Help - my car is trying to kill me.....fixed

[philwaters]

Spec:

Live axle - Ford. Tran-X LSD.

Spax adjustable platform dampers, set to full soft, with 300lb fronts and 110lb rears.

Double wishbone conversion on the front with Freestyle adjustable ARB.

13" Minators fitted with 032R's - minimum of 6years old!

8% (standard really) quick rack.

Standard track.

 

So, the story so far - as well as I can remember it:

 

At the end of 2002 I fitted a Ford axle to allay my fears that the ital item wouldn't last long with the Zetec power. This is fitted with a Tran-X LSD. All the axle work was done by HTR near Brands and I simply bolted it all into the car. The front of the car was left as it was (standard live axle top link plus the additional front link - standard ARB).

I didn't use the car much that year as we bought our house and the long DIY list started. However, I remember thinking that it handled ok and with the 032's that came with the wheels I got (to suit the Ford PCD) it had tons of grip and was good fun.

 

During 2003 I collected some parts so that I could carry out the top link to double wishbone conversion and a) adjust camber and b) fit an adjustable ARB from Freestyle.

It was now that I think (if my memory serves me correctly!) my problems began. However, as I used the car so little I wasn't sure if it wasn't just me. The problem was that the back of the car felt very nervous and lively, almost like it was on tip-toes as you went into a bend, it felt like the back end wanted to carry on going straight all the time. The front was lovely and pointy with zero understeer that I can remember. The ride heights, camber, tracking have all been checked and adjusted and I initially ran 2° of camber with zero toe-in. This was reduced to 1° of camber towards the end of the year which made little difference. Camber was checked using a length of angle with a screw at each end which touches the rim of the wheel and you adjust one screw until a spirit level says the angle is vertical - you then measure the length of the screws from the angle and then calculated using trig.

 

Over the following winter (2004) I embarked on a fuel injection project and this had really been swallowing my time on the car until late last year, when things started to come together finally. However, over the previous winter I did some research and found that I had quite a high breakaway torque on my LSD and that it should really have been less than half what I had (50ft/lb measured). I took the unit out and had it modified locally and it retested at about 22ft/lb. I hoped this would solve the rear end wanting to carry on straight ahead. I think it did, but I was left with a car that still felt very skittish and unpredictable over anything but the smoothest of roads or going into any bend. I honestly think my barge like Saab diesel feels more planted in high speed corners.

 

This year, the fuel injection is finally running pretty well and I have re-discovered my enthusiasm for the 7 and I am starting to use it more again. I really need to get to the bottom of the problem as it is drive me mad.

So on Monday evening I set the camber to 0° in an attempt to mimic the original LA set-up, and re-set the tracking (using a Track-rite push/drive over gauge in my level garage) to parallel. I also checked the back of the car and found that I have about 1° of camber on the axle (non-adjustable) and 0° of toe-in/out. I set the adjustable ARB to full soft (had been about half way between hard and soft). About a week ago I had wound on a quarter of a turn of toe-in on both tracking arms in an attempt to settle things down - but it hadn't made a noticeable difference. I also did a spanner check on everything, bounced the car and could find nothing loose or knocking.

Last night I went for a test drive and I'm convinced the thing is trying to kill me at every bend or on any bumpy road. I went out to Henley from Reading along the Wargrave road which is nice and smooth and whilst it was better it still felt like the back end wasn't to get to know the hedges at nearly every bend. I had to drive it like a point & squirt car, slow in the bends and try to fire it out. I think that setting the tracking to parallel has given me loads of oversteer, where I know it should really make the car handle sweetly. So it has to be another factor somewhere.

 

So I have the following things left to try out:

- Some borrowed wheels with CR500's on them (thanks Jason) because a) my 032's are now probably 6yrs old now (yes I've done that few miles!!) and b) the side walls are very stiff and may be upsetting things. Hope to try these in the next day or so - just so I can give them back.

- Check and change my ride heights. I think I already have the car set with a lower than normal rake front to rear to try to combat this but need to measure. I am correct - I've always thought that if you lower the rear you reduce oversteer/introduce understeer. The front lower wishbones are parallel with the ground, as are the steering arms.

- Dampers? I have some adjustable platform Spax which I fitted in either '99 or '00 with some 300lb front springs and 110lb rears. They have probably done about 15k miles and are not leaking.

- 4 wheel laser alignment to confirm all my measurements.

- Cry.

 

Does anyone have any suggestions as to what I could check next. So far everything should have been pointing to a neutral understeering car, but I am seeing the opposite. Is my thinking correct about the ride height effecting the handling - higher rear = more oversteer?

 

Phil Waters

 

Edited by - philwaters on 22 Apr 2007 22:48:44

[MartinWoodham]

Hi Phil, hopefully some who knows what they're on about will be along in a mo, to correct my half-baked opinions. Meanwhile:

 

Your spring rates sound excessive to me - 300lb fronts sounds high and 110lb rears sounds low. Although if this is original spec for the car you should be getting original handling characteristics! Maybe the rears have softened with age and you're actually getting a very stiff rear as the suspension hits the bump stops?

