Do they hurt your MPH? Just curious as to how much they would hurt, if they hurt at all. This would be for a stock Z. Thing is, my track can't hold BFG DR's, so E.T. streets would be my only choice. If i could cut a 1.7 sixty foot, i might be knockin on 12.0's door
The more rolling resistance you have compared to a stock tire, you will certainly lose _some_ MPH...but not much at all. These tires with real flexible sidewalls also "grow" a bit as you gain speed, so while they look all wrinkled on launch, they do not do this all the way down the track.
And some people don't understand that excessive wheelspin will acutally hurt your MPH as well. Granted, I'm talking about cars that are trapping 125+mph, but I have timeslips that prove this. Realize that if you were to burn-out on the starting line, and smoke the tires for 300', that you are actually shortening the track. In essence you have less distance in which to accelerate to a given speed, and thus trap speeds can _decrease_.
Bottom line is that you might lose 1 mph on a given night (if you run some passes on radials and then on slicks), but you will pick up significant ET for sure.
Just don't break anything!!
__________________ '02 Z06 (606rwhp/594rwtq)...LPE/21CMC Stage 2 Twin Turbo
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Originally posted by Hye06 ...Thing is, my track can't hold BFG DR's, so E.T. streets would be my only choice.
I suspect that 315 BFGs will hook in the 1.7s even on that track, if they get heated well by a long smoky burnout. That's one of the reasons that BFGs are the DR of choice by a wide margin.
MT ET Streets will hook better than the BFGs but only at increased risk of drive-train issues. Plus the small amount of grinding that's required, "marks" the car as running slicks; something most dealers will notice when considering drive-train warranty claims. None of this may matter if warranty coverage is not something you're worried about.
Originally posted by Hye06 Do they hurt your MPH? Just curious as to how much they would hurt, if they hurt at all. This would be for a stock Z. Thing is, my track can't hold BFG DR's, so E.T. streets would be my only choice. If i could cut a 1.7 sixty foot, i might be knockin on 12.0's door
thanks!
This is actually a fairly complex question. What is your goal when you take your car to the track?....ET or MPH? There is nothing that stickier tires do to hurt the performance of your car. The only thing they do at the track is allow you to hook better and get down the track quicker(better ET). Since the 1/4 mile goes by quicker, you may not have as high of MPH.....am I making since here? Many times you will see a particular car's ET improve as their MPH gets LOWER.....to a point where every thing is in balance(traction vs. power) There is a synergistic(whoa....did I say that) relationship between the 2 figures. On the other hand, think of spinning tires as "stored" energy.....maybe even potential energy. Once they hook, you either bog(which in a high torque car like these usually doesn't happen) or your car catches up to the speed of the wheel spin and they spin no longer. The spinning cost you lotsa time, but not much in the MPH department. That is why when you see someone pull a 12.5 at 125mph, you know the guy was having traction issues and that his car is capable of much better ETs. I have also seen someone pull a 12.5 at 106!!!! Not much left in that car......it was perfectly tuned and tires were perfectly hooking. Yes his MPH is low, but his ET is quite decent. Probably the only way he is going to improve on either figure is to get him some more power. Am I making sense??? When you see someone get excited about their MPH on a 1/4 mile run(regardless of their ET), it is just a GENERAL indicator of how the car is performing. When you factor in ET, then you can get a GENERAL indication of what the car is capable of and if it is performing up to its potential(relating to traction). I hope I understood your question. Sorry for the long winded answer.
Ranger:
what rim would I want to run a 315 BFG DR on? I hear the CCW still require a tad of grinding. Can u run them on the stock 17's in the front? Will that cause the tire to "bulge" on the rim?
Flynlo:
that made perfect sense! I understand everything you said. Thanks for that writeup, appreciate it. My goal is more concerened with E.T then MPH. I could care less about the MPH as long as the E.T. is there.
I suspect that 315 BFGs will hook in the 1.7s even on that track, if they get heated well by a long smoky burnout. That's one of the reasons that BFGs are the DR of choice by a wide margin.
Ranger
I will have to disagree with you on this. Carlsbad is BAD. It has worst track conditions. Guys running F-bodies H/C A4's with 4.10's pushing 450 rwhp running full slicks are lucky to get 1.6 60 ft's
Pat's best 60 ft with ET streets is 1.74. He has done the clean the tires VS the see smoke and count to 5 alligator's method
Originally posted by Hye06 ...what rim would I want to run a 315 BFG DR on? I hear the CCW still require a tad of grinding. Can u run them on the stock 17's in the front? Will that cause the tire to "bulge" on the rim?
If you have no alternative to Carlsbad, then look at the tires successful racers there are running. Momma says only ET Streets will get 1.7s. I have no reason to doubt that she is correct.
I do, however, suggest you consider whether or not the driveline issues that can flow from slicks are of concern to you.
With that said, the wheel choices for BFG 315.35.17 are:
Z06 fronts (9.5" width); what Powershifter say he runs.
GS rears (10.5" width)
ZR1 rears (11" width)
CCW (12" width)
None of these choices require any change to the car. All are a straight bolt up.
You may be thinking of the 16" CCW wheel for ET Streets/Drags. That one requires some grinding/shaving.
Another reason you will see purpose-built drag cars run what seems to be low MPH for the great ET they get is due to gearing and the engine actually being out of its powerband as they cross the finish line.
I see this all the time. I've seen guys run 11.9s @ only 110mph. The ET is a function of TQ multiplication (gearing). Let's say its a 3-speed trans (automatic with no overdrive). The normal shift point we'll assume is ~6500rpm. They set it up geared very low so that 3rd gear is engaged by the 1/8 mile mark. If you ask this guy what his finish line rpm is, he would probably tell you 7000-7200rpm...which is out of the motor's powerband...BUT, b/c he had such good TQ multiplication for the first 1000' of the race, his ET is phenomenal. The MPH is less than it might be if he had an additional gear in the trans to keep the engine in its more efficient powerband. In effect, he is not accelerating much at all past the 1000' mark, but merely holding on to the great ET he made the first 1000' of the track.
You can have too much wheelspin (probably not on a car that runs 115-120mph) that will actually reduce trap speeds. Been there, done that. Take an 1/8th mile trap speed comparison as an example and you'll see this play out. Usually over a 1/4 mile race, the MPH will even out pretty close, but in an 1/8mile race, the sticky-tires will show a much higher MPH than the radial tires.
I would say at least 1mph. The day I ran 11.65 I also tried my BFG 315/35/17 mounted on front Z rims. With the BFG's my mph was in the low 119's. I only made 4 attempts before I gave up and put the ET streets back on. 60ft dropped to the 1.8-1.9 range and ET fell to 11.8-11.9. I always take both sets of tires to the track in hope's that one day the prep will be so good that I can run my best on BFG's. One of my goals for next year is to run 11.5's on the BFG's.
__________________
02 Z06 CDN PERF 347 F1C, RPM 4L65E conversion
BEST ET 9.6
BEST MPH 146
My best MPH to date has been on the ET Streets. I went 116.55 on a stock car with the ET Streets bolted up. One of the issues with ET Streets is to run as much air pressure as the track will hold. I.E. if the track is sticky you might get away with 18-20PSI. On a bad day you may have to run 12-14psi. I normally run 14 and never have any problems. I could bump the pressure and pick up some mph. But, I never have traction problems with them.
Also, the clearancing is a minor thing. If I though it were and issue, I could dress it up a bit, and the dealer would never notice it, if they cared. Which in my case they don't...
I would say there is probably 1-2 mph based on input from other racers who have switched back and forth...
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