So I went out and won my first Novice AutoX (Dammit!). Now I'm in A stock (just read the rulebook, yawn) and don't have a clue as to what to do about understeer. I know about tire pressures and alignment (going to go to -1.5 fr and -1.0 rear, thoughts?) but is there anything else I can do to get the understeer under control? I know that I can change the front roll bar but not the rear but I don't know if that will do anything for the car. STU isn't an option right now as I don't have the moola.
Discuss amongst yourselves...
John

Lots of applicable threads below .... and in the 2.5 Forum ... I believe the JDM STI has a thicker from sway bar ... they put a thinner one on for the US since they figure we can't drive ...

Originally posted by makofoto
I believe the JDM STI has a thicker from sway bar ... they put a thinner one on for the US since they figure we can't drive ...

Nope they use to put a thinner one in the jdm sti now they put the same as the USDM sti.

Bigger front sway bar will reduce ultimate front end grip but will make the car transfer better and keep a better camber curve.

Shocks can help alot if you get them valved right, but since your a novice autoxer what will help most is to autox more.

tires, tires, tires, nice sticky ones :)
in A stock you can run r compounds, something to consider.... but.. since you are tlaking about money (or lack there of) it may not be good. most likely you will need second set of wheels, then tires, and looking at $1500 or so..

p-rex

Originally posted by afpdl

Bigger front sway bar will reduce ultimate front end grip

I don't agree with this...


-Matt

Originally posted by Watkinsm3
I don't agree with this...


-Matt

Pretty sure it does on an ideal chassy but since we lose camber with body roll its a bit tricky to find the ideal size bar.

Originally posted by afpdl
since we lose camber with body roll

There ya go! ;)

Originally posted by afpdl
its a bit tricky to find the ideal size bar.

It may not be fun... it may not be cheap...
Test... test... test...




Or you could just wait for someone else to do the testing and hope A) they'll share the info B) the info they share is accurate.


-Matt

Slow in, fast out. It is possible you're driving the car just right at one of your first events, but that doesn't seem to be usual in autocrossing. First, get a good alignment. Then work on driving. If you want to spend some money on the car, that's fine, but realize that you'll get more time from working on the driver.

I just did an autocross and rode in two other STis (who both ran novice last year). Their biggest problem was going too fast in the corners, leading to various degrees of scrubbing and pushing, which means they can't get back on the throttle coming out (they also didn't unwind and back off). I think corner exit is our car's huge advantage over the others, and if you're going too fast in the corner, you just push out on the exit which means you can't get on the throttle. This isn't the car, in my opinion -- heck, my loosy goosy Miata would do it if you went into a tight corner too fast. Number two for them would be looking ahead -- that cuts down on extrenuous steering inputs and exiting a corner pointing in the wrong direction.

I'm trying to be helpful. I found my stock STi with a good alignment to be pretty nice. It didn't rotate, but it did nice drifts under power. The only time I recall it plowing was when the driver (me) screwed up and didn't slow down enough for the corner. Amazing how much times drop when you can go just slow enough in the slow parts and fast in the fast parts.

Regarding alignment, do some searches. Didn't some of the national guys in WRXs run 0 toe front and some toe out in rear to help it rotate? Max front camber -- mine only made it to -1.2 stock. Obviously max caster.

camber loss due to body roll:

as the wheels move up in the wheel wells, they get MORE negative camber.

which is what happens to the outside tire

which is what you want, yes?


so why is there loss of negative camber due to body roll?

Originally posted by WRX_Mundi
Slow in, fast out. It is possible you're driving the car just right at one of your first events, but that doesn't seem to be usual in autocrossing. First, get a good alignment. Then work on driving. If you want to spend some money on the car, that's fine, but realize that you'll get more time from working on the driver.

