255/80R17s With Automatic Transmission - Page 2 - Toyota FJ Cruiser Forum
Wheels and Tires This section is for discussing the different wheel and tire options for the FJ Cruiser!

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#11 (permalink) Old 06-24-2012, 05:45 PM
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Re: 255/80R17s With Automatic Transmission

Quote:
It hunts in the hills...
How are you using that idiomatic expression Old Cruiser? Do you mean that they work great, i.e., 'this dog hunts', or 'the big tires so screw up the onboard computer and auto trans that it can't figure which gear to shift to?'

I'm glad to hear that about the MPGs guys! That's something I'm sensitive to, up to a point.

By the way, this weekend I finally got around to crawling under my new FJ and figuring out jack points and how well the stock jack works, and I got real up close and personal with the body mount 'thingie'. Now I finally understand a comment you made Old Cruiser about the miserable 'ears'. When I actually saw the situation my dead set stance against a BMC changed drastically. Before, I was dead set against it. Now, I'm considering it a viable option if these tires rub my body mount, and I can't get it streightened out with an alignment. I'm really a conservative person, and generally don't do risky things, but I'm thinking I ought to 'go for it' and get these tires. That is, opposed to the conservative thing and just get no risk 275/70R17s that give me a measly 0.25" more ground clearance, but represent 'no risk'.

Anyway, a BMC represents something of a 'rite of initiation' around here.

The 1st stage of the initiation is acquiring the knowledge of the meaning of a 'BMC'. The 2nd stage is getting it done!
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#12 (permalink) Old 06-24-2012, 06:00 PM
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Re: 255/80R17s With Automatic Transmission

cantgetin, in my experience with a taller tire, the 285/70/17, (33`s) the trans hunts and the loosey goosey flex converter is all over the place below 50 mph... now some people say why is that important or matter, well for us, we tow a boat, and most roads are below 50 mph to the state parks and marina`s. The FJ trans drove me nuts with it`s unpredictable behavior. I`ve had many many brands of vehicles, and have to say that my Fords towed best with a larger than stock tire... heck I even ran 285/60/18 Nitto Terra Grapplers on the E250 van and it pulled like a freight train...
so all in all I am not impressed with the toyota trans in this FJ.
Now that I have the stock tire size back on the truck, it is manageable when towing below 50... so inevitably I`ll be looking for stock diameter AT`s when the time comes.
If you do not tow, then you should be fine with a 33. as some already mentioned you first see a little less grunt in acceleration, and a small mileage decrease...
On our FJ, the speedometer was spot on with the 285`s testing with 2 different GPS and road side radar. With the OEM`s the speedo is off, and it makes you think the FJ gets 20-21 mpg...lol...

good luck in your choice! happy forest wheeling! we were just cruising thru the pines this afternoon!
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#13 (permalink) Old 06-26-2012, 10:37 PM
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Re: 255/80R17s With Automatic Transmission

I went from stock to the 255/80/17 BFGs and there was a noticeable difference. The truck is slower, the engine has to work harder to get up to speed, but the trade off is worth it.

I am not gonna sit here and tell you "its is just like stock!" because it isn't. It doesnt bother me at all though because I wanted bigger tires and this aint my first rodeo.

When OC says it "hunts gears" what he means is that the transmission can not decide what gear it wants to be in. Ideally, with the AT, cruising at 60 MPH on the freeway you would be in 5th gear. When you are traversing terrain that is not flat, the transmission will "hunt" and shift between 4th and 5th gear.

The reason that happens is because with larger tires you have changed the power band. So in order to maintain your 60 MPH speed while going up a slight hill, the transmission now has to downshift into 4th to "get more power" and maintain your speed. This is commonly referred to as "hunting gears".

as far as the BMC, if you leave it stock and you wheel it hard, then its a good idea. I can get into the driver side body mount if im really trying. Onroad, at about 3/4 turn i will rub the liner. A leveling kit would also solve any rubbing issues if you didnt want to do the BMC.

I run them on stock wheels with no spacers, no lift and no BMC, just fyi.
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#14 (permalink) Old 06-26-2012, 10:51 PM
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eisenfaust previously said: View Post
I went from stock to the 255/80/17 BFGs

I run them on stock wheels with no spacers, no lift and no BMC, just fyi.
Good to know on the lack of spacers and bmc. Which stock wheels do you have, alloys or steelies?Those BFGs are less bulky than most at tires so I assume that helps you too

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#15 (permalink) Old 06-26-2012, 11:10 PM
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Re: 255/80R17s With Automatic Transmission

Thanks for the extra info esenfaust, and thanks for being kind to this new newbie, who is trying hard to pick up the jargon! What you said cements the understanding I have been gleaning from the usage context of these terms.

