Rear Suspension: Four Link vs. Three Link?

[Loren]

(I hope you guys don't mind questions that have answers that are probably obvious to people more knowledgable about cars than me.)

In perusing the FF order page for the '33 I see that a "four link" rear suspension is standard, and a "three link" is described as an upgrade that costs $599 more. I have no idea what a four link, three link (or two, one, or no link) suspension is. Can someone explain them in fairly simple terms?

Why is the three link better? Is it an advantage on the street or the track—or both? What are its disadvantages compared to the four link?

I want to build the best '33 for me that I can, but I have no basis for choosing one or the other, other than that the three link is an "upgrade".

My '33 would be built with full fenders, the hard top, and would go out for autocross and track lapping days (but no wheel to wheel racing) and it must be well-mannered enough on the street that my girlfriend (and wife of 27 years) will be happy to go for rides with me.

Three links or four?

Thanks in advance for replies.

[j33ptj]

The number of links refers to how many "connections" there are between the rear axle and the frame, excluding the dampners and drive shaft.

So a four link has two connectors that go from the dif to the left and right side of the vehicles in a \/ shape, and two links straigt' so it sorta looks like this |\/|

A three link as three (duh!), not 100% sure how they run, but supposedly(?) give better cornering behaviour, while the four link is better for straight "dragging"

Jeeps have a five link: Two upper and lower control arms on each side and a Track bar across the vehile.

Suggest googling it for more information!!

Robert

[Loren]

Thanks for the reply.

Yes, I googled and wiki'd and got basic descriptions of the geometry, but not much about the advantage/disadvantage tradeoff, and of course nothing about how it might apply to a FF '33.

Given how I plan to use the car, three link sounds better for me if it improves cornering. Any other advantages/disadvantages as it applies to the FF '33?

[Olli]

Loren,

Based on how you intend on using the '33, go with the 3-link.

Olli

[Sailor]

So your girlfriend AND your wife of 27 years need to be happy to go for a ride with you? Is there going to be a rumble seat or will they have to take turns? :D

[riptide motorsport]

depends what you want to do with the car,,,if your just driving it with the ocasional drag strip run, then a 4 link is fine....if your going to do some form of competitive racing the 3 link is for you......Steven

[edwardb]

Well, I'm a Roadster guy, but this point is widely debated over there as well. For Roadsters, one of the options is also IRS, but that's another discussion. The explanation about the number of links is correct. The comment about depending on how you're going to use the car is very important. Although the most economical, the problem with the 4-link set-up is that in certain situations the geometry can "bind" and then come loose unexpectantly with unpredictable handling results. Quick snaps and/or spins can and do result. The 3-link doesn't have the binding problem, so is more predictable and can be taken to the extreme more reliably. Having said that, though, with aftermarket parts, like those included with the kit (Koni coil-overs, control arms, better bushings) the 4-link is OK and can actually handle more power and is better for straight line launching.

So if you're only going to drive in the street, not go to the edge e.g. track, auto-x, etc., the 4-link can be an acceptable and economical option. But the 3-link will definitely give more reliable handling, and most would agree is the preferred setup between the two.

Having said all that, my Roadster is a 4-link, with all aftermarket parts. I just using it for street cruising, and I'm very happy with it. No complaints at all. For my use, it's fine.

[ehansen007]

To me it seems more simple in that with the four link you're looking at up and down movement and with the three link you get more of a pivot point allowing the fixed axle move more freely and arc as it's moving up and down. Does that sum it up? You also get to adjust the pinion angle to match the ride height of the car.

[edwardb]

Did a quick search, and found this link. Scroll down to the section about rear suspension. Explains the 4-link setup, and the reason why it binds. Note this is a stock Mustang setup. The FFR non-donor setup for Roadsters and the 33 Hot Rod uses upgraded upper and lower control arms, and replaces the coil springs and quad shocks with Koni coilovers. But the basic 4-link concept is still the same.

At the end of the article there is an animation of the 3-link (upper control arms replaced by a single panhard bar) and 5-link (upper control arms replaced by a watts link). Levy Racing sells this setup for the Roadster, and it's supposed to be the most trick setup for a solid axle. The animations show why.

http://www.miracerros.com/mustang/t_suspension.htm

[BillB0B]

(I hope you guys don't mind questions that have answers that are probably obvious to people more knowledgable about cars than me.)

In perusing the FF order page for the '33 I see that a "four link" rear suspension is standard, and a "three link" is described as an upgrade that costs $599 more. I have no idea what a four link, three link (or two, one, or no link) suspension is. Can someone explain them in fairly simple terms?

Why is the three link better? Is it an advantage on the street or the track—or both? What are its disadvantages compared to the four link?

I want to build the best '33 for me that I can, but I have no basis for choosing one or the other, other than that the three link is an "upgrade".

My '33 would be built with full fenders, the hard top, and would go out for autocross and track lapping days (but no wheel to wheel racing) and it must be well-mannered enough on the street that my girlfriend (and wife of 27 years) will be happy to go for rides with me.

Three links or four?

Thanks in advance for replies.
Don't forget there also a Five-Link rear suspension that's been install on a Factory 5 on one of the TV Build.
If your not plan on racing in a straight line go with the 3 link that has a panhard bar . If you want the best for what your plan to do with the car go with IRS.

[NAZ]

edwardb gave a good basic explanation of the benefits of the three-link over the four-link. So here's my thoughts that may help you decide on which way to go.

Don't get too hung up on which one is supposed to be the best as this is very subjective and highly dependent on the intended use of the vehicle and your ability to tune it. The best designed suspension will only achieve its potential when someone with the knowledge sets it up properly. In the hands of a novice a suspension with lots of adjustability may lead to some interesting and nasty handling characteristics so the "keep it simple" approach may be better for most folks. The simplest suspension FFR sells for the 33HR is the triangulated four-link and there is really not much to adjust or mess up.

The three-link may be an improvement but it is still seriously lacking in design as it carries over the inefficient triangulated lower control arm design of the four-link and has little adjustability for folks that know how to tune a suspension. Then there's that banana bracket that folks seem to have trouble with. But you probably can't mess this one up too much as there is really not much adjustment you can make. Ride height is probably the one adjustment most will make and not understand how it affects handling and the other suspension dynamics. Suspensions are a system and when you make an adjustment as simple as ride height it affects other areas.

Then there's the IRS option and a good one it is. If I wasn't planning to drag race mine I'd have opted for the IRS and it would have saved me a ton of modification work. It's not so complicated that a good alignment shop would have trouble setting it up and if you decide to learn about suspension design and set-up down the road it would make a good base in which to tinker with as you learn.

But all three of the suspension choices offered will give you a car that handles much better than the typical family sedan even if it's not set-up ideally. However, once you decide on a design you should consider that permanent. Unless you have a large checkbook or serious fabrication skills you will have to live with your choice.

[jolsen42]

You do realize that this thread 5 yrs old. :D

John O

[JimLev]

It may be 5 years old but it's helping me decide which one to order before the end of the year.

[bellingson]

It may be five years old, but I'm reading through it for the first time. I'm no novice to rear end geometry, but the thread makes me feel better about the decision I'd already made to spend the money on the IRS!