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So, did you buy those?
WestLogic© at it’s finest.
I know the monoculture of Audi forums states that we must not deviate from known truths. But sometimes we must westlogic our way to new levels of B8 performance.
If I did this now, my only choice would be BBS CH-R 9.5" width front, 8.5" width rear. I want to wait and see if BBS FI-R comes on the market later this year in the Audi application. On the front in particular, it would be great to have a ultra lightweight wheel because I have so much brake hardware up there.
The more I think on this, the smarter it seems. Take strain off the rear brakes. Reduce drag with a narrow rear tire. Gain the extra thermal mass for the fronts which are doing all of the braking and all of the turning. The fronts can easily swallow a 265 with -3.0 camber, but the rear bumper is almost peeling off from a 255 cup. And go to a taller tire by 4/10".
Given the small variance in tire diameter, and the fact that the wider front tire may be stretched over a large wheel, you may net out very close to even front/rear rolling diameters.
The only oddity here is the “why” behind the need to run different widths when you have all the adjustments available to account for handling disparities that you’re trying to solve for. Spending more money to do it this way, rather than use the upgrades you have available is just a different approach than I’d expect. I am not flaming you, I am simply questioning the thought process.
A wider tire/wheel/offset combo on the front axle introduces a different scrub radius, and the varied track width front to back is going to have implications on handling (in this case, it would be more mid corner understeer on power). If you wanted more mid corner understeer all along, there were way easier methods in accomplishing that. In addition, one can fit 275’s on all 4 corners without rubbing for track use-- 18x9.5 wheels with 275 RS3’s have been done before. With that in mind, I do not see a reason to run staggered if you can run equal widths all around. Also, if one is not competing, I really question the aero drag arguement. One needs to develop a lot of notes and testing to determine that a reduction in mechanical grip at once axle is advantageous given the difference in drag. AND–those aero advantages are only valid at very high average speed courses. FWIW my avg speed at Mosport is something like 155kph or so (going off memory here!)–and that’s supposed to be the 3rd fastest track in the world. Drag matters there, sure. Other places? Nope. And drag is really a concern if you are racing under a governed rule where each car has to run an inlet restrictor–so you’re down on power. You don’t have any of these restrictions.
And lastly, the car is only as good as the worst axle. If you have reduced grip on one end, you will always be operating under reduced grip, as you will always need to compensate for it, and the limits of adhesion are always going to give up on that same axle–yielding a compromise in driving and handling. You already have decently high rear spring rates on an axle with near 1:1 motion ratio. Adding more rubber up front in my mind is only yielding you 1 single advantage that no other adjustment you have can be made to account for–and that is increased grip under braking. That’s it.
Also, look under any awd redline world series time attack car. They run square setups for the reasons I mention above. Trust the guys who document this stuff and test these things furiously. These are full aero cars which still choose to run square setups. If you’re concerned about aero, throw on some fender flares and canards infront of the wheels. Stick some air fences where the wheel portrudes and connect it to the splitter etc etc.
West why are you not running slicks? Are you driving there and back on the same tires is that why? So much more grip and better feel…until they let go
@boro if you’re rotating tires constantly, and it’s the fronts that are wearing out at twice the rate, isn’t the front under tired or the rear over tired?
It isn’t that simple. It depends on how the tire is wearing, where the wear occurs and the operating temps one is taking the tires to on the track. The reality is this car eats tires due to the weight. However, my tires wear quite evenly - and on one tighter circuit, I got more wear out of my rear tire than my front tire. It also depends on how one is driving the car, and how much rotation the car is yielding.
That said, it is expected for any front engined street car–even a track prepped one to eat the front tires first, because most usually, a driver is going to want some form of understeer–even if it’s very mild. As that inspires confidence.
Pushing a car mid corner on power while it’s understeering and cranking the wheel over is going to eat the front tire regardless of size. It is not a “heat capacity in the tire” thing. That would be a driver error thing. I’m not suggesting that you are doing this, but my point is that there are many variables here.
I have no problem with managing the front tires, but everyone knows the front brakes and front tires take all of the beating. I know everyone wants to be cool and pretend they have a rear engine Porsche, but the reality is our cars have more in common with the A3 than the 911.
Skywagon is a fucking idiot for putting wider rear tires on. TBD, but I may be the smartest man alive for properly tiring the fronts.
Hi West,
Boro92 has some excellent track experience. He is the type of person I try and listen to when getting car setup advice. Its been hard reading this thread without trying to reinforce what he is saying here because you may be overlooking some of his sound advice.
First, you won’t be the first person to “properly” size the front tires. Square 275 setups have been run on the B8 S4 before so running a 265 or larger up front is not a first. I also agree to go pretty much as wide as you can go on these heavy cars.
Second, and very importantly, is that there is no need though to go smaller in the rear. I would try and run a square 265 or 275 setup. You are not the first person to think of running a reverse stagger.
I’ve run a reverse stagger on my SI track car that weighs 2700lbs. Its FWD with an LSD. I have run a 255/225 setup on it and…never again. This can really introduce some nasty handling dynamics that are hard to tune out. It’s simply not necessary. Now I run a 245 square setup and next season a 255 square setup on this 2700lb car.
