creating new susp for the monster, going dual A setup front and rear Options

[byndbad914]

Car currently has RSR front struts with custom lower arm setup (sorta like a 935 front end) and the rear is a 5-link setup that is much like any old school 60s-80s open wheel car, GT-40, etc all attached to my tube chassis setup.

Decided I wanted to lower the car more and fix a couple issues with the rear 5-link geom so I started laying out some parts, then decided F it, time for a whole new update (IMG:style_emoticons/default/laugh.gif) I can't leave anything alone.

So I measured various available pickup points on the current chassis and whipped up this stuff in Pro/Engineer. The lower A is already a bit different than I have assembled in here, but close enough for convo - and JP was asking to see what I have going - I am sure so he can raz me about whether or not I actually win at DEs (IMG:style_emoticons/default/happy11.gif)

I used Pro to lay out the geometry so I could measure camber gain, get zero toe positions for the toe link (which will be adjustable in case I want to put some bumpsteer into the rear), RC height and motion, etc.


Is this perfectly optimal on all points? Hell no, but much better than what I have and works with existing structure - I am not about to really hack into this car. I can get tabs waterjet cut and welded into place, but not bending/notching tubes in my near future. Besides, it leaves me a little bit of excuse for why I am slow on the track cuz it certainly isn't my driving abilities hahaha (IMG:style_emoticons/default/driving.gif)

So here is the rear design - it will be built using the stock trailing arm cut down to not much more than a bearing carrier. yeah, yeah, use this other thing, make that, blah blah - the stock rear bearing assy has worked for a few years now so it is fine. I intend to replace that big bearing every few years regardless of upright used anyways.


I did the same layout stuff for the front and even am going to be able to use the exact same billet lower A front and rear so that is nice. I can have them waterjetted for about $170 each including the 1.5" plate material, so not bad at all.


I bought a couple front strut housings from Carquip last week and had my machinist buddy endmill out that monster weld so gonna work on getting them apart down to the stock knuckle, then I have 2" diam chromoly I just got yesterday that I will have him machine down to make the front "upright". Note the two surface colors in the above image - the blue is turned down to fit in the knuckle (50mm) and the green is the stock 2" diam of the tubing - that ridge will be used to exactly place the tube relative to the knuckle so I get both spindles left to right in the exact same spot.

The upper forward link will be made on the fly so I didn't bother modeling it. I need to get this stuff in the car with the right pickup points placed, then place some dual adjustable coil over assys which might be tough on the front, then build the forward link around the shock assy. At some point you stop fisting the design and just build it (IMG:style_emoticons/default/shades.gif)

Being a structural analyst I also have access to finite element code so I fully analyzed the lower A designs (I have 5 of 'em now hahaha) to make sure they are structurally sufficient. If I get off track in a big way I will likely bend them, but that you can't design for without having a 10lb A arm. These are just over 5 lbs per the modeling software.

[URY914]

I see. What about the angle of the dangle? (IMG:style_emoticons/default/biggrin.gif)

[byndbad914]

that is something I hold constant - low and to the left (IMG:style_emoticons/default/lol-2.gif) and just design around it

[SirAndy]

Purdy! (IMG:style_emoticons/default/wub.gif)

[J P Stein]

It looks like you have set up to get some decent scrub radius with a wide wheel from that design. Going with a cantilevered shock/spring?

Looks like a DE winner to me. (IMG:style_emoticons/default/smile.gif)

[ArtechnikA]

Tell me about the RSR struts, especially if they're about to be surplus...

(2,8 RSR clone/homage in progress...)

[byndbad914]

It looks like you have set up to get some decent scrub radius with a wide wheel from that design. Going with a cantilevered shock/spring?

Looks like a DE winner to me. (IMG:style_emoticons/default/smile.gif)

I would really love to move the spring combo inboard but unfortunately I can't in the rear, and since I want to keep the front and rear as identical as possible (so I don't have to carry so many spares, would only need one shock for any corner), I am going with a normal setup with the assy attached to the lower A.

I am gonna RULE at DE events JP (IMG:style_emoticons/default/lol-2.gif)

Tell me about the RSR struts, especially if they're about to be surplus...

