Anyone run a C5 or C6 on 275/40/17s all around or similar?

[Cobra4B]

I'm in the process of planning out a new TTS/ST2 build with a C5 Z06. Our Panoz race car uses 275/40/17s all around so we have lots of tires in that size. I'm thinking of running 4 front OEM Z06 wheels which are 17x9.5, anyone else do that? This would allow me to get the +0.4 points and really lighten up the car vs. adding power. Also, it will allow us to use the same size tires.

 

I know runnign 4 18x10.5 rear Z06 wheels w/ 295s or 305s is popular, but wondering if anyone has gone this route? Are 275s enough tire to take advantage of a C5 or standard C6's handling? They seem to work very well for the Panoz. FWIW a guy on the Z06 boards got his car down under 2700lbs before the cage went in.

 

-Brian

[Aardwolf]

Was it Ken that won on that size? Pretty sure, but my memory is not always right. I run four of the thin spokes on my C4. They are 18x9.5" and I run 275 or whatever on all four. I have some V710 in 245 size that are the same width as a 275 street tire.

[jason]

Most all the TTA/PTA vettes in the SE are running 4 275 A6's.

[drivinhardz06]

Brian, a lot of us are running on the 275 bicycle tires now because of the rules. I played around with it last year just goofing off and testing stuff (that's what I was running at VIR when we were there in Oct), but with the '10 tire point changes, if you are running A6's or C91s, that's all you can use.

 

I have ran the 275's on OEM C5Z 9.5" rims and 10.5" rims. (10" is probably the perfect width/tradeoff for a 275 Hoosier.)

[Cobra4B]

Aardwolf - Make sure you check those thinspokes often, they're prone to stress cracking. I have them on my 2003 vert and did a bit of research on them. They're light and foged, but are known to get stress cracks where the spoke curves into the lip/barrel. GM redesigned a cast replacement thinspoke w/ fatter spokes and use them as replacements when the wheels had to be replaced under warranty. Some say the cracks are related to running runcraps and that normal street tires or race tires may be fine, but a good idea to keep a close eye on them.

 

Jason/Mark - What would you run if not for the rules? Do you feel that you're giving anything up? I mean Mark you ran a 2:06 out there w/ them on and that's flyin'. In my mind the other benefit would be minimal rotational mass. Those 17x9.5s are super light. Anyone running 4 17x9.5s run any wheel spacers? How's it fit in the rear?

 

As for size, on the Panoz we run them on a 17x9 BBS RK and they're 100% vertical so I'd figure a 9.5" wheel would be about perfect, no? I ran 275/35/18s up front on my old 18x9.5" CCW Classics (had 11s in the rear w/ 295s) and they weren't stuffed or stretched at all.

 

-Brian

[drivinhardz06]

Jason/Mark - What would you run if not for the rules?

 

Because I'm a cheapo, it's hard to beat the OEM 18x10.5" speedlines for the cost/weight/strength ratio. It's truly a case of light/cheap/strong, and you can actually pick all 3.

 

So because of that, if not for the tire rules, the 295 Hoosiers fit on a 10.5" just about as perfect as you can get, and I'd probably run them. At that point (IMHO), the car has enough tire, anything more is just dragging around more weight.

 

When I ran my 9.5", I didn't run a spacer in the rear.

 

Now that I got my car dialed in nicely, I'd like to try a set of 275's on 9.5" again just for kicks.

[Cobra4B]

So the two main routes are...

 

295 R6s on 18x10.5s and T1 bars with stock air intake and stock exhaust: 7 + 10 + 2 = 19

 

or

 

275 A6s (17s or 18s) and T1 bars with a CAI or delete the cats from the h-pipe: 7 + 13 - 4 + 2 + 1 = 19

 

I'm 235 so that means I can completely gut the car and still come in above the 3118 min comp weight. A CAI 2001 Z06 will make 345ish rwhp untuned Proabably 350s tuned.

 

If you can get the min comp weight to 3118 you can run 370 rwhp a it equates to 8.43 which is apparently allowed if you're running the 275s? I saw where the 275s give you -4 points, but where does it state that it lowers the power/weight .4 like it does with TTS/ST2?

 

So if you can be at 8.3 then the trick is to lighten the car as much as possible, because a tuned CAI low mileage '02-'04 Z is 360s rwhp max.

