BMR Suspension's New Greasable Polyurethane Bushing Vertical Links: Industry First!

Eritas said:

The Mustang GT4 is and does. Stock integral link. Just ask the guys at Kohr.

Maybe you and Steeda should inform Ford of the benefits of using your integral links, since they can build an entire new billet LCA for their quarter-million dollar factory race car, but apparently don't understand or know the benefits of an aftermarket integral link. Lol.

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My understanding is that the GT4 uses the stock vertical link but with a stiffer durometer bushing, which Ford Racing has done a lot in the past. This higher durometer bushing inside of it, worth nothing, basically looks the same as stock - it is the same size and consequently provides the same potential range of articulation and motion control as does the stock bushings within the vertical link. You either create a bushing with the same/similar shape, just higher durometer, or a larger "flat" non-rubber bushing that can have some give in it and therefore ends up sized looking large, extending beyond the metal structure of the lower control arm and knuckle mounting points (so it doesn't prematurely crack like some previous poly vertical links I had a long time ago doing so after one single track day), or you go with an appropriately sized spherical bearing, which I've had and clearly moved on from as my car handled better especially under hard braking with something that has a bit of give to it (but everyone likes a different animal).

Not according to Kohr. They said it's a bone stock S550 link. I don't think you can find a FP integral link like FP makes for other suspension components.

That's interesting, as I've heard what I posted, alongside Ford has taken stock components and changed the bushing with in it before. But I can be wrong there, I don't have skin in their game. But fundamentally, this is suspension tuning. What do you learn from what Kohr does? That the vertical link has a specific job and race teams are learning that eliminating rubber (or, at least compliance) in some places for the sake of doing so isn't necessary (or at least isn't preferred by the driver). All this time proclaiming spherical bearings in vertical links are the bees knees while other companies offered solutions with some give to them (delrin, poly) for a reason and not just to be less expensive. I have had poly (I like them, 3 of 4 bushings cracked after one track day due to a bad poly resin mix apparently), spherical (hindsight, wasn't a fan unless perhaps I was a dedicated drag racer with a big rear end and big power, but even then...), I now have delrin (which I'm more than happy with; no twitch under braking or hitting track curbs).

I'll try another poly option someday so long as it has bushings designed to be strong/compliant enough to last doing what doesn't look like but apparently is a pretty tough and harsh job.

You had a delrin, poly, and spherical integral link?

Kohr doesn't decide what's on the GT4. Ford homologates the car, and you can't change out suspension parts. The GT4's control arm has spherical bearings in it, replacing OEM rubber bushings, so they easily could have done something to the integral link if their testing and development felt it was needed. That's my point.

The IL is under tension on throttle and prevents the knuckle from rotating backwards, and is under compression under braking. Short of doing a FEA analysis on the suspension, it's difficult to understand the need (if any) to change the bushing or link from the thin stamped steel OEM link to these massive aluminum connecting rod (Steeda) looking links or 1"x1" bar stock (BMR) that these guys are trying to sell people on.

I started with Boomba's poly vertical links as literally my first suspension modification. I liked what they did, but one track day cracked the poly on 3/4 bushings. Boomba, without question, rebuilt them and I sold them to a friend, who abuses his car daily but only on the street and they are apparently fine. He noticed the same benefit I did. It was just a bad batch of poly resin or something, I'm guessing. But I went with their links because the bushing itself clearly allowed articulation similar to the stock bushing as does the stock vertical link, just, in theory any way, more controlled given the higher durometer. If their bushing were larger in size, it probably wouldn't have cracked.

I then went with BMR's spherical units. That was a noticeable difference but, long story short, I wasn't a fan of how the car handled under heavy braking and when hitting curbs (car would skip over more than it does now). It wasn't for me on a road course but I know other folks who like them. In a drag race scenario, which I don't really like, they did help the car feel more solid. But I noticed zero "grip" difference and actually ended up getting better times despite a more extreme road course alignment when I switched to Steeda's delrin vertical links (but there are vastly more variables in play, including having more experience, to say it was just vertical links that made me hobble over a 1/4 mile faster). Fundamentally, I'm the worst launcher on earth so... grain of salt.

On a road course, I'm more than happy with Steeda's delrin link. That's just me. I've always noticed a better vertical link helping the inside wheel in a turn stay planted. That is the only benefit I've ever noticed. I don't honestly feel like a vertical link contributes greatly to improved lap times once you move from spherical to something with some give in it. I'd run an experiment, but I'm not rich enough to buy track time just to test stuff like Kohr. Keeping in mind, if you observe Steeda's bushings, they're huge which in turn allows articulation yet is going to help longevity and that also seems to mitigate "squeak" noise that can be blamed on metal parts touching a bushing that needs to flex without Energy suspension lube a-plenty and/or bushings that are so small they get dug into by the bolt/washer as they flex more extremely.

