Articles search results for input gear

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A fairly crucial part of how the idler gear operates is its tolerances and running clearances. part numbers: 22A1545, 22A1546, 22A1547, 22A1548, 22A1549, DAM4822, DAM4823, DAM4824, DAM4825, GUG705563GM, AAU8424, ADU6033, CCN110, 2A3643, 22A152, 53K547, Terminology: DTI - Dial Test Indicator End float is a continual problem as folk either ignore it through ignorance or lack of accessible information on how to do it, or belief special tools are needed. Also, later factory assembled engine units (from about 1992 onwards) were built up using whatever shims and thrust washers were available, since Rover were not making regular orders for all shim/washer sizes due to the forthcoming end of production. Consequently, many units left Rover with incorrect (usually too big) clearances. The idler gear was no exception. Too tight a clearance and the idler gear will either seize solid when it gets hot, or destroy the thrust washer thrust faces in the comparably soft aluminium gearbox and t

GEARBOX - Up-Rating Drop Gears

The standard drop gears are fine for practically all road use - almost irrespective of power output. part numbers: DAM9373, C-STR123, C-STR124, C-STR30, C-STR30A, C-STR30T, C-STR30TA, C-STR230, C-STR240, C-STR250 Terminology - Drop Gears - Transfer gears (primary, idler and input gears) Large-bore - Refers to anything based on a 1275-type unit Small-bore - Refers to anything based on 850/998/1098 units Despite what many folk believe - they are more than strong enough, and will perform perfectly well if correctly set up. That means getting the idler and primary gear end floats right, and using new bearings for the idler gear at each re-build. Simply following the methods outlined in the relevant workshop manuals will achieve these simple goals. There are two problems with standard drop gears - the main one is the helical cut of the teeth, the other a very limited selection of ratios. The helical-cut teeth are essentially power absorbing - both from increased metal-to-metal c

Gearbox - Up-rating diffs and FDs

There’s a good selection of straight-cut final FDs available. Examine the FD table, and using information from

'Gearbox - Final dives, standard' and 'Gearbox - Formulae for car speed, etc.'

you can assess which would best suit your usage. Bear in mind that they’re noisy, make sure you select one that’ll fit your diff unit, and also consider that using drop gears will allow fine-tuning of the ratio where necessary. See

'Gearbox - Up-rating drop gears'

Gearbox - Up-rating diffs, FDs and ancillaries.

part numbers: C-BTA166, C-BTA167, DAM6624, BTA101, 2A7062, DAM5071, DAM6027, RPS1418, C-AJJ3385, C-22A1731, ...Read more

GEARBOX - Close-Ratio Conversion Pre-A+ Gearbox

As outlined in the 'Gearbox - standard production gearbox types' article, it is entirely possible to change the common 4-syncro gearboxes to the helical close-ratio set-up as used in the Cooper S, 1275GT, 1300GT, and some early MG Metros providing the right parts can be sourced. And you don't already un-knowingly have the close-ratio kit fitted! Part numbers are detailed at the end.

The other pre-requisite for this conversion is that it can only be applied to the early, pre-A+ type mainshaft gears. That's those that have the square-topped teeth as supposed to the distinctively pointed A+ profile. This is because despite being endowed with A+-type fittings for the mainshaft end and layshaft, the conversion gears have the pre-A+ tooth profile. This is not to say that the conversion cannot be put into an A+ gearbox casing - it can and is detailed in the relevant article.

What is essential to understand is that the pre-A+ second and third mainshaft gears are going to be

Engine - 1098, Initial Tuning

The 1098 (1100) engine has had a lot of bad press over the years - largely because of early experiences when trying to tune the motor brought about problems with the then standard components available - they simply were not up to taking any real punishment as experienced in racing.

See bottom for useful part numbers.

This fallacy was handed down generation to generation like some scary bedtime story. Those that have used the unit in more recent years, employing more capable componentry know what a demon motor this can be. Following is an initial look at what it will do with a little modification - the results compared directly with it's smaller brother the 998 for illustration of the potential.

Abridged History
When the Mini was first conceived it ustilised a de-stroked version of the then quite remarkable 948cc A-series engine.

‘Salisbury’ is the word banded about by most un-enlightened folk when discussing LSDs for Minis, mistakenly believing the word covers all Mini orientated LSDs. This is grossly incorrect. Terminology - LSD - Limited Slip Differential The ‘Salisbury’ was designed in the ‘50s at a time when racecars were a good deal less sophisticated than today. Tyres were usually cross-ply with severely limited grip due to poor compounds developed ostensibly for rear-wheel-drive cars; the front wheel drive of the Mini being a rarity. And tracks were more than a little ‘bumpy’. Agriculturally built cars needed an LSD designed along similar lines; enter the Salisbury - effectively developed from a tractor diff. High static pre-loads were more than common to help compensate for severe short-falls in chassis, suspension, and tyre design. To all intents and purposes the diff was practically locked up, making the car a real beast to drive.

