285/70/17 or 285/75/17 (1 Viewer)

[TLC2013]

I'm not sure how good the data from this exercise will be, but for what it's worth here's what I get when I measure my LT285/70R17 E-Rated DT BFG KO2's mounted on Rock Warrior wheels on my 2013 LC200 inflated to 40psi:

Across the tire/wheel combo, i.e. at hub height the diameter of the tire from front to back = approx 32" at the outside edge of the tread and approx 32.5" at the center of the tread.

FWIW

HTH

I have Been searching for a thread or data base documenting the actual mounted tire height, and couldn’t find anything. Being the all knowing tire guru, Is there anything like this on the 200 forum? Would be a great resource for members to list their wheel size data, tire specifics and their unmounted and mounted measurements.

 

[gaijin]

I have Been searching for a thread or data base documenting the actual mounted tire height, and couldn’t find anything. Being the all knowing tire guru, Is there anything like this on the 200 forum? Would be a great resource for members to list their wheel size data, tire specifics and their unmounted and mounted measurements.

I think it would just cause a lot of confusion due to the lack of uniformity.

 

[Hugh Bris 1]

285/75r17 KO2 on Rock Warriors compared to 285/75r17 Ridge Grapplers on Evos. Both with 5,000 miles on them under a 200. Both inflated to 37 psi (per @gaijin... never question gaijin!)

Both are 32.63" tall when mounted on the recommended 8" rim, under the the same 200's weight according to one of Bud's lasers. When mounted on the rim, inflated to max pressure, but not under the weight of a truck, they do hit the 33.9" advertised height (where that number comes from).
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Below is the KO2.
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Below is the Ridge Grappler
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KO2s with Rock Warriors: 86 pounds
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Ridge Grapplers with Evos: 94 pounds (Evos are lighter than any of the Methods, Icons, or really whatever else is popular I've seen come through the shop)
View attachment 2197102

@gaijin For me this info is helpful to understand the diameter of the two tires, 285/75r17 vs. 285/70r17, at actual day-to-day "normal"cold tire inflation pressures. Thank you for all of the input on this and across the entire forum! Your input is obviously valuable. Feel free to correct me if I'm wrong. Both from this post by @Taco2Cruiser and on my own truck the 285/75r17 BFGKO2 on Rock Warriors measures right at 32.5" to maybe 32.625" at the peak and ~32.25" at the edge (the perspective in these photos makes the edge diameter difficult to be certain) at the recommended 37psi for these tires. In comparison to the 285/70r17 BFG KO2 on Rock Warriors and proper cold tire inflation (40psi) being about the same diameter at the center peak (32.5") and ~0.25" smaller at the edge (32") based on the data you provided. That's even comparing the data for the 285/70 being mounted on the truck to this data which is obviously not mounted on the truck.

So, it seems that at the recommended operating cold tire inflation, on Rock Warriors and mounted on the truck these two KO2's are very close to the same size.

If I'm reading these correctly, that's great! Am I missing some detail somewhere?

With this info, I'd say the decision for me is easy. It's not worth all of the hassle for such a small gain on tire size between these two sizes.

 

[gaijin]

@gaijin For me this info is helpful to understand the diameter of the two tires, 285/75r17 vs. 285/70r17, at actual day-to-day "normal"cold tire inflation pressures. Thank you for all of the input on this and across the entire forum! Your input is obviously valuable. Feel free to correct me if I'm wrong. Both from this post by @Taco2Cruiser and on my own truck the 285/75r17 BFGKO2 on Rock Warriors measures right at 32.5" to maybe 32.625" at the peak and ~32.25" at the edge (the perspective in these photos makes the edge diameter difficult to be certain) at the recommended 37psi for these tires. In comparison to the 285/70r17 BFG KO2 on Rock Warriors and proper cold tire inflation (40psi) being about the same diameter at the center peak (32.5") and ~0.25" smaller at the edge (32") based on the data you provided. That's even comparing the data for the 285/70 being mounted on the truck to this data which is obviously not mounted on the truck.

So, it seems that at the recommended operating cold tire inflation, on Rock Warriors and mounted on the truck these two KO2's are very close to the same size.

If I'm reading these correctly, that's great! Am I missing some detail somewhere?

With this info, I'd say the decision for me is easy. It's not worth all of the hassle for such a small gain on tire size between these two sizes.

I think we are getting confused because of a lack of uniformity in measurements.

My measurements were of the tire from front to back. I think your measurements are of height - i.e. top to bottom when mounted on the truck with the truck on the ground. Is this correct?

If so, then we are comparing apples to oranges.

I don't understand the importance of comparing top to bottom height measurements. Since these top to bottom measurements include the compressed area at the bottom of the tire (which reduces the overall height) then it is not a true indication of how much the rest of the tire would possibly interfere with body and/or suspension components.

Before I turn this into a TL;DR post, does this make sense so far?

 

[Hugh Bris 1]

I think we are getting confused because of a lack of uniformity in measurements.