 

When you say you softened the ARB, the text isn't clear whether this is front or rear. If it's front (and presumably a freestyle bar) then this should have made things better. If its rear, are you certain you adjusted the right way (sorry!) - stiffening in error would make oversteer worse, on my car this is very pronounced.

 

Higher rear transfers more weight (statically) to the front so would promote oversteer. This is quite a small effect however, when you take into account weight transfer under braking.

 

now where's that expert advice.....come on, don't be shy...!

 

Martin

Aero'd supersported ex-Roadsports B...anyone got a cheap LSD?

[philwaters]

Thanks Martin - all advice welcome!!

 

Being a live axle they are happier with stiff fronts and softer rears - if you go to hard at the rear it doesn't ride the bumps very well.

Also - it is a front ARB, don't have a rear, and it is a freestyle one. As you say, softening this should have helped.

 

Phil Waters

[I.Mupferit]

Phil, is it worth having a chat with Gary May and discussing set up/spring rates with him? He does have a lot of experience setting 7's up properly so might be able to point you in the right direction. You could even book a setting up session on a Saturday morning down at his workshop near Brands Hatch.

 

Brent

 

2.3 DURATEC SV Reassuringly Expensive

R 417.39 😬

[I.Mupferit]

Just a thought. I'm sure you have already checked this but are your tyre pressures ok? I used to run my old car with similar spec to yours at 16 psi all round.

 

Brent

 

2.3 DURATEC SV Reassuringly Expensive

R 417.39 😬

[philwaters]

Thanks Brent,

 

I am running 16psi but I do wonder if it is the super stiff sidewalls, coupled with the tires having gone off/hard, making it feel like higher pressures and therefore the fair ground ride handling.

 

I can see a session at Freestyle coming up - but I want to check all I can before I have to take it somewhere.

 

Phil Waters

[F355GTS]

Phil

 

you are welcome to borrow a set of rims/ 48's/ 21's to see if it removes the problem (assuming you are on Ford 108 pcd)

 

Mark

[philwaters]

Thanks Mark, but I have stolen a set from Jason's car with some CR500's on to try out - I'm just working my way through the list of things to check.

Don't suppose you have a tracking gauge do you? I have a roll over type but I'm not sure how much I trust it, although I have measured across using string and it seemed about right.

 

Phil Waters

[F355GTS]

I have a roll over and had it checked after doing it and it is spot on! welcome to try it, also have a camber gauge, nothing to do tonight so drive round and we can check it all

 

Mark

[philwaters]

Cheers - I'll give you a call once I'm home and have squared it with SWMBO

 

Phil Waters

[philwaters]

Ok - permission granted (I'm out of the DIY for an evening - whoopee!) so when suits you Mark? I can get home for about 6.15, change get the car out, so say 6.45 at your place - or do you want to leave it until a bit later?

 

Phil Waters

[elie boone]

A live axle top link is not adjustable on camber, are u sure u have the correct one.

and the rear axle should have 0° in all planes, it's a long shot but does the axle have the reinforcement plate at the back ? if so it might be possible that the axle has been bent due to the welding.

I run 300lbs front and 140 rear spring on fairly soft damper settings and i like it the way it is.

[philwaters]

Hi Elie,

Yep, I fitted the top link conversion info.

Interesting point about the caber at the rear, hope to check that tonight. It does have some strengthening box section welded to the rear but I thought that the shrinkage effect would have effected the axle toe in/out, not the camber.

I need to go and see Raceline soon and they ran a LA Zetec car in the sprint series a few years ago so I ought to pick Pete's brains.

 

Phil Waters

[Unclefester]

I wondered about the 1° camber on a live axle.....maybe a mismeasurement?

 

Lucy in the Sky with Diamonds..ooooh hooo hooo!!...

😬 😬Abbey Road Time-Machine *eek*

 

[I.Mupferit]

I remember Pete McEwen at Raceline telling me a few years back that he used to purposely induce toe in on a live axle by very slightly bending the axle tube before welding on the bracing at the back. Apparently it improved the handling enormously.

 

So it obviously is possible to have negative or positive camber, toe in or toe out on a live axle. Whether by design or accident is another matter however.

 

Brent

 

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R 417.39 😬

[philwaters]

Hi all,

 

Thanks to Mark we have confirmed a few things - mainly that my tracking gauge is accurate and that for the most part my DIY camber gauge is quite close. However, it does seem that my reading of the rears is wrong as they both show up as 0° camber with his posh gauge.

I have now set the tracking to 0.5° toe in on both fronts - was hoping to drive in today to test but I was not in the right frame of mind for the 7. So it will have to wait until the weekend now.

We also confirmed that with me in the car I have around 13-15mm rake. However, it did occur to me that the settings I have been believing were right for the car were pre-LSD and that maybe I ought to forget about getting them right and just go with what feels right. It was interesting to hear that Mark runs 0mm rake to balance his track car. Problem is with the Ford axle being a bit bigger I am already quite low on the platform adjustment - not sure I can drop it enough to achieve that.

