Installing an ERP 935 front suspension

[AlistairWallace]

Okay, so I will start with a few caveats. I am not a mechanic, suspension expert, or anything like that. Everything below is based on my use case and might not align with your expectations or opinions. Which I am fine with. I know some folks will disagree with installing aftermarket parts for street use. You are 100% entitled to that opinion, and I support your right to do as you wish with your car. This one is a long one, so brace yourself, I'll try to add as many photos as I can to the bottom with descriptions. Okay so now that I have dumped my disclaimer. The intent of this write-up is to share my experience with moving to the ERP 935 suspension (and a few other components). I am doing so because I struggled to get answers on the forums. Examples: specific measurements, weight, lengths (compared to stock) what comes with it, the difficulty of installation, etc. I choose to switch to the ERP platform due to a bent factory control arm, and my desire to tinker... I will leave the results of the installation to the end. What I was running:
1. Elephant Poly Bushings
2. Elephant Hollow 21mm Torsion Bars
3. KW V3 shocks 19 mm Raised Spindles (not Coil-overs)
4. Eibach swaybars

First I will go through what I purchased and installed, then for each part of the install, I will go through any struggles or things you should be aware of. What I installed
A. Conversion of KW V3 shocks to Coil-over - Note I could find a kit, so I built my own.

1. Elephant Front Extended Upper Perches
2. Elephant Spring Perch Adapter 2.25 -> 2.5
3. Allstar Performance ALL64143 Coil-over Sleeves - Note these require modification
4. Eibach 800.250.250 (250 lbs, 8 long 2.5 wide)
5. Eibach Coupling Spacer SPACER250 (Goes between mainspring and Helper)
6. Eibach Helper Spring (ERS 2.50 in. ID) - Maintains spring tension at full extension, no impact on spring rate
7. Strange S1409 Spring Seat Bearing Kit, - Ensures springs do not bind when turning (Sits at the top between Spring and Perch)


B. ERP

1. Porsche ERP 935 RSR Lightweight Front Control Arm and Cross Member Suspension Kit


C. SwayBar

1. Tarrett - RSR Style 21MM Front Sway Bar and Drop Link kit
2. 930 Front Sway Bar Nut Plate Adapter Set
3. Elephant Thru-Body Front Swaybar Reinforcement Kit - Not an absolute must-have, but since I have the entire front off, might as well
D. Seal-It - Assortment of Rubber Boot Seals for the Rod Ends - trying to keep dirt out.

1. RERS26PK, RERS36PK, RERS46PK - All from Summit

Coil-Over ConversionYes to answer your question I could have spent the money and bought the complete KW Coilover kit. But after talking to them, the shocks are the same inside, so I would not gain anything for the 5k spent. I purchased the parts from a combination of Summit Racing, Amazon and Elephant. Primarily to keep the costs down. The biggest problem is the Coil-Over Sleeves.
1. The KW V3 Shock body is 2.02 wide, which means you will not be able to find sleeves that fit over the shock and 2.25 springs. So I opted for 2.5.
2. The ALLStar sleeves have two ridges (rings) on the inside top and bottom that require being ground down. With a carbide bit it's pretty easy. A slight angle needs to be cut to allow it to sit flush on the bottom of the shock by the hub.
3. Yes you will have to cut off the factory Brake line mounts and fabricate a replacement (elephant sells one for 150 after the pains I went through to make my own, I would probably buy them the next time)
A. No other modifications are needed to shocks
4. Yes you will notice I have lower Steering Knuckle support welded to the shock to eliminate flex. It's not Elephants, I designed my own and had Send-Cut-Send laser cut it for about 30 bucks, then welded it on. and Yes, they work and make a difference, you feel less flex in the steering. If you want the DXF file to shoot me a DM.
5. The 2.5 springs are really close to my tire, If you place the helper spring and coupler to the top it makes it worse since the couple is wider than the spring. I opted to put the helper spring to the bottom.

