jason t

Another couple ideas for you.

1)If your JDM spec STI has aluminium front lower control arms you can add another .35deg. of caster by flipping the black pin that bolts to the arm. This black pin is mounted to the ALK. You will notice the pin is more concave on one side.

Adding caster will create "camber gain" (more neg. camber) to the outside wheel when turning.


2) Adjust the rear sway to the stiffest setting, should/will promote more oversteer. Over here(Canada) the most popular Whiteline swaybar combo is 24mm frt/rr adj. I usually set the frt on the softest setting, rear on middle or stiff setting but it all depends on what tires are underneath the car. R-comps I will play around with rebound damping, swaybar and alignment settings when compared to a street style tire.

3)I would run -2.25 frt rear 1.75 rr camber, 0 toe all around and max caster. If you want more oversteer run less rear camber, this will promote rotation. Specs could cause premature inside tire wear, these are aggressive street alignment specs.



I believe your AST are single adj.(rebound) here are some tips for set-up:

Corner entry oversteer: Soften rear rebound
--initial LWTD shifted off rear wheels, weight transfers forward slower
Corner entry understeer: Stiffen rear rebound
--initial LWTD shifted onto rear wheels, weight transfers forward sooner
Corner exit oversteer: Stiffen front rebound
--initial LWTD shifted onto front wheels, weight transfers rearward sooner
Corner exit understeer: Soften front rebound
--initial LWTD shifted off of front wheels, weight transfers rearward slower


Jason

HRT

Hi Jason

Thanks for your input as well.

I will actually measure the ride height as I always thought it was quite high compared to other Subarus. Also it does not scrape over speedhumps and can go anywhere my wifes Honda Jazz can.

If the lower control arms are not aluminium can I still do this adjustment under point 1? I do not think they are aluminium as they look the same as the ones on my WRX - quite dark colour as opposed to aluminium ones which I have seen which are 'silver' in colour.

Arnie_1

All STi's use alu front control arms. Certain models used the high caster arms (Spec C and USDM 04-06) some use the low caster arms (07 STi, 01-03 bug eye). You can do the above "free caster mod" with any alu arm.

Yes, check your ride height. Its looks to be around 340mm or so. Could be wrong, hard to tell from the photo angle. Ride height and suspension geometry is often misunderstood or ignored entirely by most people. Most just get the car as low as possible and think that the lower center of gravity will "make the car handle like its on rails". But what you don't feel or see is the outside wheel folded in on itself giving no grip whatsoever. Without relocating the suspension pickup points you won't benefit much from having the car so low, in fact it just handles worse. Often times people who are that low are running super stiff springs and/or swaybar setups. So you have more roll control and maintain proper outside wheel geometry...simply because the suspension doesn't move! Throw any mid corner bumps into the mix and the car just skates and hops to the outside of a corner.

If you work on your own car, I would also consider learning how to align at home. Its quite easy to do and will save you money and time at the shop. You will lose a bit of static neg camber when you raise the ride height but you can either add some more or just see how the car handles just with the ride height change.

jason t

Arnie is right on the money, what he said in the second paragragh is something anyone modifying their vehicles rideheight should keep in mind.

Here is more info on roll center:

http://en.wikipedia.org/wiki/Roll_center

and

http://www.neohio-scca.org/comp_clin...namics2007.pdf

HRT

Very informative and something I never even considered as it feels fine on the road.

Just measured and the front and rear are 330mm, so possibly sitting very close to bump stops. Will raise to about 350 in a first step with some of the other changes mentioned and see how I go on another trackday.

Have had a look at my classic WRX racecar and it is 340mm fornt and 330mm rear so will be adjusting this as well.

dunx

iTrader: (3)

No, the classic is a different car. Get advice from those that know them best.

IMHO.

dunx

Arnie_1

Here are some ride height recommendations from jgevers. I agree with his recs.

Classic front 350mm rear 345mm
01-04 front 370mm rear 360mm
05 front 380mm rear 360mm

mantazini

iTrader: (25)

Ver good thread guys

Suberman

Excellent read! Although i got lost after the first 2 pages. Cheers for the links Jason.

Arnie_1

Keep in mind, there are many ways to skin a cat. Lots of parts, setups and driving techniques to reduce or eliminate understeer. What works for one might not work for another. So take everyone's advice as a starting point and not gospel.

