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Daschj 11-24-2008 12:35 PM

H Stock legal upgrades

I'm a new owner of a '04 ZX3 2.3 PZEV and am considering upgrades, but want to keep the SCCA autoX H Stock class an option. We do have a local club and they do run some local (eastern Idaho) events. From preliminary studies I am aware that I must stay with 15" or 16" rims, can upgrade to some "R" compound tires, can upgrade the front anti-sway bar and bushings and can use any stock type shock, like the SVTs.

I'm in doubt about two other variables. There are no specific prohibitions about the mufflers other then the cat. Can I upgrade to a free flow type muffler so long as the noise level is acceptable?

Since the SVTs were an option in '04 could I use any other of the stock SVT suspension parts legally?

Finally, any experience based recommendation on wheel and tire combos would be appreciated. Also suggested alignment.

Thanks, In advance.

Adios, David

ajp 11-24-2008 12:55 PM

the svts are G stock so Im not sure about the svt suspension. check out the forums on, they have a section for these kinds of questions.

Dcl2049 11-24-2008 12:58 PM

I was under the impression that you have to use a stock wheel. I don't know if that means you can change them around at will based on all the different rims that there are, but I guess you could pick up some of the smallest steelies you could fit on those brakes. I race in street tire class so I'm out of the loop as far as R-comps go, sorry.

As far as the muffler, I don't know if I would spend any money there. I'm not sure welding a different muffler in would give you any measurable difference, and I don't know if they allow catback systems or not (still don't think you'd see much of a difference with all those cats, but I guess a catback would actually remove one so that's a no-no). If they make replacement high flow air filters for the 2.3 then see if you can grab one of those.

On shocks, someone correct me if I'm wrong but I seem to recall hearing how adjustables such as Koni yellows can be considered OEM replacements for stock class. You might want to look into those, as you can fine tune to match your driving.

It's been a while since I've read up on all the rules but I told you everything the way I remembered it. Good luck.

MyBlackST 11-24-2008 05:13 PM

As far as upgrade go to still play in "H" stock, you can do the following:

Air filter (not a CAI)
Cat back exhaust
Wheels - You can run any wheel that is the same size (width/diam./offset) as what was available on you model car. If you don't have a SVT you could not use those wheels.
Tires - street legal tires...."R" comps should be allowed in your region since they are DOT approved.

For more details to the rules, Check out Click on the SOLO tab and check out page 62 of the rule book.

Daschj 11-26-2008 11:41 AM

Howdy back:

Thanks for that info. Yes, I'm still reading and interping the SCCA rule book. Any advice or suggestions on a good tire for 16" stock type rims? "Good" meaning dual purpose street and autoXing.

Adios, David

Dcl2049 11-26-2008 12:03 PM

If I were you I would probably look for a set of steel 15's as those will have more choices available for tires and would probably weigh less (don't quote me on that part, but I think there's a sticky somewhere in Wheels/Tires with the weight of these). The sizes the Focus uses for 16s are kinda uncommon. I've seen people using Falken Azenis RT-615 on 15's which make a good street/track tire. They are more popular for Street Tire class though since Stock class can use R comps. There's a new Bridgestone Street/Track tire called the RE-01 that is supposed to be excellent.

ronnycage 12-22-2008 07:55 PM


Originally Posted by Daschj (Post 2461097)
Howdy back:

Thanks for that info. Yes, I'm still reading and interping the SCCA rule book. Any advice or suggestions on a good tire for 16" stock type rims? "Good" meaning dual purpose street and autoXing.

Adios, David

ok i joined for some h stock info and ive been heavily researching this.

Id run the hooiser a6's kumho 710s or victoracers. they are all good, they heat up quickly and they are good for dry grip.

tires like the yokohama a048s and bfgoodrich gforce and michelin sport cups etc... all take too long to heat up and respond at better at higher tire temps 160 degrees and beyond. by the time you achieve that temperature your runs are done. def look into a good auto x tire dont settle on azenis unless your on a budget.

16s in a 205 45 16 should do you or a good 205 50 15 I think should be fine.

street/auto x I feel the yokohama s drives or the azenis will be fine... if your serious about autoX pick up a second set of wheels and let it rip!

konis are legal as long as theres no more then 2 adjustments and im pretty sure just dampening and non ride height or spring pre load works. someone correct me if im wrong.

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