Front wheel alignment / toe-in

[jon_cox]

Anybody got any views on the correct degree of toe-in for the roadster.
The marina manual says anywhere from parallel to 0.5 degrees. Seems a bit vague to me.

Cheers
Jon

[stevejgreen]

Re: Front wheel alignment / toe-in

Those are default numbers for a Marina car, the Roadster has very different weight distribution with the axle centre line in front of the engine and not behind.
As with every part of a Roadster suspension, the standard Marina settings are only a starting point, and not necessarily a desired destination.

[h_m_cumming]

Re: Front wheel alignment / toe-in

I run mine at 1.5/2 mm toe in on the rims. Don't ask for degrees since I do it myself. Tyre wear seems right and steering is fine, not too heavy and a degree of self centering.

[Sidon]

Re: Front wheel alignment / toe-in

Excuse my ignorance. Is that 1.5mm each side or overall?

[jon_cox]

Re: Front wheel alignment / toe-in

Thanks for all the replies.
Steve, I did search through your excellent document resource which is where I found the 0-0.5 degree values as my Marina manual only gave the 1/16in value and as I do could not find the originl tyre size for the Marina I was struggling to get an angle value. I do have the Haynes Roadster manual and that also suggests 0-0.5 degree so this seems a good starting point.
Hugh, Your values give approx. 0.3 degree (each side - total 0.6 degree) assuming 13" rims. Do you use the string method to set yours up??
I have 15" wheels on my Roadster now so I am going to try 3mm toe-in on the rims EACH side (Sidon) and report back.

Slightly different but related subject.
What is the best method to centre the rack. I have done it by simply finding the mid-point of the lock to lock at the steering wheel. I assume this is good but would like confirmation as I am trying to reduce the bump steer a much as possible. I know that some steering racks had more lock on one side than the other (Triumph were good at this) so my method might be unreliable.

[stevejgreen]

Re: Front wheel alignment / toe-in

As I understand it, on a road car, toe in is actually designed to essentially take up the slack, ever present in steering mechanisms, so that the tyres, in normal service actually rotate parallel, so it’s an approximation at best. Of course as you change wheel size, since you are measuring from the rim, you will have to compensate for the error, even though it will be quite small.
Most Marina racks that I have seen have a removable plug in the centre of the rack, intended as an oil filling point, this doubles as a location for a centering pin. I would have thought that given that the Marina steering shaft is expended between the top and bottom universal joints, that it is more reliable to set the steering wheel centre at the same time as you set the toe in.

[h_m_cumming]

Re: Front wheel alignment / toe-in

OK pic shows the jig I've made to set toe-in on the Marlin. Each end is level with the centre of the wheel when sitting on a flat surface. It's important that the whole car is on a flat surface to start with. To set the rack wind it from lock to lock and count the turns then half way back to centre. (I've found the hole in the rack method to be out enough to have one trackrod end almost out of thread and one bottomed.)
Now fit your steering wheel to be central and lock it if you can. Next sight along each side, or use a string, to see which rod end needs to go in or out so that once the jig is in place at the rear of the wheel with one side touching the rim and you've measured the gap from the other to the rim, I've made mine about 20mm gap, Transfer the jig to the front and do the same. The difference is the toe-in or out. If the wheels were pointing to ,say, the n/s when you had the steering wheel centered and used the string method then adjust the apropriate rod end, maybe both, to get the wheels pointing ahead with the correct toe in.
Sorry it's so long winded but doing it is very easy and only takes less than 20 min. unless you've got arthritic knees like me.
Toe-in is overall 1.5/2 mm.

[andyf]

Re: Front wheel alignment / toe-in

Thanks for all the replies.
Steve, I did search through your excellent document resource which is where I found the 0-0.5 degree values as my Marina manual only gave the 1/16in value and as I do could not find the originl tyre size for the Marina I was struggling to get an angle value. I do have the Haynes Roadster manual and that also suggests 0-0.5 degree so this seems a good starting point.
Hugh, Your values give approx. 0.3 degree (each side - total 0.6 degree) assuming 13" rims. Do you use the string method to set yours up??
I have 15" wheels on my Roadster now so I am going to try 3mm toe-in on the rims EACH side (Sidon) and report back.

Slightly different but related subject.
What is the best method to centre the rack. I have done it by simply finding the mid-point of the lock to lock at the steering wheel. I assume this is good but would like confirmation as I am trying to reduce the bump steer a much as possible. I know that some steering racks had more lock on one side than the other (Triumph were good at this) so my method might be unreliable.

