three link upper link question

[lobudget]

I'm building a parallel 3 link for a FFR roadster (not their kit three link) and don't know the which is more important, increasing the upper link length for a better upper/lower ratio or keeping the upper link closer to the axle centerline. Right now I'm at 23" ish lowers and 17" upper (with 7 degree forward down angel) attaching five inches behind the axle centerline.


There is room to keep lengthening the upper if it goes further behind the axle. Would an 18" upper mounted 6" behind the axle be an improvement over a shorter link closer to axle center line? I could even fit an equal length upper but it would be 11" behind the axle centerline.

[NorthFalcon]

Do you have any idea what kind of total travel you will have? The advantage of having equal length links, is the pinion angle does not change. If you have short travel and a shorter upper link this pinion angle will not change dramatically. A 17" upper link sounds more than adequate. Instead of worrying about the upper link length I would worry more about being able to tune it, as well as tune the lower links to change anti squat.

[lobudget]

Thanks for the input. I expect to have about three inches of compression and two inches of drop. I know that I should be including adjustments but the build keeps getting bogged down so I'll probably start with fixed points for now. Starting point is level lowers and and about 7 degrees forward/down on the upper. I may be limited to parking lot skid path evaluations of the result for quite a while so even if I took the time to make it all adjustable I would't put them to good use. It will probably see a drag strip long before a road course but obviously the whole idea is better handling than the over the counter FFR 3 link.

[jetmech442]

I originally planned to hang mine behind the axle, like you're talking about, but then as the project kept growing, I abandoned the idea to concentrate on adjust ability since I will use it for AutoX and roadcourse(Blackhawk Farms, Gingerman..etc). The stock triangulated 4 link had very short SVA uppers, and I didn't really have an issue with the amount of pinion change on launch, so I charted for same or better.

I would say, that even if you don't get the adjustable holes in the exact perfect spot, having extra adjustment will help. My first trip to blackhawk had wicked wheel hop when I was hard into the brakes, I think this is a combination of 100% AS and still too much rear bias. I plan to drop it down a notch to 70% and try again. I have three holes on the axle side and 2 frame side, to give me a range of 40-160% in 30% increments.

Keep at it man, and good luck with the build.



162572

162571

[lobudget]

jetmech442, yours looks pretty sweet. I've tried to leave enough area around the mounting points to drill extra holes if/when road tests warrant changes. This project has been bouncing around the garage for almost nine years. Time to get it on the road.

How do you like your LQ9? I have one with a set of LS3 heads for a '68 Camaro but first things first.

[jetmech442]

Offset 3link! dude that's awesome. you seem to be offset nearly the same as the example pics online. Height might be a little low, but I'll resist the urge to armchair QB your build since there's only one pic, lol. I'v always thought the FFR's were so awesome, good luck man, hope you get it on the road soon!

Oh, and I love the LQ9.I've got it paired with a 228R cam and it was super easy to tune. On track it just sings and it's been dead reliable for several years now. Each year though I consider the LS3 head/intake swap, but never pull the trigger.

[lobudget]

You're right about the upper link height. It's about an inch closer to the axle center line than the lowers. The passenger seat has some influence on it. I'm also letting ease of fabrication drive some of the geometry. I hope in the end it's worth the effort over just using the FFR 3 link kit.