Replace Giant MPH disc brakes – mount compatibility

I had a few questions about sizing and IS vs post mounts for replacement disc brakes.

I will be getting hold of a Giant XtC SE bike (approx 5 years old) from my uncle if we are ever allowed to go outside again. The disc brakes need replacing as he has had numerous issues with the Giant MPH Hydraulic Disc Brakes that come as standard. Because this is mainly for my partner to get into riding I didn’t want to spend loads so was going to pick up a front and rear set of Shimano Deore BR-M6000 Disc Brakes from Merlin bikes. However, I am unsure of the compatibility of the brake mounts and size of the brakes.

Do I need an IS mount to post mount adaptor or a post mount to IS adaptor? If so, what size? Or how do I work this out? Will I need to by new rotors as well? How do I know what size rotor to buy?

Any help or advice would be much appreciated and if anyone has suggestions about alternative brakes that would be easier to fit then I’m all ears.

At 5 years old I’d suspect PM fork and IS frame. Without knowing what the current calipers are it’s hard to advise however the calipers are likely to be PM both front and rear. This will probably mean you can just swap the brakes out and use the adapters and discs already there. However till you know exactly what’s there it’s hard to say. Can you get photos from your uncle showing the brakes?

Are they the ones with the thumbwheel pad adjuster? They’re based on the old Hope C2s, they have a tendency to seize on if left sitting for a long period. Pretty sure they were all I.S. mount calipers with an adapter for a post mount fork. So you’ll need an I.S. adapter for the rear at least, maybe for the front depending on fork mount/disc size. If they are the later Tektro based ones, you should be able to just bolt the new brakes straight onto the existing discs and adapters.

Thanks for the help. I’ve got links below to pics, I apologise for the rust….

Pics of front and rear

From what I can figure out, these are IS mounts with no adaptors present. So I would need a I.S. to PM adaptor for both front and rear. Correct?

@jabbi what do I need to get my uncle to measure to check the fork mount/disc size?

And how to I decipher these codes? LifeLine Disc Brake Adaptor – IS to Post

Yeah you’ll need IS to PM adapters front and rear. They look like 160mm rotors both ends. You should be ok to keep those however rotors are cheap so I’d be tempted to replace.

From the age of those brakes I think the bike is a ‘bit’ more than 5 years old. The forks also look like old marzocchis (definitely 26″). Think the real age is more like 10-15 years.

I’d also be tempted to save the pennies and buy a full set like these Clark m2s https://www.merlincycles.com/clarks-m2-hydraulic-front-rear-disc-brake-set-160mm-123106.html or perhaps the cheaper Shimanos (M395). If your partner is a new rider then the deores are overkill and twice the cost (when you add mounts and rotors). If they get into it I’d bet you’ll quickly be looking at a new full bike anyway so would be unlikely to move them onto another bike.

I have more information!

Rotor diameter – 170mm
Approx distance from one bolt to the other – 50mm

Put a 180 disc on the front as like others have said u need an IS post adapter. Pretty sure I’ve got one, possibly for rear too and can post to you if needed, also got a 180 rotor I’m sure.
msg me if interested.

They are IS mount.

If you want to fit Post mount calipers you need post mount adapters for an IS frame/fork. Like these (depending on disc size).

FYI a Post/IS 180 front mount is the same as a Post/IS 160 rear.

If they are an odd disc size it might be easier to buy new disc rotors so you can use readily available mounts.

Yes, definitely I.S. calipers both ends. I think the best bet here is mentioned above, Clarks M2, come with a 180 f 160 r rotors and I.S. adapters to suit, they’ll bolt straight on. I’ve fitted plenty to customer bikes as they work out cheaper than a seal kit + fitting from some brands! Seem to work well enough and the price is amazing!

Thanks all for the help, I made an account to post the question and have been blown away by the community support! I’ll be sticking around.

I’m gonna go for the Clarks M2 with the 180 front rotor, 160 rear.

Cheers. J

@nixie – you are correct. The bike was bought in 2005, not 5 years old as I suspected, so you were spot on with your estimate. Just thought you should know. It has also made me go for the cheaper option.

I am considering replacing/upgrading the forks but will see what sort of condition they are in when I get hold of the bike. It has not been regularly used but the sheer age will probably cause numerous degrading issues, so unsure if it will be worth spending anything more on it as opposed to buying a new bike all together. I assume posting a new thread for advice about this would be best?

@jplo depends which marzocchi model it is. The really cheap ones weren’t great, the mid price ones would be ok for a beginner (assuming its an air model and you can tune the spring rate to the rider, if its a coil spring then not a lot you can do). They are mechanically very simple so an oil change would not be a big deal. Realistically though a bike of that age should be considered a gateway drug. If your partner gets on with riding then even a lower end current model will be way more capable so I’d be reluctant to throw money at it.

I recently replaced some Giant MPH brakes with the Clarke’s ones listed above. Everything came in the box and bolted straight on 🙂