Suspension - where to start?

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gungehead
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Suspension - where to start?

Postby gungehead » Thu Jul 30, 2015 1:20 pm

I would like to upgrade the suspension a little but do not know where to start.
I want to retain a comfortable ride and am not after performance/fast road/track handling, but would like more sure footed handling, less bouncing and less body roll.
What is the best plan of attack and what are the reasonable DIY jobs?

I have fitted poly bushes to my cars in the past and I am quite happy with them but which ones should I fit? Which ones transmit noise, vibration and harshness in to the car?
I would like to fit poly bushes to the anti roll bar at least.

I think the dampers (certainly the front) need replacing - new standard ones or Koni/Gaz adjustables and which (Koni or Gaz) are best?

Upgraded springs, how stiff can you go before comfort is compromised?

Thanks

Dave
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piman

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Re: Suspension - where to start?

Postby piman » Thu Jul 30, 2015 3:15 pm

Hello Dave,

I have used Superflex poly bushes in my Triumph and I'm very happy with them, very long lasting. That's what I will fit to my MK 2. Watjag sells up rated front springs but I don't know how much it will affect the ride, not too much I would guess. Koni dampers have a very good reputation and again is what I have in my Triumph.

Alec
Mk 2 3.8 (long term restoration), MK1 Triumph 2.5 P.I.,2.5 X Type Estate, 564 Hymer Motorhome

Martec
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Re: Suspension - where to start?

Postby Martec » Thu Jul 30, 2015 4:03 pm

Hi,

There are a number of issues to be taken into account with suspension, it is a black art because no-one takes the time to sit down and read to understand what you are trying to achieve, wider rear tyres on an understeering car..............der wrong.

Probably the best cheap book I've found on suspension is 'How to make your car handle' by Fred Puhn ISBN 0-912656-46-8.

The car in its original spec was very good in its day, and that is where the problem lies for modern drivers. Modern cars are very stiff so suspension can be hung off the shell and it will do as you ask, but the MkI and MkII where Jaguars first attempts at a monococ shell (no separate chassis) and so as I found out it is very whippy front to back, all the weight is at the front due to the large heavy cast iron engine, and in its day cars were allowed to roll ...........a lot, see the racing photographs.

Nowadays cars have stiff anti roll bars (ARB) to keep them flat and so keep the wheel upright with maximum tyre patch contact. The MkII had positive front camber so it would have lighter steering but would slide in corners, you will never make it as good as a modern car, but it can be made far more sure footed.

Firstly get a vernier caliper and measure the wire diameter of the springs, standard is 0.635", uprated from 'Watjag' is 0.710" and as the spring tension calculation is by raising the diameter to the power of 4 then the uprated spring is almost twice the stiffness. Both these springs give good handling and comfort, the springs on our car were 0.620" and caused 10 years of discomfort due to a 'nodding dog of a car, neck ache.

The later ARB is a larger dia than the early one so resists roll better.

The front suspension is fully adjustable so shimming the upper wishbone to give negative camber (1/2 to 1 degree) will give better tyre contact in a corner.

Dampers, the choice is yours 15 years ago Koni Classic (adjustable) were regarded as the best, but you have to remove them to adjust them (a damper only controls the spring when it moves).

Poly bushes, as the front subframe is on 4 rubber mountings you can fit all in poly (I have) without any noise or vibration (they now say the modern bushes (power flex) don't transmit NVH!!!!). I fitted superflex in the front but Polybush seem OK for the MkII.

As you can see most of my comments are on the front end, as the chassis is so whippy there is not much you can do for the rear. Everyone fits new rear springs and then tells me my car is too low at the back (I have the original rear springs but a big gas tank in the boot)!! in practice the front suspension should have the lower wishbones horizontal (ignore 3 fingers between tyre and wheelarch as they are not symetrical). Then the back should be approx 1" higher (measure at the sill).

You can fit a full kit of polybush to the rear but if you have a concrete motorway you will feel it. I replaced all in poly except for the centre spring pad and the front end spring pad.