Can I get the rears heated up in my front heavy FWD car? Nope. You never will be able to in this car either. But going down to a 225 in the rear or even 215 in the rear may help them get heated up but it also made my car snap oversteer to the point I had some unrecoverable 180 degree spins. What I am saying is that it just didnt help any.
The point is that if you want your car to rotate, you can already get your car to rotate even to the point it is darn dangerous to drive and you dont have to touch the rear tires. You have adjustability in your suspension and alignment settings that already allow for this so why give up absolute traction by reducing rear tire width? You’re introducing another handling dynamic by doing the reverse stagger when not yet even taking advantage of the adjustability you currently have.
What I am saying is that it is really easy to “overmodify” a suspension (and yes, i consider tires as part of a suspension as well). Maximize what you have before reducing your rear traction ability, IMO.
Mike
West,
Here are some videos of one of our SI drivers that is really good. He runs a reverse stagger and I had setup my car after his. I can tell you that in his hands, it works ok, but it can be a very dangerous setup in the hands of others. This is a FWD car…
+1 Mike. Thanks for helping out with the recommendations XD
That video is pretty much what I expected. The guy is on the throttle all the time to keep the car on the track. It’s fast, but definitely scary. And going to be squirrely as heck under braking. Very entertaining to watch though!!! Problem is at an HPDE, traffic is less predictable. And when one is managing the back end like that, it is asking for trouble in some cases.
Do you still have that si track car? I’ve been considering building a track car… That was on my list.
an the SN95 mustang. Total opposites though.
hi boro,
Yeah, I still have it. It’s a really fun car. It’s dead reliable and it makes some very nice noises reving past 8000rpm. The aftermarket is pretty much endless and you can get into doing your own ECU calibrations (down to basemaps) and flashing as well pretty easily.
Its my first FWD car and I’m not as disappointed as I though I could be. The LSD is nice. Its a safe car to track. If I do bunch it up, I can walk away without feeling too bad. Its darn easy to fix though.
I am like you in that I also considered a Camaro SS for a track car. I’ve done Miata and Boxster. I’m thinking of trying a 335i xdrive for a next one. Their chassis is brittle as heck though. We’ll see.
mike
Good discussion.
Man, that Civic in the video looks like a hand full.
Thanks, guys. Maybe this car is done and I should move onto tinkering with the Boxster. I just don’t want it to be over.
I sort of have a hard time believing anything can be done to this car to make it unpredictable. I really don’t think an 11% difference in tread would turn it into some kind of snap oversteer monster. I think it would have a much more mild effect, and I hypothesize in the right direction (for me).
“Reverse stagger audi” is a search term with a lot of hits.
I’m using the 500 front spring and the 650 rear spring, but at the time I ordered they offered a 750 rear spring. I could go up to that.
A note from a shop I use for Audi tuning (more or less approximates what you guys said, except for the dangerous part):
West,
back to my original question. What handling trait are you attempting to solve for?
You are bouncing from staggering the tires to swapping spring rates etc. Those are all tactics to solve for a particular characteristic that you find undesirable. Is there a particular corner the car sucks in no matter how you set it up? Does the car behave a certain way under a specific driver input which does not suit your preferred driving style? You have videos for anyone to look at?
What would be unwise is modding for the sake of modding. You have a very well setup car, with many options available to you to tune things out. You do not even have to go down the route of swapping springs, as IIRC, you have yet to adjust your JRZ’s and run them very soft (!!!). Have you played with tire pressures also? Something as essential as a tire pressure can alter the handling dramatically.
I get out there with a street based coilover system, 245 street tires and an alignment–and I am very satisfied with how the car drives. My car setup as is, is already on par with, and even beating a lot of time attack class winners with what is essentially a stock car. The biggest thing is alignment. If you know what you are chasing down, maybe collectively we can provide input on adjustments.
Nothing really wrong with it. I’m going to go thrash it this weekend and will report back on Saturday night. I’ve got the new type 3 brembo rotors on there.
I could lighten up the wheels with FI-R and I’m considering how I might better enable the front to do all the work I’m asking. I also feel bad for the under equipped sliding caliper rear brakes.
Realize I’m already running 5mm spacers up front so I’m technically reverse staggered now and I like it. The front offset on a wider wheel might send the tire inward rather than out further, when the spacer is removed.
West, aren’t you running both your front/rear sway bars on the stiffest settings? trying less stiff in front or putting the stock sway on up front should reduce understeer from what I hear.
depends on what part of the corner you are talking about.
also, let’s bear in mind he runs a 600# rear spring on an axle that is near 1:1 motion ratio. coupled with an active rear diff, that is going to negate the need for a large rear bar.
Alsoooo West hasn’t identified what issue he is chasing down, so putting on a bigger rear bar may not make him any faster.
650 rear spring and motion ratio about 0.6 to 0.65
There’s no understeer even with the rear bar on soft. I’m trying to manage front tire heat (and rear brake heat) above all else.