ALFAGTV6.COM

[Duk]

How about a lowered pivot point for the watts linkage mount? That was a recommendation from Beninca. Not too low, maybe the pivot is moved into the middle of the dedion.

I thought I'd post this question 'cause it's been too quiet around here......
Would a lower watts link pivot point be considered more of a race car modification? IE, is there any bennefit in applying it on a street car?
I spoke with Vince Sharp about this some months ago, an he says the improvement isn't as noticable as raising the front roll centre (I bought some "knuckle risers" from him), so would this be a trying to get the last little bit out of a car/not really applicable to a road car?
The way I understand it from watching V8 Blooper Car racing, when they raise the rear roll center, it causes more weight transfer onto the front wheel and obviously lowering it achieves the oposite. Am I understanding this correctly?

[MD]

Guys I know we are all about improvement here and there. Sometimes big ones and other times only the owner knows that there is a tiny modification that makes things hum just that much sweeter.

When it comes to standard suspension or radical mods, it really comes down to where you want to use it LEGALLY. If you want a fully worked car to flog the shit out of it in the street to show off to your mates and hope to God you never get caught by the fuzz, well that's one execrcise but it is a pretty stupid one. On the other hand if you want to show everybody just what an ace driver you are on the track, well you need all the mods you can afford cause the track eats up more dollars than a poker machine so you need to think long and hard what it is you REALLY need these mods for.

If you are the type that just wants an original spec car to run like it was always designed by the factory and simply maintain it so that this is what happens, well you are in yet another class altogether again.

For most of us, we probably like to do a little of all the above if we are honest with ourselves.

To get to you point Duk, after stuffing around with these cars for around 30 years and modifying things so much so that the only thing that is original is the steel material in the shell, I have come to this conclusion.

>Modify to your hearts content consistent with the intended purpose of it use. If one does not have a clear purpose for the end use of the car and modify it accordingly, somebody needs to take one's head out of one's ass and stick it on one's shoulders where it belongs. (this is a generic statement and not intended for any single person named or unnamed )<

Factory settings for street applications do not require modifications for them to work extremely well period. That's why it's called an Alfa Romeo. As for other applications, well, where do you wanna go ? Make a wholistic plan first.

Duk this is not advice for you. I know you are a sharp guy.

It is for for all the young guns that read this stuff who just wanna modify this and just wanna modify that without having any idea of the end game but spend their hard earned money standing in the sucker line because they heard something or some one has told them something or another that is just the bees knees.

Know the story?

[fedezyl]

I conccur with your opinion MD on modifying a car, the thing is there's an in between person between the hardcore racer and the classic car owner, most of our alfa's (it's my case at least)are second cars, mine is a street/track car, lowered and stiffer suspension, so a little improvement on suspension geometry might help, but is like you said, are the dollars you spend on these mods really worth on your application?

[Zamani]

Duk,

The rear roll center mod is much simpler, and I suspect much cheaper than raising the front roll center (using drop spindles). I'm not sure how much of an improvement you will get, but it sounds like a good idea.

But like MD said, how far and how legal would it be in your class? Just like cambered dedion, I suspect even that is more difficult to do than the rear roll center modification.

I thought knuckle risers were for the 105/115 only?

[Micke]

Before even thinking about modifying the roll centers you should understand what it means and the consequences.
Buying 20 more HP is pretty clear but how many can honestly say they know what the advantage of playing with RC's mean?
Why does it improve the car?
In which conditions?
Does it require any other mods to the suspension?

When you can answer these you know if it makes sense or no. Then you also don't need to ask how much or how to do it.

[GTV27]

I dig all the caveat emptor stuff going on here (aren't we all very sensible all of a sudden) but also think there is scope to improve upon what Alfa stuck in the car when it was designed in the late 60's/early 70's (not quite sure when they would have downed pens on the 116...) afterall, tyre tech alone has come on in leaps and bounds since then (for instance, I can't imagine that anybody had in mind the size and profile tyres that we now routinely run).

So I don;t think it hurts to discuss the theory - even if I'm not really sure how relevant it is outside of a racetrack environment.

