Wheel/tire discussion (carry-over)

[AydinZ71]

John made a good point about our meandering conversation on someone's wheel/tire post so I started a new one. 

 

@JMortensen, @Dat73z

 

Attached is the specific tire we run in EP (I say "we", as if I actually have the car on the road). Il post some pics of the wheel/tire combo on the car. Agree with Jon that the racing tires certainly feel a lot lighter than DOT street tires, although I have not weighed a 245 tire as a comparison. As I said in my previous post, the combo came-in at 33lbs w/ a wheel weight of 13.6lbs. I am still amazed how Koenig can achieve that knowing the top-of-the-line TE37V is just under 11lbs in the same size. The Koenig's were $109 ea on Summit and lighter than the conventional (and much more expensive) panasports. 

[JMortensen]

Wow. Those cantilevers are giving up some weight. Must be the sidewalls. I guess they're 19 or 20 lbs.

The FA rears are 13.75 x 24.5 x 15, only weigh 23 lbs, and they're 100mm wider and 1.5" larger diameter. The FA fronts are 9.4 tread width and 17 lbs. Wheels are a lot heavier though. The steel wheels I'm running are 24 lbs IIRC, so 47 for each corner. Could probably get that down 10 lbs if I spent a whole bunch of money on wheels. I kinda like the steelies though. Shows how low dollar the build is, like the stained plywood splitter... 

Edited August 7, 2022 by JMortensen

[AydinZ71]

Hey if you have the torque and braking to make the steelies work, why not! The extra inertia can more easily be over-come through those upgrades than getting expensive lightweight alloy wheels anyway. 
 

EP’s is pretty darn restrictive, but that’s what I liked about it. Super limited on what the motor can output (Greg’s landed at 260hp in his most competitive seasons if I recall correctly) and improved braking beyond pads and slots comes with weight penalties. In that scenario, all you have left at your disposal is cutting rotational inertia, weight, etc. As I mentioned in the previous post, building the car makes me feel like It’s becoming more Miata and less a “hot rod” 😂 You end up “trimming the fat” like a welterweight fighter, but when those restrictions are lifted, who doesn’t want to bulk-up like Mike Tyson! 
 

hey just a thought on that splitter. I have been playing around with my spare polycarbonate from the windshield. This stuff feels like “wonder” material. It’s stiff but doesn’t buckle, bends but snaps-back consistently, super hard to scratch with even course sandpaper. I think I’m going to give-it-a-shot for my own splitter. I’m only allowed to cover the leading edge of the air dam back to the front wheel well opening, so for a limited distance it should work OK. Il probably use thin 3mm stock, but reinforce it with an AL beam near the rear. it’s also rather easy to cut with the “right” Bosch jig saw blade. 

 

 

[tube80z]

Brakes will be the hardest thing to make work.  My friends used the S130 vented discs and front calipers to try and help with temp and get a bigger pad.  In the end those required a bendix pad that worked at very high temps and as much air as can be sent to the disk and caliper.  The rotors had to be cryo treated or they were throw away items after a weekend or two of races (buy good quality versions).  When cooling down after races or practice I would use blowers and turn the wheels if you can.  On the rears they used disks and a wilwood calipers and a lot of ducting.

 

You're going to have knockback and all you can do is minimize it.  If you can, float the rotors on hats.  I'd also use bearing spacers and make sure you check all the tolerances with the bearings (REM finish them) as those and the spindle flexing will be a big factor in knockback.  Make sure you brace the struts.  On the wheel side I'd test their stiffness to lateral force.  The stiffer the better for their weight.  The stiffer wheels will work with slightly less camber.  I'm sure I'm missing some of the tricks that were used. 

 

EP sucks when it comes to brakes on the S30s.  Good luck and have fun.

 

Cary

[clarkspeed]

Brakes are a challenge, but those cantilever slicks are the bomb. Roughly 9.5 tread width on a a 7" wide rim. There is nothing else like that. I may end up with them if I can't beat it. But surprising enough, a 245 Hoosier R7 generates very similar lateral g's but with more weight to carry.