I just did an autocross and rode in two other STis (who both ran novice last year). Their biggest problem was going too fast in the corners, leading to various degrees of scrubbing and pushing, which means they can't get back on the throttle coming out (they also didn't unwind and back off). I think corner exit is our car's huge advantage over the others, and if you're going too fast in the corner, you just push out on the exit which means you can't get on the throttle. This isn't the car, in my opinion -- heck, my loosy goosy Miata would do it if you went into a tight corner too fast. Number two for them would be looking ahead -- that cuts down on extrenuous steering inputs and exiting a corner pointing in the wrong direction.


Not sure I could have said it better...


As for the stock alignment... can we change caster on a stock STi suspension? I was under the impression that it was not adjustable.



-Matt (Still a scooby-noob)

Originally posted by jmott
camber loss due to body roll:

as the wheels move up in the wheel wells, they get MORE negative camber.

which is what happens to the outside tire

which is what you want, yes?


so why is there loss of negative camber due to body roll?

with the strut style suspension the amount of camber gain through compression is so small compared to roll over due to body motion. This is obvious from tire wear (i just corded two victoracers up front this weekend)... why? they corded on the front and the VERY outside edge was what went (about a half inch from the line that sperates the sidewall from the tread. The insides are near full tread. So the concept behind it is to help keep the tire flat in the corners with the limited negative camber gain (this ain't no double wish bone!!!). How do you do that? reduce body roll. How do you reduce body roll up front in stock? Massive stiffening of the front rollbar. Test different settings till you find the optimal balance between stiffness and contact patch.

If you get it right... the car should loosen up on turn in... exactly where it needs it. I'm still testing these things but I believe the theory sound. I believe that some of the FWD stock tuning techniques (such as a smaller front bar) should NOT be used with the STi. The vehicle should be treated as a strut equiped RWD car for setup purposes.

Adjustable front bar should be on the car next week... combined with an alignment this week (with weekend testing in between). We shall see... I'll have good benchmark drivers both weekends to help figure if an advantage was achieved. Then, of course, DC at the end of may.

-Matt

Originally posted by WRX_Mundi
Slow in, fast out. It is possible you're driving the car just right at one of your first events, but that doesn't seem to be usual in autocrossing. First, get a good alignment. Then work on driving. If you want to spend some money on the car, that's fine, but realize that you'll get more time from working on the driver.

I just did an autocross and rode in two other STis (who both ran novice last year). Their biggest problem was going too fast in the corners, leading to various degrees of scrubbing and pushing, which means they can't get back on the throttle coming out (they also didn't unwind and back off). I think corner exit is our car's huge advantage over the others, and if you're going too fast in the corner, you just push out on the exit which means you can't get on the throttle. This isn't the car, in my opinion -- heck, my loosy goosy Miata would do it if you went into a tight corner too fast. Number two for them would be looking ahead -- that cuts down on extrenuous steering inputs and exiting a corner pointing in the wrong direction.

I'm trying to be helpful. I found my stock STi with a good alignment to be pretty nice. It didn't rotate, but it did nice drifts under power. The only time I recall it plowing was when the driver (me) screwed up and didn't slow down enough for the corner. Amazing how much times drop when you can go just slow enough in the slow parts and fast in the fast parts.




Perfectly said.
I found the plowing to be true this past Saturday on a fairly slow AutoX course with sweping 180degree turns. Lots of fun. Times kept coming down as I was trying to get in the corners SLOWER and get on the gas little earlier and full power.

What really helped me was having an experienced Subaru RS owner show me this in my own car. He killed my time 2 months ago as he drove it way faster than me but really showed me the slow in fast out thing. (IMHO, is very hard to control as I want to go in hotter)

Suggestion: full rear DCCD lock helped for me. (weather was 70 degrees and dry)

Rally On,

Davis

gotcha

would be interesting to do some testing to see at what point more front roll stiffness starts to hurt grip more than help.

Im planning on getting that "geez" device so I can do stuff like that with my new toy.


