Jump to content


Photo
- - - - -

Time For A Gearing Change ?


  • Please log in to reply
33 replies to this topic

#1 thelodger

thelodger

    Carpe fan

  • Member
  • Pip
  • 150 posts
  • Location:euxton
  • TDM model: 2010

Posted 07 May 2018 - 08:44 am

I am going to fit a new chain and sprocket . I haven't had my TDM 900 long but I did do a lot of miles over weekend and got the feeling that the bike would benefit from a change in the gearing so that it does more revs per mph .  This would help particularly in town riding when I seem to be in first most of the time and second would be better and also keep the revs out of the 3.5k to 4k zone more of the time.  I understand that standard gearing is 16 front and 42 rear . I am thinking of going 15 front . Has anyone else done this with positive results ?



#2 poppykle

poppykle

    really likes Carpe

  • Member
  • 83 posts
  • TDM model: 2010

Posted 07 May 2018 - 09:54 am

I dropped one tooth on the KLE when I had it and it made a world of difference particularly commuting around town. I'm thinking of doing the same when I change the chain and sprockets on my 900. The extra revs are no real disadvantage at highway speeds either. 



#3 Bjørge

Bjørge

    has been here 4ever

  • Supporting Member(thanks)
  • PipPipPipPipPipPipPipPip
  • 1,791 posts
  • Location:Asker, Norway
  • TDM model: no more

Posted 07 May 2018 - 11:08 am

Check out this: https://www.gearingcommander.com/ ... so that you don't make a mistake when choosing sprockets (espeically at the bottom of page - chain wear)


Bjørge

#4 Favs

Favs

    Sir Cumference

  • Supporting Member(thanks)
  • PipPipPipPipPipPipPipPip
  • 4,391 posts
  • Location:County Durham
  • TDM model: 2008

Posted 07 May 2018 - 12:23 pm

Not a hijack - anyone fitted a 39 teeth rear sprocket to a 9er? Wazzit like?

Ta.


Single-handedly reviving the Wave.

 

2008 reg. Black TDM 900 ABS

 

 

 


#5 Hombre

Hombre

    Carpe junky

  • Supporting Member(thanks)
  • PipPipPipPip
  • 448 posts
  • Location:Mallorca
  • TDM model: 2004

Posted 07 May 2018 - 09:19 pm

On a 9er, the speedo will be sensitive to the gearing.

Edited by Hombre, 07 May 2018 - 09:19 pm.

<p>BSA C15T, Ducati 200 Elite, Villiers Cub Trials Bitsa, Ariel Huntmaster, AJS 650 CSR, Sunbeam S7, Suzuki 650 Katana, Honda 400-4, Bultaco 350 Sherpa, Cotton Minarelli, Fantic 303, Yamaha SRX 400, Yamaha 550 Virago, Kawasaki ZZR 1100,  Fantic 305, Yamaha TDM 850 '91, Yamaha TDM 900 '04.  Ducati 200 Elite (again and now completed restoration), Yamaha SRX-600


#6 Kenyun

Kenyun

    sticking around

  • Member
  • 36 posts
  • Location:Staffordshire
  • TDM model: 2008

Posted 07 May 2018 - 10:15 pm

On a 9er, the speedo will be sensitive to the gearing.

 

Not if it has ABS.



#7 thelodger

thelodger

    Carpe fan

  • Member
  • Pip
  • 150 posts
  • Location:euxton
  • TDM model: 2010

Posted 08 May 2018 - 08:45 am

Mine's non-abs so any gearing change is going to affect the speedo reading. I'm guessing that standard speedo error is that it reads fast and if my thinking is correct then dropping a tooth on the front sprocket will make the speedo read even faster . I suppose this might affect my insurance if I have an accident but I would also want to know how fast I am going so for these reasons I am going to stick to standard gearing.



#8 fixitsan

fixitsan

    Carpe Citizen

  • Supporting Member(thanks)
  • PipPipPipPipPipPipPipPip
  • 4,667 posts
  • Location:West Lothian
  • TDM model: 2003

Posted 08 May 2018 - 09:05 am

Mine's non-abs so any gearing change is going to affect the speedo reading. I'm guessing that standard speedo error is that it reads fast and if my thinking is correct then dropping a tooth on the front sprocket will make the speedo read even faster . I suppose this might affect my insurance if I have an accident but I would also want to know how fast I am going so for these reasons I am going to stick to standard gearing.

 

 

I don't think it would affect insurance unless it over reads by more than the 10% the construction and use regulations allows for those earlier years. They've tightened up on it with later vehicles but I don't know the year off the top of my head. The regs state that a speedo must never under read. Also, the speedo is not an MOT item !


900 with better bits. Owes me nothing, Makes me smile


#9 thelodger

thelodger

    Carpe fan

  • Member
  • Pip
  • 150 posts
  • Location:euxton
  • TDM model: 2010

Posted 08 May 2018 - 09:09 am

Does anyone have a road test which shows the accuracy of the speedo ?


Edited by thelodger, 08 May 2018 - 09:54 am.


#10 CrashTestDuffy

CrashTestDuffy

    Carpe Regular

  • Member
  • Pip
  • 124 posts
  • Location:Fife
  • TDM model: 2009

Posted 08 May 2018 - 09:34 am

GPS app on phone on a motorway stretch should give a fairly accurate speed I think.

