Bosch Motorsport M5 ABS Integration Kit for Ford Sierra Cosworth — in final development
A Bosch Motorsport M5 ABS integration kit for the Ford Sierra Cosworth is in 909’s development program now.
The Bosch Motorsport M5 ABS is a professional-level motorsport unit used in racing worldwide. It provides ultra-fast processing, highly accurate wheel slip control, and configurable ABS strategies for track use. Eleven selectable calibrations on a 12-position map switch allow the ABS behaviour to be tuned for tyres, surface conditions, and driving style.
Sierra Cosworths are still competing, and they are doing it on a braking system that is now closer to forty years old than thirty. On this car that isn’t just a calibration question — it’s the Teves Mark II, and the Teves is a problem worth understanding before you spend money on either side of the decision.
The Teves Mark II: why this car is a special case
The Sierra Cosworth doesn’t have a conventional brake booster with an ABS block bolted alongside it. It has a Teves (ATE) Mark II — an electro-hydraulic system that combines the master cylinder, the power assistance and the ABS function. Assistance comes from an electric motor-driven pump feeding a nitrogen-charged accumulator, with a pressure switch cycling the pump to keep the charge between 130 and 190 bar — Ford’s workshop figures for this car — and the warning lamp joining in once it can’t hold much above 100. There is no vacuum servo behind it.
That architecture is the source of both of the car’s well-known problems — and of one fact many owners don’t realise about their own brakes.
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The rear brakes have no conventional circuit at all. In a Teves Mark II the master cylinder serves the front wheels only. The rears are applied directly by boost pressure from the pump and accumulator, through a reducing valve — and the factory literature is explicit about what that means: lose the boost, and the brake system functions on the front wheels only, without assistance. A Teves on its way out isn’t drifting toward a heavy pedal; it’s drifting toward unassisted, front-axle-only braking. Ford’s own bleed procedure makes the split plain: the fronts bleed like any conventional car with the ignition off, but the rear circuit only bleeds with the ignition on and fluid arriving at pump pressure — under a capitalised warning in the workshop manual about how hard it arrives.
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The system is spread across the engine bay. On a right-hand-drive Sierra the actuation assembly — master cylinder, booster, pump, accumulator and reservoir together — hangs on the bulkhead ahead of the pedal, while the ABS valve block sits remotely on the other side of the bay: low on the left, beneath the inlet manifold, bracketed off the inner wing beside the chassis rail, with hard lines running between the two. Ford’s procedure for getting the valve block out goes in through the passenger-side front wheelarch with the liner removed. Every joint in that run is a forty-year-old sealing surface, living in the corner of the bay where the road grime settles.
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The accumulator loses its charge, and can’t be recharged. The nitrogen is retained by an internal elastomer element that degrades with age, and the unit was never designed to be re-gassed. As the charge goes, the pump runs more and more often to compensate, the ABS and brake warning lamps start appearing — classically flickering together as you press the pedal — and the pump motor gets worked to death covering for it.
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Failures cascade into the electrics. Internal seal leakage can put brake fluid where the motor is, which ends the motor. On Sierras specifically, corrosion in the connections around the reservoir and pump is a common fault in its own right, courtesy of where they live in the engine bay.
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Parts have largely stopped. Most Teves Mark II components are long out of production. Repair is possible through specialists, but it is increasingly difficult, increasingly expensive, and it ends with a rebuilt 1980s unit rather than a solved problem.
The master cylinder and booster go too — and that’s part of the kit
Because the Teves provides the power assistance and the master cylinder as well as the ABS, this conversion can’t simply swap one ABS unit for another. All three functions have to be re-established — including the rear brake circuit, which in the factory system exists only as boost pressure from the unit itself.
So the Sierra kit includes a 909 master cylinder and booster upgrade, developed to the same standard as the rest of our hardware: bolt-in, no holes drilled, fully reversible. It uses what the car gives you rather than cutting the car to suit the parts — the same approach behind every 909 kit. The exact specification is being finalised through development and will be published here once it’s locked; we’d rather name the parts when they’re confirmed than describe something that might still change.
Already running a pedal box?
That’s absolutely fine, and it’s a common state for these cars — plenty of Sierras have been converted over the years, precisely because the Teves eventually forces the question. A car already on a pedal box has solved the master cylinder and assistance side in its own way, and there is nothing about that which works against a motorsport ABS conversion.
Tell us what’s fitted and how it’s plumbed when you get in touch, and we’ll tell you what carries over and what doesn’t.
This is also why the usual objection doesn’t hold on this car. On most platforms, deleting the ABS is a plug and a blanking plate, and a motorsport conversion is clearly the more expensive path. Here, deleting the Teves also means fitting a master cylinder and a booster or pedal box, plus the plumbing to suit — the same class of work, in the same part of the car. If the Teves is going to need dealing with eventually, and on these cars it does, the real question isn’t whether to spend the money. It’s whether you finish with a competition car that has no ABS and a replacement master cylinder anyway, or one running current, in-production Bosch Motorsport hardware with eleven selectable calibrations and brake balance set deliberately in hardware.
Developed on our own cars — a Mk1 and a Mk2
This one isn’t being engineered from measurements and goodwill. 909 owns both a Mk1 and a Mk2 Sierra Cosworth, and the kit is being developed on them — which means the Teves comes out, the master cylinder and booster arrangement gets fitted and driven, and the sensing gets proven on cars we can put back on the hoist whenever something needs another look.
