Preliminary New Tire Report

[cywelchjr]

Ok, I wimped out and took the new Kenda tire down to the local bike shop and had them mount and balance it, cost me $28 and took less than 1/2 hour, I figure if I had attempted to do it myself it would have taken me more than an hour and a lot of back pain.

So, new tire on, looks good, but of course it needs broken in (about 100 miles according to Kenda). So, I headed out on a partial break-in ride. Put about 54 miles on the tire in about 1.5 hours of country road driving. The tire seems to handle pretty well, smooth, decent grip (although I'm not pusing it yet, and certainly not trying to get rid of the chicken strips yet), but this was a lot of twisty and semi-goat riding. It seems to be scuffing in pretty well so far, and doesn't seem to follow cracks and crevices in the road (always a concern with a new tire brand). We'll see how it wears over the next 6 months, and I'll be putting the same brand and model on the back in about 2 weeks and I'll take it on a similar break-in ride.

Another thing I found is that after about 1.5 hours in the saddle my seat was still pretty comfy, so I guess my slightly strange lookiing not quite stock seat is pretty comfortable.

[Crazcnuk]

At an average of 36mph i don't think it counts as break-in miles!

[barberad]

Not a threadjack but...

I put some Pirrelli Route MT 66's on the bike about four weeks ago and I've no complaints. Both tires were less than $140 from supercycle.com (free shipping). Cornering is good and the grab feels a lot better than the bald Dunlops. The lack of having tires on the bike is why I've been absent for so long. Good to be back on 2 wheels.

[fredintoon]

At an average of 36mph i don't think it counts as break-in miles!

Hi Craz,
depends on the roads you average the speeds on, dunnit?
Many years ago you could drive your road car around Germany's Nurburgring race track.
Buddy tried it in his English Ford. Screamed the tires, howled the brakes and gearshifted like a bastard on every corner.
Finished the course white-faced and shaking.
Averaged 18 MPH.

[Larrym]

Kendo tire data

The weather cleared up so I took a ride on my bike and collected some data.

Front tire: Kenda Challenger 100/90-19
Rear Tire : Kenda Challenger 130/90-16

Speedo__________GPS__________Error
MPH........................MPH..................MP H
15________________10.2____________4.8
20________________14.6____________5.4
25________________18.4____________6.6
30________________22.7____________7.3
35________________27.6____________7.4
40________________32.5____________7.5
45________________37.0____________8.0
50________________40.8____________9.2
55________________45.6____________9.4
60________________50.3____________9.7
65________________55.1____________9.9
70________________59.8___________10.2
75________________64.5___________10.5

GPS was a GARMIN GPS-48.

I made 4 separate runs and averaged the figures. (Used a digital voice recorder to log data as it was happening.)

It appears that whatever speed the bike indicates is faster than what is really happening in the real world. It is also clear that the offset/error between the speedo/real world is not constant at all speeds. Drat! I was hoping I could just add or subtract a fixed amount and be good to go.

Unclear is whether the difference between the GPS and the speedo is due to the front tire size or is due to 30 year old speedometer. Also unclear whether this offset/error applies to odometer and would make my gas mileage figures inaccurate. (44 Mpg...)

[DiverRay]

Speedo error is probably age related. Special Ed's speedo is off by close to the same amount. My Standard is close to real, as is the midnight. They BOTH have "low mileage" speedos, Special Ed's has over 104K on it.

[Larrym]

Trust issues

Ray,
That sounds about right. cywelchjr had another thread where he was concerned about whether the new Kendo would throw off his speedo. I had the Kendo on my bike so I hoped that this data would be helpful.

I put oversize tires on my truck and the speedo offset/error was about 4mph in top gear. I verified it with a GPS and the offset didn't vary like it did with the bike.

Looks like I can't trust my speedo, add a fixed amount to the value, or adjust it to read accurately.

THX.

[cywelchjr]

At an average of 36mph i don't think it counts as break-in miles!

The road taken is/was pretty goat and quite curvey. As a matter of fact it's a levee road, which while quite scenic is actually pretty challenging technically. Mostly 25 MPH corners (which I took at a good bit higher speeds) and more than a few whoopties. Was fun and scenic.

[Bigfoot]

My speedo is just the opposite. If it says I am doing 70 on my speedo, gps shows that I am actually doing around 78.

[jeffe]

I installed a Cateye 8 digital bike speedo. Calibrated it according to the instructions. Checked on a measured mile...was spot on. Love it. Only problem is it does not light up at night...but working on it.

[Ivan]

It appears that whatever speed the bike indicates is faster than what is really happening in the real world. It is also clear that the offset/error between the speedo/real world is not constant at all speeds. Drat! I was hoping I could just add or subtract a fixed amount and be good to go.

Speedo errors are generally in percentages. From your data, your speedo is about 15% fast.

If you can get a strip of road about 10 miles long, and watch the difference between the mile marker and your odometer, you will come to a different error. My speedo is off by about the same as yours, but my odo is off by less than 1%. In this case, the odo says the tire is OK, since the right number of revs per mile are being shown, but the spring on the needle is getting weak and letting the needle move farther than should be.

[cywelchjr]

Didn't I see somewhere that there is supposed to be a way to adjust that? Something about adjusting the spacing between the rotating assy and the needle?

[Ivan]

Didn't I see somewhere that there is supposed to be a way to adjust that? Something about adjusting the spacing between the rotating assy and the needle?

Most older auto speedos did have a small adjustment screw on them. I am unsure of the XS, since it is sealed and I really don't want to destroy mine trying to get it opened up to see. If I ever come across one that is un usable for some reason, I will open it up and see.

[Larrym]

Don't look down!!

Ivan,

"Speedo errors are generally in percentages. From your data, your speedo is about 15% fast."

Yup! That's about the size of it. Percentages. I just wanted to be able to apply some simple addition or subtraction as I glance down at the device. You're talking about doing multiplication in my head while comparing the posted speed limit and what the speedo is telling me. The "enjoyment factor" of riding my bike would take a huge nose dive.....

"Not gonna duit!!"

I prob'ly will do a ten mile run and compare the odom with the GPS. I mean the front wheel rotations being counted is the way the odom works and the showing the speed of those rotations is the way the speedo section works. Right?

[BigDick]

Most older auto speedos did have a small adjustment screw on them. I am unsure of the XS, since it is sealed and I really don't want to destroy mine trying to get it opened up to see. If I ever come across one that is un usable for some reason, I will open it up and see.

I have the stock 85 mph speedo from my bike we could use.