Adjustable Control Arms, take 2

[76ohtwo]

these look awesome. come time for round two, might very well be interested in a set. excellent work man

[mttpekin]

Wow. Thank you guys. Been pursuing this for a while now so thank you. I first drafted a model of what would become these in 2018. This is lookin a little better than my first go at it..

 

Tension arm clearance at subframe was insufficient the last 1/2" of travel to full bump. That area up there is tight... I went thru 5 iterations of gaining clearance via offsetting the axes of the tubes where they cope together. That would've been ok but not optimal nor pretty so I redesigned the front bushing arm connecting piece and my machinist will have these done $tomorrow$. A little eccentric spinning. This will make more sense when I get on car and photos of installed & cycled. Getting quite close to having a dialed drivable prototype. 

The first little boss is the diameter of the flat portion of the dished washer. holds that washer flat and off the large 'lollipop' 

 

14 hours ago, Super Fahrt said:

Matt, are you planning on selling there’s more broadly?

Ultimately yes. That's more a goal than a current obstacle though.

 

I'd like to support/build these indefinitely. I've been a faq member since I was 17, 11 yrs ago, and don't see this obsession passing anytime soon hah. I'd love to be one of the guys who provides really good stuff. I'm going to do my best but just gotta see how this goes I guess. I hope to own most of the machines to build these types of things fairly shortly. Drinking from a firehose comes to mind.. If you have ideas, I'm all ears. Please PM. 

 

 

19 hours ago, scott-o said:

I'm sure there will be plenty in the UK interested in these as well. I've seen lots of home brew efforts but nothing with so much thought and geared towards hard road driving! 

Hmmmm a UK 'business trip' that involves tricking out 02s.. twist my arm. I've gotten interest from Canada and the UK already which just makes me super stoked. 

 

Depending on timescales, count me in (if postage to the UK is available, potentially a group buy on the cards to combine postage if it makes it any better for you as well) It sounds like future batches are a small while away? Will follow for updates.

Thank you. And yes. I am going to get materials on order as soon as I've dialed in my car and am thoroughly happy with all aspects of these. Following for updates is the best way to keep up. I'll post significant updates as they occur and I'm working hard to get things moving. 

 

14 hours ago, Lorin said:

Is it as it appears to me that the caster would change with camber adjustment? If so, is the caster adjustable on top of compensating for the camber setting? The window of available caster seems like it would be different at 0 degrees camber than the window of available caster at 2.4 degrees camber.

Lorin, the adjustment range changes as camber is adjusted. I've modeled this but quantifying meaningfully via cad is beyond my capabilities. I've simulated the suspension going up and down thru its travel and the camber/caster adjustability but then you have to somehow export relevant data during those simulations and all variations thereof. That's not particularly trivial.

 

I did spend a solid bit of time yesterday working out measuring caster accurately.. I will have insight here when prototypes are mounted. This is looking like early next week. The prelim data I've collected on these by the ones mounted on my car are set at -1.2deg. Half way 'out'. I've not dug deeper as I changed the subframe mount per ^^^ and am awaiting the hopefully 'final' arms. 

 

I believe I've replied to all PM. I will update as soon as on car. Thank you again for the feedback as well as future patience. Pit limiter is off, hammers down, still takes time...

 

Best,

MP

[scott-o]

Great stuff, thanks for the response, Matt. Will keep watch!

[Rich Hall]

Hi Matt,

 

Interested in a set

 

Rich Hall

[mttpekin]

Hi all,

 

This was a pretty fun weekend. I made some parts in 3 days that'd usually take 2-3 weeks.. 

The offset bushing interfacing piece came out really nice^^. The first boss holds the concave washer much nicer than the prior version.

(if you've spent time on the CA central coast, hopefully you're familiar with KPIG)

 

Fabricated revised arms. Top picture shows how the tension arm tube meets with that offset lathe part. 

 

A good part of a day of measuring had me pretty confident that they'd clear at full bump. It's definitely quite tight up front but, they clear the subframe with zero subframe modification. That was my goal. 

 

stock ride height ^

 

Tension arm clearance at full bump^

 

full bump ^

 

 

This currently has the camber at -1.3° and 4.08° caster. Matt's Alignment has been in business for 1 day. Setting up an accurate, repeatable measuring system took some time but I am pretty happy with the result. I will be dialing this setup in over the next couple days. My wheels are the e21 et13 mahle and are the wrong offset. I really like how these wheels look but they dont really work. I've been playing today with the stock spare wheel and it has lots of clearance.

 

For a working prototype, these have turned out nicely. Production versions will be optimized slightly. They cycle smooth and have given me the adjustability I want. I am pretty happy with them right now.

 

I will be reaching out to everyone who's expressed interest thus far next week as I better understand production times.

 

Thank you! 

 

Matt 

 

P.S. Disregard the dirty subframe/engine. I cleaned it a bit and got it running well but haven't pulled engine/dropped subframe as I don't know if I'll be staying with an m10 on this one... 

 

Edited April 1, 2021 by mttpekin
clarification

[Ian]

Looking good!

 

Looking at the design, it looks like you now have an offset bushing at the tension arm at the front of the car to space the tension arm down and away from the subframe.  What are the chances that vertical movement of the main control arm could cause the offset bushing of the tension arm to rotate in its fixture, causing binding or rotating the bushing so the tension arm interfered with the subframe?

Edited March 30, 2021 by Ian

[mttpekin]

3 hours ago, Ian said:

What are the chances that vertical movement of the main control arm could cause the offset bushing of the tension arm to rotate in its fixture, causing binding or rotating the bushing so the tension arm interfered with the subframe?

edit: Clarified original post. Original verbiage said 'offset bushing' the bushing is still concentric and off the shelf Powerflex. The chromoly lathe part that interfaces with that bushing is eccentric now (pic1 on that post). This allowed me to gain critical clearance and still use all off shelf bits.

