Tire Size & Speedometer Correction - Evidence

[MarkLawson]

I'll admit to an odd quirk I live with. That is that when I look at my speedometer, I'd like for it to tell me how fast I am going, not within 3-4 mph of how fast I am going. When I bought and installed my replacement rear tire (Michelin HydroEdge 215/60R15), I found my speedometer error rate dropped significantly. Now my speedometer reads either the same or within 1 mph of my Garmin Zumo 550 GPS. See the picture below for proof. This is typical of any speed I have checked. I've run this tire for over 11,000 miles and have had no Nanny issues associated with it. I have worn through 1/3 of the legal tread, so expect to get another 22,000-23,000 miles out of it before changing. Picture was taken last Monday night on the way home from Bible study.

 

[ARtraveler]

Thank you for posting. Very good information for those who use non-OEM tires. :thumbup:

 

[SNOOPY]

Nice :thumbup:

 

[ulflyer]

I got exactly the same speed results with a 205-60-15 General and now with the Pirelli P4.

 

[Chupaca]

Let's see..!!

if you want accurate use your gps. Not even from the factory are the spot on. Highway speed signs always differ so gps is best. Different tires can make a difference but then not that much....:dontknow:

 

[Highwayman2013]

What air pressure do you run in that Michelin ?

 

[MarkLawson]

What air pressure do you run in that Michelin ?

I'm running the BRP recommended pressure, around 28 psi. After 11,000+ miles, I ran a tread depth gauge across the tire and found that the tread depth is even across the width of the tire, so I'm satisfied. I also have the Michelin Defenders on the front (175/65R14) & am running around 18-20 psi in them. I don't have that many miles on them yet, but initial indicators are that they're wearing evenly and should last 50,000 miles or more.

 

[bluestratos]

Have you got a picture of the rear tire, the correct tire is a 225/50R so I was wondering what the 60 looks like and how it fits the Rim.

 

[Hawk]

Have you got a picture of the rear tire, the correct tire is a 225/50R so I was wondering what the 60 looks like and how it fits the Rim.

Hmm, I have noticed my speed is off as well compared to my Garmin 660 (as much as 4mph in some cases), just replaced mine with the 225/50 Khumo or I would have tried a 60 as well.

PS. You need to drive faster, old man!!

PSS. You need gas!!!

 

[jerpinoy]

You can't go wrong with gps reference., thanks also with the tires and pres info.

 

[sledmaster]

Tire Size Specs

Thanks for the great post about speedo accuracy Mark, great info! :clap:

There are many of use who run 4-ply automotive tires on our Spyders. In the stock 225/50R15 rear tire size there are limited options, this is why many have tried other sizes to open up the options of what is available. As a side benefit, the speedo becomes more accurate, as Mark has shown us.

In regards to this, here are some of the other sizes and how they differ in diameter. The first number (225, 215, 205) is the tire width in mm, so going to a 215 instead of a 225 width you are going 10mm narrower (which is 0.39"). Going to a 205 is 20mm narrower (0.79").

Diameter is not as clear cut. The stock 225/50R15 tire is 23.86" in diameter (or 606mm). When you go to a 215/60R15 it is 25.16" (639mm) in diameter, or +5.4% larger. Another popular size with many options is 205/60R15 and this one is even closer in diameter to the stock tire at 24.69" diameter (627mm) which is only +3.5%, but is slightly narrower in width. Both of these sizes have been used by forum members with good success. The nanny does not care about this size difference.

There are some other sizes, but very few tires are available in these. Like 215/55R15 (+1.9%) or 205/55R15 (+0.1%) sizes, they are closer in diameter to the stock tire than the 60s. There’s also 225/55R15 but this too is tough to find, that one is +3.7% in diameter.

Here is a great link to a tire size calculator I use to figure all of this out - http://www.tacomaworld.com/forum/tirecalc.php

The 4-ply tires seem to be slightly heavier, but this is perfectly acceptable for the higher quality and durability. I have been using 4-ply tires for years on Spyder for their more even wear and greater durability. Just pay attention to their speed ratings, tread wear rating, traction and temperature ratings. Personally, I will only use a tire that is AA or A for traction, only A for temperature, and H (130 mph) or V (149 mph) for speed rating (I will not use a T rated tire, that is only 118 mph). Hope this helps!

 

[MarkLawson]

Have you got a picture of the rear tire, the correct tire is a 225/50R so I was wondering what the 60 looks like and how it fits the Rim.

The tire fits the rim perfectly

 

[BLUEKNIGHT911]

SPEEDO ACCURACY

It's been discussed here many times before.....with the stock size tire ( 225/50 - 15 ) the speedometer is not accurate. With the 205 0r 215 / 60 it's much closer to accurate ..........and don't look for the Michelin Hydro- Edge they stopped making them ( :gaah quite awhile ago, .......but you may still find some hidden away....Mike :thumbup:

 

[MarkLawson]

It's been discussed here many times before.....with the stock size tire ( 225/50 - 15 ) the speedometer is not accurate. With the 205 0r 215 / 60 it's much closer to accurate ..........and don't look for the Michelin Hydro- Edge they stopped making them ( :gaah quite awhile ago, .......but you may still find some hidden away....Mike :thumbup:

www.TireRack.com says they have 'fewer than 3' in stock ( http://www.tirerack.com/tires/TireS...omSizeSearch=&width=215/&ratio=60&diameter=15 ) @ $108.00 each (Closeout) + shipping. I understand their Defender is the replacement for the HydroEdge.

 

[bluestratos]

Looks close to stock width wise and gives a lot more options in tires.

The tire fits the rim perfectly

 

[den1953]

Excellent Rain Tire Too

That's another thing about car tires, specifically how they perform in rain. Hydroplaning is the last thing you'd want. I changed aspect ratio on the rear tire of that Triumph Rocket III and the circumference was something like 2 percent smaller on the longer lasting Michelin I went to. That made the odometer register 100 miles when I had only covered 98. That doesn't sound like much until you multiply the odometer error. 1000 miles only being 980 or 10,000 being 9,800 miles etc. My guess if you're car tire gets you closer or dead-on with your GPS there should be zero or near zero odometer error as well.

 

[xmanjr]

It's been discussed here many times before.....with the stock size tire ( 225/50 - 15 ) the speedometer is not accurate. With the 205 0r 215 / 60 it's much closer to accurate ..........and don't look for the Michelin Hydro- Edge they stopped making them ( :gaah quite awhile ago, .......but you may still find some hidden away....Mike :thumbup:

Tire Rack.com has a few left. I just bought one on Saturday for 108.00 plus shipping. Ordered it Saturday and it was delivered on Tuesday. Can't wait to have it installed to see how it rides, I have 12,200 miles on my Kendall, center is worn into the wear strips. Russ

 

[tigerdr]

Only 2 Michelin HydroEdge remaining. I order one 5 minutes ago.

 

[MarkLawson]

Another picture @ another speed taken this past Sunday:

 

[SPYD3R]

215/60R15

215/60R15.....????
you should be riding on a 225/50 R15.... the '50' vs. '60' is what's skru'n u up....
the 225 vs. 215 is the width.... no issues there, except you don't have as much 'rubber' on the ground...
'50' vs. '60' is the diameter of the tire... that makes all the different in speedo numbers... as well as MPG...
burn the BAD-BOY up, and get u a 225/50 R15 ASAP.....