(2,8 RSR clone/homage in progress...)

they were bought new from Pelican, are the yellow ones with the better valving and the 19mm lowered spindle. The stock RSRs are the green ones - suffice it to say everyone uses the yellow ones - yellow is faster (IMG:style_emoticons/default/laugh.gif) Here is a couple links to see what they are - Patrick uses them on pretty much all of the customer stuff in their photo album so I will use his site as an example, and Pelican where I bought 'em when I lived about 5 blocks from their shop (IMG:style_emoticons/default/smile.gif)

http://www.patrickmotorsports.com/part/1070/
http://www.pelicanparts.com/cgi-bin/ksearc...r=VE3-61017-M12

I have had them for five years but they have limited track time (one year of that was while I built the tube chassis for example) on them so they are for all intents and purposes like new. Interested?

oh yeah - thanks Andy (IMG:style_emoticons/default/smile.gif)

[ArtechnikA]

they were bought new from Pelican, are the yellow ones with the better valving and the 19mm lowered spindle. The stock RSRs are the green ones - suffice it to say everyone uses the yellow ones - yellow is faster (IMG:style_emoticons/default/laugh.gif) Here is a couple links to see what they are - Patrick uses them on pretty much all of the customer stuff in their photo album so I will use his site as an example, and Pelican where I bought 'em when I lived about 5 blocks from their shop (IMG:style_emoticons/default/smile.gif)

http://www.patrickmotorsports.com/part/1070/
http://www.pelicanparts.com/cgi-bin/ksearc...r=VE3-61017-M12

I have had them for five years but they have limited track time (one year of that was while I built the tube chassis for example) on them so they are for all intents and purposes like new. Interested?

Let's say I'm not interested at Patrick pricing ;-) ...

If you're dealing I'm interested.

Neither picture/source looks like the steering arm has been modified to compensate for the spindle - Do you use a bump-steer extended tie rod end, or is there a bend I'm not seeing?

Pelican lists two valving options - 220/100 and 161/160 - do you know which you've got? I have a set of RSR-spec inserts I had been planning on using but I'd have to go look at my notes to verify the valving numbers - they're not on the box anywhere I could see, although the part numbers are...

It almost looks like those are coilover struts - yes? I hadn't thought the 2,8's used coilovers but a quick check of Grüber's ,,Carrera RS'' book shows that they did, in a 'supplemental' role... Do you have the 'supplemental' coilovers? I'm sure the factory titanium springs are right out of my price range tho ...

I'm in no panic hurry to make this deal so take your time and think on what it'd take for you to part with them. PM or email me if you want.

[andys]

Tim,

Nice work. Any issues with roll steer on that rear design? I'm sure you already checked it out, but thought I'd ask. Keep the good stuff coming!

Andys

[byndbad914]

The angle and length I have set up in the design for the rear toe links is set at nominal zero roll steer. They will be adjustable up/down at the upright in case I want to tune in some roll steer depending on how the car is acting on the track. Everything is adjustable with this other than RC - that I can only mess with ride height but can't move the inner tie points. I have too much other stuff in the way on the rear to make that adjustable.

Art... it is late here just checking emails - I will work on a response for you tomorrow or Sat. There is a fair amount of history to cover to explain to you the difference between the two sets available but if I take time to explain it you will understand what you want. Short answer is I have the better 220/100 set.

[byndbad914]

so the whole coil over thing with the RSRs started because they couldn't get a stiff enough torsion rate so they added helper springs in parallel with the torsion bars to get a higher spring rate (the spring rates add when in parallel).

So the original RSRs had lower rate springs than you would run in a strictly coil-over setup, which is what everyone does now. Because of this, the rebound rating on the stock RSR is too low and also the compression was somewhat high (the 161/160 values) which is more of a question of dynamic roll, etc.

Anyway, Bilstein came up with the set that I have, and pretty much everyone uses now, which has the spindle lowered (for lower ride height without having to F up the lower A arm geom on the front) and has the better valving for working with higher rate springs. The better rebound value helps to control the higher rate spring while the lower compression lets the higher rate spring do its job.

That is as I understand it (IMG:style_emoticons/default/smile.gif)

I was plenty happy with the RSR struts but I really want to get my car low to the ground, so I either put them thru the hood or go dual A. Also, I am going to go to double adj shock valving and in case you aren't aware, those puppies are MONEY so I would rather just build a dual A and use "universal" shocks I can buy for much much less off the shelf.

If you are looking to have a good setup with fully adjustable ride height front and rear (you can buy rear adj height coilovers easily thru Bilstein, etc) and can corner balance the car, the RSRs are a great way to go for the money.

Art... I will PM you about my parting price and so forth.

[ArtechnikA]

So the original RSRs had lower rate springs than you would run in a strictly coil-over setup, which is what everyone does now.

Yes, because the FIA let them run coilovers but made them keep the torsion bars. When the 935's entered Group 5 they were free to finally pitch the torsion bars and run a full coilover suspension.

If you are looking to have a good setup with fully adjustable ride height front and rear (you can buy rear adj height coilovers easily thru Bilstein, etc) and can corner balance the car, the RSRs are a great way to go for the money.

no rear adjustable coilovers for 911 AFAIK ;-)

but it's OK - I am not building a true competition car - I am building a 'period-correct' 2,8 RSR without going crazy overboard trying to convince myself or anyone else that it is authentic. I don't mind a slight uprate here or there (i.e. front coilover rate) but I'm not building a car like we'd build it now, I'm building a car like I remember them. And I'll be glad to enjoy it like that, period-correct warts and all.

