Positive Steering Response System
AMP-SUS-110
Another part the Mini world has been waiting for! Increase steering response while braking and accelerating with the ALTA Performance™ PSRS.

http://www.altaminiperformance.com/p...esponse-System

I was wondering if this was a worth while suspension improvement.

Tia.

MiniBull

 

Here's a copy of a thread I started at http://www.metroplexmini.org:

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At my last track event, I noticed that the car was wandering around terribly under hard braking. It didn't stop me from having fun, but it was a chore to keep the car pointed in the right direction.

I traced the problem to the front suspension, and specifically to the sad rubber compliance bushings located at the inner rear position of the front suspension control arm (the "wishbone").

Rather than buy a set of stock bushings, I did some research and settled on the recently introduced ALTA PSRS. Here's the hype:

Yes, apparently they get rid of "wondering" when larger wheels and tires are installed.

Questionable ad copy aside, these units looked promising to me, as they have the look of proper detail design and quality manufacturing.

Here's how it looked next to the stock bushing:



Now, mind you, these are not easy to install. The bushings are pressed into place, so it takes some special tools to replace them (not special as in expensive, just somewhat unique to the task). See below:



The most diffcult part of the task, though, is to remove the bushing carriers. It requires some extensive work:



The ALTA PSRS can be pressed in at any angle, but there are two suggested orientations. The first clocks the white lines on the face of the bushing at 12 and 6 o'clock. This setting provides the maximum added castor. I chose the other setting, though, which adds some castor and some anti-lift (by affecting the mounting point position both laterally and vertically:



When installed on the subframe, the PSRS bushings look like this:



Alright, enough of the garage stuff, you might be saying. How well do they work?

Well, I need to coin a phrase here. How about "Fawesome"? The effect on my MINI is just amazing. Threshold braking from 100+ mph, especially in sections which necessitate braking in other than a perfectly straight line, no longer causes the car to yaw like a swimming shark. As a BIG bonus, the car responds to steering inputs. RIGHT. NOW. It's amazing.

To be honest, these parts would be helpful on a stock MINI, but the effect would not be so dramatic. My MINI, for the record, is highly modified, and the suspension includes a very strong front anti-sway bar and springs that are more than double the factory spring rates. Because of this, nearly all of the suspension compliance was concentrated in those two factory rubber bushings, resulting in unwanted toe changes under braking and acceleration that I can only describe as "wacky".

Executive summary: Wow. These are difficult to install, but the result is amazing. It was totally worth the effort.

 

Thanks for the great write up

 

I'm having some of the "dynamic stabillity" issues you listed, and the parts are right next to me. Dropping the subframe on Monday....

Matt

 

drmike,

Is the rear trailing arm bushing in your car stock? I have the same problems braking from 100+ and the Power Flex bushing did nothing to cure this. I began to wonder if the rear trailig arm bushing was playing a part. I plan to replace mine with a stock material since the car has 85K miles.

This may appear a curious question, but I also drive my car 304K a month for work. Have you driven on public roads with the new bushings installed? If so, how would you rate comfort over RR crossings for example? The P-Flex bushings are horrid, but a track car isn't supposed ride like a Buick

 

All good questions. The upper and lower rear arms are replaced with new-in-box, "garage sale" adjustable arms that I got from people who bought them but never installed them. The lower arms are rod-end, while the upper arms are urethane-bushed. Odd, yes, but I'm racing on a budget... anyway as a set they are much stiffer than the stock setup.

You drive your car 304K a month? Woah, that's 422.2 mph nonstop. OK ok that's enough... anyway, I haven't bounced over any tracks (yet!), but I did seek out a few 1.5 inch square-edge bumps. At 50mph I didn't notice much difference over the stock bushings. This is probably because everything else is already so stiff. Still, I'll be much less willing to crash over the kerbing at the track.

 

...3-4K miles...I'm a horrid typer. Yes, I have adjustable arms out back too - all four. But, is your trailing arm bushing stock?

