Heim joint questions

In reply to Tadope :

There is nothing inherently wrong with struts.  Most double wishbone cars made today have a camber curve very similar to what you get from a strut suspension, because extreme camber curves lead to unstable roll centers, which leads to sketchy feeling handling. 

If you have good high speed stability, caster is fine and not something to be concerned about, IMO.  Yes yes you might get an extra .02 degrees of negative camber while cornering after a whole lot of work, and potentially screwing up your bumpsteer because you have changed the tie rod end height.  Not worth it.

Not sure why you want a tubular subframe?  Re: identify what you are trying to fix by making a change.  They are usually weaker and more crack prone.  They make servicing easier, and in some cases they make plumbing easier (thinking rear drive V8 cars with turbos) but they become a maintenance item.  Especially if they were engineered by the "looks cool" method rather than determining expected load paths and designing the structure to accomodate them.

I actually have a set of quality coils on my shelf waiting to go on the car.

the current china crap was basically just a shakedown test as im new to this chassis and wanted to learn from its weaknesses.  After selling them ill have only spent 50$ or so on them. Plus i learned a ton.

im taking info from u guys, but also a lot from dedicated mk1 tt forums. What ive learned is that the cars are massively front end heavy. And that caster and camber curve are two of the biggest improvements you can do.  
 

actually spoke to the owner of usrally who recommended fixing the strut camber curve.

So i been on a mission to lighten the front end.

also the tubular subframe raises the lca mounting point, which fixes roll center from lowering, and camber curve. AND reduces weight AND increases stiffness.

imappreciate your insight about using extenders with the heims however.

ill be extrmely careful with that.  I might leave it out. 
or if i use them, i can actually weld them directly to the arms with additional reinforcement.

might actually make the arms atronger than before.

I definitely agree that getting between -1.5 and -2.0 degrees of camber in the front, especially if managing to do so without excessive lowering, is a massive benefit with regards to front end grip on the mkiv chassis. And the more grip that the front end has the less that will be asked of the haldex setup. 

Spending a few hundred dollars to optimize suspension geometry for an application will actually recoup cost benefit within a season or two on the back end (from a cost standpoint) from optimizing tire wear. 

That said, moving the strut tops inward gives you negative camber and changes the camber curve.

(looks with disappointment at the cup and pillow style VW mounts)

If it were me, I'd move the lower control arm forward mounting point up and out. Which is one of the things I did on the one rx-7.  Did it help? It made me feel better...

In reply to Pete. (l33t FS) :

Yeah for sure.  You can get adjustable top mount that do that.   But its limited.

Hence the heim extender idea.  That way I can change the length of the arm at will.

But to be honest.  Tt track guys run serious camber.  Like 4deg.

I might have to do top mounts and the lca

Get a pyrometer to see if you need more than -2.0, if you're not running R compounds much beyond that likely isn't going to provide any benefit. 

Also never trust anyone else's setup if they don't have a pyrometer in the trackside toolbox. 

-4 is crazy unless you have narrow tires with tall sidewalls.

In reply to Pete. (l33t FS) :

I guess other folks could be full of E36 M3e. But pretty much every tt track guy I've heard from recommends 2.5-3.5.    Stock maxes at 1.5 if ur lucky 

In reply to Captdownshift (Forum Supporter) :

I'll be on rcomp eventually

Tadope said:

In reply to Pete. (l33t FS) :

I guess other folks could be full of E36 M3e. But pretty much every tt track guy I've heard from recommends 2.5-3.5.    Stock maxes at 1.5 if ur lucky 

What was their metric for doing that? IE, how much suspension travel do they have, what tires do they have, what pressures are they running, are they using flexible non-upside-down struts or Chinesium tubular control arms and subframes that flex a half inch under lateral load, etc.

Alignments can't be made in a vacuum, really.  Even the old standard of "1.5 degrees negative at the road" doesn't really apply as a general rule because low profile tires with stiff sidewalls may not really tolerate that kind of camber, and some tires are engineered to work better with less camber, and wheel width plays a role as well, and circle track might actually want -4 because of the soft sidewalls and relatively low pressures they might run for a given track surface...

In reply to Pete. (l33t FS) :

fascinating.

well the only answer is that its a collection of all of the above

and i know that 1.5 is not enough for sure.   Low grip up front, pushing.

ill keep in my your advice.   I never said i was planning on 4deg anyways haha.

tbh im really looking for caster most of all.

you can get more camber with mk2 tt balljoints or moving the top mounts in(as others have mentioned i think)   But caster is what tubular arms are great for

In reply to Pete. (l33t FS) :

In his defense, I'm seeing the same on some of the BMW track car builds too. We're talking quality builds with Ohlins level suspension, 200 TW or DOT-R tires, tracked frequently by experienced drivers, etc. Definitely more static camber than I expected, but they are apparently finding faster times and better tire wear as they continue into the -3.5 to -4.0 static camber range.

