Possible new route to 5 stud front suspension

[Turbo-Brown]

Have moved this from my other long running thread as it probably warrants a thread all of its own.

I recently bought the front strut from an E90 in the hope of some Christmas miracle meaning it would have the right geometry to fit the E30.

It, of course, doesn't!

That's okay though, I wasn't really expecting it to, the the benefits of the E90 setup are that the whole hub and spindle can be unbolted and the strut just clamps to the knuckle.

So, today I started to compare E30 to E90.

[Turbo-Brown]

As a starter for ten, I clamped both struts to the bed of the milling machine. This puts the mounting face of both hubs on the same plane.

The good news is that the strut tops appear to be at the same height. This is just eyeballed so needs more careful measurement.

What it might mean is that just the mounting to the wishbone and track rod needs modifying.

[martauto]

Made this a sticky

Mart.

[Turbo-Brown]

Spent some time measuring today, like all things,takes longer than you think!

Made a high quality probe by gluing a ball bearing concentric with the mill collet holder.

Then used a combination of the probe and the clock to take measurements.

Popped some bearings in the taper openings of the track rod end, measuring these in X,Y and Z means I can plot the axis of the track rod. Need to find bigger balls for the wishbone though.

Next up is plotting all the points in CAD.

Lot of the measurements are offset by the diameter of the probe, hopefully I've got enough data to make a good start!

Might have to cut up an old wishbone so I can accurately position the centre of the joint.

[steve_k]

i'll be watching this with interest as there's a couple of e90's in a scrap yard i know.

[Turbo-Brown]

Of course, if this works, E90 front suspension prices will be multiplied by 10…!

[flybynite]

I've got a complete set of the E36 M3 bits if you need measurements or photographs for reference.

Still debating whether to throw it on the facelift to see if it drives as bad as everyone says it does

[Turbo-Brown]

Thanks for the offer, want to try to keep unsullied E30 geometry though!

Have spent a bit of time this evening CADding up what I measured earlier, will measure and CAD the E90 hub and relevant bit of upright tomorrow and overlay the two.

[Turbo-Brown]

Here's the post that kicked this all off:

Took a total punt on the front suspension leg from an E90 this week

The difficulty with converting to 5 stud appears to be that you either have to source super rare and expensive parts from an E30 M3, source nearly rare and still quite expensive parts from an E36 M3 that MUST be post 1996 or you're into sleeves to adapt the E30 spindles to accept E36 hubs.

Various people say the E36 route doesn't give great suspension geometry too.

I have looked at the sleeve route and even have a few sets made from about 10 years ago, but you end up with the hub hanging off the end of the spindle and it all looks a bit flimsy.

The difficulty in converting from one hub to another is that the spindles appear to be friction welded to the steering knuckle and are a funny diameter that doesn't match any off the shelf bearings, so you can't change the spindle and keep the knuckle, and there's little point making your own hub as you'd have to sleeve the bearings anyway.

Enter the E90!

The upright is aluminium and clamps the strut.

It's almost unthinkable that the geometry is a match for the E30, and the ball joints don't have a taper....and it's supposed to have two lower arms which react lateral and longitudinal forces respectively....but the struts are cheap!

Assuming the geometry isn't right, they have one great benefit: the spindle and hub now bolt onto the knuckle.

This means I can survey the E30 front struts, pivot points etc and make a new knuckle that gives perfect E30 geometry but accepts E90 hubs and struts.

Hooray!

[DanThe]

I noticed a post a few weeks ago which was going down a similar road using some Group A style arms,

I think both the E90 ball joints are larger than E30 from memory so an insert would be a good way to connect the hub to the wishbone, E46 track rod ends use a larger ball joint (may be the same size), combined with the rest of the track rod this can be bolted onto an E30/E36/E46 rack

[flybynite]

Thanks for the offer, want to try to keep unsullied E30 geometry though!

No problem

If you are sticking to E30 geometry, was just wondering what wheels you had in mind as I don't know of many 5-stud with E30 offset. Were you planning to use E30 M3 wheels ?

Most of the 5-stud conversions make use of +20 ish on the offset to cater for the bulk of 5x120 wheels being around ET40

[Turbo-Brown]

Ah has, great minds think alike!

They've got E90 M3 knuckles there though which cost M3 money! :LOL:

They must have moved the wishbone ball joint towards the centre of the car by a good amount to avoid insane amounts of camber with the setup pictured.

Would love to see the rest of that thread.

The newer ball joints don't have a taper at all, just a kind of hemispherical seat. My guess is to avoid busting the aluminium upright when someone over tightens the ball joint nut.

