|
|
|
|
Thread Tools | Display Modes |
|
12-08-2008, 10:15 AM | #1 |
Scooby Guru
Member#: 133146
Join Date: Nov 2006
Location: SC
Vehicle:07 FPgreen 7.37@95 WRX VF39+E85 12.0, 121mph |
which car will be faster?
we have 2 cars they are identical, they have the same power mods, same suspension mods, same everything but wheels and tires.
Car A: has some 18x9.5 wheels that weight 22 lbs and some 245/40/18 tires that weight 27 lbs Car B: has some 17x8 wheels that weight 14 lbs and some 215/40/17 tires that weight 18 lbs. **tires are the same brand and compound** Which will win on Auto cross, how about road racing, and drag? Idk I know one will more surface contact but the other will have less rotational mass. |
12-08-2008, 10:26 AM | #2 |
Scooby Specialist
Member#: 95916
Join Date: Sep 2005
Chapter/Region:
NESIC
Location: Rhode Island
Vehicle:2004 Impreza WRX 1998 Legacy GT Wagon |
grassroots did a pretty good article on this (using a miata) a few months back ... maybe you can find it on their website. it has test data and I found it pretty useful
|
12-08-2008, 10:29 AM | #3 |
Scooby Guru
Member#: 33782
Join Date: Mar 2003
Chapter/Region:
MAIC
Location: Milton Keynes, UK
Vehicle:96 3MI Racing search FIRST, then PM!!! |
Assuming the tires perform the same with sidewall/width ratio, slip angle etc...same driver, you really can't call it. Best guess is: B would win in all counts of forward acceleration so long as traction isn't an issue. B would loose in braking and cornering grip. Although A does have more work for the brakes to handle. Last edited by Homemade WRX; 12-08-2008 at 11:37 AM. |
12-08-2008, 10:30 AM | #4 |
Scooby Guru
Member#: 37359
Join Date: May 2003
Vehicle:2003 WRX |
There is also a significant gearing change due to tire diameters.
IMHO, there are too many unknowns. |
12-08-2008, 10:35 AM | #5 |
Scooby Guru
Member#: 33782
Join Date: Mar 2003
Chapter/Region:
MAIC
Location: Milton Keynes, UK
Vehicle:96 3MI Racing search FIRST, then PM!!! |
well that's why I said tire B would win acceleration, although I guess pending power levels/traps that could be requiring another gear shift...
|
12-08-2008, 10:54 AM | #6 | |
Scooby Specialist
Member#: 122980
Join Date: Aug 2006
Chapter/Region:
South East
Location: Raleigh, NC
Vehicle:2010 F150, 2013 CX-5 92 Miata 15 TTF/PTF/E3 |
Quote:
Code:
Stock Tire - 215/40R17 Tire 1 - 245/40R18 Section Width: 8.46 in 215 mm Section Width: 9.64 in 245 mm Rim Diameter: 17 in 431.8 mm Rim Diameter: 18 in 457.2 mm Rim Width Range: 7 - 8.5 in Rim Width Range: 8 - 9.5 in Overall Diameter: 23.77 in 603.75 mm Overall Diameter: 25.71 in 653.03 mm Sidewall Height: 3.38 in 85.852 mm Sidewall Height: 3.85 in 97.79 mm Radius: 11.88 in 301.75 mm Radius: 12.85 in 326.39 mm Circumference: 74.67 in 1896.6 mm Circumference: 80.77 in 2051.5 mm Revs per Mile: 875.0 Revs per Mile: 809.0 Actual Speed: 60 mph 100 km/h Speedometer1: 55.4 mph 92.4 km/h Speedometer Difference: - Speedometer Difference: 8.158% too slow Diameter Difference: - Diameter Difference: 7.55% |
|
12-08-2008, 11:31 AM | #7 |
Scooby Guru
Member#: 442
Join Date: Oct 1999
Chapter/Region:
NESIC
Location: RI/SE Mass
Vehicle:17 Imp Spurt 00 S2k |
All being equal, and same driver, I'd call it too close to tell. Too many other variables to say which will win based on just tires/wheels.
--KC |
12-08-2008, 12:08 PM | #8 |
Scooby Guru
Member#: 133146
Join Date: Nov 2006
Location: SC
Vehicle:07 FPgreen 7.37@95 WRX VF39+E85 12.0, 121mph |
so it seems that car should be about equal. Car A been faster on the acceleration department while Car B is faster on the corners and braking.
|
12-08-2008, 12:20 PM | #9 |
Add Lightness
Moderator Member#: 13699
Join Date: Dec 2001
Chapter/Region:
NESIC
Location: Hopkinton, MA
Vehicle:2021 Building It Better |
I've covertly put a "rallydecals.com" sticker on car A......now who wins?
jack |
12-08-2008, 12:25 PM | #10 |
Scooby Guru
Member#: 7492
Join Date: Jun 2001
Chapter/Region:
South East
Location: Hotlanta, GA
Vehicle:No race cars www.tomhoppe.com |
Add a jackstand sticker to car A next to the rallydecals.com and its a no brainer.
