GTC full lock foul

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philipmasonfrance
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GTC full lock foul

Post by philipmasonfrance » Wed Jul 29, 2020 8:36 am

This Autumn - once the temperature drops a bit - I want to strip down the front suspension for an overhaul. Apart from inspecting the obvious trunnions and bushes I'm going to try to identify why the left front disc fouls the suspension on full lock forwards (not in reverse - play in the set-up?). Any pointers please? I seem to remember reading that suspension arms (I think) could be installed back-to-front or upside down, or something like that. If that's the case, how do I identify if mine is/are correctly assembled?



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GTC full lock foul

Post by DARK STAR » Wed Jul 29, 2020 12:54 pm

If the disc is only touching one side it is possible your rack is not centred.
Why it doesn't do it in reverse I don't know 8)
Wishbone set-up is different for manual / power steering (castor angle I think) and if it's wrong you would know about it when you drive the car.
It's probably even hotter where you are than chez nous - bon courage mate :lol:


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GTC full lock foul

Post by philipmasonfrance » Wed Jul 29, 2020 2:44 pm

A gentle 35°C today .... Steering rack not centred? Is there any adjustment? I thought it just bolted onto the chassis. Or can one play with the TRE's?



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GTC full lock foul

Post by Oldconn » Wed Jul 29, 2020 4:25 pm

Hi Philip, you can play with the TRE's to a small extent, but changing from forward to reverse shouldn't make any differenceunless they are slop^py. I would suspect worn bushes in the wishbones, or maybe a crack in the bracket which fixes the wishbone to the chassis.
35°C here also .


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philipmasonfrance
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GTC full lock foul

Post by philipmasonfrance » Wed Jul 29, 2020 4:44 pm

Oldconn wrote:
Wed Jul 29, 2020 4:25 pm
Hi Philip, you can play with the TRE's to a small extent, but changing from forward to reverse shouldn't make any differenceunless they are slop^py. I would suspect worn bushes in the wishbones, or maybe a crack in the bracket which fixes the wishbone to the chassis.
35°C here also .
Checking back through my maintenance log, I reckon bushes and TRE's have done about 30,000 miles, so the problem could well be there. Hopefully not wishbone brackets as I fitted the reinforced GW brackets some years back.



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Old and Slow
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GTC full lock foul

Post by Old and Slow » Wed Jul 29, 2020 7:58 pm

Won't a slightly loose wheel bearing cause the wheel to "shift a bit" in opposite directions when going from forward to reverse?


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GTC full lock foul

Post by scimjim » Wed Jul 29, 2020 8:12 pm

There’s probably half a dozen or more threads mentioning trunnions or wishbones hitting discs on PAS cars on full lock. Some have fitted lock stops like the earlier cars had, some have shimmed the hubs.


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GTC full lock foul

Post by philipmasonfrance » Thu Jul 30, 2020 7:22 am

scimjim wrote:
Wed Jul 29, 2020 8:12 pm
There’s probably half a dozen or more threads mentioning trunnions or wishbones hitting discs on PAS cars on full lock. Some have fitted lock stops like the earlier cars had, some have shimmed the hubs.
Shimming hubs sounds challenging if I haven't got the shims (I haven't). And does the fitting of stops involve tapping a hole into the suspension arm? Perhaps I'll just make the extra effort not to go onto full left lock .....



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GTC full lock foul

Post by gtcse8 » Thu Jul 30, 2020 8:24 am

Phil what part of the suspension is hitting the disc??.
IF it`s the thread of the trunnion bolt try putting it back through the opposite way.

Some bolts I have encountered are longer than others and when the split pin is fitted more thread is exposed and this catches on the disc.


