Alfa GTV Raising front suspension

[Fylnn]

One for the front suspension geometry theorists.  I am running my GTV6 as a gravel rally car.  As such I need increased ride height and suspension travel, and also adequate droop to keep the front wheels in contact with the road.  At present I have about 150mm of clearance under the sumpguard, which seems to be enough, given the rough roads we sometimes use in Qld.  My problem now is that at maximum droop I am perilously close to the shock absorber fouling on the inside of the opening in the upper wishbone.  In fact on the left hand side I am sure it is. 

I have about 60mm of droop which seems like the bare minimum.  What stops me from getting more is the bump stops.  I have already cut them down a bit, but not as much as I would like since it was obvious that the shock absorbed was about to touch.  I am running Bilstein gas pressure which might be a little larger in diameter than some others but is what I need.  Only other mod to the front suspension is I have added 6mm plates behind the lower wishbones to strengthen the chassis rails.  That would have the effect of pushing the lower wishbone outwards and therefore the lower mounting point of the shock absorber. 

I have seen the drop spindles that people use to lower the front end.  Installed they space the ball joint about the wishbone.  But one thought that strikes me is to use a set of those without the spacer, or with a smaller spacer to return the wishbone to a more level position.  But then that changes the roll centre geometry.  I did some rough measurements and drew it up and it may not be too bad.  But I need to do it thoroughly.

So anyone out there with practical experience that might be able to suggest the likely outcome of this idea?  Failing that then plan B is to somehow modify the position of the Bilstein, not immediately obvious how, or attack the upper wishbone and somehow enlarge the opening.  Which is a bit fraught as well. 

Any thoughts anyone?

[scott.venables]

No firsthand knowledge but I have a shaky grasp on some theory!

You could create clearance in the upper control arm by adding spacers under the lower damper mount.  This will net you some extra droop if you're droop limited by the damper and not some thing else.  You will however need to add quite a bit under there to gain any significant room in the  upper control arm.  You could also massage the arm with a hammer for extra room or cut some out with a grinder.  I've seen photos or large amounts removed all around the inside to clear coil overs when the castor is increased, so I doubt you'd have any problem removing a little at the inner end of the hole. You could also make a plate to bolt to the lower control arm that moves the bottom of the damper outwards towards the wheel.

If you've got an early GTV shell I think you could probably remove entirely the factory bump stop sheet metal.  The later cars didn't have them and although I have never had a good look at one I don't think they would add much strength to the body. 

Dropped spindles are an interesting thing to bring up but I think you'd want shortened spindles wouldn't you?  I could be wrong but I would think roll centre would be less important or a dirt/gravel rally car because of reduced weight transfer.  I would pay just as much(maybe more) attention to the camber curve, making sure you don't lose or gain too much with bump/droop.  I think you might worsen the camber curve with shortened spindles because the upper control arm would be 'hanging down' at static ride height.  You couldn't be sure until you'd plotted it though.

Scott

[Beatle]

What are the competition rules regarding the suspension? 

I'm sure there are a few different manufacturers of fabricated (tubular) adjustable upper and lower Alfetta suspension arms and these may give you the damper clearance required, plus offer the opportunity of relocating the relative pickup position of the upright.

And if I understand what you've done, those 6mm strengthening plates are effectively the same as 6mm camber adjusting spacers, so the plates haven't really done anything worse than you'd get with similar camber adjusters.

[Duk]

Dropped spindles are an interesting thing to bring up but I think you'd want shortened spindles wouldn't you?  I could be wrong but I would think roll centre would be less important or a dirt/gravel rally car because of reduced weight transfer.  I would pay just as much(maybe more) attention to the camber curve, making sure you don't lose or gain too much with bump/droop.  I think you might worsen the camber curve with shortened spindles because the upper control arm would be 'hanging down' at static ride height.  You couldn't be sure until you'd plotted it though.

Scott

Scott has brought up an interesting point.
I think your best approach would be a 'raised spindle'. 1 where the bottom ball joint boss is cut off of the spindle and welded higher up on the spindle. The opposite would need to be done for the top ball joint boss, it would need to be raised (so you'd need 2 pairs of spindles to make 1 pair that you will use) or a strong , long shank top ball joint could be used. Keeping in mind that your car will need to use plenty of suspension travel, you'll need as much ball joint articulation as you can get so they don't bind and get damaged or snap.

[Fylnn]

Well yesterday I took it out to a track at a place called Hirstglen for a bit of a run.  There is a 3km track that the helpful farmer has cut on this property.  Road conditions were pretty nice, if maybe a little boggy in a couple of the creeks.  It was a great day, think the car is bedded down pretty well for its first full event on June 1.  120km or thereabouts of competitive.  The roads a meant to be a little bony after the recent prolonged heavy rains up here.  t 150mm I am really happy with the ride height now.  It is about 150mm under the sump guard, 30mm more than the last time I took it out.  Then it was very uncomfortable, bottoming out the whole time.  So now I have confidence in it and was able to push it as hard as I had talent to go.  The handling is progressive, the tail will come out but easy to catch and correct.  The only small thing I noticed is that when it unloads over a large hump it can drift a bit, like the wheels are leaving the ground.  So something I will have to keep in mind.  But for now I am not going to change anything until after the next event.  Then I might decide to chase some more droop and get back to this idea.

The day was a success, I had a ball.  There has been a long running problem with fluffing and cutting out.  It turned out to be something with the distributor.  I managed to source a hall effect one from a 75 from 105gta on this forum.  With that in place I got the Haltech retuned by Marty at STZ.  The engine was crisp and strong all day, and the assembled spectators all commented just how good the car sounds.  Well it is an Alfa V6 after all.  I also had just finished modifying the pedals to allow heel and toe so I can try and save the synchros in the transaxle that Richard Anderson at Avanti built.  It never baulked all day so that is a nice thing to use now.

All in all looking forward now to the rally at Gallangowan.  When I will consider what to do next.  Might do some calculations and try and assess what will happen to roll centre if I did put in some of Vin's long top spindles and see what it does.  The idea is to bolt straight to the top arm not space them up.

[Fylnn]

Well the car and I survived its first rally.  It was wet and slippery, wheel spin up hills in third gear was interesting.  I was just feeling my way in and managed to pick up a few seconds a kilometre on the second run through before it got darker and wetter and the fog came down.  From them on it was just driving to the finish.  So the Alfa made it all the way to the end of its first rally.

Now that monkey is off my back looking forward to getting out and doing it again.  Also looking forward to some further suspension development.  One feeling from myself and my experienced co-driver is that the front end if too stiff.  I am running 28mm torsion bars and granted it was pretty slippery but the front grip did not seem to be there.  So now looking to maybe soften it up a bit.  Going to maybe 25mm torsion bars.  Also looking to cut back the bump stop to get more droop.  Which would make the damper the bump stop in droop.  Which is what happens on the 75 I believe.  Question is, are the front dampers on the 75 any different to the GTV ones to accommodate being used as the bump stop when the suspension droops?

[Beatle]

Good to hear all went well.  You really need to get some headlight covers for her...........................