 

Greg runs a fairly simple brake setup. He uses the vented disks up front and a Maxima setup in the rear if I am not mistaken. I don't think he does anything special to the rotors, just cheap off the shelf. He does use a VERY high quality pad which is also off the shelf.

I think you are only limited by rotor diameter in EP. I may go back and take a look at the rules to see if there are some better options like Cary mentioned.

Greg also runs very high quality wheels. Volk or Jongbloed Not sure how much that factors into his success.

 

[AydinZ71]

@tube80z @clarkspeed 

 

Thanks for the comments guys! I did confirm Greg ran the 280zx front brakes. I'm taking his lead since the way the GCR is written can be confusing. In one section it says anything used other than OEM carries a weight penalty, but then do they do list 280zx brakes on the spec line. 

 

I will look into the Bendix pads and ask Greg what he used. I might get-away with Porterfields and just go easy on the brakes until I start to feel they are my limitation (besides a lack of driving skill haha) Im not sure if we can split the OEM form-factor for the 280zx brakes into a separate rotor and hat, but I will look into it!

 

We have to keep the darn headlight buckets uncovered per rules, so I was going to use a velocity stack in place of the headlights with a 4" duct to the rear of the hub so the air can travel through the vented vanes. Should provide quite-a-bit of cooling. Plan on running the Koenig rewinds for the time-being until I can find a pair of Volk wheels in the now-discontinued size (15X7"). Hopefully they bring that size back. 

 

Thanks for the comment on knockback! I will look into that as well, including your suggestions. Thanks all!!

 

Any thoughts on brakes for an open class (vintage)? Front-runner for me was the AZ zcar setup, but wanted to hear your thoughts! I don't plan on running a wheel larger than 15". 

[clarkspeed]

How much do you want to spend? I'm not a fan of the big brake kits, they are way overkill. And depending on organization, the will get you bumped a class. Check the vintage rules, many also require a cast iron caliper.  In front I prefer the stock solid rotors with Toyota 12+8 caliper. You can adapt 2nd gen RX7 pads which opens up a cornucopia of choices at a fair price. Cheap pads, calipers, and rotors that work with proper cooling and fluid. The rear you have about the same options as EP including drums. On the rear of the car I just sold, I adapted stock front calipers to the rear using a SAAB solid rotor. They worked great, SUPER cheap, and within the "spirit" of the rules. Calipers are wide so you have to run wheel spacers to keep them out of the wheels.

I don't have any restrictions on the tube car other than they fit in the wheels. That is  why designed my own setup based on floating 11.75 x 0.810 vented rotors in front. 2 options for rear I have not finalized yet.

 

I have all the measurements and can adapt just about any race rotor/caliper combination if you have something else in mind. Floating rotor mounts, radial mount calipers, etc. 

 

I have an old Arizona kit I will probably sell once I prove out my newest design.

[AydinZ71]

@clarkspeed with a long-enough timeline I could spend $1-2k for the “vintage” setup running the 3.1L I’m building. Definitely will be bumping classes for that one, but that’s more of a “how fast can this thing go” setup. For the EP setup, I expect the pads will be the most expensive component but otherwise not expecting S130 calipers and rotors to break the bank. 
 

nice that you have an AZ setup! How did you like it? My biggest concern after braking surface area and cooling, is weight. I have run the 4X4 calipers with the Z31 rotors and was not a big fan. Added a ton of weight to the front, and made the already common understeer even worse. I may have just had some bugs that needed fixing of course. Had poor rear braking at the time which would obviously make understeer worse near braking. 
 

I will probably have to come back to this in a few months, but should be ready to purchase by Oct. I’m still reeling from the body/paint expenses. Who knew just stuff in cans (primer, sealer, base, clear, filler) could cost 2-3k alone! Makes a $8k paint job sound much more reasonable when only $5k is labor. 
 

granted, I did refinish the entire interior. Once every inch was repainted, it consumed a full gallon each of sealer, base, and clear. 

