Suspension Advice?

[mickarch]

Hi Everyone,

I'm hoping I can tap the vast experience of the collective here to determine the most cost effective approach to improving the ride quality of my '93 FJ.  The problem I have is that on the crappy roads in SE Michigan, I'm getting beaten up.  On most of the expressways there are humps where they've patched in expansion joints every 100 feet or so that are proud of the adjacent pavement by a inch or two.  They're like speed bumps at 70mph.  Then there's the ubiquitous ruts and pot holes, you steer around one right into another it seems.

I've opened up the forks and it looks like the PO swapped out the stock springs for aftermarket progressive springs and pvc spacers to get preload (springs were 18" long with no markings whatsoever).  I replaced the really nasty fork oil with new 15W and that really improved the handling but perhaps I should have went with 10W as it still bucks pretty good on the expressway speed bumps.  The rear shock is stock and doesn't seem to be able to absorb the bumps at all, feels like everything is transferred straight to me.

It seems like the greatest benefits would come from a Penske shock out back and USD forks up front, but that is probably also the most expensive combination too.  What would you all suggest to smooth out the ride?  I don't mind saving up and splurging on a Penske, from what I've been reading it can't be beat.  Will it be up to the task of taming the jolts from the damn "speed bumps"?  Should I bother with emulators in the stock forks, or move up to true cartridge forks?  If cartridge, is there a relatively straightforward swap that would get me external adjustments for compression and rebound damping.  Are USD's better than regular cartridge forks, or just neat gimmick to have?

The mods I've done so far: yzf600r rear wheel and blue spot calipers w/ 14mm master, ignition advancer, and new coils with a relay.  The bike runs great, it's all day comfortable on smooth pavement, but needs some help on the rough stuff.

Thanks in advance.  I really appreciate all the information that has been amassed here, I spend a lot of time lurking and searching and this resource has been invaluable.

Mickey

[RichBaker]

I have emulators and straight rate springs (1.0kg/mm, 15w oil) in my stock forks, the combination works very well..... But is definitely not a substitute for true cartridge forks. USD forks are another big improvement over conventional cart. forks..... Depends on what you can find and afford.
I picked up an Ohlins shock 10 or so years ago, a huge improvement over stock, the Penske is a 1/2 step up from there....

[junkyardroad]

I use emulators with stock springs in the fork set at max preload with Bell 10w.  Stock rear is adjusted to max preload/damping.

Rides and works pretty well for a 230 lb rider doing pretty casual loops thru the twisties, 200 miles a day average in Colorado.

I think the emulators are a worthwhile improvement, but like you said, a set of USDs are the best if its in your budget.  Really if depends on what you prefer and can afford.

I went airborne off a nasty frost heave on the Grand Mesa a week, and the bike was well composed on landing, no bottoming, wobble, etc.  The dampening was spot on for a quick flight at speed.

[Dan Filetti]

http://www.fjowners.com/index.php?topic=448.0

Anyone?

Dan

[axiom-r]

Hey Mickey- I grew up in the burbs outside of Detroit and I have to say I don't think anything will help with those concrete seams in the highway- man those are just some bad roads. The one I recall as the worst was west bound I-94 leaving Detroit towards Chicago.

You should be able to find several different options for upgrading your suspension and there are some really good examples here to see.

Cheers-

tim

[racerrad8]

Mickey,
         If you can hold off a little while, I am in the middle of testing of a valve that installs in the forks that convert the forks to cartridge style valving.

I have a set in my bike and I was truly impressed at the ability of the valve to absorb the high speed bumps and remove them, but the slow speed cornering shock travel is controlled by the valve stack.

Bill (the fan) is currently doing all of the hard data testing for me to make sure we have the spring pack shims correct. Once he has all of the testing done, then I will have them put into production.

This valves will not require all of the modifications to the existing internal parts the the gold emulators require with the only modification being the removal of the "D" rod.

Randy - RPM

[Mark Olson]

fork brace helps a lot with the freeway joints.
penske shock with radial tires.
emulators or cartridge depending on your budget.

[mickarch]

Thanks All for the suggestions.  There is a set of gsxr1000 BPF's on ebay right now for $200, unfortunately my fabrication and machining skills are non-existent.  I'd probably need to spend that much on quality measuring instruments just to get started on the figuring

Sounds like folks have had positive results with the emulators.  Randy, do you have a time frame and price in mind for your new valve?  This sounds very promising and quite doable for a "parts changer" like myself.

Tim, you'd be impressed.  They just completely repaved 94 from Ann Arbor to Jackson, nice and smooth.  The really demon right now is 75 heading north outta town 

I've also been eyeballing Randy's fork brace. I've got pretty good expense check coming from work soon and I think I know how I'm gonna spend some of it.  Where's the best place to source a Penske shock?  That may be where the rest of goes...

