That said, the speedo is slightly optimistic (you travel slightly slower than the speed indicated on your speedometer). The amount varies from car to car.
The net result of running the larger tyres is around 1.03 faster than indicated. So, if the speedo indicates 100kph, you're actually travelling at 103kph.
Being an electrical signal (pulse) in '93 - '98 models to the speedo there are products which can be fitted to correct the pulse rate.
You do need to confirm the legal implications of fitting larger tyres. Particularly your state's registration and insurance requirements as well as checking that it does not affect your Toyota warranty.
The 285/75 tyre is a common upgrade to 80 and 100 Series Cruisers and one which significantly enhances the off highway capabilities of the vehicle.
It will adversely affect the economy, rate of acceleration and possibly noise on the highway, but it's a small price to pay for the off highway benefits.
Cheers
gc
'97 HDJ80 - Melbourne Oz
Almost everyone's tire requirements (and priorities) are different. I started with the Michelin LT's in the dealer's lot, tried to negotiate something different because I knew I didn't want those "slicks" for the rock crawling, mud, etc. that AZ would throw at me. I also wanted to step up a size or two (if I could). The dealer would have none of the new tire swap stuff so I bought the vehicle with the Michelin's. I also immediately tried to swap them out for BFG's or ??? Due to the rareness of the tire size (285/75/R16's) at that time, there were no tires of that size in the city. I did manage to arrange a swap but it would be a week before they would get the tires in. What to do...
With the Michelin's, I went up into the White Mountains east of Phoenix on some gravel roads and ended up with a sidewall blowout (this was not a 4WDR outing- passenger cars were on this gravel road!). When I got back I found that another one had been damaged enough to make it risky (maybe I ran over something sharp??). I then swapped out the remaining 3 "good" tires with Bridgestone Mud Duelers (285/75/R16's). They looked good, were somewhat noisy and they were the size I wanted. After three sidewall (2 ply) failures (in about 18 months), I was ready for a change. Performance was OK but the flats were annoying, and at times outright dangerous.
I then slowly (2 at a time), under the hazard warranty replacement, replaced them with BFG MT 285/75/R16's. I now have a complete set on, no flats, some lug damage but excellent performance. Yes, they are noisy but that is what windows are for. Off highway, I can roll the windows down (OK, push the button) and never hear them due to the slow speed. The 3 ply sidewall is what is needed for the rocky trails I run in AZ. I would certainly purchase another set. I have just over 30 k miles on the vehicle.
Although I didn't mention it, you have probably guessed that I am hard on tires. The BFG MT's (with road hazard warranty) are the only tire for me, given my driving and the terrain I try to traverse. On my earlier vehicle ('91 FJ-80), I tried the BFG AT's and they are quieter but seem to not have a rubber compound as tough as the MT's. That was 4 years ago-things change. I do have the Downey 2.5" lift kit on the current vehicle and have never scraped the over-size tires on anything, despite trying my darndest.
For informational purposes, on the '91/'92 FJ-80's, you can step up to the 32/11.50's without any problems in tires scraping anything-I ran them for about 18 months of hard 4 wheeling. If you go to the 33/12.50's (with the proper offset/rim), you may also be OK if you don't do anything wild from a 4 wheeling standpoint. They come close to scraping when tucking a wheel tight up into the body at full extension but a lift is not required unless you really press and/or launch the vehicle. I stayed with the 32's.
Joe Chott
'93 FZJ-80