My measurements were of the tire from front to back. I think your measurements are of height - i.e. top to bottom when mounted on the truck with the truck on the ground. Is this correct?

If so, then we are comparing apples to oranges.

I don't understand the importance of comparing top to bottom height measurements. Since these top to bottom measurements include the compressed area at the bottom of the tire (which reduces the overall height) then it is not a true indication of how much the rest of the tire would possibly interfere with body and/or suspension components.

Before I turn this into a TL;DR post, does this make sense so far?

Yes, I'm with you so far. I definitely understand how height measured mounted on the truck will be different (lower number) from the same tire mounted measured front to back.
Also yes, I had measured height on mine top to bottom. However, That is the same measurement from the post of the unmounted tire I mentioned in the last post. Which, now that I'm typing this I realize doesn't make sense. Why would the diameter I measured on the mounted tire, top to bottom, be the same as the unmounted tire?

 

[gaijin]

Which, now that I'm typing this I realize doesn't make sense. Why would the diameter I measured on the mounted tire, top to bottom, be the same as the unmounted tire?

Magic?

Seriously though, if all you're trying to determine is how much ground clearance you will lose by going from the LT285/75R17 KO2 to the LT285/70R17 KO2, then I would suggest a measurement from the ground to center of hub on a mounted tire on the vehicle under load. This measurement on my rig for the LT285/70R17 KO2's on RW wheels @40psi is 15.75".

Does that help?

 

[gaijin]

@Taco2Cruiser said:
285/75r17 KO2 on Rock Warriors compared to 285/75r17 Ridge Grapplers on Evos. Both with 5,000 miles on them under a 200. Both inflated to 37 psi (per @gaijin... never question gaijin!)

Both are 32.63" tall when mounted on the recommended 8" rim, under the the same 200's weight according to one of Bud's lasers.

You (@Hugh Bris 1) said:
Both from this post by @Taco2Cruiser and on my own truck the 285/75r17 BFGKO2 on Rock Warriors measures right at 32.5" to maybe 32.625" at the peak and ~32.25" at the edge (the perspective in these photos makes the edge diameter difficult to be certain) at the recommended 37psi for these tires.

Looks to me like you two agree on the total height when mounted on the truck under load.

 

[Hugh Bris 1]

Yep, that helps! Thank you! Checked pressure. It's right at 37psi. Looks like the measurement from ground to center of the hub is ~16.25" so the ground clearance difference would be about 0.5" between the 285/75r17 and 285/70r17 on Rock Warriors at "normal" cold tire inflation. @gaijin thanks again for all the responses and patience! It's very much appreciated!

 

[gaijin]

@Hugh Bris 1 ,

If all you're going for is ground clearance, then let me throw some numbers at you that you can verify on your truck:

If my LT285/70R17 tires have a ground to center hub measurement of 15.75", then I calculate your LT285/75R17 tires should have a ground to center hub measurement of 16.25" - you can check this measurement against your tires.

If this is the case, then you would "lose" 0.5" in ground clearance going from the LT285/75R17 tires to the LT285/70R17 tires.

Make sense?

 

[gaijin]

Yep, that helps! Thank you! Checked pressure. It's right at 37psi. Looks like the measurement from ground to center of the hub is ~16.25" so the ground clearance difference would be about 0.5" between the 285/75r17 and 285/70r17 on Rock Warriors at "normal" cold tire inflation. @gaijin thanks again for all the responses and patience! It's very much appreciated!

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Geez!!! Couldn't you have waited just a few more seconds before posting? I would have looked a whole lot smarter...

I was typing while you were posting

 

[Hugh Bris 1]

@Taco2Cruiser said:
285/75r17 KO2 on Rock Warriors compared to 285/75r17 Ridge Grapplers on Evos. Both with 5,000 miles on them under a 200. Both inflated to 37 psi (per @gaijin... never question gaijin!)

Both are 32.63" tall when mounted on the recommended 8" rim, under the the same 200's weight according to one of Bud's lasers.

You (@Hugh Bris 1) said:
Both from this post by @Taco2Cruiser and on my own truck the 285/75r17 BFGKO2 on Rock Warriors measures right at 32.5" to maybe 32.625" at the peak and ~32.25" at the edge (the perspective in these photos makes the edge diameter difficult to be certain) at the recommended 37psi for these tires.

Looks to me like you two agree on the total height when mounted on the truck under load.

Ah, yes. Of course you are correct. My mistake was that I related the pictures in that post which are unmounted. While I read the post, and it obviously clearly states mounted, I focused on the pictures being unmounted.

 

[gaijin]

Ah, yes. Of course you are correct. My mistake was that I related the pictures in that post which are unmounted. While I read the post, and it obviously clearly states mounted, I focused on the pictures being unmounted.

In case you (or anyone else) is interested, the math was really simple.

LT285/70R17 tire has a "spec" diameter of 32.8" and a measured ground to center of hub measurement of 15.75".

