Rear suspension - Toyota conversion...

[bazzbazz]

The factory Alfa bushes are quite soft, especially the front arm bushes. If one were reluctant to do the camry/corolla mod (which is a reasonable amount of work) a set of rear arm bushes installed in the front arms would help.

What about Poly-Bushes?

[johnl]

Not having tried poly bushes in this specific application, I would assume they would be a significant improvement on the stock rubber. Poly bushes can have their issues though. For a road car I would usually prefer to use very stiff rubber bushes over poly bushes, but such things are not always possible to find. It is often possble to adapt something, e.g. I've fitted very stiff 'silentbloc' style rubber spring shackle bushes (from a Land Rover onto a Honda Accord) using machined sleeves.

The 'Toyota conversion' also gets rid of the Alfa arms themselves, which are worryingly flimsy. Sans data I don't really know if the rather minimal 147 arms cause any issues with arm flexure (bowing under load), but it's not inconcievable. The Toyota arms use fairly robust tubes, far more 'reassuring' than the Alfa items (which are thin stamped sheet metal of 'U' section, not even 'boxed' anywhere along their length...).

Regards,
John.

[johnl]

I've installed the rear arms and performed the equal length mod as well.

The handling has been transformed, as John has described -

DV,
did you fit the GTA ARB as well? If yes then I would expect much of your 'transformation' will be due to this, as well as the Toyota bits. The thicker ARB and the 'Toyota Conversion' will both have very significant but somewhat different affects. 

Regards,
John.

[johnl]

DV,
re your 17mm GTA ARB. It will be a massive improvement on the stock 14mm bar, but, my custom bar is quite a bit thicker (20mm) and stiffer, and I still don't think it is too stiff.

If you wished it would be fairly easy (I assume) to weld plates to each end of the GTA bar, into which you could drill alternative drop link holes (which of course will allow effective stiffness change depending on which holes are used). The welding won't adversely affect the steel (i.e. heat treatment, if the bar actually has any, which it may well not) in a way that will affect it's real world performance. ARBs are only lightly loaded at the ends of the bar and a plate welded onto the ends will be strong enough (joint design and weld quality requirements still applying of course).

Regards,
John.

[johnl]

DV,
of course you'll be aware that due to the infinitely adjustable length, the Camry / Corolla hybrid control arms now give you some scope for adjusting not only rear toe but also rear camber (by changing the length of both arms on a side to the same degree). Changing the lengths by 1cm makes close to a 1° camber change. Of course this will also affect rear track width (the affect of which will be...?). When lengthening an arm it must be kept in mind just how much thread is still left inside the adjuster tube...

Re things suspension engineers do to encourage understeer; negative rear camber, more than the front camber. Reducing rear camber, in theory, should decrease understeer by reducing rear camber thrust of the outside wheel (it's the outside tyre that is much more important here than the inside tyre, since weight transfer substantially unloads the inside tyre). I have my rear camber set to very near zero (about 0.1° to 0.2° negative).

Seems to work OK, my car is fairly neutral in corners, but with so many changes I have made it is hard to quantify (more like guesstimate with the arseometer) the affect of any single thing.  I also don't use a lot of camber in the front end, about 0.5° negative.

Regards,
John.

[Divano Veloce]

Hi John,

my initial impressions of the camry/corolla arm mod were with the 14mm standard ARB - changed the car from disappointing to fun to drive - best $60 I've spent on a car. I fitted the GTA bar last night and test drove it this afternoon expecting another quantum leap in handling. Alas no... I suspect that my string line wheel alignment is not quite perfect and with the GTA bar the rear end seems to dart about with weight transfer.... This was hardly noticeable with the 14mm bar. It will get aligned this week. John, what toe settings do you use front and rear with your setup?

I have the same idea about adding some extra holes in the GTA ARB to give increased stiffness. It would be easy enough to do.

Thanks again

[johnl]

DV,
It might (?) just be that you need to get used to the substantial increase in rear roll stiffness, it tends to make the handling a bit more 'lively'.

My rear alignment; near zero camber, about 3 to 4mm of toe-in. Front alignment, about 0.5° negative camber, also about 3 to 4mm of toe-in. How confident are you in your stringlining technique?