It is your car and it all depends on what you want and what you are prepared to pay someone to do for you. Standard in good original condition is very good, if you want to press on then negative camber, stiffer front ARB, standard springs and polybushes is the way forward ..............for me (there is a calculation in the book for matching front and rear springs) but Jaguar got it right. At the rear mostly polybush is fine, I've moved over to poly bushes because the new rubber ones were destroyed after 2 years.

Brian
MY2000 3ltr S type manual standard car with leather seats, cruise control and mistral blue metallic paint.

1961 3.8 MkII manual, Indigo blue, nolonger runs on LPG, everything else uprated

MartinHaven
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Re: Suspension - where to start?

Postby MartinHaven » Mon Aug 10, 2015 5:55 pm

Hi Brian,

very interested to read your thoughts on poly bushes...

My '65 Daimler has its original bushes and I am looking at replacing the (very) saggy rear springs, followed by overhauling the front.

I had thought I'd go for rubber bushes all round, for quiet and comfort - but will the modern replacements last or should I go for poly?

Contemplating new dampers too and - as I hope to only do this once - wondering whether the difference for Gaz or Spax might be worth it, in the long run.
1965 Daimler 2.5 V8

Martec
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Re: Suspension - where to start?

Postby Martec » Mon Aug 10, 2015 8:04 pm

Hi Martin,

I've commented on this elseware, I'm not the oracle but have had years of discomfort and repeated changes of springs and bushes, you pays your money and takes your chance.

My money is on poly other than where the suspension touches the body, springs to match the frequency of oscillation (originals are good) a stiffer ARB and good dampers.

Was it you on another post who said the tyres were rubbing on the body? If the panhard rod body and axle mountings are sound (a common rust area) then the axle needs to be realigned equidistant inboard from the front of the wheel arches, also the dampers are also the bump stops, so have you looked to see which part of the body is rubbing on the tyre?

Brian
MY2000 3ltr S type manual standard car with leather seats, cruise control and mistral blue metallic paint.

1961 3.8 MkII manual, Indigo blue, nolonger runs on LPG, everything else uprated

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piman

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Re: Suspension - where to start?

Postby piman » Tue Aug 11, 2015 7:01 am

Hello Brian,

just thinking ahead really as I'm busy with my Triumph so the Jaguar is not being touched.

I've never liked the Jaguar designed Panhard rod, it just looks wrong being so short so either make a full width one or alternatively fit a Watt linkage. The other thought as I have a spare front anti roll bar is to fit it to the rear? Good dampers go without saying (I already have the Watjag front springs and Koni dampers for the front.) I also bought some heavy duty rear springs off the JEC classifieds but have no idea of their rating?

Alec
Mk 2 3.8 (long term restoration), MK1 Triumph 2.5 P.I.,2.5 X Type Estate, 564 Hymer Motorhome

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Re: Suspension - where to start?

Postby Martec » Tue Aug 11, 2015 4:51 pm

Hi Alec,

If you look at the rear of the car then its a mess from the perspective of stopping corrosion. I built mine from a wreck, the rear spring boxes were almost falling out and the back end of the sills were almost pop riveted on. Very little was left of any of the jacking points or the panhard rod attachment to the body.

I bought and fitted new panels, and took great care to ensure the spring boxes were in the correct position. The holes in the rear jacking point (facing forward) and above this were all closed off and as I said before the seat pan is now double skin and plug welded to improve strength. What the panhard bracket should have been welded to was all cut away and remade and some modification (Jaguar seemed to think that spotwelding 3 sheets of steel together in one go was a good standard!!!!).

You maybe better off with a watts linkage, and definitely a longer panhard rod, but I experimented with a full width one on the Marina and later took it of with no improvement or loss of location.

If you are booting on a bit on a back road and being chased by an independant rear suspension car then you have no chance as the back axle wriggles about like puppies under a blanket and you will feel it. On a smooth fast road it is fine as standard (rough roads let it down).

