How to "narrow" my IRS suspension ?

I've seen 3 different ways to narrow irs trailing arms- 2 modifying the outboard end and 1 cutting/repositioning the inner mount. Check out Mango Smoothie's build blog, as he narrowed his by cutting the whole outer end and repositioning it. I've also seen the stubaxle bearing housing cut loose, repositioned and then welded back in.  We've talked about this before, but I don't think pics have ever been posted. There's also a Hot VW's article (June '94? I'll check) that details cutting loose and repositioning the outer bearing housing method. I'll see if I have time later to scan and post it. Al

I'd like an added 1/2" clearance either side on my CMC w/ 5 1/2" 2L 914 Fuchs too.  Here's article I bookmarked on SAMBA.  Not easy for only 1/2" though.

http://www.thesamba.com/vw/for...44869&highlight=

And here's a place that sells 1" narrowed trailing arms for $250 (w/ exchange core arms) and then you just need new axles.

http://www.thesamba.com/vw/cla...etail.php?id=1454603

http://www.mooreparts.com/3259-AC525202/

The 1" either side would be perfect for me since I could then add rear disc which would take back 1/2" either side.  If 1" is too much a wheel spacer could be used to make it less too. Axles from a T3 automatic (Left side) are 26mm shorter and can be found too.  Suspect buying new Empi axles at $120 each would be easier than finding 2 T3 used ones.

More info here:

http://www.thesamba.com/vw/for...wtopic.php?p=2840603

Some pics- same method as described in the Hot VW's article (which shows 26mm, or 1"). It seems that Aircooled.net has narrowed them 1 1/2". To read the full thread- 

http://www.thesamba.com/vw/for...44869&highlight=

Bruce- How wide a tire are you going to use? A 205 or 215 would be pretty cool!

Bruce - before going through the work & expense of narrowing your track width, check with Kirk at Vintage. I had Kirk put 5.5" wheels so I could run 185x60 tires. He got my fake Fuchs with proper off-set to accomplish this (tire-fender clearance = 3/8". 

I would recommend getting the rear wheels only with this off-set Kirk uses. Keep the standard wheel spec for the front wheels.

Might be worth considering before venturing into the process of modifying your existing suspension. 

(Click on pics for bigger & sharper pics)

Wheels = 5x130mm 5.5"x15"    Tires = 185x60x15

CIP1 has replica 5 1/2"x15" Fuchs with 5" backset for $129 each (also 3 3/4 " and 4 1/8").  Any idea what it is on yours MUSBJIM? 5"might be too much?

 ACC-C10-6649 - 911 FUCHS STYLE 5 SPOKE ALUMINUM WHEEL - FULLY POLISHED - 5.5 INCH WIDE X 15 INCH DIA. - 5X130MM BOLT PATTERN (5 INCH BACKSPACE) - CENTER CAP AND HARDWARE SOLD SEPARATELY - SOLD EACH - (A20)

Greg - I'm not sure what they are. Kirk has used these replica Fuchs on a few of his other builds. Also, I think these are less expensive than CIP1. These were only a few dollars more per wheel ($25 ?) than the chrome wheels.

Al....I originally had my heart set on exactly 205 or 215s. But I got such a good deal on the EMPI GT 8 spoke ($25 each and new in the box) I couldn't pass it up. Now I find that I would like a bigger patch on the pavement.....Bruce

With an offset of 45mm the replica Fuchs will give you enough clearance to install at least a 185/65 tire.....maybe a 195.  Anything wider would probably not clear the fenders, but who knows.

You could buy the replica Fuchs and sell your GTs.

Years ago when I was looking for tires to mount on my replica Fuchs (American Eagle 6.0" wide, with a 37mm offset), I paid $15 for an old 195/60 tire and had the shop mount it on one of my wheels.  I then mounted the wheel/tire to the front and then to the back to make sure it cleared everything.

It did....sort of.

I made the mistake of not mounting the wheel/tire to BOTH sides in the rear.  I didn't realize that most speedsters don't sit perfectly centered on the VW pan, so the tire cleared the fender on one side, but it rubbed slightly on the other.

After driving around for a day on my new tires I realized one of my rears was rubbing on the fender and had to exchange them for 185s.

It was an expensive lesson.

