Author Topic: harsh std suspension  (Read 9973 times)

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Offline motorboy

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Re: harsh std suspension
Reply #80 on: January 23, 2021, 03:22:27 PM
*Originally Posted by phattanglo [+]
So I rode my bike for the first time this morning since the fork rebuild and it is definitely better but I feel it needs tweaking as it is a little too firm on the compression damping.
When I installed the PD valves I left them on the factory tension as instructed and used 15w oil and also drilled the damper rod holes out to 8mm as suggested.
What I'm finding is the rebound damping with the 15 oil feels to be good as pressing on the forks and releasing gives a fairly quick rebound but with no bounce so good control I think.
Compression also seems to be well controlled but actually on the road it is a bit too stiff and while it isn't as bone jarring as before it could use a little adjustment.
My question is if the oil weight seems to suit the rebound damping, is it ok to wind off the pd valve spring tension a little and if so how much adjustability do I have.
If this is not possible and I have to use a lighter oil, how low can I go without adversely affecting the rebound damping too much.
PS I've re-measured my sag and it's actually nearly 30mm so I'm happy to leave it alone and see how it goes.
Was the 15w the oil the company recommended
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Offline phattanglo

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Re: harsh std suspension
Reply #81 on: January 23, 2021, 03:36:30 PM
Yes Brook suspension and the Racetech database suggested 15w as YSS themselves recommended 20 weight which would have made the ride harsher still.
It seems the valves can be loosened to no turns so I'll try that and if no joy I'll have to reduce the oil weight.

Offline motorboy

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Re: harsh std suspension
Reply #82 on: January 23, 2021, 04:03:29 PM
*Originally Posted by phattanglo [+]
Yes Brook suspension and the Racetech database suggested 15w as YSS themselves recommended 20 weight which would have made the ride harsher still.
It seems the valves can be loosened to no turns so I'll try that and if no joy I'll have to reduce the oil weight.
If it was me I would Contact Brook first and get their opinion
Last Edit: January 23, 2021, 04:04:02 PM by motorboy
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Offline phattanglo

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Re: harsh std suspension
Reply #83 on: January 23, 2021, 06:17:32 PM
I've messaged Firefox racing who I bought the PD valves from, hopefully they'll be able to help.
It seem odd that the valve range goes from 0 to 7 full turns in and the factory setting is 2 turns in and I'm using lighter oil than YSS suggest.
I've definitely got the correct fork spring rate for my weight and the static and rider sag are pretty much within range.
I enlarged and de-burred the damper rod compression holes to 8mm as advised by Oyabun and I know the PD valves are seated correctly as the were supplied with alloy adaptors that were a perfect fit.
The only thing I can think of is the valve spring tension so I'll wait for Firefox to get back to me.
Possibly I was expecting a bigger improvement than the forks are capable of but other users reports suggested it was a very effective mod.
Last Edit: January 23, 2021, 06:21:29 PM by phattanglo

Offline motorboy

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Re: harsh std suspension
Reply #84 on: January 23, 2021, 09:58:42 PM
*Originally Posted by phattanglo [+]
I've messaged Firefox racing who I bought the PD valves from, hopefully they'll be able to help.
It seem odd that the valve range goes from 0 to 7 full turns in and the factory setting is 2 turns in and I'm using lighter oil than YSS suggest.
I've definitely got the correct fork spring rate for my weight and the static and rider sag are pretty much within range.
I enlarged and de-burred the damper rod compression holes to 8mm as advised by Oyabun and I know the PD valves are seated correctly as the were supplied with alloy adaptors that were a perfect fit.
The only thing I can think of is the valve spring tension so I'll wait for Firefox to get back to me.
Possibly I was expecting a bigger improvement than the forks are capable of but other users reports suggested it was a very effective mod.
As far as the valves go I'm sure they are used on several different bikes  with 41mm forks and different spring rate -did the company give you any direction on opening the damper rods
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Offline phattanglo

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Re: harsh std suspension
Reply #85 on: January 23, 2021, 10:17:14 PM
No I've just gone with the consensus that suggests opening out the original holes to 8mm.
I suppose I could take the valves back out, I'd soon know if the holes were opened enough when I was pogo-ing down the road 😁

Offline motorboy

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Re: harsh std suspension
Reply #86 on: January 23, 2021, 10:27:13 PM
*Originally Posted by phattanglo [+]
No I've just gone with the consensus that suggests opening out the original holes to 8mm.
I suppose I could take the valves back out, I'd soon know if the holes were opened enough when I was pogo-ing down the road 😁
I still think your best course of action is to contact the company tell them how you have it set up-and what do they suggest- I would think if they wanted the damper rods opened they would have said so and told you how much
Last Edit: January 23, 2021, 10:29:52 PM by motorboy
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Offline Oyabun

