Mine currently as I sit at dinner.
2024 Land Cruiser "250 series"
- Thread starter Hulk
- Start date
OK, proof mine saw dirt on its first day.
now armor it up with some Dissent bumpers and 38" tires and go to the rubicon!OK, proof mine saw dirt on its first day.
Congrats on the new ride!
View: https://www.instagram.com/p/C-gOJClyLp-/
Cruisertrash
Rising Sun Member
OK, proof mine saw dirt on its first day.
WARRANTY VOIDED!!!
I’m going to say that a 34” tire does not fit. If you let some air out I’m sure it would. This is a worn 315/75r16 from my 80. Measured just over 34” with a level. It took a floor jack under it to get her in that far. The tire is not completely up to the frame in the rear but is contacting the forward spare tire brackets. I nearly lifted the whole truck off the ground in an attempt to raise it more. It’s also contacting the trailer wiring bracket. I’m going to say that 275/70r18 is the max spare tire without modification.
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Rzeppa
Rising Sun Member
I was thinking that is going to be the deciding factor in what size tires I can go to without adding a swingout. You just proved it. I like to do a 5 tire rotation. At least they put the same nice alloy wheel on the spare instead of some cheap stamped steel unit.
There are reports out there of 285/70r18 fitting under the truck. I’m going to say it comes down to which tire manufacture you go with as that size is +/-34”. But yah I’m not going to exceed my OEM spare location’s size ceiling for tires either.
Today’s exercise proved I need to order 18” wheels for the summer tires. I’m mounting dedicated winter tires on the OEM wheels.
Today’s exercise proved I need to order 18” wheels for the summer tires. I’m mounting dedicated winter tires on the OEM wheels.
Rzeppa
Rising Sun Member
That's what I do for both of my wife's cars, used to be Blizzaks, now running Nokians in the winter and then generic all seasons from May through October.
On my 250 I think I'm going to back to the Duratracs that I liked so much when I had a set on my 60. I wonder if having anything other than stock diameter will have any adverse affect on the software, and also wonder if there is some kind of software calibration setting to compensate for road speed, like when you could put different teeth gears in the speedo cable mechanism behind the x-fer case.
Icon did a pretty good tire fitment and wheel offset video. Cliff notes: 275/70r18 or 285/65r18 are the largest recommended size for spare tire fitment. 35x12.5" fits with minimal trimming. +40mm offset is the recommended wheel. Enjoy.
View: https://youtu.be/LS94Q7qbVec?feature=shared
View: https://youtu.be/LS94Q7qbVec?feature=shared
Rzeppa
Rising Sun Member
I'm not as concerned with fitment per se, but wheel speed calibration and how larger tire sizes affect the software. I guess the service department at one of our local dealers might have an answer. Too bad BVB is retired, I bet he'd know.
I have observed that when I drive past a radar speed display, the speed displayed on the dash is invariably greater than what the radar says, typically by a couple MPH. I'd speculate that the stock 31.5" tires might be slightly undersized for what the software expects.
I have observed that when I drive past a radar speed display, the speed displayed on the dash is invariably greater than what the radar says, typically by a couple MPH. I'd speculate that the stock 31.5" tires might be slightly undersized for what the software expects.
ScaldedDog
Hard Core 4+
Rzeppa
Rising Sun Member
Every Land Cruiser I've driven with larger than stock tires behaves opposite - the indicated speed on the dash is lower than that indicated by the radar display. For 33s on a 40 or a 60, it is around 13% under. On my 45 it is pretty close. I measured the stock 7.5 x 15 bias ply tires that came with it at 32", so that's likely the way they geared the speedo drive behind the t-case. But the 250 is so much software, it's gotta just be some value in the config file.
Only reason your speed would be slower in real life than what your dash shows, with larger tires, is if you regeared your axles. Otherwise, everything else being equal, a larger tire will go a further distance per revolution than a smaller tire, so your real world speed will be higher.
Jeff, I’d assume your 1958 is actually calibrated for the larger 265/70r18 stock tire size. Mine is reading about 1mph fast compared to the radar speed signs at speeds around 50. I expect to be dead on with those after moving up to 275. Look at it this way. The larger the tire them more distance traveled with less record on the odometer. Larger tires actually extend your trucks warranty.
Rzeppa
Rising Sun Member
Um, I understand the geometry and physics and the relationship between gearing, tire size and indicated speed. My question is, how will changing tire sizes affect the 250's software and how that affects the rest of the vehicle's behavior (example ECT, electric vs ICE activation, etc.). On my old school rigs, it is just a simple arithmetic ratio between stock (235/75R15 ~ 29") vs. what I put on, 33", so 13.7%, validated by odo testing on a large (100 mile) sample size. Whenever I go to Cruise Moab, I record the odo reading at mile marker 100 just west of Glenwood and then again at the Utah state line. Simple math. On the 250, there's a buttload of software that wants to know the actual speed and I'd like to know how going to a bigger tire will affect that software's behavior.