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GTC full lock foul

Post by scimjim » Thu Jul 30, 2020 8:44 am

philipmasonfrance wrote:
Thu Jul 30, 2020 7:22 am
scimjim wrote:
Wed Jul 29, 2020 8:12 pm
There’s probably half a dozen or more threads mentioning trunnions or wishbones hitting discs on PAS cars on full lock. Some have fitted lock stops like the earlier cars had, some have shimmed the hubs.
Shimming hubs sounds challenging if I haven't got the shims (I haven't). And does the fitting of stops involve tapping a hole into the suspension arm? Perhaps I'll just make the extra effort not to go onto full left lock .....
tapping a hole in the trunnion. Items 19, 20 & 21 - 19 has an eccentric hole (it doesn’t wear loud waistcoats and mustard cords, it’s off centre so you can turn it to different Positions :D )
56C7215F-4D07-4DC4-953F-2678AEC49E52.png
56C7215F-4D07-4DC4-953F-2678AEC49E52.png (195.97 KiB) Viewed 357 times


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philipmasonfrance
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GTC full lock foul

Post by philipmasonfrance » Thu Jul 30, 2020 10:41 am

gtcse8 wrote:
Thu Jul 30, 2020 8:24 am
Phil what part of the suspension is hitting the disc??.
IF it`s the thread of the trunnion bolt try putting it back through the opposite way.

Some bolts I have encountered are longer than others and when the split pin is fitted more thread is exposed and this catches on the disc.
Hi, Mark. I'm going to get under the car next week to check it out properly. I remember that the mark from the contact is about half-way up the disc. I'm ashamed to admit that this has been the situation for many years and it's only since I've retired that I find the motivation to try and sort it out! :oops:



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GTC full lock foul

Post by philhoward » Thu Jul 30, 2020 12:21 pm

If it only does it one way, sounds like the rack isn't centred (and it's been tracked up on one side only)? My 5a would catch the wheel in the arch, but only on one lock. The tracking was only ever touched once, and it was adjusted one side only.


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GTC full lock foul

Post by gtcse8 » Thu Jul 30, 2020 10:25 pm

As Phil says :wink:
If the tracking is not totally central one side of the rack will need the TRE adjusting more than the other.

In my humble opinion of changing/setting up/re furbing racks most fitters just don`t know how the Scimitar system works.
They piss about with adjusting TRE`s because the tracking is out and the steering wheel is not central.

Because the PAS system relies on the track rod lock nuts INSIDE the rack for travel it does not have lock stops on the trunnion, and if the TRE`s are not equally adjusted One side will be further out than the other giving more travel on that side.

Start at the rack and get the central rod Centralised first.
Careful turning of the steering wheel and noting the lock to lock should be good enough.

SOME :!: not All, racks have a drilling in the central rod just for this purpose, there is a plastic plug screwed into the pinion pre load capping plate, but getting the little bugger out in one piece is nearly impossible, if you wreck it on removal a 5/16" UNC bolt X 1/2" long, or grub screw will replace it.
A 1/14" OD Tapered pin is pushed through and the rack moved till the hole lines up, or you may be able to see the locating hole through the 5/16" tapping?, if its there.

Ignore where the steering wheel is till last.
Once the Rack rod is correct THEN the tracking should be done.
After getting the tracking set at Neutral/Parallel THEN set the steering wheel central and knocking off the indicators correctly.

BUT there still is the issue of trunnion bolts catching the disc, WHICH SOUNDS LIKE YOUR PROB ? this may be due to a longer trunnion bolt, or the wrong way round, or the rod off set. :w

I had this problem with a Middlebridge once and finally traced it to the stub axle/vertical link Inner bearing shoulder that had worn away, a 10 thou shim pushed the bearings and hub out enough to give clearance on full lock.
Last edited by gtcse8 on Fri Jul 31, 2020 9:07 am, edited 1 time in total.


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GTC full lock foul

Post by philipmasonfrance » Fri Jul 31, 2020 8:17 am

Ah hah! OK, I'll check that bolt out first (easy and no cost!) then look at getting the rack centralised when I have the tracking re-done. Thanks for all the advice, gents!



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