Fork Mod Question

Lee Dodge

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I'm working on some fork modifications. (Cartridge emulators). I am wondering if anyone has had the forks apart and either has a picture of the damper rods or knows what size and how many compression damping holes are in the rods. I've searched a couple threads so far but haven't come up with anything.
 

Antarius

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If I recall, the stock damping rod has a single hole that is 3/16's in size. It may have been a tiny bit bigger, tiny. But basically, it was tiny and as soon as I saw it, it became abundantly clear why IMO there's no satisfactory option that doesnt involve drilling them out. You'd either have to go with such a thin oil that your rebound damping would essentially be non-existent, or you'd have a harsher ride than you would want. Just my $0.02 on that.

RaceTech calls for something like 6 or 9 3/8" holes if I recall correctly. I had a machine shop drill mine to RaceTech's spec, but the bottom line is RaceTech wants you to put as many holes in there as possible without limtiing the structure -- because they're trying to eliminate the damping rod all together.
 

Lee Dodge

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Thanks, that's the info I was looking for. Its kind of what I suspected based on a pic of the damper rod from a CTX700 I was able to find.
 

mike5100

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I can't help you with the number of holes required but I can complicate things slightly. I have just had racetech emulators fitted to the 2016 Showa DBV forks and the specialist said this valve is permanently fitted in the bottom of the fork stanchions. He said the only way to remove them would have been to grind them out. I think he said he wasn't sure how their continued presence will interact with the emulators, but when he'd finished the forks behaved as he expected them to behave so he was happy.
Mike
 

Antarius

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In the NC700x, at least in mine (a 2012 model), the damping rod comes out of the bottom. You have to remove the bottom bolt first, then dump the whole fork out and they'll come out. They are held in by the bolt, and spring tension, nothing else.

As far as how a damping rod will affect an emulator - I can explain that. Basically, it will severely hinder the ability of the emulator to do its job. Reason being, the damping rod with its tiny little hole is still preventing too much oil from flowing (thus making it harsh), and not allowing the emulator -- which has a valve stack -- to work as designed. The reason RaceTech and many others want you to drill out the damping rod so heavily is to essentially eliminate the damping rod from the equasion, as much as possible anyway, so the valve stack in the emulator can do its job.

A lot of people, and a lot of companies, get "around" this issue of drillign the damping rods by running a thinner oil. The idea being, a thinner oil can run through the hole faster anyway and get to the emulator / valve stack and then the valve stack can be tuned to do its job.

This is true, to a degree. The problem when you run an emulator is it really has no rebound damping valving. Emulators are really only good at controlling (accurately) compression damping (as in, how oil flows INTO it, not out of it -- like when your tire hits a bump). The rebound damping, or how fast your wheel gets pressed back INTO the ground (and internally, how the oil flows OUT of the valve), in an emulated fork is controlled by the weight of the oil more than anything else.

Why does this matter? If you run a really thin oil to get around the single tiny hole problem of the damping rod, you will have a very fast rebound -- or in other words -- very little rebound damping. You can definitely get some good compression damping out of the emulator setup, which will make the harshness when you HIT a bump reduced drastically, but you will still have a front wheel that is overly eager to get back down to the ground, which increases harshes on the back side of the bump.

All in all, as with most things in life, suspension is a compromise. A compromise of cost, what you need it to do, difficulty to complete the job and what the end result is capable of being. In some cases, stock forks are fine. In other people's cases, stock forks with an emulator is fine. In others, emulators with the damping rods drilled out are what they are happy with, and in some other cases people are not happy with any of that and go with a true cartridge fork.

I can go on and on about what's "correct" and "best," but that's just silly. Ultimately it's up to the rider to decide what sacrifice they want to make and what type of riding they're doing, and then they can decide the best course of action.

For me, RaceTech emulators with the damping rods drilled out was good "enough" for me on this bike. On other bikes, I do a lot more to get the suspension to do what I want. It just depends on the application.
 