Thanks a for the feedback!

 

Ah yes, it would help if I actually answered the question. Yes, the trailing arm bushings are stock.

 

Nice write up. I asked this very same question a few months ago.

I am glad to see the positive feedback as well as a write up to make me realize that it is not as easy as it might seem but it sure does give me an excuse to buy some new tools!

Definetely a must have for the track.

 

Mike, thanks for sharing, and a nice job at that! I've been eye-balling these for some time now...

Good timing for Matt (Dr O)! Best of luck on Monday...

 

I guess I'll have to cancel all my upcoming track days until I get some then.

 

Jasen, your car looked very solid last year at LRP.

 

Nice write up.
Looking forward to what DO has to say.
Can it be done without the 20 ton press?

 

I'd say the more difficult bushing needed between 5 and 10 tons of force to break loose. A hammer won't work, and a big heavy vise is probably risky. The press is the way to go.

 

Question: Is it possible to take the carriers out without dropping the subframe. I thought it would be as easy as removing the three bolts, pull the arm down and slide the carrier off... not gonna be that easy?

 

the consensus is no, that to get the carriers you have to take out the sub-frame. Those with the magic BMW bushing tool may not have the same issues. That can pull the old bushing while still on the car. I don't know if it can press the PSRS in though...

Matt

 

hmm.....you start yours yet Doc?

Im just not seeing how it's necessary to remove all that. maybe remove the arm, but the whole subframe!?

 

You have to pull the subframe way down to get the rear bolt to rise enough to lift out of the bolt hole. By the time I could move the subframe that far, it appeared that it was just as easy for me to drop the subframe. Maybe not, but it looks that way to me.

 

the horse was lost.... I lost a day due to a wood stack knocked over in a storm, and then Napa didn't have a ball joint tool in stock! Now I'm about to dive in, but I've lost a week....

Matt

 

The bushing bracket carrier can not be removed without disconnecting everything needed to drop the subframe completely.

There is an issue with the BMW bushing removal tool in that sometimes the rear disc, which pulls the bushing sleeve through the bushing carrier bracket, will slip inward causing a flared end. The work around is to reverse the disc and place a large washer between it and the busing sleeve; once surface tension is broken and the sleeve gets close to flush with the bushing bracket carrier, the disc can be turned around and used as intended pulling the stock bushing and sleeve through. What this means is, if you are one of the unfortunate ones, the subframe will have to be lowered enough to clear the extra length & width the washer adds overall.

The next question is whether the BMW tool will install the PSRS. Because the puller bolt must be absolutely centered within the bushing bracket opening it is not known at this time (at least by me) if the offset opening in the PSRS will allow the tool bolt to center properly.

If it were to work then the subframe would not have to be removed completely only lowered; the steering column would still need to be unbolted, the power steering reservoir released, the outer ball joint unbolted, the front bumper removed etc., but the steering pump wires could stay hooked up and the tie-rod ends would not have to be popped. I don’t think that’s enough work savings to do it half way. The first time someone drops the subframe it goes slow but the next time it’s a breeze, I can drop it in about two hours now. This gives you an opportunity to check the health of all the ball joints, clean threads, and torque everything properly.

 

Yes, it sounds insane, but I enjoy dropping the subframe now, after all of the times I've done that. It's nice how it balances perfectly on a floor jack, and it's a breeze to put back into place.

 

How about someone smart enough to sell the PSRS already installed in a new pair of bushing carrier? How much would that cost?

 

A note here. Anti-dive works by altering geometry and as such will cause the suspension bushes and arms to load up under braking before the springs and dampers. In a vacuum this is not a good thing, but one must weigh all the advantages with the disadvantages.

 

Msfitoy thinking again

 

DAMN! well, what am i gonna do...guess i'm droppin it then.
I'll get to clean it all up real good while im at it too.

K-huevo, thanks for the input.

James