Edited August 17, 2022 by AydinZ71

[clarkspeed]

Just my opinion, and you can get many, but the 12.19 x 1.25 rotors (or bigger!) whick is what most big kits go with, are way overkill. My car did 135 to 145 max on track, weighed 2350 total, and I brake really hard. I could not understand why I had such a crappy pedal feel after trying a few different pads. We put temp paint on the rotors and found they never got hot enough for the race pads. Ended up going to a performance street pad which felt much better. The pads lasted forever. The rotors never show any wear but eventually heat crack after too many cycles. All this combined with their huge weight convinced me I had to downsize. Unless you really want your brakes to last over multiple weekends, it's not worth the weight penalty. After driving multiple "vintage" setups I mentioned before, I am convinced I don't want much more for my unlimited car. The weight savings is a noticiable performance improvement. Hell the circle track guys only run 11.75x1.25 rotors and they weigh 3000+.

 

Brakes are really about heat management and pedal feel. It's the sticky tires that stop you. With that said, the IT guys always ran to totally stock set up with drums. If everything is fresh and adjusted correctly, they will pull your eyeballs out, but they need lots of cooling, maintenance, and may only last 1 weekend. They will start boiling fluid when the pads reach 20% wear. PITA.

 

So it's your decision. You might consider running same as the EP car. You may get some quantity breaks, can swap stuff around, and will always have some spares.

 

If you want to go down a different path, I can make some recommendations. And fabbing your own setup is roughly similar in cost as the big kits. Or you could upgrade with Bremo or AP if you really want to go big time.

 

[AydinZ71]

Hey this is super helpful Clark!! Really I’m clueless on the topic so your personal experience is ideal! With this in mind, il run the 280ZX OEM front and rear calipers to meet the EP spec and assume for now that I will likely have enough pedal response and heat dissipation for the future 3.1L as well. 
 

local friend of mine is picking-up a 280zx parts car and is earmarking the calipers for me. 
 

how about rotors? Are the OEM front vented and rear solid rotors sufficient in your mind? Without knowing any better, I was going to get quality OEM units slotted. 
 

pads, I was going to take your suggestion and start with quality street performance pads (porterfield?) and go from there.

 

i have experienced the same lack-of-wear phenomenon on my street Z. Same pads for 10 years… not even %50. Tires… under normal semi-aggressive driving even performance tires would lose grip from age before loosing tread. I always attributed this from a lack of load(momentum). 

Edited August 18, 2022 by AydinZ71

[clarkspeed]

Oh your gonna need to throw everything you can at those EP brakes. Again, best to ask Greg what he runs. I know he struggled for years with pedal feel before he got it right. I would copy his pads and fluid if possible. And make sure you have very good cooling air up front, if pulling from buckets that sould be good, but make sure it exits efficiently. Again you are going to need a very good race pad for  "small" EP brakes. Street pads will cook immediately. With those big brake kits, you have alot more options to control the heat.

 

I never put any extra money in the stock based hardware, and I don't think Greg does either. Greg's car did 155 at Daytona and is usually 10mph faster max on every track than my vintage cars. But Greg is a relatively light on brakes. So cheap calipers and rotors on Rock Auto unless he does something I dont know about. Start by Putting the money in the consummables fluid and pads.

 

Weather you autox, track day, race, or endurance race, brakes are just one of those things you should upgrade to the level you need, no more or you are either wasting money ot taking a weight penalty (outside of cooling air, gotta max that first). I know many that run track days in a Z and have to bleed between sessions. As long as they don't go beyond 20 min, no problem. But that is right on the edge, but then again, brake fluid is cheap!  If they wanted to upgrade, I would evaluate their system and go just 1 step more. And 1st thing I would check is if cooling air can be improved.

Hope this helps, and if something is off, hope someone else will chime in.