-Tom who won on thinner but shorter tires before because of gearing |
12-08-2008, 12:40 PM | #11 |
Scooby Guru
Member#: 70252
Join Date: Sep 2004
Vehicle:05 STI blue |
Yea, i think theres alot of other factors as well.. the track being a huge one.. but i'd go for more meat on the tires winning.
|
12-08-2008, 01:12 PM | #12 |
Scooby Guru
Member#: 442
Join Date: Oct 1999
Chapter/Region:
NESIC
Location: RI/SE Mass
Vehicle:17 Imp Spurt 00 S2k |
|
12-08-2008, 02:02 PM | #13 |
Scooby Guru
Member#: 37359
Join Date: May 2003
Vehicle:2003 WRX |
As I said, there are two many unknowns. The OP doesn't even say what car or what mods. Just that they are equal.
Imagine two versions of this test being run, one with stock Miatas and another with modified Z06s. Will a Z06 accelerate faster on 215s? Even if you assume it's a Suby, the differences between a stock NA Impreza and a 500whp STi will change the equation. Given enough power, the 215s can't get the power down to take advantage of the gearing and weight reduction. |
12-08-2008, 02:52 PM | #14 | |
Scooby Guru
Member#: 133146
Join Date: Nov 2006
Location: SC
Vehicle:07 FPgreen 7.37@95 WRX VF39+E85 12.0, 121mph |
Quote:
Power mods: vf39, sti TMIC, gimmick turbo inlet, APS CAI, Perrin EL and Uppipe, TGV deletes, Phenolic spacer, Buschur Racing catless TBE, 860cc injectors, and a E85 tune that is not finallized . Suspension mods: megan racing street coilovers, cobb adjustable swaybars and kartboy endlinks. The car should weight about 2890-2910 with the heavy wheels and tires without me, I weight 150 lbs. Also, it has a stock 07 WRX tranny. |
|
12-08-2008, 02:58 PM | #15 | |
Scooby Specialist
Member#: 122980
Join Date: Aug 2006
Chapter/Region:
South East
Location: Raleigh, NC
Vehicle:2010 F150, 2013 CX-5 92 Miata 15 TTF/PTF/E3 |
Quote:
|
|
12-08-2008, 03:48 PM | #16 |
Scooby Specialist
Member#: 63292
Join Date: Jun 2004
Chapter/Region:
South East
Location: Warner Robins, GA
Vehicle:2000 Subaru 2.5RS 2002 WRX powered |
also, how good of a driver are you? That would make a big difference between the two. Are you good enough to be able to fully utilize the extra tire? I'm really only asking in terms of road racing.
However, based on what you've given me, and assuming you are an average, but not great, driver. I would guess the thinner tires would win in autocross and drag, while the wide tires would win at road racing. Hopefully, Im right. Because that was pretty much the basis I used to make my decision on wheels/tires for my soon-to-be-road racing RS. |
12-08-2008, 08:05 PM | #17 |
Scooby Newbie
Member#: 87190
Join Date: May 2005
|
Small differences in alignment, shock valving, and tire age could make a difference. The devil is the details.
With that said, it should be close, but one car will be better than the other depending on venue. One has less rotational mass and shorter gearing while the other has wider rubber - Course dependent. |
12-08-2008, 08:27 PM | #18 | |
Scooby Guru
Member#: 70252
Join Date: Sep 2004
Vehicle:05 STI blue |
Quote:
also short gearing doesnt nec.. equal faster track time.. depending on different sections of a track, the car with the taller gearing could be faster then that with the short since no time will be lost for a shift. |
|
12-08-2008, 10:06 PM | #19 |
Scooby Guru
Member#: 86356
Join Date: May 2005
Chapter/Region:
Tri-State
Vehicle:2018 Aprilia Tuono v4 1100 |
For that year WRX on most SCCA courses I'd want a short tire, but 215 is too skinny. Why are you limiting yourself to those two choices?
|
12-08-2008, 10:16 PM | #20 |
Scooby Specialist
Member#: 70011
Join Date: Sep 2004
Chapter/Region:
NESIC
Location: Bozeman, MT
|
17 pounds per wheel of unsprung weight is a lot..
I'd say the longer one is better for autocross I lot depends on how much power the car has. |
12-08-2008, 10:47 PM | #21 |
Scooby Newbie
Member#: 188792
Join Date: Sep 2008
Chapter/Region:
SCIC
Location: Huntington Beach
Vehicle:2007 STI CGM |
I would say for road racing, car A would be faster despite being heavier. Thats why in, say time attack, I would want the widest tire that would suit my needs. 215 or 245, it seems like a no brainer.
For drag, I would say if the car doesnt spin the tires, car B would be faster, just because of the lighter weight and less rotating mass. Autocross??? |
12-08-2008, 10:45 PM | #22 | |
Scooby Specialist
Member#: 48377
Join Date: Nov 2003
Chapter/Region:
MWSOC
Location: "They eat fish soaked in lye"
Vehicle:1996 Gutted, built XP class Impreza L |
Quote:
Car C wins hands down. |
|
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
Ford’s global mid-size car will be built on the Mondeo platform, will replace Fusion | AVANTI R5 | Non-Subaru News & Rumors | 8 | 03-23-2009 09:08 PM |
so which Ot'er will be the first to kill me for posting this | pjhe | Off-Topic | 6 | 05-16-2008 10:17 AM |
Which Japanese Cars Will Be 'Classics'? | Tragedy | Off-Topic | 100 | 04-12-2008 02:15 AM |
Seems like my car should be faster? | jersey1320guy | Factory 2.0L Turbo Powertrain (EJ Series Factory 2.0L Turbo) | 33 | 09-07-2007 04:36 PM |
My car will be in a car show! | HRE | giulio | Tri-State Area Forum | 5 | 05-23-2001 01:26 PM |