Just eyeballing the amount of rear bumpstop you have, you could probably get away with even lighter (say 250lb/in) back there if you want to. 8" is a pretty short spring but I see what you're saying about the coilover sleeve. I'm surprised the suspension links are that limited in travel even with the shock removed!
If you don't have room for a longer spring, do you have room for a wider one? "Barrel" type springs can buy you a little more travel in the same overall length.
I am watching the suspension progress with great interest. Have a set of Megan coilovers on one car that came new with a parts car I bought, got running and flipped. The Megan's seem ridiculously stiff. Looking at putting Koni sports on the the other car with sleeves and springs similar to what you are doing. You spring rates you are considering seem close to what I thought was a good choice. Also I was wondering how you like the headlight beam pattern now that they're being used on a frequent basis. Enjoying your posts!
engiekev said:Luxury SUV towing a 90s rwd RallyCross car? Perfect!
Its going to be ridiculous! I always reach for that extra bit of automotive irony.
I'm envious of your new NB, I was eyeing that car, but SWBO wouldn't go for it without a soft top.
¯\_(ツ)_/¯ said:Just eyeballing the amount of rear bumpstop you have, you could probably get away with even lighter (say 250lb/in) back there if you want to. 8" is a pretty short spring but I see what you're saying about the coilover sleeve. I'm surprised the suspension links are that limited in travel even with the shock removed!
If you don't have room for a longer spring, do you have room for a wider one? "Barrel" type springs can buy you a little more travel in the same overall length.
I did have a look at the barrel springs, I was worried about clearance to the shock tower at the top, and the RUCA at the bottom. The OEM stuff is only slightly bigger in diameter than 2.5" springs.
Thanks for input on the springs, I really appreciate your opinion as you've been through a few iterations on this!
I've been thinking about the limitations of the 8" long springs, I think I'll run them for an event or on the street to see how they go. However, I also have access to a makerspace at work, and just signed up for the lathe course so I can machine a groove lower on the shock. With that lower groove, I can move the threaded section lower and run 10" long springs. I think that opens up more variety of spring rates without binding.
As to the limitations of the stock suspension arms, I think there's like 15% of travel that can be lost from bushing bind, but not a significant enough for the cost to chase right now. The road race guys will cram a few sphericals in the upright to free it up a bit of drag/travel. I think I can gain some travel easier if I switch to a raised eye-bolt style upper mount like you did in the rear. I think I'm losing about 2-3" travel at the top hat/spring seat.
Good luck at SnoDrift!
madmrak351 said:I am watching the suspension progress with great interest. Have a set of Megan coilovers on one car that came new with a parts car I bought, got running and flipped. The Megan's seem ridiculously stiff. Looking at putting Koni sports on the the other car with sleeves and springs similar to what you are doing. You spring rates you are considering seem close to what I thought was a good choice. Also I was wondering how you like the headlight beam pattern now that they're being used on a frequent basis. Enjoying your posts!
Thanks! I'm enjoying your thread as well, I need to copy that battery tray repair!
The folks over at NRR have played around with custom Koni setups for a couple decades now, if your shooting for a more track oriented setup, I'd do a bit of searching over there. https://www.nissanroadracing.com/forum
I had some Megan's on a Summer Beater Subaru GC coupe, they're terrible, throw them away! Or better yet, sell them to some kid who wants to live the low life and bounce around underdamped.
As for the headlights, the right light's up/down adjuster stripped out just before getting them aimed low enough. It's still waaaaay better, but a bit embarrassingly high to be driving around at night. So I've been avoiding night-ops.
Thanks, I will take a look at the koni info at NRR.
¯\_(ツ)_/¯ said:Just eyeballing the amount of rear bumpstop you have, you could probably get away with even lighter (say 250lb/in) back there if you want to. 8" is a pretty short spring but I see what you're saying about the coilover sleeve. I'm surprised the suspension links are that limited in travel even with the shock removed!
If you don't have room for a longer spring, do you have room for a wider one? "Barrel" type springs can buy you a little more travel in the same overall length.
You're driving at Snodrift? What car? Well be up there volunteering at control and will have to say hi at service.
This is really interesting stuff with the suspension work. I'll need to go down a similar path with the NB. There just isn't any off the shelf suspension packages (for any platform) that works well in RallyCross. Seems like a revalved koni or Bilstein with coilovers is the solution, getting the valving and spring selection being the tricky part. I'm working on some clandestine projects at work for this, we've referenced Dennis Grants calculators and info but they're not exactly suited to RallyCross. A RallyCross calculator would be neat.
http://farnorthracing.com/autocross_secrets16.html
In reply to engiekev :
Orange BRZ, number 986- come see us for sure!
For cars that can get them I'd say the Bilstein HD is a good rallycross shock choice in general, that's also a lot of people's budget stage rally shock of choice. Springs can definitely be tricky, the BMW guys are lucky in that respect since they can swap on springs from various heavier models, but generally speaking if you want a basic rate to aim for (wheel rate, actual spring rate is going to depend on motion ratios) I'd ballpark most stuff with this: [corner weight * 3]/wheel travel. Then do your motion ratio math, and fudge the rates down from there for various reasons- long bumpstops are a good way to get away with softer rates, or suspension with a more progressive motion ratio, etc. It also depends how smooth your courses are, but I wouldn't go much stiffer than that formula for rallycross in general.