#11 fixitsan

fixitsan

    Carpe Citizen

  • Supporting Member(thanks)
  • PipPipPipPipPipPipPipPip
  • 4,667 posts
  • Location:West Lothian
  • TDM model: 2003

Posted 08 May 2018 - 10:24 am

GPS app on phone on a motorway stretch should give a fairly accurate speed I think.

 

+1  GPS on a straight and level road


900 with better bits. Owes me nothing, Makes me smile


#12 Hombre

Hombre

    Carpe junky

  • Supporting Member(thanks)
  • PipPipPipPip
  • 448 posts
  • Location:Mallorca
  • TDM model: 2004

Posted 08 May 2018 - 08:46 pm

My 9er speedo over-reads against GPS speed.

<p>BSA C15T, Ducati 200 Elite, Villiers Cub Trials Bitsa, Ariel Huntmaster, AJS 650 CSR, Sunbeam S7, Suzuki 650 Katana, Honda 400-4, Bultaco 350 Sherpa, Cotton Minarelli, Fantic 303, Yamaha SRX 400, Yamaha 550 Virago, Kawasaki ZZR 1100,  Fantic 305, Yamaha TDM 850 '91, Yamaha TDM 900 '04.  Ducati 200 Elite (again and now completed restoration), Yamaha SRX-600


#13 spike240

spike240

    really likes Carpe

  • Member
  • 91 posts
  • Location:Fylde Coast
  • TDM model: 2007

Posted 20 June 2018 - 07:16 am

Hi - reading through this thread, as sometime in future I am thinking of a 15 tooth front sprocket. A friend reckons it will make the 900 more useable. A couple of questions - someone said the speedo  error wouldn't affect the ABS models - why is this?

And Lodger -  did you end up swapping cogs? If so - what do you think? And where did you source the sprocket - oh and what make is it?

Many thanks.

PS The TDM is growing on me - I am learning how to ride it. :lol:



#14 Nog

Nog

    Knight of Postsalot

  • Member
  • PipPipPipPipPip
  • 512 posts
  • Location:Sarf East Innit
  • TDM model: 2007

Posted 20 June 2018 - 07:24 am

 A couple of questions - someone said the speedo  error wouldn't affect the ABS models - why is this?

 

 

Because on ABS bikes the speed is taken from the ABS sensor, which is on the wheels and so unaffected by gearing changes, since the gearing will be changed before the final reading (if that makes sense).  Only a change in wheel size would make a difference to that speed reading.

 

Normally they take the speed off the output shaft from the gearbox, which means any final gearing changes are after the speed is taken and therefore will mis-read,



#15 madmopedracer

madmopedracer

    Carpe junky

  • Member
  • PipPipPipPip
  • 473 posts
  • TDM model: 1993

Posted 20 June 2018 - 10:59 am

would the speedo reading be out by much just drooping 1 tooth on the sprocket

if you can the calibrate with gps for the important speeds 30,40,50 and 70 mph 



#16 Kenyun

Kenyun

    sticking around

  • Member
  • 36 posts
  • Location:Staffordshire
  • TDM model: 2008

Posted 20 June 2018 - 12:47 pm

I wouldn't be overly concerned about speedo readings, I haven't altered the gearing on my TDM900, but on my other bikes 1 tooth [extra] on the front sprocket alters the speedo reading by only about 2.5%.



#17 thelodger

thelodger

    Carpe fan

  • Member
  • Pip
  • 150 posts
  • Location:euxton
  • TDM model: 2010

Posted 20 June 2018 - 03:47 pm

I stuck with the standard size sprockets.  I think dropping a tooth on the gearbox sprocket is likely to make the speedo over read by at least 10% ). I reckon standard over read is  c5%  and then at least another 5% from the "one less tooth ".

 

I fitted Ognibene sprockets front and rear as they have rubber damping rings ( original Yamaha front had one  but not the rear ) .  Italian made and much better than the usual JT sprockets.  They also look cool and stupidly I like their name !!  Chain is  DID  VX525 gold X ring.

 

Cheers



#18 spike240

spike240

    really likes Carpe

  • Member
  • 91 posts
  • Location:Fylde Coast
  • TDM model: 2007

Posted 20 June 2018 - 08:22 pm

Ok thanks for the comments. Personally I am not too bothered about the speedo as mine is ABS, I also nearly always have gps in front of me and I can confirm the standard speedo set up is very optimistic.
Is anyone else using a 15 tooth sprocket?

#19 Bjørge

Bjørge

    has been here 4ever

  • Supporting Member(thanks)
  • PipPipPipPipPipPipPipPip
  • 1,791 posts
  • Location:Asker, Norway
  • TDM model: no more

Posted 21 June 2018 - 09:48 am

If standard sprocket is 16 teeth, then dropping to 15 would give (16/15) - 1 = 6.67% lower speed with same output shaft speed (also,.speedo reading)


Bjørge

#20 spike240

spike240

    really likes Carpe

  • Member
  • 91 posts
  • Location:Fylde Coast
  • TDM model: 2007

Posted 21 June 2018 - 12:36 pm

Hi and thanks. There is a link earlier in the thread to a site gearingcommander which is very very good. It does all the maths for you, but there's nothing like experiencing the change - if you know what I mean. Can't help thinking if  a 15 tooth sprocket was better than standard 16 then Yamaha would have done it. Having said that, my mate (mentioned earlier) is a dinosaur biker/racer/mechanic and reckons for the losses on top speed the bike will be more useable.

So for the cost of a sprocket I will try it (don't know when tho). When I have done it, and  road-tested it I will be sure to let you know.

atb




0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users