 

Plenty of things to try this weekend - so watch out if you are around Reading this weekend, you may see a wayward 7 with a scared looking driver behind its wheel

 

Phil Waters

[Martyn Heesom]

Phil,

 

have you checked for bump steer?

 

Martyn

[I.Mupferit]

*idea*Phil, is it worth asking an experienced 7 pedaller such as Mark or Angus, for example, to drive the car for a second opinion on the handling at the limit? I know the handling will be slightly different anyway to a De Dion car but they might be able to throw some light on it.

 

Brent

 

2.3 DURATEC SV Reassuringly Expensive

R 417.39 😬

[elie boone]

FWIW the live axle front settings

Toe in: 0°20" +/-0°10"

Camber : 0°45" +/- 0°15" ( neg )

Castor 5°00" to 7°30" ( 6°30" optimum )

[Alias]

6 year old tyres don't sound like a good idea to me. The rubber does tend to harden over time, thus losing grip and the hardening of the sidewall (as you mention). Would also check the rear dampers work properly (easy test to do!).

 

I can't work out whether you have a rear ARB. If you do, would strongly recommend you try disconnecting this as well.

 

-------------------------------------------------------------------

1800 Supersport with 6 gears and clamshell wings.

[philwaters]

Thanks everyone - I think the problem is solved (although more testing is required )

 

I finally cracked the handling problem today. I dialed in some toe in (0.5°, at least I thought) yesterday but all it seemed to do was make the front a bit more stable whilst the rear remained lively. Whilst it was predictable, it didn't inspire confidence as the rear just felt like it wanted to over steer all the time.

So, next on the plan was to check the ride heights. I did this when I was at Mark's checking out the tracking and camber. It was spot on with 15mm rake with me in the car. Whilst I was there Mark commented that he ran his track car with zero rake to make it more stable and nicer to drive. With this in mind I decided to try dropping the rear of my car to see what difference it would make. I managed to achieve 10mm before the passenger platform hit the end of it's thread, so I replicated this on the other side - leaving me with 5mm rake.

A quick test drive and the car was a revelation - it was almost back to how it felt before I fitted the LSD - the back seemed much happier to follow the front and it was far more stable under braking, something that had been worrying me. I guess that under the brakes the rear lifts (or rather the front dives) and this increases the rake giving even more of a problem than normal.

My steering wheel was offset to I spent the rest of the morning/afternoon messing about with the tracking and actually found I didn't have what I thought due to my carpet tiles moving under the gauge (I think) - so up they came and I re-did it all on the concrete floor - now spot on 0.45° each side (the 0.05° was due to the locknut pulling the tread in the rod end as they have both been repeatedly showing the desired 0.5° - but I can't be bothered to change them both for such a small amount. It feels like I've pushed my car further than I've driven it this weekend, and each time it was only 4ft!!)

 

So - everything is much better. There is still the slightest hint of the problem in high speed bends, but I think that was always there really. I am going to look for some shorter springs to give me some adjustment back and may well drop it another 5mm and try that.

All my testing was on my 032's as I didn't want some nice grippy newer tires masking a problem - they were a last resort and I'm glad I didn't need them after all.

 

Doing some more thinking on the problem and I think I have a theory as to why my old settings were so terrible. Firstly there is the LSD factor and the fact that it would make the rear a bit more 'over steery' but I am not sure that would manifest itself in the approach to a bend in the way I was seeing. I think the problem lies in the fact that the new axle is a larger diameter tube (thus stronger and why I fitted it). The distance from the center to the ground is determined by the diameter of wheel + tire so has remained the same. The larger diameter has meant that the damper & radius arm fixing brackets are therefore higher in relation to the center of the axle and you have to lower the spring platforms to achieve the same rear ride height as before.

I am wondering if the higher brackets mean that the radius arms were set to be at an angle when achieving the ride height and this has some 'strange' effect on the geometry - possibly shortening the wheelbase as it moves through their arc.

Interesting to note that most of the racers who run the Ford axle tend to fit double radius arms to ensure the axles moves in the desired direction (basically - up).

 

I'm a happy bunny again - and it just goes to show that sometimes you need to forget all about the 'well those settings were perfect before' and start from scratch!!

 

Phil Waters

[rj]

Phil,

 

 

You alway have the option of starting to polish it rather than to drive it at the limit...

 

😬

 

/regin

[F355GTS]

Good to hear Phil

 

Mark

[elie boone]

The rake is always set without the driver in the car.

So it depends on the spring rate how much rake you have left with the driver in situ.

[philwaters]

and how 'large' the driver is of course - Mark did ask if I was actually in the car as I'm a skinny bastrad

 

Interesting though as I've always done it with me in the car and pre-Ford axle/LSD era I have never had this problem.

I've ordered some shorter springs so that I can try it lowered a bit more as I've now run out of platform adjustment - maybe I'll have a play around now that I know I have a known good setting to fall back on.

 

Phil Waters