.

In reply to Tadope :

The 1-piece arms will only allow for a limited amount of adjustment before you start imparting bad loads into the arms and/or subframe brackets. As you adjust them away from their nominal position, the two bearings get farther apart... But the mounts you're bolting them into don't. Once again, no-bueno. This is why the 'uber-expensive' 2-piece race version exists. The main geometric benefit to the 1-piece arms, would be if the arms themselves are built with non-standard dimensions for more camber and/or caster with the spherical joints adjusted to their nominal position. 

In reply to Driven5 :

oooooh. Hadnt thought of that.  So the 2piece arms literally change their shape as they adjust

About the only thing that an E36 or later BMW chassis has in common with a TT chassiswise is an engine in the front and they have four wheel. That engine in the front isn't even the same layout. You cannot under any circumstances compare the suspension layout or setup between the two. 

Setting up a suspension and what tires you run currently, versus the future, is an evolution. It's why in the initial coilover thread I said buy a good high quality piece now instead of something that you'll be replacing later. Buy stuff once and buy it for life with the exception of tires and wear items or in the instance of having an off. And use a pyrometer to let you know what is needed next. Because you may find if you race to -3.0 or more that you're riding on bumpstops and it handles like crap. Or you may start with a setup that's negative -2.0 and find that, yeah that outer edge of the tire is not getting up to temperature, and more is needed. But you need to do it instead of speculating and saying but other people... Because other people are more ons doing stuff based off of what vendors that never go to the track are suggesting and what Barry in accounting who spent $6k on his setup but has never raced wheel to wheel are suggesting. 

Don't be like other people, because they are morons and sheep. And they're also driving BMWs and not TTs so they don't even know what they're talking about with regards to your platform. 

In reply to Captdownshift (Forum Supporter) :

That's quite the unnecessarily caustic rant. I only brought up BMW because there seemed to be some incredularity that a front-strut track car could possibly benefit from running upwards of -3.5* static camber. Nobody is actually trying to equate the platforms or how to set them up beyond that.

A lot of time and money can be saved over iterating from scratch by finding a starting point that at least gets you into the right ballpark. The people with the most current and active 1st hand experience setting up the Mk1 TT and Mk4 Golf/Jetta platform for track use will generally be as good of a baseline for him to gauge from as any.

Here is the thing about set ups: 

In general you can use other peoples set ups as a baseline; provided they are getting good results & using sound practices. There are a lot of marque experts who've done the leg work and so using their recommendations is a usually good place to start.

BUT

The "known" set up may not work for you as a driver. I can think of two examples of this:

1. Drivers whose limits are lower may not bring the car to the limit with the set up. -2 degrees of camber may work just fine for them where as -3 may cause premature tire wear with them driving.

2. Driving styles; I have a friend who is an excellent driver but he doesn't like a loose car. The supposedly fast set up for his car is very loose, he's much faster with the car set up neutral. He is a front runner.

In reply to Tom1200 :

And of course you can adjust and dial in toe in the front and rear to provide for additional oversteer versus understeer. 

In reply to Captdownshift (Forum Supporter) :

Yup; but I think the biggest thing we miss is the driver car combo as a whole.

Tadope said:

However. Pete_vr6 has realworld experience snapping them so thats unfortunate.  But drag launches are a level that I think outclassed any of these arms

We break everything but the stock stamped steel pos work just fine. Sometimes we add a 3rd member/traction bar to them to keep the rear bushing from distorting or just use a spherical rear bushing and weld the arms on the seams. 

Actually there was recently a post in the tt group on fb talking about how similar the e36 is.

Pics and all.

The rear suspension setup is almost identical.

And the front mac strut setup is very similar as well.

Heck I literally have e36 rear control arms on my tt right now, and I was considering using e36 front strut mounts.

In reply to Tadope :

The E36 isn't a short, nose heavy front driver, and the suspension geometry is a lot different.

In reply to Pete. (l33t FS) :

Yeah, their front CVs are a lot more resistant to extreme camber and arm length changes 

In reply to Captdownshift (Forum Supporter) :

I'm picturing how much negative camber the inside tire has with -4 static plus body roll, and how much acceleration grip the tire has coming out of a corner.

It isn't as much of an issue on a rear drive car because the inside tire on a rear drive car mostly just contacts the ground when accelerating out of a corner, or hovers over it if you have decent acceleration grip and engine power.  Front drive expects a lot from both front tires on corner exit, and the corner exit is the start of the straight.  Any loss there is carried and multiplied all the way down to the next corner.

Tt is awd

FWIW, it is very common to need -3* or more of static camber for race / track cars.

For reference, Spec Miatas typically run -3.5* static in front and similar in rear.