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

[vmax1974]

What size and grade bolts have people used to hang the diff

Need to know before going and ordering my nut and bolt set

Using the saturn plans and want to get the diff mocked up this week

[Talonmotorsport]

Can I ask how you are planning to mount the diff?

[Davidbolam]

I will pop some photos up of my modified mount in the next few days

I have made sure it won't budge

David

[vmax1974]

Originally Posted by Talonmotorsport

Can I ask how you are planning to mount the diff?

Same way as the donor bolt through the mounts then rigidly mount the doughnut rubber to a plate welded to the diff cage

Then I was thinking about solid mounting the diff nose to take the place of the ppf on the donor was also going to work out a shield to protect me should the diff break

[Talonmotorsport]

Have you thought about making a bracket out of some 5mm plate that looks like this at all? Remove all the blocks/brackets around the nose fit some 3/4-19mm round stock with 12mm through holes in the 18-19mm holes in the nose and use M12 bolts.

[vmax1974]

That was the kind of thing I had in mind

Was worried about vibration from the diff till I remembered the book build diff is hard mounted to the chassis

[PorkChop]

Originally Posted by vmax1974

What size and grade bolts have people used to hang the diff

Need to know before going and ordering my nut and bolt set

Using the saturn plans and want to get the diff mocked up this week

Dunno about size, but you'll want 8.8 grade at the very least.

[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.