GTT R53 Eaton M45 Supercharger Rebuilds 12 years on… Updates and Developments.

posted in: GTT Blog & News

Important note!

we keep stressing how important it is to get every supercharger rebuilt if it has never been done.
Leaving it until it starts to get noisy is risky and leaving it longer and continue driving will severely increased chances of it becoming unserviceable or extra expensive rebuild. This can damage sealing faces and bearing seats beyond repair.
Even just stopping driving the car and leaving it can cause damage. It needs to be removed instantly and inspected / rebuilt. As you can see sometimes the coolant breaks into the PTO and severely corrodes the rotor drive shafts oil seal face. Leaving water/coolant inside will rapidly rust.


What is a supercharger.

For beginners we will explain in short. A superchargers purpose is similar to a Turbocharger,(Note: normally aspirated engines have neither) it’s basically an air compressor to force more air into the engine (forced induction).. More air = more power. A supercharger is belt driven from the crankshaft, a turbo turbocharger is powered by exhaust gases. A common upgrade is to fit a reduction size supercharger drive pulley.. The smaller it is the faster the supercharger will spool resulting in more power. Typically -17% or -15% pulley is used on the R53 for more power. This can also be achieved/improved by fitting a GTT oversized Crank Pulley.


Black VS Grey Rotors

Pre-facelift cars all had the grey rotors inside the superchargers, unless it had a JCW tuning kit installed which the supercharger was replaced with the Black Rotor version (the same as Facelifts but the JCW came with a -11% reduction Pulley for more power) Typically the Black rotor versions (Teflon coated) are more hard wearing and run a tighter clearance tolerance between the rotors which has slightly better power efficiency than the grey rotors.

It has been 6 years since we started offering rebuild services for the Gen 1 Cooper S Supercharger, and has proved ever so popular! we have now rebuilt well over 600 units!

We must bring to attention that we have seen an increasing number of owners ignore what their ‘non rebuilt’ superchargers needs.

If your supercharger is noisy, (grumbling/rattling) stop driving. And get it sent to GTT a for GTT rebuild. There have been a number of occasions where owners have just kept driving until the car over heats and causes severe damage to engine. This can also result in the supercharger being beyond Rebuild!

Most should be aware by now the importance of a fully serviced/rebuilt supercharger is due to the engines water pump being driven by it… If this fails it will cause catastrophic engine damage and at huge cost.

Please see previous Supercharger rebuild articles on “News” Section for full understanding of the Eaton M45 rebuilds. For Full Spec of rebuilds please see GTT GEN 1 Supercharger Rebuild Page.

The fact of the matter is that they will all need rebuilding regardless of mileage. This is mostly due to the age of the supercharger being at least 10-15 years old the standard inferior internal oil seals perish causing all the usual damage etc. Even new units bought from MINI Direct are “New, old Stock” (and cost a whopping £3450!! inc vat) and these will all have the same Achilles’ Heel. We often receive these by customers for inspection/rebuilds as they do not want the risk of problems further down the line.

We must also point out the issues from owners who have tried buying and fitting second-hand units of ‘unknown condition’. Not only have these have become scarce and more expensive, we have had reports of loss of drive to the water-pump causing cracked heads and reports of others seizing from debris in the rotor housing……… why take the chance when GTT rebuild your own supercharger to the highest spec?


9/10 Superchargers sent to GTT only require this option, spec Now includes:

 In addition to installing new GTT Up-rated PTO Gear Set, GTT Spindle, up-rated bearings & seals + oil change (as per previous spec). PTO Plus rebuild now also Includes: Removing Snout & inspecting bearings, GTT up-rated Coupler installed + Flushing & Oil Change, Removing & Inspecting rotor pack condition (checking for excessive end float) + dressing out any high spots on the rotors causing rubbing to casing or each other + cleaning of rotors and internally of rotor housing & Repacking Rotors needle roller bearings with High performance grease.



GTT Snout Rebuilds

We do rebuild other sections of the Supercharger such as the snout/nose.. This seems to mostly be required if in the past the drive pulley has been removed/attempted to be removed without correct method/tooling, we highly advise to leave it to qualified technicians.

GTT Snout rebuild consists of: Full snout strip down, clean/flush, inspection and rebuilding. Includes 2 x ball races, new snout seal. GTT Coupler and oil change.

Fitting GTT Reduction Pulley Service

We now offer a Service to Remove Standard Pulley + Supply And Fit GTT Reduction Pulley, It is the perfect time to have your Standard pulley removed & replaced with a GTT reduction pulley during a rebuild. This is the most cost effective time to replace and the most beneficial mod for the Supercharged Mini with approx. 25-30BHP gain! Free fitting with GTT Snout Rebuild Only. £69+vat extra fitting cost in conjunction with ‘PTO PLUS’ Rebuild

Bolt-on VS Interference Fit Supercharger Pulleys

Often discovered during rebuilds damage has occurred to drive pulleys’ shaft… this is usually caused by aftermarket “bolt-on” type pulleys.

These “bolt on” type pulleys can come loose & slide along the shaft, this makes the supercharger pulley out of line with the other pulleys which causes the belt to wear very quickly or even jump off.

With some brands of reduction pulleys’ we have noticed the supercharger seal retaining clip (tab seal) has had to be removed to fit this pulley in the correct position. This is not ideal, and could result in the seal moving and leaking (one image shows how one of these brands has damaged the seal retainer clip as not enough clearance).

