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A new build - mx5/Sierra rear end question.
Mudchute - 24/4/15 at 02:53 PM

Hi everyone,

I've been given permission to commence a Haynes locost build so I've been planning which of the variations to go for.

I want to use an mx5 and go for an sdv build but the rear end is bothering me. I've seen the excellent Saturn cars mx5 guide and will follow that however I don't want to use the mx5 rear dampers which I believe it does. For adjustability I'd rather use a damper the same as the front but can't find a design that allows this.

Can anyone help or point me in the correct direction?

Thank you guys

Gavin


Slimy38 - 24/4/15 at 03:14 PM

Nope, no MX5 dampers used in any MX5 design I've seen, they're standard seven type dampers. It uses the upright from the mx5, and needs a short top wishbone to accommodate the rear diff arms, but that's about it for customization?


mikeb - 24/4/15 at 03:29 PM

mounting the diff seems to be the biggest headache.


Mudchute - 24/4/15 at 03:33 PM

Ah, I've not been able to find a pic of an assembled Saturn/Haynes rear suspension assembly hence the confusion.

Is the short top arm a problem? Does it compromise the suspension action/geometry in any way?


ianhurley20 - 24/4/15 at 03:48 PM

One compromise which is the way I have built mine is a standard Haynes using Sierra rear end with Mazda engine box and other bits.


Mudchute - 24/4/15 at 03:51 PM

Were you able to retain the Mazda rear hub or brakes?


garyt - 24/4/15 at 05:22 PM

Hi. I have used the saturn plans for my build. If you look thru my photo archive you can see how the mx5 diff is used fitted. If you look for the talon build it uses a diffcover to fo away with the mx5 diff arms and as such the 2 are very fifferent. My build uses the mx5 uprights hubs brakes etc there are a few anomalies to be aware of. The shorter rear upper wishbone doesnt appear to effect anything . I had craig at plazcut (no connection) to do the plates for me and he now lists them. If you need any clarification on anything dont be afraid to ask and ill do my best to answer. Measure. Take a picture.
Feel free to browse my photo archive or see my buil thread its in the chassis section..... lol... maybe the mods can move it to the haynes section
Anyway welcome and good luck
Gary


garyt - 24/4/15 at 06:03 PM

here is a pic of the diff mounted

[img] Description
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Mudchute - 24/4/15 at 06:12 PM

Thanks Gary, it's useful to see the Saturn rear built up.

Choices, the tmxr kit is tempting. It'll certainly make life easier. I'll go have a think and report back.


Stot - 24/4/15 at 06:21 PM

The diff issue is mainly the mounting of the nose. The Saturn plans suggest a rubber mounting but that soon gets torn up in use as when you apply torque to the diff the nose wants to pull up, especially if you are using rubber wing bushes too. A few of us have solid mounted the whole diff now and touch wood no problems on mine so far, I'm putting ~200hp through a 1.6 diff. Its also why Talon is offering his replacement diff casing which solid mounts like the Sierra build. mounted mine with solid bushes and solid nose mount. Proper sized bolts were used eventually..







Only thing I would say is that I can 'feel' the diff when theres engine braking taking place but I don't think it would be any more or less than a Sierra build which is solid mounted also.

Cheers
Stot

[Edited on 24/4/15 by Stot]


Slimy38 - 24/4/15 at 06:39 PM

I went for Talon's cover, it mounts really well. And it means you can revert to the standard Sierra sized wishbones and put the geometry back to the original. Not that I'm saying the short arms are bad, but I have to be honest it didn't sit well with me. Combine that with what Stot said about mounting the standard diff and the solution from Talon just makes a whole lot of sense.

This is the cover as it arrived, and fitted in place of the standard cover;




These are the mounting lugs, they're actually the Sierra diff plates chopped up!! (waste not, want not)



Painted and fitted;



And another view. Note the cage, it's from the original Haynes design so the wishbones will have the same bracket points;



[Edited on 24/4/15 by Slimy38]


ianhurley20 - 24/4/15 at 07:56 PM

quote:
Originally posted by Mudchute
Were you able to retain the Mazda rear hub or brakes?


