New: PSM Steering Rack Eccentric Bushing (Ackerman decrease bushings)

[CodyAce]

MAX Steering Rack Eccentric Bushing (SREB) set is finished testing and now in production.

~ Price is $50 with free shipping world wide in January (paypal maxusa@poweredbymax.net to reserve your set)
~ Production parts will be anodized gold aluminum
~ Prevents over centering of tie rod and knuckle to prevent heavy steering at lock
~ Takes ackerman curve from digressive to progressive difference while decreasing overall ackerman

http://www.gtfactory.jp/cms/e107_files/public/1322561145_2_FT4772_screen-shot-2011-11-29-at-1.15.25-am.jpg

http://www.gtfactory.jp/cms/e107_files/public/1322561145_2_FT4772_img_0276.jpg

http://www.gtfactory.jp/cms/e107_files/public/1322561145_2_FT4772_img_0280.jpg




So what are the opinions on these? Unsure how this even works aside from moving the steering rack.

[Beejis60]

Looks like from their curve that you need their knuckles for the change in ackerman.... but I honestly don't see how you can change ackerman without raising or lowering the rack even with oem knuckles.

or am i high?

[sheltonsr]

Looks like from their curve that you need their knuckles for the change in ackerman.... but I honestly don't see how you can change ackerman without raising or lowering the rack even with oem knuckles.

or am i high?

I believe they are showing the change with knuckles but with and without the eccentric bushings. They should show without knuckles and with and without eccentrics as well!

I just bought poly bushings, but if these actually do something positive...

[Matt93SE]

Looks like from their curve that you need their knuckles for the change in ackerman.... but I honestly don't see how you can change ackerman without raising or lowering the rack even with oem knuckles.

or am i high?

Take a look at the bushings. given the angle the steering rack bolts into the chassis, these bushings look like they move the rack upward about 1/4" don't they?

[CodyAce]

That's about all I can see too, is that it allows you to bolt up the rack higher in car (maybe to put it in line with the LCA inner pivot? Hard to invision without the car infront of me right now).

I just don't understand how moving a rack up can make ackerman change in a non linear way? Admittedly I'm kinda wet behind the ears with this stuff but I just take PSM's products with a grain of salt for the most part.

[Def]

It's changing ackerman by making the inner tie rods move through a different arc than stock. As in, the inner tie rods are not straight to the spindle, so that arc influences how much steering angle difference you get on each side.

As for this being a good thing for a track car - I'm not so sure. Rarely do you even put that much steering angle into the car, so the maybe 1-2 degree max ackerman difference being noticeable? I'd put my money on no since you're only at that level at very low speed corners really cranked in. At higher speed corners you are probably in a tenth or two of difference in ackerman. I don't think that's enough to really change how your tires are behaving when most have a fairly "broad" slip angle vs. grip plateau.

[Tower240sx]

well,,,since in road racing when you turn the wheel the chassis turns too I fiond eliminating ackerman or making it digressive to be counterproductive, whether or not it does what it says is secondary to the fact that it claims to do something i don't want,

Drifters aren't relying on the centerline of the chassis to be their driven direction so digressive ackerman makes (more) sense for that specific purpose,

I know DEF hates ackerman but I like it and feel it serves to improve front end traction

[Def]

well,,,since in road racing when you turn the wheel the chassis turns too I fiond eliminating ackerman or making it digressive to be counterproductive, whether or not it does what it says is secondary to the fact that it claims to do something i don't want,

Drifters aren't relying on the centerline of the chassis to be their driven direction so digressive ackerman makes (more) sense for that specific purpose,

I know DEF hates ackerman but I like it and feel it serves to improve front end traction

wat?

What do you mean the chassis turns too? It yaws?

I don't hate ackerman, but I do think it's pretty pointless to worry about it if you don't have at least rudimentary tire data. It's all about slip angle vs. traction vs. normal load and trying to make the tire as happy as possible to give you the most grip possible over as many corners as you can (note this is track dependent...). Without tire data you're pissin' up a rope, and without a clear plan on what type of cornering you want to improve, yep - more rope pissin'.

If you think the car would like more ackerman, run some static toe out and see how steady state grip feels in various radii of corners. You're going to need instrumentation to detect this, as the difference will be slight. If the car gets worse in the corners you want to improve on, run some toe-in and see how it reacts - if it's better, then your car would benefit from less ackerman.


