Mechanics Quick Question Thread [Ask Questions Here]

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Mechanics Quick Question Thread [Ask Questions Here]
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flag R-M-R
Posted: Dec 18, 2019 at 10:16 Quote
freestyIAM wrote:
[ ... ] PVD is a saint. Doing the Lord's work with his standardized viscosity measurement table.

He has a lot of great articles on a variety of topics. Even when I don't fully agree with an article, there's plenty of good information and interesting perspectives gained from experimentation, rather than speculation. It's quality stuff.


iffy wrote:
poor mans tuning with thinner oil is unlikely to do much

This isn't poor man's tuning, it's tuning. Scaling the damping in proportion to the rider's weight is exactly what should be done. The only reason damper changes aren't standard practice is because they take more effort than connecting a shock pump, but it's as fundamental as setting the spring rate.

Some bike companies spec different shock tunes for different frame sizes or genders (ex. Juliana vs. Santa Cruz); the main reason they rely on internal parts, rather than fluids, is because substituting a washer or spring during assembly is a lot easier than having multiple submersion baths or vacuum bleed machines filled with different fluids.
flag iffy
Posted: Dec 18, 2019 at 10:36 Quote
lower viscosity oil is unikely to do much at the end of travel and do a lot for everything else possibly reducing performance for the majority of the travel.
flag R-M-R
Posted: Dec 18, 2019 at 11:18 Quote
iffy wrote:
lower viscosity oil is unikely to do much at the end of travel and do a lot for everything else possibly reducing performance for the majority of the travel.

So you're saying a light rider who can't access full travel clearly has the right damper set-up and should continue to use the same set-up as heavier riders?
flag jamesashton
Posted: Dec 18, 2019 at 11:21 Quote
question - on a 160mm sr suntour fork, been rode hard for 2 years, pumped up to the pressure to my weight, and only about 130mm of travel are there, when no weight is on it. I can put my hand on the arch thing, and pull up on the crown, and all 160mm comes out, but then it gets sucked back down.. any ideas?
flag ajax-ripper
Posted: Dec 18, 2019 at 11:27 Quote
traqs wrote:
question - on a 160mm sr suntour fork, been rode hard for 2 years, pumped up to the pressure to my weight, and only about 130mm of travel are there, when no weight is on it. I can put my hand on the arch thing, and pull up on the crown, and all 160mm comes out, but then it gets sucked back down.. any ideas?

Not using every mm of travel is not a problem. Set you pressures so that you get good traction and ride characteristics and leave it, if you rarely use the last 25-30mm it is not a big deal.
flag R-M-R
Posted: Dec 18, 2019 at 11:36 Quote
ajax-ripper wrote:
Not using every mm of travel is not a problem. Set you pressures so that you get good traction and ride characteristics and leave it, if you rarely use the last 25-30mm it is not a big deal.

I think he's saying the fork doesn't fully extend. It's normal for there to be a little "extra" travel at full extension due to a top-out bumper, but 30 mm isn't normal.
flag jamesashton
Posted: Dec 18, 2019 at 11:57 Quote
yes, that is correct, RMR, it does not extend fully. I know all about how to use the right amount of travel and whatnot, but it does not extend, which I cannot figure out
flag ajax-ripper
Posted: Dec 18, 2019 at 11:57 Quote
R-M-R wrote:
ajax-ripper wrote:
Not using every mm of travel is not a problem. Set you pressures so that you get good traction and ride characteristics and leave it, if you rarely use the last 25-30mm it is not a big deal.

I think he's saying the fork doesn't fully extend. It's normal for there to be a little "extra" travel at full extension due to a top-out bumper, but 30 mm isn't normal.
copy misread. my apologies.
flag iffy
Posted: Dec 18, 2019 at 13:22 Quote
R-M-R wrote:
iffy wrote:
lower viscosity oil is unikely to do much at the end of travel and do a lot for everything else possibly reducing performance for the majority of the travel.

So you're saying a light rider who can't access full travel clearly has the right damper set-up and should continue to use the same set-up as heavier riders?

no.

read my post again. you are just being akward.
flag erdinc
Posted: Dec 18, 2019 at 14:13 Quote
Hi! Recently i bought a commencal clash frame. And i bought a shock from bike24. İt didn't came like on the site photo. it came with transition bearing hardware. İ still dont received the frame. Will this fit? 28mm wide. İcan change the bearings for bolt size.


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flag freestyIAM
Posted: Dec 18, 2019 at 14:20 Quote
iffy wrote:
R-M-R wrote:
iffy wrote:
lower viscosity oil is unikely to do much at the end of travel and do a lot for everything else possibly reducing performance for the majority of the travel.

So you're saying a light rider who can't access full travel clearly has the right damper set-up and should continue to use the same set-up as heavier riders?

no.

read my post again. you are just being akward.

Its not self evident to me what your argument is even on rereading your post. I don't understand how a lower viscosity oil is A) unlikely to do much at the end of travel and B) will do a lot of everything else possible reducing performance for the majority of the travel. Please explain

IMO, the lower viscosity oil will flow faster past the shim stack that controls HSC thereby reducing the HSC damping and potentially allowing for fuller use of travel on big hits. It will also flow faster past the orifices that control LSC but you can adjust for that by turning the LSC dial to the right and constricting the orifices.

What am I missing?
flag freestyIAM
Posted: Dec 18, 2019 at 14:32 Quote
Noeserd wrote:
Hi! Recently i bought a commencal clash frame. And i bought a shock from bike24. İt didn't came like on the site photo. it came with transition bearing hardware. İ still dont received the frame. Will this fit? 28mm wide. İcan change the bearings for bolt size.


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First, the bearing version of the shock appears wider than the bushing version. Second, I think its going to depend on the clash's shock mounting spacing. A lot of times the shock mounting spacing is wider than the shock's mount and you'll use reducers to make up the extra space. If extra space > extra shock mount width, then you should be able to make this work with smaller (or no) reducers. If not, i think you're F&*ked.
flag freestyIAM
Posted: Dec 18, 2019 at 15:51 Quote
ajax-ripper wrote:
R-M-R wrote:
ajax-ripper wrote:
Not using every mm of travel is not a problem. Set you pressures so that you get good traction and ride characteristics and leave it, if you rarely use the last 25-30mm it is not a big deal.

I think he's saying the fork doesn't fully extend. It's normal for there to be a little "extra" travel at full extension due to a top-out bumper, but 30 mm isn't normal.
copy misread. my apologies.

sounds to me like you need to burp your fork lowers.

https://www.youtube.com/watch?v=EJuD2Vj2mQM

In your case you could have a vacuum behind the wiper seals rather than too much air trapped behind the wiper seals, and instead of keeping you from using full travel, its keeping your fork from full extension.
flag jamesashton
Posted: Dec 18, 2019 at 17:07 Quote
might be it, ill give it a try tomorrow, thank you
flag ajax-ripper
Posted: Dec 18, 2019 at 19:38 Quote
freestyIAM wrote:
ajax-ripper wrote:
R-M-R wrote:


I think he's saying the fork doesn't fully extend. It's normal for there to be a little "extra" travel at full extension due to a top-out bumper, but 30 mm isn't normal.
copy misread. my apologies.

sounds to me like you need to burp your fork lowers.

https://www.youtube.com/watch?v=EJuD2Vj2mQM

In your case you could have a vacuum behind the wiper seals rather than too much air trapped behind the wiper seals, and instead of keeping you from using full travel, its keeping your fork from full extension.
It's more likely that he has excess air trapped in the negative chamber. Best action would be to rebuild the air spring.

 


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