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My Brand new KLR, RPM is different.

5K views 26 replies 13 participants last post by  timberfoot 
#1 ·
Hello all

My insurer has replaced my 2017 KLR with a brand new 2018 KLR after a car ran into me about a month ago.

I have included a picture of each. The photos are taken at the same local locale. Each photo is taken on the first weekend I owned each bike.

Anyway, I have a question for the experienced and knowledgeable members.

I'll preface the question with an explanation. My old bike, which had done about 24000 miles sat on about 3100 rpm at 37 mph. The new bike, which has done about 80 miles sits on about 3020 rpm to maintain the same speed.

I did have a feeling the old bike was doing slightly more rpm to maintain that speed, but I convinced myself that I was being paranoid.

So, my question is; why did my old bike do more rpm to maintain the same speed.

I welcome any thoughts or advice

Thanks guys
 

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#5 ·
Hello all
.

I'll preface the question with an explanation. My old bike, which had done about 24000 miles sat on about 3100 rpm at 37 mph. The new bike, which has done about 80 miles sits on about 3020 rpm to maintain the same speed.

So, my question is; why did my old bike do more rpm to maintain the same speed.

I welcome any thoughts or advice.

Thanks guys

Thanks for accepting thoughts or advice. I have more thoughts than advice these days.

So my thought is - global warming. Ya, the air temperature is warmer, which makes your bike run better, at lower rpm and using less fuel to do it. :grin2:

.
 
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#13 ·
Agree with previous analysis a few posts above: Possible cumulative error, additive from inaccurate/imprecise speedometer and/or tachometer. GPS receiver useful for calibrating speedometer.

Tachometer? Some clip-on/wrap-around digital instruments, affordable and available, may yield more accurate measurements.

But . . . the relationship between rpm and mph remains what it is (aside from some minimal tire circumference variations with wear/temperature/etc. changes); knowing the relationship precisely doesn't change it!

:)
 
#14 ·
Thanks for all your replies, guys.

As I said, I do welcome all thoughts and advice, no matter how strange....you know who you are!

But, thanks guys. Variance in the gauges seems to be very reasonable explanation.
 
#17 ·
That is not very much difference and your 2017 could not possibly have sat on a specific rpm at a specific speed for 24000 miles unless your 2017 speedometer or tachometer is defective or you change both tires every couple hundred miles. You probably just did not notice. Tach measures rear wheel speed and speedo measures front wheel speed. The rear tire wears faster than the front. The rear gets smaller relative to the front as they wear and turns faster, so rpms at a set speed go up as a tires wear, like 5-10% depending on how diligent you are about changing tires. Your talking under 3%, your 2018 is fine. Sleep well tonight.
 
#18 ·
Tach measures rear wheel speed and speedo measures front wheel speed. The rear tire wears faster than the front. The rear gets smaller relative to the front as they wear and turns faster, so rpms at a set speed go up as a tires wear, like 5-10% depending on how diligent you are about changing tires. Your talking under 3%, your 2018 is fine.
kwarbington, while I agree with you regarding small variations in tire dimensions through wear are of little or no consequence . . . I don't think the tachometer is driven by the rear wheel. Rather, I think the tachometer measures engine rpm independent of front or rear tire rotation, even when the bike is parked and the rear tire stationary. YMMV!

:)
 
#22 ·
Hello guys

It is true that the tacho is not driven by the rear wheel, but the rear wheel is driven by the engine. A small rear wheel would have to rotate faster than a larger wheel to maintain the same speed, So the engine's RPM would be greater with a smaller rear wheel.

How much difference can tyre tread make? What is the difference between the depth of a new tyre and the depth of a tyre due for replacement? 4/5ths of and inch? How much difference would that make to the RPM of a KLR with standard gearing? That is a question for someone more intelligent than I. I know some of the guys on this forum love that stuff.....
 
#23 ·
Pi times twice the difference in tread depth gives the difference in tire circumference. (TWICE, because the formula for circumference is Pi times diameter; the difference in tread depth applies to radius, 1/2 diameter).

Previous circumference, divided by worn circumference, gives percentage increase in rpm at any given speed.

A similar problem WILL be on your final exam.

:)
 
#25 ·
I think it's because the rear tire is bigger on the newer bike. If you look at how the tire lines up with the black and orange sticker on the swingarm, you'll see that it's different.
I think that is mostly camera angle.

But I'll ask if those are the Australian OEM Kawasaki Tires? They sure aren't the Dunlop K750's that USA recieved from 1987 to 2018!

Those tires look quite good, maybe 60% highway / 40% dirt?

What Brand & Model of tires are those? What average KM or Mi do riders get out of them?
 
#27 · (Edited)
Hello Paul

The tyres are Dunlop Trailmax. They are the same as the factory tyres on my old bike.

From memory, I reckon that Dunlop do claim them to be about 60/40 road/trail

I got a tad over 6500km out of them on my old bike. To be honest, they were well due for a change by then, but still legal.

My riding style seems to make be fairly easy on tyres. The size of the rim has not changed at all.

Cheers guys
 
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