Got my 235 / 85's mounted!

[Matt Bachand]

Mileage update. First true highway runs I had with some mixed city driving yielded a tad under 15mpg. Down a bit from 16. Still too early to tell for sure. The last 45 miles of that run my Alternator was out, and when i replaced it, the bearings must have been close to siezing judging by the hand spin noises.

I just recalibrated my VSSB to proper speedo readings, so now my TCC will in effect lock up 5 mph earlier than this reading. I'm going to clean my air cleaner up tomorrow, and I'll keep posted if any change on my mileage.

 

[Detroit Dan]

I've never changed my vssb, so I have no idea what my mileage really is. With stock tires (225/75) I got 13.75 all the time. I went to 235/85 then eventually 255/85, I'd love to know what I really get for mileage, but since I really don't know how far I'm travelling I can't seem to calculate it. For my usual driving, 40-50 mph it seems to be more in it's comfort zone. It still doesn't like the highway, even though I've lowered the cruising rpms. It wants to cruise at 60, maybe 65 but anything faster and it's working just enough that it burns through fuel like mad. And it won't do over an estimated 75-80 now, it just runs out of power and kicks in and out of 3rd. I also get some bucking like fuel delivery if I keep my foot in it. I have changed my speed sensors. My speedo is way off, and sometimes I notice it stays at 50 even when I change speed from about 55 to 70 on the highway. And sometimes it works (although it's still reading too slow).

Stock, with little tires I could get 95 out of it.

 

[Matt Bachand]

I've never changed my vssb, so I have no idea what my mileage really is. With stock tires (225/75) I got 13.75 all the time. I went to 235/85 then eventually 255/85, I'd love to know what I really get for mileage, but since I really don't know how far I'm travelling I can't seem to calculate it. For my usual driving, 40-50 mph it seems to be more in it's comfort zone. It still doesn't like the highway, even though I've lowered the cruising rpms. It wants to cruise at 60, maybe 65 but anything faster and it's working just enough that it burns through fuel like mad. And it won't do over an estimated 75-80 now, it just runs out of power and kicks in and out of 3rd. I also get some bucking like fuel delivery if I keep my foot in it. I have changed my speed sensors. My speedo is way off, and sometimes I notice it stays at 50 even when I change speed from about 55 to 70 on the highway. And sometimes it works (although it's still reading too slow).

Stock, with little tires I could get 95 out of it.