There are certainly some basics that seem to work for all (larger rear sway bar and more front camber) but beyond that it gets pretty specific to car and driver.

HRT

Thanks to all who commented.

Although it may cost a little bit extra in terms of time, effort and money, I will take a measured approach to changes. First increase ride height and stiffen rear 22mm ARB plus flip the bolt on the front lower control arms and align. I will then attend a trackday again as i have a base of 64 secs. Only other variable should be driving style and damper settings, as the weather should be the same in the next month.

See how this goes and then top mounts, camber bolts and Whiteline Roll centre adjustment kit. If still improving, then decide whether this is enough and start looking at tyres or sit back and enjoy the quicker times and spend my money on the racecar.

Arnie_1

Sounds perfect. Do the "free" modifications first. You can have all the top kit on your car but if its not set up properly you'll still suffer.

I think this project will be an educational one for all those tuned in. Your car is currently set up in a manner that is representative of what the average enthusiast would do. I'm really excited to see what improvements you have just with your first step, "Proper geometry and light swaybar tweaks."

Not sure if you wrench on your car yourself, but raising ride height is free. Doing the free caster mod is free. Swaybar adjustment is free. Only thing you need to pay for is having your front camber and toe set.

The king

Good point. A socalled "bump steer kit" would help getting the arms back in its optimal position..

Arnie_1

Its actually a "Roll Center Kit". The bump steer part of the (Whiteline) kit, the altered tie rods, alter the car's bump steer. The modified ball joint at the knuckle alters the control arm position, lowering it (thereby raising the roll center).

In HRT's case, I'd rather get him back up to a reasonable ride height and see how he does from there. He can certainly benefit from a WL Roll Center Kit. I've found it great even on stock suspension. At some point he (and others) will have to find that happy medium between aesthetics (a low ride height) or performance (higher ride height). Note, we're not talking an all out Time Attack car here with lots of aero and massive spring rates and altered pick-up geometry. My personal taste is always to lean towards performance and the aesthetic will be whatever it is, usually with uneven fender gaps and too much gap up front. But some prefer a better looking car. As long as you are aware and willing to give up a little bit in "ultimate handling" then have at it!

The king

Well, a lower car with control arms in a senceful position, would be better in good roads...

Arnie_1

It depends on whether or not you are planning on turning.

As long as the control arm orientation still promotes neg camber of the outside wheel in a turn, i.e. sensible position, then that's great! Problem is, this position is at a lot higher ride height than people are willing to accept from an aesthetic point of view. That's the problem with the whole camber curve/roll center thing. A lower center of gravity is important, no argument there. Its just when the camber curve and roll center suffer from over-lowering that we get into trouble. That balance can be pretty tricky to find, that's for sure.

The ride height and the smoothness of the road(or lack of) comes into play when one is so low that one is running out of suspension travel, riding the bump stops and encountering some coilbind or bumptstop engagement. You get that corner entry understeer when you're so low that the intial weight transfer sucks up all the available travel on your outside front corner. Your spring rate goes up due to bind or bump stop engagment and you push wide. Then you can get mid corner understeer if you hit a bump mid corner and it throws you out further off line.

Once again, its a balance of geometry and usable travel.

HRT

Update

I have made some changes with good results.

However in bteween there have been a few trackdays which I did not attend. The top spots are
Lambo Gallardo - 56.5
Mazda RX-7 - 56.7
M3 CSL 56.8
Westfiels Megabusa - 57

The best Evo or Scooby is only at 59 or so. They all complain of understeer.

The best time for one of the hillclimb cars is now 52.1, a very lightweight and 550odd bhp Evo 3.

I made the following chnages in preparation for the track day.

Increased the front ride height to 345mm from 330mm and the rear to 335mm. Put the rear arb to stiffest setting.

Decreased the front rebound on the AST's to 3 clicks from softest while the rear was at six clicks.

I attended the trackday yesterday. Weather was a little warmer than January with 21 degrees, but obviously no effect on performance.

My previous best was 1:04.28 with a lot of understeer.

After a one lap warm up I ended up with the following:

1:03.01
1:02.81
1:02.60 BL
1:02.74
1:04.23
1:04.33

The car was so much better and stable, far less undesrteer on corner entrey and much better under corner exit. Obviously could still make it understeer if I wanted especially on corner exit, but it was now manageable.

