S3 Steering Rack

[Big Vern]

Hi folks, im about to get the steering rack changed on my 86 S3 NA. I got a reconditioned unit from LotusBits and im about to order some replacement mounting bushes from SJ's. However im not sure whether to get Poly or Rubber mountings. They are the same price but looking for opinions please.

Thanks

Brett 

[Bazza 907]

Rubber, as intended.

[Big Vern]

Thanks, good enough for me

[C43]

I would have thought the poly will speed up steering response a little (but not much), will last longer but might transmit a little more vibration.

Not a deal breaker either way.

[peteyg]

Go rubber! I went poly and it's too stiff. Steering is now really twitchy.

Pete

[C43]

Quite surprised that the bushes made that much difference, might be worth checking your geometry?

 

[andydclements]

Even some specialists say poly  (or perhaps normal compound poly) isn't suitable on some steering bushes, such as ARB mounts being too stiff if poly is used.

@peteyg which ones was that? The ones in the lower suspension arms, or the ARB mounts? If it's lower mounts then, I would have not been surprised if it were S3 pre-'85 lower mounts, but I think S2 are similar to post'85 and think not as susceptible.

 

[drdoom]

Premature perishing of the rubber mounts up front on the early Esprit is not a concern other than the case of the earliest, OEM supplied lower arm inner pivot. With that corrected as specified by Lotus by way of a Metalastic bush fitted arm the front end lacks nothing in terms of steering feel, or durability. I've passed on poly up front, expecting the rubber bushes still available to be up to snuff. FWIW.

Cheers

[Benjamin Vandenberg]

21 minutes ago, drdoom said:

Premature perishing of the rubber mounts up front on the early Esprit is not a concern other than the case of the earliest, OEM supplied lower arm inner pivot. With that corrected as specified by Lotus by way of a Metalastic bush fitted arm the front end lacks nothing in terms of steering feel, or durability. I've passed on poly up front, expecting the rubber bushes still available to be up to snuff. FWIW.

Cheers

Hi, I am based in South Africa, just purchased an Esprit S3 that needs a complete restoration. Could you tell me what steering rack was used on these cars, looks like Ford to me.

[lotus-62]

Benjamin, the rack is not used on any ford (well maybe the capri perana)  but parts can be used from the capri,  however some capri racks have tapper bearings (better) the esprit rack is using needle (pinion shaft) and normal ball bearings (little bit more play)   I milled my esprit rack to take the tapper bearings as this will  eliminate any play in the axial direction from the pinion shaft.     (from memory the capri pinion shaft is too long for the esprit but I have seen a picture of an perana with a shorter shaft btw escort shaft is too short and rack too narrow) I got my parts from a company in b'ham google "kiley & clinton"

Rick

[peteyg]

@andydclements

HI Andy,

I put polybushes on the steering rack mounting brackets to replace the perished rubbers. Everything else is still rubber.

Pete

[andydclements]

Ah, yes those are the ones where I was advised to stick with rubber (on an Esprit and an Excel) as poly makes it more likely to over-steer, I wasn't previously aware of it impacting bump-steer as well.

[C43]

Hi Andy

could you explain the physics behind saying that poly bushes make the car oversteer as I am curious?

ta

Christian

[andydclements]

Sorry, I cannot, it's just what two different Lotus specialists have said when selling bushes, I think it was over-steer but memory fade could mean it was under-steer (cannot think why a little under-steer would be a problem, but over-steer is more difficult to control if unexpected). I would guess that stiffer bush (caused by poly) acts similar to a more rigid ARB.

[C43]

Hi Andy

thanks for the feedback. I know it is always difficult on these forums to know what to believe as you don't know the depth of knowledge of the person you are talking to and to tell the truth its the same with the specialists when it comes to something like suspension setup as generally they are not vehicle dynamics engineers (sorry guys, please don't shoot me).

My experience from quite a few years of vehicle dynamics engineering is as follows:

Polly bushes can transmit a little more vibration, pretty obvious I guess. I have fitted stiffer bushes to both an S2 (my brothers) and and S3 turbo (mine) and I could not feel more vibration, but theoretically it's there.

Polly bushed steering rack will locate the rack better sharpening up the car (a little, you might not even notice) such that turn in is quicker. However, as I said the change is small and you might not notice it. Understeer / oversteer change will be negligible.

 Polly bushed ARB on the front will sharpen up turn in. This I think you can feel and to me feels better, I would be surprised if anyone says otherwise. I guess you could argue that on limit mid corner the car might have a little more understeer. However, again the change will be very small.

Now I get the argument to keep the cars as standard as possible, I totally understand it. But given one of the biggest items that affects handling, the tyres, one can't get original spec I see no harm in subtly changing other items to help.

cheers

Christian 

 

[drdoom]

The ARB mounts are rather firm in the original rubber so nothing really called for in terms of substitution there. Hardly likely that understeer would be magnified unless a firmer poly set were to restrict articulation, and that would be a very clumsy effort in every sense. Not a chance that oversteer would be incurred, in my estimation.

