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tr6 trailing arm question


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I have a damaged offside rear trailing arm, which needs replacing, couple of questions for you

 

1 my car is a 1972 cp 75985 I believe there is a way of identifying the correct arm ? as different ones were made I am told.

 

2 I would have thought the aluminium casting would have cracked, and not bent, but alloy IS soft I suppose, can a casting such as this bend?

 

I would be gratefull for any help.

 

regards

 

Peter

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Hi Peter

The trailing arms on mine had a date scribed on each of them in quite large figures, don't know if they all have this, mine's a late car [1975] and the scribed dates were consistent with the age of the car, ie. slightly earlier.

Most aluminium alloys tend to bend first, then break, but a lot depends on the actual alloy.

Ron

Edited by ron
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Hi Peter

The trailing arms on mine had a date scribed on each of them in quite large figures, don't know if they all have this, mine's a late car [1975] and the scribed dates were consistent with the age of the car, ie. slightly earlier.

Most aluminium alloys tend to bend first, then break, but a lot depends on the actual alloy.

Ron

 

Hello Ron,

weather permitting I will take off the arm tomorrow, its been painted a gloss black so I will give it some nitromors and look for an ident.

regards

Peter

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Hi Peter

The trailing arms on mine had a date scribed on each of them in quite large figures, don't know if they all have this, mine's a late car [1975] and the scribed dates were consistent with the age of the car, ie. slightly earlier.

Most aluminium alloys tend to bend first, then break, but a lot depends on the actual alloy.

Ron

 

Here's an example of the TA date, hand written into the sand and then cast into the TA. I think it is way cool having this connection to a human that contributed to my TR, even if it was just the TA.

 

http://i38.photobucket.com/albums/e119/fos.../TR6/TADate.jpg

 

Stan

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Here's an example of the TA date, hand written into the sand and then cast into the TA. I think it is way cool having this connection to a human that contributed to my TR, even if it was just the TA.

 

Stan,

 

I agree with you. I do not have a picture of the dates on my trailing arms but indeed, I remember seeing the dates on mine.

 

joe

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These are shots of a twisted TA . Appears to have been shunted from the rear.

No cracks apparent , but very bent.

I rmember reading somewhere that the TA's were changed during production.

Is this true ?

I have a TR5 & TR6 plus 4 extra TA's and I can't see any diiference in any of them besides the dates.

John F

 

PICT2367.jpg

PICT2366.jpg

PICT2365.jpg

PICT2363.jpg

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What a grand response from all of you, thanks to you I now know they will bend. As no one has mentioned any differences in type, I assume that all TR6 TA's are the same, weather here is wicked

 

so will wait until better weather before stripping out the arm.

 

thanks again lads

 

regards

 

Peter.

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Hi Peter, I don't know if you have read Roger Williams excelent book on how to restore tr5 and 6's, but he refers to the differences between early and late trailing arms and the importance of using the correct one. Yours I would suppose are early. In any case he say's that the casting manufacture meticulously incorporated the date of casting on each trailing arm. So you need to match this. Be aware that Stag and Saloon trailing arms are not compatable with the TR6, Rich

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removed the TA and after stripping the drum, shaft etc, found a large crack behind the brake mounting plate, sixpack had advertised a pair of arms in the buy /sell section of the forum in early jan.

 

luckily the dates inscribed on these were nov 1971, my cars a june 72 so they were ideal. I got the pair for a very reasonable £50, a bargain when they came with revington bushes and SSteel

 

brackets and bolts of the right grade, thanks to ALL for very usefull info.

 

regards

 

Peter.

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  • 13 years later...

Hello everyone,

I wake up this discussion on trailing arms.

I noticed that my rear trailing-arms are both early types but the rear right is dated 15.5.69 whereas the rear left has no date, only 3 numbers 1 3 3 (see pictures).

Is there any known geometry difference between original (15.5.69) and replacement (1 3 3)?

I have, like some other owners, rear left positive camber (around 1 deg) whereas rear right is approx -0,5deg...

Many thanks and take care! 

William

Screenshot_20210206-183146.png

Screenshot_20210206-182936.png

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Hi William,

the TRailing arms were never officially dated and I would imagine you have to originals.

The camber is affected by the chassis height above the ground.  As you laod the car the camber becomes more negative.

It may be that your off side spring is weakening and getting shorter.  Check the gap between the tyre and the wheel arch. It's a rough check 

The near side camber may be correct as it should be apprx 0' to 0.5' negative with  the car loaded

 

Roger

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55 minutes ago, reginald said:

Hello

The later arms had a bigger Webb on the shock absorber mount not sure what year it came in

Richard

Hello Richard,

Thanks for your message. Both arms on my 69 car are early arms (on pictures). The third picture showing early / late arms differences was posted by Derek Graham in another discussion.

