looking for a good way to reduce body roll/ lower rear roll center

[BlpltGTV]

I'm looking for thoughts on ways to reduce my body roll and lower the rear roll center that looks stock. The simple easy way to do these things is bigger anti roll bars, and either a watts link, panhard or sliding block in the rear. I can't really do any of those, as I am racing a "stock" class. That said, no one protested my Centerline lowering springs. My thought is cutting one coil off the rear springs. That would both lower the rear, and give me a stiffer rear spring rate. The downside is less rear suspension travel. I will have a 4.1 LSD in the car with a 47% lockup. I'm guessing that will cause the car to push some. I also figure a higher rear spring rate might help neutralize the push.
Currently I'm running an open rear end with no rear swaybar but when I install the new rear, I'd like to get everything taken care of then since it will all be apart.

Is cutting the springs acceptable or just a display of diminishing returns? I know making the suspension super stiff does no good since its got to move in order to work. It also cracks the body in places if its left unreinfoced. Yes I'm looking for a best compromise solution.

thanks,
Will

[bianchi1]

instale a 'watts linkage' i am looking onto it now, i have a design, but need find a way to fit the turntable to the rear of the axle. a watts will lower the rear roll centre much better than a panhard linkage. the panhard really only locate the rear axle better, left or right turns, lefthand panhard , of righthand panhard linkage, thats why those nascar boys use them.. lot's of left hand turns.

[BlpltGTV]

A watts or panhard is out of the question. Obviously not stock, and does require modification to the car. I'm trying to leave the car closer to stock than anything. That is why I said a 70% solution and compromise. I really don't want to mess up a really correct car, just make it better than it is. If I were building a full on track car from a semi crusty hulk, yeah I'd go to town and do a watts link and reinforce all the suspension pickups, and add a full cage, but that is not the goal here. The goal is to build something that is faster than a mostly stock 510 with the same tires without going crazy. I also don't want someone to say hey, that's not stock and protest me. In the case of the LSD, they were an option for the car, there for I can use it. I can't run huge crazy cams either, but a set of eurospec ones would slide (don't happen to have any). The springs I have are a grey area, if someone feels like protesting, they do have grounds to do so, but I'm hoping they won't. I'm looking to flex rules but not blatantly break them.

Will

[bianchi1]

my watts will use the watts linage off a gtv4/6( newer one or milano car.just looking into the mounting brakets to the body, and to the rear axle. got most it figgerd out

[genericwood]

Quote:

Originally Posted by BlpltGTV I'm looking for thoughts on ways to reduce my body roll and lower the rear roll center that looks stock. Will

[genericwood]

Quote:

Originally Posted by bianchi1 instale a 'watts linkage' i am looking onto it now, i have a design, but need find a way to fit the turntable to the rear of the axle. a watts will lower the rear roll centre much better than a panhard linkage. the panhard really only locate the rear axle better, left or right turns, lefthand panhard , of righthand panhard linkage, thats why those nascar boys use them.. lot's of left hand turns.

[conedriver]

Hi Will,

By racing in a Stock Class, I assume this is autocrossing, correct?

If you're running SCCA Solo events or using these rules, a quick review of "Authorized Modifications": Shock absorbers, Any R compound tires that will fit on a stock rim, Front sway bar, .25 in. wheel spacers, Adjusting suspension within it's range.

Back when I ran a 1971 1750 Spider in D-Stock, I found that a bigger front swaybar reduced roll but promoted understeer. Adding Caster (by lengthening the control arms) countered this by increasing negative camber on the outside wheel when turning. You have to find the right balance since adding as much caster as possible can result in so much oversteer you can disconnect the rear swaybar (which is not allowable in Stock class). I thought all GTV's from 1972 on had a rear swaybar; was yours removed?.

Adding the LSD will make a BIG diffference; I had to drive my 1750 spider like a Corvette, only adding power when the thing was pointed straight due to inside tire wheelspin. The LSD literally transformed the car. I don't remember a lot of understeer after adding the LSD, but this was a long time ago. The items on the list that will make the biggest difference are the LSD and R compound tires. Especially the tires. If these are allowed at your events, you just won't be really competitive without them. I know it's a pain to change tires, but lots of people have little trailers for their extra set of wheels/tires and that's just the effort needed to get the desired performance.

One last item: Shock absorbers. Double adjustable shocks are allowed in SCCA Stock Class. Some SCCA Solo national level competitors run Penske Shocks or equivalent. These are seriously expensive items that you are probably not considering. However a nice set of externally single adjustable shocks would allow you to fine tune for conditions at individual events.

Finally, get a rule book and understand what is allowable. The faster you go, the more attention you will get.

