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MG Midget and Sprite Technical - Caster Problem?

I've just had the frog suspension checked as I was getting fed up with virtually no self centering at all. The front has been modified with the frontline kit.
It turns out that there was 2'35" of toe out which was adjusted to 2'0" of toe in, which helped considerably. However the caster angle is N/S(Left): 0'53" & O/S (Right): 0'42" whereas the manual says it should be 3' 0" (the 'is my attempt at degrees, not feet!)
Has anybody else had their caster angle checked? If so what was the result?
The camber results were interesting as well, N/S -1'25" and O/S -2.16".
Trouble is I don't know enough about the subject to know if these differences are critical or not! And if so what can be done about them?
Graham.
Graham P 1330 Frogeye

Graham

can't help with adjusting the caster angle, it is built in by the curve in the front chassis legs.

The only way I can imagine losing three º is by some idiot* bashing the front of the chassis down flat or by same or similar idiot welding chassis extension legs to repair damage caused in a bump or by rot to the front end.

The front extension legs are upcurved in construction to provide the threeº necessary. Which means no alteration should be possible.

You can see the relevant curve being built in at the BMH factory visit a couple of years ago (the shell being built is a 1500 but that part of the chassis is the same across the entire Spridget family)

And the other thing is

to make the º symbol is easy

hold down the ALT key and type 0186

like so ººº.......

hth

*definition of idiot: owner of LRA===D trying desperately to flatten the curve by bolting the front chassis rail to the floor of garage and two people jumping up and down inside the cockpit hoping to repair the suspected damage...

Luckily I/we failed...



Bill

Ahhh - a quid for every time you've used that photo to illustrate the answer to this FAQ, Bill!

Steve Clark

ººº

oh yeah!
Steve Clark

Hmmm not sure the chassis turn up adjusts the caster angle but I may be wrong, just can't see it. However the caster angle is manufactured as a result of the kingpin angle when viewed from the side. This means that the bottom fulcrum needs to be further forward than the top fulcrum of the king pin and will thus cause the king pin to be slanted when viewed from the side. Too much caster angle will cause the steering to become very heavy but the car will be very grippy in tight low speed corners. The spidget body shells were less than perfect when made so these kinds of figures were not unknown. However 1/2 degree does sound small.
I would agree however that any repairs around the suspension points could cause these figures to change. I would tend though not to worry about it. As you say self centreing is sorted by a touch of toe in although I have always set my steering at 1/2 degree toeing out. I find this makes the car brilliant on turn in.
Bob (Robert) Midget Turbo

Just considered this a little more and thought that the angle would put the bottom wishbone in a perfect position to have a slanted kingpin. Without the angle the slant in the kingpin would put a load on the bottom fulcrum so whilst the upturn does not cause the caster it certainly stops undue wear of the bottom fulcrum as a result of it. :-))
Bob (Robert) Midget Turbo

Graham,

It seems to have been mentioned many times on this BBS that people don't realise that the negative camber on the FL kit is achieved by a shorter top link which results in toe out unless the tracking is properly adjusted after fitting. Is this a FL documentation failure or a RTFM failure, I don't know.

Bob,

After reading your post I think you may want to read it again. The upturn is for the provision of a caster angle. Due to the nature of the design of the wishbone and upper link trunnions the kingpin has to be perpendicular to them so the upturn is what provides the kingpin inclination, and therefore caster angle, when viewed from the side.

David Billington

Yes that is what I tried to say in my second post on the subject. However it does not cause the caster it only acomodates it is what I was saying. As I said without the upturn the bottom wishbone would not be at an angle that allowed the kingpin to aim directly at the set back top trunion and thus wear would result in the botton pin. As we have said to create caster the bottom trunion needs to move forward of the top mount, this is not achieved by the upturn is it.
Bob (Robert) Midget Turbo

Robert,
I disagree.
The upturn in the chassis legs also has the effect of canting the shock absorber mounting plate back at an angle. It may be a crude way of achieving the caster, but that is what it does.

If the caster was achieved by the manufacture of the king pin, then they would have to be handed, which I am pretty sure they are not.

Guy
Guy Weller

correct Guy, the kingpins are not handed.
David Smith

ººº

you liked that Steve?

Bill

Thanks for all of the replies guys, I knew about the upturned chassis legs but didn't know if there was any work around to gain some caster. I thought it unlikely but unless you ask, you don't find out!

