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Verdict: 
It smells OK, shifts stubborn dirt, and is kind to your bike. For the price, it's a good option
Weight: 
378g
GT85 Bike Disc Brake Cleaner
8 10

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.

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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'.

Glaze away

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.

> Check out more reviews of bike cleaning products here

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.

Verdict

It smells OK, shifts stubborn dirt, and is kind to your bike. For the price, it's a good option

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?

GT85 says:

DISC BRAKE CLEANER

400ml

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?

Ingredients:

C8-9 ALKANE/CYCLOALKANE

ISOPROPYL ALCOHOL

CARBON DIOXIDE

TECHNICAL DATA

Physical Properties

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

Rate the product for quality of construction:
 
8/10

The nozzle on the top of the can is well made and delivers a good jet.

Rate the product for performance:
 
9/10

Got 'em (non) squeaky-clean.

Rate the product for value:
 
5/10

£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

Nothing, really.

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.

Overall rating: 8/10

About the tester

Age: 43  Height: 183cm  Weight: 72kg

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

17 comments

Avatar
rtw [23 posts] 10 months ago
1 like

Does anyone actually do this?

Avatar
kwi [294 posts] 10 months ago
1 like
rtw wrote:

Does anyone actually do this?

Clean discs?  Yes, though with a rag soaked in IPA. (As in Isopropyl alcohol not India Pale Ale.)

 

Edit: Just read this is Isopropyl in a spray can, go to chemist and buy it a lot cheaper.

Avatar
Mungecrundle [662 posts] 10 months ago
2 likes

Apparently the master swordsmiths of old (presumably the evil ones) would temper the steel by running the red hot blade through a prisoner and quenching it in their blood.

I thought that disc brakes worked the same way. They don't really seem to operate at their best until they have severed an artery or two.

 

 

Disclaimer: This is no worse than some of the other crap posted about disc brakes.

Avatar
guyrwood [755 posts] 10 months ago
0 likes

I use the car stuff from Screwfix, less than 2 quid a can...

Avatar
bikebot [2120 posts] 10 months ago
0 likes

If you're removing the disc to clean it, why does it matter whether the ingredients are kind to the frame?

Avatar
guyrwood [755 posts] 10 months ago
0 likes

You don't need to remove it. I spray bog standard brake cleaner onto a clean cloth and clean the discs in situ. No need to get any of it near the frame.

Avatar
Man of Lard [324 posts] 10 months ago
1 like

I just use mine... not had any glazing or other issues in 20000km across 3 bikes (with mechanical and hydraulic discs)... the most they ever get is a wipe with a damp cloth when I have the wheel off for any reason.

Avatar
sidesaddle [91 posts] 10 months ago
0 likes

Baffled that in 40 years of motorcycles I have never once felt the need to 'clean' a disc. Skim it when it's scored maybe, but this is snake-oil, almost literally.

Avatar
mike the bike [887 posts] 10 months ago
3 likes
sidesaddle wrote:

Baffled that in 40 years of motorcycles I have never once felt the need to 'clean' a disc. Skim it when it's scored maybe, but this is snake-oil, almost literally.

 

You should be ashamed Mr Sidesaddle.  As everyone knows, the recommended servicing schedule for disc brakes involves :

Taking a small section of the Turin shroud.

Soaking it in angels' tears and then ...

Wiping away all bits of squashed frog from the surface of the disc.

 

Not too much to ask, is it?

 

Avatar
guyrwood [755 posts] 10 months ago
1 like

Car and motorbike discs get hot enough in use to get the diesel and other road crap off them whilst road discs rarely do. I know when mine get a bit yowly, a good clean quietens 'em back down.

Avatar
the infamous grouse [55 posts] 10 months ago
0 likes

to clean sintered or semi-sintered disk pads; remove, spray with window cleaner, wait, wipe off glaze, rinse with water.
to clean discs; remove, spray with dettol mould+mildew remover or mr muscle oven cleaner, wait, wipe off glaze, rinse with water.

of course you need to do the bedding-in thing afterwards, which is the biggest faff.

