TC model Radius arms.... anyone got a drawing ?

[EuropaTC]

A bit of an oddball request here, but does anyone have a dimensional drawing of the radius/trailing arms for the TC Europa ?  I know the S2 manual gives dimensions but my TC manual doesn't have the same detail and I'm assuming as the chassis fork angles are different between S2 & TC, the radius arms are likewise different.

The reason for the request is that I've just done the alignment again with a slightly better set-up and I'm not happy with all the shims I'm using.  So although the arms look straight with no damage, the driveshafts, bearings & lower links all tight and camber ok,  I'm beginning to suspect the angles of the hub carrier plates at the end of one arm are bent.  The only way I can think to settle it is from a dimensional drawing, so does anyone have one ?

Brian

[buzzer]

Brian,

I would have thought that if the radius arm hub carriers are bent you would see witness marks elsewhere and/or you would not be able to fit the hub into the arm. Could you not template from one side to the other to check the angle as unlikely both are deformed in the same way.

Dave

[EuropaTC]

Hi Dave,

Thanks for your comments, it's all appreciated.

I'm not so sure that I would see visible signs of bending or at least not unless I was specifically looking for it, and I'll admit when I put it all together, I wasn't.    The "straight" sections on both sides are what I'd call perfect, hence my concern that if any damage exists it's at the final segment where the carrier bolts into those two flanges.  I can imagine them being bent by 4 or 5 degrees and me not seeing it, hence the idea of some measurements to check against.

We think alike on the template thing, I now have a roll of lining paper in the workshop to cut up and take a rubbing imprint from underneath tomorrow.  That was my plan to get some rough measurements to check against any details that come forwards,   but comparing both sides sounds like a good idea and I'd not thought of that aspect. (another dohh moment      )

I almost wish I hadn't started this 4 wheel alignment kick and just stuck with the idea that tyres should wear out quickly on this car.....

Brian

[jbcollier]

Get it sorted.  It will transform the car's feel at high speed and at the limit.

Do you have too much toe in?

To which side of the frame are the arm's mounts attached?  Inside?  Outside?

[EuropaTC]

Hi again,

Easy questions first - the radius arm mounts are "rubber inside" and yes, my concern is/was about excessive rear toe-in.

When I used the car daily I never felt it to be unstable at motorway speeds and even after putting stiffer springs all round last year I didn't consider it wildly unstable. But now, with the benefit of 20/20 hindsight  I think the way it used to knock out rear tyres, UJs and wheel bearings were probably a symptom of excessive rear toe & camber. (the first owner got 20k out of rear UJs/bearings from new but I've never made that mileage without something showing some play)

On a recent thread I was puzzling over DIY alignment and since then I've become more confident in the process and able to produce repeatable results.  The end point is that I'm happy the car is set up properly and the new suspension, new bushes, etc all working as they should.  In fact I'm quietly pleased with it all, the only niggle is the amount of spacers I've used and how they are distributed.  I am now at 8mm & 15.2mm to get 2mm & 2.5mm toe in respectively and that just seems wrong.

Hence the thought that I might just have something bent or even fabricated incorrectly and the hope that maybe someone has a drawing hidden away with measurements I can cross-check.  It's a slim hope I know,  but if you don't ask......

Brian

[Grumblebuns]

I'm wondering if there is a dimensional difference between the trailing arms for the S2, TC and TCS. Is the only physical difference the cut outs and drillings on the carrier for the different hubs between the three types so they are not interchangeable?

The TCS supplement in the workshop manual doesn't make the distinction between the two. The people who would probably know are the Lotus vendors, Richard Winters and Ray at RDEnt.   

[jbcollier]

If you fit the mounts so they attach to the outside of the frame,  that will reduce the number of spacers required.  That's how I fit mine and I needed no spacers at all.

[EuropaTC]

Could you not template from one side to the other to check the angle as unlikely both are deformed in the same way.

   Gold star award there Dave !
 
I eventually managed to get a half decent impression from both arms yesterday.  They aren't good enough for anything other than basic comparisons but cutting them out & lying one over the other they do show a different angle at the junction of the hub carrier flanges & the radius arm box section.  I tried to measure with a protractor but it wasn't good enough, so I went the other way and did the maths on what sort of angle to expect based on the shim differences between sides.  It's surprisingly small and I personally would never see it when assembling things. No idea why it's different as I've never kerbed or hit the side, it might always have been that way all the time I've owned it ?

So - there's still no definitive answer but at least I can see where the issue lies and I've more faith in what I've done so far.  I count that as progress !

Joji - the S2, TC & TCS all have different part numbers for the radius arms. It could be just the bolt spacing, I don't know.   I'd prefer detail measurements because the lower links & intermediate driveshafts also have different numbers and that's setting the other part of the suspension triangle.  I don't think we can assume anything with Lotus.....

John, The mounts are fitted with the metal flange outside, the bulk of the rubber pointing inwards. I'm using Esprit style shims fitted between the mount flange & chassis rather than washers on the radius arm bolt.  Washers are easier, it just looks a bodge with so many.  I'm envious you can get away without shims, that's how cars should be built !

[buzzer]

Brian,

Excellent, well sort of.. at least you know what the issue is. But why they are different? Could be down to 1972 quality control! or lack of....


Dave

[EuropaTC]

I have no idea Dave and I'd have thought that any impact sufficient to bend it once assembled to the carrier would cause visible/notable damage to the alloy wheel, lower link, driveshaft or even gearbox. It might even wake up the driver.......   

I have 2 possibilities, one is I damaged it when I had the chassis out for repair because they spent a year or more kicking around loose in the garage, so very possible.  Second is that it's 1970s workmanship and it's always been like that....    I have no idea, I have never checked the rear toe in all the years I've owned it - "it has shims fitted so it must be right" - that's the optimism of youth for you   

However one lesson I have learned is that I must set rear toe against the chassis centreline.    I do the front with two bits of angle which are held against the wheel rim and you just measure the difference across the car at the front & rear of the sections.  It's very simple, you just wind both TRE's equally and it's not a problem at the front because the steering wheel sorts any minor differences out. But at the rear if I'd done that and split the shims equally I would have had toe in on one wheel & possibly toe out on the other.  I'm sure that would have been "interesting".

[BDA]

Those radius arms are very stout, especially when fitted to the rear upright. I would think that almost any damage could be detected by using a straight edge. As for manufacturing irregularities... maybe you could measure from the forward mounting point to a bolt to the upright and compare both sides.

You're right, of course, that the rear must be aligned with respect to the center line of the car - otherwise your car will crab down the road. There are simple methods for doing that - though when I first built my car, I gave it to a shop to do the rear toe. I think after that, I can use my Dunlop alignment rig to make the same change to both sides and be close enough. I would guess that whatever damage (as long as it doesn't weaken the structure) or manufacturing irregularities you might have, that a proper alignment would make up for them.