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drstimpy

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I have emulators in some of my bikes and ddc in others. Blinded I wouldn't be able to tell the difference. As mentioned above they are a 90% solution but in my opinion a perfect solution for a 90% bike. They remove the most annoying problem with damper Rod forks which is way too much high speed compression dampening. It is very fatiguing to feel every tiny bump in the bars. DDC's are easier to install. Emulators are more tunable.


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Antarius

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I have emulators in some of my bikes and ddc in others. Blinded I wouldn't be able to tell the difference. As mentioned above they are a 90% solution but in my opinion a perfect solution for a 90% bike. They remove the most annoying problem with damper Rod forks which is way too much high speed compression dampening. It is very fatiguing to feel every tiny bump in the bars. DDC's are easier to install. Emulators are more tunable.


Sent from my iPad using Tapatalk
So very true.
 

mike5100

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In the NC700x, at least in mine (a 2012 model), the damping rod comes out of the bottom. You have to remove the bottom bolt first, then dump the whole fork out and they'll come out. They are held in by the bolt, and spring tension, nothing else.

As far as how a damping rod will affect an emulator - I can explain that. Basically, it will severely hinder the ability of the emulator to do its job. Reason being, the damping rod with its tiny little hole is still preventing too much oil from flowing (thus making it harsh), and not allowing the emulator -- which has a valve stack -- to work as designed. The reason RaceTech and many others want you to drill out the damping rod so heavily is to essentially eliminate the damping rod from the equasion, as much as possible anyway, so the valve stack in the emulator can do its job.

A lot of people, and a lot of companies, get "around" this issue of drillign the damping rods by running a thinner oil. The idea being, a thinner oil can run through the hole faster anyway and get to the emulator / valve stack and then the valve stack can be tuned to do its job.

This is true, to a degree. The problem when you run an emulator is it really has no rebound damping valving. Emulators are really only good at controlling (accurately) compression damping (as in, how oil flows INTO it, not out of it -- like when your tire hits a bump). The rebound damping, or how fast your wheel gets pressed back INTO the ground (and internally, how the oil flows OUT of the valve), in an emulated fork is controlled by the weight of the oil more than anything else.

Why does this matter? If you run a really thin oil to get around the single tiny hole problem of the damping rod, you will have a very fast rebound -- or in other words -- very little rebound damping. You can definitely get some good compression damping out of the emulator setup, which will make the harshness when you HIT a bump reduced drastically, but you will still have a front wheel that is overly eager to get back down to the ground, which increases harshes on the back side of the bump.

All in all, as with most things in life, suspension is a compromise. A compromise of cost, what you need it to do, difficulty to complete the job and what the end result is capable of being. In some cases, stock forks are fine. In other people's cases, stock forks with an emulator is fine. In others, emulators with the damping rods drilled out are what they are happy with, and in some other cases people are not happy with any of that and go with a true cartridge fork.

I can go on and on about what's "correct" and "best," but that's just silly. Ultimately it's up to the rider to decide what sacrifice they want to make and what type of riding they're doing, and then they can decide the best course of action.

For me, RaceTech emulators with the damping rods drilled out was good "enough" for me on this bike. On other bikes, I do a lot more to get the suspension to do what I want. It just depends on the application.
Antarius that's useful, but I think you may be misunderstanding the point I'm making above. My guy has indeed drilled the 2016 model's damping rod in accordance with Racetech's recommendations, but he couldn't remove the new Dual Bending Valve that is fitted to these new model forks. So if I am understanding you correctly the 6 big holes now drilled and the 15wt oil will deal with the problem of the excessive high speed compression damping whilst still providing reasonable rebound control, but the question is (I guess) what happens if the emulator and the dual bending valve both try to control the compression damping at the same time?
Mike
 

Antarius

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Mike,

From what I understand, the DBV is just a way to make a standard damping rod fork MORE like a cartridge fork, but still affordable.

