Independent Rear Suspension, OEM, aftermarket, stock configuration or heavily modified, all makes and models, everyone is welcome here!!!

You are not logged in. Would you like to login or register?



1/28/2014 5:09 pm  #31


Re: Hi, I have two IRS projects to work out.

I hear you want to keep it simple.  But, there is (can't find it now - away from home base computer and my cloud has crashed), BUt there is a fellow on the west coast (I recall) the did a C-5 Corvette IRS on a very hot Miata.  It is not without some Engineering Challenges. 

My C5 mods have followed his approach.   Uprights need to be drilled and inserts maded or change out the the  ball joints.  I had my local machinist do some work and was not terribly expensive.  Maybe a hundred bucks for the pair.  I used some bits from Coleman Racing to insert.  He tapered those and the ball joints fit right in.  With this aproach you can then taylor the chassis mounting locations, and length of arms to get the stance and performance you want.

You might take a run by the Pro-Touring Forum, or Lateral-G - I think that is where I found some of his work and led to his webpage.

Cheers - Jim
___________________________________________
"Head down - Bum up" in the bilge in Southeast Asia.


UNDERCONSTRUCTION! Highly Modified C3 Corvette
         Dual Wishbone IRS w Subframe + Custom Uprights
 

1/29/2014 6:03 pm  #32


Re: Hi, I have two IRS projects to work out.

Wow!  Was that off base!  Sorry for the bad leads.
1.  Not Pro-touring - but Lateral-G,
2.  Not C5 - but C6 (essentially the same)
3.  The biggie - NOT a Miata, but a Porsche 914

All can be found here (I hope...):
www.negativereinforcementracing.com

Cheers - Jim


UNDERCONSTRUCTION! Highly Modified C3 Corvette
         Dual Wishbone IRS w Subframe + Custom Uprights
 

2/26/2014 9:12 pm  #33


Re: Hi, I have two IRS projects to work out.

Poked around the web and this forum tonight looking for clues on my GT6 rear IRS build.
Tried the Chevrolet IRS thread and only saw ONE pic of a Fiero rear, TONS of Corvette pics.

I'm going to try to get some measurements and pics from a Fiero.
My thought is to toss the strut and replace it with an upper arm and coil over shock.
I can get a complete rear pretty cheap at the junk yard.
Section the cradle, or maybe cut it down and weld it direcly to the GT6 frame?
Toyota Supra or 90's T-Bird diff.
Only needs to survive about 250 HP.

I am surprised to not see more discussion of modified Fiero IRS here.

Last edited by Richard/SIA (2/26/2014 9:13 pm)


At these prices I want my gas 100 octane, leaded, and my windshield washed!
     Thread Starter
 

2/27/2014 1:14 am  #34


Re: Hi, I have two IRS projects to work out.

A late night update.
Found some great pics of Fiero rear suspension uprights modified to use an upper A arm.
LONG thread with CAD drawings and much discussion here, http://www.fiero.nl/forum/Forum3/HTML/000116-16.html
I am not interested in the rocker shocks and his drawings will not directly work for my use.
I probably have to build a sub-frame at the rear of the GT6 but with the body off that should not be hard.
I hope to be able to leave the wheel wells alone.
This may be a way to keep a budget build while also getting much improved rear suspension geometry and brakes.
Since I want to keep 13" wheels I expect to retain the original Fiero calipers.
Much more research to do, hoping to visit a junk yard this week with some calipers and digital camera in hand.


At these prices I want my gas 100 octane, leaded, and my windshield washed!
     Thread Starter
 

7/06/2014 10:42 pm  #35


Re: Hi, I have two IRS projects to work out.

Got the body off the GT-6 today.
This gave me a chance to see what the previous builder had done, a true nightmare!
I know a four link live axle can work, but this abomination never stood a chance!
Looking at other details I have decided to start with an uncut frame rather that spend a lot of time reworking the bodge the last guy made of this one.

http://www.specialinterestarms.com/DSC00947.jpg

 

Last edited by Richard/SIA (7/06/2014 10:49 pm)


At these prices I want my gas 100 octane, leaded, and my windshield washed!
     Thread Starter
 

7/13/2014 12:06 am  #36


Re: Hi, I have two IRS projects to work out.