I didn't try to and used standard hubs and sierra drums. If I were doing it all again it would be Phils TMXR design with his diff cover.
I hope Phil is okay because he has a number of domestic and health issues at the moment that may make that choice difficult.


Mudchute - 24/4/15 at 08:44 PM

The tmxr setup looks very appealing. I think I'm gonna go with that.

I'm picking up an 8x4 table Monday, a 'boardroom meeting' table that's very heavy and very sid not to mention completely flat. That'll be the build table!

Hopefully I win an auction on a welder soon as well. The ball is rolling!


garyt - 25/4/15 at 06:17 AM

Thats it started now then . Keep it going and remember we are all here as n when required there is a huge wealth of knolage on here for advice and inspirarion. Good luck Gary


garyt - 25/4/15 at 06:24 AM

As mentioned above Phil at talon is a great guy and has a vary good reputation . I would contact him sooner rather than later to get a lead time / order your chassis / pack etc. As im not sure how long you would have to wait as they are not "on the shelf" sort o speak
Gary


Mudchute - 25/4/15 at 07:16 AM

Thanks Gary,

I'm very excited about the build, patience will be my enemy however money will keep that in check!

I've been thinking more about chassis options. As I want to do as much for myself as possible I'd like to cut and chamfer the chassis tubes myself (I have suitable tooling and a milling machine to generate accurate angles) so I've been thinking I could copy the saturn plans for the front end and mx5 specific fittings (steering column etc) but build a book rear end and mount the diff with the Talon diff cover. Talon also make suspension arms to fit mx5 uprights into a standard chassis which if used should tie the whole lot together.

Does this ound plausible?


steve-hv8 - 25/4/15 at 07:31 AM

im following this post with interest as im still thinking about what to do
im going to get in touch with talon and see what lead times are


Slimy38 - 25/4/15 at 08:00 AM

quote:
Originally posted by Mudchute
Thanks Gary,

I'm very excited about the build, patience will be my enemy however money will keep that in check!

I've been thinking more about chassis options. As I want to do as much for myself as possible I'd like to cut and chamfer the chassis tubes myself (I have suitable tooling and a milling machine to generate accurate angles) so I've been thinking I could copy the saturn plans for the front end and mx5 specific fittings (steering column etc) but build a book rear end and mount the diff with the Talon diff cover. Talon also make suspension arms to fit mx5 uprights into a standard chassis which if used should tie the whole lot together.

Does this ound plausible?


That's pretty much what I did, but I had to be 'creative' with the rear wishbones. Partly because at the time there were no MX5 upright to Haynes chassis options, but partly because I want to keep costs down. You'll find that because a lot of work goes into the wishbones, they can end up pretty pricey ready made. There's nothing wrong with that but I have more time than money. It took me a good 30+ hours to do my wishbones, and it saved me a couple of hundred pounds.


Mudchute - 25/4/15 at 09:09 AM

Thats good to know, thank you and gives me confidence to attempt more myself.

The wishbones a far off so hopefully between now and then I could establish the correct dimensions. I'm happy to manufacture them myself but they obviously need to be bang on.


ctwv50 - 25/4/15 at 10:27 AM

I've poly mounted my diff all round, two volvo engine mounts top and bottom secure the nose and seems to be holding up well but I've not put any real miles on it as yet just hard launches with fat sticky tyres.

I'll take some pictures when I change the diff sometime this summer.

BUT, if I were to attempt a similar build, which is unlikely, I might try to replicate the westfield rear end but again poly mount the diff ,if it proves problem free. It'd be a lot of work and you'd have a lot of knock on changes to the standard car but that would be the fun bit. It'd maybe add a year to the build. lol!




Mudchute - 25/4/15 at 10:43 AM

Thats an excellent picture, thank you.

I did have fleeting thoughts about mounting the diff with bushes somehow. It makes a lot of sense and should give the diff/prop/gearbox a slightly easier time dependent on how well its done.

