Front Strut Top Mount Rotation

[RSi]

This information was passed to me by someone. It's regarding fitting the strut top mounts on the front of the car, not the rear. Can anyone confirm this, or is it wrong?

"The top mount is roughly triangular, with upward-pointing studs at the corners - see the part labelled 157333 & 142777 in the general arrangement drawing here:

https://rimmerbros.com/Item--i-GRID008480

The mount appears rotationally symmetrical but isn't. One of those studs is a fraction FURTHER from the centre hole than the other two.

To be installed correctly, the FURTHEST stud should be the one that's through the INBOARD hole at the top of the turret. That is, the two studs that are nearer the centre hole in the top mount, are the two studs that go outboard, adjacent to the wing gutter. The damper stud will then be correctly in the centre of the turret hole *WHEN THE WEIGHT IS ON THE WHEELS*. (It'll look like it's too far outboard until the weight comes on and the spring/damper unit assumes the correct (loaded) inclination.)

Even with the weight off you can be pretty confident it's right though, because it should still be in the right place fore-and-aft; ie, not towards the front of the turret hole, nor towards the rear.

Functionally, the difference it makes getting it right or wrong is probably negligible: there'll be a fraction more load on the damper bushes though, and the whole thing will be very slightly skew.

The worst bit is that every time you open, you'll notice the damper stud's not in the middle of the bodyshell hole - and so will everyone else who looks!

Now, while I'm looking at that diagram, I note an important thing is missing. When Murdo removed the front suspension, he should have found that there was a thick washer on each of those studs, *under* the turret. The studs are recessed in the mounting, and the thick washers effectively fill up that gap. I *think* the earliest cars didn't have those spacers, but Murdo's is very late, so it should. Sometimes you don't notice them, because they stick to the underside of the turret when the spring/damper unit's removed, and either stay there, or fall off later and drop down inside the turret, between the inner and outer pressings, lower down. Either way, it's quite simple:

There should be a thick spacer washer on each of the three damper top mount studs before the assembly is installed in the car. (Otherwise, the nuts are tightening against fresh air, and will tend to deform the top of the turret - and thus become loose with time.)

(And don't forget the rubber spring insulator 157334 either! At least that *is* in the drawing.)"

[yorkshire_spam]

My 1850 WSM mentions the position of the "spring upper finishing tip" relative to the upper mounting plate, but nothing about the plate itself being asymmetric. Doesn't mean it's not though.

[shaunroche]

VA138 has those spacers you mention or at least there were some present when I took the suspension apart at the start of the resto........additionally, they are flat on one side and curved on the opposing face....I think the curved face sits on top of the top hat and the flat face against the car?

I didn't know that the top mounts had to go in a particular orientation and never spotted anything to suggest the contrary, but looking now in this picture, I can't see anything else and as this front subframe assy is how it came off the car (a 1975 model) it does look like the sticky out bit is orientated inboard.....

[RSi]

VA138 has those spacers you mention or at least there were some present when I took the suspension apart at the start of the resto........additionally, they are flat on one side and curved on the opposing face....I think the curved face sits on top of the top hat and the flat face against the car?

I didn't know that the top mounts had to go in a particular orientation and never spotted anything to suggest the contrary, but looking now in this picture, I can't see anything else and as this front subframe assy is how it came off the car (a 1975 model) it does look like the sticky out bit is orientated inboard.....

Yes, they're on RNK too.



It's the rotational part of the strut mount I'm a bit confused about. Measuring the studs they're all very close in measurement.

[yorkshire_spam]

I'm pretty confident what you've been told is inaccurate, as far as I can tell they are rotationally symmetrical.

[Carledo]

TBH, I dunno!

I've never seen any reason to fit the topmounts in a particular orientation other than one stud inboard and 2 outboard and in the many dozens of springs/shox i've fitted, i've never once had any difficulty making the studs line up in the shock tower. The difference, if there is one, must be so small as to be insignificant.

There are some (modern) cars where the triangular topmount is undeniably assymetric and MUST be fitted in a certain orientation, the rear topmounts on Dolomites have a defined orientation that is difficult (but not impossible) to get wrong. But the front ones? Not in my experience!

Steve

[RSi]

TBH, I dunno!

I've never seen any reason to fit the topmounts in a particular orientation other than one stud inboard and 2 outboard and in the many dozens of springs/shox i've fitted, i've never once had any difficulty making the studs line up in the shock tower. The difference, if there is one, must be so small as to be insignificant.