William 

 

 

Screenshot_20210207-232058.jpg

Screenshot_20210207-232213.jpg

Screenshot_20210207-232520.png

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4 hours ago, RogerH said:

Hi William,

the TRailing arms were never officially dated and I would imagine you have to originals.

The camber is affected by the chassis height above the ground.  As you laod the car the camber becomes more negative.

It may be that your off side spring is weakening and getting shorter.  Check the gap between the tyre and the wheel arch. It's a rough check 

The near side camber may be correct as it should be apprx 0' to 0.5' negative with  the car loaded

 

Roger

Hello Roger,

Thanks for your message. My offside having positive camber, could a weakened spring be the origin? Can you confirm? I would have thought that a weakened and shortened spring would give more negative camber.

But if you are sure about it, well that confirms my wish concerning rear springs refurbishment.

I do have too much space between top of rear tyres and wheel arch lip (4 fingers moving easily, 165 hr15 tyres). One year ago, wheel center - wheel arch lip distance was 40.5cm offside (rear left with positive camber) and 41.5cm nearside (rear right with negative camber).

Thanks for your feedback, 

William 

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2 hours ago, RogerH said:

Hi William,  You are in France - aaarrrggghhh.

 

Do you have a Left hand drive OR right hand drive car?

 

Roger

 

Left-hand CKD car :-) that's why I talked with left/right rather than offside/nearside 

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Have a look at the TA mounting brackets on the chassis, there are notches on them, tell us what you have, notches to the top or the bottom, number of notches inner and outer positions.

John

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12 minutes ago, John L said:

Have a look at the TA mounting brackets on the chassis, there are notches on them, tell us what you have, notches to the top or the bottom, number of notches inner and outer positions.

John

Hello John,

Thanks for your post. Both sides 1 notch up inner, 2 notches up outer. Springs coils have green and white paint marks (350lbs/in?).

William

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Hi William,

with no weight on the car both rear wheels should be either straight up or a fraction either side (1/2 degree) - but should be equal.

If it was me I would take the springs out and check their free length.

if they are the same length then consider how old they may be.  New springs are not too expensive.  350lbs is quite soft. Does thwe cae suffer from squatting when accelerating hard.  Consider 390lbs etc.

If new springs solve the unequal situation then you may need to adjust the camber - that is good fun:blink:

his is a good site for camber info.         http://www.buckeyetriumphs.org/technical/Suspension/AdjRS/AdjRS.htm 

pr you could consider adjustable brackets.

 

Roger

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Make sure your trailing arm brackets are not cracking through the holes where they mount to the chassis.

When I had my TR250 to bits a few years ago so I could repaint the chassis, I found all 4 were cracked to the point where failure was not far away, and it couldn't be seen from underneath.

I noticed the replacement brackets were a bit  thicker steel than the originals

Neil

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2 minutes ago, RogerH said:

Hi William,

with no weight on the car both rear wheels should be either straight up or a fraction either side (1/2 degree) - but should be equal.

If it was me I would take the springs out and check their free length.

if they are the same length then consider how old they may be.  New springs are not too expensive.  350lbs is quite soft. Does thwe cae suffer from squatting when accelerating hard.  Consider 390lbs etc.

If new springs solve the unequal situation then you may need to adjust the camber - that is good fun:blink:

his is a good site for camber info.         http://www.buckeyetriumphs.org/technical/Suspension/AdjRS/AdjRS.htm 

pr you could consider adjustable brackets.

 

Roger

Hi Roger,

Indeed the simplest solution would be to change springs and see what happens.

I have gone through Buckeye articles for quite a long time now and even got pretty good fun in determining which brackets combination I should use on rear left to correct the positive camber. 3 down outer and 2 down inner seemed to be the best combination. I know that Tom Fremont had the same issue than me on rear left on 2 cars and corrected with brackets changes on the rear left.

Maybe I should consider checking any damage on the rear left trailing-arm? I heard they bend quite easily...

Where to begin with when having an IRS geometry issue is the real reason I started this discussion, and trailing-arms seemed a good starting point :-)

Car doesn't squat excessively under hard acceleration. 

William

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2 minutes ago, Stagpowered said:

Make sure your trailing arm brackets are not cracking through the holes where they mount to the chassis.

When I had my TR250 to bits a few years ago so I could repaint the chassis, I found all 4 were cracked to the point where failure was not far away, and it couldn't be seen from underneath.

I noticed the replacement brackets were a bit  thicker steel than the originals

Neil

Hello Neil,

Thanks for your suggestion, I will check this when I decide to overhaul the suspension. I had this issue on my 76 car... but it was visible from underneath the car! I replaced them immediately. 

William 

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15 minutes ago, RogerH said:

Hi William,

here is a cracked bracket - this was found from underneath the car by the MOT man.

P1020449ab.jpg

Hi Roger,

Thanks, we will check. It can be pretty tricky to see at first sight, indeed.

William 

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