As for the size/heft of the actual arm - I'm not really sure if it's necessary to have that much metal. But we're talking about notably stiffer bushings and I do suspect the stamped steel would begin to reach its limit beyond the current soft rubber bushing. If not, no worry about being safe and keeping it strong as they aren't really heavier (if at all) than the stock stamped steel, so... why not? In Steeda's case, the size of the arm is just akin to the size of the bushing race, clearly preventing any opportunity for a weak point in the structure as it narrows (i.e., if it narrowed really quickly into a smaller center bar). It's just intelligent design and it looks cool, which people care about.

As for Kohr, they may not feel the need to do anything with the vertical link. That doesn't mean other race cars don't. Also, the GT4 may be super fast but it isn't a full weight street car attempting to corner carve. Stock vertical links are also very cheap and race car parts break. They have to decide what to spend money on. Which is why I sometimes get confused (especially with hindsight and what I've learned) why people immediately jump to buying vertical links first when really they probably should start with better dampers.

I have the LCA bearing in the rear and all of my rubber bushings in the rear IRS and front suspension are either a delrin, poly, or spherical. No stock bushing remains. The combo I have I love as it made a very vague-feeling car come alive. If I had a car that was hundreds of lbs. lighter that I needed to run a budget on top of for racing, I might change my approach, I don't know. Kohr can do Kohr. I'll do me. I'm speaking from experience with a range of vertical links, not speculation that a factory race car equates to me car because it has the same body work.

Again, Kohr doesn't decide which suspension components are on the GT4, Ford does and determined it wasn't necessary. Kohr can't even change them if they wanted to.

I think you're talking more theory if rubber vs poly rather than analyzing the diameter, thickness, and deflection of the stock IG bushing (which is very little). Also I'm not sure what the diameter of Steedas delrin bushing has to do with deflection or longevity because it's a hard plastic that will not give to begin with.

How much load even goes through the IG? It's a single shear bolt for crying out loud, aftermarket links don't need to be that big, heavy, or strong.

The aftermarket options improve inside wheel hop/chatter when coming out of slow corners. That is pretty much the main performance improvement. For a road course-only car, I can see them being less needed. Is there a performance improvement? Yes. Is it night and day like the LCA bearings?
Definitely not. Was it worth it for Ford Performance to develop a different link? Obviously they didn't think so.

Steeda has a video that shows the diff and subframe bushings being the main cause of wheel hop, which is why the GT4 has solid bushings. Im not buying that the integral link has any affect on wheel hop.

Eritas said:

Steeda has a video that shows the diff and subframe bushings being the main cause of wheel hop, which is why the GT4 has solid bushings. Im not buying that the integral link has any affect on wheel hop.

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I will report back when I install these. I already have the cradle lockout kit, so my subframe is barely moving. The primary cause of wheel hop is the subframe bushings and LCA bushing deflection, we agree.

Eritas said:

Again, Kohr doesn't decide which suspension components are on the GT4, Ford does and determined it wasn't necessary. Kohr can't even change them if they wanted to.

I think you're talking more theory if rubber vs poly rather than analyzing the diameter, thickness, and deflection of the stock IG bushing (which is very little). Also I'm not sure what the diameter of Steedas delrin bushing has to do with deflection or longevity because it's a hard plastic that will not give to begin with.

How much load even goes through the IG? It's a single shear bolt for crying out loud, aftermarket links don't need to be that big, heavy, or strong.

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Enough load that my first set of vertical links, again, had 3 of 4 bushings crack. After some normal road miles and a track day. I'd say it gets plenty of load. Can the metal part of these be less substantial, probably. Does it make sense to do so when already the aftermarket options aren't any heavier (and in some cases lighter)? Nope.

I can move/bend the stock rubber bushing with a bolt through the hole by hand if I put a little ass into it. Kohr / Ford, again, didn't feel the need to spend money there. Not to mention, the GT4 doesn't have the same rear LCAs as our plebeian regular street-going Mustangs have. It has LCAs designed specifically for its coilovers, which, for another topic, just supports my concern about a true coilover in the rear of these cars. Stock LCA wasnt' designed for it. GT4 LCA was, and it has a much better suspension than your Mustang has for track duty and simply may not get any benefit from any sort of improved vertical link. Speculation, but since we're leaning on a factory race car as any sort of comparison to our S550s.

wildcatgoal said:

Enough load that my first set of vertical links, again, had 3 of 4 bushings crack. After some normal road miles and a track day. I'd say it gets plenty of load. Can the metal part of these be less substantial, probably. Does it make sense to do so when already the aftermarket options aren't any heavier (and in some cases lighter)? Nope.

