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Offline JohnCW

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Re: Fully adjustable Wilbers shock.
Reply #20 on: July 12, 2019, 08:45:25 AM
*Originally Posted by RobZ900 [+]

For me, just the shock as it is will be fine. Ive got no use for height adjustment, riser kits or hydraulic preload adjusters. I just want the adjustability for rebound, low and high speed comp and preload, all in a smart looking shock and the standard 641 ticks those boxes for the right price.

What bike are you running twin piggybacks on?

Bike is a Kawasaki zr750.  The D1 model with the wire wheels.  With correct jetting (they are stupidly lean standard) and upgrades to both front and rear suspension the old buggers go surprisingly well.  I've had guys on the new RS chase me and they are quite surprised they can't ride away from me as they expect.

The reason I bought a set of Nitron's when the Wilbers were due for rebuild was because I could never get them just how I wanted.  However the Nitons proved to be even more difficult to set up (and even just to physically adjust) than the Wilbers.  However ironically all that stuffing around with the Nitrons proved to actually be invaluable, because when I finally gave up on the Nitrons and refitted the Wilbers (rebuilt) and adjusted them with the new found knowledge from trying to get the Nirons to work, great results.

The mistake I was making, and I'm sure I'm not alone in doing this, so hence the reason for outlining it as it may prove useful to others was ...... 

(a) you need the suspension to be 'loose' to corner well.  Sure a lot of rebound and/or slow speed compression will make the bike feel 'tight' and controlled in a straight line.  But a lot more effort is required to muscle it around corners.  The old saying 'less is more' when it comes to damping adjustment is spot on.

(b) So you need a quite fast rebound.  As fast as possible without excessive bounce.  This is where the problem (confusion is a better word) arises.  As you reduce rebound damping to get the desired faster rebound, rather then a plusher ride as you expect the ride becomes harsher.  WTF you think, it's doing the exact opposite as you expect.   So naturally you reduce compression damping to see if you can remove than harshness.  Natural thing to do????  Now the suspension seems even worse, so you crank up the rebound a bit to improve things, but it's still all not right.

(C) What are you doing WRONG!!!!!!  What you have to do as you increase rebound speed, is INCREASE slow speed compression damping.  Undoing the rebound adjuster is not only reducing rebound damping, it is also reducing slow speed compression damping.  Because the wheel now rebounds down faster, with the corresponding reduced slow speed compression damping that comes from opening up the bled orifice (oil flows both ways) the wheel is now 'bouncing' on the road surface.  That is the harshness you feel as you reduce rebound.  While it seems totally counter-intuitive, if you are experiencing harshness as you reduce rebound don't hesitate to experiment with INCREASING slow speed compression damping.   And it may need to be increased quite a bit to remove that harshness.  Too much and the bike will again become harder to turn as the suspension again becomes 'tight'. 

That's why I say, if someone can afford a three way adjustable shock don't hesitate.  You need slow speed compression damping adjustment in order to fine tune it to whatever rebound adjustment is made.  High speed compression adjustment on a road bike is to me a totally different 'kettle of fish'.  I just set that so that the hit from really big pot holes doesn't smash my kidneys.  No more scientific than that.   All the real tuning is done between the rebound and slow speed compression adjustments.
Last Edit: July 12, 2019, 08:49:05 AM by JohnCW

Offline RobZ900

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Re: Fully adjustable Wilbers shock.
Reply #21 on: July 12, 2019, 10:24:06 AM
Cheers for that John. The suspension shop is going to set up a baseline when I get it all fitted, but obviously I wont know if thats right for me until I put some miles on it. Then the fine adjustments will start. Will bear in mind what you said about the balance between rebound and slow speed compression when the time comes :028:
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Offline JohnCW

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Re: Fully adjustable Wilbers shock.
Reply #22 on: July 13, 2019, 06:49:25 AM
*Originally Posted by RobZ900 [+]
Cheers for that John. The suspension shop is going to set up a baseline when I get it all fitted, but obviously I wont know if thats right for me until I put some miles on it. Then the fine adjustments will start. Will bear in mind what you said about the balance between rebound and slow speed compression when the time comes :028:

My experience is that the baseline damping settings supplied by the manufacturer (both Wilbers and Nitron) were way out.  Far too slow a rebound, and way to much high speed compression damping.   This was despite the requirement being stated as spirited road riding on bad roads. 

I've see it stated the 'custom build' these manufacturers promote is more marketing spin than real.  Certainly you get a correct spring rate, but my experience has been that despite what you specify (bad roads) , the valving and settings seem like what someone would want for a pure track shock.