I now have a hazy idea of how to do my IRS for the "Trick-6". (TRIumph GT-6 + buICK V6 engine)
Of course wanting to use my 4x108 PCD 14" x 6" Enkie (Very light) wheels gets to be an additional issue.

Looks like Ford or Supra diff. will be easiest.
Both can be had with forward mounts that may be close to what I need.
Ford should be unbreakable even with an aluminum carrier, I only have a little 225 V6.
Supra may be smaller and so easier to fit.

Ford appears easier to find, in cast iron.
Supra seems to be a little hard to get, CL sellers don't answer if you live more than a couple of miles away and tend to want high prices despite not even knowing the gear ratio's.

Supra's do show up in the P&P salvage yards, IF you can get there fast enough.
If not they will be on CL a day later, at 5x the price.

Outer end may be simpler if I can use Ford, some are the correct PCD, have to verify that some IRS are still 4 x 108mm.
Also need to confirm a 14" wheel clears.

No matter what I use it's going to be custom control arms.

Found this reference on the web, from V8S2000 board:

"Ford 8.8 IRS Info
ALL 99/01/03/04 Cobra axles have a 28 Spline outer that goes into the hub

99 Cobra axles have a 28 spline inner that goes into the diff

01 Cobra's came with stronger axles than 99

01/03/04 Cobra axles have a 31 spline inner that goes into the diff

03/04 Cobra's came with stronger axles than 99/01

03/04 Cobra's came with Carbon kevlar clutch packs

03/04 Cobra's came with larger pinion flange than 99/01

All Cobra's came with limited slip

There was not a 2000 or 2002 Cobra released on the american market.


The 8.8 IRS was offered in the following vehicles

99/01/03/04 Cobra

1989-1997 Thunderbird Supercoupe (All Posi-traction)
1992-1997 Thunderbird V-8 models with rear disc brakes(some posi-traction)3.08, 3.27 
1992-1997 Lincoln Mark VIII (All aluminum carrier, most non-posi-traction) 3.07, 3.08, 3.27, 3.55, 3.73
1989-1992 Mercury Cougar XR-7, supercharged V-6 (All posi-traction)
1993-1997 Mercury Cougar V-8 

02+ Explorer/Mountaineer = 3.55 and 3.73 open, 3.73 LSD , 31 spline

To determine the gear ratio, and whether or not the unit has posi-traction, look at the tag that is attached to one of the differential cover bolts. The first 4 spaces signify the gear ratio and whether or not it has posi-traction. If the unit has posi-traction, then the second space will have an L in it representing (limited slip), the remaining spaces specify the gear ratio. For example, 2 L 7 3 means posi-traction with a 2.73:1 gear ratio. Most people pay a salvage yard between $300-$400 for the donor parts. Also, Ford Motorsports sells a 15lb. lighter aluminum carrier with gears and posi-traction for around $650.


At these prices I want my gas 100 octane, leaded, and my windshield washed!
     Thread Starter
 

7/14/2014 12:23 am  #37


Re: Hi, I have two IRS projects to work out.

Finally got to drag the Jag rear under the El Camino frame. http://cdn.boardhost.com/emoticons/happy.png

Threw a few blocks under it get a clue how well it fits.
Have to get some precise measurements and mock it up much more carefully, but at first glance it looks great!
If there were a good way to use the spring pockets as mounting points a bolt-in conversion would probably be possible with a little extra work.
Original upper trailing arm mounts could certainly be utilized if I do a soft mount for the new cradle.
Lower trailing arm mounts could probably be re-used for the Jag very similar to the Jag originals if I did not want to improve that so much.
I'm thinking the spring pockets are coming off the frame to make room for the cross bar over the diff.
Upper Chevy trailing arm mounts may have a reinforcement point welded into them for upper  mount triangulation.

I really have to determine the diff mount height before I can finalize anything.
Guess I need to review a lot of prior post.

Will try to take pic of what I have so far and post it.


At these prices I want my gas 100 octane, leaded, and my windshield washed!
     Thread Starter
 

7/14/2014 12:28 am  #38


Re: Hi, I have two IRS projects to work out.

Oh, and on the Trick-6, I'm now looking for Sierra/Merkur IRS pics and info.
Has the right PCD for my wheels and I'm pretty sure they are disc brake as well.
A bit rare in the U.S. but I do have a line on a couple that are just a little too far away to be convenient.


