Grant74

iTrader: (10)

In our local event I have seen pics of my car cornering and lifting the inside rear wheel which isn't ideal.

Car is caged and poly bushes, with bc's set 3 clicks softer at the rear but overall fairly stiff, and a 22 mm rear arb.

I use 2.5 degrees of camber on the front, and 2 on the rear.

Would appreciate any input from people who have has this- it is event driving and I am using super soft kumhos so catr is being driven hard, but because I have standard diffs the rear spins up.

Have posted here as other forum got no replies- here is a pic to illustrate:

mark@wrx

The obvious answer is to stiffen the front ARB but that will increase understeer. Had the same happen to me on track days and also in a tarmac spec Escort Cossy on rallies.

Dave Hedgehog

iTrader: (1)

GEt a quaife diff. Problem solved.

A stiff car on stiff suspension will do that. It should only do it under braking, and sit back down under neutral stance/ acceleration so I can't imagine you'd be losing too much to tyre slip.

Grant74

iTrader: (10)

Rear diff? I think I may go 6 speed so not looking at a serious hardware change at this point, more tweaks .

I didn't know a stiffer front arb would bring the rear wheel down so not so obvious to me lol but appreciated

bonesetter

iTrader: (9)

You run BC's. How much lowering have you dialed into the car? Does the car understeer at all? You may be going quite far into the camber curve up front and pitching the up the car up att he rear.

Have you a side pic of your car at rest?

Grant74

iTrader: (10)

It is pretty low and I have roll centre adjusters and an alk kit?

What are you suggesting ? It does ride a bit higher with the kumhos as they are a 225 45 profile, but that's what it has on there- I will have a look for a side pic

Grant74

iTrader: (10)

Sorry meant to say it will under steer but been practicing and it quite consistently is balanced leading to oversteer- too fast in still gives understeer

bonesetter

iTrader: (9)

I would say you have a couple of things going on. I suspect the car may be a little too low. The roll centre correction will help this but still maybe going into positive camber on the outside front wheel, rolling onto the tyre's shoulder too.

Other thing is the rarb is, I would say not enough and you're getting too much rear roll (as well as a shed load of front roll from the over-lowering). I would be looking to go for a rear Whiteline 24mm adj set on middle setting, with a front 22mm set on firm. This will keep the car much flatter through the twisties

Your pic shows the inside rear tipping (rolling) up, causing the outside front to 'dig-in' exacerbating the roll problem, and considerably reducing overall grip and traction levels

Grant74

iTrader: (10)

That's much appreciated- I will get on to that and upgrade both !

My boost controller just have up the ghost so will see if I can get an mbc in there to let me run for the last event

Cheers grant

bonesetter

iTrader: (9)

Yeah, you would get a big improvement from just the rear, but I've always settled on 24/22 on all my Imprezas, new age & classic.

If you have a side/static pic, do post it up

Grant74

iTrader: (10)

Are you saying that in part its the ARB's not being stiff enough thats causing the rear tipping/ front dig in issue?

These pics may help which I have just taken- dont have any static pics it seems!

Car looks high in them, but its not- tyres on it are 215/40/17 but the hill tyres are 225/45/17, so quite a lot taller, and thats as low as as I can get it for the larger tyres with the arches rolled, so I keep it the same to make life simple for setup (which happens qwith the larger tyres on).

bonesetter

iTrader: (9)

That looks pretty good, not too low at all, so as you have the RC correction too height shouldn't be a factor.

What spring rates are on the BC's?

Arnie_1

Ah, the infamous tripodding!

Indeed this is a common occurrence on tight corner where you've got a lot of weight transfer going on (like a tight turn under braking or in this case, an uneven surface at a corner). If you've got DCCD, the rear diff makes a horrendous clunk too when the car does this.

There are a few causes to this phenomenon, some even a combo of the causes. Here are few that I recall:

- Driver induced. Braking very late into the corner and putting a lot of weight transfer into the mix. Or poor driving line.

- Using coilovers with very little suspension droop.

- Rear ARB too stiff causing a lack of independence in the rear suspension.

- Front ARB too soft or spring rate too soft causing front roll induced "rear lifting".

BCs are pretty notorious in lacking droop travel. On most road courses, where corners this tight are rare, its not a problem really. On tight courses, like slaloms/autox or some hill climbs, lack of droop can lead to this ^^^. However, there have been cases where even with stock struts/springs, I've seen tripodding.

People have had success running a larger front swaybar to reduce front end roll and the tripod. Installing a larger front ARB, IMHO, doesn't actually increase understeer so much as make the car less willing to rotate. Basically, a larger front ARB reduces front end roll and helps preserve roll induced camber loss. Basically, the more your front end rolls, the less camber your outside wheel has and the less grip you have....leading to understeer! A larger front bar allows you to maintain more grip for a longer period before going into understeer. If you keep the rear bar the same, the car will feel like its understeering more because the car doesn't want to rotate as well. But you will have higher cornering speeds because your front end is gripping more. But its all a balance game, don't be tempted to go big, big, big! but even going with a 22 or a 24mm (max) front bar will help your situation a bit. but just a bit because you really don't have any droop in the rear.

For now, I'd look into a larger front ARB. See how you like that. Perhaps contact Bren at Apex and see if they can set you up with a rear coilover setup with more droop. it will be their "long travel" setup with helper springs. it will definitely help your situation though perhaps create issues elsewhere. Only way to know is to try.

