MX5 Donor, Using as a Donor/problems/solutions/advice Info

[Johno]

Ohh the dreaded diff problem....
As David said Nathan (NTS) made the mistake of not bolting the diff up correctly.
There seems to be many options as to how to mount this correctly, just check out the Locost USA forums for a starter.
Even the main kit car 7 suppliers have their unique way of installing the diff so there is no one hard rule.
I believe the main concern is containing the torque on the nose of the diff.
Have a look at all the options (check out Keith Tanners problem with this) and see what you can come up with?
I believe Skov is the nearest to getting his car on the road and seems to have the nose of the diff under control with rubber mounts.
Some ppl go for the solid mount option but this may lead to fatigue problems in the future....

Just my observations but I'm sure there are more people out there more knowledgeable than me.

[CTWV50]

Anyone need any bodywork?

http://www.haynes.co.uk/forums/showthread.php?t=12782

[Stot]

Hi,

I'm getting some questions about my solid diff mounts I made.



Skov and PorkChop asked me a while ago If I could make them some when I did mine to share the cost of the aluminium but I cant make them for others I'm afraid. I'm sure Phil or someone could make them up if asked nicely.

The bushes slip fit as the clamping action will be providing the support hence the thick lugs.



I made them from 3.5" stock which is the perfect size, I didnt even bother turning down the outside surface.

I chose 40mm and 20mm long because I was able to buy offcuts this size to save further on materials. It gives about a 10mm gap between the two halves when fitted so you can play with the individual lengths really as long as the lug parts are 12.5mm and you leave a gap so they can clamp on the diff ears when bolted up.

Biggest problem I had was getting the old bushes out! A 3 jaw puller makes the job easy and theres some guides on the MX5 forums. I didnt have one of those so used a hammer and chisel to bend the outer bush casing in a bit then pushed them out with a 12 ton press.

HTH

Cheers
Stot

[jason 82]

Thanks for popping up the dimensions stot. It must be really hard sharing one of your ideas. They are really appreciated.

[Stot]

Originally Posted by jason 82

It must be really hard sharing one of your ideas. They are really appreciated.

Not at all mate, I just didnt think to! Hope they help and one of the fabricators can pick them up.

I would have considered making them if

• I didnt have a full time job.
• I didnt have an app on Android, iOS and PC im trying to maintain in my spare time.
• I wasnt building a car in my spare time.
• I didnt have a wife (in my spare time)
• There wasnt already fabricators who could probably do with the business.

Cheers
Stot

[PorkChop]

And nicely done they are too Stot - thanks very much, I'm very pleased with them

[skov]

Very happy with mine too - thanks Stot!

Regarding the original bushes, mine came out fairly easily.
I started off by drilling a load of holes in the rubber then pushed the centre bush and most of the rubber out.
I then set to work on the outer metal bushes with a hammer and screwdriver.
The outer bushes are in two halfs and the trick is to bend one half inwards along the join.
As soon as the two halfs of the metal bush aren't touching the pressure holding them in is released and they pretty much just pop out

[PorkChop]

I've posted the SSC coilover specs a few times throughout the forum, but never on this thread...


Front

13" open 9" closed 1.9" ID dampers, with 350lb springs - 8" open x 1.9" ID.

Rear

12" open 8" closed 1.9" ID dampers, with 250lb springs - 7" open x 1.9" ID.

EDIT: AFAIK the front suspension mountings are the same spec as the book Sierra build, so the 13" +1" extension dampers should also fit the front.

[skov]

Originally Posted by PorkChop

I've posted the SSC coilover specs a few times throughout the forum, but never on this thread...


Front

13" open 9" closed 1.9" ID dampers, with 350lb springs - 8" open x 1.9" ID.

Rear

12" open 8" closed 1.9" ID dampers, with 250lb springs - 7" open x 1.9" ID.

EDIT: AFAIK the front suspension mountings are the same spec as the book Sierra build, so the 13" +1" extension dampers should also fit the front.

Those shock lengths are fine, but I wouldn't take the spring rates as gospel.

Nathen had started supplying 400lb springs for the front as he thought it rolled too much, which is what I ended up with.
From my experience that's a recipe for massive understeer. It also gives a horrible jolty ride on bumpy roads as the rear can't react fast enough to catch up with the front.
I'm not convinced Saturn's original values would be much better either.

Having done some calculations (albeit full of assumptions/guestimates/errors) I came to the conclusion that the rear needs to be around 100lbs harder than the front, and that 300 front / 400 rear would be a good starting point.

As a quick test I swapped mine over and put my 250lb springs on the front and my 400lb springs on the rear and went out for a drive.
Have to say it's transformed the car!
The ride is far more composed on bumpy roads, and I've got shed loads of front grip.
It's possibly gone a little too far the other way, as it's ever so slightly tail happy now. It is however nicely controllable and much more fun that way
I'll get some 300lb springs for the front and report back at somepoint.

[jason 82]

Cheers for that. Your help is really appreciated. It feels like my first drive is a million years away ! Can't wait to go and burn a little rubber.