996 as an ice car

[cockerpunk]

for those of you not familiar, the most fun racing season of them all for me, is winter. because lake racing is the most fun you can have. and i've spent years doing this, and built an almost perfectly suited NA6 miata for the task.

can be enjoyed visually below:

https://www.youtube.com/watch?v=Y12Rbuj3E2M


ice racing on studs is a unique motorsports situation. i do autocross, HPDE instructing and wheel to wheel club racing, and the issues with cars etc are well understood, but the issues with racing cars on the lakes are much more niche, and not well understood by the broader car world, and thus lead to some pretty strange questions.

the unique problems start here:

Suspension and tires:

We (I) make bolted studded tires. these are 5/16ths inch starpened bolts. they go through the tires, from the back side, and provide insane grip. with a aim solo or other datalogger you can generate 1.1ish G lateral grip on these tires. generally the more studs the more grip, as a resualt, there is a rule locally as to your tire size and the number of studs you are allowed to have, to keep the playing field level.

so you are generating 1+ G lateral grip. and this is a bad thing for the cars.

because ice is not flat. the lake is covered with bumps ranging up to 1-3 inches high. and you are sliding across these bumps at 10-30 degree slip angles. and the rear wheel bearings in particular get beat to hell. miata's are well known for having weak front wheel bearings, but my NA6 kills rear wheel bearings pretty regularly. the front wheels are of course turned into the slide, the rears are not. the rear is also usually at full compression, riding the bump stop (more on this later), and so the rear wheel bearings are beat to hell.

ok, so what do you do about that? well, what i did was stiffen up the suspension to about double the stock spring rate, add stiffer and longer bump stops, and i run a koni shock with almost no rebound, just compression damping. this prevents the rear end from "jacking down" and keeps the energy from the bumps being absorbed by the spring/damper, rather than going directly into the hub when the suspension is fully compressed.

ideally, for speed, i think lower is better on the ice, but i tend to run near stock ride height (6ish inches to pinch weld) on the miata. raised cars handle like junk and not considered particularly serious competitors on the ice, at least in this world. so i would not want to raise a different car beyond 6 inches.

so, all this is to say, the rear wheel bearings and suspension is very important.

Engine:

cooling is a major issue. in certain conditions the amount of snow you intake can be a major issue. not just for blocking airflow, but also in that it melts, and then refreezes. i've had to go to hood pins for example because the whole front the car is so full of ice that the hood latch was frozen closed. ive also had the headlights freeze closed. so how the front of the car deals with this is important. generally ive gone to a no undertray policy, because id rather the snow and ice fall back out of the engine bay (front engined car remember), than keep picking up snow/ice. engine bays fill with snow and ice, and that too can provide issues for fans, belts etc.

so not having a car to look at right in front of me, id love to hear about how the front radiator and oil coolers are mounted.

also does the car have an oil cooler? how is it mounted?

an oil cooler is important because unlike road racing or track driving, the car spends most of the lap a WOT but at relatively slow speeds, and at high yaw angles, so airflow can be quite restricted. so oil temps can be an issue.

also on the engine front, power mods basically are not important. need that stock engine tune so it will start at -10 degrees F.

Differential:

LSD is critical. ive tried every diff made for a miata basically at this point and i have gotten rather good at rebuilding, switching etc diffs. sadly, on porsches, LSDs are rare. so i would have to swap one in. i've googled how to do this, and noticed that the procedure said nothing about setting backlash or preloading bearings or anything. thats kinda scary if true. how, in the transaxle is this done?

4wd?:

no.

if i wanted a 4wd ice racer id buy an evo and run circles around any porsche made for pennies on the dollar. the entire point of looking at porsches is the rear drive rear engine format. in the 4wd world there are so much better cars that a 911 and for so much less money. bottom line not interested in 4wd.





so ... this leads me to my questions:

1. rear wheel bearings ... how expensive? how easy to swap? how tough are they?
2. ride height ... how low is stock? what is the stock spring rates? how much clearance is there for studs?
3. engine cooling ... what does the front of these cars look like? oil cooler? radiator mountings? what kind of cladding is around them?
4. diff stuff ... how would i adjust backlash and preload? otherwise how easy is a differential swap in the transaxle?

any other issues you might see with the car on the lake?

Does anyone know a place beside copart to buy junker 996s?

i also could be interested in lighter 986/987 boxsters or 987 cayman.

pics for clicks:

[JTT]

Damn, that looks like fun! I used to do it on motorcycles and it’s such a blast.

As for your questions;
1. rear wheel bearings ... how expensive? how easy to swap? how tough are they? Seem pretty strong. I’ve not had to replace so not sure on complexity or cost, sorry
2. ride height ... how low is stock? what is the stock spring rates? how much clearance is there for studs? I’d suggest you will likely be OK as stock ride height. Lowered 2” leaves plenty of clearance with stock size tires/wheels.
3. engine cooling ... what does the front of these cars look like? oil cooler? radiator mountings? what kind of cladding is around them? Rads are located at the sides, in front of the front tires, in an angled arrangement. Air is ducted to them. AC condensers are piggybacked on the rads. There is no protection in stock form, although many use screening across the opening in the bumper to protect from debris being caught up in there. Intakes are very vacuum cleaner like, and I’d suggest would scoop up lots of ice, if you were following someone.
4. diff stuff ... how would i adjust backlash and preload? otherwise how easy is a differential swap in the transaxle? Sorry, can’t help here.

[cockerpunk]

thanks for the radiator information. sounds like something id need to look into. ducts tend to fill with snow and ice, and then you get no airflow. so not much a fan of ducted coolers.

[cockerpunk]

well, this is happening, so stay tuned for strangeness.