Swapping ends

[carlsberg]

I hope that someone can help me with sorting out the small and very scary problem with my HAWK strat.

I have just driven it on the road for the first time to the SVA test (passed)
The car had a mind of its own. Driving up the motorway at 65 mph the car wanted to wander all over the road, even on the straights.
the car has got 8 inch wheels with Dunlop 205 50 15 all new.

There appears to be nothing loose on the suspension and all of the shocks, struts are new.
I think that it could be a set up problem with the tracking and caster/camber.
has anyone got any basic setup details that work, so that I can set my car to this as a starter point.

I am used to rally cars and their foibles but this was scary!!!

any help or thoughts would be greatly appreciated..



chris

[kolynos]

I was talking to a friend of mine today who had exactly the same problem with his Hawk. Find someone who does four wheel alingment, just make sure that they CAN do it, someone who prepares rally cars for a living & that should sort it

[carlsberg]

Thanks for that, but do you have any idea what I should set the angles at

chris

[SUSIT]

I am no expert but I would start at the back and make sure the wheels are dead straight or slightly toe in but not toe out, Do you have ajustable spring seats and have you set the ride heights? changing ride height can alter geometry so set that first.
What size of wheels and tyres are you going to use?

[Sando]

.....I'd agree with that too Chris.
Toe in at the back and plenty of caster as you can get in the steering will both help no end with high speed stability.....and back to 'post SVA' ride heights ;) will make a big difference.
Toe in / toe out at the front and is then down to how you like your turn in..... toe in again, - very stable.
The ride height drastically effects this on a Hawk so you need to set up again if you lower it. (and re check the rack height for bump steer too :) )

Well done on the SVA. Look forward to seeing the car out.
cheers
Rob

[chris.richard]

I'm sure there are published geometry settings in this forum somewhere if you try searching.

[guy mayers]

Nobody has mentioned bump steer yet..... I assume you sorted that out first!
Guy
PS Congratulations on passing SVA - did it pass first time or was it a referral?

[colin artus]

Check your tyre pressures! You need about a 6 psi differential front to back and probably lower than you might expect ; try 18 front 24 rear as a start.

[SUSIT]

I'm sure there are published geometry settings in this forum somewhere if you try searching.


I tried that Chris, can only find figures for the Corse

[chris.richard]

Maybe on the newsletter cd? I thought Rutter Nutter had posted his settings.

[CorseChris]

I still find my Corse S a bit on the twitchy side (but in no way what I'd call scary) so at the weekend I set the rear toe to a fraction toe-in (from zero). I've yet to drive it like this though. I also fitted some 'cam bolts' to reduce the rear camber from just over 1 degree to about half a degree.

I know - two changes at once.......

At present, it's set to 3.5 degree caster, 0 degree camber and 1/2 degree toe-in at the front, 1/2 degree camber and hopefully 1/4 degree toe-in at rear. These are all DIY measurements and I'm not really hugely confident they are as I think they are so I'm trying to organise a sensibly priced setup session for it at the moment......

[colin artus]

Try this for a start: Front 4.5 deg caster, 1.5 deg neg camber and .5 deg toe-in.
Rear .5 deg neg camber and .5 deg toe in.

[Andy S]

I remember once at an Avon Park Single venue event after changing parts on both the front and rear suspension, we set the front and rear toe and camber by eye sight. We then went out for another stage and Dave reported, and I quote, "don't change anything, its brilliant!" Those were the days. Roll on Avon Park.

[SUSIT]

I remember once at an Avon Park Single venue event after changing parts on both the front and rear suspension, we set the front and rear toe and camber by eye sight. We then went out for another stage and Dave reported, and I quote, "don't change anything, its brilliant!" Those were the days. Roll on Avon Park.

Any events coming up Andy? :)

[Andy S]

When I said "roll on Avon Park", that should have been Abingdon. They stopped ralling at Avon Park two years ago. Its the only event in the diary so far. May be a shake down test coming up near Lincolnshire somewhere. Can't wait. We were flying last year at Abingdon. Dave was driving well and the car felt really quick. Heard that we might see the Steve Perez Stratos this year. Now that would be some carrot!

[Mark Cowling]

Hi Andy where abouts in Lincolnshire for the shake down , maybe Blyton? if so let me know the date its very near me, Regards Mark.

