[NickG]

Anyone interested in making a track car out of a TT, you should check out my blog:

http://audittracecarproject.blogspot.co.uk/

Been there done it..

I've dropped you a PM a couple of days ago regarding this mate, with a few questions regarding CSCC.

Cheers 8)

 

[Grahamstt]

I think you two ought to get a room

Hey, some actual useful and critical information from two highly knowledgeable people. Lets tell them to gtfo. :?:
I think a lot of people should be reading this quite frankly but eh. I'm glad this forum is getting more technical and less "he said she said".

It wasn't a criticism twas a tongue in cheek comment cos they are clearly very knowledgeable

 

[NickG]

I think you two ought to get a room

Hey, some actual useful and critical information from two highly knowledgeable people. Lets tell them to gtfo. :?:
I think a lot of people should be reading this quite frankly but eh. I'm glad this forum is getting more technical and less "he said she said".

It wasn't a criticism twas a tongue in cheek comment cos they are clearly very knowledgeable

Besides... They already have a room...

http://www.ttforum.co.uk/forum/viewforum.php?f=250

:wink:

 

[Madmax199]

Hey guys, I hope the exchange between Thistlebeeace and I didn't put you guys to sleep. I am the type that loves to stir the pot and invite people to look at things outside of the status quo. I kept the exchange going for so long because, for one it's not every day that I find people with the technical knowledge to analyze things with me in such depth -- and we are not really disagreeing but rather debating the practical vs theoretical aspects of using springs vs bars to control lateral roll. It is known that even in the racing world there are two school of thoughts when tuning suspension (more springs/less bar, less spring/more bar), and each approach can be made to work. What kept us going is that bringing the theories into real world application (which tend to look at ideal conditions), there are variables and design constraints that are not necessarily under the control of the formulas used to model the dynamics.

My thing is that beside grasping the theoretical aspects of things, I have a put a lot of practical time into specifically tuning the TT platform. My calculations and software shows the same data that Thistlebeeace has brought to the table, and if wasn't for the practice throwing a curve ball at the theories, there would not be a discussion. I hope you guys understand... and to be honest there is always something to gain from this sort of exchange.

So to put an end to this one, we'll say that bars and springs can both be used to keep body roll in check since lateral load transferred through the chassis could care less about what's being used. For the TT, it's design limits, and the less-than-perfect surface conditions in the real world we should conclude that:

1) too much springs will hit the practical ceiling of usable chassis Natural Frequency (let's say 3 Hz)

2) too much bar will have byproducts that are detrimental to overall grip

3) the factory bars (especially the front) are already pushing what's ideal for the platform

4) when having to compromise (not everyone have the means to test and draw their own conclusions), unless you're approaching high Natural Frequencies (again say 3Hz), it's advised to used springs to get better chassis roll control.

 

[NickG]

Not at all, there was a lot of quality information and theories... beats another "Will these wheels fit" thread [smiley=bigcry.gif]

In conclusion, what would run/are you running in terms of spring rates and ARB sizing Front and Rear then? For say perfect track conditions?

 

[Gonzalo1495]

Not at all, there was a lot of quality information and theories... beats another "Will these wheels fit" thread [smiley=bigcry.gif]

In conclusion, what would run/are you running in terms of spring rates and ARB sizing Front and Rear then? For say perfect track conditions?

Pretty sure he runs no ARB in the front and the stock 14mm bar in the rear with the adjusted hole for ideal conditions. I'm curious about the spring rates too however. :wink:

 

[Von Twinzig]

One of the problems I found was getting springs. Once on coilovers the fronts were not too bad, but trying to find short, stiff springs for the rear proved impossible here in the UK.

VT

 

[Madmax199]

In conclusion, what would run/are you running in terms of spring rates and ARB sizing Front and Rear then? For say perfect track conditions?

Well, this is a loaded question because what will work on a car with street tires (say factory width), is a world apart from what is ideal for the same car on race tires (especially wide one like I run). And there is no such thing as perfect road or track conditions. A cool experiment is to log the headlight leveling sensors with VCDS, they reveal a lot and can give a lot of insight into how much oscillation the chassis is seing. Below I also linked a video of my rear tire movement during a casual drive on decent road surfaces, it demonstrates how much there is going on even with what would be considered a stiff car.

Video of rear tire movement

I have tried many combinations of spring rates and bar rates over the years in my car. My final setup (with track in mind) is zero front bar with stock rear bar (needed or the springs would make me exceed what is usable in terms of rear Natural Frequency). My spring rate is 800/1300 lbs/in.

However, I must also note that I have more work than the average track TT, and that accounts for a lot with my "ideal" bar/spring selection. For example I run 315mm wide race tires, the front track is 2" wider than stock, I run negative 5 degree of static front camber compensation, the roll center geometry has been altered/raised to compensate for the effect of lowering, my dampers are valved to match the wheel rate, I have aero grip aiding the mechanical grip, my curb weight is 1,100 kg, etc.

With that said, although people tend to assume the car is as stiff as a rock, I till get a healthy dose of body roll when cornering. The car is still moving around when laterally loaded, and the suspension is still working....

Without roll center correction and 15mm US-spec R32 rear bar. Lots of body roll still with 650/1150 lbs/in springs

More recent with roll center corrected and factory 14mm rear bar (800/1300 lbs/in)