Be careful with the rear antiroll bar, if you look at any modern car then they have both front and rear ARB's and the rear is always smaller dia. Our MY2000 S type has 32mm front and 18mm rear ARB but the shell is very stiff. The Marina has a rear ARB half the dia of the front and I can induce power oversteer.

The MkII is very whippy as I found out when rebuilding it so it is debateable what use a rear ARB will have. In practice with matched front to rear springs, polybushes, good damper, a thicker front ARB (a later car) and negative camber to the front, change down and boot the car through a corner (preferably if the boss is not present) then the back end will oversteer a little to help. With stiffer rear springs you will already have the effect of unsticking the rear end. I tried stiffer rear springs and the rear ARB on the Marina and instead of a power slide it hopped disconcertedly. It now has standard front and rear springs.

It probably sounds odd coming from me, but I believe most manufacturers made a good job of matching front to rear springs so I like to stick with standard springs, dampers to only just control them and use negative camber and ARB's to adjust the handling.

The weight of the LPG tank in the boot shot the MkII spring match to hell so I was forced to weigh everything, corner weight it and calculate the correct front springs. We are now at the stage of a surprisingly comfortable 54 year old car which we used for the Scottish holiday and the boss is very happy to use it for next years Southern Ireland holiday. Its only taken 13 years to get to this point.

Sorry its long winded Alec, but I've been experimenting and learning for a while now, the above is boiled down from that work.

Best wishes
Brian
MY2000 3ltr S type manual standard car with leather seats, cruise control and mistral blue metallic paint.

1961 3.8 MkII manual, Indigo blue, nolonger runs on LPG, everything else uprated

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piman

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Re: Suspension - where to start?

Postby piman » Tue Aug 11, 2015 5:50 pm

Hello Brian,

thanks for your thoughts, and I've a bit of time to ponder. Coincidentally my Scimitar has a Watt linkage and a Salisbury 4HA axle so (assuming that spares are still available) reduces the amount of engineering I would need to do.


Alec
Mk 2 3.8 (long term restoration), MK1 Triumph 2.5 P.I.,2.5 X Type Estate, 564 Hymer Motorhome

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piman

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Re: Suspension - where to start?

Postby piman » Tue Sep 01, 2015 9:18 am

Hello Brian,

"I've never liked the Jaguar designed Panhard rod, it just looks wrong being so short so either make a full width one or alternatively fit a Watt linkage"

Further to my comment earlier, I went to Oulton Park this weekend and nosing in the paddock I came across a MK 1 saloon which had a full width Panhard rod so someone else must have felt it worth while to do what I was thinking? I also bought a complete Watt linkage from a Scimitar on E-Bay for £10, so worth a punt even if it proves to be impractical to fit.

Alec
Mk 2 3.8 (long term restoration), MK1 Triumph 2.5 P.I.,2.5 X Type Estate, 564 Hymer Motorhome

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Re: Suspension - where to start?

Postby Martec » Tue Sep 01, 2015 11:27 am

Hi Alec,

When you get the time to do the modification I would be very interested to see and hear your feelings of the result.

Just a small point I saw a suspension set up (may have been an escort) where a 'Watts linkage' had been fitted, but the arms had been angled up so the mounting points were horizontal from each other, and it didn't work until he refitted it with both arms horizontal and the chassis mounting points, one high, one low!!! does that make sense?

What ever happens the panhard rod/ Watts linkage is the only thing giving lateral location of the axle, so there is a lot of load going into the rear body structure.

On a point you raised before about the height of our car at the back, as the front springs are now matched to the old sagging rear springs and the fact that I don't trust the new repro spring to match our old original springs. I'm going to make up some spacer boxes to lower the centre of the spring in the spring box so as to raise the car by and 1" to 2" and shim the front spring to the correct height. I've looked in the manual again and there is nothing definitive to height setting, just the old engineers advice.

