Adjustable Tie Rods for a Roadster

[lil_red_roadster]

Finally managed to finish my adjustable tie rods at the weekend...just need to finally fit and setup once my new caster gauge arrives.

For such a simple project this has been festering for ages for want of the ability to cut an external thread without the die wandering all over the place. I know others have achieved a similar setup through alternate means but my key objectives were to use readily available components, avoid scrapping anything Marina-specific, make the conversion readily reversible and avoid the need to weld anything.

A machine shop could have done it but none of the locals appeared very interested...so with vague thoughts about buying a lathe I went for the option of using a tailstock dieholder in my pillar drill to get the thread started...after that it was a breeze. There's nothing like the smell of warm cutting oil in the morning..!

To save cutting up the Marina tie bars I acquired a pair of scrap Minor ones for a fiver...the only bit you need is the end that goes in the fork on the lower arm (identical to Marina) and the diameter is 1/2", again the same as the Marina.
McGill Motorsports supplied a pair of 200mm turnbuckles, LH rod ends and spacers and www.thelatheman.com knocked me out a couple of top-hat bushes for a tenner (this is so I don't have to use a massive 3/4" bolt through the tie-rod chassis mount). The brackets were cut from some ERW box-section and whilst they are a little bigger than I wanted it was the only section I could find (easily & cheaply) which allowed me to avoid incorporating any of the weld-strip in the bracket itself.

Pics below.

AdjustableTieRod.jpg

AdjustableTieRod_2.jpg

[greyV8pete]

Re: Adjustable Tie Rods for a Roadster

In which part of the country is the latheman based? Looks like a really useful service. Btw the above link doesn't work but ending .com does. Peter.

[lil_red_roadster]

Re: Adjustable Tie Rods for a Roadster

Apologies have updated original post/link.
He's based in Lancashire...I found him on the web & sent him a drawing. Quote was acceptable & parts arrived in a few days...very happy..!

[stevejgreen]

Re: Adjustable Tie Rods for a Roadster

That's a neat looking job I like it.
I have looked at various options on this but never done the conversion, but had many thoughts. Not wanting to denigrate Jez's work, here they are.

One thing I considered was to totally abandon the almost infinite adjustable turnbuckle left and right hand threads, and to either weld the OEM tiebar into a sleeve threaded to suit a rose joint. Welding may not be so good on a component of unknown material (is it HT steel) but reducing its effective diameter by threading would similarly weaken the part? Or if the Minor Tie rod is of suitable length simply thread it to suit the Rod end bearing.

On the face of it without turnbuckles you would lose some adjustment as it could only be set at 1/2 the thread pitch intervals.
But doing the trigonometry for an M12 1.25 Fine or 1/2"-20 UNF thread (remarkably close in pitch) that would result into about 0.1 Deg steps more than accurate enough for a standard Marina suspension that relies on the stiffness and condition of the tie bar bushes for final location.

Something that ought to be checked before starting out measuring closely, is the condition of the mini upper wishbone as discussed in Pitstop Dec/Jan 2010 and here or there. This not only cured a mystery rattle but with careful machining set the upper wish bone by 1.3mm offset. Quite possibly this could be made adjustable to some extent by shimming to compensate for the larger steps on the tie rod?

One important tip would be to slacken all the fixings between the bottom halves of the Marina wishbone to relieve excessive stress on the trunnion or bottom swivel Eye bolt.

PS. TheLatheMan is in Bolton Le Sands, Carnforth.

[dbazdavies]

Re: Adjustable Tie Rods for a Roadster

Are you able to supply future sets ??

[cameronfurnival]

Re: Adjustable Tie Rods for a Roadster

neat job Jez

[Cornish Wrestler]

Re: Adjustable Tie Rods for a Roadster

neat job Jez

Looks like a neat job very much like the arms that I've made .it has certainly made my steering very precise .I think you'll be pleased when you drive .what castor are you aiming for?

[lil_red_roadster]

Re: Adjustable Tie Rods for a Roadster

Are you able to supply future sets ??

Sorry, I'm not planning on producing these to order but happy to provide a more detailed description for a future edition of Pitstop.

[lil_red_roadster]

Re: Adjustable Tie Rods for a Roadster

Looks like a neat job very much like the arms that I've made .it has certainly made my steering very precise .I think you'll be pleased when you drive .what castor are you aiming for?

Somewhere around 4.5 degrees...the Marina was 5 (originally 2 on v.early cars) with mildly positive camber...as the Roadster has slight negative camber (which I'm sure is not quite symmetrical - to be checked) around 4.5 seems like a reasonable place to start.

[b_caswell]

Re: Adjustable Tie Rods for a Roadster

These are for a mini not sure if they could be adapted but boy they are a bit
pricey.http://www.kentautodevelopments.com/...table-tie-rods

[stevejgreen]

Re: Adjustable Tie Rods for a Roadster

Somewhere around 4.5 degrees...the Marina was 5 (originally 2 on v.early cars) with mildly positive camber...as the Roadster has slight negative camber (which I'm sure is not quite symmetrical - to be checked) around 4.5 seems like a reasonable place to start.

I believe that all Marina based Roadster Chassis were designed with a 2.5 Deg Castor angle as standard. (Taken from the Marlin Build Manual)
Assuming consistency of chassis from car to car as there are allegations that the jig was not reliable.

I am not sure where this figure came from as the majority of Marina Saloons through to Itals had a 2.0 Deg Castor angle, Estates and commercials varied. (Taken from several BL workshop manuals from 76 to 81)
It was the very early cars that had 5.0 Deg Castor.

Workshop manual.jpg

[lil_red_roadster]

Re: Adjustable Tie Rods for a Roadster

Thanks for correcting Steve - I misread my Haynes manual.
I always found self-centering at 2.5 degrees none-existent and increased caster to improve this by swapping the thrust washers to give around 5 degrees.
It will be interesting to be able to measure/adjust more accurately to arrive at the optimum settings.

[stevejgreen]

Re: Adjustable Tie Rods for a Roadster

It's a shame there is not a little more detail in this Doc, but it highlights some changes that BL made to Marina steering here or there It might help those with early donor Roadsters, as all trunnions are effectively interchangeable, provided you know what you are trying to achieve.

[martinclan56]

Just bumping this thread as, now the above mentioned tie rods have been fitted for several years (2016?), I wondered has it been a successful conversion?
I am probably going to do the same myself but am a little concerned about the use of rose joints instead of rubber bushes making the suspension / steering rather harsh?

Cheers, Robin

[lil_red_roadster]

TBH there isn't that much difference in feel.

Currently running 5 degree castor, which is the limit without cutting additional thread (more needed on one side to account for the dodgy bottom bracket mounts that cause the unequal camber); self-cantering is slightly better (but still in the crap zone) though tracking & front-end stability does feel more assured on the twisty stuff. That said, having had the standard bushed setup pull the tie-rod and securing bolt clean through the cup-washer I can say it feels more secure!!

I've lost interest over the last couple of years - hardly get time to drive it and even less time/inclination to fettle it...it needs a shim under the bottom bracket and possibly some fiddling with upper-arm thrust washers to set it up properly. Jobs that are currently filed under the "can't be arsed" category