03-07-2008, 11:22 PM
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#1
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Member
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Question regarding upsizing tires
This might sound like a total noob question, but every tire calculator I use state that by using different sized tires will throw off the speedometer, thereby affecting speed, braking etc. For the members who have upsized their tires...did you guys have to recalibrate the speedometer and how much does braking change?
I've been thinking about doing the lift/tire upgrade for a while now, and before I do it I would like some firsthand inputs from members who have already done it. Any drawbacks, concers and general opinions would be greatly appreciated.
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03-08-2008, 04:29 PM
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#2
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Re: Question regarding upsizing tires
Quote:
Originally posted by DarksideSurf
This might sound like a total noob question, but every tire calculator I use state that by using different sized tires will throw off the speedometer, thereby affecting speed, braking etc. For the members who have upsized their tires...did you guys have to recalibrate the speedometer and how much does braking change?
I've been thinking about doing the lift/tire upgrade for a while now, and before I do it I would like some firsthand inputs from members who have already done it. Any drawbacks, concers and general opinions would be greatly appreciated.
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As far as speedo re-calibration is concerned I think most just live with it.
As far as braking goes the overall diameter and weight of the tires will have some negative effect. The shorter and lighter the wheels/tires the more braking power the stock brakes will be able to provide. You can think of it as a lever arm... The closer the brake and tire diameter are to each other the better the brakes will be able to stop the truck; tiny brakes and tall tires = long stopping distances.
Taller tires lower the RPM at a given speed. (Note: The speedo will indicate the same speed at the same rpm with an un-re-calibrated speedo even though the vehicle will be travelling faster [gps 'across-the-ground' speed].)Acceleration will suffer slightly with taller tires. Tall tires also stress axles and differentials somewhat more than stock height tires. The driveline of the 4Runner seems to handle most of the extra stress pretty well. You don't read tons of posts about blown axles etc. until you get into really big tires.
It seems as though most folks who stay in the 32"-33" range don't have driveline issues as a rule.
When the new tires are installed it may trip a VSC fault. A relatively simple 'reset' of the system will take care of it. I don't quite grasp why the fault occurs but some members have had it. It seems to me if you change all 4 tires it shouldn't matter.
Consider your spare too. The carrier of the 4Runner will hold a pretty big tire. Having the same size spare as the rest of the tires isn't that important; a tire of the same height is (tall, skinny ok).
Good Luck 
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Chris
07 Salsa SR5, 4wd Cyclone pre-cleaner , Aux Transmission Cooler, Hidden Hitch 70779 (600/6000lbs, WDH=730/7300lbs), AirLift 1000, FJCruiser front springs (& now rear too!), Axle Vent Mod, Swaybar Bushing Upgrade, V6 Tick Reduction, VSC off mod, Maplight Mod, 255/75/17 Goodyear Wrangler SAs, Tailpipe Mod
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03-09-2008, 09:18 PM
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#3
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My speeometer is off about 2 mph after going to BFG all terrain 265/70/17 at 70 mph. It is only off about 1 mph at 35. I take mine off road in the dessert at times and I wanted a strong tire for playing in the desert. They work great for this. With the Daystar lift and BFG tires I think it rides slightly better than stock, handling is about the same also. I probably lost 1 or 2 mpg. The taller tires hurt acceleration some, not bad just not a snappy. Braking is also slightly worse. I am happy with it now and really like the added ground clearance in the rocks. If I were not going of road I would rather leave it stock.
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03-09-2008, 10:15 PM
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#4
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Quote:
Originally posted by 03_4x4Runner
My speeometer is off about 2 mph after going to BFG all terrain 265/70/17 at 70 mph. It is only off about 1 mph at 35.
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Same here , no biggie upsizing.
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03-09-2008, 10:21 PM
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#5
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If you have a GPS it will tell you your real actual speed. This makes it real easy for you to know.
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03-09-2008, 11:04 PM
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#6
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upsize it, lift it, add spacers, do it all man!
check it man!
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03-10-2008, 12:54 AM
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#7
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I'm running 265/75/16s and checked the speedo with a GPS last week. Trying to maintain exactly 70 on the speedo the GPS showed between 71.0 to 71.3. To me that's not enough of a difference to adjust for. If you run a larger tire or demand a more exact speedo reading you could try a Yellow Box
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03-10-2008, 12:36 PM
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#8
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I check mine with radar gun so it may not be as accurate as a GPS or maybe more I don't know.
I waited until we had one re calibrated from the factory .
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03-10-2008, 03:26 PM
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#9
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This calculator can help too. It computes the change in speedo accuracy. http://www.miata.net/garage/tirecalc.html
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03-10-2008, 04:52 PM
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#10
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Yeah that's been a sticky inhre for a while. I use this one...
http://www.1010tires.com/TireSizeCalculator.asp
A bit more informative IMHO.
I've hardly been using my 4Runner except during the winter. I've been enjoying my Camry but the specific setup I'm looking at is upsizing the tires to 265/70/17 and the 2/1 lift spacer kit. Judging from the replies it should be a pretty minimal change.
Good call on using my nav's speed sensor.
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2007 Black Toyota Camry SE V6
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03-10-2008, 06:51 PM
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#11
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Quote:
Originally posted by sbbamafan
If you have a GPS it will tell you your real actual speed. This makes it real easy for you to know.
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If you have a factory navigation or an in-dash aftermarket unit, upsizing the tires can cause havoc on the system because it relies on speed pulse data as well as GPS signal to track movement.
There is a calibration mode for installing new tires, but it seems to be limited to a certain percentage of the original tire diameter.
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03-11-2008, 01:33 AM
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#12
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Re: Re: Question regarding upsizing tires
Quote:
Originally posted by CJ3Flyr
Consider your spare too. The carrier of the 4Runner will hold a pretty big tire. Having the same size spare as the rest of the tires isn't that important; a tire of the same height is (tall, skinny ok).
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Anyone know what size tire it will hold? assuming a slightly more than stock aggressive tire, but maybe not like a Mud terrain one.
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03-11-2008, 03:31 AM
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#13
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Re: Re: Re: Question regarding upsizing tires
Quote:
Originally posted by keylay31
Anyone know what size tire it will hold? assuming a slightly more than stock aggressive tire, but maybe not like a Mud terrain one.
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32" BFG KO with no room to spare, so to speak, between the hitch and panhard bar.
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03-11-2008, 08:25 AM
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#14
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JB, no doubt that you are an offroader, from looking at the pic's, just kidding 
If you are interested on a receiver mounted spare tire holder, consider CBI offroad. They make a very nice unit for 250.00. I will get pic's posted when mine gets back from power coating.
I had to do this route since my MT's were hitting the suspension underneath. I didn't even have the gap you have.
Paul C
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03-11-2008, 08:33 AM
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#15
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Speed change & braking
No change that I can tell on braking, still will put you though the windshield on a panic stop.
Speedo, yes it will throw everything off.
I have attempted to get mine re-calibrated, but my local dealer was clueless, telling me I had possibly voided the warranty by putting on a larger tire. Haven't needed any warranty work on the drive line but may have something to worry about 
From many attempts of testing. I feel that the move from 265 65 R17 to 265 70 R17 changes my mileage reading by about 6%. I determined this by running with a Garmin GPS on several trips. Approximately for every mile, the speedo is short 1/10 of a mile.
Paul C
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