So what you and others have been saying about this 'hunting' of gears is really just a matter of degree then, because the phenonomen you describe occurs with pure stock setups with 265/70R17s and automatics too, right? I mean, as one approaches a hill, and tries to maintain, say, 60 mph, at some point, depending on the steepness of the hill, even the stock setup will automatically downshift? And unlike with a manual, where one has the option of lugging it to the extent one can stand it, with an automatic, one has no choice in the matter; its going to downshift whenever its internal logic tells it to? Its just more pronounced with the 255/80s due to the higher gearing caused by them, and the 'hunting' might start on a 4% grade with the 255s, whereas with the stock setup maybe not until a 5% or 6% grade?

Would not about the same thing occur with pulling a load, as Pale Rider suggested? It sounds like in his case there is a double whammy involved, as one has then the loss of power involved in the higher gearing, plus the extra load of a trailer?

The whole point of my reason for starting this thread was to inquire whether anyone thought this powerband shift and tendency to 'hunt' gears was injurious to the automatic transmission in any way, and no one has been able to address that point head on, and the conclusion I have come to is that the only 'bad' effect of the slight increase in gear ratios is this downshifting as you and Pale Rider described, and as I said, that's really a matter of degree. I've also gathered it could be helped by regearing, and I have no idea what that would cost, but it sounds expensive. Being a matter of degree, it seems folks don't get into it too much until they go a lot bigger, such as with 35s.
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#16 (permalink) Old 06-27-2012, 08:13 PM
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Re: 255/80R17s With Automatic Transmission

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Smalldog previously said: View Post
Good to know on the lack of spacers and bmc. Which stock wheels do you have, alloys or steelies?Those BFGs are less bulky than most at tires so I assume that helps you too
Alloys

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CantGetIn previously said: View Post
...
yea, its similar to what a stock truck does it is just more pronounced.

As far as damaging the transmission, honestly it is debatable.

If you tow alot and live in OD, it could decrease the life of your transmission. However, if you just turn off OD or drive around in fourth, it mitigates most of the damage that could occur.

Basically, the more the tranny shifts, the more heat it will build up. The hotter it is, the less effective the fluid is and it can lead to failures. If you are in Cruise control, or towing something and your trying to maintain say 60 MPH, when you are in OD you will shift alot more than being in 4th. The increase in shifting leads to hotter tranny temps.

I have had very good luck with the trick of turning off over drive. I have had several lifted rigs and most of them not regeared due to being a poor kid, and just turning off OD stopped almost all of the gear hunting (some still occurred when i was going like 30-45 on side roads). In my FJ I have towed 4k lbs repeatedly for hours on end with 33's and have had no ill effects. I have done it with OD on and OD off. I didnt worry about it and I have no issues.
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#17 (permalink) Old 06-27-2012, 10:16 PM
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Re: 255/80R17s With Automatic Transmission

I put on 255/85-16 KM2's on about a year and a half ago, love them except for winter driving where one can say they are down right dangerous. For last winter I got a set of Big O AT's to solve that problem. I lost about 1 mpg with the KM2's, but the trade off was worth it for the off road performace gained. Have OME lift and have no rubbing at all, did not do a BMC. I have an AT and it does hunt more in OD with the KM2's on hills and when towing the tear drop than the stock size tires do, I just put it in 4th. On flat ground its fine in OD even on cruise control. There is a slight loss of acceleration but once your moving its all good. My FJ is set up for "Overlanding" and I'am a little over GVWR so the E rating is nice, the AT's are a little more squishy feeling on the highway. I air down to about 15psi when wheeling and they hook up great and give a good ride, I'am sure I could go lower but don't see the need to do so.There is a reason the ranchers/farmers here in Colorado run tall and skinny tires is because it works.
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#18 (permalink) Old 06-28-2012, 06:18 PM
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Re: 255/80R17s With Automatic Transmission

Geez! Thanks Eisenfaust and Dagored! You guys are finally hitting the points I was wondering about!

What you are saying is about how I had it figured, and your stating of it makes me feel better that I'm not too far off in my reckoning. Today I told my local shop try to get me five 255/80R17s, because after several weeks of anguish trying to figure what tires I should get, I finally decided to go with the big, tall 255s. I'm a worry wort, and the last hang up I had over it was the automatic transmission. Years ago I put tall tires on my manual CJ7, but with a manual, one naturally 'manually' works one's powerband to best advantage.

Are you guys referring to your fifth gear in your ATs as your 'OD'? If not, I'd better grab my owner's manual and figure out where my overdrive button is! (I just bought my FJ in May).

Yesterday I got so aggravated with myself agonizing over this that I decided I had to make a decision on it, and even the wrong decision would be better than no decision!
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#19 (permalink) Old 06-28-2012, 06:23 PM
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Re: 255/80R17s With Automatic Transmission

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There is a reason the ranchers/farmers here in Colorado run tall and skinny tires is because it works.
That's all that works here in Pennsylvania too.
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#20 (permalink) Old 06-29-2012, 05:56 AM
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Re: 255/80R17s With Automatic Transmission

I put over 50,000 miles on a set of 255/85/16 KM2s with an automatic no problems at all. I agree with Dagored that they are not the best on ice but they were nothing but great off road on rocks up until I replaced them.

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