But please Mike, give me some more touchy feely on how ackerman is your "main bro on da' track, keeping yo' front DUNLAPS in check." :p

[CodyAce]

Without tire data you're pissin' up a rope, and without a clear plan on what type of cornering you want to improve, yep - more rope pissin'

This is honestly what I've also questioned to myself: What ****in difference does it really make in the 'big end of things' when arguing these things? I can think of countless fast guys in stock cars that outrun slower guys in faster cars in the same class....I mean stick a newb in a F1 car and he's gonna suck kinda deal.

I'm glad though that these things are mentioned, but at the same time (and maybe it's the Yankee Redneck in me) I often wonder what difference it makes. I'd rather spend the money in seat time, then a few dollars on something that doesn't make a noticable difference.



But please Mike, give me some more touchy feely on how ackerman is your "main bro on da' track, keeping yo' front DUNLAPS in check." :p

Isn't he a HPDE1 anyway;) hehe just teasin ya Mike!





And with that said, in regard to ackerman, me, positive ackerman HELPS a grip car to me (although again a probably un-noticable difference) in it's function. In the same respect I couldn't tell you when it changes what I'm driving either. Another thing I've wondered with all of this ****: How on earth are these PSM guys measuring their RC correction and this and that? I mean truthfully this side of a chassis machine, the error involved with person to person measure points can throw it all off! All I know is that my LCA and Tie rod are level with the ground, the car handles great, and it's on bull**** cheap parts from this forum and the main posters.

....which further entrenches my doubt of PSM and their 'anti boring grip car' attitude. They could paint a turd orange, say it increases weight distribution mid slide, and some moronwould buy them, no questions asked.

[Def]

I think they just measure difference in stock balljoints to where the new pivot is like we do for RC correction. The one thing I've noticed with some drift cars and their horrible RC is it migrates a TON when your arms start getting away from parallel in a hurry. That's probably one of the things that makes excessively lowered cars go from feeling meh on turn-in to just horrible when they roll over as the RC is going all over the place.

[CodyAce]

See, I said that but they told me I was measuring it 'wrong' . Technically I am, but that's also where I began to question how they measured their correction...46mm?!?!? What did they do measure it in paint with pictures?

As before, my arms are level...it handles great.

[rioredstang]

Doesn't moving the inner tie rod pivot up or down change bump steer. Ackerman would only be changed by moving the the outer tie rod mount in or out. If you move the outer tie rod mount on the spindle out to were it is striaght inline with the rear wheel you would have 0 Ackerman. These bushings will only change bump steer.

[PoorMans180SX]

Doesn't moving the inner tie rod pivot up or down change bump steer. Ackerman would only be changed by moving the the outer tie rod mount in or out. If you move the outer tie rod mount on the spindle out to were it is striaght inline with the rear wheel you would have 0 Ackerman. These bushings will only change bump steer.

No sir, you've got it all wrong.

And Tower, this makes ackerman progressive, not digressive.

[Matt93SE]

Moving the rack up and down changes bumpsteer. Moving it fore and aft changes ackerman.

[CodyAce]

No sir, you've got it all wrong.

And Tower, this makes ackerman progressive, not digressive.


As Matt pointed out, you can reduce bumpsteer put putting the inner pivot of the tie rod and control arm on the same perspective/plane. This helps keep the out points in the same relative arc when the suspension moves.

And while it may reduce ackerman, do we really want that in a NRR sort of way? I'm yet to believe in perfect zero to negative ackerman being beneficial in our case of cars.

[Beejis60]

Take a look at the bushings. given the angle the steering rack bolts into the chassis, these bushings look like they move the rack upward about 1/4" don't they?

Ya, that's right. I just got done putting new rack bushings on my truck and they're straight, not mounted at an angle like the 240s... Should think a little bit more before speaking

[PoorMans180SX]

As Matt pointed out, you can reduce bumpsteer put putting the inner pivot of the tie rod and control arm on the same perspective/plane. This helps keep the out points in the same relative arc when the suspension moves.

And while it may reduce ackerman, do we really want that in a NRR sort of way? I'm yet to believe in perfect zero to negative ackerman being beneficial in our case of cars.

Technically it increases ackerman, and makes it progressive as opposed to linear. I have no idea if that's beneficial to a normal track car or not. I just want everyone to get the facts straight.