 

[JMortensen]

On 8/17/2022 at 9:36 PM, clarkspeed said:

Just my opinion, and you can get many, but the 12.19 x 1.25 rotors (or bigger!) whick is what most big kits go with, are way overkill. My car did 135 to 145 max on track, weighed 2350 total, and I brake really hard. I could not understand why I had such a crappy pedal feel after trying a few different pads. We put temp paint on the rotors and found they never got hot enough for the race pads. Ended up going to a performance street pad which felt much better. The pads lasted forever.

 

Interesting. I have 12.19 x 81 rotors front and rear, Superlite calipers front, Dynalites rear. I've only autocrossed this car, and not as much as I would like what with covid and some health issues that are now behind me. Car probably has 150 autocross runs on it. The local autox venue is on a circle track, so at the end of the run you do the length of the front straight, probably putting my car at ~100ish mph. I'm running Hawk Black pads based on John Coffey's recommendation (they work, but MAN, they are DUSTY AF). Rotors are blue at the outer edges and pads are probably worn 1/3 of the way through. I have no venting, because autox.

Thinking you could adjust your venting to make the pads you want to use work. I can say with absolute certainty that having too much thermal capacity is a whole hell of a lot better than not enough. When I had the L6 and was doing track days on stock front rotors with stock calipers and Toyota calipers, I got to the point where I no longer got adrenaline rushes when the fluid boiled and the pedal went to the floor. I got used to it. That's not good. I also pushed the piston through the pad backing plate when the pad material gave up and exited, and had rear 280ZX pads overheated to the point where the pad was breaking up and coming off in chunks.

I agree that your average street Z with 12" brake kit is overkill, and I could probably get by on my car right now with stock brakes while autocrossing. The main point, as you said, is that the TIRES allow you to put heat into the brakes. It's not the V8 or the turbo that requires bigger brakes. The stickier the tires, the more brakes you need, and obviously the longer the courses or the sessions, the more brakes you need as well. I did all my braking carnage on the L6. I'm still a bit intimidated to take this thing to the big tracks in the area, as one of them is famous for eating cars (just dangerous) and the other had a friend's GTI on street tires doing 145 at the end of the front straight. I'd be going a lot faster. 170? More? That's high stakes stuff...



 

[clarkspeed]

So I am looking at the GCR production class. If I am reading this correctly, you can substitute brakes for a 2% or 43lb weight penalty. Measured with driver coming off track.

If substituted:

1. No more than 4 piston

2. Aluminum caliper

3. Unrestricted rotors as long as they fit inside wheels

4. 2pc hat allowed

5. Rear rotor no larger than front

6. Rear must be solid rotor.

 

Hmmmm. I know Greg would say it is not worth the penalty. But he only runs his car in pursuit of Runoffs trophy and intends to win every race. No regional races. And he can extract the last couple of 10th's out of a lap better than most of us.

 

Something to think about. Would cost alot more up front. Might be able to save a little overall weight. As stated before, probably not stop 1 inch shorter, but could add a ton of consistency. 

[clarkspeed]

Oh hell, I have not been on their website in a couple years. Check out DP Racing. They are the only company offering a "small" big brake kit that I know of. They have the right idea. But you can go even beyond this if desired.

[AydinZ71]

19 hours ago, clarkspeed said:

So I am looking at the GCR production class. If I am reading this correctly, you can substitute brakes for a 2% or 43lb weight penalty. Measured with driver coming off track.

If substituted:

1. No more than 4 piston

2. Aluminum caliper

3. Unrestricted rotors as long as they fit inside wheels

4. 2pc hat allowed

5. Rear rotor no larger than front

6. Rear must be solid rotor.

 

Hmmmm. I know Greg would say it is not worth the penalty. But he only runs his car in pursuit of Runoffs trophy and intends to win every race. No regional races. And he can extract the last couple of 10th's out of a lap better than most of us.

 

Something to think about. Would cost alot more up front. Might be able to save a little overall weight. As stated before, probably not stop 1 inch shorter, but could add a ton of consistency. 

