I have been chasing a steering wheel shimmy, that appears at between 77 and 82 kph and makes the wheel oscillate at about 3 times a second, at an amplitude of about 1 inch at the rim. This has been driving me mad. The car tracked perfectly, it was not a wheel balance type vibration, there were no other symptoms and the entire front end had been rebuilt with all new bits 3 years ago. So here are all the things I did with the help of my retired farmer mate Michel, basically one at a time, that did NOT fix it:

• Changed steering rack mounts
• Changed ball joints and track rod ends
• Changed bearings and stub axles and uprights, car aligned and wheels re-balanced (even though they were not out of balance)
• Changed subframe rear V mounts
• Swapped tyres and rims front to back
• New motor mounts fitted
• New OEM bottom wishbone bushes fitted - in which I found out that the fixed end of the brand new pin I had fitted 3 years ago had not been welded properly and the bushes had not been compressed by the fixing nut at the front. The welded end had just given. So I thought GOT IT! but I hadn't!
• New poly top wishbone bushes fitted - even though the original slipflexes looked perfect. Note here: the diameter of the top wishbone metal fixing rod, onto which the bushes slide, is 15.72mm - which is exactly 3/5 of an inch which is what the imperial diameter originally was, no doubt. The internal diameter of the steel inner sleeve of new OEM slipflex bushes is 16mm, and this produces an huge amount of play into the bearing: it allows, pre tightening, the wishbone arm to move about 1 inch at the other end! The poly Superflex bushes I used had inner sleeves of the correct diameter.
• The last existing brand new subframe in the known world tracked down and fitted - some improvement but problem not eliminated.
• New front tyres just in case.

And here is what did fix it. I began to realise what I had sort-of suspected for a bit, that I had a funny harmonic going on between the subframe and the body, that was making the subframe/body vibrate at a certain speed and produce the relatively low frequency steering wobble. So this is what I reckoned and did:

• The new OEM six shot bushes I fitted were very compliant, so using stuff called Stixall, I filled the holes completely and left it to dry for a couple of weeks. Fitted the bushes. Shimmy completely GONE at 77 to 82 kph. Maybe just a touch at 95 kph. This proved to me that the harmonic idea was correct.
• On my car I have aftermarket SPAL electric fans and they are quite heavy; particularly so when you consider they are mounted on the body (whereas the engine driven fan is on the motor), and are well forward of the axle line. I also have sound and heat proofing tiles on the bonnet in place of the OEM black stuff which had fallen to bits, and these are much heavier. I also had a three row heavy duty radiator and with its water in it, it is about substantially heavier than a 2 row. So I got the Management's permission to buy an Ally one. Now beware: the Chinese ebay ones are NOT lighter than the OEM two row - at least not according to the suppliers from whom I asked for the weight. So I bought an Alicool (well known UK make) which weighed only 5 kilos compared with 17 kilos for my three row and 12 to 16 for the ally ebay ones I asked about. Add in the extra water and you save 20 kilos or thereabouts, again this weight is well forward of the axle line. The new rad arrived last week and has just been fitted. It dropped straight in perfectly.
• I reckoned that removing this extra weight, which is all about 18 inches forward of the axle line would change the harmonic.
• I installed an extra body bracer. In the diagram below, item 3 is a diagonal bracer and I had an extra one in stock, so I put it on the other diagonal - which is what Jaguar did with the convertible, using a welded X bracer.

This morning, having fitted the Alicool rad, a half hour road test went FANSTASTICALLY well. The car is back to its OEM "riding on cream" feel, with the steering just perfect and the turn-in to corners also sharper. All steering shimmy gone. My final take? Use poly six shot bushes, which have no holes and are the same price as OEM metalastics.
I am just thrilled to have my car back and running properly, at last!
I forgot to add my great debt of gratitude to the Wizard of Oz (bows to the Southern cross) who throughout this time has been a pillar of strength and advice on the hotline between Oz and France.

 

Greg,
You mentioned recommending polys to the six shot bushings. The sub frame have the rears as well. Are there polys for the rear subframe mounts as well and would you recommend changing them to polys as well? I believe the the rears of the front subframe are not the same type but more of a V type mount. is this the case? ..or are you suggesting that only the fronts are better with polys alone?

 

The rear V mounts are not the same, and polys are not needed (and not available either) as they are in solid compression. The rears take just about all the weight of the car and transmit it into suspension and the wheels. The front six shots are really there to prevent front/rear subframe shunt under heavy braking, cornering and acceleration.
Quite why this problem happened to me I do not know, the car was fine for years, and this just kept getting more prominent. So I would only say fit polys if you had the problem, or wanted a firmer setup. But it seems if I had fitted poly six shots to start with, the problem would have been 80% solved at once and the colossal expense would have been far less!