Tracking does have an impact on handling. The ideal for a road car is as Steve says to have it setup so that as the car is in motion the front wheels are running parallel. With the Marina setup with the rubber tie rod bushes a small amount of toe-in is required to allow for the drag on the wheel pulling the suspension backwards. So that makes for safe predictable handling under cornering and braking. Adding toe-out will make the car unstable on braking but turn in quicker. On the rally car we used to run it with 1 degree of toe-out because these characteristics matched what we needed, but that's not what I'd run on a road car

[stevejgreen]

Re: Front wheel alignment / toe-in

Tracking does have an impact on handling. The ideal for a road car is as Steve says to have it setup so that as the car is in motion the front wheels are running parallel. With the Marina setup with the rubber tie rod bushes a small amount of toe-in is required to allow for the drag on the wheel pulling the suspension backwards. So that makes for safe predictable handling under cornering and braking. Adding toe-out will make the car unstable on braking but turn in quicker. On the rally car we used to run it with 1 degree of toe-out because these characteristics matched what we needed, but that's not what I'd run on a road car

Spot on with my ideas. Yes it’s essential to make sure that all bushings etc are in perfect condition (superfled discussed at length)
What the Marina ‘ideal’ numbers are are largely irrelevant, only a starting point from a car with completely different characteristics.

It’s a suck it and see question, not a defined science, it’s how you want to set up your car to your requirements.

There were claims in the past , that Roadster chassis manufacturing tolerances were poor, not properly jigged etc. Very little evidence is available, but unless the geometry is consistent side to side, you are always going to be on a compromise.

[velovol]

Re: Front wheel alignment / toe-in

I'd just like to add to the steering rack set up discussion. Earlier on I used to race Karts (Class 1) and found the length of the steering arms to be very important to handling and need to be equalised
I'd suggest find the centre point of the rack movement then lock the steering, a Mole wrench on the steering column for example. Set the steering wheel on the splines to straight ahead. Disconnect the ball joints and set the wheels to straight ahead using a timber batten or angle iron between front and rear wheels.
Loosen off the locking nuts on the steering arms and adjust the lengths until they drop into the tapers comfortably. Measure the length of each arm and hopefully they will be almost identical. You can then set up your toe in. If there is a big discrepancy in lengths you might need to look at suspension mounting points

I've found 2 to 3mm of toe in works best for me with 15 inch wheels.

[leadfoot]

Re: Front wheel alignment / toe-in

Hi Jon, don't forget to make sure you're happy with the camber settings before you adjust the toe. I used similar settings you propose on my 5exi. Btw 0.5° is 3.3mm on a 15" rim.
I made a jig for setting the camber by having two bolts set 15" apart in a piece of aluminium angle iron. I set the top bolt 3mm further in to get negative camber. With the spirit level taped to the jig, when the bubble was level I knew I had 3mm negative camber.
I then used the string method to set the toe, front & back. First I put thin wooden sheets under the wheels where required and used a spirit level on parts of the chassis to make sure the car was level. I used two axle stands on one side at a time which were set 1ft beyond each wheel. I wrapped some heavy duty fishing line around these and set the line 75mm from the centre of the wheels so that the line was parallel to the car. I simply made sure I measured 3mm more at the front rim than what I got at the rear rim on each wheel. Hey presto, approx. 0.5° toe in.
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[h_m_cumming]

Re: Front wheel alignment / toe-in

A point on the Roadsters, you will need to put a packing spacer, about 5/6mmm between the n/s bottom suspension mount and the chassis to get the camber the same on both sides. Marlins chassis jigging wasn't brilliant.

[stevejgreen]

Re: Front wheel alignment / toe-in

A point on the Roadsters, you will need to put a packing spacer, about 5/6mmm between the n/s bottom suspension mount and the chassis to get the camber the same on both sides. Marlins chassis jigging wasn't brilliant.

How much evidence of this problem is there? I have read stuff on this forum, but the author never went into detail.
I checked mine, as best as I could, tape measures, levels and inclinometers etc, and could only find a couple of mm and d3cided that was within my acceptable measuring tolerance and would be heading for a total rebuild just to chase the error.

On other settings, Camber castor etc. there is no scope for adjustment on the standard Marina. But on a Roadster check the assembly of the Mini Top Arm, I had to re-shim mine to get rid of excessive play. Article in Pitstop.

[h_m_cumming]

Re: Front wheel alignment / toe-in

Well I've known four inc. my own. You only have to put it on a level surface with the wheels straight ahead and look from the front. Bet the o/s is leaning in and the n/s is leaning out. But each to their own.

[stevejgreen]

Re: Front wheel alignment / toe-in

A list of chassis numbers might be interesting, or do you say all Mk 2 Roadsters?