coilovers

Ask questions on technical aspects and problems!

A different section under here for each of the models.

Moderator: The Midas Forum Staff

coilovers

Postby Jin » Wed Dec 07, 2016 5:24 pm

in the pursuit of upgrading the suspension, im considering many options from direct replacement within the hydragas housings to a more simple direct coilover solution.

on that note, can anyone foresee an issue with mounting the top of a coilover at the front of the car to the fiberglass inner wing?
There is already a shock absorber sited nearby.
i appreciate it wouldn’t be wise to simply mount a coilover direct, the surface directly above the hydragas sphere is relatively flat so I’m thinking of a 10mm thick 100 x 100mm spreader plate to bolt the coilover to?
i could even find some 10mm thick ally angle since there is an angle in the vicinity that would increase surface area also.

Has this been done before? i appreciate that this proposal puts all the weight now on the body and inner wings rhart than now where the weight of the body is supported by the subframe.

Any thoughts?

Thanks
https://easywider.co.uk/ universal flexible wheel arch extensions
Jin
 
Posts: 454
Joined: Fri Aug 01, 2014 10:33 pm

Re: coilovers

Postby ACourtney » Thu Dec 08, 2016 11:00 am

Hi Justin,

I wouldn't try to support the coil-over with the underside of the wing. At least not without considerable reinforcement. The force that goes through a damper is an order of magnitude lower than that through the spring - the spring supports the weight of the car and in the worst cases (such as when you try to emulate your rally heroes and yump the car) it can see several g. The damper is only there to control the speed at which the wheel can move. It only generates force when the suspension is moving and the force should vary with the speed of the suspension movement, i.e. the faster the suspension is moving the more force the damper generates.

If you look at the back suspension of a Mk1, Mk2 or Mk3, which mount through the rear inner wings, you will see that the turret is extremely thick and supports the top of the coil-overs in 3 dimensions. The underside of the front wheelarch is less thick and, in the case of the Mk4/Cortez, is really only supported in 2 dimensions, as the damper mounts closer to an edge, but not a corner.

When fitting front dampers, to all models, it is important to make sure that the suspension bottoms out on the original bumpstop on the subframe and not on the damper. The shock loads that would be fed through a damper bottoming out are likely to be several orders of magnitude higher than the regular damper loads, so higher still than the spring loads. Several owners of Mk3s have had their front dampers punch through.

The hydragas units have some damping built in. So the additional dampers we fit are only there to add a bit more control and usually some adjustment, to allow the driver to tune the car to their liking. If you are replacing the hydragas units with springs then you will probably need new dampers too, although if you have adjustable dampers you might get enough damping by setting them to the top of their range.

I have not tried any of the coil spring options as I have pursued the route of re-gassing the hydragas units, but I have seen a couple of them on cars. Allan Hopkins fitted coil-overs mounted to fabricated turrets which bolted on to the subframe. I don't know if he made that up entirely himself, or adapted someones existing kit. The Watson's spring set up, which uses a small spring fitted in place of the hydragas unit, has also been tried by several members. I have also noticed that some Metro GTi racers have replaced their hydragas units with coil-overs in a similar fashion to Allan Hopkins.

I hope this is of help.

Regards,
Alistair
User avatar
ACourtney
 
Posts: 488
Joined: Thu Dec 04, 2008 12:22 pm
Location: Oxford

Re: coilovers

Postby Jin » Thu Dec 08, 2016 8:54 pm

Hi Alistair.
Thank you for your informative reply, very much appreciated and valued.

Regarding reinforcements to the fiberglass inner wings to take a coilover, what would be a good starting point?
My thoughts were a 10mm thick ally plate approximately 100x100mm square, beyond that the inner wing isn't flat so will be tricky,
Do you have any links to any of what you have mentioned above? What is the norm when converting mk3s to coilovers?.

If I go down the coilover route I'm going to have to fabricate some mounts for the rears too.

Any help much appreciated
https://easywider.co.uk/ universal flexible wheel arch extensions
Jin
 
Posts: 454
Joined: Fri Aug 01, 2014 10:33 pm

Re: coilovers

Postby Stuart » Thu Dec 08, 2016 9:01 pm

Guessing a fair amount of the inner wings needs removing to fit an MG TF frame ?

Image
User avatar
Stuart
 
Posts: 1719
Joined: Tue Dec 02, 2008 8:29 pm
Location: Derbyshire

Re: coilovers

Postby Jin » Fri Dec 09, 2016 1:00 am

Quite possibly, shame really
https://easywider.co.uk/ universal flexible wheel arch extensions
Jin
 
Posts: 454
Joined: Fri Aug 01, 2014 10:33 pm

Re: coilovers

Postby ACourtney » Mon Dec 12, 2016 11:09 am

Jin wrote:Hi Alistair.
Thank you for your informative reply, very much appreciated and valued.

Regarding reinforcements to the fiberglass inner wings to take a coilover, what would be a good starting point?
My thoughts were a 10mm thick ally plate approximately 100x100mm square, beyond that the inner wing isn't flat so will be tricky,
Do you have any links to any of what you have mentioned above? What is the norm when converting mk3s to coilovers?.

If I go down the coilover route I'm going to have to fabricate some mounts for the rears too.

