mathematically challenged

[dJames]

I have an 2004 RT-P and was wondering, since the RT-P has a 31:11 final gear drive and the civilian has a 32:11 final drive, does that mean the the RT-P is running at a higher or lower RPM on the freeway than the civilian model?

Thanks for the help.

[outpost22]

I have an 2004 RT-P and was wondering, since the RT-P has a 31:11 final gear drive and the civilian has a 32:11 final drive, does that mean the the RT-P is running at a higher or lower RPM on the freeway than the civilian model?

Thanks for the help.

 

It depends if the lights and siren are on

[OoPEZoO]

The RT-P would have lower RPM at a given speed versus a standard RT.

 

The RT-P gets a higher theoretical top speed with trade off of slower acceleration.

[dJames]

The RT-P would have lower RPM at a given speed versus a standard RT.

 

The RT-P gets a higher theoretical top speed with trade off of slower acceleration.

Ok thanks.

[EffBee]

The RT-P would have lower RPM at a given speed versus a standard RT.

 

The RT-P gets a higher theoretical top speed with trade off of slower acceleration.

 

Are you sure, Keith? You're not taking into account that the RT-P is probably trying to catch the civilian RT and is therefore running at higher rpm.

[upflying]

The RT-P would have lower RPM at a given speed versus a standard RT.

 

The RT-P gets a higher theoretical top speed with trade off of slower acceleration.

 

Are you sure, Keith? You're not taking into account that the RT-P is probably trying to catch the civilian RT and is therefore running at higher rpm.

I concur, mine runs a higher RPM at a given speed than a civilian version. Cop bikes priority is acceleration not top speed.

[Quinn]

I was told by the service head at my dealers (we were talking to a motocop) that the RTP was geared lower for faster accelleration and would run to a higher top speed. The RT was geared so tall that it wouldn't pull in 6th gear; the RTP would pull at lot better and could make full use of 6th gear to obtain higher speed against the wind resistence created.

 

----

 

 

[Alfred02]

If it's in the final drive then adding teeth on the larger ring gear will lower the speed.

Simple example to understand it, is to picture it in your mind like this:

"It takes ONE MORE Tooth to complete a full revolution".

[Huzband]

Think of it as adding a larger rear sprocket to a chain driven bike. Better off the bottom, but higher rpm at any given speed. Which is exactly why I want a GS fd for my RT.

[realshelby]

I have an 2004 RT-P and was wondering, since the RT-P has a 31:11 final gear drive and the civilian has a 32:11 final drive, does that mean the the RT-P is running at a higher or lower RPM on the freeway than the civilian model?

Thanks for the help.

 

The correct way to say this is: IF the rear tire is the same diameter the RTP drive shaft is turning slower than the RT driveshaft. The RTP ratio is 2.82 turns of the driveshaft for one turn of the wheel, the RT driveshaft turns 2.91 times for every revolution of the wheel. This has no guarantee of engine rpm being higher or lower. That is because the transmission ratios can be different. I think I have heard the RTP has a lower 1st gear? Maybe other ratios are changed also? That would effect engine rpm when comparing the two models.

[Guest Kakugo]

Related question. Does anyone know if there's a ready-made solution to lower just the first gear?

Sooner or later the gearbox will have to come off to change the clutch and I will be able to do the job then.

Not interested in lowering gear as a whole (cough... fuel consumption... cough) so the RT-P final gear won't do it for me.

 

Thanks.

[EffBee]

The RT-P would have lower RPM at a given speed versus a standard RT.

 

The RT-P gets a higher theoretical top speed with trade off of slower acceleration.

 

Are you sure, Keith? You're not taking into account that the RT-P is probably trying to catch the civilian RT and is therefore running at higher rpm.

 

Y'all do know that I was pulling on Keith's leg a little, doncha?

[Huzband]

Related question. Does anyone know if there's a ready-made solution to lower just the first gear?

Sooner or later the gearbox will have to come off to change the clutch and I will be able to do the job then.

Not interested in lowering gear as a whole (cough... fuel consumption... cough) so the RT-P final gear won't do it for me.

 

Thanks.

 

I know the R12GS ADV has a lower first gear than the standard GS, but I don't know if that applies to the 1150 GS/vs Adv. You'd have to check part numbers on the individual transmission fich.

[dJames]

I have an 2004 RT-P and was wondering, since the RT-P has a 31:11 final gear drive and the civilian has a 32:11 final drive, does that mean the the RT-P is running at a higher or lower RPM on the freeway than the civilian model?

Thanks for the help.

 

The correct way to say this is: IF the rear tire is the same diameter the RTP drive shaft is turning slower than the RT driveshaft. The RTP ratio is 2.82 turns of the driveshaft for one turn of the wheel, the RT driveshaft turns 2.91 times for every revolution of the wheel. This has no guarantee of engine rpm being higher or lower. That is because the transmission ratios can be different. I think I have heard the RTP has a lower 1st gear? Maybe other ratios are changed also? That would effect engine rpm when comparing the two models.

 

I have never ridden the civilian model, but my RTP has a ridiculously quick (high I guess?) first gear. More than a few mph and it is ready to be shifted. I was reading a topic on the RTP's and they did not mention anything other than the final drive being different, but who knows.

Typically you can gear something for quickness or top speed, but not both as you run out of RPM's (redline).

I was just curious if the rtp ran at a higher rpm at a given speed on the freeway than the normal one.

[OoPEZoO]

If the original posters info is correct about the final drive ratios he posted, then I am correct.

 

Its simple math, not voodoo magic.

[Eckhard Grohe]

In the original post it all depends if the first number is the the number of teeth on the ring gear and the second is the number on the pinion or if the first is number of revolutions of the pinion vs the number of revolutions of the ring gear. Once that is cleared up all will be clear.

[OoPEZoO]

In the original post it all depends if the first number is the the number of teeth on the ring gear and the second is the number on the pinion or if the first is number of revolutions of the pinion vs the number of revolutions of the ring gear. Once that is cleared up all will be clear.

 

You are correct, the numbers posted are the teeth count, NOT the final drive ratio.

 

31:11 = 2.82:1 ratio

32:11 = 2.91:1 ratio

 

But if the original poster is correct about the 31:11 gears being installed in the RTP, then it is still true that it has taller (slower accel, higher top speed) gears than the civilian model. According to the parts fiche for 1150 models........GS and GSA's got the 31:11 combo, and RT's got the 32:11 combo. That dosn't make sense to me, but its there in black and white.

[nldaniel]

Keep in mind that there are two variables here.

 

One is the final drive ratio, which, according to BMW is the shorter 32/11 for the RT and RT-P's alike.

 

The other is the gearbox, more specifically the ratio of top gear.

 

Civilian RT's and RS have a very tall (overdrive) 6th gear ratio, which lowers RPM on the freeway.

GS, R and rockster use a gearbox known as the sport or the enduro, which has a lower ratio on 6th gear.

 

RT-P's get the same gearbox as the 1150GS. (*)

 

Therefore a RT-P runs even higher RPM for a given speed then a GS. (due to the difference in the final drive, which is 33/11).

 

Even a 5-speed R1100RT runs lower RPM in top gear then an 1150RT-P.

 

To see the differences in the gearing go to Anton Largiaders website. He made a lovely tool that clarifys the differences.

http://www.largiader.com/articles/gearing/

 

HTH, Daniël

 

(*) BMW vehicle buildcode 35.9: fan, uprated alternator, wiring loom and sport-transmission.