FRC Rob

We had some discussion about suspension settings in C5 Tech. However, threads in those other sections of the Corvette Forum tend to gravitate more toward handling aspect rather than drag racing. And, the concepts and/or practices regarding suspension settings will likely cross Corvette generations. So, I'd welcome feedback from all Corvette owners, as well as theories and/or practices that may apply from other vehicles with similar suspension layouts. The more pieces of the puzzle we can gather, the more it can help all of us.

Here's a summary of what we've determined (mostly by trail & error) and the questions raised so far:

Ride Height
Several owners who have significantly lowered their cars report that their 60' times have gotten worse. Is the suspension height adjustment changing the contact patch of the tires? What settings might optimize the contact patch? Could the lowering be affecting weight transfer? Are lowered cars "bottoming out" and causing the suspension to unload?

Shocks/Springs/Swaybars
I have removed my front swaybar because it seemed like a good practice, but I'm not sure that it really helped that much. I have also installed 90/10 front shocks. My experience is that they are not really helping the car accept a harder initial hit off the line, but they did seem to help keep the suspension from unloading as I pass the tree, which has improved consistency. What have you found that does (or doesn't) work for you.

Tires & Wheels
Mickey Thompson recommends their bias ply tires for manual transmission cars, and drag radials for automatics. We have reports from automatic owners of better 60', quicker ETs and higher mph traps on the radials. What are your stick and auto tranny experiences? What tires work best (and at what pressures)? Do skinnies up front help (aside from the top end handling issues with bias plys)? Some have been trending toward light weight rolling stock and brakes...what's the consensus?

Weight Reduction/Relocation
My FRC weighs ~3200# with me aboard. My biggest reduction was changing out the factory exhaust for headers/off road x-pipe/Ti mufflers. I also removed the air pump and related hardware, front swaybar and a few bits and pieces along the way. (It probably wouldn't hurt if I dropped another 20 pounds myself, but that's a whole different discussion.) What weight reduction measures have you taken? Ironically, I don't run any worse with full fuel tanks vs nearly empty...it actually seems to like a little extra weight in the back. So, what about relocating batteries to the trunk, etc?

Driving Techniques
We've all probably read Ranger's posts and he's helped many people improve their dragstrip performance. What launch techniques work for you? What about down track? Example: data logging has shown us that manual transmission shift points and speed of shifts has a big impact on trap speeds.

It seems that I've got more questions than answers, And, I don't mean to limit discussion to only these items (so feel free to expand the topic), but hopefully this can get us started. Any feedback would be greatly appreciated.

Thanks,
Rob

REDGAR

You say you limited the topic Rob but I think it is too broad. Its length will likely scare people away from replying as it is too much.

I, on the other hand will share as much as I can in one sitting.

opps, have to stop will post later

Allthrottleandsomebottle

Only thing I left off in my other post...............MY CAR IS LOWERED as well

REDGAR

You say you limited the topic Rob but I think it is too broad. Its length will likely scare people away from replying as it is too much.

I, on the other hand will share as much as I can in one sitting.

First the anwswers will be based around how dedicated you will make the car for drag racing. My car spends much of its life now waiting for me to drag race it so there are some steps I have taken that I would not recommend for the averag occasional racer.

So I will try a few things
I have run the rear lowered, normal and raised and find bottoming out a problem so I run a more normal stock height now. I have seen more say that lowering gets them better 60's than the opposite though.

Front sway bar removal help me with getting the 60's more consistent so that is the value in that for me.

Springs I have often wondered if a stiffer spring in the rear will help with 60's and it an experiment I will try at some point.

Shocks, 12 way single or double adjustable help tune to the track and a high cost. I think coil overs help the higher launching sticks with wheel hop avoidance

Skinnies are a nice deal. Lighter and less rolling resistance help. The bias ply issue is when you use radial front and bias ply rear…if you are drag racing a lot, invest in full bias ply set.

Weight reduction can be taken to extremes. You have to decide what you can live without. Here is a weight measurement list for some ideas http://forums.corvetteforum.com/showthread.php?t=984927 and here is another http://ls1tech.com/forums/showthread.php?t=17319

chiefDave

been here done this too...

10/90s up front, no sway bar and yes, it does help the transfer IMO. My car does yank the front off the ground now and it did gain .05 short, and is now doing mid 1.4s. IMO thta is good for a HC M12 on 390s.

Wheels and tires, wow! I loved the DRs from MT, and they where .2 better short for me day one. When I went to 390s, I could not get them to hook at all. The bias ply cheater slicks take more RPM to keep from bogging and for the most part take the hit from the rear end. If you dead hook with slick, cold rear end and first pass on a new clutch, bad things can still happen A billet side cover is going on my car right now and I hope that keeps it together. BLUFF I am more concerned about the hook and the short then the loss of tonage. My Z goes 3040 slicks, skinnes, 1/4 tank minus the loose nut behind the wheel

Fuel, again I used to run 1/4 but got starved once and the car shut off on the 1-2 shift I thought I broke it... but seems like I lost fuel and it started back up and I went off @ the 1/8th. My car seems to short better with 2/3 then 1/4 and I do not go low like that anymore either. Good point though IMO.