Originally posted by Watkinsm3
with the strut style suspension the amount of camber gain through compression is so small compared to roll over due to body motion. This is obvious from tire wear (i just corded two victoracers up front this weekend)... why? they corded on the front and the VERY outside edge was what went (about a half inch from the line that sperates the sidewall from the tread. The insides are near full tread. So the concept behind it is to help keep the tire flat in the corners with the limited negative camber gain (this ain't no double wish bone!!!). How do you do that? reduce body roll. How do you reduce body roll up front in stock? Massive stiffening of the front rollbar. Test different settings till you find the optimal balance between stiffness and contact patch.

If you get it right... the car should loosen up on turn in... exactly where it needs it. I'm still testing these things but I believe the theory sound. I believe that some of the FWD stock tuning techniques (such as a smaller front bar) should NOT be used with the STi. The vehicle should be treated as a strut equiped RWD car for setup purposes.

Adjustable front bar should be on the car next week... combined with an alignment this week (with weekend testing in between). We shall see... I'll have good benchmark drivers both weekends to help figure if an advantage was achieved. Then, of course, DC at the end of may.

-Matt

Originally posted by jmott
would be interesting to do some testing to see at what point more front roll stiffness starts to hurt grip more than help.

It appears that it's not possible to get a big enough front bar in _stock_. I am still considering having a HUGE (like 30mm!) bar custom made just to find out for certain.

--Kevin H.

The Hotchkis bar is 1 inch ... 25.4 mm ... but hollow ... so equal to more like 23 mm. It helps ... but is no substitute for stiffer springs/coil overs ...

1a- Don't forget this is supposed to be fun
1b- Evolution Driving School - or something like it
2- Race tires
3- Alignment
4- Shocks
5- Bigger front bar

Originally posted by Watkinsm3
I don't agree with this...


-Matt

Yep, I am with Matt on this. We have done some testing with graphed results if you are interested:

http://www.selgp.com/sti_modifications.htm

Originally posted by makofoto
The Hotchkis bar is 1 inch ... 25.4 mm ... but hollow ... so equal to more like 23 mm. It helps ... but is no substitute for stiffer springs/coil overs ...

Ah... but without the springs/coil overs option in A-Stock we're left with one lonely solution... front bar please!


As for the bar I'm experimenting with? Its BIG... Its adjustable... :devil:

-Matt

quote:
Originally posted by afpdl

Bigger front sway bar will reduce ultimate front end grip


I don't agree with this...


-Matt

Bigger front bar reduces steady state grip but increases transitional grip. most autox's these days are all about transitions. what you make up there is more than you might loose on the few sweepers.
better damped shocks will help on the sti as it is underdamped to beging with

Originally posted by FSelekler
Yep, I am with Matt on this. We have done some testing with graphed results if you are interested:


You don't happen to have the average/mean G loads for those turns do you? Somewhat unimportant since the raw times tell a good deal but, average constant loads are tell a great story compared to peak loads.

Good and interesting info!

-Matt

Originally posted by MonoSki
Bigger front bar reduces steady state grip but increases transitional grip. most autox's these days are all about transitions. what you make up there is more than you might loose on the few sweepers.
better damped shocks will help on the sti as it is underdamped to beging with

An your data is where? I seriously hope this is not just a "bigger front bar induces understeer" generalization. Check out FSelekler's link when you get a chance... ;) shocking! :eek:

NOTHING... beats real world testing (with a good driver in a consistent eviroment... blah, blah, blah). BUT... if you still believe you're right you are MORE than welcome to run this other setup in Topeka... I won't stop you... in fact, I only encourage you to! :devil:

-Matt

Originally posted by Watkinsm3
You don't happen to have the average/mean G loads for those turns do you? Somewhat unimportant since the raw times tell a good deal but, average constant loads are tell a great story compared to peak loads.

Good and interesting info!

-Matt
LOL, amazing you are the first one to notice and ask for that :)

Yes, we have that data, but we did not publish it at our site as we have to protect some part of the data that we use internally. It is just too easy for other vendors to grab data and run with it ;)

As you stated, it does not make much difference from the end result perspective, but it is the kind of data we actually need to do development for various combination of products.

