A speed observation

[rogdeb]

Although this post could maybe land in Tires/Technical ??

Used to be that my odometer and GPS read speed with a 3 mph difference at 85 mph. Since mounting the Dunlop Roadsmarts I only see a difference of 1 mph.

Just an observation -- doesn't matter why or how I guess. Others may vary, I'm sure they do.

 

[Fred W]

Although this post could maybe land in Tires/Technical ??Used to be that my odometer and GPS read speed with a 3 mph difference at 85 mph. Since mounting the Dunlop Roadsmarts I only see a difference of 1 mph.

Just an observation -- doesn't matter why or how I guess. Others may vary, I'm sure they do.

Assuming that the speedo's reported speed is higher than actual (GPS reference), if there is now less error, the reported speed is now lower than it was before, so that would have to mean that the circumference of the new tire is slightly bigger (by ~2.4%) causing fewer wheel rpms at the same actual ground speed. By the way, the difference in tire diameter would work out to a bit over 0.6 inch. That of course would be split in half for the radius to the axle. so 0.3" could just be how worn your previous rear tire was when you measured.

The Dunlop claims a diameter of 24.84". What back tire were you running before?

 

[rogdeb]

Fred,

Well worn Avon Azaro's :lol:

Thanks -- I knew one of you guys would supply the math

 

[stealth1]

The difference in circumference between a fresh tire and a worn out one might be enough to account for the change.

 

[Fred W]

Fred,Well worn Avon Azaro's :lol:

Thanks -- I knew one of you guys would supply the math

Damn, well... unfortunately Avon "Tyres" no longer list the specs for the 180/55-17 for the Azaro. But just for grins, lte's look at their replacement, the "Storm ST". They have a specified diameter of 629mm (24.76 inches) so pretty close. Must have been the treadwear.

 

[kolonial72]

I can only surmise that some really bored people lurk in this forum.

 

[stealth1]

I can only surmise that some really bored people lurk in this forum.

Don't disturb me now!

I've got some paint drying!

:clapping:

 

[rogdeb]

I can only surmise that some really bored people lurk in this forum.

I was logged on at the time and had nothing else to do :lol:

 

[fjride]

Although this post could maybe land in Tires/Technical ??Used to be that my odometer and GPS read speed with a 3 mph difference at 85 mph. Since mounting the Dunlop Roadsmarts I only see a difference of 1 mph.

Just an observation -- doesn't matter why or how I guess. Others may vary, I'm sure they do.

How do you like the Roadsmarts compared to the Avons. I have been using Avons exclusively, but the front tires have cupped-fels like riding over little road rodents

 

[Fred W]

I can only surmise that some really bored people lurk in this forum.

Bored? How could we be bored when there are tire threads going on?

 

[rogdeb]

Although this post could maybe land in Tires/Technical ??Used to be that my odometer and GPS read speed with a 3 mph difference at 85 mph. Since mounting the Dunlop Roadsmarts I only see a difference of 1 mph.

Just an observation -- doesn't matter why or how I guess. Others may vary, I'm sure they do.

How do you like the Roadsmarts compared to the Avons. I have been using Avons exclusively, but the front tires have cupped-fels like riding over little road rodents

I like them so far - seem pretty stable and good feedback - haven't had them in the rain yet though. Nor have I put enough miles on them to make a decent comparo with the Avons. There's a good few on the forum who have though.

I've been through 4 sets of Avons and never had the cupping problem you have -- only with the Bridgestones.