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What is the lightest S30?


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We had a guy here 20 years ago, gramercyjam was his user name I think. I believe his L24 autox car was 1800 or 1850. Cary, aka Tube80z, might have been even lighter in his autox car. 1750 or so. Those two always stuck out as the lightest. I don't think either of them swiss cheesed their cars to get that weight. Just stripped out race cars with nothing that wasn't needed.

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Greg Ira set the new EP standard (literally, rules were changed based on his petition) to 2150 w/driver. That’s probably 1950 without him (helmet, gear), plus we have to run a fire bottle, 1.25” wall roll cage, chassis reinforcement, oil accumulator… I’m shooting for about 50lbs heavier than Greg, but we’ll see! 

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On 4/10/2022 at 7:21 PM, JMortensen said:

 Cary, aka Tube80z, might have been even lighter in his autox car. 1750 or so. Those two always stuck out as the lightest. I don't think either of them swiss cheesed their cars to get that weight. Just stripped out race cars with nothing that wasn't needed.

 

For hillclimbs my car weighed 1850 with 5 gallons of fuel in 10 gallon cell.  Car had a basic fire system and extensive cage (12+ points).  The shell was an early 240 with nothing in it that wasn't required by the rules.  It came from Montana and had been stolen and set on fire.  Custom fiberglass doors and stock hinges (heavy), one piece FG front end (JC Whitney), and the rear hatch was a FG skin bonded into the car (total pain in the butt).  All glass (windshield and hatch) were eighth inch Lexan.  Engine was  an old EP motor with the weirdest cam I have ever seen.  Engine was equipped with dual modified SU carbs, a Stahl style header, and a short exhaust that ended just behind the driver (yes it sucked).  Engine was a 2.8 all balanced with a 6 pound flywheel and stock type clutch and connected to 4-speed running a stock style driveshaft.  This hooked up to a R200 LSD using stock style half-shafts.   The car had a run-flat electrical system after my alternator sheared off at a hillclimb.  I ended up using the battery from my trailer's winch and that was a very heavy (~60 pounds) marine deep-cycle optima. It was setup so I could quickly remove it and stick it back on the winch.

 

A lot of people have told me that it is impossible to be that light.  Where the magic was (not much) in this car was the wheels, tires, and brakes.  Tires were from a Formula Atlantic and Kevlar belted, and had 13x10 wheels up front and 13x12 in the back.  The brakes were 10.325 vented front rotors with Wildwood 4-piston dynalites in the front and 10.25 rear rotor with 2-piston dynalite calipers.  Just changing to GY tires would add almost 40 pounds to the weight (steel belts versus Kevlar).  But they GY tires were faster by almost a second on a 46-second lap of the local track.  Few people pay close attention to what tire/wheel/brake weight adds to a car and it can really add up.  I never set out to try and build a super-light car and figured it was in the 2 to 2.2K that most of these cars were.   So I was rather shocked when we weighed it a buddies who had scales.  

 

Getting this car into the 1700s would have been possible with normal parts that are available now.  But it would have been expensive to go much beyond that.  My easiest area of weight loss would have 7.25 dual disc rally clutch and a lithium battery.  Those two items alone would have allowed me to save about 50 pounds of weight.  The other easy thing to do would have been to remount the cell so the sump was at the back and could run a gallon or two of gas instead of needing to be almost full.  From there it gets really expensive really quickly to shed weight.  Carbon parts, lighter versions of everything, etc.

 

I'm sorry but that Porsche in the video seems scary, especially looking at the seats.  

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@tube80z Wow Cary! A few questions, if you don't ,mind!

 

1) Did you have a cage? If so, what spec. or wall thickness? The SCCA EP spec bar is crazy heavy... 

2) have you ever tried the 5.5" flywheel-less clutches (the "flywheel" is like 6" wide, but comes with the clutch). 

3) tell us more about those wheels! Were they custom? The lightest I have found to meet EP spec (15X7, 4X114) is the TE37V Rays/Volk wheels. Curious is that is still the case. 

4) how expensive were those kevlar tires? 

 

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I can answer some of these. I'm running a dual 7.25" button clutch on my V8. There are smaller 5.5" ones also and you can get 1, 2, 3, and 4 disk units (maybe more) to hold more power. They use a flex plate to engage the starter in the standard location. For the super hardcore racers they'll have a smaller starter that goes in backwards on the transmission side and hits a smaller diameter flex plate. You can get button clutches for the L6, don't think I've seen the tiny bellhousing and flex plate for them though. Regardless, a flexplate and button clutch reduces the weight a lot because the pressure plate is smaller, the clutch disks are smaller and lighter, etc. 