[CodyAce]

Technically it increases ackerman, and makes it progressive as opposed to linear. I have no idea if that's beneficial to a normal track car or not. I just want everyone to get the facts straight.

To me, being a progressive setup obviously means less change on the early side of movement, and more on the big end....so while it may reduce 'overall' I'd love to know the total change (and more importantly how much of a difference it is...I mean we can all claim for it to be a huge difference, but in relation to what.

Some of this stuff is getting to the point where it's a sales game, and I hate that bull****. We deal with vendors like that daily that promise all of these new things, and how much greater the new products are...but in the end of the game...how much better can it really be -- especially when the stuff he's calling junk has worked for so long.

[Umai Kakudo]

This is primarily used to fix over-centering on cars with shortened steering arms on the knuckles for driftastic high steering angle setups.

In the past others have modified the crossmember like this:

http://docrace.wordpress.com/2011/08/03/d-o-c-race-s13-update/
http://docrace.files.wordpress.com/2011/08/dsc00229.jpg

Or used offset rack spacers like this:
http://www.driftworks.com/shop/car-parts/suspension/steering/driftworks-geomaster-offset-rack-spacers.html
http://www.driftworks.com/shop/media/catalog/product/cache/1/image/9df78eab33525d08d6e5fb8d27136e95/o/f/offsetrackspacer.jpg

The other effect is the change in Ackerman at higher angles of steering. Drifting seems split into two camps. Some like zero or little ackerman to reduce scrub and slip angle of the trailing tire while others like ackerman as it helps the steering to self align and return to center with little driver input.

The PSM part in effect is re-aligning the rack for shortened knuckles to be more like OEM.

The PSM part is a new low cost bolt on solution that is limited in the amount of forward relocation of the rack versus modifying the crossmember.

Solid aluminum steering rack bushings make a tremendous difference in steering feedback and greatly reduces deflection in the steering system. I've noticed my Energy Suspension passenger side bushing getting sloppy (0.25" of free play easily moved by hand) after just one season so switching to solid bushings (Delrin or alloy) would eliminate that wear item.

I never like the offset spacer bushings as they substantially changes your inboard tie rod pivot point negatively affecting the bump steer curve and also puts offset load on the steering rack seals which accelerates wear on the rack and pinion bushings.

[sheltonsr]

The other effect is the change in Ackerman at higher angles of steering. Drifting seems split into two camps. Some like zero or little ackerman to reduce scrub and slip angle of the trailing tire while others like ackerman as it helps the steering to self align and return to center with little driver input.

The PSM part in effect is re-aligning the rack for shortened knuckles to be more like OEM.

The PSM part is a new low cost bolt on solution that is limited in the amount of forward relocation of the rack versus modifying the crossmember.

Solid aluminum steering rack bushings make a tremendous difference in steering feedback and greatly reduces deflection in the steering system. I've noticed my Energy Suspension passenger side bushing getting sloppy (0.25" of free play easily moved by hand) after just one season so switching to solid bushings (Delrin or alloy) would eliminate that wear item.

I never like the offset spacer bushings as they substantially changes your inboard tie rod pivot point negatively affecting the bump steer curve and also puts offset load on the steering rack seals which accelerates wear on the rack and pinion bushings.

Essentially, you believe this is a positive mod for a non-driftastic whip?

[Beejis60]

Essentially, you believe this is a positive mod for a non-driftastic whip?

Decreasing ackerman for road race is equally useful, just shytty for low speed, tight cornering, that's all.

[cazman]

Decreasing ackerman for road race is equally useful, just shytty for low speed, tight cornering, that's all.

In theory is could be good or bad.
The point is it's a car by car basis. Every different brand of tyre will react differently when you alter it's scrub radius. It would be a matter of trial and error if you were chasing lap times or tyre wear gains.

It's extremelly common practice over here to just cut n shut your knuckles to acheive a better steering ratio & alter our ackerman.

If anyone is genuinly interested in ackerman values then start up a thread/database.

To measure you need an angle finder/protractor and some duct tape.
With wheels dead ahead place a line of duct tape next to the wheels.
Turn the steering wheel 1/4 turn and place another line of tape down.
Repeat till you reach full lock.

Once you've done both sides you can just measure it and graph it on excel. Takes the guess work out when we build new knuckles.

If you have any incar footage of your car you'll see what your maximum steering lock is per radius/speed corner. From here it's pretty easy to gauge grip/turn in improvements once you change knuckles. (it's easier to build a few sets at a time with the cost of stock s13 knuckles in aus)

[sheltonsr]

Cool! Makes sense.