[AlistairWallace]

ERP
1. No you cannot run factory Sway-bars, you have to run through the body style
WHY - you lose the forward most bolting point that's directly on the factory cross member
2. No you cannot run the factory skid plate, - I will have to find a solution

A. WHY - you lose the bolting point that's directly on the factory cross member
B. The Rennline skid-plate could theoretically work, but I don't like the fact that the main bolts for the Cross-member are used, Meaning I would be bolting through a soft Aluminum shield, through the Cross member to the frame. I am not comfortable it would retain its tightness. Yes, I bought one and returned it.

3. No you cannot run the factory Tow arms - My plan is to try one of the Rennline ones, but something for the future
A. WHY - they just will not fit

4. The Fuel pump mounting is impacted - Factory has two mounts - (Body & Cross-member)
A. There is no hole on the new cross-member, but you can still bolt it to the body.
B. I eventually added safety wire to keep it firmly in place.

5. The kit includes Wedge style Ball Joints, Installed.
A. No clue where I would get replacements, not even sure how they would be removed - They look custom to the arms

6. The kit Includes blocks to Raise the steering rack,
A. They are considerably higher than standard Rack Raising Blocks from Elephant or anyone else. (see photos below)
A1. Elephant - 10mm
A2. ERP - 30 mm
A3. If you take into consideration the difference in the cross member designs, it nets out to a 5mm difference. Meaning the ERP cross Member + their raised blocks puts the Steering rack 5mm higher than the Factory cross member with the Elephant blocks. See the photo below of the ERP cross-member next to the factory.

B. The reason for the difference is the ERP cross member is flat at the top compared to the OEM, which has a set of raised platforms for where the rack mounts: see photos below
B1. The difference is about 15mm

C. Using the blocks puts the rack much higher in total. So much it requires rerouting the factory fuel pump lines. By default, it is routed over the rack, but because the blocks raise the rack much higher it squeezes the lines. Its relatively easy to route them under the rack, but requires removing one of the hose mounts.


7. The kit comes with longer bolts to mount the rack to the Cross Member, but based on my measurements they are too short, feels like it only uses about 5 thread turns
A. The Elephant bolts that I removed are 56mm long
B. The ERP bolts are 60mm long
C. No longer have the factory bolts, but I know they are shorter than the 56mm
D. The depth of the hole in the rack (which seems to be threaded all the way) is 75mm
E. I opted for a 75mm long Socket Cap Bolt - it's 10x1.5 thread


8. The control arms have a Sleeve welded into them for the Sway-bar bolt. So therefore there is no u-Tab style Bracket
A. The Sleeve ID is 9.9mm
B. The bolt used in the sleeve is OD 9.7mm (10mm bolt)
B1. It's slightly short, so the shank cannot accommodate the sleeve, Bushing, and Rod-end 100%. So a few of the threads are in the sleeve when you bolt everything together. Making the entire thing wobble a little.
C. Tarrett Rod End ID is 9.9mm

9. Rod ends on the kit do not come with Rubber boots, I choose to use Seal-It
A. Part #s RERS26PK, RERS36PK, RERS46PK

10. Other measurements
A. Center Ball joint to center Ball joint
A1. OEM - 47 3/4 Inches
A2. ERP - assuming 1.5 times minimum thread engagement
A21. Min = 47 1/2
A22. Max = 48 1/4 (maybe a little more)- I choose to start at 48.
B. Control Arm Lengths from Pivot Points: Please note these numbers are very rough estimates. Remember your trying to measure from the center of the Ball Joint to the center of the Torsion bars. It may be off by 1/16th or so.
B1. OEM - 11
B2. ERP - 12.75

11. Surfaces - It is critical that you clean the mounting surfaces for the Cross member to sit flush. It is more precise in comparison to the factory cross member. There is a recess in the cross member that fits over the locating dowel on the chassis. If that dowel is not absolutely clean of undercoating it will not sit flush.