 

Am I on the right path? The car I'm looking at is a higher mileage 2001 Z so it'll probably be a 340ish rwhp car. My old 2001 made 342 rwhp untuned on a dynojet with a Vortex Rammer and Borlas, it made 384 w/ Kooks headers and a tune.

[drivinhardz06]

Brian, you got it.

 

If you want the 275's to work as good as possible, get the weight down.

 

you do get a .4 adjustment for the 275's, which you'll need if it's a healthy RWHP number and you want to run it at min weight

 

beyond that, I can divulge no more secrets

[Vettedoctor]

The 275's in TTS really depend on the track, I know that Ken was faster at Putnam with the 275 set-up but he never brought in out at Nationals at Miller. I think tighter tracks without long straits you are going to be faster on a wider tire, all you can do is test to find out what works best with your car. The best way to take advantage of the 275's would be to run a lower weight, but Ken was still fast by just upping his power (he still holds the TTS record at Putnam......for now )

 

So are you looking at TTS or are you going to join those guys and add another TTA car to the mix?

[drivinhardz06]

agreed it will vary from track to track a bit

 

IMHO:

 

- At the end of the day there is a sweet spot of unsprung weight (especially when you are stuck with the OEM shock damping), rotational weight, width, and shape of contact patch. more or less of a combo of any of that doesn't really buy you anything

 

- 275s on 10.5" C5Z speedlines is not far off the sweet spot

[Cobra4B]

I'll probably build the car to run TTA, then eventually cage it for PTA and just run up in TTS/ST2 depending on how many people show up for each class.

 

The more I think about it with the TTS/ST2 Corvette guys going to full aero you have to run 2.03s at VIR to be i the hunt... 2.07s and 2.08s don't cut it anymore. I like the idea of a sort of "spec" class for the car in that I don't have to spend more money becuase I'm not allowed to. I can foucs on getting the most out of the car within a pre-defined set of rules.

[yakisoba]

That's why I like TTA. You just can't spend that much. I would think balancing and blueprinting an engine would be the largest expense you'd incur, and you don't really have to.

 

I'm running 275/17 R6 on all four, using some old Kodiak race wheels. It is working out pretty well, though the car is still too heavy: 3301 was the last weight I recorded post-race. I managed a 1:25.3 at Hallett with that. I can't fit A6 in with the other mods I have on the car, and the R6 last longer. The more I run on the 275, the faster I'm getting. I don't notice the loss of width as much as I thought I would.

[Cobra4B]

Anyone run the 255/45/17 Ho-ho? That would make the A6 a 3 point tire and leave you with 9 to spend elsewhere.

[jimbow]

Anyone run the 255/45/17 Ho-ho? That would make the A6 a 3 point tire and leave you with 9 to spend elsewhere.

There was some discussion about this size on the corvette forum. Consensus was it was not enough tire for weight and G loads. Someone had tried it and tore them up in a day IIRC

[Cobra4B]

10-4.... was anyone else there or was this "person" trusting that we'd take his/her word on it What if 255/45s are the ticket? It'd be quite easy to spread misinformation that they don't work b/c people will naturally believe that.

 

I mean base C5s come w/ 245s/275s and Z06s come with 265s/295s.... A 255 Hoosier is probably fatter than the 275 goodyear that comes on the rear of the base car.

[drivinhardz06]

The more I think about it with the TTS/ST2 Corvette guys going to full aero you have to run 2.03s at VIR to be i the hunt... 2.07s and 2.08s don't cut it anymore.

 

I think I can get 2:03 at VIR in my TTA car, but it would be in true TT hand grenade trim (on fumes, stickers, cool air) so it would never hold up like that over a race w/ big fuel load on 275s, etc. 2:03 during a race is hauling the mail.

 

ST2/TTS can be a spending contest with the whole aero thing. The cost of a good splitter and rear wing would modify a C5Z06 from stock to decked out TTA/PTA trim and have $$ left for consumables.

 

Aero would be nice to have in the esses though, those Popp videos of him going up through there flat in an ST2 car are just sick

[Cobra4B]

Yeah even in the Panoz w/ the basic font air dam and fairly neutral rear wing it feels much more stable through there than I remember in my Z06. My foot is on the floor coming up through the last sweeping right hander. Also, coming out of rollercoaster I'm foot down and gain lots of time on people there on the entry into hogs pen.

