[Boddington]

Is it possible to reduce the final drive ratio on the Mini? I've got a modded 03 MCS which I use more and more on track and less and less on the road, so I'd like to reduce the final ratio by about 10% if possible to increase acceleration and make the ratios closer.

I'm not bothered by the reduction in top speed or motorway fuel consumption.

Cheers!

[Johan422]

HELIX offers a lower final drive. It says that he imports them form England, so you may be able to find the manufacturer and buy direct

[robbo mcs]

Quote: Originally Posted by Boddington (original)

Is it possible to reduce the final drive ratio on the Mini? I've got a modded 03 MCS which I use more and more on track and less and less on the road, so I'd like to reduce the final ratio by about 10% if possible to increase acceleration and make the ratios closer.

I'm not bothered by the reduction in top speed or motorway fuel consumption.

Cheers!

Hi,

The quickest way to do it is to go to a smaller rolling diameter tyre. I use 205/50/16 on the track, which has a quite small rolling diameter of 611mm. Other common tyres such as 205/45/17 and 215/4/17 are significantly larger. Having the smaller diameter effectively reduces the final drive ratio, and makes a suprising big difference on the track.

I know someone who ran kumho 205/45/16 track tyres, which have a rolling diameter of 591. This dramatically reduced the final drive.

Cheers

Robbo

[Westy]

Quote: Originally Posted by Boddington (original)

Is it possible to reduce the final drive ratio on the Mini? I've got a modded 03 MCS which I use more and more on track and less and less on the road, so I'd like to reduce the final ratio by about 10% if possible to increase acceleration and make the ratios closer.

I'm not bothered by the reduction in top speed or motorway fuel consumption.

Cheers!

Please digest this before you start making ratio changes:

Changing your final drive does not make your gearbox ratios closer, the drop in RPM between gear changes is the same regardless of your diff ratio. The only way to obtain closer ratios is to install a different CR gearset. You would use a close ratio gearset to match an engine with a narrow powerband, it will do little for a lightly modified engine with a torque curve as flat as an MCS.

Lowering your final drive will not improve your acceleration overall. Yes, it will change the speeds at which your gearing might be ideal, so may optimise gearing at certain tracks and on certain corners, but then will make it worse at others.

These comments come from years of motorsport, calculating and using different diff ratios and gearbox ratios. You match the gear box ratios and final drive to the track and performance curve of the engine - not assume lower diff is faster.

IF you would like to play with ratios, and see their effect, this is a very good gear calculator to download. I've used it to great effect......................... GearCalc

If you want further advice on optimising gear ratios, PM me.

Kev.

[Boddington]

Thanks Johan - wow, £800!

Robbo - funny you should say that! I've just bought some 215/45/17 tyres which are larger diameter than the ones I took off, and the reduction in acceleration is noticeable, which is what got me thinking about trying to reduce the final drive in the first place! But if it's going to cost £800, I might have to think again...

[Boddington]

Cheers Kev, helpful advice. I realise it won't actually make the ratios closer, but it would make the speeds at which you change gear slightly closer. And acceleration in any given gear at any given speed will be higher (assuming traction is not the limiting factor). But I take the point that this may well put me in the wrong gear or wrong part of the rev range at different points on a particular circuit. There are a couple of places where I just nudge the limiter before hitting the braking zone at the new Anglesey circuit, for example, so lowering the final drive would mean I would need to change up just before braking.

Maybe a big brake kit would help give me a few more yards before hitting the braking zone.... Hmmmm....

[Westy]

Quote: Originally Posted by Boddington (original)

Cheers Kev, helpful advice. I realise it won't actually make the ratios closer, but it would make the speeds at which you change gear slightly closer. And acceleration in any given gear at any given speed will be higher (assuming traction is not the limiting factor). But I take the point that this may well put me in the wrong gear or wrong part of the rev range at different points on a particular circuit. There are a couple of places where I just nudge the limiter before hitting the braking zone at the new Anglesey circuit, for example, so lowering the final drive would mean I would need to change up just before braking.

Maybe a big brake kit would help give me a few more yards before hitting the braking zone.... Hmmmm....

Hi,

I still don't understand why you think your accn will be higher at any given speed by lowering the diff. It won't make the speeds that you change gear closer (as a %age of each other, they are the same regardless of diff) - you will just be shifting up at lower speeds. The engine will feels to spin up quicker 'cos it is - but that's only cos it's not pulling the car to as high a speed as a longer diff ratio for any given gear.

You only have one optimum compound ratio for any given road speed to put your engine at optimum revs - if you have a short diff then you will just end up having to shift earlier to the next gearbox ratio to stay close to this optimum compound ratio as your road speed increases.

Don't worry about running out of rev's just before a corner, the last few revs at the last few feet of a straight are not important, what is important is getting the correct ratio and revs out of a corner - remember every mph you carry out of a corner is held all the way down the next straight - whereas running out of revs at the end of a straight only hurts you for a moment.

I've not been to the new Ty Croes yet, looking forward to it, I'm there in September.

Kev