Quote:

Originally Posted by BlpltGTV I'm looking for thoughts on ways to reduce my body roll and lower the rear roll center that looks stock. The simple easy way to do these things is bigger anti roll bars, and either a watts link, panhard or sliding block in the rear. I can't really do any of those, as I am racing a "stock" class. That said, no one protested my Centerline lowering springs. My thought is cutting one coil off the rear springs. That would both lower the rear, and give me a stiffer rear spring rate. The downside is less rear suspension travel. I will have a 4.1 LSD in the car with a 47% lockup. I'm guessing that will cause the car to push some. I also figure a higher rear spring rate might help neutralize the push. Currently I'm running an open rear end with no rear swaybar but when I install the new rear, I'd like to get everything taken care of then since it will all be apart. Is cutting the springs acceptable or just a display of diminishing returns? I know making the suspension super stiff does no good since its got to move in order to work. It also cracks the body in places if its left unreinfoced. Yes I'm looking for a best compromise solution. thanks, Will

[conedriver]

bianchi1,

I think you may be confused; both a Watts Link and Panhard bar can lower the rear roll center. There are other changes that must be done before adding either of these modifications. I suggest you use "Search" to find and read the many earlier posts on the topic.

Quote:

Originally Posted by bianchi1 instale a 'watts linkage' i am looking onto it now, i have a design, but need find a way to fit the turntable to the rear of the axle. a watts will lower the rear roll centre much better than a panhard linkage. the panhard really only locate the rear axle better, left or right turns, lefthand panhard , of righthand panhard linkage, thats why those nascar boys use them.. lot's of left hand turns.

[davbert]

Quote:

Originally Posted by BlpltGTV I really don't want to mess up a really correct car, just make it better than it is. Will

[BlpltGTV]

The group I'm running with is not SCCA. The class rules do not allow R compounds, the even frown upon my 200 treadwear tires. They allow Konis, but nothing more advanced, must have full interior, the sway bars can be removed if they came with them, but bigger ones cannot be added (but no one checks so I could probably get away with it, at least on the rear.) Basicly if it looks stock, I can get away with it. The rules have some lee way to allow for NLA parts, or safety upgrades, but for the most part the idea of the class is to let non modified classic cars go out and have fun, but keep it under control. The Vintage Street Prep class that I was running my Datsun in last year is basicly a free for all as long as the car was built before 1976. The only rule was that the engine must be of the correct vintage as the car. The Vintage stock class was the total opposite of street prep. That way we get really nice Jag E-types out and that sort of thing. We also have a guy who runs his '74 Porsche 911 Targa (or perhaps SC, I can't remember) in the class.

So the rules are clearly unclear and everyone is out to have fun.

Will

[msiert]

Get away with it.............you mean not being totally honest in the upgrades you have done..............That sounds like something a well know large mouth Kentucky white Spider owner would do.

In all serious, it looks like you limited to heavier rated springs, stiffer adjustable shocks and a bigger front sway bar. If you install a roll bar & petty bar that should stiffen up your chassis and thus lessen the flex of the chassis. The chassis stiffener would help in this area too but is hard to hide from the officials.

Alfaholic's has a 30 mm front sway bar that might help you out and would not be caught.

[davbert]

run a later stock S3 spider bar... its bigger than a GTV with nicer end-links.

[BlpltGTV]

When I say a "correct car" I mean its pretty much as it came from the factory. There fore I will not be cutting anything, drilling any holes, or welding anything onto the car. It still has the original Spica shocks, interior, ect. The only things I have changed are the front and rear springs, the wheels and I went from a dual circuit brake system to a single and removed the booster. I am adding the LSD, but unless someone really knows what they are looking at, they won't know. I just removed the 32+ year old headlights because I was tired of not being able to see where I was going. The replacements are carefully chosen H4s that look period correct.

I know the front suspension geometry is really bad, and was only made worse by putting the lowering springs on it. That is why I'm trying to "fix" the roll couple by perhaps clipping a coil off the already shorter and stiffer rear springs. I don't know if this is worth doing as these cars don't have a whole lot of rear suspension travel. By clipping the rear springs, that will bring the rear end down some, and give me stiffer springs as well. The stiffer rear springs will reduce the understeer that I have a feeling I will find with the LSD in place. I could also try finding a set of knuckle risers/modified spindles for the front that would raise the subterranean roll center in the front. I am aware of the downfalls of the suspension design, and I'm not really looking to fully fix them, I'm looking for a way to lessen the issues with the roll couple being so far off in the rear.

Will

[genericwood]

Will, you may want to forget about the rear and work on the front. Non-Alfa people may not know to object to adjustable upper arms for example. Years ago, I ran a Plymouth Neon in SCCA stock class. I put eccentric "crash bolts" in the front suspension to allow some negative camber somewhat legally. They aren't cheap, but you could also get some "drop spindles" that even the Alfa guys may not know you have.

Erik

[yvesmontreal]

I'm not an expert autocrosser, not even a mediocre one, but reading this thread something felt obvious: why don't you TRY the car with the LSD before deciding on whatever understeer/oversteer needs to be corrected? May prevent you from scrapping a good pair of coils. And no, coils are not that much work to replace. And yes, readjusting rear Konis can be done in the field, right in the middle of a track day.

Let's see what the experts say about this one. Years ago, I read in Alfa Owner that a hot trick for autocrossing was to remove the suspension straps from both sides and to install a single strap close to the middle... let it roll but don't pick up the wheel. I'm just not sure about this one...

A cheap way to improve the performance of a car is to reduce weight. They want a full interior, but do they want the soundproofing underneath the carpeting? Do they want a thick crust of undercoating? Do they want the heavy vinyl trunk trim? Getting rid of all this is probably worth 100 lbs... legally.

Does anybody from the governing body read this forum?