The standard 'genuine' rubber cones from Minispares I find are good quality or they also do the uprated versions if you think your rally driving might need it:
http://www.minispares.com/product/Class ... 0to%20shop
"The Real Genuine rubber cone spring, made correctly from Rover's only original tooling for the assembly line and spare parts sales, despite others' claims.
These are the only product available with correct ride height, bonding to metal, threaded top cup and metal ring made in the UK, for Mini Spares only.
Beware of all copies and old stock being offered anywhere for sale especially on ebay and websites. Genuine cones are precisely manufactured to certain technical specifications with the patent number stamped in the rubber. Anything without "patent number 763432" is not genuine.
The compact design & durability/quality of the rubber cone helped make the Mini the classic that it is today. Designed in the late 1950's it was ahead of it's time. The only problem is that some may still be driving around on cones that could have been built in the early 1960's with a UNF thread. They are now only Metric thread. The design is good, not ever lasting. The rubber not only gets very hard but it also sags and loses it's ability to hold the car upright. It is not uncommon to have a cone sag so badly that it lowers the car 2 or 3 inches and it handles terribly. Like all rubber products, they only have a certain shelf life and being fitted equates to the same. These might need replacing every 5-7 years depending on use and climate, but are usually good for at least 20,000 miles in the UK.
Measured at the wheel, the spring rates at the static load position are 118 lb/in at the front and 98 lb/in at the rear. With three passengers and 50 lb of luggage, the loads per wheel at the same position are respectively 468 lb and 355 lb.
These loads rise to 1,050 lb and 670 lb at full bump and fall to 240 lb and 100 lb when the rebound check is in operation."
Red Spot
"Competition rated rubber spring for use on all Road/ Rally Minis. Priced individually. Marked with a red spot on the metal base for identification.
The thick top plate has an internal metric thread for strength rather than a nut welded in place as per standard cone springs(MiniSpares design now copied by all).
These uprated springs do not feel much harder or give a harsher ride, but were specially developed specifically to give a more compliant and supple performance by way of careful re-arrangement of the spring rate. Basically, less body roll with a better working rubber cone that does not tail off as quick in spring rate under use . You will need hilos with these as they sit higher and although settle a little, adjustable suspension will be required. Beware of copies on the market as they do not perform the same and not manufactured in the same way.
These are manufactured by a company who are involed in Formula 1 and high profile motorsports rubber parts. Under use they get hot and ours retain more consistency than any other on the market as they are specially moulded. Keith Dodd fitted 2 on the front of his twin point car without any sagging or deterioration to date after over 10 thousand hard road miles.
If using these on 10" wheels with Hilos cut 3/4" off the end of the centre threaded bolt of the old type Hilo with a circlip as it will bottom out on the cone spring face and the car will sit high, for extremely lowered cars the hilo face will also need machining a few mm."
http://www.minispares.com/product/Class ... |Back%20to
Yellow Spot
"These cone springs will require Hilo adjustable suspension as they sit higher than the originals.Containg an anti fade property and shape which helps them going off during racing and giving hopefully a season of racing before replacement. A softer road going compound is C-STR687. The thick top plate has an internal thread rather than the nut welded in place as per the standard cone springs or copies. these have a yellow dot on the metal base for identification purposes.
These are manufactured by a highly technical company involed in rubber on Formula 1 cars."
http://www.minispares.com/product/Class ... |Back%20to