At these prices I want my gas 100 octane, leaded, and my windshield washed!
     Thread Starter
 

7/14/2014 3:51 pm  #39


Re: Hi, I have two IRS projects to work out.

Got a look in daylight, think I've got most of it figured out for rough design.
Plan is that it will unbolt for service, bushed mounting.
Probably overkill but I think I will have six attachments for the carrier.
The usual mount across the top, I have to cut away the old spring perches for access to the area i want to put the mounts at.
A pair of mounting brackets extending forward from the top mount to the old Chevy upper trailing arm mounts.
A pair of arms forward from the front diff tie-bar to the old lower trailing arm mounts.
This will give me a lot of triangulation despite being mounted on bushings.
It also incorporates oringinal Chevy frame brackets at four of the six mounting points.
I dont have a handy cross member for an angled trailing arm mounting point.
I'm liking this Watts link, simple and inexpensive since it uses the existing trailing arm mount.

http://www.clubcobra.com/photopost/data/500/Cobra_watts_link_Small_.JPG


Have to get my wheels off the car and some lug-nuts that fit the Jag hubs in order to do a better mock-up.
Need to measure my current frame ride height front and rear as well.
Need a trans cross-member so I can mock an engine and trans to check drive line angle and pinion angle.

Pics at page one show what I am working with on the Chevy frame.
What am I forgetting?


At these prices I want my gas 100 octane, leaded, and my windshield washed!
     Thread Starter
 

7/16/2014 12:15 am  #40


Re: Hi, I have two IRS projects to work out.

Well, I'm committed now! (Should be committed?)
Just cut most of the spring perches off.
Left a little to reinforce the frame.

I have a slight rake to my car with the original suspension.
Keeping that with the IRS, it IS an El Camino and levels out with a load.

255/60-15 rear tires, so 13" from ground to the center of the hub.
Rear frame is 8.5" off the ground at my measuring point.
I am using all dimensions at intended empty ride height.
I have 4.5" of suspension travel, I figure 4.0" after I add a 1/2" thick bump stop.
Top of the upright contacts the bottom of the frame arch at end of travel just like the Jag did.
Even with only two coil-over springs I expect this to be much stiffer than the original springs.

I am going to make some adjustable jack screws so that I can set my frame heights exactly rather than depend on blocks.
I beleive I also want the axles to set level/horizontal at ride height.
So I am going to have to lower my diff about an inch from where it is blocked up now.

Question!
What if any angle for the lower arms?
Fore to aft dead level, or some degree of angle?
If at an angle how much?
Use is fast road car, might do a hill climb or Silver State Challenge, heck, maybe Willow Springs track day with the Ferrari Club just for giggles. http://cdn.boardhost.com/emoticons/grin.png


Bought material for the mount today.
2" x 2" .120 wall for the main mounting bar across the frame.
1.5" x 1.5" .120 for the forward reinforcements.
I've committed to the idea that the upper mount will have a "K" shape.
The back of the K is the main beam, the forward legs will bolt into the original upper trailing arm mounts.
I think it will be stronger than the original frame.
I also intend to create a lower brace from the forward tie-plate to the original lower trailing arm mounts.
So I will have a 3-D mount, well braced in all directions.
I like only have to add two mounting brackets for the main beam.
I will also have to add four simple mounts for the Watts link.
Pics once I get something tacked up.


At these prices I want my gas 100 octane, leaded, and my windshield washed!
     Thread Starter
 

7/16/2014 4:43 pm  #41


Re: Hi, I have two IRS projects to work out.

Quick pic of a rough mock-up.
Not the actual steel just some pieces I have laying around.
"K" shaped top mount.

http://www.specialinterestarms.com/DSC00971.jpg


At these prices I want my gas 100 octane, leaded, and my windshield washed!
     Thread Starter
 

7/17/2014 8:01 am  #42


Re: Hi, I have two IRS projects to work out.

Do you have guess where you'll put the bump stops?

 

7/17/2014 11:01 am  #43


Re: Hi, I have two IRS projects to work out.

Yes, fitted to the bottom of the frame arch.
Have to find some suitable parts.


At these prices I want my gas 100 octane, leaded, and my windshield washed!
     Thread Starter
 

7/25/2014 1:34 am  #44


Re: Hi, I have two IRS projects to work out.