Thanks,
Mickey

[JCainFJ]

 Mickey,

You need to look into doing the 1997 and newer YZF600r front end swap. I've done 7 of these and it works very well. The fork is a fully adjustable cartrage unit, and Race-Tech sells all of the parts needed to set it up properly.   You will find that any fork you mount to your FJ will need to be tuned to work its best. You also get a 3 1/2 in wheel with this mod too. The only hard part to find is a 1987-1988 FZR1000 triple clamp, it has the same tube CL as the YZF600 and the same offset as your FJ.
I have also done 6 or 7 CBR600 F3 cartrage damper swaps. This mod only provides for rebound adjustment, but it is very clean. I make the adapters to do this swap.  If you are interested give me a PM.

[racerrad8]

Randy, do you have a time frame and price in mind for your new valve?  This sounds very promising and quite doable for a "parts changer" like myself.

Thanks,
Mickey

Mickey,
       It is all truly in Bill's hands at this moments. I do know that he told me he was going to be testing them on Jon Cain's bike so hopefully Jon can get some miles on them as well.

I really have not discussed price to date with them; I want to get the product honed in for the application before I can really start taking numbers.

I am anxiously awaiting for the results from Bill myself.

Randy - RPM

[the fan]

Randy, do you have a time frame and price in mind for your new valve?  This sounds very promising and quite doable for a "parts changer" like myself.

Thanks,
Mickey

Mickey,
       It is all truly in Bill's hands at this moments. I do know that he told me he was going to be testing them on Jon Cain's bike so hopefully Jon can get some miles on them as well.

I really have not discussed price to date with them; I want to get the product honed in for the application before I can really start taking numbers.

I am anxiously awaiting for the results from Bill myself.

Randy - RPM

Actually I am using Dean Narramores bike. I installed them last night and have a second set of forks equipped with emulators to compare them with. Unfortunately I am leaving for Barber tomorrow and won't be able to put the forks on the bike or test ride until next week.

On forks I agree with Jon. A wel set up conventional fork will feel better on the street to a comparable USD. The added flex will help dampen out much of the rough stuff you hit mid corner whereas a more rigid USD fork will transmit more of the jolt through the frame. This is a big reason I decided to build a set of 96 YZF600 forks for my race bike instead of a set of class legal USD forks. What little feel I sacrifice with the conventionals is by far worth the added control on a bumpy track like Nelson Ledges or pre-repave gratten. There are some pretty nasty transitions and bumps jst off the race line at Mid Ohio as well.

If it were my bike I would go with a decent shock like the penske street sport and either a set of valves like the intiminators (very promising) or the emulators with straight rate springs. In the least on your bad roads up there I would run a set of straight rate springs (.95-1.0 kg/mm) and a lighter oil (10 wt max) If the valves are out of your budget consider removing the damping rods and modifying the rebound bleed hole. welding the stock hole shut and redrilling to appx 1/2 the stock size will allow you to run as low as 5 wt oil and retail acceptable control. If you go this route run the oil appx 10mm higher than stock (smaller air gap) to aid in controlling bottoming on really big hits. You might see a bit more front end dive under hard braking, but with the stiffer rate springs it should be no worse than what you have now. With the lighter oil and compression damping you will be able to use more of the spring to absorb the rough stuff, while the restriction in the rebound 'circuit' will keep things under control.

[racerrad8]

Actually I am using Dean Narramores bike.

Sorry, my memory has been overloaded for awhile now...

Randy - RPM

[markmartin]

  Where's the best place to source a Penske shock? 
Thanks,
Mickey

Here ya go...   http://www.traxxion.com/penskesportshock.aspx

[mickarch]

Thanks for suggestions Jon and Bill, I think I'm in agreement that the yzf600r would be the best solution for the front end.   I've searched out Jon's previous post with the parts list and instructions for the swap and have been scouring ebay for the parts to get an idea of the cost.  What I'd really like to do is get it all reasonably sorted before the end of July for a planned trip down to the Smokies.  If I go with the Penske out back, I think I'll need to be a little more frugal on the front for now.  I may just start with fixing up the stock forks with the proper straight rate springs and emulators with 10W oil to get me through for a while, then start collecting for the real swap.  I plan to keep the bike for as long as it lasts and don't mind keeping at the improvements over time.

Thanks for link markmartin, I'll be giving them a call tomorrow to see about setup and lead time.

Thanks everyone for all the advice and a big thank you to Marsh for hosting such a great resource.  Now where's that donate button?

Mickey