suspension tuning, raising the rear?

[atomic410]

buy a 748 adjustable dogbone on ebay.  way cheeper than the $300 one mentioned.  most lowering links have enough adjustability to raise the rear because they are made for a varity of ducatis.  for example mine is a ca cycles lowering one and was about $75 brand new.  it has plenty of adjustability up and down.  don't mickey mouse one they can brake and then your ass is in trouble, saw it at the track

[BK_856er]

I use the one below on my M695 - has been worknig great for several years.  I think it was about $75 from (?) eastern cycle.  Their normal unit is for lowering, but this one was made to accomodate standard ride-height to + one inch.  The beauty of new is that you can load up the threads with antisieze so next time you try to adjust it it's not frozen solid!

BK

[atomic410]

thats the same one i have i think

[Mr Earl]

The 748 adjustable rod I'm running was sourced on ebay for $25.  Matching the fixed-length original M800 rod was well within the adjustment of the 748 rod - only ~3/8" of threads showing at each end, with just a bit of extra height dialed in.

IMO, the amount of preload you'll have to add to the rear shock to get any appreciable additional ride height will severely compromise your setup and handling.  Adjustable rods are made to adjust ride height, so that seems like the proper way to do it.

[Privateer]

The ebay listing is for a lowering link/rod. Not exactly what you need?

I sent the guy a message and was informed it can be used to raise as well.  I can read, I'm not a complete idiot.

[Speeddog]

Fixing ride height problems with pre-load isn't a good plan.

A longer pushrod changes the progression of the linkage.
I don't have the info here, but I'll try to check tomorrow.

But onto the original problem, harsh freeway ride is usually a high-speed damping issue.
Just to clarify, high shock movement speed, not high bike speed.

You could try reducing the compression damping with the adjust screw on the reservoir.
Unfortunately it's more of a slow speed adjustment, but it can help a bit.

[Privateer]

Fixing ride height problems with pre-load isn't a good plan.

A longer pushrod changes the progression of the linkage.
I don't have the info here, but I'll try to check tomorrow.

But onto the original problem, harsh freeway ride is usually a high-speed damping issue.
Just to clarify, high shock movement speed, not high bike speed.

You could try reducing the compression damping with the adjust screw on the reservoir.
Unfortunately it's more of a slow speed adjustment, but it can help a bit.

good info, thanks Nick.

On a plus side, the last two days I rode to work the ride was MUCH better.  I need to sit down and figure out what he set everything at.  There's a section of the 57N I ride almost every day that just beats the hell out of me.  Coming home the last two days the bike was much smoother and manageable with only the worst parts really bouncing me around.

I also checked with CA Cycleworks because I couldn't find anything from them.  They do have an adjustable link but out of my price range at $280.  a beautiful piece but can't swing it right now.



I'll start looking on ebay (yuck) and see what I can find.  Thanks for the tip on the 748 rod.

[devimau]

fork oil height won't have any direct relation with his issue, fork oil will play a major role when travels is @ it's last 1/3 of the stroke and more.....
do you have any idea how much preload you have on the front and rear to achieve your sag?

Can you reduce the compression damping and/or fork oil height on your bike?

Seems to me that will reduce the jarring somewhat. 

[battlecry]

Your comment may be relevant, or not, depending on how high those slab joints are.  Around here, we soften up compression damping to reduce the bumps we get from the slab.  The 620 does not have compression or preload adjustment on the forks.  Raising rear height may be something he needed to do anyway, but it doesn't address his initial complaint.

Put zipties on the fork slider to indicate maximum fork compression on your slab rides and on your panic stops.  If you are nowhere near full travel, you can start reducing the fork oil height in, say, 5mm increments until you soften it up and use more of your travel.  Motion Pro makes a nice measuring syringe tool for the job.

You must keep enough fork oil to cover the damper assembly under the spring.  If you are adventurous, you can try to experiment with (increase) the size of the holes at the lower end of the damper tube.  You can look at what some of the SV folks have done for ideas.  If you feel like spending some bucks, I'm pretty happy with AK20s and can recommend them.  I still run them with zero compression "clicks" on some slab roads.

