What gearing ??

[Willow Racing]

Help I need some advice. Was at Darley Moor on Sunday and my gearing was all wrong. Running a Thundercat which makes almost 107 bhp and 50ftlb of torque was running 15 - 46 which was to long, could only just get half revs in top before having to start changing down. I have a 13 and 14 for the front and 44 and 43 for the rear. Do I need something else ? . Going to Mallory next so was going to drop to 13 - 46 or is that to much. Dave

[craig hauxwell]

13-46 might be to big a drop, when we ran the thundercat we used 14-43 which isn't far off what your running now so try a 14-44 or 14-45
here are a few ratios you can choose from with the sprockets you have avaliable

15-46 = 3-13 (what you where running)
14-44= 3-14 13-43= 3-30
14-45= 3-21 13-44= 3-38
14-46= 3-28 13-45= 3-46

dropping any lower than 3-13 will make things worse for you if you couldn't rev out with 15-46

[tufty113]

we used to run 13 44 for most shorter cuircuits and a 43 /42 for say cadwell...but thats on a stock gearbox.....we poss used a 14 front say at snett with a 42/41 rear....hope that helps...ta matt dix

[oldbelly]

13-43 is a good ratio for most short circuits on a Thundercat.

[Willow Racing]

Thanks for that guys, always good to get low down from people in the know and with experiance of the bike or engine. As a matter of interest Craig how do you work out the ratios ? We run a c/r box so will that make any differance. I always prefer to be slightly lower geared than other people
to get better drive out of the corners, it seemed to work for me on the 350 and it might help me make better starts, but thats another story. Anyway many thanks for the help. Dave

[neary racing]

we ran 13/42 or 13/43 on our bell tuned thundercats.

[G JONES]

As a matter of interest Craig how do you work out the ratios ? We run a c/r box so will that make any differance. I always prefer to be slightly lower geared than other people to get better drive out of the corners,

Hi Dave - it's just a matter of dividing "drive" in to "driven" sprocket - to know if you are geared the same as someone else - you would need to know their primary gear ratios (and tyre sizes if you wanted to be real accurate )
Here's a quick breakdown for some sprocket combinations (for the TZ) - and below that the "lowest" - to "highest" gearing setup.
If you need it doing for your sprocket sizes - give me a shout..
I was always told when I started racing - that you should aim to gear for maximum revs in top gear at the fastest part of the circuit - which should be not far off - but you may need to adjust that a bit depending on the circuit layout - you may need to adjust by a tooth for a particular corner sometimes....hope that helps...

G/BOX REAR RATIO
13 x 36 = 2.77
13 x 37 = 2.85
13 x 38 = 2.92
13 x 39 = 3.00

14 x 36 = 2.57
14 x 37 = 2.64
14 x 38 = 2.71
14 x 39 = 2.79

15 x 36 = 2.40
15 x 37 = 2.47
15 x 38 = 2.53
15 x 39 = 2.60

16 x 36 = 2.25
16 x 37 = 2.31
16 x 38 = 2.38
16 x 39 = 2.44

LOWEST
13 x 39 = 3.00
13 x 38 = 2.92
13 x 37 = 2.85
14 x 39 = 2.79
13 x 36 = 2.77
14 x 38 = 2.71
14 x 37 = 2.64
15 x 39 = 2.60
14 x 36 = 2.57
15 x 38 = 2.53
15 x 37 = 2.47
16 x 39 = 2.44
15 x 36 = 2.40
16 x 38 = 2.38
16 x 37 = 2.31
17 x 39 = 2.29
16 x 36 = 2.25
HIGHEST

[dick tapken]

and after all that all it mean's is a small one on the front and a bigger one on the back bloody mathmatician's!!

[neary racing]

classic

[craig hauxwell]

and after all that all it mean's is a small one on the front and a bigger one on the back brooodily mathmatician's!!

Maths was never your strong point eh Dick

[craig hauxwell]

Pm sent Dave.

[dick tapken]

no craig never any good at math's but i can allway's get a round right at the pub are you doing tahyerfanny?if so see you easter will try and stay out the way on the beemer.

[craig hauxwell]

no not doing it this year tappo after the fiasco over the oil spillage from the road sweeper last year.that hydraulic oil will still be coming out of the tarmac now (what tarmac there is)

[gatekeeper]

13/42 with my thundercats