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Re: harsh std suspension
Reply #87 on: January 24, 2021, 12:19:30 AM
*Originally Posted by motorboy [+]
I still think your best course of action is to contact the company tell them how you have it set up-and what do they suggest- I would think if they wanted the damper rods opened they would have said so and told you how much
@motorboy If you read back, phattanglo complains to have too much compression damping. What is meaning a restriction of flow - quite opposite what I read from you seem to imply. So no, it is not a problem that he had opened up those compression holes.
@phattanglo
As you've seen there is a huge difference in size between the compression and rebound holes, so the change in damping if you're going to go down a grade or half in fluid viscosity is proportional.
But before you'd do so, please describe me what do you feel when you talk about too stiff compression damping? When is it stiff? During braking or cornering? Is it too much, when you hit sharp edges at speed? Is it slowing down when you're at the end of the stroke? Please describe it better what you feel.
As an additional note. Not all fluids are the same. Meaning while "weight" of 5-10-15w give kind of an indication their true characteristics is given by their cst (or centistoke) values at given temperatures - typically at 40 and 100degC.
You can find an example of collected data here:
http://www.jackscycles.com/files/Suspension_Fluids.pdf
What brings us to the point. They have different real word viscosity meaning a lot depend on your brand might be thicker than others. And also working temperature makes a difference. Most of the northern hemisphere is in winter-ish period now, meaning colder temps, making things a bit more dampened. On the other hand YSS being on the tropics suggesting to use a grade heavier fluid than others. I see a bit of tendency here, what about you? ;-)
But to conclude depending on where and what is what you'd like to change, you've got four points to change. Spring preload on the valve, fluid viscosity, size of compression orifices on the rod and size of the bleed circuit orifice on the valve.
All do a bit different.
- Fluid changes all three damping modes hi and lo comp, and rebound.
- Spring preload changes crossover from lo to hi speed compression, but, doesn't change the amount of compression you get.
- Compression holes on the rod alter the high speed compression amount separately from low speed
- bleed orifice only change the amount of low speed compression.
What I'd suggest first, is to understand your suspension better. If you think that both hi and lo speed compression is too stiff, change the fluid in one fork leg to 10w and keep the other at 15 to see if you're going to the right direction. One can also use different grade fork fluids from the same manufacturer to mix proportionally and come up with intermediate viscosities. e.g. mixing equal amounts of 10w and 15w fluid will result in roughly 12.5w. But you're perfectly fine also having different kind of fluids in different legs. Many people would frown about it, but actually many bikes come from the factory with one fork leg doing springs and the other damping - or more recently one fork cartridge controlling compression and the other one rebound - so you'll be perfectly fine with it. Also as the weather gets warmer, and the suspension does it work and the fluid will be warmer it will definitely loosen up.
Also I'd buy a pair of reasonably priced preload adjusters from ebay, and set a bit more sag. Now as you have a stiffer spring, you don't need that much preload at all to keep you in the stroke - and as you have seen having a bit much preload has an effect of the spring starts to work later giving it a bit of a harsh feeling. If you're stayed with the original 140mm length damper rods, 40mm sag instead of 30 would be closer to ideal.
Suspension setting is an individual preference, there are no two racers who would run the same setup despite riding the same spec bike and being the same weight. Hope this helps to tune the suspension to your preference. No generic suspension part manufacturer will do the final setup for you. Even top dollar Racetech will give a range of options to choose your final setup from.
Last Edit: January 24, 2021, 12:27:09 AM by Oyabun

Offline motorboy

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Re: harsh std suspension
Reply #88 on: January 24, 2021, 02:06:25 AM
I have followed the thread-what I'm still saying is the manufacturer of the product should know more than anyone on how to set it up and phattanglo should follow there lead first lets wait and see what they say
Last Edit: January 24, 2021, 02:09:59 AM by motorboy
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Offline phattanglo

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Re: harsh std suspension
Reply #89 on: January 24, 2021, 12:30:19 PM
Hi Oyabun, yes that all makes sense and yes you interpreted my question exactly. My feeling is that the compression is a little stiff but primarily on fast compression, slow compression feels great, well controlled with no excessive dive when braking and has definitely improved the front end handling.
I take your point about increasing the sag and using a preload adjuster which I will make my next job.
What I propose to do is actually leave things as they are until the new shock is fitted and review the situation as I expect the improved sag and damping at the rear will have some influence on the front and I don't want to alter too many things simultaneously and get myself confused, well no more than usual :001:
I'll also put on a tie wrap and see how much travel I'm actually using on a ride.
Last Edit: January 24, 2021, 12:46:22 PM by phattanglo

 



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