Originally posted by FSelekler

Yes, we have that data, but we did not publish it at our site as we have to protect some part of the data that we use internally. It is just too easy for other vendors to grab data and run with it ;)


Ah! Makes sense... I just put 2 & 2 together and connected that page with the rest of the site! You guys have some good info in there. I was looking over your info when I first got my STi about 4+ months ago.


-Matt

Thank you Matt, I appreciate :)

Originally posted by FSelekler
Thank you Matt, I appreciate :)

what data logging tool did you use? do you reccomend it?

I'd recommend the largest bar you can find for the front. Don't believe teh Biggly? Ask trhoppe how he feels about a big front bar on an otherwise stock STi... ;)

Originally posted by jmott
what data logging tool did you use? do you reccomend it?

We use MaxQData. It is a pretty nice system, we needed something that works with a Pocket PC rather than Palm. It is not the most useful, unles you do a lot of detail analysis and normalize data, comparing do different cars with different setups. however, it is very useful comparing various setup changes, drivers, or lines.

You can find more informaiton at www.maxqdata.com.

Originally posted by Davis K Powers
What really helped me was having an experienced Subaru RS owner show me this in my own car.



I'm an experienced Subaru RS owner ;)

-Matt

I had the same exact thing happen this weekend, I showed up and won my first autocross in the STi. I also had the pushing problem. I was trying to fool around with tire pressure to correct it, but I guess the problem is just me:lol:
This thread has been very helpful, and I thank you all for your input. Anyways Do you guys run stock tire pressures? Just wondering...

Originally posted by jmott
Im planning on getting that "geez" device so I can do stuff like that with my new toy.

You should add the "Old Man Gold" car to your profile.

Stock Tire Pressures ? You are putting a lot of extra load on your tires ... of course you need more air ...

There are so many AutoX resources for beginners ... look around.

The Grassroots Motorsports web site, tech section ... has some good articles: http://www.grmotorsports.com/techmain.php

TONs of info here, tire section, etc.

email me your email address so I can send you an attachment ... of our clubs Novice Handbook ..

Originally posted by RoninSTI
Anyways Do you guys run stock tire pressures? Just wondering...

Obviously this is gonna vary depending on the tire used but the easiest answer is no... ;)

On my kumho victoracers (255s) I've been running 40psi up front and about 34-36 in the rear (depending on amount of grip i want in the rear, Looser > 35 > more grip > some #psi > looser). Any more than 41 up front and the car starts to push incredibly and much less than 39 I get severe roll over. Not much of a window in my opinion. Mor experimenting to come now that the alignment has been done and the front bar will be going on this week.

-Matt (maybe you guys shouldn't listen to me as I got my azz handed to me this past sunday. It was ugly. Don't think I even made top 10 Pax :eek: )

A guy running an evoIII(rhd!!) suggested i run 36 in the front and 42 in the rear. I got my fastest time on this setup, but I find it odd that its the exact opposite of the pressures you're running. Would the pressures i ran partially contribute to the understeer?
Sorry for thread hijacking and I really appreciate the detailed informative responses.
Makofoto email is on its way
thanks again, I'd really like to be competive and i'll take all the help i can get

Originally posted by RoninSTI
A guy running an evoIII(rhd!!) suggested i run 36 in the front and 42 in the rear. I got my fastest time on this setup, but I find it odd that its the exact opposite of the pressures you're running. Would the pressures i ran partially contribute to the understeer?


Not sure... depends on the tires... suspension... ;) With the high pressures in the rear I imagine the car will probably rotate well but I find running high pressures in the back to gain oversteer makes the car more likely to snap oversteer where as lower pressires to get the oversteer result in a more progress rotation that's easyto control and catch.

Any tire pressure in the rear that is not optimum is going to result in rotation. say for your setup that the rear tires generate maximum grip at 37psi... raising or lowering the pressures from that number is going to reduce rear grip and cause the car to rotate. Which direction you go is a matter of preference for the most part

-Matt