Best wishes

Brian
MY2000 3ltr S type manual standard car with leather seats, cruise control and mistral blue metallic paint.

1961 3.8 MkII manual, Indigo blue, nolonger runs on LPG, everything else uprated

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piman

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Re: Suspension - where to start?

Postby piman » Tue Sep 01, 2015 3:07 pm

Hello Brian,

yes that makes sense. It's a deceptively simple but efficient system and also gives the option of altering the roll centre, not that I'd know which way to go if any?

Yes, it will put load into the body and I'm quite mindful of that, and at least the load is shared by both sides unlike a panhard rod. Aston Martin in the DB3 and possibly 3S sports car had a projection with a bearing at the rear of the differential which located in a vertical U channel attached to the chassis keeping the axle in check.

Alec
Mk 2 3.8 (long term restoration), MK1 Triumph 2.5 P.I.,2.5 X Type Estate, 564 Hymer Motorhome

lornemalvo
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Re: Suspension - where to start?

Postby lornemalvo » Wed Sep 27, 2017 10:24 am

My Mk 2 is at the garage for a full restoration, currently having rear spring hangers/suspension replaced. I bought new rear springs from SC Parts and noticed there are no friction buttons or spacers in between the springs. I decided to dismantle the springs and either lightly grease in between the leaves, or fit UHMW low friction tape in between, having read up on UHMW (its use seems more common in the USA). My restorer wanted to wrap the leaves in Denso tape. This seems a good idea in some ways, but as we are fitting Polybushes (comfort grade from Poly Bush), I do not want to firm up the springs any more, but rather I want to achieve as much compliance in the springs as possible.
Having thought about it a great deal, I decided against the grease, as I'm sure it would attract grit and eventually work like a grinding paste. I am pleased that I took the trouble to dismantle the springs, as the inner surfaces are quite rough, like a rough casting. Pretty shoddy in my opinion. Not having enormous amounts of time, I sanded the surfaces, then sprayed them with a couple of thin coats of industrial black paint. I then fixed the low friction tape and will be reassembling the springs today. I'm not sure if it will make much difference, but leaf springs are supposed to be able to move against each other, and I want to give them the opportunity to work as they were designed to. Unfortunately, I will not have a before and after comparison, as the car has been off the road since 1989. Having said that, my restorer just put the same springs on another Mark 2, and wrapped them in Denso tape, so that will provide a limited comparison. My handbook advises an occasional light application of oil, so I may go with that.

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piman

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Re: Suspension - where to start?

Postby piman » Tue Oct 03, 2017 9:45 am

Hello Lornemalvo,

when leaf springs were far more common, spring gaiters were sold to allow the springs to be greased thoroughly then covered to keep the grease in and the water out. Denso tape is a good alternative but very messy, if you haven't used it. I would imagine that a thorough greasing then Denso tape is an excellent way of preserving the springs and keeping them quiet.

Alec
Mk 2 3.8 (long term restoration), MK1 Triumph 2.5 P.I.,2.5 X Type Estate, 564 Hymer Motorhome

PPV
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Re: Suspension - where to start?

Postby PPV » Tue Oct 03, 2017 1:03 pm

I notice the comment by Brian about the limited information on vertical measurements to set up the suspension and I agree with this however on pageN.30 of the manual there is a dimension '[email protected] from the datum line to the centre hole of the rear torque arm bracket and then looking at page K.3 there is a diagram of the rear suspension. The first allowed me to ensure the rear part of the body frame was in roughly the right place and then I checked the free camber of the rear springs against the diagram on page K.4. The variable in this of course is the strength of the springs but mine were sized as per the dimensions given and were the originals. I think it generally stands Ok but that was many years ago when I did this work and I now thinkmyrubber buffers in the centre of the spring and the front mounting pad need changing. I jst thought this may help check the set up.
Hope it goes well.
Regards,
Paul V
Mk2 3.8
Mercedes A45 AMG
Mercedes AMG GLC43


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