.apriliaperformance.co.uk
www.apriliaforum.co.uk
www.apriliaownersclub.co.uk
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Prsv Quote  Post ReplyReply Direct Link To This Post Posted: 15 Feb 2016 at 17:51
like you found them harsh on the road but working well, nearly full travel on a good ride. Had smear of oil from one leg mot due so changed seals went for 5wt oil didn't want damping any stiffer and kept air gap same less 5mm allowing for any oil lost. Do you think springs are OE like said, have 2 edge of file marks on machined face of spring ?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote m9rko Quote  Post ReplyReply Direct Link To This Post Posted: 15 Feb 2016 at 18:00
After a quick search it looks like 2 etched marks means they are standard in a later gen 1 radial bike, and are 10.0 N/mm spring rate
www.apriliaperformance.co.uk
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Prsv Quote  Post ReplyReply Direct Link To This Post Posted: 15 Feb 2016 at 18:02
M9rko did you take air gap before draining mine being 100mm  went in the midle ish 95mm manual sates 85mm. as spoons says if not getting nearly full travel go with more air gap.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Spoonz Quote  Post ReplyReply Direct Link To This Post Posted: 15 Feb 2016 at 19:14
M9arko would have had about 90mm air gap if the rod was down. It raises the oil level when in the bath which would have dropped again once it was raised and attached to the cap.
 
I went with 5wt oil also. Even with an increased air gap and lighter oil they still never got close to bottoming but were less harsh on big hits. Had I still got ohlins I think I would have experimented with shimming or a lighter bypass spring for the real big hits..
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Prsv Quote  Post ReplyReply Direct Link To This Post Posted: 15 Feb 2016 at 19:36
m9rko they are gen 2 factory radial forks so should be standard then thanks.

spoons thanks for the knowledge your a credit to this forum.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote m9rko Quote  Post ReplyReply Direct Link To This Post Posted: 15 Feb 2016 at 21:56
If there's 2 etched line's I don't think they are standard springs.. This is stolen from another forum (amauri on AF1)

"The first generation Ohlins/Aprilia radial fork # FG8900 & 8901 came with .95 N/mm springs.
Somewhere late in 2004 or early 05 they updated to the FG8902 and later 8903, those later forks came with 1.0 springs, upgraded seals and a small change in the compression shim stack

If you remove the original fork spring and look at the ends, you should see some markings.

Aprilia, Ducati and other OEM Ohlins fork springs do not have any numbered markings. They are marked instead with a hand etched line or lines.

The .95 OEM springs are not marked at all (2003 – 2004).
The 1.0 OEM springs are marked with one line (2004 – 2009).
The 1.05 OEM springs (RSV4) are marked with two engraved lines.

Springs you buy from Ohlins will have a numeric laser etching designating the type and rate."

Hope that helps


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Post Options Post Options   Thanks (0) Thanks(0)   Quote Spoonz Quote  Post ReplyReply Direct Link To This Post Posted: 16 Feb 2016 at 10:13
As a aid to understanding the air gap effect on damping, this is from the Ohlins manual showing the effect of oil height on the rising rate of the damping. The chart only shows a small range but the rise is fairly linear for each 10mm reduction in air gap so you can approx work out where the rate would be at 85mm air gap. It does highlight how quickly in your travel that your compression can be determined by your air gap than the compression valving in your fork.
 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Golightly Quote  Post ReplyReply Direct Link To This Post Posted: 25 Jul 2016 at 17:51
does the 85mm air gap apply to gen 1 non radial Ohlins please?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Spoonz Quote  Post ReplyReply Direct Link To This Post Posted: 25 Jul 2016 at 17:56
If you want the stock setting yes.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote philmille Quote  Post ReplyReply Direct Link To This Post Posted: 09 Aug 2016 at 23:15
I had mine serviced by the firm in Stowmarket 2 years ago, and now one the the seals has a leak, tried the Sealmate tool, but that hasn't helped. Any ideas? how come they keep going????

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Spoonz Quote  Post ReplyReply Direct Link To This Post Posted: 10 Aug 2016 at 08:56
Originally posted by philmille philmille wrote:

I had mine serviced by the firm in Stowmarket 2 years ago, and now one the the seals has a leak, tried the Sealmate tool, but that hasn't helped. Any ideas? how come they keep going????

 
They may not have used the newer multi lipped seals or there may be mark from a stone chip that damages the seal.

Ohlins seals also don't like being dry, they harden or stick to the stanchion. If the bike is parked up for any length of time, bounce the front suspension as it coats the inner lips with a thin oil film when you do that.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote BOL D'OR Quote  Post ReplyReply Direct Link To This Post Posted: 10 Aug 2016 at 09:47
I recently had my Ohlins serviced by MH racing.
Not cheap when you factor in postage/packing from Aberdeen + insurance in case they get lost/damaged.
 
I wish I'd asked him if he uses these newer multi-lipped seals. Cry
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Post Options Post Options   Thanks (0) Thanks(0)   Quote philmille Quote  Post ReplyReply Direct Link To This Post Posted: 23 Aug 2016 at 22:12
Cheers Spoonz, going to get the seals replaced by the same firm, MCT, then make sure they don't dry out.... 
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