 

 

Hey thanks Clark! yeah its the spec. line that has me nervous. Has the 280zx brakes listed specifically, for no weight penalty. As you eluded to though, I plan to run regionals. A part of my over-thinking is to ensure the car is truly built to EP, so I have some pride in it if/when I sell. I hate saying "it is EP, but... yada yada" Good point on Greg's ability to actually "use" the weight advantage. Me being a complete novice! I should be seeing him in Oct/Nov. so I can pick his brain on the specifics of his rear setup (which caliper, rotor, how he adapted etc.)

 

So here is my thought-process. Start with the 280ZX front brakes, leave the rears drums for now. Once the car is all put together, I can finally weight it and see where I am. If I am already above 2150 w/ me in it, then its a no brainer! I know Greg runs the willwood caliper in the rear so need to understand how he negotiated that. 

 

Really appreciate your involvement in the development of my car! You, Jon, John, Cary. All been very helpful.

 

Now if I can ever get out of bodywork purgatory! 

Edited August 21, 2022 by AydinZ71

[AydinZ71]

@JMortensen Gosh I'm really curious to see how those huge 4" ducts and v-stacks coming out of the headlight buckets are going to fair, even with the OEM S130 caliper and vented rotor diameter. I only know of Lance and Greg running them in EP, but im sure there are some folks in regional that have those running as well. Since we cant ditch the OEM headlight bezels or even cover them, its kind of a unique opportunity. Most S30 race cars I see either have the bezel replaced entirely with a fiberglass nose (like the CP cars), or have a plastic cover over them. Needless to say they are an aero drag for sure! It seems like a large enough variable that it could make the difference between a vented rotor front setup that "works", and one that fails measurably (like your disappointing description of losing your brakes on track). 

 

I'll just have to live with the performance from the 280zx calipers, but there seems to be enough flexibility in the rotor design (seems to only be limited by the diameter) to make some tweaks. Cryo treatment, angled vanes, slotted, alloys, etc. 

[JMortensen]

All I can say about ZX fronts is that the rotors are tiny. Under 10" diameter. They are vented though, and that's probably enough of an advantage to make it a good idea. Friend ran the full ZX brakes on his 510 and it worked great, even the rears that I had pad disintegration issues with. Lighter car though.

[clarkspeed]

Yes the alternate parts on same line are accepted with no penalty. I did not think he runs a wilwood caliper on EP car that I can remember. It looked like a Maxima setup.

 

EP allows alot of mods, dog ring box, brake upgrades, and EFI. But you have to pay it back in weight. Greg has optimized each of these with the stock parts. And even tested against the upgrades to verify his stock based parts are best. For example, he runs a stock 4 speed because he proved to himself that even the additional weight from a 5speed  was not worth it and engine torque curve beat out better ratios. Think about that for a minute. 

 

It's funny I can talk about Greg's car freely without giving away any secrets. I've been all over it throughly, and there are none. Just 20 years of development, attention to detail, solid chassis and a damn good driver. If there is a secret, it's his constant experimentation, he is always testing new ideas. 

 

So yes your thought process is good. You could even start with stock soild front rotors to get going. And drums with good shoes are fabulous. Just a little more difficult to keep adjusted. Again, put race tires on a car and it becomes a race car with corresponding G forces.

 

 

[tube80z]

On 8/20/2022 at 1:11 PM, clarkspeed said:

So I am looking at the GCR production class. If I am reading this correctly, you can substitute brakes for a 2% or 43lb weight penalty. Measured with driver coming off track.

If substituted:

1. No more than 4 piston

2. Aluminum caliper

3. Unrestricted rotors as long as they fit inside wheels

4. 2pc hat allowed

5. Rear rotor no larger than front

6. Rear must be solid rotor.

 

Unless you want to run at the pointy end of EP I'd personally take that penalty.  It also depends on how much your car weighs.  I've seen people pay stupid amounts of money for pointy end solutions on cars that never will make weight.  So unless you need to ballast to get to legal weight I'd use decent brakes that you aren't having to rebuild between days or race weekends.  The time you save can be put into better use like reviewing your race data, planning in the next change to try, etc.