In no way trying to be negative as these triple clicker shocks are worth every cent.  What I'm trying to say is don't feel you must be doing something wrong in making quite significant changes to the baseline.  Certainly I found this necessary for both rebound and high speed compression on the road.  All I can assume is they must have way better quality roads in Germany than we do in Australia.

Offline RobZ900

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Re: Fully adjustable Wilbers shock.
Reply #23 on: July 13, 2019, 09:46:18 AM
*Originally Posted by JohnCW [+]
All I can assume is they must have way better quality roads in Germany than we do in Australia.

And the UK! I ride to work at 4am, so Ive had to learn my route so I can anticipate my road position in the dark to avoid the moon surface that passes for roads!
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Offline KellyL

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Re: Fully adjustable Wilbers shock.
Reply #24 on: July 18, 2019, 04:20:01 AM
@JohnCW - going a bit off topic, but I have a question about your Zephyr 750. What mods did you use to sort out the damper rod front end to match the premium rear shocks? I also have a W800 with Ikon 7610 rear and Promecha 'provalve' emulators with Ikon progressive springs in the front. I've spent 2+ years faffing with them, playing with fork oil viscosity etc. Works well some days, but not all. I'm reluctant to move up from twin tube Ikons to dual clickers if the front can't be sorted to match (plus it's a wibbly wobbly frame anyway).

Offline JohnCW

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Re: Fully adjustable Wilbers shock.
Reply #25 on: July 18, 2019, 12:07:56 PM
*Originally Posted by KellyL [+]
@JohnCW - going a bit off topic, but I have a question about your Zephyr 750. What mods did you use to sort out the damper rod front end to match the premium rear shocks? I also have a W800 with Ikon 7610 rear and Promecha 'provalve' emulators with Ikon progressive springs in the front. I've spent 2+ years faffing with them, playing with fork oil viscosity etc. Works well some days, but not all. I'm reluctant to move up from twin tube Ikons to dual clickers if the front can't be sorted to match (plus it's a wibbly wobbly frame anyway).

Hi Kelly,
Thread seems to have run its course, so hope the OP doesn't mind us going off topic.  It might be helpful to anyone with a bike with damper rod front suspension, as plenty of em still being sold.

Short Answer: I run Race Tech Cartridge Emulators with 0.90Kg linear springs, using 5W fork oil, and a fork brace.

Long Answer:  The fork brace is a must for any conventional forks.  Stand in front of the bike holding the bars with the front wheel locked between your knees.  Now push the bars back and forth and see just how much twist there is in the front suspension.  You'll never get the bike to carve a tight line (or even run straight over tar snakes or grooved roads) with all that twist.  A good engineered fork brace will remove most of the twist.  Careful though, care needs to be taken fitting em so as not to introduce a ton of 'stiction'.

I can't really comment on the merits of Promecha's emulators other than I once contacted him to ask how they controlled and adjusted the more important rebound.  His responses was basically buy a book on how suspensions worked.  I promised myself I'd never deal with him again.

Rebound with Reach Tech emulators is controlled by fork oil weight.  To get a half-decent rebound with the stock damper rods requires somewhere between 20-30W fork oil.  The problem with these heavy fork oil weights is that they change viscosity radically as oil temperature changes.  Virtually impossible to set a consistent rebound over a range of air and internal temperatures.  So I metal epoxied up the two rebound holes in each damper rod, decided on 5W fork oil, and then by a series of trial and error progressively drill out one of the rebound holes stepping up each leg at a time till I got the rebound speed I wanted (tested on the road).  Surprising how fast it can be done as you don't need to actually pull the inner and outer forks tubes apart.  In my case the final rebound hole size was 7/64" in each leg.

Then after soldering the bleed holes in the compression plate in the emulators, progressively drilled one hole out till I got the slow speed compression I wanted.  In my case that was 3/32" in one leg, and 5/64" in the other.  That's the level of precision in adjustments you need. Imaging how small the bleed orifice opens up with just one 'click' turn on a cartridge, and one click when you getting close to the 'money' can easily be felt.

High speed damping is set to 2 1/2 turns of the 'blue' springs.  Race Tech has 3 differently colored springs of different strengths to control the damping curve.

One great thing the ZR750 has going for it is a very rigid frame (as far as cradle frames go).  Stock they came with all the bracing that people have to stick on the frames of 70-80s bikes when they want to race.  Very well engineered cradle, plus a fairly decent rear swing arm. 