[chris.richard]

Try this for a start: Front 4.5 deg caster, 1.5 deg neg camber and .5 deg toe-in.
Rear .5 deg neg camber and .5 deg toe in.

Is rear castor not adjustable? Does it need to be zero?

[Andy S]

Hi Andy where abouts in Lincolnshire for the shake down , maybe Blyton? if so let me know the date its very near me, Regards Mark.
Not sure. Dave has been before. Will let you know when we go. Will post it on Stratos events. Might get a few takers. Its only 45 plus vat for the day. Can't be bad! Good for testing those all important geometry changes with a bit of space to spare.

[guy mayers]

Is rear castor not adjustable? Does it need to be zero?

Rear castor is irrelevant I think! The reason for castor on the front is to get some self centering and feel through the steering, the more castor the more it want's to return to the straight ahead position from left or right lock and I'd recommend as much as you can wind on. If memory serves me right the Fiat X19 has around 9 degrees but I stand to be corrected.
If you have rear wheel steering then something needs fixing! Probably the leading link bushes or rose joint.
Guy

[chris.richard]

So the rear struts should be plain upright then.

[strat6v]

something like. Mine look to lean forward a bit but maybe thats cos ive got one eye further up my head than the other and i was looking sideways :D

[Chris J]

The top part of a Hawk rear upright slopes forward. I hadn't realised that until recently.

[Chris J]

Unless we're both seeing things?!

[carlsberg]

Wow this has started a bit of a discussion.
I will check all of the settings and try some of the settings mentioned.
there is nothing loose or worn. that has already been checked.
I have also been told that the Dunlop D02J tyres on it do have a tendancy to wander at slow speeds and only work at maximum attack. Tyre pressures are a good point though.

Does anyone out there have a remote brake servo to give the car a bit more stopping power. Already biased.

The car passed the SVA test on a retest, only because the new speedo and sender unit didnt give the right readings on their rolling road. (non linear) i bought a new speedo and sender (same type) and fitted and recalibrated it. Took it to Chadderton and put it on the rollers. It gave the same readings as before. After a long discussion with the testers boss, the car was taken for a road test. It passed!!!
Their rolling road was faulty!!! I still had to pay the retest fee. I am now waiting for the DVLA to come out and inspect the car as they now have to inspect every car. They don't believe the receipts........
I want to set the car up properly for stage rallying but dare not strip it out until the DVLA man has been. I am told this could be up to a month.
Entry in for the first event 9th April. its going to be close.

[CorseChris]

DVLA won't inspect any SVA type issues - they only look at things like engine & chassis number, donor parts (if you are trying for an age-related plate) that sort of thing. My local VRO wouldn't accept the SVA certificate or MOT as proof that the chassis number they'd given me had been adequately applied despite the fact that both clearly showed the same chassis number. Different department, different remit.


..so I'd feel free to change settings and parts as long as it won't compromise any potential donor items you may be claiming.

HTH

[catswhiskers]

[QUOTE=carlsberg]

Does anyone out there have a remote brake servo to give the car a bit more stopping power. Already biased.

QUOTE]

Try Staffordshire Vehicle Components in Tamworth. They do a twin circuit servo for a good price. I've just fitted one, very neat and compact unit but with the inclement weather, I'm waiting for a dry day to fully road test.
I think their web site is something like www.svc.co.uk

Mick

[catswhiskers]

Well, I was nearly right. Its www.s-v-c.co.uk :D

Mick ;)

[Martin K]

Does anyone out there have a remote brake servo to give the car a bit more stopping power. Already biased.

If the brakes have a kind of 'dead pedal' feel to them it maybe that your master cylinders are too large. What size front/rear master cylinders are you running? A lot of people forget that with a twin master cylinder/bias pedal box the actual leverage that your 'foot power' has over each cylinder is half that of a single master cylinder. Either more pedal leverage or smaller master cylinders are therefore options - as is the option of fitting a servo.

The Hawk pedal box has a relatively low pedal ratio - on the brake pedal at least. If you can't modify the pedal ratio on the brake pedal (by moving the pivot) to increase the mechanical advantage, changing to smaller diameter master cylinders would increase the braking power and give better pedal feel.

This would be a lot cheaper than the servo option!

Getting the bias adjusted right is important, as if not set up correctly the car will not want to stop.

Pad material can also make a huge difference to stopping power what are you using at the moment?

