Drag Racing Tech - Spinning on Launch - Need Help!

Hey guys,

I'm trying to sort out some issues with my launches, but figured I'd ask for help here!

It's a '98 Z28, and has BMR LCAs, an Adjustable Torque Arm, Eibach Pro-Kit springs, 315/35 Nitto 555Rs. ~400rwhp/400tq with a built 4L60E. It only has a stock Converter in it for the moment; so I'm only launching at ~1800 RPMs.

The problem I'm having is my 60ft times are just terrible, making the entire run awful. I spin pretty much all the way through 1st, and then again when the car shifts to 2nd.

I've tried lowering the PSI in the rears, but as we got lower, the times got worse. First pass at 30psi, the 60ft time was 2.11s. At 20psi, it was at about 2.5s.

Any recommendations on where to start on correcting the issue? I shouldn't be overpowering everything with what I have, but that's what it feels like.

Thanks!

You don't want to keep lowering the pressure, becuase as you can see you slow down. I would go with a different tire. Like Mickey Thompson ET street. People say "you will blow your rear!" Get a girdle it will be fine.

I'm assuming you run a 17" rim? If so, the lack of sidewall is most likely your issue. Also if the car is lowered then you really need adjustable LCAs and relocation brackets to regain proper suspension geometry.

We mostly kept lowering it trying to get the full spectrum and see if there was an ideal setting, but we quickly found out that there wasn't. The ET Streets are a likely change I'll make at some point in the future. Yes, I'm running 17's. Would the tires make that big of a difference, even if something else is off?

And would putting the stock springs back on be an improvement over it being lowered? Had considered that, instead of spending more money if I don't need to as I'm trying to correct the issue on a budget.

Thanks!

400whp, sounds like you have a decent sized cam in there...I would get a stall asap. And I also agree, those tires are pretty terrible. I could barely peddle my car down the track with 305/40/18 nittos , but could launch off the 2 step on some MT' 275's

nittos are not the best tire for the track, on my nitto drs i have to fry them to stick ,imo my mts were such a better track tire , i just got sick of buying 2 tires every year

Roast those things to the moon. Nitto DR are about the worst, but some people get decent 60' out of them especially with an auto.

I run the 295/45/17 Mickey Thompson ET Street Radial II on my car and holy shit... all I can say is hang on because they WILL hook. Just be careful what you wish for. All that spinning is what is keeping your rear alive. I disagree with what the guy above said. Maybe he has never dead hooked with a sticky tire before. If you bolt these tires on with 400rwhp, you will break the rear end, girdle or not. Maybe not right away but eventually, especially with a stall.

I skipped the 315/35/17s and went straight to the 295/45/17s so I'm not 100% positive but I'm 99% sure that even the 315/35 in the Mickey Thompson will dead hook at your power level. Mighty Mouse ran those into the DEEP 9's before he went to the 295/45 for the higher sidewall height because he was dipping into the 8's. I think he ran something like a 8.7x at 160mph on those 295/45s. 8 second 1/4 mile, drove to the track and back, 'nuff said. I would get the 315/35 if I were you. The 295/45 will disable your ABS because of the tire height difference front to back. Front is 25.6", rear is 27.5" (they say 27.2 but I measured brand new at 27.5+).

Get the 315's in the MT's, a stall and a 9" and you will be rollin'.

btw, no they will not last longer than a single season but you have to make compromises somewhere. These are made for a specific purpose and they live up to the hype. Try them and I guarantee you will run nothing else. btw, it's been said that they are not safe in the rain. I've had no problems personally. I use common sense though like don't accelerate in corners, or take corners quickly, don't drive past 35-45mph, i.e. stay off the freeway when it's raining.

Good luck

I assumed the tires were definitely part of it, I just didn't think they'd be that bad!

I have a ~3000 stall on the way. Since it's my DD, I didn't want to go too high with it.

And yeah, the rear end is something I'm a bit worried about, which is why I'm a little hesitant to go straight to the MT's. I mostly just want to clean up things for the moment, so I'm not spinning as far as I am. I expect some spin, but through 2nd gear is rough.

Thanks for all the help, guys!

I'd get the MT still, just do less of a burnout if you don't want to dead hook. :cheers:

I have the stock 10 bolt running 255/50/R16 don't spin and I even launch about 1200. The only thing i have broken in the rear was a Richmond gear pinion. Oh and im running a Girdle.

I'd get the MT still, just do less of a burnout if you don't want to dead hook. :cheers:

Yeah, I'll have to get another set of wheels to put them on. I really can't drive around on them daily. If it does rain here, it's far too much for me to be able to get home on something I can't drive at a decent pace on. It's almost impossible to not take a freeway or a terrible back road. :)

Thanks again. :cheers:

get a set of cheap 15" drag rims(weld, centerline, etc) with some et streets. change shoes when you go to the track. problem solved.

I've cut some decent 60ft times on the same power level with stock suspension and a 3200 stall with a 275/40/17 Nitto. The tires aren't the problem unless they are dry rotted. Mine didn't start hooking good until I got under 20 psi. 15/16 seemed to be the sweet spot, and I'd run 20 on the street. Yes they are soft and squishy at that psi but that's what you want to absorb the impact of power. They wouldn't hook for shit at 25 psi, it was like a whole different tire.

get a set of cheap 15" drag rims(weld, centerline, etc) with some et streets. change shoes when you go to the track. problem solved.

x2 im with him

With the nittos you really have to give them a big burnout to get them sticky. Burn them out for abour 10 seconds. Ive netted 1.8 60fts with the 275/40/20r NT05 street tire version with a 4000 stall. I typically run them at 20 psi...no lower, and like said before you really gotta heat them up.

IMO your going to regret that 3000 stall you going to wish you went higher i had a 3600 in my last DD and wished i would have got something a lil higher but yet thats jus my opinion where two different people but with your tire pressure i suggest about 22psi ...also since the car is lowered you would want adjustable suspensions parts as well...

IMO your going to regret that 3000 stall you going to wish you went higher i had a 3600 in my last DD and wished i would have got something a lil higher but yet thats jus my opinion where two different people but with your tire pressure i suggest about 22psi ...also since the car is lowered you would want adjustable suspensions parts as well...

That's no lie, I have a 4k stall and wish it was bigger

IMO your going to regret that 3000 stall you going to wish you went higher i had a 3600 in my last DD and wished i would have got something a lil higher but yet thats jus my opinion where two different people but with your tire pressure i suggest about 22psi ...also since the car is lowered you would want adjustable suspensions parts as well...

Well, I got a really good deal on it and if I decide to go bigger, I can always see about having it restalled and it'll still be cheaper than buying a new one. :nod:

And I'm likely going to switch back to my stock rear springs, and go to a track that's prepped correctly... I found out about a week later how many issues other people were having at that track.

We'll see how she does once I get that converter in there, etc.

A nitto at 22psi and 17 psi act completely different. Don't run them under 20 all the time but for at the strip it WILL help.