Sway bar, um yanked mine and it does help the short IMO and it realy helps the car lift the front and transfer out back. Yes, it does save yuo maybe 15 lbs? It will make it feal very loose on the hit, and it will take getting used to.

I have got lighter rotors to put on too, and I hope this will save some unsprung tonage as well. That and thye look cool Bad part is we are limited to OEM size to fit under CCW drag pack...

My car is lowered a bit out back and a little up front. Seems like it likes the travle out back so it does not bottom. I have seen a stiffer spring make a huge change in an A4.... like spin, or bounce and spin delt to hook, 1.40 short!

My biggest challange now is to eliminate wheel hop, as I am not good enough to peddle when or if it happens, and with the sway bar off the front...

time for lunch!!!
Dave

FRC Rob

chiefDave,
It looks like we have fairly similar combinations; I'm heads/cam/bolt-ons, Textralia OZ700 Z-grip, DTE Stage 4 3.90:1 with brace, RPM Level 5 MN6. (I run at 1/4 mile and 1/8 mile tracks, and the MN6 allows me to drive it through the 1/8 mile trap without shifting to 4th.) I've been running MT drag radials. Short times have been in the high 1.6's, but more commonly in the 1.7's. It runs 7.4's - 7.5's in the 1/8 (trapping in the 94 - 95mph range) and 11.6's - 11.7's in the quarter (trapping in the 120 - 122mph range) depending on weather, track conditions, etc. The car does not hook as consistently as I'd like, and is sensitive to track conditions, despite having no front sway bar & 90/10 shocks. I am considering stepping up to bias ply ET Streets and skinnies in hopes of improving consistency, and running a little faster. What improvements did you get when you went from drag radials to bias plys?

chiefDave

Very similar cars brother Funny stuff too.. my car on 342s, brace, shafts H/C did 11.4s @ 122-123, on a high 1.5 60 on ET street radials. I only had one or 2 trips to the track and then we put 390s on it.

The Drs are great tires IMO for around 400 RWHP, but you need a good heat in them (burn em up) and as low as 15 PSI hot if my memory is corect.

When we went to a 390, no hook or hop, game set match. Went to slicks n skinnies (MT ET street bias ply) and my MPH dropped a bit, but my short times dropped .1 to .2. The tranny was OEM and I was not getting it done on the big end, so my ETs where stuck around 11.4s

BLUFF the bias ply and skinnies are a great mod, and it is as big as or maybe more of a change going from DRs to slicks as skinnies. More to follow and great thread!
Dave

Joe_G

Rob,

I relatively recently went from ET Streets to M/T DR's. I was consistently 1.8's with the ET's and am now 1.6-1.7's with the DR's. The shorter DR's gave me both an et and MPH advantage with my 385 rwhp car. Steve did the same and had similar results. Same with Robert.

I found the ET's to be more consistent for sure - the DR's sometimes spin on me. But the DR's are quicker and faster with my setup. I can believe Dave that cars with much more HP than mine would need the streets, but the taller size killed them for me.

Mike (whom you never met) is, as I type, taking out his diff and will start joining us again in June. He has the Streets (my old ones actually) and you can borrow them before you buy them to see if you like them.

Remember that if you go to them you'll have to either get a trailer like I have or cram them in your car like Steve did. They fit in Z but not with a passenger. That's the real reason I changed, It's just easier to swap tires at home than at the track.

FRC Rob

Joe,
I'm not really sure what would be best for me at this point, but it seems that I need to change something, because its just too inconsistent the way it is now (especially for bracket racing in the Challenge events). I'm seeing very good drag radial results from most automatic cars, and it seems like some stick shift cars do well on them too, while other stick cars do better on bias plys. Why do some cars react favorably to bias plys while others do not? I'm not sure that there's an arbitrary horsepower threshold...heck, I don't even know how many ponies I've got. Realistically, probably only somewhere in the 400 - 420 range...but then again, my car has recently run competitively with a 440 rwhp car and a 510 rwhp car. That's a pretty wide range, so I've got little faith in dyno results. Perhaps you could draw some conclusion if two cars were to dyno back to back...same day, same conditions, same dyno...otherwise, its no different than trying to compare track results from Englishtown vs Bandimere. You can throw all the correction factors in the world at 'em, but there's really no way of accurately comparing the results. If changing 4 tires at the track vs 2 tires at home will fix the problem, then I need to suck it up and git 'er done. I'd be very interested in taking you up on that try before you buy offer...of course, I'd be willing to pay "rent" to compensate for whatever wear I'd put on them. Do you also have access to some skinnies to go with the rears?

