Difference in drag radial overall height - Camaro5 Chevy Camaro Forum / Camaro ZL1, SS and V6 Forums

11syn3rgy · 12-03-2013, 10:26 PM

Hey guys,

I'm probably going to get 275/45R18 M&H drag radials and plan to keep my stock 20's up front for drag racing. I realize that many guys are running this combo and I wanted to know if the 1" overall height difference will cause any issues? Will my tuner need to account for this or is this not enough of a height difference to worry about? I only visit the track 3 or 4 times a year.

What are you guys doing?

Thanks!

blazzin1 · 12-04-2013, 06:29 AM

Actually, you're the first person I've EVER heard of running those tires!!! Most folks run a 305/45R18 (same height as stock). Technically, no, it shouldn't cause a problem, but I've read many stories about some cars that are either more or less sensitive to the tire height difference. If it does cause a problem, it will just be "lights" on the dash, and will reset itself once you switch the tires/wheels back out.

Padre · 12-04-2013, 06:36 AM

You can change the diameter of the tires in the tune. This will help keep your speedo and your shift points accurate, so if your tuner is in the tune anyway, it's simple to do.

Padre

11syn3rgy · 12-04-2013, 08:28 AM

Ok, thanks guys!

2SSCAMARO · 12-04-2013, 10:25 AM

You shouldn't have any problems. I ran nitto NT05R 285/40/18's that properly inflated are only 26". I ran them at 18 psi which took them below 26". I never threw any codes or had any issues with the stabiltrac.

11syn3rgy · 12-04-2013, 11:09 AM

Quote:

Originally Posted by 2SSCAMARO

You shouldn't have any problems. I ran nitto NT05R 285/40/18's that properly inflated are only 26". I ran them at 18 psi which took them below 26". I never threw any codes or had any issues with the stabiltrac.

Did you have your tuner adjust for the shorter tire or shift point changes?

Camarojt · 12-04-2013, 02:25 PM

The difference in tire size will slightly affect your shift points if you are already tuned for a stock height tire. I just did this exact same thing yesterday but I went from a 26.5 rear back up to 28". Took my tuner less than a min to key in the tire size and update that in my tune. If he has already did your work for you will all ur mods, I would think he would do this just as a good appreciation token. If he charges you $100 to do it, then you have 2 choices, pay it (which IMO is ridiculous) or tap shift it urself at the track, being that you only go a few times a yr.
it might not even need adjusting. Just depends on where you are tuned to shift at now vs the difference in tire size.

What are ur shift points now and how high do you cross the finish line?

11syn3rgy · 12-04-2013, 04:15 PM

Quote:

Originally Posted by Camarojt

The difference in tire size will slightly affect your shift points if you are already tuned for a stock height tire. I just did this exact same thing yesterday but I went from a 26.5 rear back up to 28". Took my tuner less than a min to key in the tire size and update that in my tune. If he has already did your work for you will all ur mods, I would think he would do this just as a good appreciation token. If he charges you $100 to do it, then you have 2 choices, pay it (which IMO is ridiculous) or tap shift it urself at the track, being that you only go a few times a yr.
it might not even need adjusting. Just depends on where you are tuned to shift at now vs the difference in tire size.

What are ur shift points now and how high do you cross the finish line?

He has it tuned to shift around 6400 rpm currently, which should be plenty safe. Sounds like most of the guys breaking stuff at my level is from over revving the engine. I'm fine with it being a "safe" tune. I will datalog it in the spring once I get the new tires and see what he thinks, I just wanted to see what everyone else was doing. I'm only trapping at 119.5 currently and still have plenty of 4th gear left when I'm at the track. Maybe it won't really matter?

Camarojt · 12-04-2013, 05:54 PM

If you have plenty of gear left then you will be fine. He might need to adjust your tire size difference Bc now it will be a little off but 1" is barely going to be noticeable.

If you are going to buy new tires, why not run what most guys run which is the 305/45/18? Then your tune is the same Bc ur tires will be same height as stock.

11syn3rgy · 12-04-2013, 07:10 PM

Quote:

Originally Posted by Camarojt

If you have plenty of gear left then you will be fine. He might need to adjust your tire size difference Bc now it will be a little off but 1" is barely going to be noticeable.