Another image shows where Superchargers Snout outer oil see has been severely damaged due to the seal retainer being spun around with the “bolt on type” pulleys inner sleeve.

Bolt-on’ type pulleys are known to slip, slide and even fall off on rare occasion.

Identifying the problem… A sudden loss of power will be caused by this as the supercharger has lost all drive, or intermittently as the pulley jams then slips repeatedly. This means the water pump will too! Over heating is inevitable as the water-pump is driver by the supercharger, if not fixed, worst case could result in catastrophic engine damage!

On some occasions the free spinning of a loose pulley on the shaft wears it so severely it is no longer serviceable.

GTT Supercharger reduction pulleys use an interference fit system to the shaft (same as OEM pulley) so why risk it?


Why Not To Use — DIY Supercharger Oil Replacement Kits With Syringe

We have seen this a few times where people use these kits to refill/replace the superchargers oil through the drain plugs. This is highly risky as you do not know the condition of the internals and by topping up you unknowingly are mixing new oil with all the old sludge/swarf/dust etc making a sort of grinding paste that destroys your PTOs internals… and in some instances beyond rebuild.

BMW can now only supply recon units from Eaton at a whopping £3450 (inc vat) and above…,second hand units of ‘unknown condition’ becoming both scarce and more expensive, a GTT rebuild on your own charger makes much more sense.


Engine Coolant Inside R53 Superchargers PTO?

This is a rare case (we currently have seen around 10 cases) where the water-pumps seal fails and coolant forces its way into the Superchargers PTO ….

The water pump and PTOs… mating surfaces corrode together making a seal, so the coolant may not even be coolant dripping on the floor at all.

Some incidents we’ve seen the coolant get through the second oil seal in the PTO (under small gear) and into the rotor housing..

The seal behind the fork drive is also replaced during a GTT PTO rebuild. We also strongly recommend a new water pump is fitted at the same time.

When coolant breaks into the PTO it severely corrodes the rotor drive shafts oil seal face. Leaving water/coolant inside will rapidly rust! remove right away and get rebuilt!

All New “GTT Fork Drive Pro” — Supercharger to Waterpump Drive

This has been designed with over 50% less rotational play/backlash when mated to the water pumps “fork drive”… as many will know the OEM one gets very worn from this over time and becomes both noisy and unserviceable.

Manufactured from top spec high carbon toughened steel  and plated to protect against corrosion.

This is a Exclusive optional extra item we install with GTT PTO PLUS Rebuilds.

Note: some cases might be mandatory to replace if your OEM one has worn.

£29+vat Extra (installed only)

Over the years we have seen  many Supercharger which many of the OEM PTO Drive forks needed replacing.

They fail/wear from years of backlash against the waterpumps counter-part “fork drive” due to having excessive rotational Tolerance “play” which causes friction when changing speed of the supercharger + every time the engine started…. this eventually makes the two fork drives both wear a “sloped” contact area resulting in making them push away from each other…. which results in horizontal end that damages both the PTO Plate bearing/seal and waterpump.

As our “GTT Fork Drive” have a  tighter tolerance to the waterpumps, this will significantly reduce/stop this occurring.

See images on the article by clicking here


Supercharger Rebuild FAQs

Rebuilds are normally completed within 48hours after payment is received. You can also Pay in advance via website for a faster turnaround time (we will prioritise you)

Payments can  be made via GTT website (select your spec) here.…/minig…/mini-g1-supercharger-rebuild/

UK rebuilds are returned via 1 working day courier and international via Express. (postage charged on website is return shipping….we do not collect your parcel)

Please ensure you put your contact details in the box (Inc. email address) and package very well.
Remove waterpump and large Air outlet “horn” from top of sc.

Yes we rebuild SCs received from all over the world.

Send to: GT Tuning LTD, Unit 10 Uplands Way, Blandford Heights, Blandford Forum, Dorset DT11 7UZ (united kingdom)

Ensure non UK units are sent with the correct customs info (we are not taking ownership of the unit, therefor we do not pay import duties or tax for this) Tax of  the rebuild service/ new items will be paid by customer where applicable when returned to customers country.

SCs are returned ready to install with oil inside!

If you are unsure what rebuild you want or require, we will usually inspect within 1 working day and email you with our findings.

Yes we rebuild SCs received from all over the world.

We have been rebuilding SC for over 6 years and well over 600 units.
They are a well proven success / solution. We are the original Mini SC specialist who were determined to fully understand the cause, symptoms and create the ultimate rebuild solution that will always be far superior to DIY kits & “new on the Scene” / claimed Generic Sc Gurus” That copy our research and articles to fool you of an equal standard.

Please see all our articles below from nearly 18years of experience with the R53 & 6 years of rebuilding SCs.

If you ignore your SC service/inspections you WILL risk the unit being US (unserviceable) + risk of catastrophic engine failure (from no water pump drive)

Rebuilds are the most cost effective time to replace the SC pulley for a reduction and the most beneficial mod for the Supercharged Mini with approx. 25-30BHP gain! (Free installation with GTT Snout Rebuilds!)

We will only reinstall OEM and GTT pulleys if pulley is removed. (Clamp on types will be returned loose) As we do not recommend them due to the damage they can cause. (See article)

All SC need rebuilding regardless of mileage. This is mostly due to the age of the supercharger being at least 10-15 years old and the standard inferior internal oil seals perish.

For enquires email:


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