Lowering vs. Handling: TT Edition

[Murderface]

I looked into how much lowering affects the TT's handling and wrote about my findings, figure some of you might be interested:
http://audittmk1.blogspot.com/2009/06/tt-suspension-geometry-analysis-how-bad.html

My car as it sits now:
http://i102.photobucket.com/albums/m96/lmaoxfilip/ttlake.jpg

[auditech79]

This is exactly why i want a D3 A8, I would just lift the fvcker up when i drove. Air suspension FTMFW!!

[l88m22vette]

Good read Murder, you officially win because of the graphs with pretty colors:tongue:

[Warranty]

Nice filip. I love the way my TT feels with coilovers. I can only imagine how much stiffer in the corners it would be with an RSB.

[frostyflax17]

very good write up man.

i can' see the graphs here but i get the general idea from your narrations.

one question though,
when you say that a lowered TT has better camber than stock, does that mean a TT with say... a 1.5" drop won't need a camber correction kit at all? I always thought it would mess it up.

[Murderface]

very good write up man.

i can' see the graphs here but i get the general idea from your narrations.

one question though,
when you say that a lowered TT has better camber than stock, does that mean a TT with say... a 1.5" drop won't need a camber correction kit at all? I always thought it would mess it up.

This is regarding the front wheels...not the rears. You don't need a camber kit for the front wheels on a TT for street use...with a drop and adjusting ball joint mounts you can dial in over 1.5 deg (I think the ball joints give .5 deg of adjustment, I have 1.3 deg with no ball joint adjustment), plenty for street use.

[W3rkd]

There's no pop-up's and moving gif's I don't understand. Thanks I was curious about this before.

[l88m22vette]

The whole suspension conversation is different when you talk about TTs because the FWD has a completely different set-up than AWD (torsion beam vs. multi-link); this affects camber and what you can/can't do, specific lowering issues (FWD can go lower more easily), etc. I use more toe in the front (.15 vs. .08) which definitely improves turn-in. For AWD the only thing you need with lowering is a 1/2 KMAC kit for each side of the car, or a new LCA for each side.

[Murderface]

Again, the whole article is about the front suspension. You can actually tweak the rear FWD suspension as well...you can adjust camber and toe by shimming the stub axle. Don't really see a need to though.

[myslow1]

you officially win because of the graphs with pretty colors:tongue:

:lol: thats what i was thinking while i was looking at it hahaha!!!

I just have springs with a kmac right now :(

[LateApex]

In your blog you say " As you can see, surprisingly the 60mm lowered TT actually has more negative camber (!!!) than stock ride height up to 4 degrees of body roll. As mentioned before, this is generally desirable in a turn. Past 4 degrees of body roll, the OEM ride height starts to have an advantage that at most (at 6 degrees body roll) is a half degree of camber. So it looks like lowering doesn't impact the camber characteristics too badly."

I'm pretty sure this is only true if you start at -2.4* camber, the camber you might get if you lowered the front without an alignment. Obviously, anyone dropped 60mm would realign the suspension to a more reasonable static setting. If you assume -1.3* is a good starting point you would need to shift the 60mm line up to that point which would make the comparison with stock seem not so appealing. Lowering the car changes the lower control arm angle and negates a large portion of the suspension travel that induces negative camber as the car leans around turns, resulting in a faster move to positive camber.

[Murderface]

I'm pretty sure this is only true if you start at -2.4* camber, the camber you might get if you lowered the front without an alignment.

If you assume -1.3* is a good starting point you would need to shift the 60mm line up to that point which would make the comparison with stock seem not so appealing.

I think you missed that the -2.4 degree figure comes from camber with the wheels turned (camber increases because of caster) at ten degrees plus body roll taken into account:

http://i102.photobucket.com/albums/m96/lmaoxfilip/Suspension_Geometry_036.jpg?t=1244445079


Obviously, anyone dropped 60mm would realign the suspension to a more reasonable static setting.