[AlistairWallace]

Some Random Notes
1. I ran the Rebel Racing Billet Steering coupler (one that connects the Steering Shaft Directly to the Rack) & the Rennline Billet Bearing (the one between the final u-joint and the Steering coupler) for a few months and when I went to remove everything at the beginning of this installation I noticed a few things.
A. The Billet Steering coupler had some scoring marks, which seems to indicate it was loose (which is wasn't). I suspect a misalignment may have been the issue.
B. The Billet Bearing was completely destroyed, The roller bearings were all torn to shreds.
C. When comparing the coupler to the standard Rubber join, I noticed it was about 10 mm taller. If you have a raised Rack and add this billet joint. I suspect it will create issues.
D. MY conclusion
1. The factory Rubber coupler and Rubber Bearing are there to provide some flexibility in the system.
2. I am considering adding another joint directly to the rack, but that's a winter project.


2. The Tarrett Sway-bar drop links are a little short for this application.
A. Keep in mind they are designed to be bolted to the top of the Control arm, which is about an 1 1/2 inches higher than where they bolt onto the ERP control arms on the side. They restrict the control arms from getting to full droop. A simple solution is a longer tube. I contacted Tarret and they are aware of the issue and can supply the correct length, cost was reasonable. (see photos)


Result
1. I always suffered from horrible bump steer, I was never able to dial it out. This setup solved it 100%. Even though it doesn't have the final alignment, it is by far soooo much better

2. Steering Feel
1. Much more direct and responsive than factory with Elephant poly bushings
2. No harsh feedback through the steering

3. Answers to a few questions
1. With all those Rod-Ends is the ride harsh - NO, I did not notice a drastic difference
2. With all Rod-End Based is the road noise more - Yes,
1. Noticeable on a really rough road (which I intentionally went hunting to feel and hear the difference).
2. The noise is transmitted through the Chassis, so you hear it down by your feet. Not banging, but its there. not enough for me to go back, but my car is purpose-built, not a daily driver

3. From an Adjustability standpoint, how is it.
1. I am running the Elephant Billet Upper Shock tower mounts, which are designed to give more camber and caster out of the box. The combination of this kit and the mounts may be too much, but I am finding it hard to get below 1.7 Camber.

2. Caster - Easy to adjust from camber plates and the lower Connections, you can dial in a ridiculous amount, so much so that it will rub on the front of the fenders

3. Camber - Standard Camber Adjustment above & you can lengthen the control arm. I was able to get as much as 2.5 degrees of camber. Nope, I'm not running that much, but I wanted to understand the limits. If anything reducing camber becomes a problem. I had to narrow the control arms to get it below 1.7 with the camber plates maximized.

4. Track Width Adjustability - It can be done, but you have to do some work - Options
A. Drop the Cross-member, pull the control Arm bolt then Rotate the Rod end (see photos for reason)
B. Disconnect the Pinch Bolt on the Shock, Disconnect the Sway-bar, Disconnect the Caster Adjustment rod, then rotate the entire control Arm.

5. Bump Steer: Drastically improved geometry over stock lowered. Relatively easier to dial out.


4. Was the installation hard? How long did it take
A. Not really, I took my time over a week and half to do it. Biggest delays - Note - it doesn't come with directions
1. Correcting Rack and Pinion bolt lengths
2. Cleaning the undercoating away
3. Drilling, Welding, Painting - for sway-bar

Am I happy? I did my first run in the mounts (Tail of the Dragon) a couple of weeks ago and yes, it performed well, even without the final alignment. So yep I am happy. Am I able to keep up with a good driver in a GT3? Nope But that's not my aim. Its a blast to drive.