Bruce- 205's or 215's will change the way the car handles; there's a reason Porsche is putting huge tires on the backs of their cars for the last few years. It's worth doing. Al

Yeah - when I was running 225's on the rear, I could not get the rear to break loose, even pushing it really hard on a track.  I was running 7" wide rims (Fuchs) on the back then.....now I'm running 6" rims and 205's all around (long story).  It still is really sticky. 

The problem with these cars is the front end is so light it loses traction easily. I have gotten in trouble while braking hard.

Now you've just got me curious; you have to spill it now! If you write it I'll read it!

Are you running the same tire/wheel sizes front and back? What do you have for brakes? And I know this sounds counterproductive, but what about adding 40lbs. up front?

I think a lot of owners forget that rear drum brakes are not self-adjusting. For once "junk in the trunk"may not be such a bad thing.

I've often wondered about the possibility of adding some weight up front as well.  Anybody done it?

Lane- I've read about guys autocrossing with buggies doing it; there's a guy on the Samba that had 40 or 50 lbs. (I think) bolted to the front axle.

Al asked;  "Are you running the same tire/wheel sizes front and back? What do you have for brakes? And I know this sounds counterproductive, but what about adding 40lbs. up front?"

on Pearl until 2010;  

Front:

wheels:  16" dia. By 6" wide Fuchs (original) 

tires:  205/55-16. Continentals rated for 140mph

anti-sway bar:  19mm (3/4") from CB

Brakes: "Karmann Ghia" conversion from CB, Super Beetle Master Cylinder

Shocks: Koni adjustable for a 1969 VW sedan

Rear:

wheels:  16" dia. By 7" wide Fuchs (original) 

tires:  225/55-16. Continentals rated for 140mph

anti-sway bar:  19mm (3/4") from CB

Brakes: Drums from a 1971 non-Super Beetle (10 lb. residual valve)

Shocks:  Koni Adjustable for a 1969 VW Sedan

Suspension: 1969 VW Sedan, dual-plate, IRS, custom CV axles 

Front of the car has the battery, several tool/spare parts bags and a full size spare, along with the usual VW sedan gas tank (7.5 gallon?) and that's it.  The front end has never felt "light" at speed.

In late 2010 I swapped the rear 7" rims for a pair of 6" and am now running Michelin 205/55-16's all around.  Not as positive feeling in extreme cornering, but still pretty damn good and I'm getting too old to try to see if the rear will break loose on the track.

gn

You could do what some 'outlaw'(these guys are "run what you brung" amateurs that do not like all the rules and regulation and expense involved to race NHRA)  drag racers do and use 25lb sand bags.

Maybe try adding one bag first, centered in the front of the trunk, ideally if your battery isn't there the well would be a great place. Test the car and if more weight is needed add some...just a thought

Gordon- Why did you lose the 225's and 7" alloys for 205's and 6's?

Al:  Ever since I first got Pearl on the road I had been bothered by an intermittent rumbling at speeds between 65-72mph.  I tried just about everything to solve it over the years, racking up over a Grand in wasted short and long shots, some of which might have improved things, but probably just masked it.

Swapping out the 7" rims for 6" as I had on the front, made sense because now it was easier to swap wheels around corner to corner to see if the rumbling followed any particular wheel.  BTW:  At a sustained speed of, say, 70 when the rumbling was most pronounced, it was NOT constant, but came and went on a semi-random period, making it even harder to find.

Also, going to the same wheel/tire size all around allows me to rotate wheels now - I never could before because the rears were pretty big.

Once I had my transaxle rebuilt with a new ring and pinion and differential, all of the rumbling went away.     All that stuff I did (I had all of the wheels balanced at least 8 times along with a lot of other stuff like suspension mods, tires, you name it) never would have found the real cause, but "What'cha-gonna-do"?  At least it's gone and riding smoother than ever.....

Good to hear you solved the problem; too bad it took so long and cost so much. I know how frustrating it is when you can't seem to pinpoint an issue. Possibly a worn side and/or spider gear; that would produce your on again/off again symptoms.

Yeah, there are advanatages to running the came wheel/tire all the way around, but wider rubber on the rear anchors these cars so well!!

For optimum handling picking the correct sized tires for the front and rear is hard to do.  When cornering on the track you're flat out and I've always liked dialing in just a bit of under-steer, to be on the safe side. 

Running a much wider tire in the rear may be a good compensator for the extra weight in the rear, but it also may stick too much and cause the car to under-steer when cornering hard.  A little under-steer is great, but a lot is not.

Ploughing through a corner is no fun.

