Zero rebound is OK ???

jerry · 13-01-2018, 11:05 AM

set Zero rebound on my S4 forks as an experiment !!!

Usually they are set rebound 4-18 and compression 7-16 bike handles great and suprise was the suspension is much more compliant , and comfy but also bike is more stable ??

this is confusing the forks at zero are not pogoing back on compression with zero rebound as soon as i added even 1 click of rebound the front end felt harsh over bumps again at anything more than 40mph ,
its clear that these forks dampers work best for high speed damping which is fine by me ,

even on the bumpiest roads i could find today at speeds up to 125mph front end was safe , comfy and no nasty handling although the famous S4 wobble just began to start if I was to press on to 130+mph etc I guess that maybe a steering damper is going to have to be considered .

also the front end was nicer over thosee horrible washboard type concrete roads which are common in some areas ..you know what i mean ...

But I need to under stand why setting zero rebound is good ,, are my forks K Teck damping ciruits valving wrong ,,????

i even added a couple of clicks of extra compression damping and still the bike feels nice ,, its certainly less bumpy all round and more relaxed to ride ,,and still corners fine

im happy but perplexed

forks are Showa SBK type off a 996
with KTeck valving and bushes and Ohlins 7.5nm springs ,, 7.5w oil , airgap 125mm springs out , Sag 28mm , preload is 4 lines out , forks are dropped thru yokes 20mm as 996 ones are 10mm longer than S4 ones

The rear Shock is an OHLINS PRCS 46 fully adjustable extras and external remote preload ,, no worries with its settings which are compression 12/24 rebound 15/40 sag 30mm , preload 5 /10 clicks

stopintime · 13-01-2018, 12:09 PM

Zero rebound is probably not zero. Valving/shims might be on the far end of the scale, giving you too much rebound damping in most positions. (I have the same issues on my Bitubo shock)

Darren69 · 13-01-2018, 01:12 PM

Even the standard S4 forks are over damped imho, I set mine to standard and keep clicking the damping back a bit at a time to try and find the best setting. Not there yet, but then I think the progressive Hyperpro springs I fitted screw things up a bit too.

jerry · 13-01-2018, 01:46 PM

darren ....10 years ago when my S4 had its original forks , with no real rebound damping circuit in them if you know what i mean, I also fitted hyperpro progressive springs and it was aweful ..

jerry · 13-01-2018, 01:49 PM

maybe i will have to have word with kteck they did my fork rebuild back in 2011 maybe the shim stack can be played with ??

jerry · 13-01-2018, 03:10 PM

been doing some research and as my compression damping adjustment is good but rebound is to quick/firm even at zero i should probably try thinner fork oil to increase the flow rate and therefore adjustment range ,, a good 5w synthetic like silkolene pro or equivalent may be the answer ???? instead of the 7.5w in now

Darren69 · 14-01-2018, 09:19 AM

Quote:

Originally Posted by jerry

darren ....10 years ago when my S4 had its original forks , with no real rebound damping circuit in them if you know what i mean, I also fitted hyperpro progressive springs and it was aweful ..

I beginning to think that the Hyperpro just doesn't suit this type of Showa fork, and while I wouldn't describe them as awful they are certainly not the improvement I have had when fitting the same kit to other older type rwu forks on other bikes. I shall continue backing off the rebound damping in the meantime to see if it improves them.

Fortunately I have another identical spare set and when i get some pennies they will probably be going to Maxton.

Mossleymonster · 13-03-2018, 09:54 AM

Quote:

Originally Posted by jerry

been doing some research and as my compression damping adjustment is good but rebound is to quick/firm even at zero i should probably try thinner fork oil to increase the flow rate and therefore adjustment range ,, a good 5w synthetic like silkolene pro or equivalent may be the answer ???? instead of the 7.5w in now

Have you got any further with this? I have the exact same issue, and before we wander into spending what will no doubt be 100s of £s I'm going try your rebound suggestion. It makes sense that the rebound could cause this.

I've just taken mine out from 12 clicks to 1, as the last bit seemed a bit vague on the adjuster, will report back when I've ridden it....

13-03-2018, 11:49 AM

Quote:

Originally Posted by Darren69

I beginning to think that the Hyperpro just doesn't suit this type of Showa fork, and while I wouldn't describe them as awful they are certainly not the improvement I have had when fitting the same kit to other older type rwu forks on other bikes. I shall continue backing off the rebound damping in the meantime to see if it improves them.

Fortunately I have another identical spare set and when i get some pennies they will probably be going to Maxton.

