I thought I would start a new thread on this. (Last one I promise...)

Changed tires from 235/55-18 to 235/50-18, new tires are .93" lower than factory original

0 to 60 went from 5.7 to 5.4
recorded times 5.38, 5.33, 5.40, 5.41
1/4 mile went from 14.22@98 to 13.82@105mph
recorded time were 13.85@104, 13.83@104
Intermediate times can be posted.

The only mod on the 2006 Charger Daytona, is a Mopar low restriction drop in replacement air filter (K&N makes them for Dodge)
No headers, no CAI, no other physical modes. However the latest Super Chips was loaded.

WOW!

 

Maybe I missed it in the last thread but what brand and model tires did you put on. They look to be doing good for you ( -4/10's and +5 mph in the quarter is not too shabby).

Redbeard

 

Everyone seems to miss the point. It is not the tire compound, it is the change in diameter. Essentially it gives me a higher final drive ratio. The magic seems tobe in that the smaller tire diameter seems to make the car better match the engine torque and horsepower curves, allowing better acceleration. Instead of adding HP, using CAI, headers, or whatever. Modifying the final drive ratio by changing tire diameter, instead ofchanging say, the rear end ratio's in the differential yielded an unexpectedly large gain in performance.It also lowered the car by .5" reducing drag.

FYI the tires are









Michelin Pilot Sport

235/50ZR-18 97Y
I think it is the tire size, not the type that made the difference.

If I did not see it with my own two eyes I would not believe it!

 

Got the message and agree with it totally. Now I have the stock rims free I will putsome smaller than stock drag radials on them for the track. Do you think 27.25 diamater is the sweet spot?

 

I have no clue... But you could push me over with a feather with the results I got... Totally unexpected. my 60 foot time was a 2.62, and I did have wheelspin. So if you could "hook-up" better, you may get low 13's...

 

Hey Mango, after thinking further, it may not be such a good idea to put smaller tires on the back... This will leave the car with a poor aerodynamic profile, front is taller than the back. This would be good for weight transfer to the rear wheels on launch, but as you approach 100mph at the end of the 1/4 mile your front end might get light, and the air going under the car may cancel out any improvements...

I'll attach a photo next time, but I swear it looks like I put a lowering kit on my car. Yes I know it is only a .5" lower, but you can really see it. It should lower the C/D of the car also with less frontal area...

 

I plan to put the narrowest tire I can on the front rims to balance it out, just have to make sure the tire height is right.

 

That would be COOL!

Two thumbs waay up!

 

Just me, poking my head back in this section of the site

I posted the exact same thing to the truck guys a few weeks ago and basically got nowhere. I also took a full inch off the overall height of my tires (thereby losing a whole half-inch of vehicle height) and noticed a very noticable improvement in acceleration. By my poor math skills, it's like me going from a 3.92 rear to a 4.03 or so. Since they're 305/50/20, it's not like they're exactly tiny or hurt the truck's performance in non-pavement applications. I don't pretend to be a mud bogger so I'll gladly take the increase in power.

 

I wouldn't completely discount the tire compound component. True that with a shorter tire, you are effective lowering the final drive ratio (numerically raising it) resulting in more torque multiplication, but if the tire slips you lose power. The Pilot Sport is marketed by Michelin as a performance tire while the original Michelins are marketed as touring tires. The touring tires are tuned more toward ride quality than performance tires. Things like wet traction and tread life have a higher priority for a touring tire. If you check the two tire series out on the Michelin web site, you'll see these differences. Things like sidewall flex and tire compound are big components in making tires do what they're designed to do.

More than once just replacing tires have made radical changes to the personality of my vehicles. I had a set of tires on my pickup that wouldn't grip at all. It was a real handful to drive with those donuts. It would get squirrely if I ran through a puddle of dog wee (chuahua wee at that)! Made winter driving an adventure. Fortunately, their wear was as bad as their traction so after a couple of years I replaced them with a set of Pirellis. We're talking day and night here. I could now accelerate up drives and on ramps that I used to have to feather the throttle to keep from breaking the tires loose on. I would have gotten the Michelins but the tire store only had 3 of those on hand and 8 Pirellis and I didn't want to have to come back. I realize that this is a more extreme example but it does illustrate the differences that rubber compounding makes.

I think that you will find that a combination of the shorter tire AND better grip has given you the numbers. You might want to play with air pressure to further tune this. Since we are talking straight line racing, you could lower your rear pressures to reduce rolling radius (lowering the car and effective lowering drive ratio more) and plant more tread on the track. At 25 psi or lower the tire pressure monitor will whine but you'll know why. Bump up the fronts to max rated pressure to reduce rolling resistance. Don't forget to reset the pressures before you drive home though.

I've been considering a set of Pilot Sports to replace those on my car and my wife's Chrysler 300m Special. I like the wet traction of the Michelin's (important here in the Pacific Northwest). How would you compare the two tires for ride quality? I'm asking this more for my wife's car. I can trade a smoother ride for better handling but she likes the ride quality that she has. If there isn't a big difference in ride, she would probably be game to go with the performance series.

Have fun and have a safe and Happy New Year!!

Redbeard