On the subject of your wandering rear end, castor in the rear suspension is not in itself an issue. What is important is that you minimise any rear bump steer and ensure that at no point in the rear suspension travel do you end up with toe out on either rear wheel - and you must also allow for flexing in the trailing link pivots under acceleration and braking when setting static toe in. It is also VITAL that rear toe is set relative to the center line of the car, rather than across the pair of wheels, as a net 1 degree of toe in could be the result of having one wheel with a toe in of 3 degrees and the other with a toe out of two degrees. Set like this the car would wander all the time.

If you find that the rear toe is not the problem then where else can you look to solve the problem?

Rear camber changes can also create a rear-steer effect, as the 'load' point on the tyre wanders across the tread during suspension movement due to camber changes. This will depend a lot on the tyres in use. As someone has already told you to expect wandering on the Dunlps at low speed, it would suggest that the tyres need a fair amount of camber thrust before they settle down, and camber thrust is a function of speed and camber angle. Negative camber is far more stable that positive camber. If one rear tyre goes to positive camber at any time it will try to pull the rear of the car 'out' on that side.

For performance, I would have thought that 1 to 1.5 degrees static negative camber might be better on the tyres you have, even at the expense of a little tyre wear.

Please report back with your results as this is an interesting problem. (To me, anyway!!)

[chris.richard]

It is also VITAL that rear toe is set relative to the center line of the car, rather than across the pair of wheels

Martin, on the Hawk chassis, can you use the lower chassis rails as parallel to the centre line?

[stratosphere]

when were talking bout this issue..

Has anyone here driven their car at + 200kph/130mph? (+ 250??)

Experience?
Are one scared?
Only suitable to do this on "dance floors" or it's a "walk in the park" even on bumpy and bad roads?
Severe lift tendencies?
If everything is aligned then ...... if not RIP???
GP4 or not

Please share your knowledge (and tell what chassies/car Hawk, Corse, original etc)

Luigi, eagerly awaiting his Hawk

[rutthenut]

Speed > 130mph? Yes, with my Stradale Hawk HF3000.

Had the car set up so that it tracked nice and true, surprisingly.

On a race track surface, this is no problem at all.

On motorway-type roads, usually fine.

On Belgian motorways, I found it better to increase speed a bit more ;)

[PANOS]

(In my dreams, officer...) I do 140MPH/225KPH (7,000RPM-5th gear) on the motorways with no problems, apart from the oil overheating (but I am sorting this out soon...).
Mine is a Trasformer(Hawk)/Spyder chassis - Beta 2L tuned engine...
Settings:
Front - Caster 5degrees / Camber - 0.5degrees / Tow-in 1mm
Rear - Caster ???????? / Camber - 1.5degrees / Tow-in 1mm

Tyres:
Front - 225/50R15 / Rim 8x15 / Pressure 20psi
Rear - 255/45R15 / Rim 10x15 / Pressure 24psi

CIAO PANOS

[Martin K]

Martin, on the Hawk chassis, can you use the lower chassis rails as parallel to the centre line?

I believe they should be parallel and equidistant from the centre line, yes, as the lower inner suspension pickup point is mounted on them.

[Andy S]

I know Dave Watson uses Green Stuff pads in his. Massive improvement over previous ones. Good from cold aswell.

[carlsberg]

thanks for all the help so far. lots of ideas and helpful suggestions. This week i will be mainly trying to sort the car out. I must admit the car is more stable now the tyres have been scrubbed in (at sensible speeds of course) but I am going to fully check and document what i do to it.
Also brand new servo and proper pads coming on monday.

chris

[chris.richard]

Also brand new servo and proper pads coming on monday.


What sorts?

[chris.richard]

Try this for a start: Front 4.5 deg caster, 1.5 deg neg camber and .5 deg toe-in.
Rear .5 deg neg camber and .5 deg toe in.

Colin, are these toe-in figure for each wheel, or in total?

[Media]

Hi Chris,

My new build Hawk had its first four wheel alignment before the SVA test by a local garage that does four wheel alignment for Rally cars, during this time I did around 500 miles, I was told that this would enable the suspension components to bed in. I had the same problem that you've experienced. Since that time it has received its second four wheel alignment and now it is handling is spot on, with no wondering. I have a print out of the final test results if you would like a copy please let me know and I will fax it to you.

[carlsberg]

yes please a copy of the details would be good for my information and records. I have no fax, could you email them or personal message them to me.

Any additional help would be appreciated, what sort of spring rates have you got

chris