72 in a 60

[ElmonteRon]

First the background. Back in September of 2012 i acquired my newest incarnation of ?Trigger?: A flawless, black, 2006 ST1300, with only some 9000 miles on her. Interestingly enough though on the initial ride home, I became aware that the speedo was some 10 MPH off at 60 MPH. I was able to come to this conclusion by pacing other vehicles and later with the use of a GPS unit. The other real nice thing I noticed was the fact that Trigger was on track to hit some 44+ MPG...that would darn near double the range of my previous bike. A real plus in my book.

OK, fast forward 8 or so weeks...Trigger and I are patiently waiting in an intersection and BAM! I?m rear end and sprawled out on the ground with Trigger some 15 feet away in a similar position...but that?s another thread for another time...so with that in mind i spent most of the winter stripping Trigger down; a fargle here and there, cleaning and replacing the parts and pieces that i could.

Now jump to the recent past, Trigger is back on the road, less a saddlebag, but on the road nonetheless. As good as new, except ? my mileage has dropped off. I?m lucky to average some 39 or so MPG. Still not bad, but not what it was cruising at 70+.

Now present day, just moments ago, off for a quick ride in what feels like the first sunny day since last September in the Pacific Northwest. There i am turning a pleasant 75 on the speedo (assuming an odd 65 mph give or take a few), until i spot the brake lights off to the right, followed by the red & Blue strobes calling to me, suggestively telling to me to stop and pull over; since i was the only one around, the light show had to be for me. The short version...I got lucky, the Washington Trooper let me go with a verbal warning [thanks again officer] incredibly, he stated that I was doing 72 in a 60 and that i need to slow it down. The following 4 miles home passed in an eye blink. All i could think about was how? I know I wasn?t going that fast. What did i screw up over the winter. Did the accident mess something up? I know the speedo was off by a large percentage back in the fall...but what changed? DOH...one of the winter projects was NEW TIRES. i replaced the OEM tires with a set of Road Pilots. Could that be it? Once home I grabbed the old GPS and hit the road. Sure enough, now the speedo is off only by a couple. While the speedo now read 64, the GPS displayed 60. oops! And my displayed MPG had also increase immensely, now that i?m only doing 60-ish...go figure.

So the moral of the story is...take the time, check your speedometer after new tires...don?t assume.:bow1:

 

[Poacher]

Had a similar problem with a riding friend. He runs a triumph Cali and had a skinny front on and we wouls alway have a go at him for being too slow; his reply was that he would not go over the posted limit - 70mph.

Anyhoo he changed his tyres for a different make - as you did - and suddenly he's away in the distance, doing 73mph [gps] on the motorways. he was amazed at the difference - so were we. He aplogised for being a prat too which was nice.

p

 

[Throttlejockey]

This is a one of the reasons I use my GPS exclusively as a speedometer. I don't even bother looking at the one on the bike.

 

[Slasher]

This is a one of the reasons I use my GPS exclusively as a speedometer. I don't even bother looking at the one on the bike.

I also do this. It's easier to see being right in my line of sight on the dash, and extremely accurate!

 

[970mike]

Well I am sure the tires did not make any difference to the stock speedometer and fuel mileage, as I have run several brands and sizes of tires on the ST with no change. Not sure why yours would change, but the PD versions are right on the money.

 

[sennister]

On both my 1100 and 1300 I have seen the speedo error differ from time to time. Sometime it is really close sometimes way fast. It seems that temps seem to have something to do with it for me.

Though like others mentioned. I look at on of my Garmins more than the speedo on the dash.

 

[jvick98]

On both my 1100 and 1300 I have seen the speedo error differ from time to time. Sometime it is really close sometimes way fast. It seems that temps seem to have something to do with it for me.

Though like others mentioned. I look at one of my Garmins more than the speedo on the dash.

I have often noticed the speedo being different from the GPS by different values but just assigned it to something I didn't understand. Don't use the speedo anyway so it doesn't matter.

Jim

 

[sennister]

I have often noticed the speedo being different from the GPS by different values but just assigned it to something I didn't understand. Don't use the speedo anyway so it doesn't matter.

Jim

Does it seem more accurate in colder weather than warmer? That is what I seem to notice.