There are some (modern) cars where the triangular topmount is undeniably assymetric and MUST be fitted in a certain orientation, the rear topmounts on Dolomites have a defined orientation that is difficult (but not impossible) to get wrong. But the front ones? Not in my experience!

Steve

When he saw the photo of the NS strut top, this is what he said.

"The nearside front strut's been out before and the top mount hasn't been replaced in the correct orientation. It's an easy mistake to make and yours needs to be rotated clockwise by 120 degrees, so that the centre nut is in the centre of the hole in the turret".

Interesting, as it is off centre.

[Carledo]

TBH, I dunno!

I've never seen any reason to fit the topmounts in a particular orientation other than one stud inboard and 2 outboard and in the many dozens of springs/shox i've fitted, i've never once had any difficulty making the studs line up in the shock tower. The difference, if there is one, must be so small as to be insignificant.

There are some (modern) cars where the triangular topmount is undeniably assymetric and MUST be fitted in a certain orientation, the rear topmounts on Dolomites have a defined orientation that is difficult (but not impossible) to get wrong. But the front ones? Not in my experience!

Steve

When he saw the photo of the NS strut top, this is what he said.

"The nearside front strut's been out before and the top mount hasn't been replaced in the correct orientation. It's an easy mistake to make and yours needs to be rotated clockwise by 120 degrees, so that the centre nut is in the centre of the hole in the turret".

Interesting, as it is off centre.

Then what the discrepancy is, is not in the stud spacing which you have determined is accurate and equal to within 1mm or so (good enough for BL's sloppy 70s standards) but that the shock stud hole is not central within the triangle formed by the 3 studs.

OK, lets assume that that IS the case, if so, WHY? If this was a Ford, with a Macpherson strut, the position of this hole would be CRITICAL as it controls caster and camber, being an extension of the "virtual" king pin.

But it ISN'T a Ford and it ISN'T a Macpherson strut, it's a non rotating coilover shock mounted to the top wishbone of a double wishbone system. Whilst a perfectly upright position for the shock (or an exact angle in) might be desirable in a perfect world, it's hardly essential, anywhere within an inch or two of the hypothetical centreline will do and a couple of mm either way is totally irrelevant.

Even so, the point has been made and I will now check all my 4 Dolomites currently present here (3 of which I have personally built up the coilovers for, with no regard for this) and see how many i've got "wrong". And i'll dig out a couple of spare topmounts and check whether or not the hole is central!

To be honest, if I HAD found one previously where the stud wasn't central, i'd probably have put it down to poor tolerances in the shell anyway!

Every day a school day!

Steve

[RSi]

TBH, I dunno!

I've never seen any reason to fit the topmounts in a particular orientation other than one stud inboard and 2 outboard and in the many dozens of springs/shox i've fitted, i've never once had any difficulty making the studs line up in the shock tower. The difference, if there is one, must be so small as to be insignificant.

There are some (modern) cars where the triangular topmount is undeniably assymetric and MUST be fitted in a certain orientation, the rear topmounts on Dolomites have a defined orientation that is difficult (but not impossible) to get wrong. But the front ones? Not in my experience!

Steve

When he saw the photo of the NS strut top, this is what he said.

"The nearside front strut's been out before and the top mount hasn't been replaced in the correct orientation. It's an easy mistake to make and yours needs to be rotated clockwise by 120 degrees, so that the centre nut is in the centre of the hole in the turret".

Interesting, as it is off centre.

Then what the discrepancy is, is not in the stud spacing which you have determined is accurate and equal to within 1mm or so (good enough for BL's sloppy 70s standards) but that the shock stud hole is not central within the triangle formed by the 3 studs.

OK, lets assume that that IS the case, if so, WHY? If this was a Ford, with a Macpherson strut, the position of this hole would be CRITICAL as it controls caster and camber, being an extension of the "virtual" king pin.

But it ISN'T a Ford and it ISN'T a Macpherson strut, it's a non rotating coilover shock mounted to the top wishbone of a double wishbone system. Whilst a perfectly upright position for the shock (or an exact angle in) might be desirable in a perfect world, it's hardly essential, anywhere within an inch or two of the hypothetical centreline will do and a couple of mm either way is totally irrelevant.