Some other details on my car
Engine: Custom High Compression, TwinPlug, Motec EFI, 3.2 Short Stroke 240WHP.
Trans: 915 - Heavily reinforced with a Wavetrac

Note the fuel line routing is in the way




Note the Control Arm Rod End cannot be removed for adjustment without lowering the cross-member - You do not need to 100% unbolt it, loosen it a few turns and pry it down is enough. But its a pain in the a$$. Would have been so much better with one of those adjustment double nut things.






Note the Ball Joint is not a factory one. Not sure who I would ever get that out. Also open to the elements, so will require more frequent checks and replacement.

[AlistairWallace]

Pictures are worth a thousand words but the forum restricts the text length and number of photos, so making the best of it







Note the chassis needs to be very clean for the cross member to fit around the boss



Note the Tarrett Sway Bar links, the short one is the standard one, the longer one is required for running the 935 suspension



Yes my tires rub on the caster adjustment bar, but only at very full lock, so not that often.

[AlistairWallace]

one more set

[AlistairWallace]

Last Batch - Hopefully all of this helps someone some day


Brake Brackets that you will have to cut off, and grind flush




Note how the factor cross member rises up to where the steering rack mounts


Note the Steering Rack block fits into the cross member so it cannot move side to side, really nice workmanship.

[Evan Fullerton]

Nice write up! There are sooooo many of these “bolt on” parts that don’t come with any instructions or recommendations or acknowledgment of modifications that may need to be made to make it fit.

The only downside with 2.5in springs is more interference problems if pushing the limits on wheel offset and tire size. I have 1.5 degree decambered spindles which makes things tighter but to clear a 2.25” spring I need a 10mm spacer with 18x8.5 ET35 wheels.

[Tremelune]

Old 911 and an MGB...You gotta spend a whole lot more to beat that pair for fun motoring!

Useful writeup. I was wondering about this setup myself...

[Walt Fricke]

I see mention of consideration of perhaps adding another joint in the steering column. I'd be very careful about that.

When I fiddled with this, I cut out the middle of the long splined rod, slid a tube over the stub ends, and welded it up. However, I hadn't taken careful enough notice of how the two U joints - and in particular the flats at each spline for the securing cross bolt - related to each other, so the difference in degrees of how the flats related to each other was a bit off. The result was uneven steering. Turns out if you want to avoid having the far end of a 2 joint system turn at varying rates relative to the near (or steering wheel) end, first faster, then slower, etc., you have to clock them in just the right way, so the uneven motion at one end is canceled out by the uneven motion at the other end. Porsche had all that under control. Luckily, with a bit of grinding on one of the flats I was able to change a spline or two to bring thing back into register or whatever you want to call it.

Adding another U joint would call for changing this some, I suppose so the contribution of the second and third added together did the balancing, or something like that. Shouldn't be necessary. The tub limits how much you can raise the rack up - too far and it hits the tub. But with raised spindles and adjustable trailing arm end height you have a lot more adjustability than just moving the rack provides.

[AlistairWallace]

Originally Posted by Tremelune

Old 911 and an MGB...You gotta spend a whole lot more to beat that pair for fun motoring!

Useful writeup. I was wondering about this setup myself...

Yep they are both a blast to drive. Might be sacrilege on this site, but sometimes the MG is even more fun on the back roads. Slow as bleeep but fun trying to maintain any form of pace

[AlistairWallace]

Originally Posted by Walt Fricke

I see mention of consideration of perhaps adding another joint in the steering column. I'd be very careful about that.
..............

Yep I agree, my plan is to mimic the SRP one but with splinned joints so that I can clock them correctly. Flamming river has some pretty good instructions on how to do it.

[Evan Fullerton]

Originally Posted by AlistairWallace

Yep they are both a blast to drive. Might be sacrilege on this site, but sometimes the MG is even more fun on the back roads. Slow as bleeep but fun trying to maintain any form of pace

I also have a MGB GT……. A 3.4L 60 Degree Chevy V6 warmed over a bit fixes the slow……. but points out other deficiencies…… mainly brakes and lack of chassis rigidity.