UBC Auto-X July 26th

lol...

Na like I was telling Brian when he started this whole racing bug, smaller is better.   The smaller the outside diameter of the wheel, and the shorter the overall tire/wheel combo the quicker the car will accelerate due to the effective gear ratio change.   Going from say a 26" tall tire and wheel package down to a 23" tale tire and wheel package, the difference is amazing.  Acceleration is much faster coming out of a corner, braking is increased drastically, the only draw back is reduced top speed, however if you are never red-line at top gear, the point is null.      We really need to set up Lisa's old tires on a car, say a set of full size 17s or 18s and let people try the difference.  

These sizes will both fit on a stock or lowered Fiero.

Note the overall size is a whopping 4 inches difference, which would result in a 2" drop to your car going from one size to the other, or a 2" lift if you started with the smaller size and moved to the larger size.

Just a side note, on a Fiero that is dropped 2" the max you can go is a 26.88" tall rear tire.  Unless you have some serious back space on the wheels. 

     Also note that you know have a 15% change in gearing, which is a substantial change.   Go to the website and play with sizing.   I think we found one day, that you can go with a 22" wheel on a Fiero and with a low enough profile tire, not even make the speedo change.

 

This program has been used approximately times.



DML Tire and Wheel Calculator Results

 

Dimensions

Dimension Tire A: 205/40 R 16 (22 x 8.07 x 16) Tire B: 225/60 R 16 (27 x 8.86 x 16) Difference Width Sidewall height Overall height Circumference 8.07" (205.00mm) 3.23" (82.00mm) 22.46" (570.40mm) 70.55" (1791.96mm) 8.86" (225.00mm) 5.31" (135.00mm) 26.63" (676.40mm) 83.66" (2124.97mm) +0.79" (+20.00mm) +2.09" (+53.00mm) +4.17" (+106.00mm) +13.11" (+333.01mm)

 

Speedometer Error

Actual Speed	Indicated Speed with Tire B	Speedometer Error
5 mph (8.04 kph)	4.22 mph (6.78 kph)	-0.78 mph (-1.26 kph)
10 mph (16.09 kph)	8.43 mph (13.57 kph)	-1.57 mph (-2.52 kph)
15 mph (24.13 kph)	12.65 mph (20.35 kph)	-2.35 mph (-3.78 kph)
20 mph (32.18 kph)	16.87 mph (27.14 kph)	-3.13 mph (-5.04 kph)
25 mph (40.23 kph)	21.08 mph (33.92 kph)	-3.92 mph (-6.30 kph)
30 mph (48.27 kph)	25.30 mph (40.71 kph)	-4.70 mph (-7.56 kph)
35 mph (56.31 kph)	29.52 mph (47.49 kph)	-5.48 mph (-8.83 kph)
40 mph (64.36 kph)	33.73 mph (54.27 kph)	-6.27 mph (-10.09 kph)
45 mph (72.41 kph)	37.95 mph (61.06 kph)	-7.05 mph (-11.35 kph)
50 mph (80.45 kph)	42.16 mph (67.84 kph)	-7.84 mph (-12.61 kph)
55 mph (88.50 kph)	46.38 mph (74.63 kph)	-8.62 mph (-13.87 kph)
60 mph (96.54 kph)	50.60 mph (81.41 kph)	-9.40 mph (-15.13 kph)
65 mph (104.58 kph)	54.81 mph (88.20 kph)	-10.19 mph (-16.39 kph)
70 mph (112.63 kph)	59.03 mph (94.98 kph)	-10.97 mph (-17.65 kph)
75 mph (120.67 kph)	63.25 mph (101.76 kph)	-11.75 mph (-18.91 kph)
80 mph (128.72 kph)	67.46 mph (108.55 kph)	-12.54 mph (-20.17 kph)
85 mph (136.76 kph)	71.68 mph (115.33 kph)	-13.32 mph (-21.43 kph)
90 mph (144.81 kph)	75.90 mph (122.12 kph)	-14.10 mph (-22.69 kph)
95 mph (152.85 kph)	80.11 mph (128.90 kph)	-14.89 mph (-23.95 kph)
100 mph (160.90 kph)	84.33 mph (135.69 kph)	-15.67 mph (-25.21 kph)
105 mph (168.94 kph)	88.55 mph (142.47 kph)	-16.45 mph (-26.48 kph)
110 mph (176.99 kph)	92.76 mph (149.25 kph)	-17.24 mph (-27.74 kph)
115 mph (185.03 kph)	96.98 mph (156.04 kph)	-18.02 mph (-29.00 kph)
120 mph (193.08 kph)	101.19 mph (162.82 kph)	-18.81 mph (-30.26 kph)
125 mph (201.12 kph)	105.41 mph (169.61 kph)	-19.59 mph (-31.52 kph)
130 mph (209.17 kph)	109.63 mph (176.39 kph)	-20.37 mph (-32.78 kph)
135 mph (217.22 kph)	113.84 mph (183.17 kph)	-21.16 mph (-34.04 kph)
140 mph (225.26 kph)	118.06 mph (189.96 kph)	-21.94 mph (-35.30 kph)
145 mph (233.31 kph)	122.28 mph (196.74 kph)	-22.72 mph (-36.56 kph)
150 mph (241.35 kph)	126.49 mph (203.53 kph)	-23.51 mph (-37.82 kph)
155 mph (249.40 kph)	130.71 mph (210.31 kph)	-24.29 mph (-39.08 kph)
160 mph (257.44 kph)	134.93 mph (217.10 kph)	-25.07 mph (-40.34 kph)
165 mph (265.49 kph)	139.14 mph (223.88 kph)	-25.86 mph (-41.60 kph)
170 mph (273.53 kph)	143.36 mph (230.66 kph)	-26.64 mph (-42.87 kph)
175 mph (281.57 kph)	147.58 mph (237.45 kph)	-27.42 mph (-44.13 kph)
180 mph (289.62 kph)	151.79 mph (244.23 kph)	-28.21 mph (-45.39 kph)
185 mph (297.67 kph)	156.01 mph (251.02 kph)	-28.99 mph (-46.65 kph)
190 mph (305.71 kph)	160.22 mph (257.80 kph)	-29.78 mph (-47.91 kph)
195 mph (313.75 kph)	164.44 mph (264.59 kph)	-30.56 mph (-49.17 kph)
200 mph (321.80 kph)	168.66 mph (271.37 kph)	-31.34 mph (-50.43 kph)