[Cobra4B]

Aero would be nice to have in the esses though, those Popp videos of him going up through there flat in an ST2 car are just sick

He's ST1 as he currently sits... that car is one of the best sounding cars on track period. In ever knew the LSX could sound so good with a merged single side exit exhaust. I know turning 8000 rpms has a wee bit to do with it, but you can hear him all the way aruond the track when watching a race.

[drivinhardz06]

I think he posted a video of driving James Forbis' ST2 car, I just remember he never lifted in the esses

[jason]

I'll probably build the car to run TTA, then eventually cage it for PTA and just run up in TTS/ST2 depending on how many people show up for each class.

That's exactly what most of us are doing down here.

[Vettedoctor]

And Danny ran a 1.59 in Forbis's car as I remember, plus Danny said he left a little out there (Danny always says there's time out there as if the 1.59 wasn't sick enough!)

 

I like the challanges that TTA presents as to how and where you want to use your points, it makes running a FRC or Coupe look more appealing. However I'm a little confused as to how you could start in TTB* with a FRC without Z51(?). All FRC's came with Z51, is it just a place to start with a base class or do you have to prove it with your option list?

 

If you could start with a FRC in TTB* you would have 33 points to work with, I would say coil-overs, sways, intake, cam, headers, a brake kit and some 275 Hoosiers would work pretty well. Plus no problem getting to 3246, I would think you could get pretty close to 390 rwhp with an LS1 with intake, cam and headers.

So why are you looking for a 01Z?

 

Just stirring the pot.

[drivinhardz06]

yeah all FRC's were Z51 but I think they allow you to base class it if you were changing the springs/shocks/sway bars anyway (which is really only what made a Z51).

 

I think if you had a boat load of $$ to spend, you could build a faster TTA C5 using a coupe or FRC, but you'd have to use all the right combo of pieces and parts (lots of testing).

 

The C5Z right out of the box just "works". And you can run it lighter than a base C5's, a hundred and something lbs is a lot.

 

And I think if you talk to scott, the taller 5th gear and lower revs of the LS1 really hurts him, he has to use 5th much sooner, and that taller base C5 5th ratio, the motor really takes a nap on long straights.

[Vettedoctor]

I didn't really think about the tranny, but in the MW/GL region the only track you need 5th is Road America. I perfer the M6 box at most or our tracks the taller gears help you get out of the corners a little further. The M6 box would be better at Mid-Ohio IMO. Yeah 128 lbs is a lot but if you can put it where you want it will balance the car out very well. Just getting a C5Z to 3118 is tough so the balance may not be as good. Plus I think for PTA the extra points will make for a better car for longer stints.

[Cobra4B]

As Mark said you have to spend more money on a FRC/Coupe to get it to work.... I don't care to have LT headers on any Corvette again, they make everything hot and exacerbate clutch pedal issues. Nor do I want a cam that needs more valvetrain maintenance... KISS.

 

Speaking w/ Sperkins the FRC is TTB* but if you leave the stock Z51 stuff on you're taking the mod points for shocks/bars/springs. So to be TTB* w/ only 7 points assessed you'd have to put base bits back on the car.

 

I'm going south this weekend to pickup a 2001 Z (7 pts) if it checks out as it is supposed to be.... going to try a K&N w/ a '02-'04 airbox lid (0pts), cat delete (1pt), then run '04 sachs shocks (opts) and T1 bars (2 pts) and 275 A6s (9pts) all around... should be a fun and fairly cost effective track toy.

 

Going to 100% gut the car other than leaving the glass in it because I have an open trailer... wonder what it'll weigh in at w/o a cage and just a harnessbar.

 

PS I never use 5th at VIR.... it's a 3rd/4th gear course if you're really using all of the 6500 rpms and taking Oak Tree at speed on sticky tires.

[drivinhardz06]

Going to 100% gut the car other than leaving the glass in it because I have an open trailer... wonder what it'll weigh in at w/o a cage and just a harnessbar

 

plan on putting ballast back in (which isn't a bad thing).

 

I'm going to have to put the carpets back in when my lightweight clutch goes in next month, and I've still got a 25 lb trailer hitch on it.

 

these cars are pretty light