Getting close to beginning to weld!
Need a little bit of flat plate and to verify my design.
Tomorrow I will pull the rear wheels to make measurements from the original El Camino axle.
I have the GM chassis book but cannot find anything stating exactly where the axle sits in the frame arch.
I will also make some measurments from an XJ6 for diff height.

What I need some help with is setting pinion angle.
It would seem to me that I want the lower arms to sit flat.
But they are mounted to the pinion housing.
Not sure how much, if any, angle might be desireable?
I thought I saw some discussion of this on the forum but my recent search did not find it.
Now also wondering if I dare make the rear mount without mocking up an engine and transmission first?

Tempted to weld in the upper mount for added frame rigidity but thinking that even a bolt-in design will help if I use poly bushings.

A little concerned that the lower watts link may be fairly close to the ground, need to get the correct lug nuts to mount my wheels for a measurement.
Watts link pivoting arm will have to be fairly short.
Trailing arms might be simpler but get in the way of the exhaust system.


At these prices I want my gas 100 octane, leaded, and my windshield washed!
     Thread Starter
 

7/25/2014 8:02 am  #45


Re: Hi, I have two IRS projects to work out.

How difficult would it be to put the rear axle in and find the center?

Your pinion angle should be the same angle as the angle coming out of the transmission.  Typically, it is 3 degrees.

You do want your lower control arms to sit flat/parallel to the ground.  The L bracket which attaches the LCA to the main pumpkin determines what pinion angle you can support.  The good news is, the most common L bracket supports a 3 degree pinion.

It won't hurt to place the engine & transmission on the frame to double check your angles.  Putting the driveshaft in might also help to determine where to mount the rear with respect to the frame arch.  Should be close.  I would measure from the pinion input to the center of the original axle and do the same with the new pinion.  This should give you an idea of how to center the new axle.

If you run out of space to send the trailing arms to the front of the frame, you can send them to the back of the frame.

Good luck!

 

7/27/2014 5:33 pm  #46


Re: Hi, I have two IRS projects to work out.

Got tired of imprecise wood blocks holding the frame up and made some adjustable stands from ready-rod and scrap.
They go through existing holes in the fram and are fully adjustable.

http://www.specialinterestarms.com/DSC00990.jpg


At these prices I want my gas 100 octane, leaded, and my windshield washed!
     Thread Starter
 

7/27/2014 10:35 pm  #47


Re: Hi, I have two IRS projects to work out.

Found some refernce points and measured the center of the arch for the axle from the old frame and live axle.
Now looking at the Watts link, looks like I only have about 3" available end to end since I would not want it on the ground if I get a flat tire.
Tire sidewall is only 5".
Is this enough length?
I could possibly push it as far as 4" end to end if I must.
It also seems that the Watts arms should both be at the same angle and length to work properly.

With my lower suspension arms set level I get about five degrees on the axles.
I know they need some angle for the U-Joints to work properly, is this enough?

I am surprised to see how low several suspension components will sit, bottom of the watts link and the diff in particular.
I will have to measure the low points of the old live axle for comparison.
I've had issues with the front of my frame and "Speed Bumps" in the past.
Clearly no off-road action with this suspension and tires!


At these prices I want my gas 100 octane, leaded, and my windshield washed!
     Thread Starter
 

7/28/2014 11:21 am  #48


Re: Hi, I have two IRS projects to work out.

I guess I am going to chicken out and use the 3.31 open diff insted of the 3.54 posi.
The posi housing is the very early type that uses different calipers which I do not have an easy source for.
It would also require me to turn a lot of RPM at cruising speed with my 27.1" tires and 1.1 top gear.
3.31 is not a LOT better but is close to what I have now.
If I can locate a set of early calipers I could always put the 3.54 in for hill-climb days.

Defineitly looks like I will want my 327 instead of the 350 since it's going to get wound up pretty often.


At these prices I want my gas 100 octane, leaded, and my windshield washed!
     Thread Starter
 

7/29/2014 7:23 am  #49


Re: Hi, I have two IRS projects to work out.

What is wrong with the existing calipers?  I have a series 1 jag rear and I don't forsee a caliper problem.

I've always thought the 283 & 327 were under-rated.  If you're going wind up an engine, it is easier to wind up a smaller mass than a larger mass.  Then again, I'm the one taking a 348 to a 431, mostly because I couldn't find a quality crank without going large.

