M1100 gearing ?

[Italiatwin]

Hi all

I got my M1100 a couple of days ago and I love it.
I have some queries regarding gearing.
My bike shows about 78/80mph at 4000rpm in 6th.
Is that standard gearing ?
What are the standard sprocket sizes ?
It seems to be reading faster on the speedo than it is acctually going, but maybe that's my imagination ?
Tyre sizes are standard.

Cheers 😀

[Italiatwin]

I've just been on Gearing commander and with standard 15/39 gearing it shows 71mph at 4000rpm.
To get 80mph at 4000rpm it needs 16/37.
This doesn't seem right, surely with that long gearing the bloody thing would hardly pull away ? But my bike pulls like a train.
Any thoughts ?

[Mr Gazza]

The speedo reads speed from wheel revolutions and has nothing to do with drive train gearing.

If you have the standard wheel sizes and the recommended tyre profile then the speedo should be accurate.

The only way to tell what sprockets you have is to count the teeth.

[Italiatwin]

Yeah ok, so I think I'll have to check the speedo readings against a sat nav and count me teeth.

[Darren69]

My S4 has standard 15/39 final gearing and I'm pretty sure from memory that 4000 would see close to 80mph, although the S models had a close ratio box I think the first and 6th gear were the same. Its been a while since I rode on the autobahn where you can use 6th gear on the thing I can't remember. and I don't know if they changed the gearbox ratios on the later bikes.

You've not got some clutch slip issues, maybe?

[Darren69]

I did have a lengthy message ready but it crashed so I lost it. anyway I have found those radar speed signs that flash up your speed in 30 zones to be a useful way to check speedo accuracy and have found them to be pretty close within +/- 1 or 2 mph.

[SunEye]

According to the owner's manual the speedo on the M1100 overreads by 8%. So an indicated 78-80mph is actually 72-74mph. So I suspect that you have standard gearing, which is 15/39.

[Italiatwin]

So I have counted my teeth and I am running 14/39.
My bike is showing 80 at 4000 revs, gearing commander says 67 at 4000 revs with the 14 tooth engine sprocket. Even with the 8% over read it should be saying about 73.
My speedo seems to be approximately 20% to fast. I am going to check this against my satnav throughout the speed ranges today.
Have any of you experienced this extremely optimistic speed reading ?
Did it result in new clocks required ?

[Darkness]

The speedo reads speed from wheel revolutions and has nothing to do with drive train gearing.

If you have the standard wheel sizes and the recommended tyre profile then the speedo should be accurate.

The only way to tell what sprockets you have is to count the teeth.

Have you confirmed that the speed is taken from wheel rotations like Mr Gazza says, as if it is, the speed you are doing is proportional to the rolling diameter of the wheel?

There will still be a fixed relationship between engine revs and road speed, based on the gear ratios fitted, but why do you think the Rev counter is right and the speedo wrong?

[Italiatwin]

I now know the Speedo is rather optimistic because I went out with the satnav bolted on yesterday
Unfortunately the battery on my phone went flat before I got to the dual carriage way but I did establish that the clock is about 7/8% fast at 30 and around 10% fast at 50.
I am assuming that the increase in inaccurate readings will continue rising as the speed gets higher, next time I have a dry day and a full battery on my phone I will look at the higher speeds.