Ceriani rear shock preload question.

C

cwis

Full member
Hi all,

Daft question - how can you tell what preload position Ceriani rear shocks are set to? Both preload lugs face backwards, and knowing my luck, I'll snap one off turning it the wrong way investigating, so if anyone can shed some light I'd me most grateful.

Currently the unloaded distance from shock mount to shock mount is 370mm - it that wound up or wound down?

The bitsa sailed through another MOT this morning and I'm looking for a little more rear ride height while I accumulate the pennies for a new pair of shocks...

Cheers all!

Chris
 
Depends on which way round the shocks have been fitted, the Cerianis are handed. They handle comes out at an angle. Got a couple of unmolested 3c's here at the moment and levers back is least pre-load. Note it is pre-load on the spring the lever adjusts not ride height.


    Keith
 
Cheers Keith. I'll have a go at winding them up then.

Once a shock has the weight of a bike on it (and is not topped out any longer) then pre-load effectively adjusts the ride height. The spring stays the same length (because the same weight is on it) but the pre-load collar is further down the shock body, making the (compressed) shock longer.

But you knew that!

The only difference as I see it (and I'm happy to be corrected) between pre-load and ride height adjustment on a shock is that ride height will change the topped out length of the shock (and obviously the  loaded length too) whereas preload will change the loaded length of the shock (not the topped out length) which has repercussions for the mean position of the damper mechanism is during operation, and this can limit shock extension when the wheel is unloaded.

Did I get that right?

Best regards,

Chris





laverdakeith said:
Depends on which way round the shocks have been fitted, the Cerianis are handed. They handle comes out at an angle. Got a couple of unmolested 3c's here at the moment and levers back is least pre-load. Note it is pre-load on the spring the lever adjusts not ride height.


    Keith
Click to expand...
 
Can't see a ramp - it looks like it's internal.

It's academic in any case - they appear to be seized. Hey ho - a month or so more of it dragging it's arse on the floor (is what it feels like) and then I'll stick something better on there.

Thing is the weight bias is so far rearwards it plays havoc with stability at speed... And that's not taking into account the very poor damping. Makes it interesting!



Paul Marx said:
Just look at the ramp you're turning with the "lug".
Paul
Click to expand...
 
Longer shocks would be good if your legs are long enough- when I get round to ordering some for the RGS they will be 10mm longer than standard. 

Also lopping off an inch or so off the forks if it's a 180 will help the steering and front end feel- made my old bike feel much better.  Use clip ons first if you are unsure and be prepared to shorten the stand by 10mm.  I  have only dropped the forks through the yokes by 10mm so far on the RGS but even that helps the fork action and steering- 10mm on the rear should make it perfect and help the looks too- lots of RGSs look a little tail heavy to me.
 
cwis said:
Can't see a ramp - it looks like it's internal.

It's academic in any case - they appear to be seized.
Click to expand...

Chris, just pull the springs off, squirt a bit of your favourite penetrating lubricant around the shock body inside the adjusting collar, and maybe give the collar a light tap with a non-marring hammer. They should come right off. Then you can clean the collars and the shock bodies and reassemble, maybe with a spray of silicon lubricant?
The collars are fine silt/sand traps, which causes them to lock in place when they sit for a while. When you put them back together try a squirt of silicon or Teflon (or both) spray occasionally, and a shot of colloidal graphite won't go astray either. Whatever you do the fine particulate crud will build up over time (unless you use shock covers), and they'll gum up again eventually. If you wiggle them once a month or so they should last a long time before you have any more problems, unless you ride on dirt roads a lot. Then you have to clean them out again.

Ken
 
Chris,
Pre load and ride height adjustment should be treated as seperate entities. If you wind the preload up in the way you suggest you will dial out the static sag and probably most of the rider sag as well, which in turn could potentially reduce the sag on the front. If you don't have sag your shocks will top out on bumpy roads and handling will be 'orrible.
On a pre Jurassic shock like the Ceriani the pre load adjuster is primarily to adjust out the difference in  laden sag that might exist if a 10 stone Jota rider starts taking his 16 stone boyfriend on the back.
If you are needing to adjust the pre-load excessively for solo travel then you probably need to look at heavier spring rate. If you're trying to raise the ride height for some reason then you need longer shocks or alter the mounting points on the bike .


 
Heh! Bob - you are completely correct and I will end up with longer rear shocks and possibly shorter forks eventually. I'm looking for a short term halfway house compromise deal - I'm aware of the difference between ride height and pre-load but on a smooth road there is no difference. Mostly....

I'm the 10 stone Jota (well - bitza) pilot but there is no 16 stone boyfriend - I just want to adjust the attitude of the bike - I prefer to have my arse in the air and my face buried in the carpet tank when I'm riding - perhaps I should buy a 120?

