Can anyone give me a Dummies guide to gear ratios?

[mwalters]

As the title says, I need a dummies guide to these please. Im unsure what my car has in at the moment, although I remember my FVJ (annoyingly) hitting the limiter half way down the bentley straight at Snetterton 300 last year costing me time!!!

So.....a lesson would be much appreciated, my next outing will be Donington so that could be used as an example circuit?!

Thanks in advance!

[tristancliffe]

There's the new drivers seminar at Race Retro!?

But I could give you a little lesson at some point. It's very simple, although there are a number of very common myths and misconceptions around. I used to have a personal record of having never needing to change ratios in a paddock, but I blew that last year at Britcar because of misjudging Silverstone.

There are more qualified people to teach you than I.

[schomosport]

As a start point use the ratios on Tony Wilson's site: https://sites.google.com/site/tonywilson43/

These will give a reasonable guide to the in-betwen ratio splits.

Then you need to scale according to tyre diameter, final drive and any relative difference in car top speed.

So in my case for example my Toyota makes the same power output as the Formula Vauxhall Lotus so should be geared for roughly the same top speed. But I have a taller back axle ratio than the Vauxhall so need to use slightly lower ratios than those given here to compensate.

There are more scientific ways but this works OK for me. You are not driving a narrow rev band race engine so it is top gear you mostly need to worry about and you will then learn from experience if you need something higher or lower in the in-between ratios for a particular corner. Make lots of notes!

If all this is just gibberish then you need to do some Google homework to understand what is going on becasue it is all out there.

Oh and for Donnington they have shifted the chicane since Tony wrote his guide and I don't think he has updated it. First straight shorter, second straight longer......

[mwalters]

Yeah race retro would be fab, except family commitments prevents my attendance

[J Chapman]

Am I right in thinking the FVauxhall Jnr has an LD200 Gearbox? If so please take a look at our website www.formulafordzetec.co.uk Go the ‘Technical Resources’ section and under ‘Gearbox’ you will find all the information you need.

There is an Excel spread sheet which you can download to calculate speed in mph. You’ll have to enter the tyre diameter in inches, the maximum engine RPM and the correct crown wheel pinion (CWP) ratio. Then divide the ratio fractions into decimals, enter them beside the gear number and “Hay Presto” the spread sheet gives you max wheel speeds for each gear.

Obviously the data isn’t much use unless you know how fast you’re expecting to go, I’d suggest pestering the other FVJ owners to get a list and use this as a start. Ratios are easier to compare in decimals rather than fractions. Once you’ve decided on a 4th gear you can start to fill in the second and third with the selection you have, aim to get a good separation. Once you’ve been to a circuit two or three times and you’ve acquired a few more ratios you can start tweaking the lower gears to suit your style of driving, but initially I wouldn’t worry too much about it provided you get the fourth gear somewhere near so you’re not over/under revving. The FVJ in both 8 and 16 valve spec should be tractable enough to pull the car out of the corners even if you have gone a bit high on you second/third gears.

Our site is mainly concerned with FF1800’s but there is plenty of info and ‘How to Guides’ that are probably applicable to many other single seater’s.

[J Chapman]

Now with new and improved gear ratio calculator including graphs!!

[mwalters]

Thats fantastic and thankyou for the tips!

Matt.