 

Good to hear that fixed the problem.

BTW did you ties the 2 diagonal braces together where they cross?

 

Hi Greg, my approach was different than what you did, for front wheel shimmy,big wide tyres!

i do have the forward top bar in place , but car still felt loose/flexable, so i added a top larger bar from the top of the brackets may not have been the best idea , but it stopped the loose feeling and more responsive steering input changes! also solid mounted the steering rack with aluminum bushes!
it triangulated the top bar reinforcement!
ron

 

I did not, because to do so I would have had to remove the aircon condenser and empty/recharge the aircon. But, amazingly, JCP still have the OEM convertible centre-welded X brace in stock (idiot money though) item 2 below. This bolts straight in I expect, if so I could bolt it in just by removing the rad, as I did with my extra diagonal. If a windfall arrives I will get one, and am looking out for one secondhand in the meantime.

Cheers
Greg

 

I would not spend the money on the OEM brace, IMO it needs gussets where the braces cross to reduce twist.

If you weld the braces where they cross and add triangular gussets this will stiffen the car significantly. Google roll cage and look at the gussets where the bars cross.

 

Thanks Warrjon, when I have to degass the aircon, for whatever reason, I will tack weld (in situ) the point the diagonals cross, the get them out and do just that. The metal the tubes are made off is very thin though, so I shall have to be careful!

 

Latest update:
As the weather after the winter began to warm up, my shimmy problem returned to a degree. I decided to buy some poly six shots from Superflex. These are solid poly and far less compliant than the OEM bushes as now available. I removed the modified OEMs and found that they had lost quite a bit of the rigidity I had put into them by filling the holes, for whatever reason. To fit the Superflex bushes the procedure is:

• burn or cut out the rubber from the steel outer tube on the old bushes. The polys have to be pressed into that tube.
• the polys have a "cotton reel" shape and the steel outer tube fits nicely between the raised ends of the "reels".
• I actually ground down the raised end on one end of the polys to make the bush easier to press into the steel outer, using silicone grease to help the process. A large vice is fine for this job. Once in place the lack of the raised part has no effect on bush performance as they are squeezed in place by the huge bolt and washers.
• The OEM bushes have a steel inner bonded to the rubber, and a further steel inner that slides into that (13 in the diagram). The polys have no steel inner bonded in, but they do need the removable OEM tube to be pressed into them, again using silicone lube.

• refitting the bushes is straightforward, but I used larger diameter washers than the OEM ones (14 above) so that the polys were squeezed into the outer when the huge bolt was tightened up. The steel inner when pressed in was about 2mm shorter than the bush material each end, so this idea worked very nicely and when fully tightened all was solid and the inner steel tube held by the washer while the poly was compressed too. Pics attached show the idea.

I have only had the chance for a very brief test, but the shimmy that was creeping back has totally gone. I really strongly advise this mod for anyone rebuilding their front end, turn in is improved noticeably, ride quality not affected at all as far as I could tell, with just maybe a bit more thump over big pothole and similar big irregularities.
My theory is that the OEM six shots are not quite the same as they were 15 years ago, and they were on my car at least, allowing a certain degree of lateral harmonically induced rocking of the subframe at certain speeds. Also I noticed that going uphill also increased the symptoms, as the weight or load on the bushes shifted.

 

I would second that Greg. I've had the poly six shot for 6 years now and they do sharpen up the steering.

I have also just fitted poly in the small raduis arm bush on advice from Norm. Mine were toast after 6 years,

I like the Superpro poly bushes, I have them in the front sway bar and upper wishbone and DO NOT squeak.

 

Well done Greg, AT BLOODY LAST.

Time for a beer or 3.

 

Greg, could you post a link to the Superflex bushes you used? I'm not sure what a shot bush is. Is it #10 in the update post diagram?

 

Yes, number 10, it connects the front of the subframe to the body.
https://www.superflex.co.uk/products.php?cat=211
Bottom left item on this page. Warren has used the Aussie equivalent. The Superflex admin lady, Christine Frew is unbelievably helpful and efficient.

 

Thanks. I'm wondering if those will be good replacements for the rubber under the car I suspect I might have to replace. They look like they have a range of good kits.
However, re-reading your report, I notice you said "just maybe a bit more thump over big pothole and similar big irregularities" so I wonder if these would perhaps not be the best choice. I'm primarily interested in ride comfort over handling--she handles fine as is, and isn't a tossable sports car anyway. I want to waft....

 

SD
unless, like I did, you have a specific problem to eradicate, stick with OEM metalastic bushes.