If you are going to buy new tires, why not run what most guys run which is the 305/45/18? Then your tune is the same Bc ur tires will be same height as stock.

Yeah, that's a fair question. I might still do that but I like the idea of a slightly shorter tire in the rear that should effectively help my gearing a little bit? Plus, always been a fan of M&H. I think both tires would do a great job. This is why I'm trying to be informed before I pull the trigger on either DR. Seems like the M&H could also be a little lighter since they are only a 275 tire and the MT is a 305?

white ZL1 · 12-04-2013, 07:49 PM

The M/T 305 is 32lbs per tire, and the 275 M&H is 29.9lbs per tire.
The difference from the stock height 28.8" tire to the 28" M&H is going to be negligible, and since your car is a 2011 the only shift it's going to affect is the 1-2 shift since that's the only one that is based only off of MPH. The 1-2 shift should be about 150rpm higher with the 28" tire if your tune is based off of a 28.8" tire height. So 6550ish instead of 6400.
2-3 and 3-4 should shift based off of RPM, so they should still happen around 6400rpm.

11syn3rgy · 12-04-2013, 08:07 PM

Quote:

Originally Posted by white 2SS/RS

The M/T 305 is 32lbs per tire, and the 275 M&H is 29.9lbs per tire.
The difference from the stock height 28.8" tire to the 28" M&H is going to be negligible, and since your car is a 2011 the only shift it's going to affect is the 1-2 shift since that's the only one that is based only off of MPH. The 1-2 shift should be about 150rpm higher with the 28" tire if your tune is based off of a 28.8" tire height. So 6550ish instead of 6400.
2-3 and 3-4 should shift based off of RPM, so they should still happen around 6400rpm.

Cool. Great info. Thanks man!

VADER SS L99 · 12-04-2013, 08:59 PM

Quote:

Originally Posted by 11syn3rgy

Yeah, that's a fair question. I might still do that but I like the idea of a slightly shorter tire in the rear that should effectively help my gearing a little bit? Plus, always been a fan of M&H. I think both tires would do a great job. This is why I'm trying to be informed before I pull the trigger on either DR. Seems like the M&H could also be a little lighter since they are only a 275 tire and the MT is a 305?

The con about that shorter tire is that you will have less sidewall height and less tire width with the 275. Traction is gained with sidewall height and tread width. IF and that's a big IF you can dead hook with the 275 it will possibly make you faster than the 305 but if you can't hook with the 275 that gearing advantage is thrown right out the window. If your wheels are at least 10.5" wide you might want to also consider the NT05R 315/40R18 which is 28" I believe. I still think nothing will hook better than that MT 305/45R18 though.

rtcat600man · 12-04-2013, 09:07 PM

The other issue you might experience is a total shut down of all stabil trak,, traction control and abs systems.

I run a smaller dia. rear drag radial and the system senses there is an issue with a difference in tire dia.

Not sure when this occurs, but I thought I read somewhere it is close to 1" difference and you are close to that.

Certainly does not hurt, but the dash will light up like it is Christmas, you will not have accurate readings.

I drive from home to the track and back again with my set-up running a 265/40/18 rear tire.

12-03-2013, 10:26 PM	#1
11syn3rgy JT Synergy RS/2SS Drives: 2011 Camaro RS/2SS (L99) Synergy Join Date: May 2013 Location: Hager City, WI Posts: 697	Difference in drag radial overall height Hey guys, I'm probably going to get 275/45R18 M&H drag radials and plan to keep my stock 20's up front for drag racing. I realize that many guys are running this combo and I wanted to know if the 1" overall height difference will cause any issues? Will my tuner need to account for this or is this not enough of a height difference to worry about? I only visit the track 3 or 4 times a year. What are you guys doing? Thanks!

