Steering rack mountings - standard or polybush?

[Alty Ian]

Do the polybush mounts make any appreciable difference? I am using Polybush everywhere else and the steering rack ones seem quite thin and rigid already.

Any advice or comments?

[jag68]

They are significantly better, and really tighten the steering up. They are still flexible enough however to take most of the jolt out of bumps feeding up through the steering gear unlike the solid ones which can really bite. You won't be sorry to use them.

[Heuer]

My experience is different - I went back to standard rubber. They return the car to what Jaguar intended and make it a pleasure to drive rather than a chore.

[abowie]

Another vote for polybush.

[Heuer]

The only advantage of polybush is its longevity but the rubber bushes last 12 years+ anyway. They squeak in dry weather and increase harshness without doing anything to improve the handling although once people fit them they seem to convince themselves they are an improvement. If you are wedded to polybush be aware they come in different colours each of which denotes a grade of stiffness - black, blue and red - so go for the one that matches closest to rubber. There is a fix for the squeaking which involves drilling the anti-roll bar supports and fitting grease nipples :?

[jag68]

I quite vividly recall a track day 15 years ago when for a contribution to charity we would take people out for a run around the track. My race car ('65 E Type) didn't have a second seat so I loaded my passenger into my stock E Type with stock wheels tires etc. At the end of the main straight is a left turn which in the stock E Type you take at about 100 mph (130 plus in the race car). I turned in and nothing happened. The car just kept on straight. It was only for a moment, but it was a panic stricken moment, then the stock rubber bushing in the rack mounts caught up to the turn and around we went, probably 10 feet further into the turn then planned. Scared me stupid. I was used to solid rack mounts in the race car which have no reaction time. As a result I put solid mounts in the stock car, but they are too harsh for the road. The red, being the stiffer poly mounts are the ticket. No delay - no scares. I appreciate that a car as the factory intended it is, at times, desirable, but how many of us who actually drive their cars have totally stock cars? Most of us have modifications for reliability, and I think modifications for safety have to be at least as valuable. And - after all this is a design out of the 50's. Some handling improvements are desirable.

[jag68]

As an addendum: I'm only speaking of the rack mounts. Poly suspension mounts are different. I agree with David. They squeak badly after a few years. I went back to stock this spring and as far as handling goes I notice no difference. My autocross (slalom) times haven't changed.

[44DHR]

A definate yes from me too.

I thought we had a discussion about this issue before, but my point then was even more reason for a more positive mounting if running wider tyres to avoid the "loading up" mentioned above. The increased resistance of the wider tyre's contact patch causes more flex in the steering rack mountings before they load up and transfer the lateral movement to the wheels.

Cheers,

Dave

[Alty Ian]

Sounds like the consensus of opinion is standard for original cars with 185 x 5 tyres and polybush for anything with uprated performance or wider wheels/tyres.

[PeterCrespin]

I thought we had a discussion about this issue before, but my point then was even more reason for a more positive mounting if running wider tyres to avoid the "loading up" mentioned above. The increased resistance of the wider tyre's contact patch causes more flex in the steering rack mountings before they load up and transfer the lateral movement to the wheels.

Since the rack mounts should be constrained by safety devices permitting very limited movement laterally - a couple of millimetres maybe - one would expect they play to be taken up during hard cornering regardless of tyre. There is (or should be) no extra movement available just because of a tyre or wheel change. It might be that the small deflection would be used up more frequently but it ought to be the same defection regardless. Of course if the limit stops are missing or incorrectly assembled, anything could happen

Pete

[44DHR]

Pete, you are technically correct - as usual - and there is minimal available movement when the "fail safes" are correctly installed.

However, I was trying to point out that with wider tyres and a higher contact patch there is more manual effort required to turn the steering - especially at slow speeds - and even more to those of us with smaller 15 inch steering wheels - to give potentially more lateral shearing effort on the rack mountings. Checking old rubber mounts is an essential maintenance exercise on old and potentially hardened rubber units which experience infrequent use. My full page article in the Jaguar Enthusiasts magazine and featured on its cover's front headline mentioned in a previous post on "Steering Rack fail safes" in December 2013 outlined my wish that people are aware of this vital component which are often overlooked in re-building, or simply not fitted.

I agree the movement is minimal and restricted to a few millimetres, but the difference is noticable with Polybush mountings compared to soft or partially sheared stock rubber - as is going to solid mounts - when doubled on the side to side extremes. Steering is critical to get right and I just feel even millimetres do make a difference when transmitted up through the steering components to the resultant movement at your hands.

regards,

Dave

[PeterCrespin]

I don't disagree, except in the area of 'feelings' versus measurements.