Currently got E39 Comp 42 wheels which are ET20 Vs ET24 for the 15" E30 wheels so not a million miles out.

Think the E36 and E46 had quite high offsets so wonder if that drives people's wheel choices.

[Turbo-Brown]

So using the mill as a CMM is a new game to me, and like all new games it takes a bit of practice!

Decided to make the fixturing for the strut more rigid and take all the measurements again today.

Also made a pin with a sphere on it so I could find the centre of the wishbone ball joint axis.

Took lots more measurements today too in the hope of pinning down the geometry more accurately. Ended up with 64 coordinates to plot in the CAD.

Overlaying yesterday's and today's models, some key things are reassuringly similar, but one is miles out.

The top of the strut where is would affect camber is about 0.8mm out, which equates to about 0.1degrees of camber.

Fore and aft it's about 9mm out but yesterday's measurements didn't account for that very well.

The track rod lines up to about 0.2 which isn't too terrible.

However, the wishbone is miles out.
Yesterday, I just eyeballed that measurement whereas today I made a datum to measure to so hopefully that's the smoking gun!

Grey is yesterday's model, white is today's.

Plan for tomorrow is to double check the wishbone setout then put the E90 strut on the machine and probe that followed by CAD and overlay.

Plan A is to investigate whether the bottom of the E90 upright can be machined off and an adaptor which replicates the E30 geometry be bolted on the back, hopefully using the hub bolts.

Plan B is entirely new uprights!

[Turbo-Brown]

Solved the mystery of the out of place mounts, had accidentally offset them twice, glad I checked!

Probed the E90 strut today.

And built the CAD model to overlay with the E30 strut.

Good news is that the camber looks like it should be about spot on! The tops of the struts align almost perfectly! White is E30 and transparent is E90.

The ride height is about 7mm higher using the E90 strut, but that's compared to the E30 with a 40mm drop so should be okay I think.

The less good news is that I can't use F30 discs as they're set back too far. Shame as the 340mm ones would have been ideal!

Next closest is the E46 330d with 325mm discs. Much shallower, but still clash with the track rod unfortunately.

Made a crude wheel to see where that sits, would have just cleared the E30 strut, has miles of clearance to the E90.

Going to look at using two piece discs and hats to get around the disc and track rod problem next.

[martauto]

Nice work Alex, is it possible to use spacers inside the discs ?

Mart.

[Turbo-Brown]

I'm trying to avoid it being too much of a bricolage, looking at two piece discs at the moment, just need to make sure I can get the calipers behind the wheel though.

Job for tomorrow that!

[martauto]

I'm trying to avoid it being too much of a bricolage, looking at two piece discs at the moment, just need to make sure I can get the calipers behind the wheel though.

Job for tomorrow that!

Understood Alex, just throwing bits of stuff around as this could be a very useful thing for loads of guy`s.
Dont forget to copyright it.lol

Mart.

[Turbo-Brown]

More ideas the better!

Think if two piece discs work then this could be a winner!

[Tzantushka]

Made a high quality probe by gluing a ball bearing concentric with the mill collet holder.
...
Then used a combination of the probe and the clock to take measurements.
...

Old school fitting & machining - I like it!

Pfffft - who needs these fancy Coordinate Measuring Machines...

[DanThe]

What is the difference between the wishbone ball joint centres? If you use this as a reference rather than the hub faces the difference can be easily made up with a wheel spacer, that is of course if the track rod ball joint is still in an acceptable position

[Turbo-Brown]

Hi Dan,

Reason I've referenced everything to the hub face and axis is that I can faithfully replicate the E30 geometry that way.

Basically, I don't want to move any of the mounts with respect to the hub so the strut top, wishbone and track rod end all ideally want to stay where they are.

[Turbo-Brown]

So did lots more measurements today, more basic tape measure and Vernier stuff to verify the CAD models and see how to fit stuff up.

Also trawled the internet for other cars with 5x120pcds, decent sized discs and the right kind of offsets....

Mini Paceman (whatever one of those is!) to the rescue!

Has 307mm discs and pulls the disc about 8mm away from the track rod end.

Turns out my model for the E46 disc is a mm or two out as in reality it doesn't clash.

Remembered how much I love these wheels too!
Excuse the crap model, I mapped out the back of the spokes to see if the calipers fit. Might need a 2mm. Spacer possibly.

[Turbo-Brown]

Lots of CAD work today.

Whilst the Mini brake discs do appear to fit, they're really heavy at almost 8kg so have decided to go with Wilwood discs to match the calipers.