 

[ElmonteRon]

I guess my "assumption" is that the tires i took off were just about down to the skin and theses new one having a nice deep tread have a different outer circumference which would affect the speedometer accuracy. As for overall MPG, i too doubt that the tires would have that big of an affect either...other than now i'll be doing something closer to the posted speed limit rather than zipping around at some 10 or more over the limit.

thanks all for the thoughts and insights...

The bags, well they were ejected at the time of impact. The Left bag...I was able to plastic weld (youtube trick) it back together, looks awful from underneath but it will work for now. Had to purchase the body/bucket from the local dealer (shameless plug hondabike.com, saved me $100+ over list, free shipping and still picked it up at his store...thanks). Just need to get the hardware off the old and onto the new. The right bag is just all banged up but in tact and NOT cracked...thinking about spraying the lid with truck bed liner...anyone try that? if so got any pictures? the rear fender was busted to i bobbed it and of course the right engine guard got tossed. oh and most importantly, I bounced: not a scratch. I was very lucky.

The real bummer here though, being in the great State of Washington were it is MANDATORY to have vehicle insurance, my assailant didn't-of course. on the up side thought, small claims court appears to have worked. I won and the person has actually paid me some money to date...more than i ever thought i would see.

anyway, sorry to ramble, it's still a rather sore subject to me.

laters all and enjoy!

 

[Firstpeke]

Okay guys, the difference in rolling circumference between new and worn out is less than 2%, do the math....

For a brand new Michelin Pilot Road 3 for example on a 17/60R17 new it is 650 millimetre (mm) of which 6mm is tread pattern depth.

This gives 788.1 revs per mile for new and 802.9 revs per mile when down to 0mm remaining. A difference of under 2%. (1.88%)

So your bike speedo with a gearbox pick off for speed would read less than 2% different between new and worn out.

70mph would give about 1.4 mph difference between new and worn out tyres.

Front tyres, for those bikes with speedo drive on the front, produce even less error as the original tread pattern depth on fronts is usually about half of the rear when new.
For example the Michelin PR3 is 4mm original tread pattern depth when new, 2mm less than the rear for the ST1300, So the error would be 66% of the gearbox driven speedo.

HTH

 

[Poacher]

Front tyres, for those bikes with speedo drive on the front, produce even less error as the original tread pattern depth on fronts is usually about half of the rear when new.

Yes, your figures are quite correct but miss the point [sorry]

I think the problem is the profile of the tyre not the tread depth. No sure about the OP's tyre but in the case I stated there was a fair difference between the two tryes and this cause the variation in speed/speedo - in this case around 7-9mph. The difference was very marked after the change.

Hope this confuses the thread further ????

p

 

[sennister]

I guess my "assumption" is that the tires i took off were just about down to the skin and theses new one having a nice deep tread have a different outer circumference which would affect the speedometer accuracy. As for overall MPG, i too doubt that the tires would have that big of an affect either...other than now i'll be doing something closer to the posted speed limit rather than zipping around at some 10 or more over the limit.

thanks all for the thoughts and insights...

The bags, well they were ejected at the time of impact. The Left bag...I was able to plastic weld (youtube trick) it back together, looks awful from underneath but it will work for now. Had to purchase the body/bucket from the local dealer (shameless plug hondabike.com, saved me $100+ over list, free shipping and still picked it up at his store...thanks). Just need to get the hardware off the old and onto the new. The right bag is just all banged up but in tact and NOT cracked...thinking about spraying the lid with truck bed liner...anyone try that? if so got any pictures? the rear fender was busted to i bobbed it and of course the right engine guard got tossed. oh and most importantly, I bounced: not a scratch. I was very lucky.

The real bummer here though, being in the great State of Washington were it is MANDATORY to have vehicle insurance, my assailant didn't-of course. on the up side thought, small claims court appears to have worked. I won and the person has actually paid me some money to date...more than i ever thought i would see.

anyway, sorry to ramble, it's still a rather sore subject to me.

laters all and enjoy!

Should have taken him/her to a Judge Judy type show. The person who is awarded a judgement gets paid by the show not the person that lost. So you would get the full amount awarded right away. It is my understanding that all the TV judge shows work like this.

 

[Firstpeke]

@Poacher, to get a large difference in speed with a different profile in the magnitude of 10mph would require a diameter difference of some significance, profile makes quite a small difference as it is running on the same rim.
If you were able to fit a 190/55R17 rear, on the same rim (which you can't) the difference in diameter is only 6mm, making next to no difference in the revs per mile, half the error previously mentioned...... cumulatively if running a worn out 170/60 and fitting a new 190/55, then the difference in diameter could be 18mm, which may make as much as 2.1mph difference in the speed indicated....

