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Hunger
Posted on Wednesday, October 16, 2019 - 02:36 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

I know it's a never ending topic but haven't got a definitive answer so far and I suspect I've done something wrong.

So recently I've serviced forks in my 2006 XB12X. I do have the upgraded springs - progressive and more than 5mm thick - that's how you recognize it they say - correct me if I'm wrong. I set up oil level at 113mm below the edge as per 2006 manual. With the spring back in the tube the oil level was exactly at the edge, almost spilling out. But since it wasn't actually spilling it didn't stop me from putting it together. The oil I used was 10W.

After the operation she rides OK but I feel some wobble in the front when hard cornering. Also the front is a bit too soft for my taste even though the dials are already beyond the 'optimal for your weight' setting.

In this post:

http://www.badweatherbikers.com/cgibin/discus/show .cgi?tpc=142838&post=1206859#POST1206859

the poster says oil level should be different for 2007 forks - are these the 'upgraded' forks? I'm not sure. Also there's a question on whether it should be 172mm or 192mm as stated in 2007 manual.

So my question is, did I set the oil level wrong? Since I have thicker springs maybe I should have set it to 192mm or 172mm? Or maybe I've used too light oil (10W)?

Thanks!
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Ourdee
Posted on Wednesday, October 16, 2019 - 05:46 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Did you tighten the pinch bolts on the fork that holds the axle?
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Hunger
Posted on Thursday, October 17, 2019 - 08:57 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Ourdee, yes of course.
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Pushr0d
Posted on Thursday, October 17, 2019 - 09:34 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Did you 'jounce' the front before you tightened the axle pinch bolts?
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Shoggin
Posted on Thursday, October 17, 2019 - 09:44 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

I don't know the answer to your specific questions, but too much oil will stiffen the forks, even shorten their travel. not soften them.

IIRC 7.5W is OE, so 10W is fine if you're a heavier/ faster rider.
I have even used 15w as a band-aid for too light a spring, but using "fork oil" is a must.

Hows your front tire look? Are you testing this on a track? Moving the adjustments past the weight recommendation is fine and what you need to do in order to tune it to your liking. If any of the adjustments are maxed out is when you need to change oil weight or spring rate.
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Mark_weiss
Posted on Thursday, October 17, 2019 - 04:23 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Oil height determines the amount of air space left in the fork, above the oil. A sort of secondary spring that generates force as the forks compress and pressurize the air. It is not a mm exact measurement unless you are racing in Grands Prix.

Cartridge forks do require that as oil is added the damper rod be moved through its stroke. If oil is simply added and the fork assembled, the cartridge could have been full of air and would make a significant difference in oil height once the air had been expelled into the fork tube.

What does "dials beyond optimal" mean? Each adjuster has very different effect on performance.
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Hunger
Posted on Friday, October 18, 2019 - 01:34 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)


quote:

What does "dials beyond optimal" mean? Each adjuster has very different effect on performance.




Means I already had to tighten preload a little more from recommended for my weight. While I expected forks with fresh oil would be stiffer from the start. Overall stiffness is similar to before changing oil.

I'm more worried about the oil level. I assume beyond springs there's no difference between '06 and '07 fork. I believe I have the '07 springs in my 2006. They are thicker than '06 therefore they take more volume therefore you have to pour less oil in the fork. That's my understanding. The 2006 manual says 113mm from the top, 2007 says 192mm. The difference is significant, it's 8cm so there must be a reason. I'd appreciate if someone could confirm or deny my theory. I've set it as per 2006 manual despite having '07 springs. If I made a mistake I'm going to take it apart and correct.

Please also tell me if this actually looks like 2007 spring.

I'd be grateful for advice!





(Message edited by hunger on October 18, 2019)
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Mark_weiss
Posted on Friday, October 18, 2019 - 08:45 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

If the '07 spring has a higher rate the forks will not require as much air-spring, hence the larger air volume allowed.

If the old oil was not terribly old or contaminated its viscosity probably did not change much, that is why the new, clean, oil is yielding similar feel.

Pre-load is partially a personal preference matter. If you are setting preload only a bit higher than called for in the table that would not be too unusual. A LOT higher would be cause for investigation. Since the Uly has more fork travel than standard it is expected that there would be more braking dive than with shorter travel suspension. If you want less movement you can add oil and reduce the air space. This change will not alter damping, but will cause the effective fork spring rate to increase more rapidly as the suspension nears full compression. It is a matter of choice.
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