Half the spec diameter is 16.4" and the measured ground to center measurement is 96% of that, or 15.75".

Translating that to the LT285/75R17 tire which has a spec diameter of 33.9", just take half of that (16.95") and multiply by 96% to get 16.272" (rounded to 16.25").

Having not tested over a range of tire sizes I can't say for sure, but as a general rule of thumb it might be OK to say that the effective (mounted, under load, at RCTIP) ground clearance height (ground to center hub) for any tire is 96% of half its specification diameter.

I'm just rambling now - past my bedtime...

HTH

 

[Hugh Bris 1]

In case you (or anyone else) is interested, the math was really simple.

LT285/70R17 tire has a "spec" diameter of 32.8" and a measured ground to center of hub measurement of 15.75".

Half the spec diameter is 16.4" and the measured ground to center measurement is 96% of that, or 15.75".

Translating that to the LT285/75R17 tire which has a spec diameter of 33.9", just take half of that (16.95") and multiply by 96% to get 16.272" (rounded to 16.25").

Having not tested over a range of tire sizes I can't say for sure, but as a general rule of thumb it might be OK to say that the effective (mounted, under load, at RCTIP) ground clearance height (ground to center hub) for any tire is 96% of half its specification diameter.

I'm just rambling now - past my bedtime...

HTH

LOL! That's great! I follow the math and logic. This type of figuring things out is right up my alley! It would be interesting to see more comments on this formula to see how well this works out. 2 data points are hardly enough and I don't have a good way to add more myself.

 

[Hounwas]

Hi everyone,
Ok it’s time for new tires went wheeling yesterday and I need tires really bad VFA below. So I’ve read just about every thread I could I’m still unsure of what to get. This is what I have.

Ome 2” lift
No UCA
Rock warriors

So my question is can I fit 285/75/17 on without rubbing or spacers? Or should I just the smaller 285/70/17 which I currently have on that came with the rock warriors. I’d love to get the bigger tire but if it’s going to be hassle I don’t know if it’ll be worth the extra inch. Also my buddies are saying to get the toyo open country but I don’t see much on the forums about them. Thanks for your time.

If you have a 2" lift and no UCA, you might be able to get away with 285/75s without rubbing, but it will be close. You might be better off sticking with 285/70s or even 275/70s to be safe. As for tires, the Toyo Open Country is a good tire, but there are a lot of other good choices out there. Do some tire compaison research and see what other people with similar setups are running.

 

[bloc]

If you have a 2" lift and no UCA, you might be able to get away with 285/75s without rubbing, but it will be close. You might be better off sticking with 285/70s or even 275/70s to be safe. As for tires, the Toyo Open Country is a good tire, but there are a lot of other good choices out there. Do some tire compaison research and see what other people with similar setups are running.

Hopefully they've figured out tires since this was posted almost 4 years ago.

And 275/70R17 isn't even on the table.. absolutely no reason. 285/70R17 was an option offered by toyota for our trucks.

 

[coleAK]

Does anyone have the actual diameter of the 285/70r17 KO2 when "normally" inflated and mounted?

Here are my KO2s (285/70-17, C load) have ~3k miles on them and measure pretty close to 33” Horizontally. ~32.1/2” vertical. Mounted and on the truck that is.

I have a stock ‘13 LX. And my wheels are +35 offset. I had to do considerable plastic manipulation to stop rubbing going up to 285/75-17 would have been trimming/cutting. I would have been very happy to get a set of RWs and looked for 7-8 years for a set in Alaska. Would have been less liner work with RWs more medial offset, but I still think 385/75’s would be a bunch of work.

 

[VUHNILA GUERILA]

A. Wanted to thank everyone on this thread...helped with my RW purchase and BFG
B. RW should have been stock.

2020 Land Cruiser Heritage Edition. All Stock except, 2010 Tundra Rock Warrior Wheels and 285/70/17 with BFGoodrich All-Terrain T/A KO3.

No Rubbing (yet).

 

[rlynch356]

resurrecting this thread a bit....

Looking at going from 285/70-17 to 285/75-17 on RW's (currently with a spidertrax spacer but I would prefer that comes off...but can stay if needed)..

OME 2" (50mm) Medium duty lift i.e. not BP-51.. Nitro Chargers.... with OME UCA's fitted..
bumpers (CBI but I doubt anyone has data for that..),
mud flaps removed ( I need to come up with a solution for some there..)

My question is really about full flex rubbing.. Any issues there or in general with Rubbing?
The 75 KM3 is 33.9 vs the Cooper AT LTX 32.83..

So 1" larger (.5" at the diff.. height)

The tires I am looking at are the KM3 and Nitto Ridge Grappler - I would rather stay with an AT but..... here on the east coast US... M/T's are pretty much necessary with clay mud.. they help some.. more than the Cooper A/T's I have for sure given my recent winching experience.. M/T's might have helped..
Maybe.. but really it's all about the ability to clear the tread of mud better. - Anyway I digress...