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MG Midget and Sprite Technical - neg camber, with the frontline kit.

I have seen various references to -ve camber with the frontline shock kit..

I have the old original kit on mine, and I understand this has now been seperceded by a modified kit, that has LESS neg camber. Is this true?

I have also seen references to people fitting modified top trunnions to alter the camber.

I've had search but can't find the specifics I want.

Can someone please kindly point me to the appropriate thread about altering camber via the top trunnion?

Thanks in advance.
Lawrence Slater

I not sure you're right (or even wrong) but if it helps I think I've got the lastest Frontline front kit, fitted 2 years ago, and it was quoted at -2
N Atkins

Peter May does a Top Trunnion conversion kit. Fitted to mine and many other race cars and an easy mod. Here -

www.petermayengineering.com

Rgds,

Nigel
Nigel Pratt

Thanks for that link, I'll check it out.

I might well be wrong Nigel, I jus't can't find the thread I read, where I (think I read ) read about 1 degree neg camber instead of two. I didn't pay close enough attention at the time, and didn't bookmark where it was. But if as you say the current kit is 2 degrees, I must have imagined it or mistaken it for something else.
Lawrence Slater

There are books with this stuff in....

The kit cannot be quoted as giving a specific amount of negative camber because it will vary with how much, or not at all the car is lowered at the front, or even whether 1275 or 1500 stock ride height.

There are also other factors which will vary how much negative camber or not, you get with the Frontline kit.

The only real certainty is 'probably' whatever your car has by way of camber, likely to be degrees positive, the frontline kit moves it in the direction of negative by 2 degrees. So if your car has 3 deg pos the frontline kit might change it to 1 deg pos. If your car has 2 deg pos the frontline kit might change it to zero. If your car has 1 degree pos the frontline kit might change it to 1 degree neg. Etc.
Daniel Thirteen-Twelve

It says one degree in the text here http://www.frontlinedevelopments.com/products/sprite/frontsuspensionkit.shtml , maybe it's a compromise as Daniel has mentioned that some cars, 1500s?, have different negative camber than others due to difference in the pick-up points IIRC. Might be 1500s lowered give reduced camber. Certainly the originals are 2 degree negative.

Says 2 degrees negative here on the old site http://www.mgcars.org.uk/frontline/frntsus.htm
David Billington

David,

Thanks so much for that, I really was beginning to believe I imagined it, and that meant that my aged brain had deteriorated further than I thought :)

I asked about this, because ever since I fitted the FL kit, my car is noticabley visually, neg camber, at least I could see the difference compared to the original shocks.

Since fitting it, I also have a pretty twitchy front end. I have played with toe in and got it the best I can with decent tyre wear vs being very sensitive to steering wheel movement.

So I figured if I reduced the neg camber, I would I get back some of the original handling which to my mind was more forgiving, -- presumabley understeer.

I only really changed to the FL kit because I was fed up with the crap recon lever arms I seem to get through all too quickly, so the AVO teles clinched the deal.

So as I had money to waste 10 plus years ago, I decided to play, but apart from the great teles, I wasn't that excited about the very responsive steering resultant from fitting the fl kit.

Maybe because I was so used to the original handling (sloppy some call it, but I liked it), I still haven't gotten to really like it.

I've been reading around for methods to reduce neg camber. Most references are about increasing it for obvious reasons. But one posting, by Rob I think, mused on the possibility of raising the rear of the standard shock to induce more +ve camber. So I'm thinking I could do the same on the FL housing. (with a wedged plate for example).

Any thoughts on this, apart from go back to standard lever arms?