I know most people here probably aren't big on the PSM/PBM stuff, but the new "Pro Knuckles" look like they have incorporated features like the Driftworks knuckles! 45mm of Roll center correction and they're $500 i think (probably plus shipping them your old knuckles) which is about $130 less than Driftworks' price (don't know about shipping)

[Beejis60]

In theory is could be good or bad.
The point is it's a car by car basis. Every different brand of tyre will react differently when you alter it's scrub radius. It would be a matter of trial and error if you were chasing lap times or tyre wear gains.

That's a good point but I was stating that as a general rule of thumb.

Cool! Makes sense.

I know most people here probably aren't big on the PSM/PBM stuff, but the new "Pro Knuckles" look like they have incorporated features like the Driftworks knuckles! 45mm of Roll center correction and they're $500 i think (probably plus shipping them your old knuckles) which is about $130 less than Driftworks' price (don't know about shipping)

Note that the DW knuckles are their own design, not modded oem knuckles. Their knuckle "face" is flatter which automatically decreases ackerman.

[PoorMans180SX]

Their knuckle "face" is flatter which automatically decreases ackerman.

Please explain, this puzzles me...

[Umai Kakudo]

Essentially, you believe this is a positive mod for a non-driftastic whip?

Solid steering rack bushings are a very good mod for any performance car that doesn't need to worry about NVH issues. In the past the only option for off the shelf solid bushings were really expensive ($150) and JDM special order.

With shortened steering arms some sort of rack re-positioning is required to prevent over centering at max steering lock (or the steering stops need to be set up to limit steering prior to over centering but that leaves angle on the table).

The main disciplines that really need to pay attention to ackerman tuning are drifting and circle track.

For everything else it's a low percentage gain for those with otherwise sorted cars who need to find a few hundredths of a second.

For more good ackerman info check out the roundy round magazine articles like this one: http://www.circletrack.com/chassistech/ctrp_0407_ackermann_steering_system/index.html

[sheltonsr]

I bought the bushings yesterday. I have the rack out de-powering it and figured why not make it solid? $50 is too cheap not to.

[Matt93SE]

You took it out? Eff dat. I did it in 10 minutes on the car. (at the track. when it was 105F.. in the snow. uphill both ways.)

[cazman]

Poorman180sx
Assuming he means the tie rod mouting location is rotated so that it is closer to parralel to the ball joint:
it change the ackerman throughout the steering lock as the tie rod pivot (further down than the mount) is now moving through a completly different arc.
The tie rod will now point towards the front of the LCA/rack instead of aft

[sheltonsr]

You took it out? Eff dat. I did it in 10 minutes on the car. (at the track. when it was 105F.. in the snow. uphill both ways.)

Well, it's a bit hard to completely dismantle the rack and cut apart the inner seal etc. when it's in the car :D

Gonna do this: http://www.nicoclub.com/archives/howtoo-steeringrack.html
and see what happens.

[Matt93SE]

Screw that... disconnect the lines, then run the steering wheel from lock to lock about 15 times to pump out 98% of the fluid. then loop the pressure and return line back together. done. there's enough lube in there to keep the rack happy for years (going on about 4 years and 2500+ track miles on mine now).

[Def]

True, but you can't ever go back to a powered setup with that rack again. It'll leak like crazy, been there, done that.


I personally didn't like the car without PS. I could get around the track fine without it, but it was really hard to drive right at the limit. With aero and a ton of power I'm sure it'd wear you out in no time.

[Matt93SE]

Why would I want to convert back to power steering? I already cut the lines off and the main reason I converted the **** was cause my PS pump failed 5 min into my first run at the track and I had no choice but to pack up and go home (a $250 tow and $225 track entry fee wasted), or to fix it and salvage what's left of a bad track day. Btw, I only missed 1 1/2 sessions. I had the car running again halfway through the second session in my run group.

I have the aero and stickier tires than you're running (Running 245 BFG R1s now..), and I can drive for 2+hrs a day in the car without problems. Actually I feel better after a day in my car than I did in Dad's S13 w/ stock seat, belts, and power steering at Hallett.

Having the proper size steering wheel helps a ton too. people laugh at my school bus size wheel, but I can do a 3pt turn with no power steering and it's not an issue.