 

7/29/2014 10:59 am  #50


Re: Hi, I have two IRS projects to work out.

I do not have the old calipers for the 3.54 diff and they are different than the newer carriers.
I need to find someone to put the posi from the 3.54 into the 3.31 case.

327 is s shorter stroke than a 350, less piston speed and free revving.
To build a 7000+ rpm 350 is big money, 327 will cost less and live longer.


At these prices I want my gas 100 octane, leaded, and my windshield washed!
     Thread Starter
 

7/29/2014 12:28 pm  #51


Re: Hi, I have two IRS projects to work out.

The posi from the 3.54 will fit just fine into the case.  Setting up backlash and pinion depth is time consuming and annoying for anyone not a speciality shop.  I ended up having Mark Williams change replace my 19 spline carrier with a 30 spline carrier.  Any gear ration from 2.88 to 3.94 will fit on the carrier.  Mine used to be be a 3.31 and is now a 3.54.  If you were going to a 4.11, you'd need a different carrier size because the inside diameter of the ring gear changes.

Regarding your calipers, I would expect most any calipers designed for a 10.3 inch rotor could be made to work.  Might need an adaptor plate for bolt hole alignment, but 1/4 or 3/8 inch plate could be made into an adaptor.

If you have a friendly parts store handy or time on your side, you could use the following information to find a caliper in a similar size.  EBC makes aftermarket rotors for Series1 & 2 Jag rears (and fits many others).  Their rotor part numbers are: GD239 or USR239, different finish is the difference.
The part numbers for the brake pads are:
Red (DP3101C) or Yellow (DP4101R)

Here is a link to their catalogs to see what else those part numbers apply to:
http://ebcbrakes.com/catalogs/

Just do a search on either of those part numbers (3101  or 4101)

Last edited by 303Radar (7/29/2014 1:20 pm)

 

8/01/2014 12:49 am  #52


Re: Hi, I have two IRS projects to work out.

A step forward always seems to be followed by a step back!
Got a quote on putting the posi from my 3.54 diff into the 3.31 case.
$350.00 plus an install kit ($?) and the 3.54 R&P become useless unless I pay another $350.00+ to have them set up on the open carrier.
Not likely anyone would ever want to use a 3.54 open diff!
The 3.31 is really still a bit low for long distance driving with a 1.1 top gear, 2.88 gears are easy to find but are a slug for around town.
So now I am interested in a factory optional 3.07 with posi center section.
Way back when I first joined this group there was a southern California dealer in Jag parts recommend in one of the threads.
I just spent hours trying to locate that post with no luck.
I did contact them way back when and their pricing was pretty reasonable for an entire rear with posi.
Just the center section should be even less, and much cheaper to ship.
Anyone know who I am talking about, and how to contact them again?

I also thought I had decided on a lower Watts link set-up.
Not thrilled with how low to the ground the lower end of the Watts would be.
While poking around some other threads here I cam across one with a forward link inclined inward to match the pivot point with the inside of the LCA.
For some reason the thought of making that link also act as a low mounted anti-sway bar popped into my head.
Also re-read the old pinion angle debate thread, and the negative camber gain vs LCA angle thread.
So now I have more design thoughts to ponder before I can complete my install.
Looks like I will be lowering my rear static ride height too for several reasons.

Going to have to clean-sheet of paper this, one more time. http://cdn.boardhost.com/emoticons/errr.png

At least my basic mounting scheme still looks good to me.


At these prices I want my gas 100 octane, leaded, and my windshield washed!
     Thread Starter
 

8/01/2014 8:37 am  #53


Re: Hi, I have two IRS projects to work out.

Randy's Ring and Pinion has a good install kit with the crush sleeves, bearings, shims, and other good to replace parts. I think it is in the 75 - 100 dollar range.

 

8/02/2014 6:15 am  #54


Re: Hi, I have two IRS projects to work out.

Richard/SIA wrote:

A step forward always seems to be followed by a step back!
... So now I have more design thoughts to ponder before I can complete my install.
Looks like I will be lowering my rear static ride height too for several reasons.


Going to have to clean-sheet of paper this, one more time. http://cdn.boardhost.com/emoticons/errr.png

At least my basic mounting scheme still looks good to me.