Actual Speed Indicated Speed with Tire B Speedometer Error
5 mph (8.04 kph) 4.43 mph (7.13 kph) -0.57 mph (-0.92 kph)
10 mph (16.09 kph) 8.86 mph (14.25 kph) -1.14 mph (-1.84 kph)
15 mph (24.13 kph) 13.29 mph (21.38 kph) -1.71 mph (-2.76 kph)
20 mph (32.18 kph) 17.71 mph (28.50 kph) -2.29 mph (-3.68 kph)
25 mph (40.23 kph) 22.14 mph (35.63 kph) -2.86 mph (-4.60 kph)
30 mph (48.27 kph) 26.57 mph (42.75 kph) -3.43 mph (-5.52 kph)
35 mph (56.31 kph) 31.00 mph (49.88 kph) -4.00 mph (-6.44 kph)
40 mph (64.36 kph) 35.43 mph (57.00 kph) -4.57 mph (-7.36 kph)
45 mph (72.41 kph) 39.86 mph (64.13 kph) -5.14 mph (-8.28 kph)
50 mph (80.45 kph) 44.29 mph (71.25 kph) -5.71 mph (-9.20 kph)
55 mph (88.50 kph) 48.71 mph (78.38 kph) -6.29 mph (-10.11 kph)
60 mph (96.54 kph) 53.14 mph (85.51 kph) -6.86 mph (-11.03 kph)
65 mph (104.58 kph) 57.57 mph (92.63 kph) -7.43 mph (-11.95 kph)
70 mph (112.63 kph) 62.00 mph (99.76 kph) -8.00 mph (-12.87 kph)
75 mph (120.67 kph) 66.43 mph (106.88 kph) -8.57 mph (-13.79 kph)
80 mph (128.72 kph) 70.86 mph (114.01 kph) -9.14 mph (-14.71 kph)
85 mph (136.76 kph) 75.28 mph (121.13 kph) -9.72 mph (-15.63 kph)
90 mph (144.81 kph) 79.71 mph (128.26 kph) -10.29 mph (-16.55 kph)
95 mph (152.85 kph) 84.14 mph (135.38 kph) -10.86 mph (-17.47 kph)
100 mph (160.90 kph) 88.57 mph (142.51 kph) -11.43 mph (-18.39 kph)
105 mph (168.94 kph) 93.00 mph (149.63 kph) -12.00 mph (-19.31 kph)
110 mph (176.99 kph) 97.43 mph (156.76 kph) -12.57 mph (-20.23 kph)
115 mph (185.03 kph) 101.86 mph (163.89 kph) -13.14 mph (-21.15 kph)
120 mph (193.08 kph) 106.28 mph (171.01 kph) -13.72 mph (-22.07 kph)
125 mph (201.12 kph) 110.71 mph (178.14 kph) -14.29 mph (-22.99 kph)
130 mph (209.17 kph) 115.14 mph (185.26 kph) -14.86 mph (-23.91 kph)
135 mph (217.22 kph) 119.57 mph (192.39 kph) -15.43 mph (-24.83 kph)
140 mph (225.26 kph) 124.00 mph (199.51 kph) -16.00 mph (-25.75 kph)
145 mph (233.31 kph) 128.43 mph (206.64 kph) -16.57 mph (-26.67 kph)
150 mph (241.35 kph) 132.86 mph (213.76 kph) -17.14 mph (-27.59 kph)
155 mph (249.40 kph) 137.28 mph (220.89 kph) -17.72 mph (-28.51 kph)
160 mph (257.44 kph) 141.71 mph (228.01 kph) -18.29 mph (-29.43 kph)
165 mph (265.49 kph) 146.14 mph (235.14 kph) -18.86 mph (-30.34 kph)
170 mph (273.53 kph) 150.57 mph (242.27 kph) -19.43 mph (-31.26 kph)
175 mph (281.57 kph) 155.00 mph (249.39 kph) -20.00 mph (-32.18 kph)
180 mph (289.62 kph) 159.43 mph (256.52 kph) -20.57 mph (-33.10 kph)
185 mph (297.67 kph) 163.85 mph (263.64 kph) -21.15 mph (-34.02 kph)
190 mph (305.71 kph) 168.28 mph (270.77 kph) -21.72 mph (-34.94 kph)
195 mph (313.75 kph) 172.71 mph (277.89 kph) -22.29 mph (-35.86 kph)
200 mph (321.80 kph) 177.14 mph (285.02 kph) -22.86 mph (-36.78 kph)




If your speedometer has been calibrated for 225/75 R 16 (29 x 8.86 x 16) tires, replacing them with 255/85 R 16's (31 x 10.04 x 16's) would result in the speedometer reading low by 11.43%.

70 mph (112.63 kph) 62.00 mph (99.76 kph) -8.00 mph (-12.87 kph)

When your speedo reads 62, you are really doing 70.

To figure out your actual mileage multiply your ODO by 1.1143 then devide my gallons used for MPG.

There ya go bud! BTW, changing the VSSB isn't all too tough, Find the circumference of the tire with a chalk line on the ground, then roll forward till it hits the ground again, and I'll punch in the math for the input shaft ratio and find which jumpers your VSSB should be set at while its fresh in my head.

 

[Detroit Dan]

ow, that much math hurts my head.
I will say this: all the talk about conversion to flotation sizes is flawed. There aren't likely any two tire manufacturers that make a 235/85/16 that's the same height or width. Someone elsewhere called a 235/85 a 33, and above you put the metric 255/85 at only 31, but the 225/75 at 29. My 235/85s were 31, they dwarfed the 225s, and are dwarfed by my 255s. My 255s are advertised as a 33" tire and I believe it, when they were new anyway. Plus, they are Intercos who is the most honest when it comes to flotation sizes.

 

[Matt Bachand]

Indeed my 285's are 31's. so your 255's must be 33's...

Every tire calc website has different base values also. Best you can do is get close i guess.

 

[buddy]

Theoretically, you should be able to calculate the height by the tire size.

For a 33" tire on a 16" rim that has 255mm width, that means the ratio of the wall heigt to the width of the tread needs to be 85%, which is the second number.