[Beejis60]

I have the aero and stickier tires than you're running (Running 245 BFG R1s now..), and I can drive for 2+hrs a day in the car without problems. Actually I feel better after a day in my car than I did in Dad's S13 w/ stock seat, belts, and power steering at Hallett.

Having the proper size steering wheel helps a ton too. people laugh at my school bus size wheel, but I can do a 3pt turn with no power steering and it's not an issue.

Also depends on the car AND if you depowered it properly, or just looped a power rack with no fluid drainage. I ran my Integra with absolutely no fluid in it, welded shut like the NICO instructions with zero issues with the K20 swap with 220bhp at 1900lbs.

[sheltonsr]

So maybe this is overkill...

Oh well, already out! Yeah i will most likely be running 255 or 265 tires, nothing crazy. Probably not R compounds. I'm sure it'll be more tiring and possibly harder to drive at the limit, but i've always felt like more road feel would make me more confident of where the limit is. Just a theory at this point.

Will be starting a build thread soon, and will report my impressions!

[Matt93SE]

I've found the car much easier to drive at the limit actually. You can feel exactly when you begin to push the front end too hard and the tires start to slip instead of turn.

Make sure you stay with a stock size or maybe a tad larger steering wheel and don't put too much caster in it and the steering effort stays light. Running lots of caster like our cars want makes the steering effort high due to jacking the front end up. If you fix the front end geometry with roll center correction/ control arms, you increase the mechanical grip so you don't need as much camber and caster to keep the front end stuck to the track.

So ideally you have to adjust your setup a little bit, but it pays off with less tire wear, less driver fatigue, and best of all better lap times. In the last 4 months, I've dropped lap times by 4sec a lap with what I've mentioned above.

[Def]

Why would I want to convert back to power steering? I already cut the lines off and the main reason I converted the **** was cause my PS pump failed 5 min into my first run at the track and I had no choice but to pack up and go home (a $250 tow and $225 track entry fee wasted), or to fix it and salvage what's left of a bad track day. Btw, I only missed 1 1/2 sessions. I had the car running again halfway through the second session in my run group.

I have the aero and stickier tires than you're running (Running 245 BFG R1s now..), and I can drive for 2+hrs a day in the car without problems. Actually I feel better after a day in my car than I did in Dad's S13 w/ stock seat, belts, and power steering at Hallett.

Having the proper size steering wheel helps a ton too. people laugh at my school bus size wheel, but I can do a 3pt turn with no power steering and it's not an issue.

Just saying I did that for quite a few track events and was not a huge fan. I drained the fluid then put a T in the loop going up to the stock PS reservoir which I'd keep cracked so it was like an open breather to reduce pressure. It's as low effort as you're going to get without yanking all the seals out.

The steering effort steadily built up right around the limit, and yes, it did feel like there was more front end feel, but there's absolutely no way you can make fast corrections with that much force.

I ended up delaminating the stock steering wheel rubber from the metal rim from the steering force, so I decided to go back to a PS setup, and I went faster after a small adjustment period. With a HICAS rack the steering effort feels pretty decent with 255/40's.

My steering effort near center went down when I added more caster recently. And also keep in mind more positive caster gives you more negative camber gain on the outside front, which is about the most important things our cars need.

[sheltonsr]

Good info fellas!

I have a stock steering wheel, so that ought to help, and since my rack was already leaky, i figure i can just buy a re-man rack if i don't like the "manual" rack.

[Tower240sx]

OMG i forgot about this thread and now theres just too much **** to sort through....

Messing with the ackerman on a car without knowing where you want to go or why is silly, granted.

All of my assumptions are based on the reading I have done as I haven't actually messed with the ackerman angle on anything yet, it's just hard for me to justify dragging a tire through a corner when I could have it following the radius it is actually being asked to follow...you're gonna need some really big words to convince me that it's somehow better to have the front wheels parallel or toed out in a corner when we all know they aren't following the same radius

[Def]

Ackerman angle makes your tires toe out as you apply steering angle.

"Dragging" is the wrong term to use, it just influences the slip angle of the tire. Your tires will dictate whether the unladen tire wants more or less(the usual) slip angle to generate its maximum traction relative to your loaded tire.

[sheltonsr]

Sometimes i fear i'm not smart enough to make my car fast...

Oh well i'll still have a good time!

[Tower240sx]

I think if you understand everything being thrown about you need to find a more complicated hobby....I take it as a good sign