Easier/quicker gear changes

[Ruairidh Dunford]

I found 4.9:1 axles really hard work on my SWB cars and have ditched all of them in favour of 5.25:1 ratios, it is by far the best modification I have ever made - fully recommended.

[Mike Costigan]

Interesting comment, Ruairidh; I find when travelling in convoy with a similar car fitted with 5.25 axle, my 4.9 car is better in places, not so good in others, but overall there is negligible difference between them.

[JonE]

I found 4.9:1 axles really hard work on my SWB cars and have ditched all of them in favour of 5.25:1 ratios, it is by far the best modification I have ever made - fully recommended.

so can you better explain the 'really hard work' - are you saying that the 5.25 better liberates the little power they have? i.e. that they are slightly overgeared?

What about box ratios - have you found that the standard 3 speed is perfectly fine?

Would be interested in Mike's explanation also of which bits better and which worse,in those situations described.

[Mike Costigan]

... Would be interested in Mike's explanation also of which bits better and which worse,in those situations described.

Climbing steeper hills, I may start to get left behind, needing to change down to second earlier, but then can overhaul the 5.25 car when it is still in lower revs in top. On flatter give-and-take roads, even when both cars are running in top gear, sometimes one car has the advantage, other times the tables will turn; overall there seems to be little to choose either way.

[Ruairidh Dunford]

I find with the 5.25 ratio I can remain in top gear for longer on inclines, at times not needing to change down at all.

The 4.9 is slightly too tall for my needs - I do carry 5 people and, at times, a camping trailer as well so my load may be more than Mike’s. Even when travelling alone without the family the lower ratio allows the engine to rev more freely and this keeps it on the power in top gear, I find.

In the spirit of always experiencing it first hand, I have left the Cup with 4.9 and will see how it performs - may be some time before I get to try that out however!

I find 1st gear too much on 3 speed close ratio boxes for my ‘own’ use. The four speed close ratio box and 5.6 ratio axle on the Pearl is very nice however. I imagine that on your own, in a lighter car, the close ratio 3 speed would be much more desirable than it is to me.

Under slight initial protest from him, I changed the 4.9 ratio to 5.25 in my father’s Chummy a few years back. After 350k Miles of driving the car in standard form he now finds it a much nicer experience, for the reasons I mention above.

If you have the luxury of trying a lower ratio I think I would reccomend it.

[Robert Leigh]

Robert,
Just looked at your video. All the other cars seemed to be standing still!  What are the other mods on your car as well as lightened flywheel and close ratio box and remote gear change? My pretend Ulster will nearly touch 70mph on the flat with one up,plenty tools,spare wheel,hood etc.It has Nippy type carb and correct Ulster exhaust manifold, carefully mated inlet and exhaust manifolds, full touring wings(in aluminium) and full windscreen. Other mods are lightened flywheel, Super Accessories gearbox, dynamically balanced engine, Speedex head and larger valves.
Cheers,
Dave.

I use a 1.25" SU with 1.125" inlet valves, larger radius tappets, slightly improved ports, Jack French cam, balanced crank assembly and a late head, all put together as carefully as I can be bothered. It all seems to work quite satisfactorily!
Robert

[Hedd_Jones]

With respect to axle ratios etc. I have a mechanically standard short wheelbase box saloon. 4.9 axle. I also have (or rather daughter has) a RP with a 5.25 axle, but a late head, otherwise standard mechanically. Both cars have bosch dizzys.

There are hills (and I mean hills) in my native North wales where the short wheelbase car will not go up when well loaded, yet the RP surmounts fairly easily in 1st.

When father was about to drive the RP, they were well matched on the open road, the RP would climb longer in top, but I'd be up his arse screaming up in 2nd (both have phoenix cranks). Father wouldn't do the speed I did down hill, presumably as his engine was reving just that bit harder. Yet whichever car was in front neither car would build any great lead. The RP is however 2/3 quieter inside with its later 4 speed box. Now the wife is in charge of the RP she holds me up something rotten, but her austin driving skills are not as well developed.

I guess Austins improved the engine as the weight it lugged about increased, maintaining to a degree the performance at an even keel. The late engines in the 3 bearing cars therefore being the 'best' if properly built. Father used to rave about his 1939 Ruby (long since sold).

with respect to down changes from 4th to 3rd. Easy. Ball of your foot on the brake, little pinky on the throttle, throttle off, brake, clutch in, into neutral as you come off throttle (clutch not necessarily required), a good blip on the throttle using your pinky pivoting your foot on the brake, clutch in, a good prod into third and away you go. If it doesnt work you need to match the revs better (or put thinner oil in the gearbox)

[Dave Wortley]

Robert,
Thank you for your reply.
I have used both 1 1/4” and 1 1/8” SU’s along with a Jack French camshaft/large rad tappets but my car had a 5.125 axle and 19” wheels at the time and where I live in Sheffield and running around the Peak District it was awful to drive. No guts in top gear below 3000rev/min. That setup ended on the way back from the Coast to Coast in 1998 when the crank let go in a big way,turning the camshaft into a Z shape. Now have 5.25 axle and standard camshaft/large rad tappets and I gave up with experimenting with SU carbs and used a Zenith Downdraught.

Cheers,
Dave

[Chris KC]

With respect to axle ratios etc. I have a mechanically standard short wheelbase box saloon. 4.9 axle. I also have (or rather daughter has) a RP with a 5.25 axle, but a late head, otherwise standard mechanically. Both cars have bosch dizzys.

There are hills (and I mean hills) in my native North wales where the short wheelbase car will not go up when well loaded, yet the RP surmounts fairly easily in 1st.

When father was about to drive the RP, they were well matched on the open road, the RP would climb longer in top, but I'd be up his arse screaming up in 2nd (both have phoenix cranks). Father wouldn't do the speed I did down hill, presumably as his engine was reving just that bit harder. Yet whichever car was in front neither car would build any great lead. The RP is however 2/3 quieter inside with its later 4 speed box. Now the wife is in charge of the RP she holds me up something rotten, but her austin driving skills are not as well developed.

I guess Austins improved the engine as the weight it lugged about increased, maintaining to a degree the performance at an even keel. The late engines in the 3 bearing cars therefore being the 'best' if properly built. Father used to rave about his 1939 Ruby (long since sold).

with respect to down changes from 4th to 3rd. Easy. Ball of your foot on the brake, little pinky on the throttle, throttle off, brake, clutch in, into neutral as you come off throttle (clutch not necessarily required), a good blip on the throttle using your pinky pivoting your foot on the brake, clutch in, a good prod into third and away you go. If it doesnt work you need to match the revs better (or put thinner oil in the gearbox)

Yes, with respect to the OP's question my first thought was whether he's using the right oil...

[Dave Wortley]

R,
Funny about changing Ian’s chummy to 5.25. I changed mine back to a 4.9 after many years with the 5.25. I prefer the 4.9 now, combined with an old 1” SU. It purrs along very sweetly in top with 1 or 2 up ( occasionally).
Cheers,
Dave.