Cub Trials Gears

[old bones]

My recently finished cub still has road gearbox internals with 13t drive and a large rear sprocket (cant remember how many teeth it has!) would the fitting of wide ratio parts be of much benefit bearing in mind that I am returning to trials after a long lay off so consider my self just above novice standard, are the parts available ? and a rough cost ?

In conversation at a trial it was suggested that there was a way to achieve the lower gearing by fitting Bantam parts does anybody know if this is possible and what would be involved.

Any advise gladly accepted

[subira]

I don't have my notes with me, as I wrote all the details of the advice I got down when I built my bike, but here goes.

The wide ratio box is the best option (IMHO) as it gives a better spread for trials, i.e. low first and close second and still keep a fourth that makes roadwork possible. I hunted around for one for a long time and eventually got one from across the pond - I couldn't unearth a complete one in the UK.

Serco used to do a lower second to add to this that makes first and second even closer - might still do it. Also using the 16T engine sprocket on the primary drive gears everything down, even if it means a half link on the primary chain.

This make first and second very useable, even with the 199 cc motor and 15 stone on board. I can't remember what the final drive sprockets are but the rear is pretty small and doesn't snag on rocks etc.

There are of course loads of: road based, CR and ECR boxes being used to good effect, so its not a disaster if you have one. If you haven't done the engine 16T that's a good start to slow everything down, easy to do and doesn't require an engine strip. Then you can see if its the spacing or the overall gearing that needs some work.

Loads of different opinions out there, this isn't the gospel, just works for me.

[odgie]

It's maybe worth knowing that, as you lower the overall ratio, either by final or primary drive ratios, you also in effect make the gears a closer ratio anyway (I think it's something to do with the lower the overall ratio, the less effect each gear change has, but don't quote me...). If you set the bike up for a very low first, that will as a consequence make second closer to it. A wide ratio box will give you a higher top gear, but unless you're doing much road work, it isn't really that important (how many times do you get flat out in top these days, with trials usually laid out quite compactly?). My Sunbeam has all the stock road ratios inside, and you can't lower the primary (it's gear driven), so I'm stuck with the 'cotton reel/dinner plate' type final drive, but it works fine enough. I've now got first low enough to make second also a useful gear (which of course is not always a Good Thing, as if you get them really close, unless you're An Expert, you end up with the dilemma of which gear to choose...) My advice for what it's worth would be to save yourself the expense and hassle for the time being, set the bike up with first gear low enough (and in my experience that's always a bit lower than you think you need it to be), and see how useful second then becomes as it is. In the real world, a bit of difference between the two will at least make choosing which for what section a simpler task, and you may find you don't need to strip the engine and spend a heap more money on it after all. :-)

[subira]

This isn't my work, but a very helpful diagram all the same.

[old bones]

Many thanks Odgie and Subira

Your advise was most welcome and with the help of the diagram I can work out what will happen (in theory) if I do a sprocket change.

But most of all, now I know its not critical to fit the WR internals. Perhaps I will ride it a few times and see how it goes

Thanks again

Old Bones