Rear Suspension Springs

[super6al]

Hi Everyone,

I've purchased new rear springs as 'standard'. If you look at the attached photos however, there is a difference in the number of coils between the original still marked (just!) Green/white & the new GSV1001 ones marked Green/red. Any ideas if these have the same poundage & spring rate as original

Thanks

Alan

[BlueTR3A-5EKT]

Factory original green with white stripe was 216275 the original rear spring. Gsv1001. An Unipart rehash part number. 

[Peter Cobbold]

The old springs will be stiffer judged from the number of coils: 7 coils vs 9 on the new .     BUT The diameter of the wire is also critical , a mere mm extra on the diameter makes for a much stiffer spring. Cant tell that from the photo, you need to measure witha micrometer. IF the new is slightly greater diameter wire then that might add stiffness and compensate for the extra coils.

Coil spring calculator here:  http://www.tribology-abc.com/calculators/t14_1.htm

note stiffness varies with fourth power of wire diameter, d.... hence need to use micrometer

Peter

[BlueTR3A-5EKT]

LEACY the M G specialist offer GSV1001 red and white stripe. http://www.leacyclassics.com/gsv1001.html

[super6al]

Thanks for the replies,

Peter

The new spring diameter is indeed thicker 13.55mm v 13.1mm for the original. In order to use the spring calculator I need to input number of 'working coils'  - what is meant by this?

BlueTR3A-5ekt

The springs on the Leacy link are the same as I have purchased. I had a look & can't find a red/white strip one

Thanks

Alan

[Waldi]

Hi Alan,

a working coil is where it is not restrained by the adjacent coil, so as soon as the bottom or top coils get “air” to the adjacent coil this is where the working coils start. The new one has approx. 9 effective (working) coils, but you should be able to make a mote precise count.

Waldi

[Peter Cobbold]

2 hours ago, super6al said:

Thanks for the replies,

Peter

The new spring diameter is indeed thicker 13.55mm v 13.1mm for the original. In order to use the spring calculator I need to input number of 'working coils'  - what is meant by this?

BlueTR3A-5ekt

The springs on the Leacy link are the same as I have purchased. I had a look & can't find a red/white strip one

Thanks

Alan

Alan,

So the new coil has wire that makes it stiffer by (13.55/13.1)^4...................which is 1.13 or 13%

The number of coils would make the new softer by 9/7 or  1,28   or 28%

Overall the new springs are a tad softer. by 13%, Assuming the same type of steel is used.

Its not going to make much difference to handling Ride height amd squat might chnage a bit, but you can shim to adjust height

Peter.

Edited June 23, 2019 by Peter Cobbold

[super6al]

Thanks Waldi/Peter

I've fitted a new spring to one side, flushed/refilled the lever arms & re-bushed with superpro, (the other side should be complete this week after I've repaired some rust found around the B post base). Once I fit the other side I should be in a position to understand how the changes have affected the height & squat etc. One thing looks slightly alarming is the amount of toe in on the side completed. I haven't measured yet & I need to get the suspension 'settled' after both sides are completed but it looks excessive & I'm not sure it will settle out. I haven't changed the shim set up or brackets so I'm thinking the only the thing that should have changed would be the camber or ride height due to new springs,bushes & tyres. Anyway I'll check later this week & hopefully it will be ok

Alan 

[super6al]

Hi 

So I've now fitted both springs & took the car for a 3 mile ride to settle it & check everything was ok.

When I returned home I checked the rear toe in & camber as best I could using string, a builders square & a vernier.

The results are :  Toe in R/L 4mm .

                             Camber RH -2.5mm , LH -2.85mm

Changes I've made - Trailing arms & Damper link new Superpro bushes. Dampers flushed & new SAE20 oil. New springs. New 165 tyres.

Brackets are as standard & I've not changed any shims.

Should I do more miles to let everything 'bed in' before correcting?

Thanks

Alan

 

 

[Peter Cobbold]

Alan,

PU bushes will give less toe-out than rubber so I would reshim the t/a pivots to bring the toe closer to parallel. But it is very important to have tightened the pivot bolts with the car on all 4 wheels.- not as easy as saying it !

The negative camber looks Ok but as the springs settle that might increase, or if you load the boot. Can be cured easily with a PU shim under each spring.

Peter

[super6al]

Hi Peter

I didn't tighten the pivot bolt with all 4 wheels on the ground, only with the weight on one wheel at a time. I guess I need to loosen & redo both sides again.

Also done some further research & when I measured from my string line, I didn't take into account the increased track at the front. However the rear wheel toe in is easily visible by eye sight.

It will be Friday before I can get back onto it.

Thanks
 

Alan  

[Peter Cobbold]

Alan,  That's better than doing it with the t/a at full droop. If the chassis was close to normal ride height the pivots should be OK. Peter

[Will]

With PU bushes, tightening on the ground should not be necessary as the bush rotates on the spacer, unlike rubber.

