Steering Angle/self Centre

[WallerZ]

Afternoon all, I have found that my steering angles are probably completely wrong to the extent that on full lock, the wheels are so tight they skip and jump instead of rotating and turning the car resulting in a poor turning circle. Plus, there doesn't seem to be any self centring of the steering wheel which is an IVA fail I believe?

 

How much angle should I expect and how should I be setting the steering up?

 

Cheers,

Zach

[speedtripledan]

That will be toe settings causing that I ususlly go fir slightly toe in

[Guest Alan_builder]

That will be toe settings causing that I ususlly go fir slightly toe in

 

I think that just knackers one edge of your tires and you have 2 steering wheel settings for st. on.

 

I think you need to adjust the top to bottom position of your wishbone ball joints for the wheel. Top position back and or bottom position forward to increase self centering.

[Guest MarkB]

I agree with dan, get tracking gauges on, try setting parallel first, see if this remedies the self centring problem, if it does either leave it at that or have a little tweak.

[Shaft]

Self centering is alot to do with castor angle as already mentioned by Alan above.

Probably a daft question, but have you got the top wishbones on the correct way round?

[sj-bradley]

If they are similar to my zero, it was not possible to put them on any other way round as the shocks would not fit.

 

Is the steering lock too severe? Does the Mazda steering need modification to reduce turning circle? I don't know enough about that rack.

 

Simon.

[speedtripledan]

 

 

I think that just knackers one edge of your tires and you have 2 steering wheel settings for st. on.

 

I think you need to adjust the top to bottom position of your wishbone ball joints for the wheel. Top position back and or bottom position forward to increase self centering.

if you have serious levels of toe in or out then yes 1/2 deg will cause no wear to tyres what so ever. My atomic and stykus are both toe in. The castor is designed in by gbs and not adjustable other than maybe a few washers on the wishbone mounts. My atomic was 1.5deg toe out on the ns front and parallel on os net result I could not push the car with steering turned set them to both 1/4 toe in and hey presto no resistancer car was pushable and went from scitish on the rd to stable

[Snapperpaul]

For IVA only set tyre pressure to high, about 30psi and have a degree of toe out, this gives enough self centring to pass IVA

Once you have NAC in hand reset tyre pressure to 16 to 20 and set toe in to 1/2 degree then drive and try different settings

I agree that caster and camber should be looked at, Haynes Riadster manual has some base settings

Edited September 1, 2013 by Snapperpaul

[Bob Tucker]

The toe in/out is designed to set the wheels parallel once the car is on the move.

RWD cars have a slight resistance to the front wheels,which takes up any slack in the bushes, hence they need toe in

On FWD cars the front wheels are pulling the car forward, again removing any slack from the suspension & steering,

& ending up parallel after starting with toe out.

 

on full lock, the wheels are so tight they skip and jump

That sounds like too much lock, upsetting the ackerman angle, which turns the inside wheel through a tighter circle in a turn.

Or the entire steering geometry could be out....cant help with detailed set up as I dont know the MX5 based version.

Self centering is usually dependent on the caster angle, as that uses the cars weight to re-center the steering,

(hence we need more that the Sierra) but in my experience a touch of toe in also helps.

As you can see......its a real can o' worms!

 

Pick any one of these for an afternoons light reading...

https://www.google.co.uk/search?num=40&newwindow=1&site=&source=hp&q=car+steering+geometry+explained&oq=car+steering+geometry&gs_l=hp.1.1.0l3j0i22i30l4.1165.6618.0.9180.21.18.0.3.3.0.150.1355.14j4.18.0....0...1c.1.26.hp..1.20.1220.5p3O7qe40OQ

[Guest mower man]

I am not familiar with the mazda front suspension set up so may not all be correct . Setting up angles should be done in a particular sequence 1 ride hieght ,this can effect /change camber so needs to be set first 2 caster can affect track [toe in /out] so set second 3 toe can affect straigt line stability /tyre wear / steering feel ideal is parralell but slight toe in is ok. Settings should be very close to mazda specs . Self centring is a product of caster as said above genalleraly 7 's run around 5 to 8degs to much give heavy steering not enough light wandery effeect ,hope this helps it can be a black art but record all settings and road test to get correct feel , I understand thats awkward with a new build so go for std settings mowerman

[WallerZ]

Its actually a mk2 escort rack, gbs said it was too much to change for the mx5 rack or something.

It does feel like the problem with the steering lock is causing the wheels to jump, how would I reduce the steering angle?

There has been no proper tracking or anything done for the car, mainly put on and done by eye so will need some proper gauges. Does anybody near me have a set and able to pop in one evening/next weekend?

Unless it's left and right, I can't see the wishbones going on any other way... I'll try get some pictures up soon

[Guest Alan_builder]

Hi Zach,

 

I have just had a look at your build pictures. There may be an optical illusion but it looks like you have 20 yes 20 degrees of toe out.

 

Put 2 2m pieces of wood one on the Center height of each wheel, supported at each end. Have the bits of wood going forward from the back of the front wheels. Push the wood up to the front wheel tires ok but there may be a small gap, just do your best. Now measure the distance between the bits of wood at the end furthest from the car and check that the distance just in front of the car is the same.

 

You can do some maths and work out what toe you have by taking the distance between your measurements and using sin / cos.

Do get bits of wood that are not bent!

 

If I am correct at 20 degrees toe out you may get skipping because one wheel gets too crosswise to the direction of travel.

 

PS you can use a spirit level to check the wheels are upright, just mind the bulge in the tires at the bottom.

[sj-bradley]

It is difficult to judge looking at photos from the front of the car as you do have the parallax problem and it makes the wheels look really bad.

 

Question, can you push the car on a smooth surface like a polished / painted garage floor easily - with no sounds of squeaks from the tyres?

 

If the answer is no, then you have a problem as I found out. Once you can push the car easily without it making tyre noises, you are close.

 

As Alan says above, getting some straight bits of wood on the front wheels will tell you what the toe in /out is. (with some maths)

 

Simon.

[WallerZ]

I'm guessing the norm is only a few degrees and of toe in?

 

I've just seen the photos and yes, it does look bad from them. From what I can see looking at the car, it is an optical illusion of the photo as the wheels appear fairly straight (used loosely) when looking at the car. I'm going to have a look tonight and see what I can figure out.

 

I used to push the car in and out the garage before the engine was running. Was quite easy and don't remember any major sounds that I wouldn't expect from a tire rolling....and it's not smooth or polished, its just concrete. I think the camber is badly out, the toe was done by eye originally to begin with before getting professionally checked after IVA

[Guest mower man]

Iwould doubt if it's a no of degs ,more likely 1 or less as a max and if camber is out that will compound the prob,all angles should be done before Iva other wise you will have probs with no self return or very heavy steering please read my earlier post and correct the angles as nec and you will find the prob should dissapear mower man ps camber should be in the area of 1/1.5 degs negative