Can't do much to change camber up front without a camber kit...all you can do is add negative camber by shifting the ball joint...can add ~.5 deg iirc (I can't find the exact figure anywhere, but I remember reading that a while ago). Wouldn't want to go any more positive @ a 60mm drop since right around there the camber starts getting more positive. Fortunately, for a full inch of travel at that point, the TT's camber only goes ~.1 deg more positive, which IMO isn't too bad.

EDIT: I left part of apex's post in here for some reason without quotes =\ whoops.

[LateApex]

I think you missed that the -2.4 degree figure comes from camber with the wheels turned (camber increases because of caster) at ten degrees plus body roll taken into account:

You are correct, I missed that your reference was during turning, not static. However, I think the relative relationships remain.

[keg225]

How is bump steer affected? If the hinge joint on the tie rod is a different lenght than the control arm lowering the car will greatly affect bump steer.

[Murderface]

I didn't notice any bump steer with my drop...I'm not sure about where the joint on the tie rod is positioned on the TT though. I'm going to guess it's a different length though since when I dropped my car then aligned it, it was toed (I forget out or in) .5 deg.

[keg225]

Bump steer was one of the major handling problems I found when building SCCA production cars w/ struts. The only way we could make it handle properly was to raise and move the pick-up points as close to the center of the car as possible. We also made sure the joint on the tie rod matched the pickup point as close as possible. If you put a strut car that has been lowered on bump steer plates and raise and lower it the bump steer is not good.

[Murderface]

So after getting new 18x9 wheels, cheap 245 width tires, raising the front of the car by like 1/2" and replacing front control arm bushings with a DEFCON setup, I took the car for a run on an on ramp with the accelerometer...

Holds 1G+ maximum G pulled was 1.13G

So what does that mean? That means shove it Vmaxx haters :P

[frostyflax17]

can you compare the g's to like stock... vs other springs?

[Warranty]

Yeah, I could run the G meter on my liquidTT and see how the Eibach coilovers perform under some Gs. I think my panzer plate might even help a little. I'm sure if I add a RSB it will be a little better.

[l88m22vette]

I'd bet money if you installed a rear sway you'd wonder why the hell it took you so long

[cheeba]

So after getting new 18x9 wheels, cheap 245 width tires, raising the front of the car by like 1/2" and replacing front control arm bushings with a DEFCON setup, I took the car for a run on an on ramp with the accelerometer...

Holds 1G+ maximum G pulled was 1.13G

So what does that mean? That means shove it Vmaxx haters :PIs this with an accurate accelerometer? Get some high-end Summer tires and post up the new numbers :ohmy:

[Murderface]

Is this with an accurate accelerometer? Get some high-end Summer tires and post up the new numbers :ohmy:

This is with a cheap accelerometer...but said accelerometer NAILS my quarter mile trap speed very accurately, given a flat surface. In 1/4 mile mode, it beeps when you cross the finish line, I always stare at the speedo/GPS to make sure the trap speed it reads matches how fast my car was actually going since this is a good indication that the time is fairly accurate. From what I've read, they're good to within a tenth of actual time.

It's probably accurate to within several percent...5% error would still be over 1G.

I'd bet money if you installed a rear sway you'd wonder why the hell it took you so long

Dammit, every time I go around a turn hard I wonder why the hell I don't have one. Would be so nice for the car to keep turning rather than just sliding the front... could probably pull even more G.

[Cincy]

GET MORE TQ! My ass slides around when making hard turns/uturns with no rsb. Going to wait till the new turbo goes on before i decide if i need one.

9" wheels with 245's? Should of got some real meats! 275! :lol:

[Murderface]

Haha I might go with 255s next time around...can't get away with much more tire without having to run poke (my tire is extremely close to the springs on my coilovers).

[Cincy]

whats your offset? Im looking at some 28's which makes them basically even with the fender. I really want to fit some 275's on there