I straining a the leash to get cracking on this. Tomorrow is going to drag, I need to pick up this table and start mapping it out. I do hope I win the welder auction too...


ctwv50 - 25/4/15 at 11:03 AM

Here are some bad images, the first is the first mock up with some standard Volvo engine mounts, the other two are the top and bottom mounts with poly bushes in and painted. I made these out of metal found in a fabricators scrap bin, a disposable welding gas bottle and any other bits and pieces I had lying around, hence the rough undesigned look. I intend to redo them using specced material when I change the differential.






Mudchute - 25/4/15 at 11:29 AM

They're substantial and must work well.

I was wondering. The big ally 'I beam' mount cast into the diff cover. What if one were to chop that right down, leaving something thats slightly wider than the diff itself then machine two holes going front to rear of whats left and then fitting a poly bush through them which then mounts to a chassis bracket?

If that makes sense!


ctwv50 - 25/4/15 at 11:48 AM

quote:
Originally posted by Mudchute
They're substantial and must work well.

I was wondering. The big ally 'I beam' mount cast into the diff cover. What if one were to chop that right down, leaving something thats slightly wider than the diff itself then machine two holes going front to rear of whats left and then fitting a poly bush through them which then mounts to a chassis bracket?

If that makes sense!


GBS Zero do a similiar thing but solid mounted.

http://zachsgbszero.blogspot.co.uk/2013/04/fuel-system-diff-panels-bit-of.html

If it was done in such a way so you could resist the twisting motion then yes go for it.


ctwv50 - 25/4/15 at 12:00 PM

Actually, having recently taken an mx5 diff apart it occurred to me that you could use slightly longer high strength case bolts and use thick steel plate shaped and drilled to fit around the cast steel nose to create any kind of mount to any kind of frame or build allowing you to be able to completely remove the arms from the ali case. Kind of like talons diff case but without the cost.



[Edited on 25/4/15 by ctwv50]


Slimy38 - 25/4/15 at 05:25 PM

I think I'd prefer the longer diff casing bolts to be honest. The only thing to consider is that they're not terribly big and very close to the edge. Comparing them to the large bolts that fit the arms (and the leverage of the arms themselves) I don't know whether it would be enough? If you could do it from one plate (5mm maybe) then I'd be happier.

Putting bolts through the aluminium webbing of the case just seems like a bad idea. With the diff casing prone to cracking in standard fit, I'd worry about the load through a much weaker part. Then again, there's no mention on the blog that he had to do anything about it so I guess it works.

I'm no engineer though, that's just my humble opinion


Mudchute - 25/4/15 at 05:45 PM

I think the torque of the ending will put a lot of strain through those long castings and try and twist the diff out of them?

I lost the ebay auction. I think a trip to machine mart is on the cards. There's no decent used welders for quite some distance.


dubzter - 25/4/15 at 08:18 PM

quote:
Originally posted by Slimy38
I went for Talon's cover, it mounts really well. And it means you can revert to the standard Sierra sized wishbones and put the geometry back to the original. Not that I'm saying the short arms are bad, but I have to be honest it didn't sit well with me. Combine that with what Stot said about mounting the standard diff and the solution from Talon just makes a whole lot of sense.

This is the cover as it arrived, and fitted in place of the standard cover;




These are the mounting lugs, they're actually the Sierra diff plates chopped up!! (waste not, want not)



Painted and fitted;



And another view. Note the cage, it's from the original Haynes design so the wishbones will have the same bracket points;



[Edited on 24/4/15 by Slimy38]


I'd be really interested to hear how you got on transferring the diff into the tmxr cover? What's involved and what spanner rating would you give the job?