Avatar
KiwiMike [1282 posts] 10 months ago
0 likes

Wow - didn't see that coming. Thought I was reviewing bike-friendly disc brake cleaner, not a second referendum proposal.

A few facts:

The only way to get baked-on brake pad residue off of steel rotors is fine-grit sandpaper, or some sort of acid etching. It's damn hardy stuff.

What brake pad material reacts against is NOT bare steel, rather the brake pad material that has bonded to the rotor. a new, pristine rotor is next to useless until bedded/burnt in. 

This process of cleaning up everything then braking hard down a hill multiple times is non-negotiable if you want the best performance. Read up on two decades of bike-disc wisdom.

If you have spilt anything on your rotors or pads apart from pure water, and it's then been baked in at hundreds of degrees you need to get it off, or performance will suffer. This is simple physics.

I accept that some will be happy with this, and will therefore think the level of braking they have enjoyed over the last 10,000km+ is both optimal and acceptable.

The idea you would go to the trouble of skimming a £15 rotor is ludicrous. Spending 10 minutes removing, sanding and re-torquing a rotor is not. Have a cuppa and pop on a decent bikey podcast like Velocast or Cycle Systems Academy. You're welcome.

Yes the car stuff is cheaper. It's also full of more aggressive chemicals that a car/motorbike's undercarriage is immune to, but a paint or decal finish on a bike frame possibly won't be. Your bike, your choice.

It is very hard (I'd say impossible in the UK) to buy Isopropyl Alcohol in a chemist. Let alone in aerosol can form. I had to go to eBay to buy just 100ml of the liquid stuff, as chemists simply don't sell it anymore.

 

Happy braking folks!

Mike

 

 

 

Avatar
Langsam [49 posts] 10 months ago
0 likes

Maplins stock aerosol IPA, and it's cheaper than the GT85 can.

 

 

Avatar
KiwiMike [1282 posts] 10 months ago
0 likes
Langsam wrote:

Maplins stock aerosol IPA, and it's cheaper than the GT85 can.

 

Their website begs to differ: the 200ml cans are £3.99, the 400ml ones £9.99.

http://www.maplin.co.uk/c/diy/cleaning-and-aerosols/electronic-cleaners

Plus pure IPA doesn't have the specific compound formulated to remove the brake residue. And whilst I haven't tested the Maplin stuff, given it's for use in servicing electronics it is highly unlikely to have the same blast pressure as the GT85 can. 

 

So it costs more, but won't be as good, chemically or physically. Genius  1

Avatar
. . [168 posts] 10 months ago
0 likes

I don't doubt the benefit of sanding discs and pads, but how does the performance of GT85 compare with non-spray IPA on a paper towel (my preferred method), or sanding alone?

Avatar
leqin [185 posts] 10 months ago
5 likes

your in a rush and you pick up the black can with the red top and spray your disc brakes.......... and then a few seconds later you start thinking what a complete and utter bunch of lemons must work at the WD-40 Company because they stuck all of their bike maintenance range in black cans with red tops........ just like GT85...... except GT85 doesn't clean brakes and you just sprayed teflon on yours.

Avatar
Dicklexic [65 posts] 10 months ago
1 like
leqin wrote:

your in a rush and you pick up the black can with the red top and spray your disc brakes.......... and then a few seconds later you start thinking what a complete and utter bunch of lemons must work at the WD-40 Company because they stuck all of their bike maintenance range in black cans with red tops........ just like GT85...... except GT85 doesn't clean brakes and you just sprayed teflon on yours.

 

Hahaha my first thoughts exactly when I saw the picture of the can! Personally I don't use GT85 oil for anything, but I'm sure plenty do, and a good dose of oil isn't going to help your brake function at all, except maybe stop them squealing!