In reply to rallyxPOS13 :
Thanks!
On the top hat/spring seat travel limitation, that seems like the low hanging fruit if nothing else is binding in that area. Looking at the photos, I almost wonder if the Miata mounts everybody likes to change out for more rear travel could be made to fit? Or even BRZ/later Impreza stuff looks similar and flatter. Want to measure the stud spacing on those?
All that said, it may not matter either- Panthera has bumps but if it's the main place you're planning to run you don't need big travel to do well there, it's just nice to have.
¯\_(ツ)_/¯ said:In reply to engiekev :
Orange BRZ, number 986- come see us for sure!
For cars that can get them I'd say the Bilstein HD is a good rallycross shock choice in general, that's also a lot of people's budget stage rally shock of choice. Springs can definitely be tricky, the BMW guys are lucky in that respect since they can swap on springs from various heavier models, but generally speaking if you want a basic rate to aim for (wheel rate, actual spring rate is going to depend on motion ratios) I'd ballpark most stuff with this: [corner weight * 3]/wheel travel. Then do your motion ratio math, and fudge the rates down from there for various reasons- long bumpstops are a good way to get away with softer rates, or suspension with a more progressive motion ratio, etc. It also depends how smooth your courses are, but I wouldn't go much stiffer than that formula for rallycross in general.
We'll look for you!
The other factor that plays into rallycross suspension tuning is tires: winter tires, re-tread (alpha or maxsport), or stage rally tires. The "spring rate" of the tire type varies drastically, re-treads are super squishy and similar to a equivalent sidewall winter tire, where stage rally tires are much stiffer. Though if the spring rates are too soft and nailing the bump stops already, a squishy tire isn't going to fix that issue.
¯\_(ツ)_/¯ said:In reply to rallyxPOS13 :
Thanks!
On the top hat/spring seat travel limitation, that seems like the low hanging fruit if nothing else is binding in that area. Looking at the photos, I almost wonder if the Miata mounts everybody likes to change out for more rear travel could be made to fit? Or even BRZ/later Impreza stuff looks similar and flatter. Want to measure the stud spacing on those?
Ooooh, that's a great idea! I was considering making my own machined from a flat plate, but I'm sure Nissan was using the same supplier as the other Japanese OEMs for parts like that.
In my continuing quest to use precision tools to take imprecise measurements:
The stud spacing is looking like ~81mm or 3.2"
And the central hole is coming in around 48mm or 1.9"
I'll post up in the general discussion here and see if someone has a set of those NB top hats sitting around. ya know, since Miata is always the answer.
In reply to rallyxPOS13 :
Looks like the Subaru stuff is bigger, with both the BRZ and Impreza coming in around 5.13" stud spacing. Fingers crossed that the Miata is closer, or maybe some other thing I'm not thinking of would work.
Edit: E30 is close but you'd need to make your own spring seat
Miata is approx. 5" stud to stud. 3" center hole.
Thanks for all the help with Top Hats, it doesn't look like there's an obvious solution, but I think I can work with what I have. The rest of my coilover parts have shown up, but with the 7" Allstar sleeves, I need to machine a groove in the shock further down, and if I can pull it off, I think I can get a 10" long spring. I've got an appointment with the guy that runs our work's Makerspace to learn the ropes on the lathe, should be in the next week or so.
Massive Distraction Testing
So one of the bubbles of the Ven Diagram that ended up with the Range Rover was a vehicle to do some exploring in West Virginia. SMBO and I are looking to purchase some mountain acreage to eventually build a retirement place, and a larger shop than I can cram into suburbia. It sounds simple, but it's a difficult ask: Comfortable interstate cruiser, handles on asphalt ribbons, can tackle gravel switchbacks, and even bomb around on two-track dirt roads that loggers cut into existence all while being a nice place to spend the day behind the wheel.
I have to say, the Velar tackled all of these things admirably. The air suspension and drive modes allowed it to quickly translate between gravel, snow, ice, and pavement, and we covered a ton of ground! I've always been a knobby tires and locking diffs kind of guy, but I have to say, a bunch of software and 40 series sidewall Conti DWS's got me everywhere I pointed the thing at.... strange new world.
Massive Distraction 2
Also foster-failed a puppy:
This weekend, I had a bit of a shock, when I realized the first event of the season is a couple weeks away! I got annoyed with and deleted Facespace again, so it's hard to keep in the loop on things!
So there were still a handful of things I wanted to update in addition to the rear suspension, so I rolled the POS into the garage to work on my welders tan.
First up I wanted to get rid of the Apex'i N1 exhaust. It's a 3" model for turbo cars, and had relatively low clearance to the ground. I replicated the design with some smaller 2.5" straight through mufflers:
And just so I can never find future leaks in my terrible welds.... sprayed it all black!
