help with size/offsets

Jamaica · 12-22-2010, 03:43 PM

Quote:

Originally Posted by bullitt5897

With 18's you will need atleast a 2+" drop... that's for sure!

hey bud i called you back last night. Ill call back today. Looks like i need a new painter lol

bullitt5897 · 12-22-2010, 04:00 PM

make sure its the right number lol i didnt get any calls last night...

gozfast · 12-22-2010, 04:59 PM

Quote:

Originally Posted by bullitt5897

Adding front tire tread width while giving you a larger contact patch will add the following negative attributes:

Tire wandering Aka bump steering
Extra Understeer
Slower transitions
Slower acceleration

Most if not all of these items can be addressed and mitigated *sp* as much as people like running squared setups I typically don't as per my driving style at the track.

Bullitt, I'm planning on a 275 F / 285 R on 20x10 +35 and 20x10.5 +15 rims. From my understanding-

Bump steer: Increases when the rim face is extended further from the pivot point, increasing leverage. With increased offset on a wider rim (+35 on a 10" vs +22 on a 9.5") the maximum lever arm would be equal, therefore no increased bump steer than the narrower wheel. People seem to feel the 9.5 + 22 is acceptable.

Understeer: Everyone except yourself has stated that a wider front tire will reduce understeer not increase it. I have Stillen sways and the front still pushes.

Slower transitions: True, but I will be autocrossing with my original sport rims not the wider 20X10 front I'm planning on getting. I don't expect many violent transitions on my daily commute.

Slower accereration: I believe this will be negligible with a quality lightweight rim.

A 255 section width tire is designed for a maximum 9.5" rim width. You run the same tire on a 10" rim, outside of the designed application.

You say more tire up front is bad, yet you want to go to an even bigger 285 tire in your next setup.

Bump steer is bad, but you want to extend the rim face out even further on a 11" front rim when you install the widebody.

You don't like square setups. Why do all the racers use them? I don't need bigger tires in the back, I don't have 1000HP (I am jealous though)

Don't get me wrong, I know you have the most badass car on this site, and definitely know more than I do. I just hope you could straighten me out on what appears to be conflicting information. Please don't look at this post as an attack or insult in any way, I'm just looking to understand.

destinyZ · 12-22-2010, 06:06 PM

^^^ Respectfull criticism anyone? Good questions looking forward to bullitt's answers. I'm sure he has something to say about that.

bullitt5897 · 12-22-2010, 07:11 PM

gozfast,

I respect your input and questions let me clarify a little for you and other readers:

When I was referring to bump steer I was not referring to the technical term bump steer. however, I was referring to wheel tracking hence why i put tire wandering because when your tire gets larger any bumps whether it is sealer strip or uneven payment can and often almost snatch the wheel out of your hands. That was my fault for not using the proper term. Larger tires are more prone to this but like I said all of this can be mitigated.

As far as understeer is concerned I do smaller more technical tracks which have a lot of switchbacks, flat turns and mainly off cambered turns. The larger tires up front resembling a squared setup do not give me the feel "I" want in a turn. A successful turn for me I find that I am four wheel drifting toward the turn exit under power. When I had more of a squared setup the front and rear would push then the front would just let go when I was under power and on acceleration out. I had to add camber and toe out "slightly" in the front to counteract that affect.

slower transitions is just the nature of going bigger its a lot to move around not so much the weight aspect... look at it this way take your stock tires and the fronts are very narrow now roll circles with the fronts its easy and the circles are relatively small. Now take your rears and try to do the same... put aside the weight for a moment and you will notice the tire must gain more of an angle and edge to due the same size circle and you have to work harder to transition that turn. Adding camber helps with the transition problem.

Acceleration is hampered only by small amounts its just extra friction that you have to overcome but you do gain a larger contact patch for braking so where you had to take longer to accelerate you can stay on the gas longer and wait later to brake. There is always pros and cons of going bigger.

I ran a 255 because that was what was available in my Falken sponsorship and what fit within the fenders on my car.

As far as my new setup I have full control over my camber, toe and caster thanks to my spc suspension parts. This allows me to run those crazy sizes and mitigate those affects. Now again, this car is not all track and is a daily driver and a show car so I have to give up in some areas to accommodate other areas. I am going wider to accommodate the extra power thats all. I am keeping the staggered setup though.

Again, my preferences are tailored to my driving style... I came from Motorcycle racing and a lot of my bad driving habits stem from that experience. I scared the CHIT out of several instructors going into turns but once we got halfway through the turn they were like I cant believe this line works and as I powered out the turn they were surprised at the corner exit speed I carried. Now several years later I have left alot of my bad habits (and by bad habits I am referring to bike habits) to my bikes and I have adopted true car racing lines which have made me more consistent and faster. I still brake really late though haha I feel if my bike can do it so can the car

lol

Again, I respect your criticism and concern. I am not the be all end all when it comes to this stuff and we are always learning and being corrected by others so thank you for giving me the chance to further explain.