255/85R16 = 33.7" theoretically
235/85R16 = 32.3" theoretically

But manufacturers must be allowed a certain tolerance on that. Thats why in Matt's case, what worked was using the loaded height of the wheel on the truck. Which was like 30.2" tall x Pi = 94.88 circumference, which got him right on the money with the speedo.

 

[Matt Bachand]

Got an old camera up and running again.... She's in brand new shape from 2002, has a minidisk in it. LOL. here are some pix of the new skins 2 months late.

And an oldie for comparison.

 

[94K30]

looks good, Matt

 

[DEERE3594]

Looks great, just gotta get you raised white letters up front too! (also love the lights :thumbsup: )

 

[Matt Bachand]

Looks great, just gotta get you raised white letters up front too! (also love the lights :thumbsup: )

I really like the white lettering! I wish it the front 2 had em... Only paid 180bux for all 6, 4 are great tread, 2 have a year left on them.

The lights are nice, can't miss me at nighttime. When I got it it had nothing on the big body, so I went nuts... 5 down the side, and 3 up the headache rack. 2 bulbs in each lens, non led.

SO, result of this was frying through 2 headlight switchs, before wiring them up to a separate switch. (NEver got around to relay)... It turned into a wiring nightmare as everytime I had a failure was in the middle of the night while plowing, so needless to say its fix fast and go. Then forget about it until next failure.... No issue's last winter so maybe I got em The slush kicking up behind the rear wheels reeks HAVOC on everything and anything.

My truck will never look good, but I can sure as hell keep it from looking bad.

Slow down the rust on the utility body is all i can do. yearly paint and bondo.

 

[Detroit Dan]

Indeed my 285's are 31's. so your 255's must be 33's...

I thought you had 235/85s, not 285s?


Hey qwomack, what size wheels do you have?

 

[Matt Bachand]

I thought you had 235/85s, not 285s?


Hey qwomack, what size wheels do you have?

Indeed, 235's... typo...

 

[qwomack]

The wheels are stock size, whatever that is. I guess I need to get off my butt and provide some pics of my new shoes.

 

[Detroit Dan]

The wheels are stock size, whatever that is. I guess I need to get off my butt and provide some pics of my new shoes.

I can't believe you'e running 285s and 305s on 6 inch wide rims. I was told I shouldn't run 255s, but it was only a half inch narrower than what the book called for, so I figured I could live with it. But those sizes are wide, I saw 285s once on a dually and they looked way too wide for the rim, not to mention they had no spacers and were rubbing all the way around in the back.

Are you at all worried about uneven wear or worse, peeling them off the rim?

One last question, why a different size up front?

 

[buddy]

I think stock is 7" wide rims. Skinny still for 305s.

 

[Detroit Dan]

mine are 16x6 stock

 

[qwomack]

I can't believe you'e running 285s and 305s on 6 inch wide rims. I was told I shouldn't run 255s, but it was only a half inch narrower than what the book called for, so I figured I could live with it. But those sizes are wide, I saw 285s once on a dually and they looked way too wide for the rim, not to mention they had no spacers and were rubbing all the way around in the back.

Are you at all worried about uneven wear or worse, peeling them off the rim?

One last question, why a different size up front?

I agree that I am pushing the envelope running the size tire that I am, there are also several other people here, cbrew comes to mind, that are pushing it even further. He is actually running 315's all the way around. I figure if 315's are possible, 305's should definitely be do-able. I am running 2" spacers in the back to keep the sidewalls from rubbing. Believe it or not, the 285's look at home on the rims. As far as wear is concerned, I have about 1000 miles on them and everything looks good so far. The taller sidewall also lends to a more comfortable ride.

The reason for the wider tires up front is for the look I was after. I wanted a wider tire for the "low ground pressure" feature. Every time I have gone off-road, the front tires would sink and get me stuck. The wider foot print should help in that department. They are all the same diameter, btw, at 33".

 

[buddy]

My stock 15s were even 7" wide, those 16x6 would be perfect for 235/85s

 

[Detroit Dan]

Good looking truck, Quint. Just like mine, only your missing the dents and rust. Hoping to get mine restored back to that condition, been picking away at the bodywork, and experimenting with the Rustoleum/Tremclad method.

 

[qwomack]

Thanks, Dan. She's done me well through the years.