Slimy38 - 25/4/15 at 10:25 PM

It's really easy to be honest, I'd give it a 1 spanner rating at most. There were a few things to note;

1. I removed the oil seals and reused them, but Phil actually said not to. I mainly did it to see if I could get away with it as they're £30 each! If it leaks it's not an issue to replace them after.
2. The cover inside edge was too tight on the diff, I had to just skim the edge with a file to get it to a point where I could use a rubber mallet.
3. DON'T use the bolts to draw the cover on, they will strip. Phil warned me not to and I didn't want to test the theory.
4. The vent, the filler plug and drain plug need to be transferred, so don't throw the casing away as soon as it comes off.


dubzter - 26/4/15 at 04:07 PM

quote:
Originally posted by Slimy38
It's really easy to be honest, I'd give it a 1 spanner rating at most. There were a few things to note;

1. I removed the oil seals and reused them, but Phil actually said not to. I mainly did it to see if I could get away with it as they're £30 each! If it leaks it's not an issue to replace them after.
2. The cover inside edge was too tight on the diff, I had to just skim the edge with a file to get it to a point where I could use a rubber mallet.
3. DON'T use the bolts to draw the cover on, they will strip. Phil warned me not to and I didn't want to test the theory.
4. The vent, the filler plug and drain plug need to be transferred, so don't throw the casing away as soon as it comes off.


Sounds straight forward enough, cheers for that.


PorkChop - 29/4/15 at 09:12 PM

quote:
Originally posted by Slimy38
1. I removed the oil seals and reused them, but Phil actually said not to. I mainly did it to see if I could get away with it as they're £30 each! If it leaks it's not an issue to replace them after.



The pre 93 ones can be had for cheaper than £30 a side, and the later (93-05) ones are less than £10 a side.

[Edited on 29/4/15 by PorkChop]


Slimy38 - 29/4/15 at 09:49 PM

quote:
Originally posted by PorkChop
quote:
Originally posted by Slimy38
1. I removed the oil seals and reused them, but Phil actually said not to. I mainly did it to see if I could get away with it as they're £30 each! If it leaks it's not an issue to replace them after.



The pre 93 ones can be had for cheaper than £30 a side, and the later (93-05) ones are less than £10 a side.

[Edited on 29/4/15 by PorkChop]


Ah, looks like the price has dropped since I last checked, yes the ones I would need are now £20 each + postage. (it's a 92 diff).

And yes, I did notice the later ones are a good deal cheaper!


Mudchute - 3/5/15 at 01:20 PM

Hey guys,

I've reached the next decision to make. I'm going ahead with using mx5 running gear but I ultimately would like to fit a duratec using a Mazda gearbox.

Overall time will be limited over the next couple of years so I would like to build it with a duratec from the start however I understand this'll almost definitely mean a Q plate, is that correct?


Slimy38 - 3/5/15 at 03:31 PM

If you build it with running gear from one car and engine from another, it will get a Q. If you want an age related plate, then use all the Mazda and do an engine transplant later.


Mudchute - 3/5/15 at 04:03 PM

I need to decide if I want an age related plate or not then...


ianhurley20 - 3/5/15 at 05:29 PM

For an age related plate you have to have two 'significant' parts from the donor car, you don't have to have all of them so Engine gearbox wiring loom is enough
Ian


steve-hv8 - 5/5/15 at 10:56 PM

so with the diff cover from talon can you retain the mx5 uprights with the standard sierra wishbones?


Talon Motorsport - 8/5/15 at 08:07 AM

You use the standard Roadster chassis with the suspension and damper brackets as per the book. The upright needs moving forward by 9mm to get the the bottom of a standard 34mm wide coilover to line up next it, this means using a fixed/solid off set lower wishbone and twin camber adjusters in the top wishbones with a bolt running through the coilover, top mount with an adjuster either side of them.

[Edited on 8/5/15 by Talon Motorsport]


steve-hv8 - 9/5/15 at 12:39 PM

do you supply the wishbones that would allow the diff cover to be used in a sierra chassis with mx5 uprights?

quote:
Originally posted by Talon Motorsport
You use the standard Roadster chassis with the suspension and damper brackets as per the book. The upright needs moving forward by 9mm to get the the bottom of a standard 34mm wide coilover to line up next it, this means using a fixed/solid off set lower wishbone and twin camber adjusters in the top wishbones with a bolt running through the coilover, top mount with an adjuster either side of them.

[Edited on 8/5/15 by Talon Motorsport]


Mudchute - 9/5/15 at 06:56 PM

And would you supply them as a kit?