However you will notice that the last two laps were slower. Whilst on the second last lap, there was a drop in perfromance and the induction noise had changed. I knew immediately that I was losing boost and the boost gauge showed it struggling up to 0.6bar instead of 1.6. Felt like a 250bhp car and was slow.

I pitted and checked for obvious loose fittings but could not find anything wrong. At the same time checked hot tyre pressure and they were at 45psi I had started at 34psi I immediately lowered the hot pressures to 35psi as common thought is that these are too high.

Went out again knowing that the car woudl be far slower, but it was a chance to check the differences with tyre pressures. With a far slower and less powerful car, it was awful and had gone back to its old understeery habits.

I ran

1:04.50
1:05.26
1:06
1:07.02

The power loss became worse and as can be seen the times went downhill.

I came in and increased hot tyre pressure to 40 rear and 38 front as it was evident that the T-1R have a very soft tyre wall and it was folding over. I know that this may go against the norm, but it was definitely better on higher pressures.

I then went out again with the driver of the M3 CSL as a passenger to give me some tips. He could see where I was getting my lines wrong and offered to help. I watched his laps and he has excellent car control. He did state though that to stop it understeering he was running -3 camber up front. He has 360mm AP kit up front and the standard CSL Michelin tyres, which do not look standard.
Car felt far better on the higher tyre pressures.

Times went

1:09.57
1:06.41
1:05.04
1:05.35
1:04.98
1:04.11
1:03.82
1:03.98

What a difference despite being some 200bhp less. This guy really knew his stuff. Even though he had never been in my car, he knew when to get on the power, when to start braking and really use my AP's to the fullest without triggering the ABS, which is what I was doing. Had me all over the kerbs and using the track to the fullest, but wherever possible saving time by staying on the power even for a metre longer and then really hauling it up under brakes. The AP's handled it with no problem. He did comment that power wise it felt like a standard WRX, and that with full power resumed and no passenger the car would easily run a 59 as is. With a set of semi slicks should be running 57s

I have just ordered the Whiteline adjustable camber/caster kit and the Whiteline roll centre kit for fitting before the 13 March. Hopefully this does not throw out the good work done.

So overall a good weekend despite the power loss, which I saw what the problem was as soon as i opened the bonnet when I got home.

The intercooler pipe straight from the turbo had moved off and there was a centimetre gap between it and the turbo, hence 0.6 bar boost.

I know that the T-1R's perform best at normal street pressures i.e 34-35psi cold, despite them getting to 45psi they did not go off or overheat. I think I have a good setup on the rebound settings.

Thanks to all for their input. I will keep you posted of the results after the 13th.

The king

Edit: Enough said.

The king

If you can adjust you shocks, then you can tune some of the understeer from there.

Typically, less bump and more rebound help corner entry understeer.

Edit:;

Do you have the AST compretition coilovers?

HRT

Only have the Sportlines. Only adjustable for rebound. i softened the front and hardened the rear and it was much better.

Arnie_1

That's great news! its also good that you learned the most important aspect about track days and setting good times, "Fix the nut behind the wheel first!". Learning to properly drive is the single most important modification you can do and should be where the bulk of you money is spent. It is, however, less than sexy! We all know we'd rather buy toys for the car. But its great to see the improvement in both setup and driver's skill.

What are you current alignment specs?

The Whiteline Max-C plates are a nice bit of kit. I run them on my car set at full max caster position. Then I use the camber bolt to get the camber to what I want (about -2.5 for track work on sticky summer tires). Your AST should have the lower clevis holes set a bit more inboard so you can get pretty decent camber just from the bolt (around -2 to -2.5). You'll need to check your tire temps (probe pyrometer on the inner, middle and outer edge) to really see if you are maximizing your tires. I'm also a big fan of the Roll center kit. Less roll, geometry improvements. All good stuff.

Toyo's tend to have very soft sidewalls/carcass compared to other brands, even their semi slicks. So you will get a bit of sidewall fold over if you don't run a bit more pressure, as you found out. But its definitely a balancing act between keeping the tire from folding over and overheating your tires or not using enough of your tires due to lack of camber. But for those tires and your current setup, I would think you would need to run a minimum of -2 deg of camber up front. But running -3 is certainly within the ball park depending on how much roll you get. Rear look at -1.5 to -1.25, depending on how loose you like the rear.

dunx

iTrader: (3)

standard CSL Michelin tyres - one of the best/most expensive available

Glad you can see an improvement !

dunx

warren m

jesus lads,i thought iknew a bit about cars,i obviously know very little in comparison with some of you lot,good site this far more knowledge on suspension set ups etc..far better than some other make of car forums i have been on,only just got my impreza but tried to take on board the different opinions on here,thanks.