P.S.  For anyone wondering what emulators are, they are these things and added into damper rod suspension to give adjustable rebound and compression damping (both slow and high speed). 

Last Edit: July 18, 2019, 12:27:17 PM by JohnCW

Offline KellyL

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Re: Fully adjustable Wilbers shock.
Reply #26 on: July 18, 2019, 01:23:21 PM
Thanks John, that's really valuable information. And apologies Rob for the thread hijack, but I love a good suspension discussion!

The Promecha emulators are much the same as the Race Tech functionally, except that they put a washer shim stack inside the valve orifice instead of the spring-type piston valve. This shim stack is the compression circuit, whilst rebound is via the stock damper rod orifice. I need 20W for decent rebound. There's pretty bad small bump compliance, but acceptable high speed (square edge bumps etc). Harsh at low speed, but handling improves at higher speed. Promecha also modded the fork spring rate by slicing off some of the tighter coils (i.e. the 'softer' bit) and did some mystery modding to the rear shock shim stack + rebound needle taper. Yes Peter is a character to deal with, and probably should have retired a while ago.

Based on your info, perhaps a way forward is to junk it all and go 0.9/0.95 linears and go Race Tech (more tuneability), shrink the rebound orifice, 5W oil, and find a fork brace. Shouldn't be an issue with options, as 39mm fork is a Harley Sportster size.

Doing a search for W800 tuning info on the internet is like finding a needle in a haystack. You have to sift through all the crap cafe racer conversions to get to proper useful stuff.

I'd love to get my hands on a ZR750, but people are now asking crazy money for them. All the CB Seven Fiftys being advertised are also overpriced and really clapped out.


Offline JohnCW

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Re: Fully adjustable Wilbers shock.
Reply #27 on: July 18, 2019, 02:20:51 PM
The idea of using light weight oil comes from SV650 crew.  In their case they completely block the rebound holes and just rely on leakage past the internal seals (damper rod head and stem) .

I started like that using 10W oil as a first guess.  Suspension wouldn't even move.  Dumped that out and stuck in 2.5W being the lightest you can buy with no holes it was still to slow.  Got it all working with 2.5W and some small holes but decided such light oil would mean accelerated wear, so redid the whole exercise with 5W.

Moral being different forks require a slightly different setting (which can only be found by trial and error) but methodology is still the same. 

Another significant advantage of light weight oil is that it is so much cleaner to work with that sticky 20W which clings and drips everywhere. 

I also quickly learned to recycle the 5W oil with each 'tinker' as it gets expensive real quick dumping it after just a test ride.   Drain it into a clean bottle, and then refill the fork putting it through a paper paint strainer.  Just needs a small top up. 

I've got the process down to a point where I can pull the damper rods, drill and reassemble ready to ride in about 1 hour.

Offline RobZ900

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Re: Fully adjustable Wilbers shock.
Reply #28 on: July 18, 2019, 06:03:17 PM
*Originally Posted by KellyL [+]
And apologies Rob for the thread hijack, but I love a good suspension discussion!

No worries, its all useful information. Personally, Ive never upgraded the suspension on any bike before, so Ive got zero experience of it, so this is all a learning curve for me. I understand sag, static sag, and rebound and I know what compression is, but still figuring out low and high speed comp. Obviously low speed is for small bumps etc. and high speed is for things like pot holes when you hit them harder/faster, Im just figuring out how to set them all. I know how to measure and set sag and fork rebound. As for rebound on the shock, it seems a bit harder to judge what should be about right. Then compression is a different animal all together. Seems to me that theres no real science to it, rather setting a starting point and then adjusting to suit, all by feel, which would be a very personal thing.

All I know right now is that my suspension isnt up to the job for someone my size. At 6 6 and 116 kgs/255lbs, I dont think Kawasaki had someone like me in mind when they fitted the suspension lol.
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Offline KellyL

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Re: Fully adjustable Wilbers shock.
Reply #29 on: July 19, 2019, 12:18:16 AM
Rob I'm no expert, but I learnt most about suspension tuning from riding mountain bikes. There's lot of good info out there, but here's how I think about springs and damping:

Springs
Manage static weight/mass.

Damping
Manage dynamic movement.
Low speed compression - controls pitch and dive with acceleration and braking, respectively. (Works in conjunction with swingarm geometry to influence anti-squat, but that's a rabbit hole.)
High speed compression - controls bump compliance.
Rebound - determines recovery back to neutral geometry.

Coming back to your original question about compression adjusters - if the shock only has one C adjuster, then it's usually low speed compression.