I 'think' the theory on lowering the rear roll centre goes like this (BTW am happy to be corrected if I've got this all arsabout - this is not my profession, I am just an amateur carmuckarounder):

-> lower the rear roll centre, reduces the effective rear roll rate, puts more load on the outside front tyre, gives better rear grip

An alternative to achieve the same effect (more or less) is:

-> raise front roll centre, increases the effective front roll rate, puts more load onto the outside front tyre, gives better rear grip

Now, either (or both) of these things sounds like a good strategy for a 105 ( are well ALLOWED to speak of such things here?), but I can't imagine needing this in a 116 (maybe mine doesn't have enough grunt to require it ).

Applying the counterfactual, perhaps the recipe for an understeering 116 should be to:

-> raise the rear roll centre, increasing the effective rear roll rate, putting some load onto the outside rear tyre, giving better front end grip; or

-> lower the front roll centre, reducing the effective front roll rate, putting more load on the outside rear tyre, giving better front end grip.

Given the settings that the factory has blessed us with - do we need to do either of these things and why do people use drop spindles to raise the front and relocate the rear to under the tube?

[kevin]

Jason, body roll determined by the distance bewteen cg and roll center hence most chaps want to raise front roll centre through drop spindles. I do some strange weldings on my cars which are all tested but personally I will not get my spindles lenghtened.(I dont trust any one here to do this). I would rather use a Alfa 6 hub like everyone uses here. Check this pic out. Look carefully

[GTV27]

oh pitchas

OK I see an alt watts mount on the bottom of the dedion, outboard brakes, a strange diff, limiting straps, big fuel pumps ... have I missed anything?

Clearly is just some hack from running down to the shops (NOT!)

OK spindles brings up the roll centre, so less gap to the c of g and therefore less 'leverage' (to use an inappropriate term) creating less roll, thereby taking more load on the front tyres, less load on the rear tyres and moving the balance towards more understeer and less oversteer. The drop on the watts should do the same thing at the other end of the car - Both of which are pretty much the reverse of what my car needs (and any other 116 that I've ever driven)

ergo I just don't get it.

[GTV27]

Duk,


I thought knuckle risers were for the 105/115 only?

no reason why you couldn't use risers on the upper arms of a 116 to lift the roll centre and get some camber gain...still not sure why though... it was a trick used onthe rally GTV6s, but I think that was about getting more droop travel for the height they ran them at

[Duk]

OK spindles brings up the roll centre, so less gap to the c of g and therefore less 'leverage' (to use an inappropriate term) creating less roll, thereby taking more load on the front tyres, less load on the rear tyres and moving the balance towards more understeer and less oversteer. The drop on the watts should do the same thing at the other end of the car - Both of which are pretty much the reverse of what my car needs (and any other 116 that I've ever driven)

ergo I just don't get it.

For front roll centre mods, you just need to look at your own signature photo.

The raising of the front roll centre by either knuckle risers or drop spindles has 2 advantages.
1: The raised roll centre gives less body roll for a given anti-roll bar diameter and front spring rate (don't forget the springs are very important fact in anti-roll bar performance), as you stated.
2: There are improvements in camber gain on suspension compression.

Less body roll to reduce the loss of negative camber/gaining postive camber and more negaitve camber gain on suspension compression should (and does) give a front outside tyre that can work harder because it has better contact with the road when it's loaded in a turn.

Where I am lost is the effect of the rear roll centre and why they change it in a fat ass V8 Fruitloop Car.
They have on the drive adjustable ant-roll bars, so rear roll centre height changes can't be only driven by rear roll rate alone.

Most (all) front engine rear drive cars have a higher rear roll cenre than the front. Weight tends to rest more at the lowest point (carry something heavey up stairs with 2 people if your bored, but don't be the 1 at the bottom ).

So, if I've raised the front roll centre, this should (as well as the advantages above) put more load on the rear wheels and help prevent the front from becoming overloaded and degenerate into understeer (understeer has already been reduced heaps and turn in improved with the KRs).
So if the rear RC is lowered, would this have the same effect of transfering more load onto the rear tyres as well, again reducing the possibility of overloading the fronts?
It's easier to stick wider tyres under the arse than the front .