Good luck. 

[Privateer]

Your comment may be relevant, or not, depending on how high those slab joints are.  Around here, we soften up compression damping to reduce the bumps we get from the slab.  The 620 does not have compression or preload adjustment on the forks.  Raising rear height may be something he needed to do anyway, but it doesn't address his initial complaint.

Put zipties on the fork slider to indicate maximum fork compression on your slab rides and on your panic stops.  If you are nowhere near full travel, you can start reducing the fork oil height in, say, 5mm increments until you soften it up and use more of your travel.  Motion Pro makes a nice measuring syringe tool for the job.

You must keep enough fork oil to cover the damper assembly under the spring.  If you are adventurous, you can try to experiment with (increase) the size of the holes at the lower end of the damper tube.  You can look at what some of the SV folks have done for ideas.  If you feel like spending some bucks, I'm pretty happy with AK20s and can recommend them.  I still run them with zero compression "clicks" on some slab roads.

Good luck. 

I didn't anticpate this thread going this direction which is why I didn't add much info.

For the record, while I do ride a 620, it has S2R1000 forks and a S4 shock, both with comp/rebound adjustments.

When I get some time, I'll measure up my sag and get all the adjustment points documented.  I did have them all down but the Race Tech guy didn't document anything so I didn't ask.

[Privateer]

OK.  Measured the rear today.

Static sag, 30mm
Free sag, 4mm

I have about 7mm of thread showing above the preload adjuster.

[atomic410]

finding a suspension guy and getting him to stand behind the work he does with you is key if you want to make steps into strides.  find a shop/suspension guy you trust and invest the time and money.  once you find the spot that you want you'll be in astonishment that you didn't just do it before like that.  it also makes the next bike that you own easiser to set up because you have a better idea to know where to start.  my 2 cents

[dlearl476]

I'm no expert, but from experience it is damping that makes a ride harsh or plush, not the spring.

When my monster was stock any 'sharp' bump would rattle my teeth...expansion joints, manhole covers, etc. I had the springs changed front and rear and the forks re-valved. I also went with an Ohlins. The springs installed were stiffer at both ends.

The bike eats up expansion joints with no harshness now.

I don't think adding preload will solve your problem.

With suspension, balance is the key.  Everything interacts.  Spring rate, compression/rebound, pre-load, ride height. Something as insignificant as the difference in ride height between a 180/55 and a 190/50 tire can affect it, I've experienced it personally.

As for expansion joints, the ones around here are affected by something as insignificant as tire pressures.   

[stopintime]

OK.  Measured the rear today.

Static sag, 30mm
Free sag, 4mm

I have about 7mm of thread showing above the preload adjuster.

Those numbers are fine AFAIK.

Plan on measuring the front? (reg balance as commented)

[BK_856er]

finding a suspension guy and getting him to stand behind the work he does with you is key if you want to make steps into strides.  find a shop/suspension guy you trust and invest the time and money.  once you find the spot that you want you'll be in astonishment that you didn't just do it before like that.  it also makes the next bike that you own easiser to set up because you have a better idea to know where to start.  my 2 cents

+1 on that.  Over the course of several years I learned everything I could and experimented with the entire gamut of parameters, including fork oil viscosity and height, sags, ohlins, penske, matris, 4-5 different shock springs, geometry, etc.  I approached everything very systematically.  It was quite a journey and I learned plenty.  Recently I took it to the local guru and $20 later the bike was "balanced" in a manner that I could never quite achieve on my own.  I was trying to do things by the book, which is all I knew, but the guru could draw on his many years of experience to get everything to a happier place with some final tweaking of spring tension and hydraulics.  The same guru/tuner, Dave Moss, does the trackside tuning on my SBK.  Great local resource.  A suspension that works for you is a wonderful thing, but at the same time any given setup is always a compromise!

BK