I'm looking at Austin westminister double lever arm shocks too, but before I go there, I thought I would explore this first, as I haven't yet managed to buy the westminister shocks yet anyway.
Lawrence Slater

with FL I not surprised their info varies even on their web site(s) - I'm surprised it doesn’t say something like minus nought degrees or positive nought degrees

Daniel,
how much degree difference would you reckon on a car that’s dropped about an inch (despite being told by FL the drop would only be half an inch, then later three quarters of an inch) please

Lawrence,
- can't resist it - twitchyness was your old tyres :)
N Atkins

Lawrence

What ARB & spring rate are you running on the front? negative on std rates could indeed make the car twitchy.
Paul Walbran

standard springs (but new 10 years ago when fl kit fitted), standard arb.

I didn't know that without the uprate arb the -ve camber would cause a problem.

I've got a 5/16s arb in the loft. I fitted it at the same time as the fl kit, but it ripped out a roll bar bracket on the rusted near side.

As a temp measure I bolted through the chassis leg and put the 3/8ths back, and after about a year I put a repair chassis section on, but didn't refit the 5/16 arb as I haven't strengthened the brackets.

Tyres had a lot more meat when fl kit fitted, same effect regardless of those :).

Its not undriveable by any means, far from it, just very very responsive. Not the lazy drive it was prior to the fl kit fitting.
Lawrence Slater

Lawrence

9/16th anti roll bar is standard on 1275s (some earlier cars had no ARB fitted, I understand later 1500s had an upgraded bar as standard (but I don't play with 1500s)

5/8th, 11/16 and 3/4 are all available as upgrades

My personal preference is for 340lb springs and a 5/8 ARB on a road midget with standard rate rear springs, Dampers uprated all round with 30% valves - I have not gone down the Frontline route, but can see the benefit of doing so.

I can't see how you could reduce the negative camber by raising the rear of the top arm - you would need to move the inner pivot point out - raising it or wedging would just as likely move inwards or at least not move it out - slotting would have the desired effect, or using an offset bush in the top trunnion. My inclination would be to leave alone and play with the ARB for now...

Regards

JB
James Bilsland

If I read your post right you haven't yet refitted the ARB. That would make it decidedly twitchy.
Uprating the roll stiffness at the front would be a definite help to sorting this, either through springs, ARB or both. We use 400lb springs and 5/8 bar, doesn't seem at all too harsh. You could do it with just the ARB, say 11/16" if you want the economy approach, but both ARB and springs would be better.

Ride height at the rear can also affect twitchiness, the higher the twitchier as it induces roll steer from movement of the rear axle.

How the FL kit affects this is that negative camber (or less positive if that's the case) increases grip by setting the tyre at a better angle to the road when cornering. Increased grip at the front will make the car twitchy.

Uprating springing makes the car sit flatter but loads up the outside tyre due to weight transfer from inside wheel to outside. As tyre grip is not linear with load, this results in reduced grip all other things being equal. Of course with independant suspension all other things are not equal as with less roll the outside wheel will be sitting squarer to the road, which increases grip.

The result is a mix of thse two opposing tendencies, but in general there is usually net understeer increase as with less weight transfer at the other end (rear axle) there is increased total grip at the rear on top of whatever the net result is at the front.

For that reason, once you get past a certain level of extra front stiffness and the resulting tendency to understeer, negative camber is a very good way of restoring the balance.

If you just put negative camber in without the additional stiffness you usually get the opposite sequence - more grip at the front, twitchyness, rectified by stiffening up the front as above.

As a simple fix, you could always adjust tyre pressures, more air in the rear and less in the front. try 22psi front, 28 psi rear as a starting point. (Note: If tyre pressures get too high then grip reduces. The point at which this happens depends on the tyre aspect ratio, rim width etc, but it is generally above 30psi and with 80 or 82 series tyres well above. Generally braking grip suffers before cornering grip on high aspect tyres so that needs to be considered too.)
Paul Walbran

just to tighten up a bit on what James put about ARB being standard fit on 1275s and I wouldn't have known this until I read it -

if Terry Horler's book is correct, page 116 - the ARB became standard on RHD cars in Aug '73, so very late on in 1275s

