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V8 Rear Suspension

Postby Jeffrey Lister » 20 Mar 2017 16:49

Does anyone know the correct ride height front and rear for a 1974 GT V8,mine currently rides at;
nsf 34.5cm osf 35.00cm
nsr 36.5cm osr 36.5cm

Measured from the hub centre to the chrome strip on 185/65SR14. This gives good and responsive handling therefore I don't want to raise the ride height

I am considering fitting parabolic springs to my V8 CB, my questions are, does the parabolic offer any advantages and secondly what would the ride height be after fitting them. The car is fitted with telescopics.
Or should I fit leaf springs MGOC part number BHH1133 and would that give me the same ride height as before.

Finally are anti tramp bars useful for everyday driving with the occasional spirited blast,
Jeffrey Lister
 
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Re: V8 Rear Suspension

Postby Derek Gardner » 10 Apr 2017 19:43

I have fitted a set of parabolic springs this winter and I am very pleased with them. I set the ride height a little above what it was to allow for settling down. It gives a vastly improved ride especially with the potholes we seem to have nowadays all over. Had to tighten up U bolts after a few miles as the settled down. No more back jarring and banging. In my view a great improvement. I have got gas shocks also set mid range.
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Re: V8 Rear Suspension

Postby Mike Howlett » 10 Apr 2017 20:58

Paul Hunt has collated quite a lot of data on ride heights which you can find on his very useful web site. Here's the link
http://www.mgb-stuff.org.uk/suspensiont ... rideheight

Fitting new leaf springs seems to be a bit of a lottery as to whether they give the same height as before. I guess its all down to the temper of the spring steel the leaves are made from.
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Re: V8 Rear Suspension

Postby Victor Smith » 12 Apr 2017 10:38

Jeffrey,
A key word search using with "MGBGTV8 ride height" in the search box on the V8 website homepage produces a couple of links:
> There is a note on the V8 website with the ride heights on my MGBGTV8 which has the original suspension. I am not sure whether Brost & Co are still in business as property values in the area of London where they had a business have risen substantially making residential redevelopment an attractive use of the property they had.
http://www.v8register.net/subpages/v8wh ... nsions.htm
> V8BB thread on parabolic springs for the MGBGTV8.
http://www.v8register.net/FilesV8WN/V8B ... 190308.pdf
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Re: V8 Rear Suspension

Postby Jeffrey Lister » 13 Apr 2017 06:23

Thank you all for your replies to my question.

I have fitted the parabolic rear springs but noticed that the rear was riding too high. By releasing the U bolts and moving
all of the parabolic spacers from below the the main tapered spring to the top keeping the overall thickness the same, the ride height was reduced to a more acceptable 40cm measured from the wheel centre to the bottom of the chrome strip.
With the Gaz telescopics overhauled ( by Gaz ) for a lesser cost than replacing the car now rides better over the minor bumps and pot holes.

At the moment I don't seem to have the need to fit anti tramp bars but that may change as I would be interested to see what difference they would make.

Regards

Jeff Lister
Jeffrey Lister
 
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Re: V8 Rear Suspension

Postby John Hale » 14 Apr 2017 19:22

Hi Jeffrey

When you mention parabolic springs I assume you are talking about what we used to describe as "Taperleaf", a single leaf spring of tapered thickness? If so then they offer significant advantages over the conventional multileaf springs in terms of ride comfort and life and they probably won't settle as much in use but they are not so good in terms of torsional stiffness (wind up), which may increase the tendency for axle tramp on high torque applications like the V8. The RV8 is equipped with anti tramp bars no doubt for this reason but I think you are right to see how you get on without them which depends so much on how you drive your V8.

Many (many) years ago I worked in suspension development including fatigue testing of leaf springs and I don't recall us ever breaking a taperleaf spring once they had "run in", so anecdotally at least once you pass the first few thousand miles you'll be set for life!

Regards, John Hale.
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Re: V8 Rear Suspension

Postby Chris Yates » 18 Apr 2017 18:24

I have a similar problem with 15" wheels and Hoyle suspension F and R
The ride height is too low and the suspension too hard. Fine for a circuit but not for the long trip to southern PortugaI if I want to keep the co pilot happy. I have reduced tyre pressures to 27 r and 25 f and I am now going to adjust the dampers and then see whether I need different springs
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Re: V8 Rear Suspension

Postby Victor Smith » 18 Apr 2017 18:39

Chris,
I recall John Hoyle mentioning there are a range of adjustments with the Hoyle kits so I would be careful just plunging in and making random changes. I think you would do better to take the car to a specialist, ideally the company in SE London that has taken over the Hoyle business from John, and let them apply the knowledge and experience they have so you get a good result. http://www.hoyle-suspension.co.uk/
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Re: V8 Rear Suspension

Postby Mike Howlett » 19 Apr 2017 08:38

Ride height on the Hoyle suspension is easily adjusted by winding up and down the lower spring seat on the damper with a C-spanner. Be aware that there is a locking grub screw in the threaded ring that must be slackened before attempting to wind the ring up or down. I have recently been adjusting mine to get the steering tie rods parallel to the ground.

Slackening off the dampers might help a hard ride, but altering the spring rates is the best solution. I wonder what springs you have? I have tried several different ones. For the rear on my GTV8 it seems that the standard 10" long 300 lb/in spring is the right one for me. On the front I started with 9" long 300 lb/in springs which were too hard in my opinion. I felt that the front of the car kept bobbing up and down, as if the springs couldn't compress at all when a bump was encountered. So John Hoyle sent me a set of 9" x 200 lb/in springs. These were better but probably a bit soft, so I now have 9" x 250 lb/in springs at the front, and the ride is good. An MGB is never going to ride like a heavy modern car. It will always react to bumps, but mine is now quite comfortable and has stopped the oscillating movement.

I see from the latest Hoyle web site that the standard springs now supplied are 10" x 300 at the rear and 9" x 250 at the front, so by chance I have settled on those recommended items. I suspect that a 225 lb/in spring might be a slight improvement for the front, but I don't have a set of those. You will need a spring compressor to remove and replace the springs from the dampers.

The springs can be bought quite cheaply from suppliers like Merlin Motorsports (https://www.merlinmotorsport.co.uk/s/su ... er-springs). They are standard 2.25" ID springs available in a wide range of ratings and lengths. Or you can buy them from Mark at Hoyle. Back in the days when I set mine up, John Hoyle used to send me springs to try free of charge, which is why I have three different ratings on the shelf.
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