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Had a little issue with the math. Wheel rate is Kspring*MR^2 To solve for the rear spring, assuming 50/50 weight distribution.... I think it is Rear spring = ( <Front spring rate> * (.57^2)) / (.89^2) So for a front spring of 550 I'd get a rear spring of 225 This math scans with what Loren recommended

Yes these spring rates for the wcm are way stiffer than caterham. 2x stiffer I am using the advice from westtexass2k who ran 550/250, apparently, based on his prior posts here. I can only assume the force/motion ratios are way different for the wcm vs caterham. Goal is to set the car up for road racing. Arb, springs and dampers will all work together to address this excessive body roll but right now I'm just considering the spring rates Here are some pics of what looks like too much body roll and how I took the angles. Not totally convinced this body roll is bad but it looks a lot different from super 7 race cars that are not as rolly

Getting back to this. My car can only fit small body shocks and springs. I think that other wcm ultralights can fit bigger outer diameter springs, but if I tried that they would interfere with the rear axles. So I believe I am stuck with 1.875 id springs and small body shocks. Small body shocks get expensive quick. Here's what I am thinking based on those motion ratios above. To get the wheel rate equalized front and back. We're going to need a slightly softer spring in the back. From looking at the forums it looks like some folks have got a lot softer in the back than I would if I were going for a balanced setup. Maybe there are other reasons to go softer in the back. So .57 / .89 = .64 After lots of searching, the stiffest spring I can find is a 600 hyperco in a 1.875id x 10 inch. These seem rare! Other makes stop at about 400 lb/inch 600 * .64 = 384 The car is slightly heavier at the back so I'd go up to 400. Softer setup could be 500 / 350 Shocks - that I don't know. Qa1 suggested these but they aren't adjustable 8Q45. I think that my setup is relatively close to this at 500/500 and the qa1 small body shocks that came with the car. I don't think I will invest in any changes yet and focus on driver training. @charles5448 Hyperco part numbers for their 1.875 id 10 inch long springs. This is the best set I've found and mostly seems available from summit etc

MR for front is approximately 0.57 MR for rear is approximately 0.89 Info used: Front: 0.81 * cosine (45) = 0.57 Rear: cos(27) = 0.89 D1 - 10 7/8 D2 - 13 1/2 D1/D2 = 0.81

Motion ratios incoming! I will measure the actual distance traveled Not sure if this will be the same for all wcms but maybe a useful reference

Hello, does anyone have the motion ratios for the wcm on hand? I'm trying to be scientific about my shocks and springs setup for next year

Also you need to put some ballast in when you set the ride height. Measurements above are with no driver weight.

134mm and 99 mm taken at the blue tape marks. Note that this might not be so useful because it's measured with the street wheels which has a much larger rear vs front. 225/40/17 vs 245/40/17. Race setup is all 245/50/15 Race setup was used to set the ride height and that was a difference of 15mm front to back. Front was set first to give the oil pan enough clearance. Thank you @MV8I am now pretty sure there are cut down 500lb springs. I searched through summit racing and other places. The only 1.875 id springs that are 500 lbs are 10 inches long. My car was ran a lot lower prior to me getting it, so they probably had to cut the springs down All starting to make sense

I ran some similar calcs based on the wire size and got that too. However, looking at what qa1 sells in this size shows the lighter springs. Mine sure look like these ones https://qa1.net/springs/1-7-8-inch-id/

Tire pressure in the back? I run around 20psi. Toe in the back, camber?

I've been looking at my springs a little bit more today and they are 1 7/8 inside diameter. So I think they might be 150# !! Already have some calls into different places to get some heavier ones. I think mine are waaay too light. Thanks for asking I might not have investigated. I think your setup sounds pretty good- it's what others have had success with. What diff are you running? I have a line on a good deal for a WRX STI r180 which could be a huge upgrade. I did it recently What's your rake? My car started out with tons of rake and I leveled it out. Now it's 15mm difference front to back. Started like 40mm That setup was causing mid turn, power off oversteer

Same setup in the back. I guess you are probably pretty close either 250 or 300. I believe 300 was the baseline setup for a lot of these cars. Some wcm people put heavier springs in the front, but the balance of the car is heavier in the rear. So I would think if anything heavier springs would go in the rear. I think the real solution is adding an anti-roll bar. Anti roll bars would be a fantastic add.

I measured 11mm

I've sent qa1 an email to see if there is any way to identify these springs without taking it apart!

Not sure what my spring rates are but would love to find out. I looked for markings on them but can't see anything. No front roll bar.

Charles I have spares here both front and rears. If you wanted to borrow one to get it duplicates im sure we could work something out. Alternatively as someone suggested some fiberglass or cf replacements would be cheaper and probably a nice weight savings....

First thing I did that day was loop it in that exact spot!!!

I want the electric one, but my $$$ is all tied up in the WCM

I watched this race and it was awesome to see the yellow super 7 out there. I think the solution to some of the objections to the SCCA handicapping these is to run a different classification. This is something I've advocated for in a different thread. An inclusive classification for many different types of super 7's would be incredible

It was a very fun day indeed. Beautiful fall weather out there, and the property is wide open like a park. The dark black asphalt was very slippery in the morning then got better in the afternoon. I decided to go with Toyo R tires for my track setup and they don't work so well until they warm up. The 7 was keeping up with some heavy metal out there for sure but the aero penalty kicked in severely on the long straight away there. Drag coefficient is about 0.7 vs. 0.3 for your average sedan. That makes a huge difference over 80mph. Top speed I saw was 118 at the end of the front straight away. Another nice experience was taking the wind screens off and running helmet to the wind - that definitely added to the experience....

Here is an example of some pretty lousy driving as it was my first time out at Grattan raceway. I found this race track a little bit hard to master because there are so many turns that are blind. First few laps coming into them my thought process was.... is this going to be a left or right hand turn???? scary stuff! Especially combined with the cool, slippery conditions in the morning on this fall day. But after lunch it was a little easier.

Hello WCM owners, I have a line on a 2004 WRX STI differential. I did the swap a couple weeks ago after breaking the original WRX r160/ diff pinion This deal came through after my swap was already completed, but it is a much better deal than I got so thought I'd throw it up here Details -seller is asking $700 -images I saw of it looks very nice -2004 STI (only model year sti with 5x100 bolt pattern) -R180 -plated, 3.9 final drive ratio This one is hard to find... If you have the wcm, you should strongly consider it. Along with the diff you will swap the axles, knuckles, hubs. The pickup points on the STI knuckles are the same - my alignment didn't change hardly after this. You will end up with a much stronger, less compliant rear end than the r160 and base WRX parts the car comes with. Also you will get a fully blown mechanical LSD @RGTorque @Bruce K

Here is a video from today at Waterford Hills Road Racing. I got it under 1:15 before the differential broke

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