[Joe240]

Originally Posted by TajoMan

https://ls1tech.com/forums/cadillac-...alignment.html

As you see in the picture from above link, wider tire (even with properly wider rim) does not necessarily have bigger contact patch.
It just changes the shape of contact patch. (elongated more on sideway)

Contact patch area is solely function of weight of the car and tire pressure. (within reasonable tire width of course. not talking about bicycle tire like width)

As mentioned above, proper rim witch is for optimal sidewall support.
The Tirerack article just says 'tire width' not 'contact patch'.

I love people who bring supporting evidence to an argument Not being sarcastic, seriously glad you are linking to things like this because it helps everyone who takes the time to read.

This link though, he had to adjust his camber to increase his contact patch. what I'm referring to is leaving everything else the same (including camber and the vehicle weight and passenger weight, tire pressure, ambient air, weather, etc.) a wider tire on the correct width wheel will increase contact patch

[casper83]

I’m with olehead. So many variations that can affect a run. As an example I put down some of my runs made on different tire and rim combinations. The different combos end up with different tire diameters adding yet another variable.

My fastest 60’ times came on the stock 225 Cinturato. Who would have figured? They have also produced some of the quickest ¼ mile times. This is just a sample of runs, but without a doubt the TSW with MPSS 245’s has been consistently slower by a couple tenths in the quarter and slightly slower in the 60’.

OP, if your main goal is just to get in the 11’s, put in race gas and should get there with the current setup. I’m still of the opinion that root cause you need to look at the tune. A PS2 should be giving you much better trap speed.

[Maynard]

Originally Posted by Joe240

I love people who bring supporting evidence to an argument Not being sarcastic, seriously glad you are linking to things like this because it helps everyone who takes the time to read.

This link though, he had to adjust his camber to increase his contact patch. what I'm referring to is leaving everything else the same (including camber and the vehicle weight and passenger weight, tire pressure, ambient air, weather, etc.) a wider tire on the correct width wheel will increase contact patch

No, you are mixing up width and size. SIZE (area in square inches) of contact patches is always the same for a given weight and air pressure. Shape differs, based on width of the tire. The air pressure is what holds the car up - basic math. For example, a 3000# car on tires at 30psi will have a contact area of 100 in2, or 25 in2 per wheel (100 in2 at 30 pounds per). That can be 4 patches 10" wide and 2.5" long, or 5" wide and 5"long. Camber won't change this, it just shifts it to the outside edge, more shape-changing (in drags, this makes the tire function like it is much narrower, so camber isn't usually good for dragsters; on track it means the tire is squared up when leaning into a turn, so very good).

All of that is only a small piece of drag launches - there is all kinds of fancy physics around the way the wrinkling tire sidewall stores and then releases energy, along with leverage and altered diameter (and all the weight-transfer factors). Not sure how much of this applies to a road tire like an MPSS, but it is what drag radials are designed for. If you want to drop times, I'd consider some dedicated wheels/tires for sure.

[Joe240]

Originally Posted by Maynard

No, you are mixing up width and size. SIZE (area in square inches) of contact patches is always the same for a given weight and air pressure. Shape differs, based on width of the tire. The air pressure is what holds the car up - basic math. For example, a 3000# car on tires at 30psi will have a contact area of 100 in2, or 25 in2 per wheel (100 in2 at 30 pounds per). That can be 4 patches 10" wide and 2.5" long, or 5" wide and 5"long. Camber won't change this, it just shifts it to the outside edge, more shape-changing (in drags, this makes the tire function like it is much narrower, so camber isn't usually good for dragsters; on track it means the tire is squared up when leaning into a turn, so very good).

All of that is only a small piece of drag launches - there is all kinds of fancy physics around the way the wrinkling tire sidewall stores and then releases energy, along with leverage and altered diameter (and all the weight-transfer factors). Not sure how much of this applies to a road tire like an MPSS, but it is what drag radials are designed for. If you want to drop times, I'd consider some dedicated wheels/tires for sure.

I see what you’re talking about, the mathematical weight distribution of the car based on the tire pressure. 3000lbs/30psi=100sqin/4Tires=25sqin per tire of contact patch. You are correct, I was mixing up shape and size when talking about contact patch

[bryan_G01]

you need 20-30 more hp to get you into the 11s.

Fuel, run some 2gal of ms109.
Add a jb+, it will work and is good for 30whp or .2 in the 1/4mi but not everyone likes to double dip tunes.
loose weight, remove everything from the car you can.


I ran my 11s on oem wheels and stock runflat all seasons.

[B58togo]

Originally Posted by olehead

Lot of info all good but after many too many years and 1000's of passes on both the 1/8 and 1/4 in cars as fast as mid 9 - Track prep - Weather - make a huge difference at any time on any car - watch any drag racing show - it is all about getting off the line and maintaining traction - cars like the X drive BMW automatic pretty much point and shoot cars - I prefer brake boost but launch control is fine if you are not worried about RT - these little coupes are great to about 800 ft and then unless you have turbo upgrades erc they just do not have the HP at the big end

I used to think these cars were on the weak side on the second half, but after flashing BM3 Stage 2 93 I'm picking up 24 mph. 11.9 @ 118 on the dragy. JB4 couldn't do that. A couple days ago I was merging onto the highway and there was a silver C7 base two lanes over. I forgot I was in manual mode and just rolled with it, 75-125 kept him in my blind spot all while staying in 5th. The torque curve is so fat on these cars, I think it just feels like top end is lacking. LSD, trans flash and E30 map are on the agenda in the next couple weeks. Shooting for 11.7 @ 120.

[MAILIYAT]

Originally Posted by B58togo

I used to think these cars were on the weak side on the second half, but after flashing BM3 Stage 2 93 I'm picking up 24 mph. 11.9 @ 118 on the dragy. JB4 couldn't do that. A couple days ago I was merging onto the highway and there was a silver C7 base two lanes over. I forgot I was in manual mode and just rolled with it, 75-125 kept him in my blind spot all while staying in 5th. The torque curve is so fat on these cars, I think it just feels like top end is lacking. LSD, trans flash and E30 map are on the agenda in the next couple weeks. Shooting for 11.7 @ 120.

higher tire pressure may help since the launch is not an issue with xdrive.
snaptube telegram web

[luchocamp]

Originally Posted by Conte_81

Hi All,

I have 2015 M235i. Car has Pure Stage 2 turbo, downpipe/intercooler/intake and a Remus axleback.

The car was tuned and made 406hp and 390tq at the wheels. My goal is to break I to the 11's. I ended up at 12.1 in the 1/4mi.

What else can I do? I've tried both launch control and brake boosting with DTC and DSC on/off.

try start in second gear M2

[luchocamp]

Originally Posted by casper83

I’m with olehead. So many variations that can affect a run. As an example I put down some of my runs made on different tire and rim combinations. The different combos end up with different tire diameters adding yet another variable.

My fastest 60’ times came on the stock 225 Cinturato. Who would have figured? They have also produced some of the quickest ¼ mile times. This is just a sample of runs, but without a doubt the TSW with MPSS 245’s has been consistently slower by a couple tenths in the quarter and slightly slower in the 60’.

OP, if your main goal is just to get in the 11’s, put in race gas and should get there with the current setup. I’m still of the opinion that root cause you need to look at the tune. A PS2 should be giving you much better trap speed.

amazing results with 225 Cinturato rft tires.
also G20 M340ix are getting 1.67 on street and 1.50 on US prepped track with those tires