Dave B, I fitted the frontline kit and then had the tracking set up by a tyre place, obviously not too well! It is actually in the documentation but they give it as 1/8 inch toe in when as far as I'm aware everybody nowadays uses degrees.

The place I went to in Maldon, specialises in modified suspension and tyres for modern cars and has a computerised set up which uses lazers and cameras to align everything. The operator seemed pretty knowledeable but hadn't seen a sprite before but got the figures from my manual and away he went.
Graham.
Graham P 1330 Frogeye

The caster is pre set by the chassis but only if the chassis is running parallel to the ground. If the rear is higher or lower than the front then the caster would be lowered or raised accordingly. Something a lot of kids learned the hard way back in the 60s when the rage here in the US was to raise the rear of the car quite high to clear huge tires.
Bill Young

Graham,
unless you have a RWA the fancy laser set up jig they use for modern cars doesn't fit a SWA, my garage wouldn't touch it, so i bought an old type camber gauge off of evil bay & did it myself.
Must say the FL kit is well worth the money.

Brad
Brad (Sprite IV 1380)




HMMMmmm, I must note be vary special...MY Degree thingy dosnt work...is it differant here in the states


I tried holding the "alt" then typing 0-1-8-6 (with out the dashes), and then tried alt and doing the 0186 at the sametime....oh well. life goes on.


prop
Prop

Im curious,

Was the suspenion, in proper order Before you installed the FL kit, if so what changed, did the car fall off the jack stands, was the wieght of the car supported by the chassis leg itself? ect.

I have never done Or seen in real life the FL kit, but I think it was just a bolt on and go kind of thing,

something was not right before, something happened during the time of install, the kit was not installed correctly, or a manufacture defect. one of those 4 options....find the correct one, you will find your problem area.

prop
Prop

I must be 'Special' too as that doesn't work on my PC either, I hope i'm not quite a 'Special' as Prop though.
Brad (Sprite IV 1380)

You have to use the numbers on the "10 key" number pad.
Trevor-Jessie

Thanks Guy I bet I made the same mistake the last time we discussed this issue. When I think about the caster normally I always seem to forget the shocker mounting is upturned as well.
So I am going to have to commit that to memory as I never work it out by thinking about it!!
Bob (Robert) Midget Turbo

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Errr, i must be special i can't get it to work, i even managed to get the number pad to give me letters?
Brad (Sprite IV 1380)

Talking about caster and camber, why do the front wheels of a Merc lean over at that extraordinary angle when on full lock. They look really weird! Anyone seen that?

Guy
Alt 0186 doesn't work on my laptop 'cos it doesn't have a keypadontheside.
Guy Weller

Brad, all frogeyes are RWA so that shouldn't be a problem.
Prop, nothing untoward has happened to the frogeye since I owned it, but before, who knows? The Frontline kit is a "simple" bolt on (took me about 2 hours a side with new springs), however you do have to have the tracking reset after fitting. As Dave B said the kit alters the camber angle, plus you are disturbing the position of the steering arm in relation to the rack, so the tracking will be out.
Graham.

Graham P 1330 Frogeye

Guy the reason is that unlike the midget the Merc has a lot of caster on it which makes both wheel tilt the same way when in lock. Unlike camber which has wheels leaning in opposite directions when not in lock. Which is why on very tight twisty roads (where alot of lock is used) caster can be very useful
Bob "My E 250D has a lot of caster!" England, obviously with German sympathies!!
Bob (Robert) Midget Turbo

°º½¹¸»

works for me

but I wish the ornerary one worked proper like...

Alt0176=°
Alt0186=º (slightly lower º)
Alt0189=½
Alt0185=¹

maybe it depends on the typeface/font you use

who knows?

but it does need the numerical section enabled

maybe it neds "num lock" on too, mine always is
Bill

°°°°°°°°°°

I always did this by typing the letter "o" very, very, gently.

-:G:-
Gryf Ketcherside

I dont have the 10 key number pad on my lap top also...It would be cool someday to learn what all these little squiggle keys actually Do....But not tonight or anytime soon, I like the fact that my computer is working fine, so no scence trying to fix it.

lol.

prop
Prop

This thread was discussed between 11/11/2008 and 13/11/2008

MG Midget and Sprite Technical index

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