Leading A-Series engine specialist since 1981
A must for any competition engine build, the MED roller bearing drop gear sets use a highly durable roller bearing/spindle design for the idler gear, to replace the standard pin and needle bearing setup.
This makes an indestructible drop gear set. The idler gear roller bearing runs on the steel support shaft fitted into the gearbox casing. The steel top hat spacer then replaces the idler bearing within the flywheel housing, which encapsulates the idler gear assembly when fitted.
There is no need for any shimming as all tolerances are taken up within the gear assembly, this itself can save time and further expense on over/under size shims and idler gear bearings.
Straight-cut drop gears are stronger and more reliable than the standard helical design, with less side-loading effect. The kit is supplied with all three drop gears - so a primary gear, idler gear and input gear.
We can supply alternative ratio sets by changing the primary gear/input gear. See the Additional Information tab for more on changing drop gear ratios. For reference, A-plus sets have a 22mm idler gear shaft and pre-A-plus have a 19mm idler shaft. Both 1275cc and 998cc sets can be chosen from the dropdown menu above.
For fast road applications we would recommend setting the primary and idler gear end float between 0.004-inch to 0.006-inch. For competition, a marginally larger tolerance may be suitable - contact us if you're unsure.
The MED drop gear sets are available in three different ratios, which can be used to tweak the final drive ratio. Changing the effective final drive ratio will either improve acceleration or top speed potential, although one will always come at the expense of the other.
We can do this by changing the tooth count on either the idler gear or primary gear to 23 or 24 teeth. The idler gear in the middle remains at 30 teeth regardless.
The table below shows the various tooth counts and the effect on the drop gear ratio:
|Input gear||24 teeth||24 teeth||23 teeth|
|Idler gear||30 teeth||30 teeth||30 teeth|
|Primary gear||24 teeth||23 teeth||24 teeth|
To calculate your effective final drive ratio based on the above, simply multiply your existing final drive ratio by the number of the drop gear set. So for example, a 3.47:1 final drive ratio with a 1:1.043 drop gear set then becomes 3.62:1. Remember that the higher the number, the shorter the gearing will be, so this change will result in a higher engine RPM for a given speed.
Changing the primary gear is easier than removing the differential to change the final drive ratio, so racers use this to adjust their gearing to suit different circuits. Keeping an engine in its peak powerband for longer will result in a faster lap time.
See the following table for our final drive conversions using the various drop gear sets:
|Original final drive||Effective final drive|
|1:1.043 drop gears||1:0.958 drop gears|