-Mike

gozfast · 12-23-2010, 09:35 AM

I've been racing motorcycles my whole life also, 40 years worth. MX, roadracing and supermoto. Bullitt, it sounds like you like to "square off" the corners. I'm still working on the smooth lines myself. My bike racing days however, are over after a recent motocross accident. I broke both legs and shattered both my ankles, breaking eight bones total when I waaaayy over jumped a double. (wrong gear, oops) I've spent the last two years trying to walk again. I actually ordered my car without a test drive because I still had casts on. That's why I bought the 370. There's a saying that goes: With age, comes a cage.

12-22-2010, 04:00 PM	#17 (permalink)
bullitt5897 Premium Member Join Date: Jan 2009 Location: North GA Posts: 6,831 Drives: Twin Turbo Z34 Rep Power: 3682	make sure its the right number lol i didnt get any calls last night... __________________ *Shop Cars: 2013 318whp Nismo VspecII 370z SOLD, 2009 1000hp+ 93oct 4.0L TT 370z Fast Intentions STAGE 4 #054*

12-22-2010, 06:06 PM	#19 (permalink)
destinyZ Enthusiast Member Join Date: Apr 2010 Location: Guam, USA Age: 36 Posts: 415 Drives: FROM INDIANA Rep Power: 15	^^^ Respectfull criticism anyone? Good questions looking forward to bullitt's answers. I'm sure he has something to say about that. Last edited by destinyZ; 12-22-2010 at 06:35 PM.

12-22-2010, 07:11 PM	#20 (permalink)
bullitt5897 Premium Member Join Date: Jan 2009 Location: North GA Posts: 6,831 Drives: Twin Turbo Z34 Rep Power: 3682	gozfast, I respect your input and questions let me clarify a little for you and other readers: When I was referring to bump steer I was not referring to the technical term bump steer. however, I was referring to wheel tracking hence why i put tire wandering because when your tire gets larger any bumps whether it is sealer strip or uneven payment can and often almost snatch the wheel out of your hands. That was my fault for not using the proper term. Larger tires are more prone to this but like I said all of this can be mitigated. As far as understeer is concerned I do smaller more technical tracks which have a lot of switchbacks, flat turns and mainly off cambered turns. The larger tires up front resembling a squared setup do not give me the feel "I" want in a turn. A successful turn for me I find that I am four wheel drifting toward the turn exit under power. When I had more of a squared setup the front and rear would push then the front would just let go when I was under power and on acceleration out. I had to add camber and toe out "slightly" in the front to counteract that affect. slower transitions is just the nature of going bigger its a lot to move around not so much the weight aspect... look at it this way take your stock tires and the fronts are very narrow now roll circles with the fronts its easy and the circles are relatively small. Now take your rears and try to do the same... put aside the weight for a moment and you will notice the tire must gain more of an angle and edge to due the same size circle and you have to work harder to transition that turn. Adding camber helps with the transition problem. Acceleration is hampered only by small amounts its just extra friction that you have to overcome but you do gain a larger contact patch for braking so where you had to take longer to accelerate you can stay on the gas longer and wait later to brake. There is always pros and cons of going bigger. I ran a 255 because that was what was available in my Falken sponsorship and what fit within the fenders on my car. As far as my new setup I have full control over my camber, toe and caster thanks to my spc suspension parts. This allows me to run those crazy sizes and mitigate those affects. Now again, this car is not all track and is a daily driver and a show car so I have to give up in some areas to accommodate other areas. I am going wider to accommodate the extra power thats all. I am keeping the staggered setup though. Again, my preferences are tailored to my driving style... I came from Motorcycle racing and a lot of my bad driving habits stem from that experience. I scared the CHIT out of several instructors going into turns but once we got halfway through the turn they were like I cant believe this line works and as I powered out the turn they were surprised at the corner exit speed I carried. Now several years later I have left alot of my bad habits (and by bad habits I am referring to bike habits) to my bikes and I have adopted true car racing lines which have made me more consistent and faster. I still brake really late though haha I feel if my bike can do it so can the car lol Again, I respect your criticism and concern. I am not the be all end all when it comes to this stuff and we are always learning and being corrected by others so thank you for giving me the chance to further explain. -Mike __________________ *Shop Cars: 2013 318whp Nismo VspecII 370z SOLD, 2009 1000hp+ 93oct 4.0L TT 370z Fast Intentions STAGE 4 #054*

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12-23-2010, 09:35 AM	#21 (permalink)
gozfast Base Member Join Date: Mar 2010 Location: Earth Posts: 67 Drives: 370Z Sport Rep Power: 15	I've been racing motorcycles my whole life also, 40 years worth. MX, roadracing and supermoto. Bullitt, it sounds like you like to "square off" the corners. I'm still working on the smooth lines myself. My bike racing days however, are over after a recent motocross accident. I broke both legs and shattered both my ankles, breaking eight bones total when I waaaayy over jumped a double. (wrong gear, oops) I've spent the last two years trying to walk again. I actually ordered my car without a test drive because I still had casts on. That's why I bought the 370. There's a saying that goes: With age, comes a cage.