Bent ARBs fitted by design

[Pete Lewis]

Of there was a designed set in the position of the ends to aid road camber , driver weight then LHD would need an opposite which is not shown there is only one 5/8 part number that  i can find ??

Pete

[Pete Lewis]

Theres an unsed original on the show chassis in HQ.

Pete

[Casper]

Quote

 I really don't think I have ever seen a "flat" thin ARB. They are always bent, and in the same way. That surely cannot be coincidence?

I recall a similar discussion on another site and John Kipping contributed :    "They are all like that". 

Good enough for me.

C.

[JohnD]

They could all be like that after use, desn't mean they were fitted like that.

[Colin Lindsay]

12 hours ago, clive said:

And Marcus, that is exactly the point. I really don't think I have ever seen a "flat" thin ARB. They are always bent, and in the same way. That surely cannot be coincidence?

But are the ones you have seen new, or off a car where they have been bent by years of use? I have completely flat ones in my garage roofspace, and have seen NOS versions at shows that are also flat, so they can't all have been manufactured incorrectly.

If they're meant to be bent, then which side goes to which? High side left, or high side right? Or maybe it's bent downwards rather than up?

[Ian Foster]

I have two 11/16” ARBs. One is the original from my 1969 GT6 Mk2 the other is off another rotoflex GT6.

When laid on a flat surface, one has set of about 10mm, the other 15mm. The o/s is higher in both cases. There are few minor inaccuracies in the bends on one side of the bar, but this is a feature of both so I am assuming this is related to the original manufacture.

The 7/8” bar (off a late Spitfire I think) that I currently use is almost flat.

I changed to a 7/8” bar years ago to try and address excessive rear roll, but I have since stiffened my rear spring by the addition of another central leaf and the rear end is much better as a result, so I’m considering reverting back to the original 11/16” bar to reduce understeer. I drove Nick’s Vitesse EFi which runs a standard bar and noted good turn in, with similar front springs.

I have tried to cold straighten my original bar by clamping to a bench and bending with tube without success. It does twist a long way but does not retain it and having tried this I cannot believe that a bar can acquire a set ‘in service’. I assume it is a special spring steel bar, so can it be heated and bent without affecting the steel, or if it is heated does it need to be quenched/not quenched?

The other alternative unless I can be convinced that the set is a good thing, might be to have adjustable links, which could be done with rod ends (expensive) or cutting, threading and joining the linking rod on the original links with a sleevenut and locknuts. I have some recent NOS links that are in good condition.

This link allows comparison of different bar diameters https://balancemotorsport.co.uk/suspension/anti-roll-bars#cal

PS Similar thread running on Sideways forum.

Ian F

[Clive]

36 minutes ago, Ian Foster said:

 

The other alternative unless I can be convinced that the set is a good thing, might be to have adjustable links, which could be done with rod ends (expensive) or cutting, threading and joining the linking rod on the original links with a sleevenut and locknuts. I have some recent NOS links that are in good condition.

 

I am wondering about using the OE bush that is fitted via a stud to the ARB, cutting the funny rubber ball bit off the other end, and cutting a thread on the remaining rod. Then use a rod end etc to fit to the wishbone. OK, no turnbuckle so a tad faffy to adjust, but a cheap way forward? And retains the rubber bush so hopefully no increase in noise.

I am struggling with my rear on my rotoflex spitfire. Found an oddball spring that I am going to try, rotoflex GT6 version from leaf number and Wrapped end brackets, but more arch than std by a large margin. Not easy as so little info about modified rear springs.

[JohnD]

Yes, I started the thread on Sideways as this seems a general question for Triumph owners, that needed general discussion.

It seems to me that interpreting parts deformed after 50 years in use as being originally deformed is unwise.     

Ian, you tried to stress your bar to the point when the strain caused it to yield and change its shape, like an overtightened bolt.   What I suspect has caused the deformed bars today is creep, which is a form of yield that occurs over time under less than yield-level stress.     It may indicate that the material or production of the bars was not satisfactory, but we can't sue Triumph now.

John

PS for some time, Jon Wolf has offered spherical jointed drop links.  http://www.wolfitt.com/wolfitt_products_1.htm#Anti roll bar drop links - rod end conversion  Very easy to make the links linger by using a longer threaded tube.

[Pete Lewis]

we used to call it torsional  memory,  came across this with truck half shaft testing which  wanged  the shafts through a determined angle back and forth  for days and weeks till it failed the eventual split and fracture was sectioned and microscopically examined for its characteristics

the  heat treatment got modified to suit the results all our shafts had a  shear point near the splined end to protect the diff from snap overloads .

pete

 

 

 

 

[dave.vitesse]

I have been racking my memory re things relating to the Swing Axle from way back then. The original, pre-production, set-up had a much stronger rear spring and had less camber change. The production people said the ride was too hard so, yes you guess it, fitted a softer rear spring. As a result to reduce problems caused by the softer rear spring the location of the rear tie-bar was said to have been changed, before production, and ARB was designed to have some give. Not to sure what the changes to the ARB may have been in 1959, but they may have related to the Swing Axle. Post production I believe the tyre pressure was also change possibly around 1960 to reduce the effects of the Swing Axle.