Another annoyance was the solid motor mounts that came with the car. It was literally rattling bolts off the car. Most of the options these days leaned quite a bit more to the solid side of things, or really hard polyurethane. What I wanted was the Nismo rubber mounts that are in the golidlocks zone of stiffness. However since I left 240land, the price of them has gone from $200 a set, to over $200 a pop. Some sleuthing online found some on eBay, but just the LH side. I was wary that they're fakes, as they were only $60. But comparing it with a new RH one, it seems to be of the similar quality (the black versus cad plating is normal for these, I assume to quickly tell if you're installing them on the wrong side)
We'll see if one rips in half before the other! I also replaced the dying (but <200 miles) 'Exedy' Clutch Master Cylinder, with one from Luk, and that and the motor mounts really add a great refinement to driving the car around!
The exhaust is just what I wanted, quiet at idle, lets a bit of rasp out in the higher end, a pop or two on the overrun, and never boomy.
At my age, it's hard to get firsts with the 240, but had one today $50 into an S13!
With prices on the rise, and the event a couple weeks away, I figured I'd top it up now... So I was dismayed when I got home that apparently topped all the way up, the tank leaks out the vent or pump, and dumped a few bucks on the ground:
Success! I need to do a few tweaks, but Version 1 of rear coilovers based off Bilsteins with 275# 8" springs are in. All the bits finally came in the mail, I hacked together the top mounts from various pieces laying around, and while it's likely sacrificing ~3" of travel, it's a million times better than what was there previously.
Took it for the test loop around the neighborhood, and it's soaking up bumps, but not too wallowly out back. I can fully commit to the throttle coming out of corners.
In the near future, I plan to create a flatter top mount, and it seems like this setup can take a longer spring, so V2 will integrate some 10" long springs, likely 250#. But I'll take them to the RallyCross first.
NIce progress. See you next weekend!
Thank you for sharing, long-time reader. Very cool project.
My parents bought an S13 new, and for a while we owned it. Cool cars.
irish44j (Forum Supporter) said:NIce progress. See you next weekend!
Yeah, I'm excited to back out at Panthera!
I had to double check that I registered for the right event, it only showed 6 people signed up!
David S. Wallens said:Thank you for sharing, long-time reader. Very cool project.
My parents bought an S13 new, and for a while we owned it. Cool cars.
Thanks! 
I enjoyed following along with your S13 back in 2013, while they're not as quick as Miatae, they're fun to drive. I recall an update where you were battling keeping rain out of the hatchback area. I was struggling with that lately, and as the car sits outside most of the time, I figured it was worth the cash for a new hatch seal:
NissanParts.cc carries all of the OEM rubber pieces for the sunroof, doors, and hatch/truck. Truly some sticker shock if you add them all to the cart at once!
We had quite the storm come through today.... and it didn't work. Next stop is re-sealing the taillights.
rallyxPOS13 said:irish44j (Forum Supporter) said:NIce progress. See you next weekend!
Yeah, I'm excited to back out at Panthera!
I had to double check that I registered for the right event, it only showed 6 people signed up!
MSR is being odd, it won't let me sign up for the season membership for some reason. But I'll be there.
Also, that's not showing the 17 people who have season memberships already (including NINE drivers in our class at the moment). So our class is already double-figured for the first event.
Another part showed up in the mail, some TC rods I ordered on a Black Friday sale!
In the 90s, Nissan started using large liquid filled bushings to take up NVH and do multi-axial flex. On the 240SX, the front tension rods have these on the chassis side. Mine weren't completely dead, but cracked and on their way out. So I preemptively ordered from SPL Parts. They're one of the few aftermarket vendors in 240-world that still manufactures parts in the US, and they're very well designed. However delays in the supply chain had these delayed ~4 months!
Slapped those on the car today:
Oh, and another set of 280ZX turbo wheels popped up for sale in town, so I couldn't help myself:
The car is so much smoother, it's downright easy to drive right now, and I'm excited to see how it goes on the dirt!
My list is short leading up to the event next weekend:
Oh, and the mutts were feeling left out today with all the garage time, so I decided to initiate the POS13 with some nose prints!
I'm glad I wasn't the only one wondering about the low number on the entrants list. Although, more runs is always nice as long as have enough to man the course...
Good luck with the changes to the S13, I hope it works better for you now. I did a quick oil change on my beater Subaru and it should be ready to go for Sunday. See you there!
Wow those SPL rods are beautiful! Glad to see you making good progress on the rear shocks too. Hope you next event is a lot of fun and problem free.
madmrak351 said:Wow those SPL rods are beautiful! Glad to see you making good progress on the rear shocks too. Hope you next event is a lot of fun and problem free.
They're just juxtaposed against the bent dirty suspension all around them 
But seriously, super nice adjusters, big FK Teflon sleeve bearing, and even a couple mounting holes for brake ducts. I also got the offset version that's allows for more tire clearance so I don't drag mud and sticks on them. SPL is good stuff!
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