Why are RPMs shown rather than torque?

**IdunBrokdItAgin** · 28th November 2010, 00:04

May sound like a damn silly question on it's own but the real question is why do both cars and bikes show RPMs as a read-out as opposed to torque?

Most lay people, such as myself, look to RPM as an indicator of "fast" (as in higher means "faster" in both terms of acceleration and cruising speed - when gear ratio taken into account). However, having just read a thread from another forum of optimum places to change up (in RPM terms) it seems to strongly allude that change up points are best selected for the points where torque is strongest (calculated both in the current gear and the next gear).

So, if acceleration is best judged by torque, why do bikes/ cars not have a torque read-out (either in addition to, or instead of, RPMs)?

Are bikes and cars just working on old technology instrumentation read-outs? And, if a dyno machine can measure torque at any point, why can't a modern automobile?

Lots of questions but I am genuinely interested in the reason behind why torque is not displayed.

**ellipsis** · 28th November 2010, 01:27

....just ride it mate...

**davebullet** · 28th November 2010, 05:28

G'day mate.

Probably no technical reason. I'm sure there are physics equations and means for a bike to measure the mass load, subtracted from an ideal zero load and you have torque available.

I suppose revs are there first and foremost to stop you blowing up the engine. Then rev limiters came along with ECUs and largely prevented the rider from doing that (except at cold).

Maybe it's do with dials and linear gauges. I mean revs are linear and bike independent. You can hop from one machine to the next and get the same readout.

A torque calculation / tacho system might be too susceptible to people modding their bikes. Different exhausts, fueling and cams etc... change the torque curve.

Having said that the Bugatti Veyron reads out HP.

I suppose most people just find an already taken dyno of their bike and identify the rev range where the max torque is.

And finally.... we ride triples which basically mean you have max torque all the time, so would be redundant

**nadroj** · 28th November 2010, 07:30

I have a torque meter on my bike - it's called a bum-ometer!

**Cloggy** · 28th November 2010, 07:46

Not a silly question at all. I agree with you, it would be nice if both car and bike manufacturers could include where the engine's optimum operating range is on the rev counter. I've seen this on some trucks.
Also agree with Dave, one of the reasons I bought my Triple is for the very reason they start making torque down low in the rpm range. You don't need the rev the snot out of it to get it to move. Although taking it to the redline is a lot of fun as well.

**Owl** · 28th November 2010, 07:48

RPM - Visual aid for deaf people, cause deaf people can't torque

Sorry, but on a serious note, have you ever seen a deaf person driving a manual without a rev-counter

**marty** · 28th November 2010, 08:32

I always thought the speedo was the fast indicator. And the fact that the dashed white lines on the road have turned to a solid one, and lamposts look like fence posts.

**Bass** · 28th November 2010, 08:37

Indicating RPM is relatively straightforward and inexpensive. Torque output however depends on: -
RPM
Throttle setting
Fuel type and purity
Air temperature
Engine temperature
Air humidity
plug condition
etc
etc

I have seen it done using a load cell in the drive line which actually measured the torque rather than calculating it. However it involved slip rings which all but negated the value of the exercise because the load cell ouput is in millivolts and so the slightest bit of crap on the slip rings screws up the signal.

**puddy** · 28th November 2010, 08:42

Originally Posted by wild_weston

May sound like a damn silly question on it's own but the real question is why do both cars and bikes show RPMs as a read-out as opposed to torque?

Most lay people, such as myself, look to RPM as an indicator of "fast" (as in higher means "faster" in both terms of acceleration and cruising speed - when gear ratio taken into account). However, having just read a thread from another forum of optimum places to change up (in RPM terms) it seems to strongly allude that change up points are best selected for the points where torque is strongest (calculated both in the current gear and the next gear).

So, if acceleration is best judged by torque, why do bikes/ cars not have a torque read-out (either in addition to, or instead of, RPMs)?

Are bikes and cars just working on old technology instrumentation read-outs? And, if a dyno machine can measure torque at any point, why can't a modern automobile?

Lots of questions but I am genuinely interested in the reason behind why torque is not displayed.

The boy racers just can't squeeze in another gauge!

**Shadows** · 28th November 2010, 08:50

All I want to know how fast my wheels are turning and how fast my crank is spinning.

The seat of my pants takes care of the rest while I concentrate on the shit unfolding in front of me.

**Crasherfromwayback** · 28th November 2010, 09:24

can be used as another speedo. You don't need a torque read out...you can feel it through your bum cheeks!

**IdunBrokdItAgin** · 28th November 2010, 11:06

Thanks for the replies.

So it sounds like it is theoretically possible, for an automobile, to calculate its torque - however there are many variables and modern technology wouldn't be accurate enough to accommodate all of them.

Interesting - I reckon the person who designs a practical working solution would make a fortune - won't be me though as I am just not that clever.

**SMOKEU** · 28th November 2010, 11:40

A torque gauge will be of little use as you just have to know where in the rev range the peak torque is developed, and drive/ride by the tacho, shifting just under the redline for maximum straight line acceleration.

If you're in a cage towing a heavy trailer then it's a good idea to keep as close to the maximum torque RPM as possible.

**hayd3n** · 28th November 2010, 11:42

Originally Posted by SMOKEU

A torque gauge will be of little use as you just have to know where in the rev range the peak torque is developed, and drive/ride by the tacho, shifting just under the redline for maximum straight line acceleration.

If you're in a cage towing a heavy trailer then it's a good idea to keep as close to the maximum torque RPM as possible.

you'll actually find the bike faster if you know when to change gear its not necessarily just before the red line