Problems setting front sag, 2012 675R - Triumph675.Net Forums
 
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post #1 of 6 Old 11-02-17, 16:04 Thread Starter
Wiggie
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Problems setting front sag, 2012 675R

I finally turned my attention to setting up the suspension on my 2012 675R in anticipation of a couple of track days at Barber in November--which will be as far as I know the first time this bike has been on a track. I had previously adopted the settings recommended in the Sportsrider.com database, then switched to the "comfort" settings because I was mostly riding around town with some local highway riding--where it can be rather bumpy. (The difference by the way was staggering--as you might expect from a quality suspension like Ohlins).

But what I had never done was set up rider static sag properly. Rear sag I now have at 30mm, which is in the range I want (about 7 mm of threads showing above the locking ring on the shock). However I cannot get the front sag on the Ohlins NIX 30 forks to be less than 36-37mm even with full preload dialed in. I was trying to target 30mm but can't get there. When riding over bumps and some hard braking I am NOT using up all the travel--still have about 25mm available. From this my naive conclusion is that the fork springs are too soft--or perhaps that the oil viscosity or level is not correct. Correct me if I am wrong but I thought I read somewhere that too little oil (too much air) would manifest itself at the extreme end of the forks' travel--leading to bottoming out of the suspension. This is not happening.

Another possible clue is that the "free sag"--that is the sag from fully extended with no rider aboard--also seems to be excessive. I measured 27mm front, and 13mm rear, whereas my reference material suggested this should be 5-10mm front, and 0-5mm rear.

I realize its about time to replace the fork oil, at which time I will try to figure out if the springs are appropriate for my weight. But in the meantime could one of you more experienced riders/mechanics/suspension tuners comment on whether my thinking is in the right direction? I hate to invest in new springs only to hear from someone more experienced "don't worry mate they are all like that" or something similar.

Background:
Purchased bike used with ~8,000 miles. It had had a very easy life prior to coming to me. I weigh 160 lbs/73 kg, about 175 lbs max with gear on. I don't know this for sure but I suspect that the forks have never been out, and the original OEM spring and oil are probably all still in there. So being a fairly light weight guy, I am surprised that the OEM spring would be too weak for me. By the way after much vacillation, I did my sag set up with a full tank of gas (as well as my riding gear on--nowhere could I find any recommendation on whether to set the suspension up with a full tank, half full tank or empty tank which is surprising since this could make a 30 lbs difference to the bike's weight.

Many thanks for any advice. And my apologies if this has been discussed ad infinitum (ad nauseam?) previously.

2009 Daytona 675; 2008 Sprint ST 1050; 2007 Aprilia RSV1000R Factory
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post #2 of 6 Old 11-02-17, 17:03
MGFChapin
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Oil viscosity wouldn't affect sag. Any possibility the previous owner changed springs? I weigh the same as you and the stock springs are perfect for me.
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post #3 of 6 Old 11-02-17, 17:15 Thread Starter
Wiggie
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Anything is possible--the bike has had two previous owners. I am pretty sure owner#2 didn't change it, he seemed kind of--well, ahem, clueless--but I have no way of reaching owner #1.

I will be interested to find out what is actually in there. Hard to believe its the stock spring based on what I am finding.

2009 Daytona 675; 2008 Sprint ST 1050; 2007 Aprilia RSV1000R Factory
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post #4 of 6 Old 11-02-17, 19:13
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Quote:
Originally Posted by Wiggie View Post
Anything is possible--the bike has had two previous owners. I am pretty sure owner#2 didn't change it, he seemed kind of--well, ahem, clueless--but I have no way of reaching owner #1.

I will be interested to find out what is actually in there. Hard to believe its the stock spring based on what I am finding.

Whether it was ever changed or not, you need heavier springs.

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post #5 of 6 Old 11-02-17, 19:36
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Quote:
Originally Posted by Cloner View Post
Whether it was ever changed or not, you need heavier springs.
Yeah, maybe. I have a hunch the preload adjuster somehow isn't working right if he can't get less than 36-37 mm. You'll have to take your forks apart regardless, OP. Take the cap off and see if the blue preload collar spins up or down when you turn the preload nut on the cap. Maybe the threads came disengaged or something.
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post #6 of 6 Old 11-03-17, 11:14
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It doesn't seem right to me either. I would also check to make sure the preload adjusters are actually working.

As I asked in the other thread about front sag, how are you measuring the sag numbers and what part of the bike are you using as a reference?
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