Original T1 gearing?

[wil]

I have had gearing adivice using the lower ratio pulleys, but I have not got them yet.

Can someone suggest a good starting point for a 12t motor using the original internal ratio(2:2.125, i think!)

cheers

[John Stones]

What sort of track

[wil]

It changes each week, but usually a couple of medium length staights, and some tight bends as well as faster corners.

I'm just after a starting point really. I have run it with an 85 spur and 27 pinion, but it's not nearly as quick as other 12t runners

cheers

[ldebackker]

you could try a 29 pinion, or else a 30. I think you'll have enough topspeed with the 30, but first try the 29.

good luck ;)

[Doomanic]

I'd have said that way overgeared! That's 6.7:1!
That's not much lower than I run for stock (6.375:1)! :o

If you overgear a car it will appear slow, have you tried a smaller pinion?
Do you know the overall ratio the other guys are running?

Also what cells are you using as that will also have an effect?

[wil]

I did use a 23 pinion, then a 25 pinion but neither were that brilliant.

Will a change in spur size have a more significant effect than pinion change??

Accleration needs priority I think, I just want a good place to start with for a 12t motor, then I can adjust it at the track.

As for cells, they are your very own! ;D

[Doomanic]

OK, it won't be the cells then! ::) ;D

Try and find out what ratio the others are running and try that.

[wil]

So would a ratio used in a corally C4, for example, work the same if it was used in a Xray T1, even if internal ratios are differnt??

[Doomanic]

Yes, if you have the final drive ratio and a calculator you can work out what pinion/spur combo you need to replicate it.
You will need to know the internal ratio of the car you are copying.
The X-Ray is 2.125, dunno about the corally.

[university_dave]

C4 and C4.1 have internal ratios of 1.88

[Petermarkphillips]

for original pulleys. try 87 spur with 27/28/29 tooth pinion with a 12 turn modified outdoors. Thats what i ran at Brca national with krypton, sightly higher with peak/orion core.

If you havent got a 87 tooth spur, look at your gear ratio chart, and choose a similar ratio for the spur gear you've got.

[wil]

Cheers guys,

OK, I have got my mates gearing info. He runs a 87t spur 27t pinion in his corally C4.1.

What is the equation for working out the final drive ratios??

thanks

[Doomanic]

Spur divided by pinion, then multiplied by internal drive ratio.

So that is 87(spur)/21(pinion)=4.143*1.88(C4.1 internal drive ratio)=7.789

For your car 85/24=3.542*2.125=7.536
or 85/23=3.696*2.125=7.854

As you have already tried the correct starting point (23 tooth pinion) have you considered the possibility that your motor needs a rebuild?

Is it possible you have the alternative pulley set which gives an internal ratio of 1.77?

In which case 85/19=4.474*1.77=7.919
or 85/20=4.250*1.77=7.523

[Petermarkphillips]

Always remember when working out ratios, its the driven gear didivded by the drive gear. ie spur over pinion. internal ratio in xray is the large pulley size over layshaft pulley size.

multiply the internal ratio by the spur gear over the pinion size.

[wil]

I brought the car second hand, so i will check about it possibly being 1.77, didnt think of that!

The motor was run with new brushes last time out and a clean comm, although not skimmed.

Thanks for your help, I will check the internal ratio out and thanks for doing the sums for me! ;D

[NumanR]

Hi guys just wanted to know if any of you drive inside on carpet and what gearing you would recommend for a 12d, I have the 1.77 gears fitted and use the original spur (93 or 96?) with 24 pinion, the motor normally comes off very hot also the belt is running very close to the motor. Advice please guys. Thanks.

[Dave Treacy]

Mark, you need to run a larger spur gear to lower the motor - improves CoG and stops it rubbing against the belt. Try a 96 (original is a 93) with a 25.... and don't drive the nuts off it, it isn't a big 6!

[NumanR]

Thats why my brick servo dont fit! Thanks Dave. Is btcc going to be coming back to MK in 2004?

[Dave Treacy]

I don't know if the calendar has been officially announced, but let's say that I'll improve my lap record before you get a chance to beat it....

I'm planning to run in next years BTCC as well - just gotta get Sorex tyres for my boys - they race boring cars.