(also at same time it gained as standard hazard warning lights and anti-glare mirrors to both doors)

http://www.amazon.co.uk/gp/product/1906133336/ref=pd_lpo_k2_dp_sr_1?pf_rd_p=103612307&pf_rd_s=lpo-top-stripe&pf_rd_t=201&pf_rd_i=1870979451&pf_rd_m=A3P5ROKL5A1OLE&pf_rd_r=1H1MJABS9451AS0YE6BY

I'm not sure how much extra pressure Lawrence's old tyres can take :)
N Atkins

That may be so, I don't have Horler, I have not yet seen a car made after about 1966 (and I've played with a fair few Spridgets) which wasn't fitted with an ARB so it must have been a popular extra fitment (either from delivery or fairly soon after)...

JB
James Bilsland

James you'd know better than me, it was just something I remembered reading

I did qualify and put the source so as to try to learn and get things correct for others reading the thread and myself (also allowing for the many mistakes I add)
N Atkins

Quick post as in a rush, and will write more later.

I made a real pigs ear of my measurements. I have the standard arb fitted, whatever thickness that is?

In the loft I have an 11/16ths arb. That is what ripped out the arb bracket. Only took about 5 miles to do it, and I hadn't got the tracking sorted by then so I have no idea how the drive would have been with the 11/16ths.

Will write more later, but thanks for the very informative replies everybody.
Lawrence Slater

11/16 will rip out the brackets of a perfectly good chassis eventually, so one with a bit of rust there wouldn't stand a chance. Always worth reinforcing that mount if upgrading the ARB, much simpler than trying to repair it later!
Paul Walbran

More time now.

Took a vernier caliper to the arb on the car, and it is definitely the standard 9/16th. No idea where I got the 3/8ths and 5/16ths from (Could be the vino the night before though).

I can't remember why, or from where, I bought the 11/16ths arb. It wasn't fl, as I have their receipt fot the fl shock conversion kit, and there is no mention of the arb. But it was about the same time, so I must have known, or been told before, about the need for a stiffer arb with increased -ve camber, even if I have totally forgotten now. That is either worrying(senility), or just plain stupid(worrying),---- not sure which explanation I prefer there .

Anyway, summing up then -- ,
increasing -ve camber (reducing +ve camber), without stiffening the front end suspension, results in too much oversteer?, -- hence my dislike for the handling.

Even a 1/16th increase (9/16ths to 5/8ths ) to the diameter of the standard arb, is sufficient to correct this.

Have I bought a too stiff arb then, at 11/16ths? From what you say Paul, not if I have standard front springs.

As far as I can remember, when I bought new front springs also over 10 years ago, I bought standard ones. Fairly certain I did, no reason not to.(Can't find the receipt though).

Btw. If anything, the back sits low, due to poor quality rear leaf springs.

Also, I could put back the standard lever arms, just to test how much the camber was taken in the direction of -ve. That would be interesting. It's certainly very visibly -ve when you look down on the wheels. I'll measure it.

I have to strip the near side anyway, to look at the wear in the steel pin of the fl top arm. So I might as well bolt on a standard lever arm shock, and measure the "standard" camber at the same time. Then I can compare the two.

But the first job, is to be to strengthen the arb brackets, and refit the 11/16th bar, and see how that feels I guess.


Lawrence Slater

Lawrence

After modifying to the Frontlinekit I had too much negative camber at one side only. I solved it with an offset drilled centre hole nylatron trunnion bush (Moss TMG309621). After all I had to change the castor as well… It gave a much more stable feeling.

Flip
Flip Brühl 948 frog 59

I've used 11/16 ARB and 330 lb-in springs with FL kit for 15 years or more (fast-road, track-days, competition). It's very solid and easy to control as several on this BBS have experienced. Wouldn't change anything.

A
Anthony Cutler

if the back is too low (as you said), that will affect oversteer /understeer so fix the ride height before you mess with the front geometry.
David Smith

If I do have standard front springs, and I'm pretty sure I do, what's the spring rate?