Just for info that will cost you approx. £500

I had some 916 forks rebuilt for my 900 including anodising (average quality) involving all new internals and seals sprung for my weight and riding style. Also got matching remote reservoir shock to match at the rear with the total bill coming in at around £1300

About a week after paying that little bill I spotted some lovely Silmotor headers on ebay Germany....now sat on my spare bed next to the forks....

350TSS · 13-03-2018, 05:47 PM

My Maxton re cartridge came back with Putoline 5 and 140mm air gap - not tried them yet but Maxton just might know what they are doing. BTW I am 90Kgs and bike is planned to be 150Kgs

utopia · 13-03-2018, 07:03 PM

Based on some pondering and some half-remembered fork techy stuff ......

Could the reason for the harshness that appears when you increase the rebound damping be due to the forks "racheting down", or whatever its called ?
My reasoning is that, if the forks have more rebound damping they will return more slowly and hence still be in a partially compressed state by the time they hit the next bump.
Multiple bumps means this happens each time and so they "ratchet" down. Might explain the extra harshness over ripples ?
With less rebound damping they can return fast enough to be back to their "normal" position by the time the next bump comes along.

I may have got that all wrong.
Could have googled to check but decided to just post it, as it might prompt some further ideas.

As Lars says, zero on the scale is just a reference, not an actual zero. More like a minimum perhaps.
And lighter oil should shift the scale in your favour .. though it will also affect the compression damping so you may want to up that a bit to get back to where you are now, so to speak.

Mossleymonster · 13-03-2018, 09:46 PM

Today, I finally got my bike back to the shop to get the seized shock bolt out. I had planned to get the shock to Teut at TW suspension in Prestion to get sorted.

Anyhoo, dropped the bike off, set off home. Teut rang and said it would be 3 weeks, he's getting busy.

I'm thinking WTF.

Pete, who owns the shop rings and his mate is there. He's an engineer with Ktech.

Ktech are doing the shock and providing new fork springs.

It's all looking good and not silly money.

What a smashing day.

Luddite · 13-03-2018, 10:07 PM

Quote:

Originally Posted by Mossleymonster

Ktech are doing the shock and providing new fork springs.

It's all looking good and not silly money.

What a smashing day.

An auspicious start to the riding season!

Chris.p and I have both had our forks resprung and revalved by Ktech with excellent results. Great customer service too. You won't be disappointed.

Chris posted a detailed report of the whole process here:

http://www.ukmonster.co.uk/monster/s...ad.php?t=51391

Mossleymonster · 13-03-2018, 10:11 PM

I'm happy already. Hopefully I'll have something that's rideable. When I had the 750 in 2002 I could ride round roundabouts one handed rubbing the toes out of me boots.

Darren69 · 15-03-2018, 08:26 AM

Quote:

Originally Posted by Nottsbiker

Just for info that will cost you approx. £500

I had some 916 forks rebuilt for my 900 including anodising (average quality) involving all new internals and seals sprung for my weight and riding style. Also got matching remote reservoir shock to match at the rear with the total bill coming in at around £1300

About a week after paying that little bill I spotted some lovely Silmotor headers on ebay Germany....now sat on my spare bed next to the forks....

If you have any pictures, I'd be interested to see what the anodizing quality was like because mine will need doing and if K-tech do a similar but better quality re-anodizing I may be better off sending them there.

13-01-2018, 11:05 AM	#1
jerry Old Git Join Date: May 2006 Location: Cricklade Bike: Multiple Monsters Posts: 2,832	Zero rebound is OK ??? set Zero rebound on my S4 forks as an experiment !!! Usually they are set rebound 4-18 and compression 7-16 bike handles great and suprise was the suspension is much more compliant , and comfy but also bike is more stable ?? this is confusing the forks at zero are not pogoing back on compression with zero rebound as soon as i added even 1 click of rebound the front end felt harsh over bumps again at anything more than 40mph , its clear that these forks dampers work best for high speed damping which is fine by me , even on the bumpiest roads i could find today at speeds up to 125mph front end was safe , comfy and no nasty handling although the famous S4 wobble just began to start if I was to press on to 130+mph etc I guess that maybe a steering damper is going to have to be considered . also the front end was nicer over thosee horrible washboard type concrete roads which are common in some areas ..you know what i mean ... But I need to under stand why setting zero rebound is good ,, are my forks K Teck damping ciruits valving wrong ,,???? i even added a couple of clicks of extra compression damping and still the bike feels nice ,, its certainly less bumpy all round and more relaxed to ride ,,and still corners fine im happy but perplexed forks are Showa SBK type off a 996 with KTeck valving and bushes and Ohlins 7.5nm springs ,, 7.5w oil , airgap 125mm springs out , Sag 28mm , preload is 4 lines out , forks are dropped thru yokes 20mm as 996 ones are 10mm longer than S4 ones The rear Shock is an OHLINS PRCS 46 fully adjustable extras and external remote preload ,, no worries with its settings which are compression 12/24 rebound 15/40 sag 30mm , preload 5 /10 clicks __________________ MONSTERMAN

