Delica Canada | Mitsubishi Van Club

Green1 wrote:While I can't speak to tire size on this one, keep in mind that pretty much all vehicles from the factory have the speedometer set high.

Where DO you come up with this stuff?

Wow, that's interesting. So then if a guy knew exactly how much off his speedo was with any given tire, he could conceivably calculate which size would net an accurate (or more accurate) reading.

Possibly, however keep in mind that you are unlikely to find a size that will make both the odometer and the speedometer accurate, I'd try to get the odometer as close as possible to correct, and simply get a good feel for how far out your speedometer is at that size.

I do have GPS but unfortunately, haven't been able to get certain functions from it; such as anything mileage or fuel consumption related. (The thing won't even accept my cell's phone book.)

You don't need mileage or fuel consumption info from it, just the speed it shows while you are driving. compare this to what your speedometer says to get an idea of the accuracy of the speedometer (due to limitations in GPS, do this while travelling on a straight line road at a constant speed)

mararmeisto wrote:

Green1 wrote:While I can't speak to tire size on this one, keep in mind that pretty much all vehicles from the factory have the speedometer set high.

Where DO you come up with this stuff?

A large cross section of vehicles coupled with GPS and/or speed signs, coupled with common sense. (large companies aversion to being sued)
do you have proof to the contrary?

Green1 wrote:

mararmeisto wrote:

Green1 wrote:While I can't speak to tire size on this one, keep in mind that pretty much all vehicles from the factory have the speedometer set high.

Where DO you come up with this stuff?

A large cross section of vehicles coupled with GPS and/or speed signs, coupled with common sense. (large companies aversion to being sued). [D]o you have proof to the contrary?

Two things: the fact that most owner's manuals cite correct tire size as crucial to correct speedometer readings (not odometer); and, speed is what the driver has control over (they can adjust how fast they are going, not how far).

mararmeisto wrote:Two things: the fact that most owner's manuals cite correct tire size as crucial to correct speedometer readings (not odometer); and, speed is what the driver has control over (they can adjust how fast they are going, not how far).

The first is a standard disclaimer so that you don't put wildly different tire sizes on and then sue them because the speedometer is way off, and the second is simply irrelevant to the point I was making. Neither of which contradicts what I said. People will sue big companies if they think they can at all blame them for their own actions, an inaccurate odometer is no "safer" for the company if it reads low vs high, so accuracy is a good goal. A speedometer on the other hand is quite likely to net a lawsuit if it reads even one km/hr less than the number written on a speeding ticket, so there is great incentive for the company to make sure that if it is out even the slightest bit, it's on the high side and not the low side. As technology has progressed with new vehicles being more and more computer controlled, they can set the tolerances more precisely, as such speedometers on new vehicles today are quite close to accurate (though still a couple km/hr above actual) whereas on older vehicles the tolerances were less, so the error margin the company gave themselves was more. If you have ever seen a vehicle which, from the factory, has a speedometer reading that is dead accurate, or reads LOW, please let me know. I certainly never have.


*update* I hadn't realized this, but apparently it is more than just big companies covering themselves against lawsuits... it's actually a legal requirement on UNECE vehicles (possibly also on domestic vehicles, I didn't look them up)

http://en.wikipedia.org/wiki/Speedometer wrote:UNECE regulation in that they specify that:

* The indicated speed must never be less than the actual speed, i.e. it should not be possible to inadvertently speed because of an incorrect speedometer reading.
* The indicated speed must not be more than 110 percent of the true speed plus 4 km/h at specified test speeds. For example, at 80 km/h, the indicated speed must be no more than 92 km/h.

The standards specify both the limits on accuracy and many of the details of how it should be measured during the approvals process, for example that the test measurements should be made (for most vehicles) at 40, 80 and 120 km/h, and at a particular ambient temperature. There are slight differences between the different standards, for example in the minimum accuracy of the equipment measuring the true speed of the vehicle.

Green1
Is there any subject you're not an expert on?? It seems you are willing to argue with everyone on any subject!
TLBF

thelazybrownfox wrote:Is there any subject you're not an expert on??

Are you seriously ask this question

Green1 wrote:Neither of which contradicts what I said.