If you have a standard suspension set-up then the best bet is to use an original ARB if you can.

Dave

[68vitesse]

And this from Canley Classics website suggesting larger bar is not used on unmodified cars.

https://www.canleyclassics.com/suspension-steering-and-brakes/swing-spring-conversion-kits

Regards

Paul

[Pete Lewis]

Strange as they offer it on 13/60 parts listing ,  but not 1200   both cars have the same suspension

This is all of little cause if you need one only the 7/8 is available in the aftermarket 

So you can only replace with stiffer flat one 

Less roll may give  More or Less  toe in on turns , and  is generally changed by playing with tyre pressure's first.

Think triumph suspension gives paarallel up to 20deg turn in , not something ackerman devised but its common to have parallel 

On most cars from the  60s to the present day,

 

Pete

[dave.vitesse]

It all about where the forces go if you prevent the roll on the front. I guess this is why it's importance to get the balance correct between the front and the rear suspension. What Standard Triumph found is that if the front was too stiff then the Swing Axle would jack up more.

Yes Paul that is why Canley Classics don't recommend the stiffer ARB on a standard car. 

I agree Pete, if you can only get the stiffer type it's pain. An Estate rear spring may help? There was also the Van rear spring which was even stiffer. Many used to fit latter.

Dave

[Clive]

As my previosu comments about my herald estate. It had 440lb front springs (along with a courier rear spring), and these would have had a far greater effect than any ARB. To the extent the ARB was no longer required, it just caused understeer. 

Seems many people (not Dave, Pete etc) think putting a bigger ARB or playing with springs/shocks is simple. It really isn't. And very easy to make things work worse than the factory/standard setup.

[Pete Lewis]

flatter cornering forces would looking at the geometry give less toe in on turns so roundaouts etc become a flatter feeling so the sensation via the backside is very different 

force , to greater body roll .

you cant compare pocket sprung with a water bed , both are flat but you cant get out umless you mimic a beached whale 

ha  

Pete

[dave.vitesse]

The problem was a soft sprung Swing Axle rear suspension. Not the best of things in the first place and Standard Triumph made changes to reduces it's unwanted effects whilst still trying maintain the softer ride.

Forces when you corner will be transferred from the front to the rear as you travel around the bend, the stiffer the front then the more force will be transferred to the rear.

I also remember there was something concerning the roll angle, as this was greater on the smaller/original ARB it helped reduced the tuck under. 

Clive's right in my book, if you harden up one end of the suspension then you have to do the same at the other.

Dave

[Pete Lewis]

Its looking like good time to invest in a chassis/ handling dynamometer rig.  

I think our old one is still lying dormant in the test cells which still remain abandoned  at the back of the dunstable dealership,

anyone got a balaclaver and torch, 

pete

 

[dave.vitesse]

10 minutes ago, Pete Lewis said:

Its looking like good time to invest in a chassis/ handling dynamometer rig.  

I think our old one is still lying dormant in the test cells which still remain abandoned  at the back of the dunstable dealership,

anyone got a balaclaver and torch, 

pete

 

Anybody got a Mk2 Jag as a getaway car?

Sounds like a good plan Pete.

Dave

[JohnD]

The BMIHT have been delving away in their archive, in search of this Service Bulletin from 1959.    But they feeel that it would be better for one who is familiar with the objective of the search to pursue it further, and invite me, or "a colleague" to visit them by appointment and search in the relevant six boxes.      I'm a bit tied at present, and will do so when I can.   If anyone else fells that the Spirit moves them, they are welcome to take up the search for this Unholy Grail.

Ms.Charlotte Gallant is the archivist I have been corresponding with, the BMIHT address is history@britishmotormuseum.co.uk and the archive boxes in question are BL-STA-13 to 18.  She asks for a weeks notice to book the Reading Room.

John

PS  I've joked about the University of Sideways, it's Faculties and academics.     Maybe we should invite Ms.Gallant to accept the post of Librarian?     Ook!

[Pete Lewis]

Richard has just sold his Alpine and  got the Daimler version      shall we  sign him up ???

 

[Pete Lewis]

And another way,

Club HQ has copies of service bulletins , ive ask Bern if theres a chance to look but any member can call in and have a browse

Pete

[Ian Foster]

Thread resurrection alert !!!

I have removed the previously fitted 7/8" ARB from my Mk2 GT6 and refitted the original 11/16" bar (albeit with its slight set).

The effect is 100% positive. Much better steering at even low speeds and improved turn in as Nick commented above.

This is in conjunction with a slightly beefed up original rear spring (1 new leaf added) and my weak rear end was the reason I swopped ARBs in the first place (see post above) .

So once again Triumph know best!

Ian F