Phil Procter described various mods that he has made to improve drivability on a recent posting.....

Phil, your findings ref the 3rd to 4th gear issue on standard ratios I believe is common. Can I ask what axle ratio you use? I have the same trouble as you had, down here in Cornwall hills are popular additions to the road network and I often find myself reving away in 3rd but not quite able to pull 4th. I run a 5.625 sports/van ratio and was thinking of changing to maybe 4.9 to allow 3rd gear to be used more effectively? Budget doesnt stretch to close ratio gears I'm afraid.

Steve

Hi Steve

You could well have made your problem of hill climbing worse by fitting that ratio of axle, you will be revving around 7% extra at all road speeds with that one, so where mine is revving at about 2000 at 30 mph yours will already be doing around 2150 if my sums are right, so for any given engine revs you will be actually travelling slower.
The 5.625 axle is probably good in a car that has enough power to stay in top gear, but as soon as you have to drop out of top, you are back to the same old problem again, only revving even higher.

I run a standard 5.25:1 ratio axle which you should be able to pick up quite chaeaply in good nick, you could probably sell your van axle and still have enough money for the two close ratio gears you need as well, from memory they cost me £135 at the time, but I did the fitting myself.

You only need to change the two primary gears which drive the layshaft, this pushes up the first three gear ratios to close the gap between 3rd and 4th, I very rarely use 1st anymore unless I am starting off on a steep hill, so the fact that it is a higher ratio does not seem to matter (on my car).

Having said that, my car is a two seater special with an alloy body, you would have to take into account the weight of the car (and occupants) if you are running a standard body etc (not yours, the cars !!).

Also the tyre size can play a significant part as well, I am running 4.00 x 17 on the back and 3.50 x 19 on the front.

I dare say a few other people will be running different set ups, but there are quite a few variables which all play a part.

Phil

Steve, I run my RP on a 1:5.125 rear axle (It should be 1:5.25, but I counted the turns on the fabric coupling compared to the road wheel, thus I KNOW it's 1:5.125), and find up hills if I change down to 3rd at about 29mph, I loose 2mph on the change, but can then keep going at 28mph'ish up the long hills on the A30, until I feel confident to move back up to 4th.

Your car is a lot lighter than mine. Malcolm I think is running on a 1:4.9 with his Ali. RK and that moves......

I would definatly move to a lower ratio if I was you. My RP goes through the harmonic barrier (2,500rpm!) at about 36 mph - Not anything to do with your query, but thought I would throw it in.

I have a table in Excel for calculating road speed relative to axle, gearbox and engine ratio/revs - and thus backward calcs as well. If you want a copy, email >> sandy at duckspond dot freeserve dot co dot uk <<

Sandy......

Just to add my two pennorth, Steve, I would also consider the ratio you would get with the 5.625 axle and the higher ratio 3rd gear in a cr 4 speed box, especially in a light car like yours. There are hills here in Lincolnshire, despite rumours to the contrary, and I find that a good combination myself.
What tyre size do you run?

Regards, Stuart

Great stuff chaps, thanks .

Some more info.....

Sandy... thank you for the offer of spreadsheet formula I am fairly familiar with calculations for road speed/gearing etc , but thank you.
As Sandy points out my car is reasonably light with some slight engine tuning so it does go quite well and I can often "hang on" to 4th longer than other cars, but of course as Sandy points out this is not always a good thing when the harmonic is considered?
I originally wanted to build a racer hence the axle ratio I have ...no plans for that now as the new addition ,my baby son arrived on Thurs night so common sense must prevail!!
I think the ideal combination for me is probably my 19 inch wheels ,the current 5.625:1 axle ratio AND the close ratio gears. What has made me enquire about axle ratios instead is the cost of the close ratio gears, as I could sell my sports ratio axle and buy a 4.9 or thereabouts CWP and maybe have change left, thus carrying on the tradition of not spending any money! I may enquire as to the current cost of close ratio gears just out of interest? I have built my axle twice and the gearbox twice as well so there would be no labour costs involved.

Thanks

Steve.

p.s of course new 5.625CWP's are being made now so I guess the seconhand value of mine has dropped?

Just thinking laterally, Steve, you could acquire a 4.9 axle and a supercharger and stay in top....modern Mini blowers use the vento type screw, I believe. I haven't seen one but word is they're not expensive.
Perhaps I'm just being silly....

Regards, Stuart

Stuart

There is a supercharged new mini driving around my town here that sounds incredible! I think it has been "played with"! That would sound good and go well I reckon!

As you say, probably silly at the moment, seen as even in standard trim mine has broken several times!! One for the future I think .
Steve

Apparently, the 2001 on Cooper S used an Eaton M45 supercharger (very latest versions are now turbocharged). It seems that John Cooper Works offer an uprated blower. The sort of person who wants a blown mini tends to discard the M45 (which is more than adequate for our needs) and fit the JCW conversion. I hear that one sees nearly new M45s on offer for £100-150, having been discarded by their owners after delivery mileage. A quick trawl round the specialist mini spares suppliers on the net seems to confirm this. Perhaps one should get a few in?

I really shouldn't tempt you! Hope you all got some sleep, if not at night!

Regards, Stuart

Steve, as you know my car is fairly light compared to the steel bodied saloons bing an RK saloon. I have a slightly modified Austin Seven engine with alloy head. My back axle ratio is 4.9 and it out climbs any of the other club saloons. Granted I do have to change down marginally earlier than the others but once I do they don't see me until they reach the top of the hill !

Also, from a flat road point of view, I can get up to 41 mph in 3rd gear ( the car has a standard 4 speed box ). If you have a light body with a 5.625 axle then I would expect that you are able to pull away in 3rd if not 4th gear. Excellent if you want to out accelerate the next man but not useful when you are using it as a normal road car. Next time we meet up have a go in mine and see what you think.

Malcolm

I see were you are coming from ref the out accelerating up hill etc etc....
As you know , my prob is that the engine spec I have is not a "rev happy" engine. The racers get away with the lower ratio because they rev like crazy!
I would like to try another car, Mike Davies's Davidstow trip last year was good ,but Davidstow is very rough and you cant get any speed up .
I have a Mother and Mother in law both keen to babysit, so we should be around some club events later in the year! .

Steve

Glad to hear that Steve, we would miss your cheery face otherwise.

You forgot to mention in your statistics how the 'good lady' was doing, shame on you, plenty of flowers I hope, they don't call it 'labour' for nothing.

My youngest is 34, it all seems so long ago !