As to the rack mounts, again I'd suggest that the original Esprit front end has ample measures of steering feel if in good fettle. Stiffer poly bushes would possibly add harshness/increased kickback over rough pavement without improving anything.

Bumpsteer management is a matter of steering versus suspension articulation, done initially via steering rack vertical placement, as provided for in Lotus' mounting design. Further pursuit could involve altering the tie-rod end height at each upright, and on from there. Rapidly diminishing returns in this, though all will be for nought if it's actually a matter of worn components overdue for replacement.

Cheers

[drdoom]

I defer to Christian on his observations concerning turn-in sharpness, and to his point that alternative tyres make the rigid pursuit of OEM spec more dogma than practicality.

My own, admittedly ancient, seat time in early Esprit was most memorably in a car fitted with 50 series Pirelli P7, on BBS 3-piece wheels. That was a car in very good condition overall, on Koni shocks and with the front TC arms replaced with Lotus' upgraded parts but otherwise original. Simply lovely steering feel with that set-up, really rather electric.

[Andyww]

I am not sure why people mess about with different suspension bushes as Lotus were, and are, world renowned suspension experts and spent a lot of time getting them right.

Exception is if the replacements are the ones qualified by Lotus in the more recent upgrade programme.

Having said that, the rack mounting bushes seem to be an anomaly. On earlier cars, the Elan had rubber rack mounting bushes but then the Europa had its rack solidly mounted to the chassis with no rubber at all. The Europa never suffered from any downsides from this. 
The same poly bush discussions happen on Ferrari forums and the same applies, the original manufacturer knew what they were doing. Some people fit semi-solid rotating wishbone bushes to their 308/328 which ruins the suspension, but some people have thrown away the rubber rack mounting bushes and fitted solid spacers and reported improvement.

[C43]

Hi

I can see peoples point when it comes to keep the car original, Lotus generally know what they are doing when it comes to setting a car up. However there are a couple of things to remember; technology has moved on, what was state of art 30 years ago is not now and we don't have to work to the same compromise as Lotus when it comes to production costs or making the car driveable for everyone.

I think the good part of owning a Lotus (and I suspect old Ferrari or Porsche) is no two are the same, we all tune them to our own preference.

I do want to caution people about the shore hardness of the rubber bushes they are getting. I saw some supposed Lotus spec ones last week that are much much harder than you would ever want to fit. So if you do go rubber just check they do not have the consistency of rock!

cheers

Christian

[andydclements]

As Christian indicated, even the Lotus rubber bushes sold now are not "original", the compound has had to change to meet ever-changing regulations, so hence the Lotus programme that devised their poly-bushes which achieved the original handling characteristics.

[drdoom]

I am prompted to recall that the classic Elan formerly owned was fitted with solid metal rack mounts and had the rubber bushed column coupler replaced with a steel u-joint. With considerable care taken to see bump-steer minimized, road wheel offset chosen to align tyre contact patch with steering axis intersect at pavement that car had superlative feel with utterly minimal kickback. That was on 185/60 tyres with Koni's and uprated springs, all else as standard.  I believe Lotus made the wheel change to Speedline for the S2 with that patch intersect as one objective at the front end.

Agree with the lads regarding suspect specs for the "replacement" rubber mountings currently on offer. I have some concern with transaxle hanger bushes versus cast alloy hanger bracket in that recently acquired bits have been found to shift out of place through nothing more than handling in the course of mock-up assembly. That work has been sidelined entirely for much of the past year owing to household renovations, will post a thread in the months ahead if further work corroborates the early observation.

[Gis]

I’ve swopped my old steering mounts for poly ones a few months ago but wasn’t too happy with them. Some micro vibrations, it just didn’t feel right. Next ordered a set of OEM lotus rubber mounts from SJ. There are 3 variants on offer at SJ. The poly ones, aftermarket rubber and Lotus OEM rubber. The OEM lotus rubber mounts are about 3x as expensive as the aftermarket set but they both fit perfectly. With the polys the smaller mount needed trimming at the sides since the are too wide. The mount is quite hard and not easy to trim as you can see in the pics below (including my poor trimming skills..) one thing I want to point out is the small mount thickness difference overall and at the base in particular. The OEM rubbers are noticeable thicker and softer and the steering rack sits at least 2mm further forward on the passenger side. Micro vibrations are gone, all feels good now.

[Jeanvm]

Why would you want to change the standard set up? The Esprit has a wonderfull handling and steering!

[Gis]

11 hours ago, Jeanvm said:

Why would you want to change the standard set up? The Esprit has a wonderfull handling and steering!

Good question. For me: lack of insight in this case (A better word for inexperience 😉). Mind you for suspension bushes, the correct polys work well. Reason for posting; so others can make an informed choice. 

[Gis]

So in my own case the learning here is to avoid poly. Dims (on small one) don’t fit, compound too hard. Trying to be smart saving a few quid and then having to double down with the correct parts. Aftermarket rubber might still be an option if the sizes are correct (to be verified by someone who actually uses them). OEM works as advertised, at higher cost. Use rubber if you wanna be safe 😂