Rzeppa
Rising Sun Member
Yeah I am kinda surprised that the software seems to be off on the 245/70R18s they put on mine at the factory. You'd think there is a variable that they could update for that, and that's kind of what I'd like to know - how easy or hard is it to change that value. Based on my observation of displayed speed versus radar speed mine appears to be off by around ~10% - the problem is that I am rolling through radars on low speed areas such as Morrison's 25 MPH so there isn't much resolution. If it were 60 or something it would give a more granular answer. What it is looking like is that they put a one-size-fits-all number into that variable instead of customizing it for the tires they're putting on at the factory.
Obviously under counting miles with larger diameter tires extends the warranty, but I'd be happier if the calibration were accurate. But if I go to 270 or 275/70R18 and that makes it accurate and also fits underneath for the spare, then win-win!
DaveInDenver
Rising Sun Ham Guru
The regulations in many places around the globe require that a speedometer have no more than 10% error plus some discrepancy and the absolute error must always be over estimated. So a speedo in Europe or Asia will never come from the factory reading lower than your actual speed but could be as much as 10% plus 4 to 10 km/hr high.
The SAE has a spec for it but it's not in the FMVSS for passenger vehicle. Commercial trucks in the U.S., though, have to correct +/- 5 MPH at 50 MPH (e.g. 10%) but AFAIK it's a simple tolerance not accurate but do not exceed situation.
The most obvious I found was my 2022 Suzuki DRZ400 is very optimistic. At indicated 60 MPH I'm really only going about 54 MPH. Our 2017 Subaru Forest reads just slightly high, about 1 to 2 MPH at 65 MPH. Didn't notice much error in my 2008 Tacoma. Perhaps relevant is that the DRZ and Forester are both made in Japan and the motorcycle is probably basically the same bike globally. The Forester was surely U.S. spec but a global design (maybe the most similar to a 250 series). My Tacoma is US-made and basically a North America only design so no reason it would need to adhere to JDM, Aussie or Euro rules.
BTW, don't trust GPS speed as a reference. GPS speed is estimated and very much a function of the Doppler correction done in the receiver. More modern techniques using carrier phase shift are extremely accurate but that's RTK and survey quality, not consumer level chipset stuff and these super accurate ways are highly influenced by signal quality (think big roof antennas on your equipment). So it's entirely possible what your phone says could be a couple of MPH wrong, too. Average speed over a straight road with a good sky view is best but check it against mile markers and your watch. That's actually the most likely to be right. Even CDOT gets mile markers pretty close to properly spaced. Even if the marker is 50 feet off and you're only within +/- 1 second of exact your total error is about 2% to 3% that way.
And, yes, I actually do check speed using mile markers and a a stopwatch. Dorkus Maximus. Although on the bike I have to try for one mile per minute to prevent dying in a fiery wreck.
The SAE has a spec for it but it's not in the FMVSS for passenger vehicle. Commercial trucks in the U.S., though, have to correct +/- 5 MPH at 50 MPH (e.g. 10%) but AFAIK it's a simple tolerance not accurate but do not exceed situation.
The most obvious I found was my 2022 Suzuki DRZ400 is very optimistic. At indicated 60 MPH I'm really only going about 54 MPH. Our 2017 Subaru Forest reads just slightly high, about 1 to 2 MPH at 65 MPH. Didn't notice much error in my 2008 Tacoma. Perhaps relevant is that the DRZ and Forester are both made in Japan and the motorcycle is probably basically the same bike globally. The Forester was surely U.S. spec but a global design (maybe the most similar to a 250 series). My Tacoma is US-made and basically a North America only design so no reason it would need to adhere to JDM, Aussie or Euro rules.
BTW, don't trust GPS speed as a reference. GPS speed is estimated and very much a function of the Doppler correction done in the receiver. More modern techniques using carrier phase shift are extremely accurate but that's RTK and survey quality, not consumer level chipset stuff and these super accurate ways are highly influenced by signal quality (think big roof antennas on your equipment). So it's entirely possible what your phone says could be a couple of MPH wrong, too. Average speed over a straight road with a good sky view is best but check it against mile markers and your watch. That's actually the most likely to be right. Even CDOT gets mile markers pretty close to properly spaced. Even if the marker is 50 feet off and you're only within +/- 1 second of exact your total error is about 2% to 3% that way.
And, yes, I actually do check speed using mile markers and a a stopwatch. Dorkus Maximus. Although on the bike I have to try for one mile per minute to prevent dying in a fiery wreck.
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Measuring for Alaskan ferries this morning. Just over 31’