If your speedometer has been calibrated for 205/40 R 16 (22 x 8.07 x 16) tires, replacing them with 225/60 R 16's (23 x 8.86 x 16's) would result in the speedometer reading low by 15.67%.

 

Odometer Error

Actual Mileage	Indicated Mileage with Tire B	Odometer Error
1 mi (1.61 km)	0.84 mi (1.36 km)	-0.16 mi (-0.25 km)
5 mi (8.04 km)	4.22 mi (6.78 km)	-0.78 mi (-1.26 km)
10 mi (16.09 km)	8.43 mi (13.57 km)	-1.57 mi (-2.52 km)
50 mi (80.45 km)	42.16 mi (67.84 km)	-7.84 mi (-12.61 km)
100 mi (160.90 km)	84.33 mi (135.69 km)	-15.67 mi (-25.21 km)
500 mi (804.50 km)	421.64 mi (678.43 km)	-78.36 mi (-126.07 km)
1000 mi (1609.00 km)	843.29 mi (1356.85 km)	-156.71 mi (-252.15 km)
5000 mi (8045.00 km)	4216.44 mi (6784.25 km)	-783.56 mi (-1260.75 km)
10000 mi (16090.00 km)	8432.88 mi (13568.50 km)	-1567.12 mi (-2521.50 km)
50000 mi (80450.00 km)	42164.40 mi (67842.52 km)	-7835.60 mi (-12607.48 km)
100000 mi (160900.00 km)	84328.80 mi (135685.03 km)	-15671.20 mi (-25214.97 km)

Same as with the speedometer, if your odometer has been calibrated for 205/40 R 16 (22 x 8.07 x 16) tires, replacing them with 225/60 R 16's (27 x 8.86 x 16's) would result in the odometer reading low by 15.67%.

 

Effective Gear Ratio Change

Rearend ratio with 205/40 R 16's	Rearend ratio with 225/60 R 16's
3.55	2.99

As far as gearing goes, if you have a 3.55 rearend and 205/40 R 16 tires (22 x 8.07 x 16), changing to 225/60 R 16's (27 x 8.86 x 16's) would be the same as if you kept your current wheels and tires but changed your rearend gears to 2.99's

 

RPM Change

RPM with 205/40 R 16's	RPM with 225/60 R 16's
6000	5059

Replacing your 205/40 R 16 (22 x 8.07 x 16) tires with 225/60 R 16's (27 x 8.86 x 16's) would lower your finish line RPM by 941 RPMs.

 

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Capt Fiero wrote: 20 series profile

Ugh, no thanks, not for street use anyway. I think you'd feel every pebble on the road with such low profile tires. I don't even like the 50 series tires I have on my GT. Next tires will be 60's.

I'm old school. I like to see some meat on my wheels, not thin little rubber bands.

 

Patrick wrote: Capt Fiero wrote: 20 series profile Ugh, no thanks, not for street use anyway. I think you'd feel every pebble on the road with such low profile tires. I don't even like the 50 series tires I have on my GT. Next tires will be 60's. I'm old school. I like to see some meat on my wheels, not thin little rubber bands.

Ah, I grew up looking at Formula technology. You thin out the sidewalls and during cornering your car will tend not to "lean over" it's point of contact. As your aware, if you can keep your point of contact and point of load in parralel, you gain a significant amount of cornering ability, which is why manufacturers spend so long designing their steering knuckles and suspension (Due to SAI, Included Angle, Caster and Scrub Radius). David does have a legitamite point, but then again, it wouldn't be all good for example. A closer range transmission means more shifts, and in a racing type like autocross, that could get quite tiresome (This is overlooking the power loss during each shift). And Patrick, the style you like is good for drag racing, as it allows the car to spin the axles and inside portion of the tire slightly, before the outside finally tries to catch up and snaps forward like a rubber band, giving a touch more grunt to the sixty foot mark.

Romeo wrote: And Patrick, the style you like is good for drag racing, as it allows the car to spin the axles and inside portion of the tire slightly, before the outside finally tries to catch up and snaps forward like a rubber band, giving a touch more grunt to the sixty foot mark.

Sounds like you're describing "wrinkle slicks".

 

Romeo sorry to burst your tire here, but in the grander scheme of things, and the reason no one runs much bigger than a 10" slick on a Fiero is, nothing else in a Fiero can handle that much traction.  Long before you break traction on a 10 slick in a Fiero, you'll shatter CV shafts, blow up even the most radical of trans axles, motor mounts would be turned into pretzels faster than you can think.   I use to run a 9.64 inch rear street tire (not a even a drag tire) on my back of my V8 car and I actually dropped it back to an 8.8" street tire because I got tired of breaking parts.  Its much cheaper to replace burnt tires than blown clutches or trans axles.   I still kill mounts, but not nearly as bad.     With the big tires, I could litterly at will, put new mounts in the car, take it out, rev the clutch dump it hard, and pull it back into the driveway to replace my now destroyed mounts.