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MG MGA - toe in ?

Can anyone tell me if there should be any toe in on the stearing rack, and also if there is, how much ? Thank you in advance, Vin.
Vin Rafter

Vin

Parallel.

Steve
Steve Gyles

I remember setting about 1/8" toe in on mine over the years, I'll check the manual when I get home.
Russ
Russ Carnes

Russ

The manual says parallel.

Barney addresses the topic: http://mgaguru.com/mgtech/steering/sr106.htm

Steve
Steve Gyles

Parallel it is then! I remember (chancy at best) setting 1/8" in for gymkhanas / slaloms.
Russ
Russ Carnes

Just read Barney's thoughts which I am not sure are correct.

I found whilst racing that a bit of toe out make the front end turn in extremely well with the result that the steering becomes heavy. A bit of toe in makes the steering lighter and will make the car more stable by inducing understeer. This means that:

Toe out and the rear end will spin out.
Toe in and the rear end will push the car straight on.

Perhaps that is what Barney has said?

I have my car 1mm toe out but I also have negative camber on the bottom arms so the car is very lively. :)
Robert (Bob) Midget Turbo

I remember (chancy at best) setting 1/8" in for gymkhanas / slaloms. That would be toe in. Slight understeer seems to make it easier to transition to oversteer, or balance between. I had much less up to date tires then, and I don't have much opportunity to drive it hard enough to experiment now. I also have much wider wheels and tires now, it corners very well and is much fun to drive on the back roads without pushing hard. I am also conservative about driving fast now, people are much less predictable, and I don't want to break the old rat anyway.
Russ
Russ Carnes

Cars and the tires on them want toe as close to parallel as possible for tire wear and handling consideration. The reason toe in is often called for is to take up any slop in the steering linkage. The steering linkage in a MGA, the rack, 2 inner rod ends and two outer tie rod ends, does not leave a lot of play. In cars with steering box center link, idler arm and 4 tie rod ends there is more room for slop and most of them call for 1/8" before any wear sets in. Wheel bearing slop is also a consideration in our MGAs because it can't be adjusted out. Measure any slop in your car by pulling the front of the tires together and then pushing them apart while the tires are off the ground. Use half the slop as toe in. Otherwise use just enough toe in (1/32"-1/16") to know you are not toed out. Toe out causes handling problems and tire wear. A little toe in improves handling but too much also causes wear. If you notice tire wear that "feathers" the tread inward you have too much toe.
R J Brown

What handling problems do you think a touch of toe out causes Randy?
Robert (Bob) Midget Turbo

Each side wants to go away from the centerline with toe out. This causes pulls in both directions, a "nervous" feeling front end. Toe in is self centering.
R J Brown

The steering does become heavy with toe out and self centering does suffer a touch but there are benefits.

If a car is parallel then as the steering is turned the slip angles of the tyres and play in the steering cause the steering to be toe'ed in by a good amount depending on the tyre fitted. Thus the contact patches of both front wheels are not optimim and thus grip is reduced causing UNDERSTEER. Not a bad thing for the casual driver and the reason manufacturers set their vehicles up as such. Far better to lose control of a car with understeer than oversteer I am sure you would agree.

However with a touch of toe out in the same circumstances the slip angles and play in the steering make the contact patch of the front wheels parallel and thus grip is increased and the front end becomes very "pointy" and the vehicle turns in brilliantly. This is fine for the skilled driver because he can handle the backend stepping out if the speed is too quick.

Here again it is a safety concen to the competence of the driver. I personally enjoy driving a car set up in this manner and naturally a race car needs a front end that will turn in (watch clips of Moss driving a massa 250F) but everyone to their own taste so long as everyone understands what is the effect of each setting is. As you rightly say just a minute amount of oe in is the steady way!
Robert (Bob) Midget Turbo

Sorry to re activate this thread but having re read it I think it may be relevent to my particular (perculiar?) car.

The suspension on my car is lowered by 1 1/2 to 2 inches all round, has uprated front shocks, telescopic rear shocks, a front anti-roll bar and negative camber front wishbones. It corners almost flat with no roll and has really aggressive and instant cornering response but has a really hard ride.
At reasonable speeds this is fantastic and great fun but at higher speeds the steering response is so quick that sometimes the car almost gets away from me. This tends to happen when the car hits a large bump mid-corner when at higher speeds.

Looking at this thread again I wondered that if I also adjusted the steering so there was some toe-in, would this tone down the steering response a little.

It maybe could be a great way to adjust the car for either hard track-day type driving or for more relaxed long distance cruising.

It sounds as if Bob has a similar set up on his car but I would be grateful for anyones opinion.

Colyn
Colyn Firth

The car is obviously set up for competition work, not so great for daily street use, watch out for speed bumps. If you do competition fairly often, maybe you like it the way it is. Readjusting toe-in regularly can be a PITA. If you compete seriously you want it set for best competition handling, and probably leave it that way. If competition is rare and not so serious, and you have a lot of street use, you might consider reworking back to more original specification, especially near zero camber. Negative camber and/or any odd tow-in setting makes for accelerated tire wear. Low ride height can also be a PITA for real. I suspect the prior mods also include shortened and stiffer front coil springs, which are the likely cause of harsh ride quality.
Barney Gaylord

Hi Colyn
Sounds like a great car!!

The negative camber as you obviously realise helps to turn in the front end, especially on higher speed corners!! as you have found out. It works exactly on the same principle as toe out in so much as when you turn into a corner the tyre deforms and so the contact patch is optimised to full contact. However the inner (unloaded wheel) is exactly opposite and looses its patch completely but with no weight upon it who cares?

Caster on the other hand would sort that problem but is far better in slow speed corners.

Sorry I could rant on for hours and it could be all bunk!

I think Colyn that you ought to try and set the steering at 1 degree toe in and hopefully the steering will be more forgiving and it is the easiest option.
Alternatively you could try and place the normal bottom arms back on and set the Toe to help place the front end to how you like it.
Robert (Bob) Midget Turbo

Thanks Barney and Bob, I am going to experiment with the toe-in a little and I will let you know how the car responds.
When I first saw the car it was set up for racing with a full race engine and roll cage etc. The full race engine was swapped for an big bore MGB 3 bearing motor which is much more driveable on the road. I also had the option of converting the car back to a standard suspension but I loved the lowered set up once I had backed the shock absorbers off a little.
I hope I didnt come across as disliking the way my car drives because I love it, I was just wondering if it was possible to temporarily take the sharp-edge off the turn-in for long distance drives? European tours etc.
Thanks again
Colyn
Colyn Firth

This thread was discussed between 13/01/2010 and 07/02/2010

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