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Haynes Roadster Rear Toe Adjustment
Joshy - 14/2/19 at 10:02 PM

Hi all,

I've had my Roadster on the road for a couple of years now, and I know for sure that my rear toe is out. There are some unusual wear patterns on the rears, and going over potholes with the left rear makes the car 'lurch' a little...

I'm running a sierra spec. chassis and (until now) by-the-book wishbones. Currently the car is up on axle stands and I'm half way through re-designing the rear suspension. I've gone with poly-bushes on the inboard pivots and rod-ends on the upright - please, everyone critique my design!

I particular, I have the following questions (in no particular order):

- My design is using the existing rear upper wishbones. I'm intending to plug weld a threaded adaptor in, such that a rod-end can be accepted. Is this a good idea, or should I make new upper wishbones from scratch?

- How much theoretical +/- toe angle should I be aiming for?

- I'm intending to use M12 x 1.25 rod ends. How much minimum thread engagement is required? 1.5D? Can I use thin lock-nuts to increase thread engagement depth?

- I originally designed the 'floating arm' with both rod-end axes in-line, with a view to using a RH/LH threaded pair to facilitate on-the-fly adjustment, and continuous adjustment (as opposed to discrete adjustments of half a thread-pitch). Unfortunately I found that this meant the outboard rod-end was already over its maximum angular deflection in the nominal position. The only way I can see to solve this is by bringing the inboard rod-end mount-plates further up the core wishbone. Is this a good idea, or will the design be significantly weakened?

- What type of rod-ends should I use? Bronze / PTFE / Nylon lined?

- Where can I buy poly-bushes and pivot bush inserts for the inboard pivots these days?

- Is the tie-tube between the inboard pivots required?

- Any recommendations for a good bespoke wishbone fab-shop?







Any help is greatly appreciated!

Cheers,
Josh


AdamR20 - 15/2/19 at 06:55 AM

All looks really good to me. Plug welding in adaptors will work great. You only need about 1 deg of adjustment, but make room for more given manufacture tolerances. 1D contact will be plenty. Spend no less than 20 on each rod end. Tie tube not needed.

No need for the 'floating arm' system any more though, take a look at a rear lower Westfield wishbone and just copy that

https://goo.gl/images/cW77Fj

[Edited on 15/2/19 by AdamR20]


wylliezx9r - 15/2/19 at 07:43 AM

That's pretty much exactly the design I had on my old car and it never gave me any problems.


jps - 15/2/19 at 08:54 AM

quote:
Originally posted by AdamR20
No need for the 'floating arm' system any morehttp://www.locostbuilders.co.uk/post.php?action=reply&fid=3&tid=214292&repquote=1787577 though, take a look at a rear lower Westfield wishbone and just copy that

https://goo.gl/images/cW77Fj

[Edited on 15/2/19 by AdamR20]


So the Westfield one has a standard 'solid' bush on one side at the bottom - and a single rose joint on the other side? Surprised it doesn't need to be adjustable at both sides?


AdamR20 - 15/2/19 at 09:39 AM

Exactly that.

Why would it? There's enough flex in a metalastic bush to give all the adjustment (about a degree) you need.


Doctor Derek Doctors - 15/2/19 at 10:54 AM

Why have a double ended floating toe link if it has a dog leg and can't be rotated to adjust toe? You might as well just have a welded on leg.

Also that toe link will naturally rotate round under the offset weight due to the dog leg and the seal will just wear away against the bolt.

What angle will that out rear rod end have on it with a straight toe link? It doesn't look too much for a normal rod end, certainly no more than I have used in the past. Or you could just use a high misalignment rod end.

I had pretty much that set-up on my old sprint Car and it worked fine:

Description
Description


jps - 15/2/19 at 11:54 AM

quote:
Originally posted by AdamR20
Exactly that.

Why would it? There's enough flex in a metalastic bush to give all the adjustment (about a degree) you need.