Having one of each matters more than having two of anything. Fitment questions that would otherwise be answered by guesswork or by a customer’s car on a deadline get answered properly in our own workshop, on both platforms, before anything is offered for sale.
It’s the same way the GT-R kit came about, and it’s the reason we’re prepared to talk openly about what this conversion actually involves rather than describing it in general terms.
In final development
The Sierra Cosworth integration kit is in 909’s development program now. Register your interest and be first in line for fitment details, pricing and the first production kits — and tell us about your build; development cars occasionally get early access.
Development is covering the full conversion — the M5 installation and the 909 master cylinder and booster upgrade that replaces the Teves. Both will be specified here when they’re locked.
When you get in touch, tell us what the car currently runs: an intact Teves Mark II, a failed one, an earlier conversion to a separate master cylinder and servo, or a pedal box. All four are common on these cars now, and they are genuinely different starting points for the installation.
What a 909 integration kit means
Across our released platforms, a 909 kit is the vehicle-specific engineering around the Bosch Motorsport M5: wheel speed sensing designed for the hubs and axles the car actually runs, hydraulic unit mounting in a location we have tested, cabin hardware bracketed rather than improvised, and calibration support behind it. That is the standard the Sierra kit is being developed to.
On every 909 kit, brake lines from the master cylinder to the hydraulic unit are made to suit the vehicle at install — 909 specifications call for Goodridge or Speedflow hardware.
Technical Specifications – Bosch Motorsport M5 ABS
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Control Strategy: High-speed multi-channel wheel slip control
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Maps: Eleven selectable calibrations on a 12-position map switch
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Inputs: 4x wheel speed sensors
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Outputs: Hydraulic modulation via Bosch Motorsport valve block
Bosch Motorsport M5 vs the factory Teves Mark II
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Factory Teves Mark II |
Bosch Motorsport M5 ABS Kit |
| Technology |
1980s electro-hydraulic ABS with integrated master cylinder and power assistance |
Modern, high-speed multi-channel motorsport ABS |
| Processing Speed |
Limited, slower ECU response |
Ultra-fast ECU with real-time wheel slip control |
| ABS Maps |
Single, fixed map |
Eleven selectable calibrations for different tyres and conditions |
| Master cylinder and assistance |
Both generated by the ABS unit itself — pump, pressure switch and nitrogen accumulator |
909 master cylinder and booster upgrade included — separate from the ABS, bolt-in, no drilling, fully reversible (specification to be confirmed) |
| Known failure modes |
Accumulator loses its nitrogen charge and cannot be recharged; pump motor overwork; fluid ingress to the motor; corroded reservoir and pump connections |
Current production hardware, in service across international motorsport |
| Parts availability |
Most components out of production; specialist repair only |
Current Bosch Motorsport supply chain |
| Brake balance |
Fixed proportioning |
Set deliberately in hardware, with slip controlled at each wheel from that baseline |
| Driver Control |
None |
Driver-selectable map switch, adjustable between sessions |
| Performance |
Adequate for road use in period; limited under hard braking/track |
Motorsport-level braking performance for the track |
FAQs
Q: When can I buy one?
A: The kit is in final development and pricing has not been released. Register your interest and we will come back to you with fitment details and timing as soon as they are confirmed.
Q: My Teves is still working — is it worth doing anything?
A: It’s worth knowing what’s ahead. The accumulator’s nitrogen charge is held by a component that degrades with age and cannot be replenished, so a working Teves is a working Teves for now. If the car is competing, the calibration is a separate argument again — a 1980s road ABS map has nothing to do with the grip a modern tyre gives you.
Q: Can I just remove the ABS and run without it?
A: You can, but it isn’t the cheap option people expect. The Teves unit is also your master cylinder and your power assistance, so removing it means fitting a master cylinder and a booster or pedal box, and plumbing to suit. That work is common to either path — which is why a motorsport conversion on this car is worth pricing properly rather than assuming it’s the expensive one.
Q: Does the kit include a replacement master cylinder and booster?
A: Yes — because it has to. The Teves performs all three functions, so a 909 master cylinder and booster upgrade goes in alongside the M5. It’s being developed to the same standard as the rest of our hardware: bolt-in, no holes drilled, fully reversible. The specification is being finalised through development and will be published here once confirmed.
Q: My car is already on a pedal box — is that a problem?
A: Not at all. Plenty of these cars have been converted, and a pedal box car has already solved the master cylinder and assistance side in its own way. Tell us what’s fitted and how it’s plumbed and we’ll tell you what carries over.
Q: My car’s Teves has already been converted to a normal master cylinder and servo — does that help?
A: Often yes, and it’s a common starting point now. Whether your existing setup carries over depends on what was fitted and how it’s plumbed, so tell us exactly what’s on the car when you get in touch.
Q: Which Sierra variants will it suit?
A: Development is running on our own Mk1 and Mk2 cars, so both are in scope from the outset. Exact fitment detail is being confirmed as that work completes. Register your interest and tell us which car you have and what it currently runs — it genuinely informs where the work goes first.
Q: I’m building a car now — can it be a development car?
A: Possibly. Get in touch and tell us about the build and how the car gets used. Development cars occasionally get early access.
Q: Will installation need brake lines made?
A: Yes. On every 909 kit the lines from the master cylinder to the hydraulic unit are made to suit at install. Professional installation is recommended, and we can install and commission in our Newcastle workshop.
Q: Can you ship overseas?
A: Yes. 909 vehicle-specific kits ship worldwide. Contact us for freight to your country.
Q: Is the system validated for road use?
A: No, Bosch Motorsport ABS is for track usage only.