I have been through this many times with people claiming tyres make huge differences in speed...... the standard ST1300 speedo error is up to 10% high at higher speed ranges.... never does a speedometer on a vehicle indicate low against actual speed, this would be outside type approval or some other such legal requirement.
If it says 30 you must be doing 30 or less in real time, if there is a condition where your calibrated speed is more than indicated then you have a faulty speedometer, assuming the tyres fitted are within all possible options permitted by the manufacturer....

When I worked for a company supplying video speed enforcement systems to the Police all over Europe and in Hong Kong, as well as having some connections to Stalker in the USA, I used to train traffic officers in the use of the systems.....
I also used to work for Michelin and provided technical information to vehicle dealers and truck manufacturers as well as assisting in the specification of tyres for new bespoke build vehicles for special use....

I do understand where you are coming from but still believe that folk try to attribute to tyres things which they are not responsible for..... including failure.....

People more often than not, underestimate their tyres in the dry, and overestimate them in the wet.... never mind what the guys in the USA call hydroplaning (aquaplaning here).... or even viscoplaning.... then there is the oft misquoted "slip" angle..... but that's another thread entirely.....

 

[ElmonteRon]

well gee, when you say it like that...i feel kinda silly mentioning it. The tire may be slightly different from the prior tire, but surely not an inch or more...perhaps it's mechanical or an electrical issue (however the bike determines the speed) At any rate the fact is that when i first got the bike the speedo was a good 10mph off and now it's not. Guess it's just something that i'll have to spot check from time to time with the GPS to make sure that it's consistent.

again, thanks for all of input...

 

[Poacher]

Ok Ok Ok I'll rip my shirt and put ashes on my head and never bother you again

I love these guys who can take MINIMUM information and destroy a perfectly good anicdote.

1. the rider was a wimp and hated any speed over 20mph so always went at least 5mph slower than he claimed so as not want ing to be seen as a wimp.

2. it was on a 19" rim so your figurers are out and NO I don't care how far out they are - It's a story to add to the thread not a degree question

3.Later found that his speedo was reading 6% out across the board anyway - it failed an MOT and had to be replaced.

4. My speedo may or may not have had the STANDARD 3% varience as well .....

Are you getting the picture yet?

So here we have a possible [note - possible] 9% difference between my speedo and his PLUS your magic %% for profile difference - You do the mathe but only when you have all the facts .......

I added my original piece to add to the thread as an anicdote to the original poster not so you all could hav an inpromptue mathe binge. I'm truely sorry if you find my posts boorish/dull/insignificant and 'not one of your sort'. I'll try not to rain on your threads again.

To the Mods ......

This is a RANT 'cos I really find this sort of thing very bad for my carma. If you wish to delete it please feel free --- at this point in time I really don't care - Stuff 'em all

 

[ElmonteRon]

No NO NO...guys. this is my bad. I appreciate ALL of the comments. i was publicly flogging myself a bit. i'll put the cat-o-nine tails away. I was putting more weight on the tires going from old to new, or i should say in the over all change in circumference. didn't think it through well enough. that's all. I liked the discussion that came out of it. Really-it's all good.

 

[Firstpeke]

Sometimes trying to share knowledge can bring so much pain.......

Perhaps I should go back to ignoring tyre threads...... like Ken and Norm......

 

[SupraSabre]

This is a one of the reasons I use my GPS exclusively as a speedometer. I don't even bother looking at the one on the bike.

 

[ST Gui]

I don't bother using my GPS or nav app for speed. My speedometer is much bigger, and is 3mph fast at any speed, at least above 15mph or so. Given this, I don't ever need to know exactly how fast I'm going.

Since I observe speed limits, going by the speedometer keeps me legal. I use an app from time to time that tells me where speed cameras are and it has a digital speed indicator. It's nice for a change of pace, but not needed nor particularly superior.

I prefer the Maps app on iPhone while in cell range. When I'm in the wide open where there is no cell coverage, I'll use Navigon. It gives me my speed, but again, the speedo is superior.

Now if there were an HUD on the windscreen, that would be a different story. That would be wicked cool.