Joe_G

You don't have to pay rent! That's what buddies are for. Steve has my old Streets, but I think he gave them to Mike whose Streets are bald. Chat with Steve on Saturday. In fact I'll PM you his number so you can call him and maybe hook up with him before you guys head up Saturday. I'll miss the event due to work unfortunately.

None of us have the skinnys. So the rear wobbles some at the big end. A little scary the first time but we all got used to it, however, that's another reason I went with DR's. I didn't want to trailer up 4 tires and buy 2 more wheels & tires, and frankly, I got to worrying about what would happen if I got out of shape at the big end with those wobbly tires. My handling was not the razor sharp Vette handling to be sure and I'm just in this for fun. And I personally never got below 1.8 with Streets and I usually run 1.7 and some 1.6's with DR's.

Just my personal opinion, but if you're not racing for money don't fool around with the trailer and 4 tires with your power level. You can learn to launch consistently on the DR's. Like most things, driver mod usually pays the biggest benefit (and it's free). The biggest gain is learning to set a very consistent .0xx light. You do that every time and you'll be hard to beat, whether you get a 1.5, 1.6, or 1.8, so long as it's the same every time. We only get a couple of months a year where we might set records - and from my obserervations the shorter 26" DR's will give you quicker and higher traps due to the gearing advantage.

robz

It seems like everyone's given you some sound advice. I've tried almost every tire and many different brands. In my experience the best hooking tire for an m6/m12 vette in the hp range of 400rwhp-500rwhp has been the mt et street 26x11.5x16. Keep in mind the m12 will launch better. The mt et street radial has proven to hook well and be very consistent but moreso for auto's. For consistency(brackets/indexes) you need to be scientific. Know your exact tire pressure,rpm launch,track temp, every single run and with alot of seat time you will develop a consistent clutch release and throttle stab. Practice and attention to detail will give you consistency moreso then the tire.
For best et go with the mt et streets.

Joe_G

Robz, did you have to grind your upper control arm to get the 16" on there? My buddy has a brand new set on Camaro rims but they hit, and we've been hesitant to start grinding on the control arm.

I makes good sense to me that if you could get that to safely fit, that short tire combined with the thin sidewalls would be the best combination of all if you decided to go with skinnys up front. I just never wanted to invest the $$ at this point for my basically stock car but maybe FRC Rob would be willing!

16Again

Just had the new set of 16" MT ET Streets mounted up at Horse Power Sales.
Ready for some play time now.

16Again

Joe are you sure it's the control arm and not the balljoint dust cap? 16's fit just fine if you dimple the dust cover. 30 seconds of work for miles of smiles.

FRC Rob

chiefDave,
Thanks for your input. I'm inclined to believe that due to the similarities of our set-up, what worked for you should also work for me.

Joe,
Got your PM and greatly appreciate the gesture. We will be out of town this weekend, so I'll miss Saturday's Challenge. I'll try to hook up with Steve after I return. Maybe I could just make a few 60' shots at Countyline...that would be a great proving ground, and would skirt around any potential top-end handling issues without skinnies. (Not to mention that I'm quite familiar with that track since I've made close to 100 passes down there in the past month).

Robz,
Thanks for your input, too. I follow your posts and you certainly seem to have your car dialed in.

Bob,
I'm so jealous. I called CCW a few days ago to inquire about their drag set-up. Unfortunately, they've got an 8 week lead time right now.

16Again

I waited for 2 years (due to lack of money) for John and Chip to "HOOK" me up. These things aint cheap, but they are money well spent. Roger (actually Tim) replaced the original ET's this morning since I cut one down last week when we were playing at Countyline.

By the way, if you want to try slicks and skinnies at the track, you are more than welcome to borrow mine. Of course if you scratch one, i'm coming for your first born male.

You can swing by here with a truck, and I will put my car on jackstands, or put street tires on her so you can run the CCW set up. The only problem will be what Joe mentioned above. You will need to trailer the tires up or the car up. There is no driving these on the street.

FRC Rob

Thanks for the offer Bob (and Joe); I'll be taking one of you guys up on that after I get back in town. I love the look of those CCWs, and they truly are bolt-ons (plus 2 whacks from a hammer). I was leaning toward some less expensive alternatives, but they'd require brake mods or using wheels designed for temporary spares. Although the CCWs are more costly, they don't require such "compromises" and they hold their value pretty well on resale if you ever decide to get rid of them.

robz

Yes. Some modification is needed in that area.

123sugey

Robz... Avatar is old lol. Just reading these older threads. Learning. You mentioned above "450-500 hp" what 16" bias ply size for my setup would you recommend ? Throwing my new drag radials in the trash lol.

383vett

Good info here but this thread is over 5 years old. Me thinks there is a rule against bringing back crusty threads.