Any help much appreciated


Hi Justin,

If you were to reinforce the inner wings to take a coil-over then you would need to thicken the laminate by laying up extra layers on the inside of the wing, or even cut out a section and mould in a turret section. Either would require a lot of laminating work and also most of the front of the car would need to be disassembled to gain access. With due respect, a 100x100mm ally plate stuck underneath the wing is a load spreader and not a reinforcement.

I don't have any links to the Watsons springs, though several regular posters have bought them. I do have a photo of Allan Hopkins' car taken a few years ago at one of my open days

ImageCIMG3067 by Alistair Courtney, on Flickr

As you can see it looks like a home made bracket, but it bolts neatly on to the subframe. I have no idea what the spring, or damper, rates were that he used. The spring applied here would need to be softer, with more travel, than one of the Watsons coils as it acts further out along the top arm.

Regards,
Alistair
User avatar
ACourtney
 
Posts: 488
Joined: Thu Dec 04, 2008 12:22 pm
Location: Oxford

Re: coilovers

Postby Jin » Tue Dec 13, 2016 12:44 am

evening Alistair
thank you very much for your reply, I really appreciate the input.
I spent the weekend under the car with several rules and squares etc. and have also realised that "beefing up" the front inner wings isn't an option, not least because the surface above the front Hydragas unit isn't flat anyway so my idea of plating it isn't going to work :(

reality is also dawning on me regarding replacing the hydragas units direct for springs, the issues are mainly cost, I've had a quote last week to machine the necessary components to mount the springs in place of the Hydragas units (similar to the Aussie setup) of £650, add to that 4 dampers at £200 and 4 custom springs 4200lb @ £80 + vat and postage each and its getting pretty expensive, not only that but I would still need to fabricate damper mounts at the rear so many obstacles to overcome.
with this shelved I'm left with my original wish to replace with coilovers acting direct on the wheel centre so no ridiculous 4000lb springs required,
I've worked out I can fit a 9" coilover between the boot floor / subframe to hub if I make an offset lower mount to the hub, or better still make 2 spring seats between the 2 and have a remote damper.
regarding the front I did consider a setup very similar to that on the red car you have pictured when I first bought the car 3 years ago, but I discounted it on the basis that I didn't think 4 8mm bolts would be enough to take the upward load acting on the spring nor did I think the remaining half of the Hydragas clamp (attached to the subframe) would be strong enough to resist upward and inevitably sideways load in use.

does anyone know if the car in the picture has additional support behind the damper mount or is it literally just a plate bolted to the 4 Hydragas 8mm bolts?

while on this subject, as I understand it the other Midas models - mk3s etc had rear coilovers from build and a custom bracket that bolted to the rear hub to take the mount? does anyone have a pair assuming they fit the rover metro trailing arms? this would save me a job as a starting point
cash waiting
many thanks for the help
:)
https://easywider.co.uk/ universal flexible wheel arch extensions
Jin
 
Posts: 454
Joined: Fri Aug 01, 2014 10:33 pm

Re: coilovers

Postby ACourtney » Tue Dec 13, 2016 9:14 pm

Jin wrote:regarding the front I did consider a setup very similar to that on the red car you have pictured when I first bought the car 3 years ago, but I discounted it on the basis that I didn't think 4 8mm bolts would be enough to take the upward load acting on the spring nor did I think the remaining half of the Hydragas clamp (attached to the subframe) would be strong enough to resist upward and inevitably sideways load in use.
:)


Hi Justin,

An M8 HTS 8.8 bolt has an allowable shear load of 1937kg for single shear across the thread, according to the rules of Eurocode 3. That will have a safety margin of around 25%, so it would be okay up to around 2400kg and if you made sure that the shear plane was across the shank and not the thread (Eurocode assumes the worst!) you gain another 17-18%. Even discounting that, four M8 HTS 8.8 bolts would be good for nearly eight tonnes, or around ten times the weight of the car. Note that I have referred to HTS 8.8 bolts. All decent bolts have their strength range stamped on their heads and 8.8 are the optimum for this sort of application. Whilst 10.9 and 12.9 have higher ultimate strengths, their impact energies and elongation at failure are lower. In other words they are more brittle and are more likely to snap in a shock load, or impact.

If the bracket is designed sensibly with the centreline of the coil-over more in line with the axis of the hydragas unit the loading on the turret will be more or less the same. Okay to achieve that completely you would need a flange on the back that located under the lip that held the hydragas unit, but essentially you would not be introducing any large bending loads that required any extra reinforcement.

Regards,

Alistair
User avatar
ACourtney
 
Posts: 488
Joined: Thu Dec 04, 2008 12:22 pm
Location: Oxford

Re: coilovers

Postby Geoff Butcher » Tue Dec 13, 2016 9:22 pm

The Aussie front kit cost me just under £600 including carriage and customs/VAT but without dampers
Geoff
User avatar
Geoff Butcher
 
Posts: 751
Joined: Fri Dec 05, 2008 9:10 pm
Location: Braintree

Re: coilovers

Postby Jin » Tue Dec 13, 2016 11:17 pm

thanks guys, much appreciated

I'm pretty sure this is the route I am going to pursue
are the rear coilover brackets still available for the mk3s?
ill even happily buy an old pair if somebody has some?

thanks in advance
https://easywider.co.uk/ universal flexible wheel arch extensions
Jin
 
Posts: 454
Joined: Fri Aug 01, 2014 10:33 pm

Next

Return to Technical and Problems

Who is online

Users browsing this forum: Google [Bot] and 7 guests