As for driving, you can try to get your braking done a bit sooner so that you aren't fully loading the front end on the turn. Basically, being on a more neutral throttle and chassis attitude when entering the turn. However, if you're trail braking to get the car to turn in, then there are other issues that need to be fixed, set up wise.

Grant74

iTrader: (10)

There is a little trail braking but in essence in that pic the corner is the first one after the start, so coming in hot in second, trying more to lay off the throttle on turn in rather than actually braking- maybe a quick dab per corner but no more.

By the point in the pic throttle is back flat as I'm trying to get back on boost having backed off a little on entry plus speed lost on turn in.

But have other tripod pics on virtually every other corner lol

I'm going to try changing both arbs as suggested and agree re lack of droop.

In fact if you look inside rear is probably nearly fully extended ! Didn't know there was a long travel option- have found apex very helpful so will give them a call.

Next Hill is end of the month so not going to try before then as that's too much to take in- I might try stiffening the rear arb a notch though as can have a little play before as that's easy to do- seem to think fitting front arb is a mare for some reason.

I have also been sand racing in a little front wheel drive 1.6 impreza which has been fun- that doesn't tripod it drifts then tries to roll when it finds a ridge lol

Appreciated gents

ASJ

Not sure where the road goes on from the picture, but you appear to have a lot of steering lock on if you are foot to the floor on the throttle. (Could just be the picture though.....) Coming out of a tighter corner like this I would like to see the lock wound off past the apex before getting to WOT.

Wondering if a wider line with less steering input could be smoother, inducing less roll and hence less problems at the rear?

Take the above with a pinch of salt as it's nigh on impossible to judge the situation from a single still of course

Agree with the above comments about front ARB

Rgds, Ade

bonesetter

iTrader: (9)

Fitting a front arb is really quite easy. 40mins tops should see it done if you're not familiar with the job, shorter time if you are

Tip: When removing the old bar note which way it came off and which way the pick-up points are pointing. Leave the old bar in front of the car the way it was removed if you need to check again

Grant74

iTrader: (10)

Corner goes on straight into a 120 right so you need to be positioned quite deep into the second corner to try and get it as straight as possible.

I have done it several different ways and this seems the quickest- its on wot as it falls off boost as soon as you look at it which is annoying as its a baby sc36 and have now even tried a top mount with no dv, but boost controller just gave up so going to get the Simtek back on the go and remapped.

The views are appreciated- I'm clear that my largest time advances are as a result of learning to drive the car and getting advice and support from a number of people who are just better drivers. The car tweaks all help lol

Arch

iTrader: (59)

You did get a reply you just chose not to look at it.

https://www.scoobynet.com/driving-dynamics-354/

The problem you have is not enough droop on the BC's to accomodate hard cornering. Had the same issue myself. Tried everything including roll bar changes geo changes etc etc. In the end had to bite the bullit and change the coilovers.
I assume you are using either the BR or RM series.
I also had rebound issues if the rears were set within 4 clicks of full hard. i.e very little rebound which made the drooop issue even worse.

You wont solve this issue with roll bar changes or spring rates believe me I tried and in the end I changed the coilovers. I am certainly not belittling the BC BR/RM coilovers as they are a decent option for road and occaisional track day use but are not up to proper competition use and were not intended for that sort of use. As Arnie has said they do not have sufficient droop to handle the roll even a properly set up and corner weighted car has. I can testify to that. I did manage to reduce it substantially but it doesnt matter if the wheel is 5mm or 20cm of the ground the effect is the same. Even with a proper plated diff it still creates issues.

If you are using the car competatively I would recommend changing the coilovers to a set of KW Var 3 or if you can afford it KW clubsport.

ASJ

...into 120 right.... Makes your postion in the pic make more sense

Competing in sprints/hills you are so pressured into getting it right first time, using different lines/techniques can be tough can't it. Also not helped by the hour or two between runs. Nothing like circuit racing where you can spend days running round the track trying every possible variation in testing/practice/trackdays.

Rgds, Ade

Grant74

iTrader: (10)

Arch- sorry missed that- yes the cheaper range of bc's and think ultimately you may be right- I'm going to try the arb but fear that shocks may be the ultimate answer, but a different level of expense lol

Grant74

iTrader: (10)

Ade- I have some old videos on you tube If you search for impreza Bouley bay- I have come on since then but gives you an idea

Arch

iTrader: (59)

Wasting your time - trust me been through it all and been advised by some very knowledgeable guys who set the car up!

Grant74

iTrader: (10)

What did you end up on Arch? KW's are nice

Arch

iTrader: (59)

I was going for the KW Clubsport but got offered a nearly new set of EXE-TC fast road coilovers at a reasonable price. Had then rebuilt and specced by EXE-TC still to use them in anger tho. If these had not come up it would have been the KW's.

ASJ

See what you mean about that combination near the start as per the photo on the vids....awkward!

Since it's on public roads though, guess you can practice to your hearts content . Sprints/hills on the mainland tend to be on private land and hence the only access is generally on competition days. Exceptions tend to be race circuits where a single standing lap is used...

Rgds, Ade

Grant74

iTrader: (10)

I'm on the speed committee and you would be banned from entry if you practiced lol I always try and get a few runs up in range rover so j can dispel the demons in my head, but no comparison really.

But yeah like most hill climbs lined by in movable trees which is sobering- will try and record vids from next hill which will be a bit quicker than those, but conscious some of my competitors have been analysing them lol

Grant74

iTrader: (10)

Meant to say- kw club sports different from variant 3's?

Arch

iTrader: (59)

Yes very different.