All of my bikes have had the rear end jacked up and the front end lowered - I like the feeling at turn in, the faster turn in and the heavier steering. I used to ride quite quickly down very bumpy roads and I'm sure a bike with more front end weight is more stable than standard.

Ken - I'll have them apart then. I've got some spring compressors (somewhere!) so it's a no-brainer really.
 
It's an interesting quandary Chris, and I'm guessing you can't drop the yokes down the forks because the fork tops foul the bars?
I think a trip to a suspension specialist might be on the cards in the near future, longer shocks perhaps and subtly shortened forks perhaps...
I've found when experimenting with front ride height that you can get to a critical point when you experience dramatically increased front tyre wear. It's worth keeping an eye if you're trying out some new ideas. On my old spaceframe the difference between excessive tyre wear and acceptable was something like 5mm to 7mm of fork poking out of the top of the yoke; ie raise the front ride height 5mm and the tyre wear became acceptable. I don't think a 3C frame will be quite so sensitive but its worth bearing in mind.
Your front mudguard will probably be clouting the middle pipe long before tyre wear becomes an issue! :D
 
cwis said:
Can't see a ramp - it looks like it's internal.

It's academic in any case - they appear to be seized. Hey ho - a month or so more of it dragging it's arse on the floor (is what it feels like) and then I'll stick something better on there.

Thing is the weight bias is so far rearwards it plays havoc with stability at speed... And that's not taking into account the very poor damping. Makes it interesting!



Paul Marx said:
Just look at the ramp you're turning with the "lug".
Paul
Click to expand...
Click to expand...

Silly me, you're right, it's internal.
Sorry!
Paul
 
I know sod all about the mechanics of it all but I used to ride my 3C pretty hard and the Ceriani shocks were always on the hardest setting. Prehistoric suspension I suppose but I had lots of fun and it was very stable.
 
I've been running Wilbers shocks with a length of 365mm on my Jota and am quite happy with them. At the time I still had modified the Marzo forks and the extra length was noticeable even with this dinosaur. Wilbers, like most of the aftermarket guys, are happy to build lengths to suit. Once the Emulators and Wilbers springs went into the forks the handling sharpened up more even more. Raising the tubes in the clamps isn't an option due to the handle bars being in the way. The Ceriani fork bikes IMHO handle better out of the box than the Marzos which makes life simpler. You mentioned having a bitsa so I don't know what you have installed. Regardless what you decide to do make only one change at a time and see how your bike reacts before going on to the next experiment.

Tom
 
Hi all,

Thanks for all the replies - food for thought.

I do have jota bars so you are all right - I can't simply drop the forks through the yokes to lower the front. I'll have to look about for some clip-ons, but if this will be a temporary measure I don't really want to spend much cash! The forks are Ceriani by the way.

The bike feels like it's too low at the back. It feels great into downhill bends, understeers slightly the rest of the time, and is unstable at speed over bumps - feels like a weave is not far away. I put the instability down to too much of the bikes weight on the marginal damping at the rear end. I'd like to shift some of that weight forwards, and also (obviously) replace the shocks.

Bob - with respect to tyre wear, I've not noticed the increase you have when playing around with front end bias, but I have noticed that when I am happy with the bias, the chicken strips at both ends are the same size, proportional to the size of the tyre, if that makes sense. If the weight is too far to the rear, the front chicken strip is larger, and if I dial in too much front end weight, the rear chicken strip is wider....

Anyone else noticed this, or am I the lone mentalist?

Best regards,

Chris
 
It might not be a bad time to check the condition of your steering head bearings. Bad bearings can also cause funny steering.
 
Good call - they were what I replaced first, before thinking about dicking with the ride heights. I also re-arranged the cable routing around the headstock for minimum stiction - people often overlook this and it can make a real difference!



markblurr said:
It might not be a bad time to check the condition of your steering head bearings. Bad bearings can also cause funny steering.
Click to expand...
 
Hi Chris,
  If you remove the centre console (the alloy plate holding speedo & rev counter),and replace the four studs with new longer ones say 20mm longer and make up two spacers (20mm thick) to fit on top of the yoke,but under the handlebar,directly under the centre console;you'll beable to move your forks through the yokes by upto 20mm.

Worth trying?
Andy
 
Got to be worth a go! I've got an R1 master cylinder on the bike for the front brake (far smaller than the original) which gives me far better flexibility as to how I arrange the handlebars.

I'm going to try and get some time in the garage over the weekend to free up the preload adjuster on the shocks (I've also downloaded the Maxton application form so I can measure up for new shocks too!)

Chris

KERMIT1200 said:
Hi Chris,
  If you remove the centre console (the alloy plate holding speedo & rev counter),and replace the four studs with new longer ones say 20mm longer and make up two spacers (20mm thick) to fit on top of the yoke,but under the handlebar,directly under the centre console;you'll beable to move your forks through the yokes by upto 20mm.

Worth trying?
Andy
Click to expand...
 
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