Arnie_1

Agreed. Michelin Pilot Sport Cups.

HRT

Improvements are continuing. I ordered various Whiteline parts but they were delayed in arriving and I did not get the chance to fit before the weekend.

So I was running exactly what I was the week before but with the boost pipe fixed. Weather was a bit warmer at 20 degrees, which helped the tyres get up to temp. I concentrated on finding the optimal pressures which seemed to have the biggest effect on the cars behaviour.

Tasty selection of cars arrived, various RX7, Lambo Gallardo, Lotus Exige S, M3 CSL, couple of STi's, Seat Cupra, Audi S3 and one EVO 9. They were all running some form of semi slick, even the Gallardo and Cupra were running Toyo R888.

First five laps ranged from a best of 1:02.36 to a 1:03.45. So i had just beaten my best time. However the car was not right and was moving about a fair bit. I had tried cold pressure of 30psi and at the end they only got up to 35psi, although the front right was 2 psi higher. Undesrteer was still prevalent if I was too quick into the corner with some oversteer when the full 1.6bar hits.

Increased pressures by about 3psi front and 4 at the rear, and took into account that the front right was getting a harder workout so gave it 1psi less. Immediately the car felt better and all my laps were under my previous BL of 1:02.36, with 1:01.73 to 1:02.22 being the worst. There was no drop off in performance compared to the cars with semi slicks. They all seemed to get their best timeon lap two and then would drop off from there.

I spoke to the Lambo driver and he commented on how fast the Sti was down the straights, he was hitting about 80mph while I was just over 75 mph. however his was so much better through the corners hence 56 secs.

Again I felt that a slight increase in pressures was warranted. On my last laps I was out with the Lotus Exige S. Having another fast car on track seems to make you go a bit mental and although I again got another best lap of 1:01.38, I had several low 1:02 due to silly mistakes. I was faster than the Lotus by about 0.5 sec per lap, but I am not sure how well it was being driven. I would have expected it to be right at home on such a track and be up with the Lambo and CSL, so maybe the driver was still learning. I felt I had gone one step too far with the pressures and the car was better in the second stint with about 34-35 psi cold. They seemed to increase pressure by about 5-7psi, when hot.

So I have cut over 3 seconds overall and 1 sec or so per visit.

So now to fit the bits and pieces and try again. Although I am thinking that I may start up the hillclimb car and give it a go, although I fear it will be very laggy on the tighter stuff.

Arnie_1

Great update! This thread is definitely a worthwhile read and very
informative. This current post is a great reminder about how important tire pressures are to fine tuning that last little bit of your setup and balance. I think once you get all your parts on, you can spend the rest of the season on fine tuning the car and driver setup.

Once you have all your parts on and have settle on an alignment range, have your car corner weighted. You'll probably find that your tire pressures and temps will be spread a bit more evenly between your left and right sides. You also probably won't have to go up as high on your driver's side tire pressure.

Great job!

Arnie_1

BTW, how much negative camber are you running front/rear?

stef_2010

iTrader: (3)

Hope nobody minds me digging this up rather than posting a new thread and no-one answering me

Seems to be a good few people who know what their talking about in here so this is probably the best place to ask

I have a classic type r and I'm looking for suggestions on setting up my new coilovers, with handling only in mind, not fussed how it looks. The car does get used on the road aswell though, mainly b roads

I need to know the full settings so I can tell the garage what I'd like, I'm sure you guys know better than them

I need:

Ride Height

Camber (front and rear)

Castor

Toe

and whatever else I can adjust that I've missed

I've just started to mod the suspension/handling on my car so dont have any other fancy bits yet, is there anything else that I should get at the moment that wont break the bank ? I'm finding, like everyone else that my car understeers like a pig, thats probably partly down to me though

Also is there any free mods i can do ?

Any help appreciated

Grant74

iTrader: (10)

If its helpful, I have just had mine done- negative 2degrees camber all round, neutral toe in, and as much castor as they can get.

1.5 degrees negative camber is better for road use.

Ride height- not too low!

dunx

iTrader: (3)

Doesn't a Type-R come with DCCD ?

Just wind it open...

dunx