For example, the fitment of a smaller steering wheel does absolutely nothing to the forces at the rack mounts, even when stationary. You might feel it does, and your arms might complain at the effort, but that's just a reflection of the reduced input leverage, which has zero effect on the rack mounts. It has an effect on the column hardware but not the rack mounts.

This is in contrast to the loading-up that happens with wider or stickier tyres (which might paradoxically 'feel' easier if their fitment coincided with adoption of, or changes to, a larger steering wheel or power steering respectively).

I agree polysbush will feel different because a change of material will affect how those few millimetres transmit up the steering gear from wheels to driver. Ditto solid mounts, which would introduce a whole other set of issues. And yes, millimetres do count and feel does count when enjoying the car to the max - even if the effect on outright performance of a given car/driver combo is debatable. I'm pretty sure an elderly Jackie Stewart in an E with 185s, delaminated mounts and incorrect failsafes could run rings around you or I with poly mounts and 225 Yokohamas. Such is life.

Pete

[44DHR]

Pete,

I agree on all counts.

I look forward to that opportunity for us to race Jackie Stewart - and again on that one I'm sure you would be right too - but wouldn't it be great to try !!!

regards,

Dave

[Shimmer1]

Series 1 4.2 Open E Type.
I fitted solid steering rack mountings in an attempt to restore directional stability to my car which had had suspension and steering work done, an exchange rack and new metalastic bushes were fitted. It felt, on a dry Motorway, as if there was a soft rear tyre in the wet--terrifying. This becomes most noticeable on Motorways. The rear lower wishbone bearings are OK.
It didnt solve the problem. On exploring the new N/S front upper wishbone I found it was a sealed for life unit possibly from Barratts. The O/S ball joint was a newly fitted standard one. I have replaced both front upper wishbones fitted with standard ball joints, adjusted castor and camber angles and it has improved the handling. Unfortunately it still feels less driveable than before this work was done. The exchange rack worries me as all three grease nipples (rack and track rod ends) fell into bits when the grease gun was removed were they made in China? The rack was very notchy and noisy. I was told to liberally grease it, with some improvement.
I took it out today and my question is are the solid rack mounts now making it twitchy? The back end feels better. After reading this post I think Red polybush mountings would be better am I correct and who stocks them? I have had this car for 43 years and for the first time it frightens me going in a straight line.

[Shimmer1]

More info about above,
It has Konis all round and runs on Michellin 205/70VR 15 Tyres

[jag68]

The poly rack bushings are available at SNG. Part no C20087U. I fitted a new (not rebuilt) rack from SNG a couple of years ago. It was a bit notchy at first but has now become "normal" in that regard. Needed a bit of breaking in I assume. It's difficult to comment on handling issues as there are any number of things that can cause difficult handling. I've used solid or poly rack bushes for the last 10 years (at least) and they don't cause the car to be twitchy - actually they really tighten it up. Is it possible that you have some toe out in the front - or, not enough self centering due to, for example, a) a too tight bushing in the rack, b) not enough positive castor? What condition is the rubber in the rear trailing arms? The list of things is almost endless. Does the twitchy behavior occur under throttle, turning in, trying to just go straight? What were the grease nipples made of that they should just fall apart?

[rfs1957]

Can anyone point me to a source of hardware installation info regarding the steering fail-safe parts ? Think I can see that it involves spacers and longer bolts but my "faithfully restored" car has faithfully irrelevant stainless bolts everywhere but none of the fail-safe componentry. Only taken me 10 years to twig ............

[mgcjag]

Hi Rory.....look here towards the and are a couple of photos with good detail viewtopic.php?t=5101&postdays=0&postord ... s&start=20 Steve

[rfs1957]

Thanks for that Steve, looks like you have to walk on eggs on this one if you are not to look dumb ! Where does your mechanical engineering degree have to come from before you dare confess that you can't grasp the logic behind the use of spacers (fixed length stops) on the steering side, and the use of adjustable-length stops on the opposite ?

[Shimmer1]

I have a result! I took my car for tracking this AM. and although it has been tracked twice in the last four months it was found that the total toe was 16.7mm its been adjusted to 1.6mm and already feels like my old car.
I will await the weather for ducks to improve before I take it out for a run but i`m optimistic.
I have rack mounts with spacers, washers and nuts and bolts together with a spare rack tube if previous poster would like photos. I don`t have photobin or simillar, PM me your mobile number and i`ll send via my phone.