I can move/bend the stock rubber bushing with a bolt through the hole by hand if I put a little ass into it. Kohr / Ford, again, didn't feel the need to spend money there. Not to mention, the GT4 doesn't have the same rear LCAs as our plebeian regular street-going Mustangs have. It has LCAs designed specifically for its coilovers, which, for another topic, just supports my concern about a true coilover in the rear of these cars. Stock LCA wasnt' designed for it. GT4 LCA was, and it has a much better suspension than your Mustang has for track duty and simply may not get any benefit from any sort of improved vertical link. Speculation, but since we're leaning on a factory race car as any sort of comparison to our S550s.

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How many stock Integral links did you break? Crappy, inferior, weaker than stock aftermarket ones don't count.

Ok, so the stock bushing has axial play, that's not the function of how that bushing and link works. It's a tension and compression arm, so twisting and deflecting the OEM bushing does not tell you anything. Now measure the compression and tension deflection and get back to me.

The GT4's LCA is irrelevant. It's the same Integral Link design and has the same mounting points to the subframe, hub, and IL itself as factory. Just because the GT4's LCA is different doesn't mean the integral link functions any differently. The fact Ford retained the OEM IL while changing the LCA (which isn't cheap) tells you something... -It's probably unnecessary to change out the link to begin with on a stock S550.

Well, if it's unnecessary then why did my car improve with even those cheap vertical links? I mean... it was obvious the first turn I made. I may have gotten a bad poly bushing mix in my Boomba links, but you could clearly tell they would allow articulation like the stock vertical links. They worked (just not for very long). It may not have been necessary on the GT4 with its superior LCA and specially designed coilover suspension which is of course doing an excellent job of controlling the rear suspension in a lightened, non-street legal race car where NVH and doesn't matter and cost/benefit doesn't justify it.

We don't have GT4s. A good quality vertical link with appropriate articulation and a properly designed bushing (not so much durometer, but its ability to articulate in the narrow range of motion it does need to without binding) will most certainly help the S550 rear IRS maintain its geometry as it articulates ESPECIALLY given the high-rate inward spring location and especially when the owner does not have an LCA bearing upgrade.

It is not the end all be all or even the first modification someone should do. If we are following the GT4 as a model, the first thing to do is better dampers and springs, keeping in mind the cast aluminum (brittle) LCA on our cars is NOT designed for a true coilover at the lower mounting point. While you're at it, go through the pain and suffering to install the LCA bearing WITH better upper shock mounts (or you will most likely get some bounciness, which has been demonstrated time and time again). Steeda makes mounts, others do or will in time - all will have bearings as it clearly makes sense there.

A bushing with true engineering and testing behind it that's made to last will not cause bind and will not get cut into over time (due to is movement) by the bolt/washer that secures it because it is large enough to sufficiently articulate over a larger space as needed (however little it may do so) without rubbing into the bushing. You especially don't want that kind of bind and pressure points close to its outer diameter where it is most liable to degrade and crack under whatever stress it endures. Poly is most liable to crack if dug into and put under narrowly applied stress - it has to be properly sized and designed for the task to prevent that.

If you don't feel you need vertical links, well... don't get them. I chose the ones I did because of their design - reasons I've articulated already. And in hindsight, I wouldn't have started with vertical links and tell people not to all the time (because they are not as important as internet forums seem to dictate - so we're on the same page more or less). Race cars weigh cost/benefit. There was clearly not enough benefit with the GT4's rear suspension design to change the vertical link after designing a special LCA and coilover system. That does not mean there is no benefit from a well-engineered aftermarket vertical link on our cars. Simply is not an apple to apple comparison.

Lol, yes I will take your word for it when you don't know how an integral link works or the forces that act upon it. If you can't even understand that, there is no way you can understand what the changes in the LCA did to the GT4.

On another note, the new Ford Performance FP350S racecar appears to use coilovers on the stock aluminum LCA. How is that possible??? They're not out yet and I'm not sure if they also use the stock integral link or not but I'm sure we will find out sooner or later.

A placebo is a hell of an effect. As long as you're happy with, and feel your money is well spent, that is all that matters.

You can bolt anything to anything. Doesn't mean I'm gonna sign up for it.

I do understand how the integral link works. I have agreed in effect that it isn't a first modification. You say it isn't necessary, but others benefit from them. My point is, if your going to replace a part, make sure it's designed properly. This is inches not miles. The GT4 doesn't need another inch, so to speak. This is a driver feel modification.

Say what you want, I did not perceive a placebo effect against the stock vertical link. Is it a massive change? At extremes is where it's noticed. The GT4 isn't a fair comparison. It's LCA does not need to contain and control a high rate spring (as compared to wheel rate) while maintaining geometry with the knuckle to which is ultimately attached a heavy breaking system with incredibly heavy wheels holding up a full weight, road legal car.

If it doesn't matter what's there, just slap a steel rod in and call it a day. Or stop arguing with someone who won't buy what's advertised here either. Hope you make it through the hurricane unscathed.

Lose power for a few days and come back to all sorts of good reading!

Good stuff guys. Keep it up. ;)