With every car that I've spent much effort experimenting with different alignment settings, I always seem to end up with a bit of toe-in front and rear. I find toe-out in the front or rear just makes the steering and handling feel a bit 'loose' (not in the American sense). A bit of toe-in seems to 'tighten up' the steering and handling, at the same time improving directional stability, but without the loss of turn-in response that seems to be the generally accepted / expected result of toe-in. My experience is the opposite to this, a bit of toe-in improves turn-in, and I'm at a loss as to why I seem to be the only person to find this to be so...

Regards,
John.

[Divano Veloce]

The factory Alfa bushes are quite soft, especially the front arm bushes. If one were reluctant to do the camry/corolla mod (which is a reasonable amount of work) a set of rear arm bushes installed in the front arms would help.

What about Poly-Bushes?

Poly bushes will increase peak compressive force in what are very slender arms. Also they're not cheap. The camry/corolla arms cost $60 in materials and about 10 hours labor (but there's joy in doing...)

[Divano Veloce]

DV,
It might (?) just be that you need to get used to the substantial increase in rear roll stiffness, it tends to make the handling a bit more 'lively'.

Regards,
John.

The car is very pointy.... the steering is way too sensitive and overassisted.... This is more apparent with the GTA rear ARB.

Wheel alignment is booked for this Thursday.

[johnl]

The car is very pointy.... the steering is way too sensitive and overassisted.... This is more apparent with the GTA rear ARB.

Strange. When I fitted the stiffer rear ARB in my car, the seering became a bit 'pointier', more sensitive and responsive (all good), but felt a bit less over-assisted (i.e. a little bit heavier, subjectively, also good).

I dare say you haven't yet stringlined the rear alignment, but what do you think your current front end alignment settings are?

What tyres and pressures are you using? Is anything else in the suspension non stock? Are all the bushes etc. in good condition?

My car, I also have the B6 Bilsteins on the front, as well as a GTA front ARB, a homemade upper strut brace, and a homemade lateral subframe brace (runs under the engine).

Wheel alignment is booked for this Thursday.

Of course your front camber is more or less what it is (dependant on ride height, mostly). Adjustment is possible by slotting the chassis holes (at the top ot the 'strut tower').

You now have at least some scope for adjusting rear camber (the maximum neg camber being limited by how far out you can wind the control arm adjusters and still keep enough thread depth interlocked in the adjuster). You don't seem the sort of person to fetishise massive negative camber for misguided 'aesthetic' reasons. Personally I would aim for a smaller negative rear camber angle, at least keep the rear neg camber angle a bit less than the front.

Keep in mind that the rear roll stiffness will be increased, and so roll motion will be decreased. Less static negative camber will be needed to pre-emptively counteract body roll induced positive camber gain at the outside rear wheel. The camber of the inside rear wheel is of relatively little consequence, especially with the stiffer rear ARB because this will increase lateral weight transfer from the IR wheel to the OR wheel. At the same time, weight transfer from the IF to the OF will be lessened, despite nothing having been done to the front roll stiffness. These effects tend to decrease understeer (though not in all cases, often depending on the load sensitivity of the particular tyres fitted).

I advise at least some toe-in front and rear. Plenty of people will disagree with me about the front toe.

Regards,
John.

[Citroënbender]

It's worth pointing out the differences from your car to his.

1. Springs and shocks - you are running the lowered, stiffer Ti springs and renewed shocks.  He is on OEM shocks and standard ride height.  Your car has the reinforced rear strut top rubbers of the Ti and GTA, his does not.

2. Rear linkages and bushings - his car runs the modified rear trailing arms, yours has the original spec. Yours has the original spec stub axle and small eye bush for the trailing arm, the bush was revised twice and the stub axle once before DV's car existed.

3. Front suspension - the lower control arms were revised four times (the last in 2008), with the most attention being given to rear bushings. Yours has cast alloy front suspension forks, his are malleable cast iron. Both cars, if original, missed out on the final iteration of the upper wishbone. 

[Divano Veloce]

Thanks Citroenbender!
there are quite a few differences there, I didnt know about any of them.... Whats similar though is the improvement this modification has made. The car has gone from tedious, disappointing, tiring and at times dangerous to competent and enjoyable. It is far more stable on B-roads at speed. Its typical for alfa to underspec suspension bushes somewhere (its probably the most "Alfa" thing about the car). Like castor rod to body bushes on the 75/Alfetta....

