4LO - rough idea on revs and speedo readings.

[earthman]

On a standard 350LC, anyone know what the speedo should read at X revs whilst in X gear?

[Deleted]

y

[JonW]

surely X revs in Y gear = Z mph?

[Deleted]

TBH it’s a six speed gearbox it redlines probably somewhere in the region of 9000rpm

If you want every 1000 rpm in each of the gears that’s 54 different speeds, double that for every 500 rpm, quadruple for every 250 rpm

Try writing them all down whilst riding, it won’t be easy, or you have to stop at least 54 times and memorise what your speed was in that gear at the revs chosen

I guess you could work it out mathematically, the crank turns once every 0.06 seconds at 1000 rpm, look at the crank gear ratio that drives the gearbox (thats the gear cog at the end of the crank), factor in each of the 6 gear ratios to see how fast they will turn at 1000 rpm, multiply by the final drive ratio, which will vary with what drive cogs you are using front and rear, do that 54 times from 1000 to 9000 rpm and you’ll have your answer

Easy as pie or should that be Pi

Much too complicated for me though

[Deleted]

5th gear 1000rpm for every 10mph Ish
5th gear 6000rpm = 70mph ish

[earthman]

Apr 27, 2018 7:49:26 GMT 1 @hblair said:

TBH it’s a six speed gearbox it redlines probably somewhere in the region of 9000rpm

If you want every 1000 rpm in each of the gears that’s 54 different speeds, double that for every 500 rpm, quadruple for every 250 rpm

Try writing them all down whilst riding, it won’t be easy, or you have to stop at least 54 times and memorise what your speed was in that gear at the revs chosen

I guess you could work it out mathematically, the crank turns once every 0.06 seconds at 1000 rpm, look at the crank gear ratio that drives the gearbox (thats the gear cog at the end of the crank), factor in each of the 6 gear ratios to see how fast they will turn at 1000 rpm, multiply by the final drive ratio, which will vary with what drive cogs you are using front and rear, do that 54 times from 1000 to 9000 rpm and you’ll have your answer

Easy as pie or should that be Pi

Much too complicated for me though

Thanks, best reply so far but that's way to complicated for me too. Lol

I were thinking of one or two figures only, for example, cruising at 6000 revs in top gear on a flat road generally gives X mph on the speedo.

[Deleted]

In top gear off the top of my head and in KM's.
At 4000rpm I'm doing approx 80 kmph. At 5000 rpm i'm doing approx 100 k's.

[Deleted]

Sorry, I'll change it abit. I must of been in fifth gear.
So today in top gear at 4000 RPM , is was doing 88kmph .
So close to 50mph and thats with standard gearing .

[bare]

Small Factiod I've tripped over in the past:
Yama Tachos are erm 'incorrect'... weren't great brand new, Decades on they can be laughably off (seen 1500 rpms error on one of mine).
Ditto for the Speedo
Insert a digital Spark pulse/rmp readout and using your Phone's GPS readout (tape the phone to the Tank?)
then see what is Actually happening and at what Real road speed.

[earthman]

Good points there Bare.

[Deleted]

I cant say how accurate the tacho is on my bike but I believe the speedo is pretty close.
Around here they have LED signs that flash up your speed if you are going over the speed limit and if your under it a green smiley face.
Whenever I come across one I give it a little throttle to wipe the smile of its face and my speed comes up in red .
Its always spot on with all the different ones Ive come across.

[earthman]

Apr 30, 2018 1:29:51 GMT 1 @ken007 said:

I cant say how accurate the tacho is on my bike but I believe the speedo is pretty close.
Around here they have LED signs that flash up your speed if you are going over the speed limit and if your under it a green smiley face.
Whenever I come across one I give it a little throttle to wipe the smile of its face and my speed comes up in red .
Its always spot on with all the different ones Ive come across.

That's a good tip.