Boy - do I hear that!  Been round and round - but finally settleing in on my projo.  I'm way behind on posting - but will get some this weekend when it rains...

Cheers - Jim
 


UNDERCONSTRUCTION! Highly Modified C3 Corvette
         Dual Wishbone IRS w Subframe + Custom Uprights
 

8/06/2014 10:22 am  #55


 

8/07/2014 7:19 am  #56


Re: Hi, I have two IRS projects to work out.

Here is a picture with the dealer you might be looking for:
http://imageshack.us/a/img812/1424/6qwq.jpg

 

8/30/2014 12:05 am  #57


Re: Hi, I have two IRS projects to work out.

Half-off at P&P for the holiday weekend. http://cdn.boardhost.com/emoticons/happy.png


Got a chance to look around at a few cars they have. 

Lexus LS400 diff looks almost like it was made for exchanging into a Triumph except that it has an odd guibo type joint on the input. 
Appears to be an open diff. 

Porsche 944 trans-axle can be had for under $100. 
Interesting, but a lot of work to make it fit and deal with the torque tube. 

61 Pontiac Tempest rear complete, another interesting engineering exercise. 
Flexible drive-shaft (Really!) and an American made trans-axle intended for a front mounted engine.
Not sure  but it may be a three-speed. 

Nissan 300 ZX diff, appears to also not be a posi but not too hard to make work. 

'96 Ford T-Bird, diff is not as large as I feared, not posi. 

CL ad has a Supra posi diff for $200.00 
Not sure of the ratio or miles but I know they have been adapted to Spit/GT6 often enough that I think there is a kit available. 

Found five Merkur's in semi-local P&P yards! 
Rear is very similar to T-bird but a bit lighter. 
Also found an Escort GT twin cam parts car locally, not sure if the disc brakes can be adapted to the Merkur hubs? 

So I have until monday to decide what to use for my GT6/Buick V6 and T5 IRS rear build.


At these prices I want my gas 100 octane, leaded, and my windshield washed!
     Thread Starter
 

9/01/2014 1:47 am  #58


Re: Hi, I have two IRS projects to work out.

Some actual progress of the "I bought another part" sort.
Got a Merkur complete manual trans rear today.
Open diff, not posi as the web info postings call for.
Aluminum carrier and smaller than a T-Bird 8.8 unit.
Some web threads suggest that a GM 7.5" posi can be made to fit.
Ratio is 3.65 which I believe is what the web claimed and should work well with the T5 OD.
Anxious to do some measuring and have another look at the thread on the Sideways Technology forum which gives some clues for how to fit it.

I know I will have to fabricate uprights and "A" arms, the current trailing arms plus axles, are HEAVY and 10" too wide.

I will try to get decent pics from the start once I get it cleaned up.


At these prices I want my gas 100 octane, leaded, and my windshield washed!
     Thread Starter
 

9/01/2014 9:14 pm  #59


Re: Hi, I have two IRS projects to work out.

GFinally got a Merkur rear from a manual trans car.
Posted lots of "Before" pics in the import IRS pic thread.
I will need to "Uncage" it similar to what is commonly done for a Jag.
I may be able to use the center of the original cross-member diff support for my install.
I will be looking for some shorter axles, making my own control arms, and my own uprights.
At least the outer carriers are a "Bolt-On" design.
Looking for Euro-Ford bits to convert to disc brakes.
Coil over shocks are about all I will be able to just buy locally.

http://www.specialinterestarms.com/DSC01066.jpg
http://www.specialinterestarms.com/DSC01067.jpg


At these prices I want my gas 100 octane, leaded, and my windshield washed!
     Thread Starter
 

9/03/2015 9:55 pm  #60


Re: Hi, I have two IRS projects to work out.

Actually back to working on the Trick-6 suspension again, on paper.
Merkur info is hard to get in the U.S.

Silly stupid question, how do you measure a velocity jointed axle for length?
Just the shafts end to end?
How is the CV measured to calculate for suspension design?
Anyone here good at VSusp?
I need to know how to change the track width in order to begin modeling my design.
Other suspension modeling software that is cheap or free?

Last edited by Richard/SIA (9/03/2015 9:56 pm)


At these prices I want my gas 100 octane, leaded, and my windshield washed!
     Thread Starter
 

Board footera

 

Powered by Boardhost. Create a Free Forum