I'll start a new thread for 147 handling/suspension tuning as this one is specifically regarding an awesome hack to the rear lateral control arms.

[johnl]

It's worth pointing out the differences from your car to his.

1. Springs and shocks - you are running the lowered, stiffer Ti springs and renewed shocks.  He is on OEM shocks and standard ride height.  Your car has the reinforced rear strut top rubbers of the Ti and GTA, his does not.

Hi CB,
I agree, both cars are not the same, so a stiffer rear ARB may interact a bit differently with some things on one car vs the the other car. I am still surprised that the GTA rear ARB seems to be causing handling issues, since my substantially stiffer rear ARB didn't...

My car has the Ti badges, but I'm not entirely convinced that it has the Ti suspension. It sits very high, approximately 70mm gap at the front and 75mm at the rear (top of tread to highest part of wheel 'cutout' in the quarter panels). I can't imagine it sitting any higher!

I hear that the stiffer GTA / Ti strut rubbers are very hard to find?

2. Rear linkages and bushings - his car runs the modified rear trailing arms, yours has the original spec. Yours has the original spec stub axle and small eye bush for the trailing arm, the bush was revised twice and the stub axle once before DV's car existed.

I haven't yet given my trailing arms any thought, since they are giving me no problems. What is wrong with the early trailing arms etc, that Alfa felt the need to "revise" them?

3. Front suspension - the lower control arms were revised four times (the last in 2008), with the most attention being given to rear bushings. Yours has cast alloy front suspension forks, his are malleable cast iron. Both cars, if original, missed out on the final iteration of the upper wishbone.

This is something that I think I can feel, i.e. the lower wishbone bushes do feel like they flex too much (or at least I can feel something flexing, and these seem the most likely culprit). They felt like this from when I acquired the car, despite the lower wishbones being recently replaced before the previous owner sold the car (so aren't knackered).  This is a likely place that I may well eventually fit poly bushes (the harder black ones, or whatever colour the other mob makes their harder version).

These rubber bushes feel to me that they are dumbing down the steering feedback, as well as taking the edge off steering response. I think they are probably deforming significantly under heavy braking, and contribute to the odd wierd wiggle in the direction of forward progress (i.e. contribute to toe change whan the wheel encounters a bump, and I don't mean bump steer in the classic kinematic sense). A clue might be that the steering feels sharper when the ambient temperature is colder, i.e. when the rubber bushes will be stiffer, which gels with the steering and handling being better on colder days...

Do the iron forks make any actual difference compared to the aluminium forks? I'd be very surprised if they were better in a dynamic sense, but maybe there were breakage issues with the aluminium? They at least appear quite rigid to me (likely to be, from appearance), and probably significantly lighter than a cast iron version.

What makes the final version of the upper 'wishbones' better than the earlier ones?

Regards,
John.

[johnl]

.... Whats similar though is the improvement this modification has made. The car has gone from tedious, disappointing, tiring and at times dangerous to competent and enjoyable. It is far more stable on B-roads at speed. Its typical for alfa to underspec suspension bushes somewhere (its probably the most "Alfa" thing about the car)......

........ an awesome hack to the rear lateral control arms.

DV,
That is more or less how I feel about the nature of the original rear lateral control arms, and the substantial improvement made by the Toyota based arms. The original arms really let the chassis down, badly...

And before anyone suggests it, my Alfa control arm bushes were not in poor condition, the previous owner had them replaced shortly before selling the car, but nevertheless they were terrible...

Regards,
John.

[Citroënbender]

Hi John, comparing the colour daubs on your springs with DV would be one way to determine what spec they are. Wheel hub CL plumbed up to the arch lip underside edge is another way. No idea of the weight difference from the JTD to the TS drivetrains.  They use slightly different front subframes but I doubt the lower arms mounts vary. 

I can't comment on what makes the newer stuff better, the only things I can say in relation to multiple part numbers are - I believe they sometimes honour the original part for situations where people are repairing specific damage and you desire relative consistency left-to-right.  Also, some of the supersessions might well be marriages of convenience; if there is a similar bushing entering currency within the maker's family of brands, it may be economic to standardise and reduce unit costs/inventory.