[byndbad914]

no rear adjustable coilovers for 911 AFAIK ;-)

I know you can get slip on threaded sleeves that fit over stock 91 rear shocks so you can easily upgrade to that in the rear... in fact, if you are doing simple upgrades here and there that is something you should definitely do IMO, and then in conjunction with the front RSRs you have a fully tuneable suspension for ride height and corner balancing, etc for the track.

[ArtechnikA]

no rear adjustable coilovers for 911 AFAIK ;-)

I know you can get slip on threaded sleeves that fit over stock 91 rear shocks so you can easily upgrade to that in the rear... in fact, if you are doing simple upgrades here and there that is something you should definitely do IMO, and then in conjunction with the front RSRs you have a fully tuneable suspension for ride height and corner balancing, etc for the track.

If it doesn't look like something they had in 1973 it's probably not going on.
But 911's have had adjustable spring plates for a long time (not quite 1973...) but it is a very subtle modification to the spring plate. Coilovers in back would be a big (visual) change but I'm OK with the spring plate mod. So I'm covered for height and corner balance.

[jmill]

Rebel has the RSR strut much cheaper than Patrick.

[ArtechnikA]

Rebel has the RSR strut much cheaper than Patrick.

Everybody has stuff cheaper than Patrick ;-)

You go there for the one-stop-shopping, or because you know they'll have what you need when some of the low-margin guys are outta stock when you really, really need something.

There's some stuff I see on their site I want, but I'll sure look for it elsewhere first...

[stewteral]

Tim,

Nice work. Any issues with roll steer on that rear design? I'm sure you already checked it out, but thought I'd ask. Keep the good stuff coming!

Andys

Hey Tim,

I'm with Andy: great design job. I know you've been working on it for quite a while.

The question I have is WHEN do you expect to get the new design in the car for the next track day? Has spring come to Colorado yet?

Terry

[byndbad914]

Spring in CO is a bit of a farce really - now is about the time we really start getting winter (IMG:style_emoticons/default/dry.gif) It was damn near 80 just three days ago, had a bit of snow last night, will warm back up, then who knows.

Last year in April I started a basement remodel since I thought it would be a good time to haul lumber in and out - we got 14" of snow the very next Saturday and I had a trailer full of wood. Two weeks later another big snow, so you really don't put any faith in the weather here, or least I don't, 'til sometime in May (IMG:style_emoticons/default/mad.gif)

All that said, I have the quote at the waterjet company being updated and hopefully have an answer on Monday - they called today and were a bit backed up so I told 'em Mon is fine. I am having every tab, bracket etc custom cut so I get everything exactly right - notice that every tab has a flat section on it that is parallel to ground so when I get the car up on stands I will set it perfectly level by shimming - then when I place the tabs I can just get them exactly level and the placement should be more accurate than a tape measure tho' I will of course double check the measurements before final welding. If I tell 'em to cut I should have everything pretty quickly - it will take them more time to source the material than to actually cut it as it goes so quickly once programmed.

The machinist that I am working with does it as side work at his job on the weekends and, unfortunately now that I am finally ready to go, his job has overtime work for the last two and next two weekends, so he has to do that. I am hoping to have most of the stuff to get started by the end of this month, if all goes well maybe be on the track in May when I can somewhat trust the weather.

[Brett W]

Have you looked at the 928 front uprights. They are cheap, already have good parts on them and easy to work with. I am going to use a pair to design my front suspension around. They save me a bunch of fab work. They use 5x130 hubs, 3.5in caliper spacing or even the late style Brembo mounts. Wheel bearings and other parts are easy to find and heavy duty enough for a 3400lb car. Beats redesigning the wheel.

Rest looks good.

[byndbad914]

looked at 'em - what I couldn't get good clarification on was whether I could use my 930 Brembo setup and floating rotors with them but it seemed like "no". So since I already have so much stuff based on bolting to the RSR struts that I have, it was easier for me to make an upright from the spindles. If I were starting from scratch on brakes and so forth, yeah, they would be really easy to work with and agree that you should try and make that work instead.

That said, I forgot to snap pix but I have two spindles off the strut tubes as of yesterday - just had to drill out the spot weld and press the tubes out (it took 7,000 lbs on the hyd press gauge to press the strut tube out!!) so I now have two nice spindles and the .188" wall 2" diam chromoly tube showed up last week, so my machinist is turning that down to ~ 50mm OD (takes .030" off the diam) and we are going to use a light press fit to ensure structural integrity and I will be welding them as well.

Tom at Carquip in Boulder here has been super nice to work with (where I bought the used 911 struts) and even ran the spindles over his hone to true up the strut tube diameter, so they are looking really good.

The stock strut tube wall thickness was around 0.140" and the new upright wall is 0.158", so structurally pretty similar and should be essentially impossible to bend - if I bend it I have MUCH bigger issues (IMG:style_emoticons/default/wink.gif)