Gearing

[Maitland]

Hi all,
      finished mounting the 18 ins GSXR wheels and now need to replace chain and sprockets. Any ideas as to best sprocket ratio?

It's a 1200, standard motor and has a 34 tooth rear and guessing 16 tooth at the gearbox. I'm assuming this is a touring set up as the 1000 cc bikes have 40 - 17 or there about.
It will be used on the road but built and modified (ongoing) for the track. I'd be grateful for your thoughts on gearing to this end before I go knocking on Andy's door for chain and having the rear sprocket made to order. 

Maitland.

 

[Jota Rob]

Hi

Sounds like you have a big fat 630 Chain set up in there.
Suggest you throw that away, its no use for your bike 

You need to choose beteen 530 or 520, 530 if you're doing mostly road miles but if you're likely to suffer chain run problems, go 520 and accept it will wear quicker pro rata.

19/40 or 19/38 will do for starters, what will make more difference than anything is the tyre width and profile so its all speculative trying to guess which rear sprocket but either will be a good starting point.

YOu probably know but the 530 can be turned down to a 520 pitch, I grind it coz my lathe is only little and doesn't like it much.

Cheers Rob

 

[sfcpiet]

Maitland,

34/16 is the infamous #630 set-up.  Hopefully it's worn to the point you cannot use it any longer!

As Rob stated, 530 or 520 is up to you, a 520 or 530 o-ring would suit the road, a plain 520 is fine for track use.

You'll probably only find 19T #530 front sprockets, 18T were available for US bikes to keep the revs up and the battery charged, so changing ratios is limited to choosing the rear sprocket.  I run a 38 rear on my 3C, a bit of a pain in the alpine hairpins with the CR box, but if needs be, the change to 2nd. occurs at about 130kmh !  Works well accelerating out of la Source in Spa though  .

Recently fitted 19/42 to a nicely re-worked SFC1000.  Not so good if you're looking for all-out top speed, but a great choice for boosting low and mid range pick up!  Would be my first choice for a slow, twisty circuit.

Guess you'll need to try a couple of options to find out what best suits you.

piet

 

[Maitland]

Thanks for the info guys, 19/40 seems a good place to start, might get a 42 as well, most of our circuits are short and twisty

I plan to use a 140 section tyre on the rear and none 'O' ring chain, should fit with a few mm to spare, nothing outrageous at his point.

Rob, did you make Mallory practice day the other Friday? We didn't arrive until late in the day. I went mini moto racing with the CRMC, 6'2" on a 500! Elbows and knees all over the place

 

And feet as well rounding the hairpin   Hence the Laverda, a bit more room

Maitland.

 

[andychain]

Guys read the comments from OZ racing about the 520 versus the iwis light 530 !!!!!!!!!!!

106 links weighs in at 1.6kg.

I run the stuff on my Bandit and yet only the guys in OZ seem to trust it on Laverdas. Look at google Les Harris Racing and guess what is on that puppy.

Andy

 

[Jota Rob]

Hi Maitland

Yes you do look a little large (is that an oxymoron ?) on that bike so the Jota should be more fitting !  If its helps, I'm running 19/37 right now on a 160/60-17 but it equates to 19/40 on a 130/80-18 and works very well, so yes if you're rolling circ is as here a 19/40 or 42 could work well.

I didn't go to mallory no, I went to Rockingham instead and yesterday to Cadwell. 

Rob 

 

[CLEMTOG]

Its been a long while since I did high speed time trials (30/60 minutes plus one lap) on my 1200 (1986/87) but I remember different gearing criteria, I seem to recall Lydden 19/48 and Mallory 19/46, with Snetterton (the circuit has changed twice since then) in the days of that one mile long straight as only then needing 19/40/or 42
all of that from memory.I have got some of those big sprockets left over, not sure which ones, and they are for 530 chain.
CLEM

 

[andychain]

Rob the worlds best oxymoron has to be blow job 

 

[Maitland]

Little more research me thinks.

Need to double check tyre widths as 140 Avons are actually 145-148 mm overall width. Simon has Bridgestones fitted on his Jota and they felt fine at Mallory so will probably go with them, but first I'll check what Avon have.

Not sure about all that sprocket changing Clem, could seriously disrupt my between races afternoon nap! (Thats me in the background) and no comments about age and too much excitement please.

Maitland.