[super6al]

Thanks Gents

Looks like I need to adjust shims to get somewhere near.

2 more questions :-) 

1)The Brown Bible says to add shims to the outer bracket to reduce toe in - Will I get the same effect by removing a shim from the inner bracket (I don't have any shims)?

2) The figure quoted is 0~1/16" rear toe in, it then states its referenced to the corresponding front wheel with a tolerance of 0~1/32" - does that mean 1/16 Total for both L/R rear wheels or is it  1/16 for each wheel but they can't be more than 1/32 toe in compared to its front wheel. Its confusing but to my mind there is a difference?

Thanks

Alan

[Peter Cobbold]

Removing a shim from the inner is acceptable to give more toe-out, you can add the removed shim to the outer to give even more toe-out. I imagine looking down on the t/a and a triangle joining the cetnre of the wheel and the inner and outer pivots. The triangle is of course rigid. So when an inner shim is changed the triangle pivots about the outer pivot, and vice versa......a diagram to scale will show how much

The BB refers to rubber bushes which compress more tnan PU under road load, so ignore the BB and set your toes parallel. I use the bodywork as a guide

Peter

[astontr6]

On 6/22/2019 at 8:17 PM, super6al said:

Hi Everyone,

I've purchased new rear springs as 'standard'. If you look at the attached photos however, there is a difference in the number of coils between the original still marked (just!) Green/white & the new GSV1001 ones marked Green/red. Any ideas if these have the same poundage & spring rate as original

Thanks

Alan

Hi Alan,

My old SAH book shows the Green/White spring as Late TR6, rated @ 354lbs./ins with a  fitted length of 8.81" from CP52868 but does not show Green/Red type. It has to be remembered that BL modified the spring rates on the rear at least 4 times in an attempt to cut down spring wind up.

Bruce.

[Bill944T]

to cut down spring wind up

Go on, in terms an electrical guy can understand!

Regards

Bill 

[astontr6]

1 hour ago, Bill944T said:

to cut down spring wind up

Go on, in terms an electrical guy can understand!

Regards

Bill 

Hi Bill,

The original TR6 had very soft springs on the rear not much better than a TRA4 IRS. This meant that under harsh acceleration the rear end of the TR6 would compress the rear springs because of the extra torque of the 6 cyl. engine and the rear  would squat down and the front would start to point upwards as if you were getting ready for take off! This feature was commented on by early testers and also led to revised settings of the Armstrong shocks. I now hope this is clear for you? My 1973 CR TR also suffered from this problem to a degree. I replaced my springs over 30 years ago with 420 ibs./ins problem gone, plus a better ride.

Bruce.

[Bill944T]

the rear  would squat down and the front would start to point upwards as if you were getting ready for take off!

Thank you Bruce. Seeing this pictured in the road test articles as a teenager was the inspiration to buy my 71 TR6 when I got to 20 years old, as oddly enough, my then DAF Daffodil didn't do likewise! But, it could go almost as fast in reverse as it could forward. I'm using the word "fast" in context of 28 bhp...................... Not that many would be likely to have seen what I think is the only surviving 1964 DAF on eBay recently as a complete "project" for £9k+... It didn't sell despite having what appeared to have everything included to rebuild it................

Regards

Bill 

[super6al]

Thanks everyone,

Over the weekend I did some further (hopefully more accurate) measurements. This time I took into account the front track additional width & rotated the wheels, checking 3 separate points on each rear wheel. I now have an average of toe in as follows. RH -3.02 mm LH -3.85 mm.

Camber measurements are significantly different to what I had previously measured at RH -6.5mm equates to -0.88 degrees & LH -2.5mm -0.38 degrees. 

The toe in I will correct by swapping shims over. Not sure what to do about the RH Camber. I didn't remove the brackets on that side, I only fitted new t/a bushes & springs. I did find the inner t/a pivot had some old damage, like it had been 'squashed' at one end of the rubber bush. I corrected it best I could by reaming from the 'good' side. I also had to open the brackets slightly to get the new bushes & pins to fit. I can only think this has altered the geometry or it has always been this way & now the higher profile tyres exaggerate the camber. Brackets on both sides are standard 3 notch inner 1 notch outer.

I have to say even like this the ride is much more accurate & the new 165 TTrac tyres are a hoot compared to the 20 year old 185 pirellis previously fitted!    

Alan

[Peter Cobbold]

Alan, I'd set the toe and then put ina few decent drives to see if the camber corrects itself. The PU bushes will have been comprssed as you tighten the brackets and may need to settle into the correct  average running position.

Peter

 

[super6al]

Thanks Peter

Today I swapped a shim on each side from inner to outer bracket. The new toe measurements are now RH +0.15 mm & LH - 0.58 mm. Camber didn't change. I will do as you suggest before making any other changes.

Alan