The Wilwood discs are about 4kg and my bells are 600g so big weight savings to be had!

These discs are about 310mm diameter and about 20mm thick which means I don't need any spacers for the wheel now.

Discs are about £40 each and material to make the bells is less than £35 for the pair so comparable costs to the Mini discs overall which is a bonus.

Had a stab at the adapters for the uprights, will do some FEA on them, but I suspect something like En24T or S275 will be more than up to the task. Will certainly be able to optimise the design for weight, it's around 1500g at the moment.

Red thing is the adapter.

[martauto]

Looking very cool Alex !!
Do you plan to make castings for the adaptors or machine from billet ?
For the tapered holes , will you mill these out using the cnc ? I`ve done one and two off`s in the past with a very fine peck and they were spot on, didnt take too long either.

Mart.

[Turbo-Brown]

I wouldn't trust my welding or casting for such a critical component!

Looks like I can make from stock 200x200x24 angle, so S275 grade which should be plenty strong enough!

Minimal waste too as my adapter is L shaped.

My mill isn't backlash free enough to make the tapers sadly, I'll have to measure the taper and either make or buy a reamer. Will step drill or interpolate to clear most of the material then ream to size.

[DanThe]

The disc to ball joint clearance is always a pain in the arse when doing brake upgrades, the amount of movement in the hub under load is quite unbelievable!

A 20mm thick rotor is what id expect to see on a 3 cylinder fiesta BTW is it a typo?

[Turbo-Brown]

Tis a bit skinny, it's a Wilwood UL32 disc which measures 12.19" x 0.81".

So long as it can pump air through itself, braking from speed will be fine though

[martauto]

I take it thats a grade of stainless ? Are we looking at 316 or there abouts ?
I know this is a bit /lot nerdy, but will you use a tooling ball for your central datum so everything comes off one singluar point no matter what angles you have to adopt ?
Having cad makes the calcs sooooooo much easier as well lol.
(hope I`m not telling my granny how to suck eggs )

Mart.

[Dlb26]

S275 is a plate grade of mild steel, surely you are better spending a bit more on something better and less likely to rust?

[martauto]

S275 is a plate grade of mild steel, surely you are better spending a bit more on something better and less likely to rust?

Thanks for that mate !!
I think Dan has a great point about flex/stressing but it`s about what is availiable from stock and stainless is difficult to find in this section for such a small amount.
17-4 ph is fantastic for this but once again ............................
I will keep my eyes open for a "piece of something " for you Alex.

Mart.

[Dlb26]

The small amount is definitely an issue, a lot of stock holders only want to sell you a full length because they can end up sitting on the remainder of the cut piece for a long time. There is a company in Scunthorpe and Peterborough that will cut no matter how small for trade accounts, not sure about public though. They are Locate supplies and specialise in non ferrous products. What about Metals4u etc? I have no experience of them.

[Turbo-Brown]

The great thing about S275 is it's available in a nice angle profile which minimises the machining I've to do.

My machine isn't all that rigid which had the effect of rinsing through cutters on steel. Really need to make a brace for the column, it's so bloody weedy compared to the rest of the machine!

Absolutely not teaching me to suck eggs, Mart!
I'm an enthusiastic amateur machinist, but I've got relatively little experience on the mill, most of my machining over the last 25 years had been on the lathe!

I have a go with a ball for the datum, funny enough I used steel balls to find the centre of the holes in the E30 struts, used the clock to find their centre in X and Y then clocked to the top to find Z.

[Turbo-Brown]

Back to materials, the S275 is fine as long as I get it zinc passivated.

It's good and strong too with a yield of 275MPa.
For those who don't know what that means, the yield strength of a material is when it will bend permanently. If you take a coil spring from a biro and gently stretch it, then let go, it returns to the length it was. However,if you reeeeerally pull, you feel the material sort of give up as it yields, and now when you let go, the spring is permanently stretched.

So 275MPa means you can apply a force of 275Newtons per square millimetre before it yields.

Putting that in weight terms, that's a load of about 28kg per square mm.

So for a 10mm X 10mm (1cm X 1cm) bar, you could apply a tensile load of 2.8tonnes before the material yields.

[Turbo-Brown]

Would love to use a bit of 17-4ph, heat treatment is pricey though, although we use a lot of it at work for shafts and it is reasonably stainless. Not sure how it copes with stress corrosion cracking though, and those ball joints might make excellent crevices!

[Turbo-Brown]

Metals4u have a fantastic business model, they charge SO much for material!

Hoping I can get one of our suppliers at work to help me out with an offcut if angle. Other thing about S275 is it's cheap!