I believe Cary was running steel wheels, but when you get them down that small they just don't weigh that much. The Formula Atlantic tires are not that expensive for slicks. I understood that my Yokohama 15" FA slicks I used in the 90s and 00s had a kevlar strip down the center and was told that this prevented them from expanding and changing the effective gear ratio at high speeds. FAs can get going pretty fast on super speedways, and used to run before CART cars at their events back in the day. Wasn't aware they had kevlar belts too.

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Thanks @JMortensen again! 
 

i should have mentioned, I bought a 5.5” button clutch/flywheel for the L24 a year ago working through Greg. Works with the auto trans flex plate just like you said. Just runs a single friction plate but an L24 doesn’t put out that much torque, even in EP form. I was new to these “button” units so always curious what the pro/cons are to various sizes/configs. Naturally, I have WAY overshot my expectations on a “finish” date, so still prepping the interior for paint while this $1200 clutch just sits on my shelf. 

 

the TE37V’s are 5.5kg each, which is just about the lightest wheel I can find in 15X7, but I think the loss of cornering response from a 13” wheel might not make up for the weight savings. Still, I’m so novice on all this that I’m obsorbing the various options like a sponge as I’m sure they will come in handy at some point! 
 

you have highlighted for me that I need to learn more about racing tires in my size. Il hit Google and see what’s out there, compare weights etc.

 

thanks again Jon! 
 

 

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On 4/13/2022 at 9:07 AM, AydinZ71 said:

@tube80z Wow Cary! A few questions, if you don't ,mind!

 

1) Did you have a cage? If so, what spec. or wall thickness? The SCCA EP spec bar is crazy heavy... 

 

The cage was 1.5 x 0.125 for the main safety sections spelled out in the GCR.  The extra bits were a mix of 0.095 and 0.065 that provided added bracing.  I added 1" x 0.49 bracing in multiple areas to stop bending I found when doing some torsional and bending tests on the unibody.  I personally think the car was so light as the shell was an early S30 and seemed to have thinner sheet metal in some areas compared to the later cars.  The cage tied into all the normal suspension points and had a center section similar to Jon's V8 car where a tube ran down the middle connecting the front A-pillar cross bar with the rear diagonal.  The strut towers had bracing that formed a Y structure front and rear that were connected into this.  There were some other odd braces that looked Nascar inspired that I had thought about removing to add a passenger seat.  This cage was scary and I was shocked that it ever passed tech at the hillclimb events.  I found that the underside welds of most of the cage tubes were just bondo sanded over to look a weld.  My guess is the PO couldn't weld upside down.  I removed all this crap and completely welded around the tubes.  In many areas I also added additional connections to the unibody.  These all added weight but probably less than 5 pounds in total.

 

On 4/13/2022 at 9:07 AM, AydinZ71 said:

2) have you ever tried the 5.5" flywheel-less clutches (the "flywheel" is like 6" wide, but comes with the clutch). 

 

Not on this car.  That was an area of potential improvement.  My V8 car has a setup somewhat like Jon's but I'm running a dry sump on the LS and mushroom flywheel.  The ring gear mounts to the back of my clutch.  This is a 7.25 unit and all this weighs around 13 pounds complete.   I have a low ground clearance bellhousing so I can drop all this down (~3 inches lower) to the point where the transmission case is the low point.  A fried has run the 5.5 clutch on an EP car and moved to a 4.75 unit.  The downside of all that is you have to run the stock size ring gear.  It is pretty cool hearing the motor rev like a superbike.

 

On 4/13/2022 at 9:07 AM, AydinZ71 said:

3) tell us more about those wheels! Were they custom? The lightest I have found to meet EP spec (15X7, 4X114) is the TE37V Rays/Volk wheels. Curious is that is still the case. 

 

The wheels were Diamond and Aero mini-stock wheels.  They are a lighter weight steel wheel.  They aren't very strong and are designed to fold up if hit too hard.  They are one step above junk really.  I only went this route as I was unsure about what diameter I would want to run.  Most of the GT tires were 16s.  At the time there was a glut of the 13 FA tires on the used market so I went this route being cheap.  There was more laptime to find with a better wheel/tire combo.  The Hoosier's at the time use a really light Kevlar belt construction.  The sidewalls were very flimsy and made using a manual changer a breeze.  The GY FA tires were more of a true radial and had steel belts and substantial sidewalls.  They weighed more and were definitely faster. 