13-01-2018, 01:12 PM	#3
Darren69 Transmaniacon MOC Join Date: Sep 2013 Location: Sutton In Ashfield Bike: Multiple Monsters Posts: 6,042	Even the standard S4 forks are over damped imho, I set mine to standard and keep clicking the damping back a bit at a time to try and find the best setting. Not there yet, but then I think the progressive Hyperpro springs I fitted screw things up a bit too. __________________ Roast Beef Monster! Termignoni and Bucci - Italian for pipe and slippers! S4 Fogarty, S4R 07T, 748, Series 1 Mirage

13-01-2018, 01:46 PM	#4
jerry Old Git Join Date: May 2006 Location: Cricklade Bike: Multiple Monsters Posts: 2,832	darren ....10 years ago when my S4 had its original forks , with no real rebound damping circuit in them if you know what i mean, I also fitted hyperpro progressive springs and it was aweful .. __________________ MONSTERMAN

13-01-2018, 01:49 PM	#5
jerry Old Git Join Date: May 2006 Location: Cricklade Bike: Multiple Monsters Posts: 2,832	maybe i will have to have word with kteck they did my fork rebuild back in 2011 maybe the shim stack can be played with ?? __________________ MONSTERMAN

13-01-2018, 03:10 PM	#6
jerry Old Git Join Date: May 2006 Location: Cricklade Bike: Multiple Monsters Posts: 2,832	been doing some research and as my compression damping adjustment is good but rebound is to quick/firm even at zero i should probably try thinner fork oil to increase the flow rate and therefore adjustment range ,, a good 5w synthetic like silkolene pro or equivalent may be the answer ???? instead of the 7.5w in now __________________ MONSTERMAN Last edited by jerry; 13-01-2018 at 03:12 PM..

13-01-2018, 12:09 PM	#2
stopintime Registered User Join Date: Dec 2010 Location: Oslo Bike: S2r Posts: 428	Zero rebound is probably not zero. Valving/shims might be on the far end of the scale, giving you too much rebound damping in most positions. (I have the same issues on my Bitubo shock)

13-03-2018, 05:47 PM	#10
350TSS Too much time on my hands member Join Date: Jan 2013 Location: Shipbourne Bike: M900 Posts: 1,421	My Maxton re cartridge came back with Putoline 5 and 140mm air gap - not tried them yet but Maxton just might know what they are doing. BTW I am 90Kgs and bike is planned to be 150Kgs

13-03-2018, 07:03 PM	#11
utopia No turn left unstoned Join Date: Jun 2010 Location: leicester Bike: M750 Posts: 4,546	Based on some pondering and some half-remembered fork techy stuff ...... Could the reason for the harshness that appears when you increase the rebound damping be due to the forks "racheting down", or whatever its called ? My reasoning is that, if the forks have more rebound damping they will return more slowly and hence still be in a partially compressed state by the time they hit the next bump. Multiple bumps means this happens each time and so they "ratchet" down. Might explain the extra harshness over ripples ? With less rebound damping they can return fast enough to be back to their "normal" position by the time the next bump comes along. I may have got that all wrong. Could have googled to check but decided to just post it, as it might prompt some further ideas. As Lars says, zero on the scale is just a reference, not an actual zero. More like a minimum perhaps. And lighter oil should shift the scale in your favour .. though it will also affect the compression damping so you may want to up that a bit to get back to where you are now, so to speak.

13-03-2018, 09:46 PM	#12
Mossleymonster Registered User Join Date: Nov 2017 Location: Barnsley Bike: M1100s Posts: 238	Today, I finally got my bike back to the shop to get the seized shock bolt out. I had planned to get the shock to Teut at TW suspension in Prestion to get sorted. Anyhoo, dropped the bike off, set off home. Teut rang and said it would be 3 weeks, he's getting busy. I'm thinking WTF. Pete, who owns the shop rings and his mate is there. He's an engineer with Ktech. Ktech are doing the shock and providing new fork springs. It's all looking good and not silly money. What a smashing day.

13-03-2018, 10:11 PM	#14
Mossleymonster Registered User Join Date: Nov 2017 Location: Barnsley Bike: M1100s Posts: 238	I'm happy already. Hopefully I'll have something that's rideable. When I had the 750 in 2002 I could ride round roundabouts one handed rubbing the toes out of me boots.