anybody have pics with 275 60 20's

[D Derr]

Going up 1” isn’t gonna do shit to the speedo. Maybe 0.5mph difference. I went to 35s and mine was off by maybe 2mph.

Oh, and going to 275/35's (4.3" shorter tire) would make a calculated difference of 13.6%! So, an indicated 70 would be an actual speed of 60.5 mph. THAT is a huge difference.

 

[Patsfan4lif]

Going from a 275/55-20 to a 275/60-20 will change the speedo by about 3.4%. So, if your speedo is correct with the 55 aspect ratio tires, after the change to 60's, 70 mph indicated would be 72.4. This is totally by calculation and different tires will vary a bit from the strict height calculations. But, it will be close to that; so a small difference.

Calculate going from a 275/55/20 to a 35/11.50/20 and tell me why my speedo was off by less than 2mph

 

[Patsfan4lif]

Oh, and going to 275/35's (4.3" shorter tire) would make a calculated difference of 13.6%! So, an indicated 70 would be an actual speed of 60.5 mph. THAT is a huge difference.

I got my results from gps, driving next to another exact expedition and seeing difference and on 3 different radar guns. I think your math is wrong sorry to burst your bubble. And if someone is really worried about 5mph then do what I did and get a speedo corrector.

 

[1955moose]

The speedo difference is no big deal, who really cares if your speed is dead on anyway. When you see a cop, your always on your best behavior anyway, and hoping to God, when you turn left, he turns right! I grew up in a time when speedos didn't work at all most of the time, and did like I did in my brother in law's Austin Healy3000, and take the Rpm and double it, 3,000 rpm equals 60mph. He kept that car for all the 60's, through 71, I think. Great car, I wish I had it myself today.

Sent from my N9131 using Tapatalk

 

[Vancouver Bob]

I was snooping around on the Custom Offset site. You can get a pretty good idea of different tire sizes, different offsets on the Expedition or whatever other car you might be interested in. The 275 60R20's are 33" tall, about 10.5"wide. Offset is going to make a big difference in appearance.

Here's a 2004 with a 3/2.5 lift(level), these are -25 offset so stick out a fair amount.

 

[Vancouver Bob]

 

[limitedex]

I had 275/60/20 on stock platinum/limited wheels. Obviously they were bigger and you could tell. Going from 31.9” to 32.99” is noticeable. I had Goodyear Duratracs too. I sold them to a friend after about 5,000 miles since I wanted something wider. Went back to 305/55/20 on Fuel Anza wheels.

 

[Patsfan4lif]

35/11.5s nimrod

 

[D Derr]

Calculate going from a 275/55/20 to a 35/11.50/20 and tell me why my speedo was off by less than 2mph

OK, thought you meant you went to 35 aspect ratio tires. Anyways, the difference between 275/55-20 (31.9" tall) and a 35" tall tire is almost 10%. So, if your speedo was dead on with the original tires, at an indicated 70 mph with the 35" tires, you would be going about 77 mph. Now, about being only 2 mph off, all things being equal and linear, you would be only 2 mph off at 20 mph. So, not sure how you calculated anything, but that is the cold hard math of the situation. Math is really quite simple; if you need help, let me know.

 

[LokiWolf]

I got my results from gps, driving next to another exact expedition and seeing difference and on 3 different radar guns. I think your math is wrong sorry to burst your bubble. And if someone is really worried about 5mph then do what I did and get a speedo corrector.

Did you measure stock? My guess would be no. So your scale is off most likely.

D’s math is dead on.

Our 2015 had 34’s. GPS calibrated stock it was off a fair amount(Don’t remember percentage exactly). Once lifted and with 34’s it was actually closer to accurate based on GPS. My guess is yours was off Stock, so therefore the effect your taller tires had was less.