 

They ended development on these and for a long time they were not available.  Avon seems to be the only valid player for the bias ply slicks.  I think Hoosier still makes a semi-redial tire but I doubt it's using their latest tire technology.  That seems to mostly happen in 17s and 18s.  I'd never run 13s on a track.  While they are light you're not going to see huge gains from this.  The larger tires have a smaller tread to road approach angle and this seems key to having better grip.  Assuming everything else is the same.  I think for EP you're going to be limited to the cantilevered slicks unless they rules have been relaxed. 

 

On 4/13/2022 at 9:07 AM, AydinZ71 said:

4) how expensive were those kevlar tires? 

 

At the time a new set were about $1200 new.  I bought used for $50 to $80 a tire depending on how good they were.

 

On 4/13/2022 at 9:07 AM, AydinZ71 said:

 

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@tube80z thank you Cary! All very helpful! Amazing you were able to get the weight so low with the 1.5”X 0.125 bars! EP is same spec. 
 

I have a set of diamond racing 15X7” wheels too, and weigh-in at 16lbs ea. the TE37V’s will cut 5lbs in each corner, but having trouble sourcing the 7” wide version to be honest. I’m super anxious about working through a “fake” vendor so trying to find a reference from someone I trust.

 

you have definitely given me some homework, and broadened my knowledge. Thanks to you and Jon! 

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On 4/14/2022 at 10:51 AM, AydinZ71 said:

@tube80z thank you Cary! All very helpful! Amazing you were able to get the weight so low with the 1.5”X 0.125 bars! EP is same spec. 
 

I have a set of diamond racing 15X7” wheels too, and weigh-in at 16lbs ea. the TE37V’s will cut 5lbs in each corner, but having trouble sourcing the 7” wide version to be honest. I’m super anxious about working through a “fake” vendor so trying to find a reference from someone I trust.

 

 

I bought Volk TE37 V "17 through ACG automotive in San Diego with good results, but they took forever to ship and that was before the covid BS....

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hey, thanks @Nelsonian

 

Yeah it seems every vendor is having a hard time getting them to customers in a reasonable amount of time. I have heard that from multiple sources now, and as you would imagine its worse after COVID.

 

So I am in a bit of a jam. Factory is not making the 15X7" i need to meet SCCA EP spec, only 15X7.5 (kind of odd). 

They did make a 10th anniversary addition in 15X7" last year but I am struggling to find anyone who still has a pair, and the factory stopped making those too. 

 

I might just have to give-up on Volk 😕 They were the strongest, lightest (11 lbs) wheels that could at one point be bought in that size.

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Thanks man :) 

yeah… been looking on eBay, but that’s a good tip and I will continue to do so. Hard to find the wheel that checks all the marks, especially the 4X114mm. Also, as with most things in the automotive world, the used market is flooded with “slammed” street wheels 8”+, and a 0 offset is necessary with my suspension geometry. 

 

Truthfully, would I pay $2500+ for a lightweight racing wheel on a street car? Hellllll no, but clearly there are many that have the disposable income! 😂 
Just kind of sounds like putting high performance running shoes on hipster with a bacon belly, but who am I to judge. 

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  • 3 weeks later...
On 5/6/2022 at 7:20 PM, JMortensen said:

Lightened 432R with dual exhaust (adding weight back?) complete with S20 and crap Nismo roll bar: https://www.facebook.com/photo/?fbid=10159065665906559&set=pcb.1922406734626606

 

Complete with dumb comments from people who don't know what they are looking at, eh Jon?

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On 5/6/2022 at 7:20 PM, JMortensen said:

Lightened 432R with dual exhaust (adding weight back?) complete with S20 and crap Nismo roll bar: https://www.facebook.com/photo/?fbid=10159065665906559&set=pcb.1922406734626606

 

But seriously, I'm interested to hear your informed opinion on the full specification and details of the car, "...crap Nismo roll bar" and all.

 

How old are you, Jon? Here's a photo of the car in question, racing in 1971. I'm guessing that you might not even have been born in 1971? Oh, and NISMO wasn't 'born' until 1984.

 

 

Ish-102.jpg

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