12-04-2013, 06:36 AM	#3
Padre Only drives on Sundays Drives: '16 2SS A8 NPP MRC NGray Join Date: Feb 2011 Location: Dalton, GA Posts: 2,500 View My Garage	You can change the diameter of the tires in the tune. This will help keep your speedo and your shift points accurate, so if your tuner is in the tune anyway, it's simple to do. Padre __________________ OLD HOTNESS: The "Heretic": '11 2SS/RS L99 A6 Black/Inferno. Build Journal, Videos D1SC GT9 JBA-LT = 720/680 \| 10.330 @ 133.61, 1.546 sixty... Camaro King at ECS V, Darlington. NEW HOTNESS: '16 2SS A8 NPP MRC. Bone Stock, 1/8th: 8.051 @ 89.44, 1.919

12-04-2013, 10:25 AM	#5
2SSCAMARO Drives: 2010 Camaro Auto Join Date: Mar 2010 Location: Fl Posts: 1,164	You shouldn't have any problems. I ran nitto NT05R 285/40/18's that properly inflated are only 26". I ran them at 18 psi which took them below 26". I never threw any codes or had any issues with the stabiltrac. __________________ Just livin' life

12-04-2013, 09:07 PM	#14
rtcat600man having FUN now 13.66@101 Drives: 2010 2LT IOM Join Date: Nov 2009 Location: Clarkston, Michigan Posts: 9,230 View My Garage	The other issue you might experience is a total shut down of all stabil trak,, traction control and abs systems. I run a smaller dia. rear drag radial and the system senses there is an issue with a difference in tire dia. Not sure when this occurs, but I thought I read somewhere it is close to 1" difference and you are close to that. Certainly does not hurt, but the dash will light up like it is Christmas, you will not have accurate readings. I drive from home to the track and back again with my set-up running a 265/40/18 rear tire. __________________ MY BUILD

12-04-2013, 06:29 AM	#2
blazzin1 Drives: 2010 2SS/RS R6P Join Date: Nov 2008 Location: St. Cloud, FL Posts: 4,845 View My Garage	Actually, you're the first person I've EVER heard of running those tires!!! Most folks run a 305/45R18 (same height as stock). Technically, no, it shouldn't cause a problem, but I've read many stories about some cars that are either more or less sensitive to the tire height difference. If it does cause a problem, it will just be "lights" on the dash, and will reset itself once you switch the tires/wheels back out.

12-04-2013, 08:28 AM	#4
11syn3rgy JT Synergy RS/2SS Drives: 2011 Camaro RS/2SS (L99) Synergy Join Date: May 2013 Location: Hager City, WI Posts: 697	Ok, thanks guys!

12-04-2013, 02:25 PM	#7
Camarojt Drives: 2011camaro SS Join Date: Nov 2012 Location: Allen, Tx Posts: 2,202	The difference in tire size will slightly affect your shift points if you are already tuned for a stock height tire. I just did this exact same thing yesterday but I went from a 26.5 rear back up to 28". Took my tuner less than a min to key in the tire size and update that in my tune. If he has already did your work for you will all ur mods, I would think he would do this just as a good appreciation token. If he charges you $100 to do it, then you have 2 choices, pay it (which IMO is ridiculous) or tap shift it urself at the track, being that you only go a few times a yr. it might not even need adjusting. Just depends on where you are tuned to shift at now vs the difference in tire size. What are ur shift points now and how high do you cross the finish line?

12-04-2013, 05:54 PM	#9
Camarojt Drives: 2011camaro SS Join Date: Nov 2012 Location: Allen, Tx Posts: 2,202	If you have plenty of gear left then you will be fine. He might need to adjust your tire size difference Bc now it will be a little off but 1" is barely going to be noticeable. If you are going to buy new tires, why not run what most guys run which is the 305/45/18? Then your tune is the same Bc ur tires will be same height as stock.

12-04-2013, 07:49 PM	#11
white ZL1 Drives: none Join Date: Aug 2011 Location: DFW area Posts: 1,844	The M/T 305 is 32lbs per tire, and the 275 M&H is 29.9lbs per tire. The difference from the stock height 28.8" tire to the 28" M&H is going to be negligible, and since your car is a 2011 the only shift it's going to affect is the 1-2 shift since that's the only one that is based only off of MPH. The 1-2 shift should be about 150rpm higher with the 28" tire if your tune is based off of a 28.8" tire height. So 6550ish instead of 6400. 2-3 and 3-4 should shift based off of RPM, so they should still happen around 6400rpm.