The first Minis rolled off the production line with a three-syncro gearbox, first gear as explained earlier was still a hit and miss affair.

Terminology -
FD - Final Drive

NOTE; A 'high' or 'low' ratio gear is in reference to it's performance, not it's numerical number. To illustrate - a 'high' FD ratio will give 'higher road speed', but will have a numerically low figure. A 'low' FD ratio will give lower road speed, but have a numerically high figure. A by-product of this will be reduced acceleration capability on the 'high' ratio, increased acceleration capability on the 'low' ratio. The main gearbox gears work in the exact same way.

I’m sure we’re all aware of Sir Alec Issigonis’ brilliant solution to the gearbox location in the Mini - just fold it up underneath the engine, simple. Following is a résumé of the production gearboxes to date.

Basic rule to remember is ratio is established by dividing tooth count ondriven gear by the tooth count on its driver. To work out overall gearbox ratios you also have to establish the constant ratio.

Terminology -
FD - Final Drive (diff ratio)

Formula : 60,000 FD (Final drive/diff ratio) x wheel rev per mile.

Calculation for establishing vehicle speed for different final drives.
Formula These are for common tyre types, and accurate enough for assessment - a combination of using industry standard for theoretical calculation, actually measured assortment of wheels/tyres, and calculated averages! Applying

GEARBOX - How they work

Having decided on or even implemented a course of action to bolster the performance of your Mini’s engine, maximising it’s potential should encompass a good look at the gearbox.

GEARBOX - How they work

Having decided on or even implemented a course of action to bolster the performance of your Mini’s engine, maximising it’s potential should encompass a good look at the gearbox.

The red lights went out after a short wait and the 2005 season was underway. I held position and went early on the attack,

It seems remarkable, but a winter break of over six months is never enough time to prepare a racing car! The truth is, at long last I've completely refurbished the hall, stairs and landing at home. That concludes a 7 and a half year ...

Contrary to popular mis-guidance, all BBUs will fit all four-syncro gearboxes. It was only the three-syncro boxes that varied in casting dimensions causing hassles where 1275s were applied to 850/998 gearbox casings.

Terminology -
BBU - Big Bore Unit (1275cc based engines)
SBU - Small Bore Unit (850/998/1098cc based units)
FD - Final Drive

NOTE: This information is largely for transplanting large-bore engine units into small-bore engined Minis. For further information on up-grading transfer (drop) gears, refer to relevant separate article.

Terminology -
BBU - Big Bore Unit (1275cc based engines)
SBU - Small Bore Unit (850/998/1098cc based units)
FD - Final Drive

Calculation for gear ratios and transmitted engine rpm Basic rule to remember is ratio is established by dividing tooth count on driven gear by the tooth count on its driver.

Terminology -
FD - Final Drive (diff ratio)

Calculation for establishing vehicle speed for different final drives.
Formula : 60,000
FD (Final drive/diff ratio) x wheel rev per mile.

SU Carbs - The history

Practically every Mini owner can name the brilliant engineer responsible for our obsession. Many can name the man responsible for the rubber suspension spring.

A goodly number know a fair bit about the engine's heritage and the man who came up with the extremely efficient cylinder head design.They account for the biggest chunks of the Mini's anatomy. But what about that other extremely simple yet hugely effective instrument that features so prominently when engine tuning occurs - the SU carburetter? A limited few can tell you what 'SU' stands for, extremely few have any idea of its concept and evolution. So let's put that right… In the beginning Strangely enough, it all started way back with William Banks Skinner; one of the owners/directors of the well-known Lilly and Skinner footwear distributors.

Zandvoort Double Podium

Zandvoort Double Podium

The Mini 7 Racing Club's season finale took us to Zandvoort for the second year running, although last year it was a non-championship round. Both championships had already been wrapped up - Ashley Davies topping the points table for the mini se7en challenge supported by Mini Spares, and Shayne Deegan for the mini miglia challenge supported by Mini Spares. Well done to both of you.

When most folk talk about limited slip differentials for the Mini, minds immediately turn to the name "Salisbury". Indeed many think that word covers any LSD for the Mini. This, of course, is not so. The Salisbury diff was designed in the 50's at a time when race cars were not sophisticated, tyres were usually cross-ply with limiting grip due to poor compounds, and tracks were more than "a little bumpy".

Articles search results for input gear

Zandvoort Double Podium

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