Lawrence Slater

Found all the information for spring rates on another thread. Norm Kerr posted a link to a pdf with it.

Not only that its listed in the haynes manual. I just got out of the habit of reading that, with the addiction of the keyboard.:) Or to put that another way, I've become too bloody lazy to look it up for meself guvner. :)
Lawrence Slater

hi

271 lb/in was used from '58 ~ '79 for the front spring. The length was increased over the years as the weight increased.


Norm
Norm Kerr

I agree with Anthony, 11/16" should be fine.
Paul Walbran

So its a case of replace my rear springs for decent ones (on list anyway), and strengthen arb brackets, to re-install the 11/16th arb, and that should sort the twitchy front end.

Now why isn't life that easy all the time huh?

Thanks to all for your posts, been very helpful.

I know I shouldn't say this, but, thanks for not telling me about safety issues. Geez, I'm a trouble maker. lol.
Lawrence Slater

no,

you'll need to change your all your tyres too :)

and possibly your bushes,

grease the front, check your tyre pressures, check your U-bolts, check your dampers, check your wheels, . . .
N Atkins

But only after disconnecting the battery first right Nigel? lol.
Lawrence Slater

in all seriousness, one part of the system effects the others, even the bodyshell, so it's about each component and set up complimenting the other in the type of suspension/steering system(s) set you want

I'd imagined your battery being welded strappings and connections wioth silver fag paper for fuses - Capstain Full Strength of course :)
N Atkins

Dont have battery straps, got shot as they were a pain in the rear. bat just does it's thing on the tray, and has never bothered me at all.:) You knew it didn't you.:)

I do have proper fuses though. Siver fag paper wont "fuse" until it's too late. Mind you with 35A fuses, might as well be silver foil. lol.
Lawrence Slater

Lawrence

Ironically saggy rear springs may well be making the car less twitchy. Two reasons:

If they are saggy because they are softer (lower rate) than they should be, that helps the front/rear balance by letting the outside front wheel take more of the roll resistance - same effect as stiffening the front.

Also, the position of the axle relative to the spring eye is more favourable with respect to rear axle steer. The lower the axle is compared with the spring eye, the more it has a tendency to cant the axle in a way that steers the back outwards in a corner when the body rolls (axle drops down and forward on the inside, up and backwards on the outside).

As the axle (at rest) gets higher compared to the spring mount (ie saggy springs), this effect reduces, disappears and then reverses. Hence less twitchyness as the back end steers into the corner rather than trying to hang the tail out.

Maybe you should leave the back where it is and get a set of lowered front springs! Then your only problem might be the one we have in CJV, which has been (intentionally) lowered - that extra couple of inches makes it a challenge for creaky joints like mine to crawl out and get vertical :-)
Paul Walbran

Thanks Paul. I think. :) lol. Boy, that's technical stuff alright.

How did the boffins at BMC, ever come up with a compromise good enough to satisfy all the opposing forces in spridget suspension?

Or didn't they, and is that why after all these years, all these modifications are tried?

And all I wanted was a decent pair of front shocks. I should have stuck to the lever arms, and the regular chore of changing them when they were knackered. lol.
Lawrence Slater

Lawrence,
your attic ARB may be off a 1500? I cannot remember sizes but I do know that when I upgraded my 1500 one with a thicker aftermarket replacement, I "cascaded" the 1500 ARB to my 1275 and it suited it very well. 'though both cars benefited from some extra welding to reinforce the ARB mounting points. I have lowered front suspension using spacers, and standard rated springs.

Rear is not intentionally lowered as such but does sit lower than standard on very compliant "Clive Berry" springs. I also have cheapo e-bay tube shocks on the rear (ex mini fronts). I like the way it handles. But the clue is never drive another person's car; that way you can always convince yourself that yours has the ideal set-up and just have fun coping with however it behaves!