You're right, I didn't contradict what you said. In fact, I'm still not contradicting you.

mararmeisto wrote:

Green1 wrote:Neither of which contradicts what I said.

You're right, I didn't contradict what you said. In fact, I'm still not contradicting you.

Green1 wrote:...[H]owever keep in mind that you are unlikely to find a size that will make both the odometer and the speedometer accurate, I'd try to get the odometer as close as possible to correct, and simply get a good feel for how far out your speedometer is at that size.

I can't believe I missed this: there is a simple solution to your dilemma. Since the speedometer and odometer are centred in the instrument cluster, and the speedometer is above the odometer, put the size-appropriate tires for the speedometer on the front wheels and the size-appropriate tires for the odometer on the rear wheels. That should satisfy the specifications for both meters.

Love the humour
TLBF

thelazybrownfox wrote:Love the humour
TLBF

This is no joking matter: if he puts the wrong tires on the wrong wheels, BOTH meters will be wrong!

It's been my understanding that the odo/speedo are both driven by the same cable, certainly from my motorcycle days...but what do I know? You've actually given me an idea though... What about leaving my 235's on the front and replacing only the rear tires with something a bit bigger? (assuming the rear drives the dial cluster.) Is there anything illegal or dangerous about that? We're talking about very similar sizes. Could it be a problem in 4x4 mode?

Would anyone care to guess what replacement size would give the most accurate reading given that my 235's put the speedo at 83 when I'm actually doing 77? I still think it's really weird that my 235's are that much off. 235 is supposed to be very close to stock size so the challenge, at least with my van, is not so much to replicate stock size as to simply find the correct size.

A dealer I spoke to on the phone said the 30/9.5 (which someone here also suggested) would be good but they're actually a bit larger than the alternative: 265/70's, which I'm kind of leaning towards.

What do you think?
I definitely don't want to change tires and end up with just a different logo but the same problem.

Drumster wrote:You've actually given me an idea... What about leaving my 235's on the front and replacing only the rear tires with something a bit bigger? Is there anything illegal or dangerous about that? We're talking about very similar sizes. Could it be a problem in 4x4 mode?

It's not considered a good idea on any 4x4 vehicle to have mismatched tires, however with the centre Dif on the L400 I don't know how much of an issue it really is.

I think the more relevant point would be that the odometer and speedometer both connect to the same wheels, so this won't have the effect of correcting both...

Would anyone care to guess what replacement size would give the most accurate reading given that my 235's put the speedo at 83 when I'm actually doing 77? I still think it's really weird that my 235's are that much off. 235 is supposed to be very close to stock size so the challenge, at least with my van, is not so much to replicate stock size as to simply find the correct size.

before going too far down that road, I'd recommend considering whether you want the speedometer, or the odometer to be more accurate, I'd rather the odometer be correct myself.

I definitely don't want to change tires and end up with just a different logo but the same problem.

To be perfectly honest, if your speedometer reads 83 when you are doing 77, it's well within spec, and I wouldn't worry about it, just know that it reads a little high, as does everyone else's

Green1 wrote:I think the more relevant point would be that the odometer and speedometer both connect to the same wheels, so this won't have the effect of correcting both...

As far as I am aware, in every instance I have seen the Odometer and Speedometer are driven by a single rotating cable, and the division of speed vs. distance is computed directly within the gauges. I believe it is usually a front wheel for ease of maintenance/installation. (This was the case in my Hyundai Excel, and is the case in my 89' 4Runner).

Mr. Flibble wrote:

Green1 wrote:I think the more relevant point would be that the odometer and speedometer both connect to the same wheels, so this won't have the effect of correcting both...

As far as I am aware, in every instance I have seen the Odometer and Speedometer are driven by a single rotating cable, and the division of speed vs. distance is computed directly within the gauges. I believe it is usually a front wheel for ease of maintenance/installation. (This was the case in my Hyundai Excel, and is the case in my 89' 4Runner).

That's exactly what I was referring to, so basically, adjusting tire size will adjust both gauges by the same amount, so if the 2 aren't equally accurate, any adjustment that "fixes" one will "break" the other.