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The Tire and Speedometer Saga

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beez

beez

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I know the topic of tire sizes and speedometer error has been going back and forth for some time now but I have a few questions on the topic. I recently purchased some new 16” Panasports and would like to put on some high performance tires. I did some quick research on the tire sizes and the speedometer error that I will encounter with each size. Basically from the numbers I should go with 205/65R16 or 215/65R16 to get the closest numbers. The problem is there is a very limited (ie I didn’t find any) high performance tires in this size. I did find some high performance tires in the 225/60R16 size, but I believe they are too wide from what I’ve been told which is disappointing in that they are nearly the exact same size as the stock tires. If I drop down to 215/55R16 there are a number of choices and pretty much where I am leaning at this time. Again, the problem is these tires are about 5% to fast so if my speedometer said 60mph I would be traveling at 57 (theoretically… I know the tire pressure and other factors aren’t figured in). This isn’t too much of a problem as my truck is about 5mph faster than the speedometer read since the tires are larger that stock. All this said, I am curious to know how difficult it is to recalibrate the speedometer, if it’s possible to do at home, and do they make some kind of calibration box for this purpose (I want to use my stock speedometer). Also, are there some high performance tire options out there that I haven’t found?

Now if they had 17” Panasports…

Thanks,

Adam '73 TR6
 
How high performance do you need with a car with 100 hp and Redlines as OE?

I have Panasport 16s shod with Yokohama AVIDs. Price was about $100 a corner fitted and balanced and they are a vast improvement over stock.

A quick tire rack might help you here. There are a whole bunch of UHP all-season for example.
 
The tread pattern is also important to me, I think the high performance summer tires look alot nicer than the all season. I don't plan to drive my car alot in the rain and never in the snow. I would like something that will really stick when I take turns at a high speed. I would like to take my car on some of the sports car club courses without having to change tires... tire life isn't important.

I've searched a good deal at tire rack and a few of the other tire sites as well.
 
I bought a ratio adapter with cable ends from A.C.I Engineering, 6720 Lovers Lane, Portage, MI 49002 five years ago for $72. I converted to an OD trans and could not find a tranny gear drive that came even close. The math provided by A.C.I was close, but I ended up taking the car to a local shop that put it on a dyno and installed the correct gears for another $50. I suggest scrolling back to my TIRE MATH thread where Geo Hahn posted an address that shows how to callibrate the speedometer -- this seems a less expensive way to go since you are only about 5% off.
 
Thanks for your help! I recently upgraded to a J-type overdrive. Do I need to adjust my speedometer to work with this transmission or will the gears in the overdrive take care of this for me?

Thanks,

Adam
 
I think going with an overdrive gearbox makes no difference to the speedometer. You are essentially measuring propshaft speed.

As I recall, the reason there were different speedometers sometimes associated with overdrive-equipped cars was that they had different rear-ends (which does effect the speedo).
 
The link from Geo Hahn was probably for the PDF document by Anthony Rhodes on Smiths & Jaeger speedometers. If you google for Anthony Rhodes and Smiths you'll find it. It's 27 pages of great information.

Incidentally, the calibration methods in the PDF will allow you to match the needle to the correct speed but won't address odometer error as that is based on gearing.

You could always go for an AutoMeter or VDO electronic speedometer instead. These allow user input of the pulses per mile OR with the VDO you can drive a measured mile and the instrument will measure the pulse/mile so your speedometer and odometer are matched exactly to your tires and drivetrain.
 
Adam, my wife's daily driver, a 2000 Nissan Maxima, uses 215/55/16 tires, and we have found the Dunlop SPA2 a good perfomance choice; good grip and stiff enough sidewalls to give good turn-in and steering feedback.
Also a brand name that was British (now Japanese owned) when the car was made, if you care about such things.I like the Yokohama suggestion from Alana too, and in an earlier thread someone mentioned being happy with the Michelin HydroEdge.

Let us know what you choose, and how it works out, this seems to be a hot topic.
Simon.
 
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