Even so, the point has been made and I will now check all my 4 Dolomites currently present here (3 of which I have personally built up the coilovers for, with no regard for this) and see how many i've got "wrong". And i'll dig out a couple of spare topmounts and check whether or not the hole is central!

To be honest, if I HAD found one previously where the stud wasn't central, i'd probably have put it down to poor tolerances in the shell anyway!

Every day a school day!

Steve

Morning Steve

I've measured everything and can't find any differences in measurements. The strut top centre hole is equal too.

When I come to fit the shocks it'll be interesting to see if I rotate them if there'll be any difference.

Seeing that others have noticed the same, with shocks not sitting central on the strut top hole, what could be the reason I wonder.

[Carledo]

Morning Steve

I've measured everything and can't find any differences in measurements. The strut top centre hole is equal too.

When I come to fit the shocks it'll be interesting to see if I rotate them if there'll be any difference.

Seeing that others have noticed the same, with shocks not sitting central on the strut top hole, what could be the reason I wonder.

Today being a slightly nicer day, i've been out hunting and measuring and what i've found is this:-

Car 1, This I have called my "control", it's a low mile and largely original 74 Toledo, the shox and springs are in the sort of shape you'd expect from OE. NEITHER shock stud is central in the hole, both are equal fore and aft but both are displaced slightly outboard of central by the same amount, perhaps 3mm

Car 2, My modified 1500FWD has GAZ ASP Shox and Sprint springs built up by me for the Carledo originally. The o/s/f pin is displaced forward slightly, maybe 2mm and the n/s/f is displaced rearward maybe 3mm, but both appear to be within 1mm of central in the inboard/outboard plane.

Car 3 My modified Sprint auto, has new, but original spec, standard springs and shox, the O/S is one of a pair bought built up from Ian (Sprint 95M) and the other has the spring from Ian's pair with a new Unipart shocker and a different (used) topmount that I built up myself when the original shocker of the pair from Ian failed. The pin displacement on this car is exactly the same as on Car 2, o/s forward, n/s back and by similar amounts.

I've also checked the 2 topmounts I could easily find and my results match yours, I can find no obvious assymetry, either in stud or hole spacing beyond the + or - 1mm here and there that I would regard as manufacturing tolerance.

So still, I dunno! the results would indicate that though there is no noticeable assymetry in the topmounts, there IS a difference somewhere and it's theoretically possible, with a lot of faffing, to make them match, side to side, though not necessarily to be exactly central in any case. Whether it's worth the effort, is probably up to the individual, I can't see much point, seeing as it has no effect on how the cars drive (all 3 cars above drive fine) You, with your higher attention to concours detail, might feel otherwise!

As to a reason, I can only offer the possibility that the hole in the strut top isn't consistent car to car. Not sure if I can be bothered to measure this! But if this is the case, you will know, as your efforts at rotating the topmount will have no result if the error is in the shell! So i'll wait till you've tried this!

Steve

[RSi]

I think we can safely say it's nothing to do with the shocker mounts, no idea where the chap got this from - but as you can see from what he wrote, he seems very sure of himself.

[Carledo]

So many urban myths............

I remember having a similar discussion with the late great Jon Tilson about screen rubbers. He perpetuated a myth that the available screen rubber from Baines was wrong because it was designed (or marketed) as being for a Toledo or 1500FWD which both came with a toughened screen as standard. And that the thinner Laminated screen was loose in the rubber as a result, leading to many leaks.

Now the leaks are beyond question, especially if the screen is fitted dry, ie without sealer.

The rest of it is garbage, there IS and has only ever been ONE screen rubber with ONE part number (904111) for the entire range. Regardless of what sort of screen was fitted. And when I took a micrometer to both a toughened and a laminated screen, it turned out that the laminated one averaged 20 thou THICKER than the toughened one!

I could go on for hours, but i'll spare you that!

Steve

[matt of the vivas]

I don't think you know anything Steve.
Next you will be denying the existence of the rare 1850 Sprint with Gold Wheels.

[Carledo]

I don't think you know anything Steve.
Next you will be denying the existence of the rare 1850 Sprint with Gold Wheels.

You mean this one?





The more I learn, the less I know and the less I trust what i've learned. As I said above, every day is a school day! Having said that, most of what I learned in school turns out to be BS too, especially history!

Steve

[matt of the vivas]

That's the one!