But is my understanding of the effects of the rear RC correct?

Again, it's only a road car, so this is more theoretical than anything. Unless it turns out we should all be raising or lowering our RC and then start out cornering an F1 car

[GTV27]

That picture was from when the car had -1.5 static camber and used to abuse the shoulders of the front tyres - is now running -3 and is much happier in that respect

I get the advantage of camber gain from a spindle/knuckle riser change (have knuckles on the 105 - and they suit its oversteering characteristics) but I don't like the associated effect of increasing the front roll stiffness on a 116. I guess, having put on the spindles/risers, you could go down on the anti roll bar...but fundamentally, going to a higher roll centre is going to put more load on the outside front tyre relative to the inside front tyre and the rear tyres. As it is, that is the tyre that overheats on my car so is not a good move for me to do (in theory).

In terms of lowering the rear roll centre, it is going to make the rear end more suseptable to roll and therefore make the front end do more of the work in resisting roll - again putting more load on that already overwrought outside front tyre, so I can't quite come to terms with why that would be a good thing (in theory)

The supertaxis seem to use the rear roll centre adjustment to balance the car for changing conditions and are generally going only a few turns at max - depending on the pitch of the hardware, it can't be much more than a few mm in total. I'd wonder if you'd even notice such a change on a road car. As to why they use the RC and not the bars...that is beyond my current level of understanding

As there is empirical evidence out there of people who presumably know what they are doing using both spindles/risers and lowered rear roll centres, we must give them the benefit of the doubt that this is collectively a good thing to do. I would like to understand the theory of how though...

[Micke]

As I've seen mentioned several times the idea of using knuckle raisers to change the front RC on 116 cars and I have a question:
What is the change in RC using the knuckle raisers? I don't need guesses as answers.

What comes to changing balance of the car. For this you have springs and anti-roll bars.

[Duk]

That picture was from when the car had -1.5 static camber and used to abuse the shoulders of the front tyres - is now running -3 and is much happier in that respect

I get the advantage of camber gain from a spindle/knuckle riser change (have knuckles on the 105 - and they suit its oversteering characteristics) but I don't like the associated effect of increasing the front roll stiffness on a 116. I guess, having put on the spindles/risers, you could go down on the anti roll bar...but fundamentally, going to a higher roll centre is going to put more load on the outside front tyre relative to the inside front tyre and the rear tyres. As it is, that is the tyre that overheats on my car so is not a good move for me to do (in theory).

I'm not seeing why you don't favour adding KR or drop spindles to a 116, Alfa did it (eventually) when they released the SZ/RZ and they could courner with over 1G using tyres from the early '90s.
To me, it's a fix to an intial design flaw that does overwork or probably more correctly, incorrectly works the front tyres.
I was initially disappointed with my V6 75s lethargic turn in and mid corner grip even with new bushes, ball joints, LCA bearings (Bazza style) and Koni yellows. But KRs, some 105lb/in coil overs and 1 degree more positive caster (wanted more but machine only reads to 4 degrees) and only 1 degree of negative camber, I'm inspired by her new found agility. It's not quite as chuckable as my MR2, but it's not far off and it rides better. And that's with 17" rims (on the car when I bought her) and 205/40 tyres.

[GTV27]

Re why I don't favour....stuff.

On first principles, I don't understand how lifting the front roll centre (or lowering the rear) is going to help with a 116 that understeers (which is what I've tried to explain in previous posts, including the quoted one above). I'm not doubting that people do it and like the result, I just don't understand what's going on.

Something that could be happening is that cars have been lowered (perhaps by a lot) and then have risers fitted (or have the de dion mod to lower the rear) which is to compensate for the front roll centre going subterranean as a result of the lowering. But for a car with horizontal LCAs, I don't see it helping.

Micke raises a sound point - do risers actually lift the roll centre (I think he knows and is inferring that it doesn't) I've got books that say how to work it out, but they are 100 miles away (MD prob knows where) and I haven't done the measurements and figuring.

[Duk]

Fair enough.
Is this the kind of diagram you're after?
Incidently, my car looks more like the top set up with the KR 'cause it's not as low as it use to be (LCAs nearly horizontal)