One thing that I wish was available for our cars is an adjustable front and rear sway bar.  Adjustable sways allow you to fine tune your setup.  When I tracked my Miata I could change my handling from slight over-steer to slight under-steer just by moving the connecting bolts on the rear bar one space in or out.

The suspension geometry on these cars almost forces them to have a degree of front understeer so you always come into a corner and start to "plow" your way through.  The fact that there's so much weight in the rear, as we all know, can convert that understeer to oversteer, sometimes in a heartbeat and when you least expect it.  the trick is to get the suspension balanced and set up for what you want to do.

What I found with those big 225's on the rear was that you could control and feel how much understeer there was simply with your right foot.  Come into the corner and feel the expected understeer and then start applying throttle (rather than backing off and making things worse) and you would feel the rear stretch to the limits of the sidewalls and "stick".  From there you could, if the corner lasted long enough, play with the throttle and feel the steering go from under through neutral to oversteer and back just by playing with your right foot.  Playing like this and steering through a corner with your right foot was pretty cool, believe me!  Corner times were pretty quick - significantly quicker than a club member's Cobra.  Pearl actually handles a bit better than the Dune Buggy I auto crossed years ago.  All I need in her now is a "Driving Brake"!!

Gordon---glad yo solved your rumbling problem.  I also had a rumbling noise that seemed to come from under my feet.  Turned out to be a very shot wheel bearing.  I drove it all the way from DC to Hot Springs, Ar with the sound.  The bearing was pretty shot by the time Russ and I 

changed it and the one on the other front wheel too.

So a noise someone would describe as "rumbling" can be more than one thing.

http://vwparts.aircooled.net/W...ble-OTT-p/bwf8xz.htm

They have an adjustable rear bar listed but it's for a swing...

Same wheel and tire size all the way around. I thought about a cement bag before doing a canyon run but Donna would not ride with me anymore if I went too fast. Sooo... perhaps a cement bag and a blindfold would do it.

also... I'm on a diet, and, if that works out I'll have even less traction...

Al, thanks for that link.  I really dislike the standard sway bar for our front beam.  That looks like a huge improvement.

Gordon, I originally set my track Miata up to over-steer, so I could get that 'tail-out' feeling while cornering.

Unfortunately, it didn't take me long to experience that 'tail-out-tail coming around' feeling.

Once the rear end gets past a certain point things happen REALLY fast.  After a high speed, ball-squeezing, heart stopping spin I went back to the pits and dialed in a bit more under-steer.

The small track that I did most of my driving on has a cement wall on three of its eight corners.  Make a mistake on those three and it's going to get expensive.

Good info here...I'm glad I asked the question. i'm more of a techie/tester guy and have limited experience in the driving nuances of these cars and others. Over-steer and under-steer escape my understanding so let me try to explain my concept of this under-steer/ over-steer as I think it applies to my car.

I have a ZF limited-slip differential and lots of power from my 2110cc engine and (I think) not enough rear tire traction footprint, (the rear tires break loose way too much when I stomp on it in a corner) So what i feel like is happening is when I stomp on it, the rears break loose but at the same time the front tires don't respond to where  I'm steering it or where I want it to go. It's like with both rears digging in, it wants to go straight in a line lined up with where ever the rears  are aimed. Is this under-steer ? I have already swapped ends twice in a giant parking lot.

I feel like i need to get a bigger (read bigger tires here) footprint on the rear to take advantage of the power to the ground aspect but still have some directional control.(not SOME  but SAFE directional control) What do you guys think ?

This road handling stuff is, by far, the most difficult for me...........Bruce

Seems to me that an oversized gas tank would solve a few problems at once, or at least help the front end drift when full.  I had to do a panic stop this summer and the road was full of little rocks.  I just slid like I was on ice and hit the car in front of me.  Luckily it was a Prius, haha.  A new front bumper was on my to-do list luckily and it came out awesome. 

Bruce, you should never...ever apply power while going through a corner, unless you want to practice your drifting.

All the speed should be done before you enter the corner.

When you hit the gas while going through a corner your car will want to go straight, not around the corner.  If you have lots of hp you can get the rear wheels spinning and create over-steer (back end comes around).

The only car I've owned that would over-steer at will on a track was my V8 powered Miata.  In second gear, going through a tight corner I could, with a stab of the gas pedal, smoke the tires and pretend I was the drifting king.

I only tried this on low speed corners.  With high speed corners it was foot off the gas when I entered the corner, hit the apex, and power on the way out.