 

Ian, the poly bushings allow the arm piece to rotate inside that bushing by design. There is a smooth piece of tubing that rotates inside that polyurethane. This is unlike the rubber stock bushings that are torqued at ride height and all articulation is handled by rubber deflection. The bushing itself is not offset, just the plane which the tension arm tube meets that 'lollipop' as I've named it. The upper limit of that rotation/deflection was what interfered with the initial concentric metal piece and is solved with this one. I currently cannot envision a situation in normal operation that'd interfere/bind with these. I took spring off and cycled the whole suspension by hand. It is smooth and doesn't interfere anywhere. I want to setup a gopro and watch these in action before long.

 

Edited March 30, 2021 by mttpekin

[MOESPEED2002]

Matt,

 

These are looking very proper.

 

Since these are mocked up on an oem car. Whats the chances you can get them fitted on other variants. A good example is the IE swaybar kit which many use as a std upgrade. They relocate the swaybar under the subframe with a block. The swaybar is very close to the tension rod in their setup. Thus would be concerning now that you have moved the tension rod down a little due to its diameter being larger than oem.

 

The added length from the bushing will be in close proximity to the block also. Just guessing though. If you need other pics maybe with clearance dimensions, my car is on jacks at the moment.

 

Thanks

 

Side note: I like the raw steel arms. I just might want mine cleared instead of black or any other color.

 

Moe

Edited March 31, 2021 by MOESPEED2002

[mttpekin]

22 minutes ago, MOESPEED2002 said:

The swaybar is very close to the tension rod in their setup. Thus would be concerning now that you have moved the tension rod down a little due to its diameter being larger than oem. The added length from the bushing will be in close proximity to the block also. Just guessing though.

Hi Moe, The tension rod on these arms follows very near the stock arms route. There aren't really too many options here haha. It's quite tight... The tension arm connects to the control arm the same distance from the ball joint as stock (if you measured from ball joint to where the tension arms axis intersected the lca arm axis) 

 

The mentioned swaybar mounting block remains below the 'peak' on the subframe in my picture below. I don't have one of those so I can't be positive but just based off your pic, I believe these would perform fine together. 

 

[MOESPEED2002]

Matt,

 

Right on! That looks like it will clear even with the large tension diameter. Tight but clear.

 

 

Excellent!!

 

I also measured clearance between the swaybar and oem tension rod. I have 7/16" or 11mm at full droop for me. About 5/8" or 16mm at ride height. FYI.

 

Thanks

 

Moe

 

 

 

Edited March 31, 2021 by MOESPEED2002

[Ian]

Matt, terrific work!  I look forward to trying these out on track.  

 

However, I am still a bit concerned about the offset tension rod rotating under hard braking on track and altering the suspension geometry.  This kind of dynamic change could in theory change toe in the middle of the turn.  Do you have a pic of the original tension arm interfering with the subframe?  

 

I'm wondering if a better solution might be to clearance the subframe so the tension rod can swing through a single arc to alleviate any concerns about dynamic changes in suspension geometry.

[mttpekin]

On 3/31/2021 at 6:59 AM, Ian said:

Matt, terrific work!  I look forward to trying these out on track.  

Thanks!

However, I am still a bit concerned about the offset tension rod rotating under hard braking on track and altering the suspension geometry.  This kind of dynamic change could in theory change toe in the middle of the turn.  

I thought about this for quite a while. In theory, yes it could. Also in theory my numbers came out to .045" lateral travel of that bushing piece over 2" of travel. That number is inaccurate because it doesn't take into affect the amount of that taken up by bushing deflection. Also somehow you'd need to resolve this into an affect on the control arm swing arc and then relate that to the differences in steering arm arc change. Theoretically this is hard. Luckily I have a laser and a car on blocks and can go cycle the suspension and directly measure toe. I'm itching to drive the thing.. 

Do you have a pic of the original tension arm interfering with the subframe?  I'm wondering if a better solution might be to clearance the subframe so the tension rod can swing through a single arc to alleviate any concerns about dynamic changes in suspension geometry.

This was my original plan. Clearancing the subframe would be slight. My estimate is around 1/8" removal/displacement from the contact point would do. I also don't think that it'd contact often under normal driving. I went through this trouble because I know some guys don't want to grind on their subframes / a 100% bolt on modification. This picture in red is the only place you'd need to clearance slightly. Purchasers will have the option for concentric bushing interface parts. Mapping toe will give me a good idea. I can also envision using this offset idea as a tuning tool. Currently I believe that this will have a very slight affect, if any; or less than the affect of the adjustability these allow. 

 

 

Edited April 1, 2021 by mttpekin

[Ian]

That looks great!  Removing that small bit of subframe would be fast and easy.  This non-offset option will alleviate any on-track concerns.  At least it does mine!  And I suspect anyone buying this type of part isn't particularly worried about total originality. 

Edited March 31, 2021 by Ian

[mttpekin]

5 hours ago, Ian said:

That looks great!  Removing that small bit of subframe would be fast and easy.  This non-offset option will alleviate any on-track concerns.  At least it does mine!  And I suspect anyone buying this type of part isn't particularly worried about total originality. 

Makes my life easier, and now people have more options... I am set up to make both.

Thank you guys, MP

 

[Ian]

I think the areas that might need trimming are marked by the red arrows in this pic, correct?  Those flanges can be trimmed.  I "might" have removed some of the flange already...

Edited April 1, 2021 by Ian