05-28-2020, 10:42 PM | #1 |
Drives: ‘15 RH Z/28 #185, Hennessey #006 Join Date: Aug 2019
Location: Kansas
Posts: 42
|
Understeer in Relation to Tire Size
Alright, y'all. I'm calling upon the collective expertise and experience of everyone here once more. I've been tearing this forum apart for an answer, but I haven't quite got one that I'm totally satisfied with.
So, most of us know that a staggered set of tires, say 305's in the front and 325's in the rear, will cause understeer. However, just "understeer" is difficult to quantify. Those with experience with this set up, especially if you track your rig, what are your thoughts? If you drive your Z at 8/10th's, is is noticeable? How about around town? Thanks in advance! Also, pictures are more than welcome. Square 325 set up pictures are also cool! |
05-29-2020, 12:29 AM | #2 |
Account Suspended
|
Fatter tires in the rear can produce noticeable under-steer. The more rear-biased the
more under-steer. The front tires lose traction first with wider ones on the back, which causes under-steer. However alignment, spring rate, sway-bars and very importantly, driving technique also play a big role. So, if you want the larger tires in back, then modify the suspension to compensate. |
05-29-2020, 09:41 AM | #3 | |
Drives: 15 RH Z/28, 23 RB2SS1LE, 23LT1VOM Join Date: Dec 2012
Location: So Cal
Posts: 817
|
Quote:
Most folks wouldn't notice the difference , certainly at civilized speed. At 8/10ths it would be, to some,but you can dial it out with the pedal on the right The gen 6 1LE's and ZL1LE's all come with a smaller contact patch up front, and they are well balanced cars right out of the box. YMMV |
|
05-29-2020, 11:10 AM | #4 |
Drives: 2015 Z28 Join Date: Nov 2016
Location: Michigan
Posts: 136
|
I didn't notice much with a staggered set-up. The rims are different widths anyway which will change the specs of the tire anyway. The difference between a 305/325 GY 3R is not much as say a 305/325 Trofeo.
|
05-29-2020, 12:28 PM | #5 |
Instagram: Sangstah
|
Going from a staggered setup to a square setup makes a huge difference, definitely felt the difference in the canyons.
__________________
2019 SS 1LE - "CaSSandra" 2014 SS - "AleSSandra - Sold" 94 Z28 - Sold
Follow the build https://www.camaro6.com/forums/showthread.php?t=612717 |
05-29-2020, 07:13 PM | #6 |
Drives: 2015 Z/28; 1969 Camaro SS Join Date: Nov 2015
Location: York, PA
Posts: 805
|
I think you would need to be a professional driver to notice any measurable difference. If you notice understeer from a 305 to 325 on the street you probably shouldn’t be on the street.
Also a Trofeo to something like an RE11 street tire can’t be compared, staggered or not. From what I read they did a square setup with Trofeos because it tweaked a little bit more out on the N’Ring. |
05-29-2020, 09:00 PM | #7 | |
Drives: '94 Z28+ '15 Z/28 Join Date: Jun 2009
Location: Cheektowaga, NY
Posts: 1,275
|
Quote:
Any "street" evaluation will be flawed because streets aren't prepped, the tires aren't up to temp, pressures could be wrong, etc, etc. I can give you lots of feedback on real world testing of 305's square when pushing hard from 20mph-60mph. But that's with a Potenza RE-71R, not a Trofeo. Not sure if other tires will behave different. My car has substantially more front end grip than it does in the rear, period. Granted a lot of times when I'm turning the wheel, I'm standing on the brakes, which drives them down, but even in a fast-ish slalom, the tail will step out before the front will push. I can get it to push in certain situations, but mostly the rear is the end that misbehaves.
__________________
1973 Mach 1, 351C cruiser
'15 Z/28 Red Hot, A/C 1980 Z28- resto-mod project 1979 Y84 Trans Am 1986 IROC-Z |
|
06-09-2020, 10:27 AM | #8 |
Drives: 2015 SS/RS 1LE Join Date: Dec 2014
Location: Milwaukee, WI
Posts: 537
|
I have tried to remove the small amount of under-steer my 1le had built in. I have changed many things, it's pretty much a Z28 lite now. Just like Joelster says, my car has more grip in the front than the rear. It will push the front tires on the street, it is on colder tires, a tight very slow turn with moderate acceleration, like a u turn or something similar. If I am pushing the car hard around 90deg corners I will get a nice neutral slide as the front will break the same as the rear and with a little more throttle the rear will step out rotating the car a little more. If I went with a 305 in the rear I think I would lose the ability of rotating the car with the throttle.
|
06-10-2020, 02:40 PM | #9 |
I have run many tire setups on this car, although not staggered, I still adjusted alignment for each tire setup. My RE11 rain track tires need the rear loosened slightly, while the trofeo's handled the stock track alignment well (needed slightly more camber than suggested), and I just got some 315 R888Rs that will need some refinement at the track too. Tire pressure, suspension setup (specifically stiffness of sway bar), alignment, driving technique all play a factor as most people have stated. I had Randy Pobst in my endurance car in January that was tail happy, he completely disconnected the rear sway bar for his driving technique. We were within half a second of each other at Laguna Seca, the sway bar gave him an extra .2 seconds.
__________________
2015 Camaro Z/28 Black
Sold: 2010 Camaro 1SS/RS |
|
07-06-2020, 09:22 PM | #10 |
Raging Bull Reborn
Drives: '09 CGM Z063LZ '15 RH Z/28 #0631 Join Date: Mar 2012
Location: Broken Arrow OK
Posts: 765
|
Why don’t you just run four 325s? They fit with enough room to spare front and back. The Michelin Pilot Cup2s allow the car to corner just like the older trofeo-r’s .... they corner like a scalded dog...
And at 12 to -12.5” wide I get comments at every cruise in
__________________
Toy 1 '15 RH Z/28 w/AC & Radio S/N 0631 Toy 2 '09 CGM Z06 3LZ My DD: '17 Ford Mustang GT Her DD: '14 F150 Ecoboost 3.5 |
07-06-2020, 09:59 PM | #11 | |
Drives: ‘15 RH Z/28 #185, Hennessey #006 Join Date: Aug 2019
Location: Kansas
Posts: 42
|
Quote:
|
|
07-06-2020, 10:36 PM | #12 |
Drives: 2010 RS Inferno Orange Metallic Join Date: Mar 2010
Location: Albany, Ga.
Posts: 3,399
|
so why do i experience more oversteer in my car vs understeer
I have a 2010 V6 2lt Auto with 275 45 20"s on Front and 315 35 20's on back if i push it hard the back breaks loose first, which of course then i steer with the throttle I have driven it hard and the front does not brake loose first. I been driving the car for ten years
__________________
PCP Hideaway Headlight Covers, BBK Headers & High Flow Cats, ZL1 Add-ons Wicker Bill, TL1/ZL1 Hood Insert, Gen5 DIY Frameless Mirror, ABL Dash Lighting an My link Navigation, Blacked out Rear Bowtie, all Sylvania led Turn Signals, Ceramic Window Tint By Nicks, MBRP Exhaust tips, GEN5 DIY Virginia Legal DRL Harness, Painted Brake Calipers, Vittesse Throttle Controller, Heritage Grill, Diode Dynamics Led Lighting, Manual Shifter Boot, Paddle Shifters, CNC Throttle Body, Trifecta Tune, RX Catch Can & Breather, Trunk Black out and Side Grills, Chevorlet door Sills.
|
|
|
Thread Tools | |
|
|