As I'm not entirely certain how it works, I can't confidently say where the emulators will help or hurt.

I missed your DBV comment in your original post. Sorry bout that!
 

mike5100

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Mike,

From what I understand, the DBV is just a way to make a standard damping rod fork MORE like a cartridge fork, but still affordable.

As I'm not entirely certain how it works, I can't confidently say where the emulators will help or hurt.

I missed your DBV comment in your original post. Sorry bout that!
It's odd isn't it. Even two suspension specialists I spoke to didn't seem to know how it was meant to work. One of them even said that he thought it was all marketing hype, but he then did find 'something' in the base of the fork tube. He didn't say how he thought it worked (or not). But logically it must try to work like an emulator surely. By the sound of it they have a valve in there that 'bends' more when it gets a fast compression bump and less when it doesn't. If that is correct then it will be opening at the same time as the emulator is blowing off will it not?
Mike
 

Antarius

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It's odd isn't it. Even two suspension specialists I spoke to didn't seem to know how it was meant to work. One of them even said that he thought it was all marketing hype, but he then did find 'something' in the base of the fork tube. He didn't say how he thought it worked (or not). But logically it must try to work like an emulator surely. By the sound of it they have a valve in there that 'bends' more when it gets a fast compression bump and less when it doesn't. If that is correct then it will be opening at the same time as the emulator is blowing off will it not?
Mike
That's funny, it honestly sounded gimmicky to me when I read the specification also -- interesting the two guys you spoke to felt the same. That said, Showa does not (IMO) do R&D for gimmicky things and spend money on it, so I'm sure it does something.

If I had to GUESS, it does what you surmised. Or perhaps, it specifically gives a little bit of damping to the rebound stroke, since the damping rod fork won't. The fact that it "bends" sounds very much like what a cartridge stack, or stack in an emulator does... the little washers bend at certain rates and allow oil to flow at a given rate. Change the rate and you change the characteristic of the fork.

Logic would say that since the main downside of a damping rod fork is high speed compression and a lack of rebound damping, the DBV system would help at least one if not both of those. Otherwise, why would they build it?

**EDIT**

I found a .PDF from Showa explaining what the DBV does. It sounds like it was developed to create a low cost "cartridge like" damping curve, for compression damping. It does nothing for rebound. So, basically, it's a miniature version of an emulator. I'd hazard to guess it doesn't work as well as a true emulator either.

https://www.showa1.com/en/news/news_corporate/pdf/hotnews_20141104.pdf
 
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mike5100

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Yes - that's my thinking too. So the question remains - if the DBV is still in there and trying to do its thing, will it interfere with what the emulator is trying to do?
Mike
 

mike5100

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.... also - it seems that this DBV is welded into the bottom of the fork tube and is therefore non-serviceable. It seems an awful shame that Showa didn't make it a screw-in device then people may have been able to tune the valve itself - in particular for me if it had blown open earlier in a fast compression, the forks would probably have been ok for me.
I might be taking crap mind you as I'm just beginning to learn a bit about forks
Mike
 

Antarius

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I'd trust your suspension guy who actually saw the components with his own eyes -- if he says the emulator is still going to do it's job, I pretty much trust that it will.

I picture the damping rod being drilled out, the increased amount of oil rapidly overwhelming the "DBV" valve or whatever they call it, and the emulator still being there to finish doing what the damping and Showa's magical "DBV" couldn't.
 

mike5100

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I'd trust your suspension guy who actually saw the components with his own eyes -- if he says the emulator is still going to do it's job, I pretty much trust that it will.

I picture the damping rod being drilled out, the increased amount of oil rapidly overwhelming the "DBV" valve or whatever they call it, and the emulator still being there to finish doing what the damping and Showa's magical "DBV" couldn't.
Again - that's exactly how I was rationalising it. The words the specialist used to me though were along the lines 'I wasn't sure of how it would affect the emulator but the forks (with the emulators in) are behaving as I expected so it's ok'
Mike
 
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