Guy
Guy

Yes, I really cant remember why I ended up with the 11/16 arb, and not the intermediate upgrade. But as it's the one I have, after I add some strength to the mounts, I guess I'll fit it.

"you can always convince yourself that yours has the ideal set-up and just have fun coping with however it behaves"

ha ha. Yup I've been doing that for years, and your right, it works for me too. :)

Lawrence Slater

Lawrence,
I am probably going over old ground, but if your car is twitchy have you checked toe-in? Mine works best with about 1 degree toe in; less than that and I have to continually steer the car. And as the TRE connection is above the level of the stub axle, increasing the neg camber, lowering the suspension or a combination of both will increase the toe-out which will then need resetting.
Guy

Hi Guy, yes I did track it quite a bit. To the point that I almost set fire to the bloody thing; I got so sick of trying to fine tune it lol.

What I settled on, was either wear out the tyres prematurely, or compromise and live with the twitch.

But it annoys me, since I can't let my mind drift when I am constantly having to watch where the car is taking me. hah hah.

So I have even wear and a bit of twitch. Which judging by all the prvious comments seems to be down to adding more neg camber without increasing the stiffness in the front suspension.

But I take your point, and when I make the changes to the front, and or back, I will indeed double check the tracking again.

Now why didn't god in his/her infinite wisdom, when creating the world, also lay down an 11th commandment?

Thou shall not make a midget twitch.
Lawrence Slater

Must be the tyres you are using. How old are they?
Guy

Tyres are as old as the fl kit I fitted but were perfect back then. Even wear before and ever since and not twitchy until I fitted the fl kit, so not tyres I reckon.

But then again I don't know how sensitive the FL kit, or neg camber is to the type of tyre fitted. If it has to be fitted with a particular tyre in mind, then I will definitely dump it, and convert to double lever arm shocks.

But the tyres are due for a change anyway, as they are getting near the mark, and I have some original steel wheels to fit too, --- at some point when I get around to all this stuff.

Probably at the end of the summer though, ss I want to drive in what's left of it. lol

Also perhaps(probably) take the sprite down to Barcelona and up through Paris and Munich, for a bit of visiting friends.
Lawrence Slater

Guy,
that made me laugh - Lawrence is a bit sensitive about his 10 year old tyres and doesn’t like me mentioning their age – so I don’t :)

hurray, got my name changed
Nigel At

Nigel you could have used deed poll for that.:)

And what do you mean I'm sensitive about my tyres?

Rubbish.
Complete rubbish.

The fact that as soon as I read that Guy had mentioned my tyres, I immediately killed the cat, pulled the wings of 3 butterflies, and smashed every plate in my house in a blind and uncontrolled fury, had nothing whatsoever to do with my tyres.

I just felt that way this morning :):)

And anyway, they are closer to 20 years old than 10. So there, Ner ner ner.
Lawrence Slater

blow, I thought they were about 20 years old but couldn't remember for sure

I expect Guy will be thinking about the same as me about the age of your tyres, be interesting to see if he 'says' anything about them :)

for some reason I thought I couldn't change my posting name on here and kept forgetting it only (previously) showed my initial and not my first name
Nigel At

Does anyone know if you can simply swap the bronze bushing in the Peter May offset trunnion with the stock rubber/steel bushing? Just curious if you wanted the neg. camber but a little more compliance for street driving. Just eyeballing it, looks like the bronze bush may be smaller OD than the stock rubber one.
Jack Orkin

Can i throw a spanner in the works and ask which side of the car you are referring to?

No midget was built equal on each side and there "are no books" which explain how to make both sides the same.

PeterJMoore

Peter, is that question for me or for Jack in Georgia?

I was talking generally about the car being front end twitchy, I hadn't considered that it might be a one sided issue.

Lawrence Slater

This thread was discussed between 26/07/2011 and 31/07/2011

MG Midget and Sprite Technical index

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