Ah - good point. I was thinking about the poly-bushes I have on mine which, although I appreciate they have a shore rating which I understand shows some pliability, seem pretty solid to me!!


rusty nuts - 15/2/19 at 06:36 PM

I had rear toe out on my Luego using Sierra parts which I was able to adjust out using shims between the bearing carrier and the rear upright , took all of half an hour each side and cost pennies


tilly819 - 15/2/19 at 08:11 PM

quote:
Originally posted by rusty nuts
I had rear toe out on my Luego using Sierra parts which I was able to adjust out using shims between the bearing carrier and the rear upright , took all of half an hour each side and cost pennies


I did exactly the same on my Haynes.


fregis - 15/2/19 at 11:07 PM

quote:
Originally posted by rusty nuts
I had rear toe out on my Luego using Sierra parts which I was able to adjust out using shims between the bearing carrier and the rear upright , took all of half an hour each side and cost pennies


did the same
if i remember good, 0.2mm shim changes 0.10 deg


40inches - 16/2/19 at 10:20 AM

quote:
Originally posted by rusty nuts
I had rear toe out on my Luego using Sierra parts which I was able to adjust out using shims between the bearing carrier and the rear upright , took all of half an hour each side and cost pennies


By shims do you mean specially made ones or washers? I used washers on the 2B but the MK is just within limits, so no need.


rusty nuts - 16/2/19 at 01:41 PM

quote:
Originally posted by 40inches
quote:
Originally posted by rusty nuts
I had rear toe out on my Luego using Sierra parts which I was able to adjust out using shims between the bearing carrier and the rear upright , took all of half an hour each side and cost pennies


By shims do you mean specially made ones or washers? I used washers on the 2B but the MK is just within limits, so no need. [/quote


I used some shim stock that I had cut to shape with a sharp pair of scissors. They are fitted to the rear section of the bearing housing between the bearing carrier and the upright. It is or was possible to buy ready made shims but me being a tight as made my own. The car lost the vague feeling on the rear after fitting the shims .


jps - 16/2/19 at 04:56 PM

quote:
Originally posted by rusty nuts
I used some shim stock that I had cut to shape with a sharp pair of scissors.


I remember one of the guys on the Haynes forum said he did this with an unrolled beer can (or two!)


Joshy - 3/3/19 at 10:07 AM

Thanks for the advice everyone. Whilst the 'locost' shim solution is appealing, I've decided to press on with my rose-jointed design. This will allow me to adjust the toe-angle continuously, and on-the-fly (e.g. in-between trackday sessions). I also have ambitions to design and build a single seater hillclimb car in the near future, so it's been good practice!

I've used M16 RHT rod-ends on the lower upright pivots with reducer/misalignment spacers. M14 LHT rod-ends on the upper upright and inboard floating link.

I'm planning on machining all the threaded inserts myself, but I'd prefer to out-source the fabrication/welding. Can anyone recommend any good fabricators (even better if they're midlands-based)? Also, what grade of steel should I specify for the inserts/tubes?









[Edited on 3/3/19 by Joshy]


Camber Dave - 3/3/19 at 10:39 AM

Your choice of M16 & M14 rod ends with 2mm pitch may give you a problem setting toe accurately.
The course pitch on the double ended link will be extremely difficult to set. ie 1 flat will be about 7/10 of a mm and the backlash in the link will be enough to upset your setting as you tighten the 1/2 nuts.

Westfields and others have used 1/2" UNF (and a single end) for years.
M12 * 1.25mm would also be both strong enough and easy to adjust. I flat of the turnbuckle will be 0.4mm


Joshy - 16/5/19 at 09:15 AM

I've been trying to find a fabricator who will weld these arms up for me...

Can anyone recommend a decent fabricator? I have fully detailed engineering drawings ready to go, and keen to get these made sooner rather than later so I can enjoy the summer!!

Cheers,
Josh


40inches - 16/5/19 at 10:26 AM

Contact Callan (Doctor Derek Doctors) on here. I would think that he could help.


Charlie C - 16/5/19 at 10:52 AM

You can also contact Callan here http://www.t89.co.uk/contact/


907 - 16/5/19 at 02:52 PM

quote:
Originally posted by Camber Dave
Your choice of M16 & M14 rod ends with 2mm pitch may give you a problem setting toe accurately.
The course pitch on the double ended link will be extremely difficult to set. ie 1 flat will be about 7/10 of a mm and the backlash in the link will be enough to upset your setting as you tighten the 1/2 nuts.

Westfields and others have used 1/2" UNF (and a single end) for years.
M12 * 1.25mm would also be both strong enough and easy to adjust. I flat of the turnbuckle will be 0.4mm





Agree totally with Camber Dave.

Stay away from course pitch threads.




My first rod ends went to landfill. Designing your own is knowing when you have made a mistake.