I don't think extra weight in the front would have helped you in this case.  Braking with gravel on the road is like braking with ice on the road.

Years ago I was really moving through a corner in my Miata and hit some gravel.  In a second the car drifted across the center line and I almost went off the other side of the road.

Scared the crap out of me....thank goodness no one was coming in the other direction.

After that, I kept my flat out, bonsai driving for the track.

I usually squeeze the power on, gently, somewhere after the apex, depending on speed, gear, severity of corner, and degree of A$$h#le of the driver at the moment.

Sometimes I slam the pedal down pre-apex knowing full well what is gonna happen. And sometimes it is sheer poetry, other times it is a pucker moment!

3rd gear, mid rev range, pucker! 2nd gear, mid rev range, just a bunch of fun. Roasting the tires in 1st, what child can resist?

But yes Ron, fast in, hard on the brakes while still straight, turn in, steady state throttle, apex, then squeeze on the throttle and track out(to the rumble strips)! Then it is "well done"......

Yes, that's understeer. First, by applying power in the corner, you are shifting the weight rearward. This reduces the weight over the front wheels so they have less traction and thus less ability to turn the car. This also increase the grip of the rear tires.

Second, the ZF (clutch pack) LSD under power wants to make both rear wheels move at the same speed. But in a turn, the outside wheel must move faster and the inside wheel must move slower. When the LSD counteracts that speed difference, it makes the car want to drive straight instead of turn. A Torsen style (Quaife) torque-biasing diff on the other hand has less influence on oversteer/understeer and acts more like an open diff in a turn.

When you "swap ends", that's oversteer. When you lift off the throttle or brake in a turn, the weight shifts forward reducing grip at the rear wheels. Less grip makes it easier for the rear tires to move sideways. At the same time, you've increased grip on the front wheels which makes them turn the car more than they were before. Combine this with the higher inertia at the rear of the car from the rear engine and the rear end wants to swing out more quickly and farther than other cars. I.e, you spin out easily.

Larger rear tires will actually tend to increase understeer. But may be desired for the increased rear grip.

You didn't mention it, but if your car is a swing axle without a camber compensator, the jacking effect of that suspension in a turn will reduce rear grip as well making it even easier to spin out.

Justin....Thanks for the explanation. I guess there's a lot going on simultaneously when I'm turning, accelerating or decelerating. Weight transfer etc. I really like this car but it has already scared me a couple times. I've been going over to the parking lot at Santa Anita horse racing track here locally to play a little. The first time was after a rain and at night and got to feel drifting a lot. Next time was dry pavement, that was very different and more scary. I gotta cool it for a while now as their Security may be looking for me to come back.

On my sand buggy I could play much easier and learn to read these differences easily but on hard pavement it is much faster and violent. I already like the IRS better. It feels more flat and stable. Especially since i put a slight negative camber on the rear wheels Sway bars?? I have them but I have no idea what difference they actually make. Maybe i should take them off and see what it's like that way first. Anyway...Thanks to all of you for your comments. I really appreciate your input. i really like this forum.......Bruce

Bruce- Disconnect the rear sway bar mounts at the ends, drive it a little, and then connect the mounts again, and tell us what you think...

PS- Was the stuff I sent you legible?

Al...Yes it was...Thanks.....Also I talked to a guy at Hot VW and they are to sen me a couple articles as well....Bruce

As ALB mentioned, if you've got a rear anti-roll bar, disconnect for testing. Doing so will increase understeer/decrease oversteer.

Wider rear tires may make it a more progressive breakaway. Not sure how much you'll gain with the width you have to work with.

Your LSD, when you do break the tires loose, it's more likely for both tires to spin and get the rear end hanging out. It's why actual drift cars need them. If you had an open diff, when you do the one-wheel-peel, the other wheel gets no power so it'll maintain grip longer. I.e, it's more difficult to power oversteer than with an LSD.

It's good you're actually testing the limits of your car. Most people don't so when they do go over the edge they panic and make things worse. I feel a number of accidents could be prevented if everyone was able to experience the handling limits of vehicles back in driver's ed.

Just taking a 2-3 day drivers course will really change your perspective on driving be it in your daily driver or on a track. No matter how good you think you are, no matter how long you've driven you'll learn things you didn't know, especially about the bad habits you've acquired over the years, etc.

I'd recommend taking at least one course especially if you every once in awhile 'hi-ball' your car...just saying