GT85 Bike Disc Brake Cleaner does a good job of cleaning up disc brakes, and it's nice to use as well.
If you run disc brakes, you need to look after them. Discs are not (contrary to many people's belief) a fit-and-forget solution. Just as rim brakes need regular cleaning and maintenance to remain in good working order, so do discs. GT85 cleaner is a good option as part of this regime.
Coming in a 400ml can with a fixed nozzle, GT85 is about mid-range price-wise. You can pay less for bulk automotive-grade disc cleaner, but that could be a false economy if the harsher chemicals mean you prematurely erode your frame or brake components or surface finish. GT85 has been extensively tested by the WD40 – its parent company – R&D labs and bike brand Raleigh, and formulated with just the one active ingredient to be as kind to your bike as possible while still doing the job. WD40 says that the GT85 Bike formula is less aggressive than cleaner designed for use on cars and motorbikes, as the parts and seals on bikes are more susceptible to chemical damage.
After a period of use any disc brake will collect mud, road film including diesel, petrol, rubber, brake dust, oil, chain lube, bike wash, cow poo and a host of other substances, all of which will become baked into the overall rotor-pad surface at hundreds of degrees. This will degrade performance and induce noise – at which point your brakes will benefit from a 'reset'.
Resetting bike disc brakes consists of removing the rotor and pads, then giving both a good going over with a fine-grit sandpaper to remove all trace of the old glaze. I use 260-grit, and it takes about a sheet to do both sides of one rotor plus pads. You want to get all the old shiny glaze off. Then the GT85 cleaner comes into it – a solid blast both sides of the rotor, plus the pads, to remove all trace of the scoured-off brake pad material. GT85, being almost totally isopropyl alcohol, doesn't smell offensive and dries very quickly. The 'blast pressure' is higher than I've experienced with other brake cleaners, and certainly shifts stubborn filth.
Going off the shake test to see how much was left, I reckon you'll get maybe 8-10 full brake-reset cleanups out of a can. On the back of the can it recommends it can be sprayed into the calliper itself - while on the bike, wheels and all. As a preventative quick going-over after a deep bikewash it's not a bad plan if it helps prolong brake performance. You're probably looking at 10p per blast, so money well spent if it keeps things quiet and grippy.
Overall, GT85 Bike Disc Brake Cleaner is a good option for keeping your disc brakes in good order.
It smells OK, shifts stubborn dirt, and is kind to your bike. For the price, it's a good option
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road.cc test report
Make and model: GT85 Bike Disc Brake Cleaner
Size tested: 400ml
Tell us what the product is for, and who it's aimed at. What do the manufacturers say about it? How does that compare to your own feelings about it?
DISC BRAKE CLEANER
Formulated to remove brake dust, dirt, oil, brake fluid and other contaminates from the surface of your disc brake rotors. Its fast acting formula dries quickly leaving no residue.
Tell us some more about the technical aspects of the product?
Appearance: Clear, colourless liquid with a characteristic organic odour.
pH: Not applicable, non-aqueous
Specific Gravity: app. 0.710 at 20oC
Viscosity: Thin free flowing liquid. Extremely volatile.
Active Content % m/m,
as supplied: > 90
Flammability, as supplied: Extremely flammable, flash point below -20oC
Composition Data, as supplied: A solution of naphtha (petroleum), hydrotreated light and
iso-propanol with carbon dioxide propellant.
Service temperature: Designed for use at ambient temperatures only
The nozzle on the top of the can is well made and delivers a good jet.
Got 'em (non) squeaky-clean.
£8 RRP for 400ml seems about midpoint in the market.
Tell us how the product performed overall when used for its designed purpose
Pretty well, actually. Quite happy with it.
Tell us what you particularly liked about the product
The power to shift dirt, and the lack of strong odour. Managed to use it indoors, with no nasty effects.
Tell us what you particularly disliked about the product
Did you enjoy using the product? Yes
Would you consider buying the product? Yes
Would you recommend the product to a friend? Yes
Use this box to explain your score
I might have appreciated a longer removable nozzle, for on-the-bike application without having to remove the wheel. That said, if you are cleaning your bike, it's best to take the wheels off anyway. Also, £8 for how long it lasts could get pricey if you are heavy-handed.
About the tester
I usually ride: Merida Ride 5000 Disc My best bike is:
I've been riding for: Over 20 years I ride: A few times a week I would class myself as: Expert
I regularly do the following types of riding: cyclo-cross, club rides, general fitness riding, mountain biking, Dutch bike pootling