changing to disc brakes

[Greg8]

hi
I have a spec rockhopper i think its a 2003/4 model it has manitou axel plus forks mavic m8 117 wheels roll x tyres shimano deore gears I havent had it long bought second hand I just use it for local bridlepaths, towpaths and delamere forest at weekends I would like to replace the v brakes with disc brakes as I think these would fare better in the wet I have my eye on some hope and avid disc brakes which are second hand on ebay would these fit ??

Also the fork adjuster which says less /more doesent have any effect on the fork travel so i presume these need a service ? Would this be something I could do myself ?.Thanks

 

[3narf]

It's difficult to know if they'd fit without seeing the forks/frame- does the bike have IS (industry standard) brake mounts, or just V-brake bosses?

To be honest, it might not be worth all the hassle. V-brakes are better imho. Just replace the pads with something like Kool Stops and they should be fine in the wet.

As for the fork adjuster; these things are largely marketing gimmics, so don't expect it to work any better after a service!

Hope the above helps and isn't too discouraging...

Enjoy your bike! My wife has a Hard Rock which is approaching 20 years old and is still absolutely fine.

 

[Panter]

As above, except I would add that disk brakes are a significant upgrade over V's.
It depends what you're riding, of course, but if you're out, regularly, riding through Winters gloopy mud then disk brakes are hugely better.
They don't clag up, require no adjustment and, of course, aren't constantly grinding away at your precious rims every time you brake.

I was (and still am actually) a huge fan of Avid brakes but having now ridden a few Hope equipped bikes, I'd be sorely tempted to have a good look at those

EDIT: I'm not familiar with your forks, but most manufacturers have extremely good service guides online

 

[battered]

A friend did this without trouble. Hydraulic discs are a huge improvement off road, cable operated discs less so. The things you need to check are that the whees have 6-bolt fixings for disc brakes (if not you need new hubs or wheels, costs ££) and that the frame and forks have mounting points for the calipers. If they don't then you will need new forks £££ and while a frame builder will fit carriers to a steel frame an ally frame is more difficult and in either case the costs are very high.

So, in short: if you have all the fixing points and the right wheels then it's just about economically viable. If not, sell the bike and buy one with discs on it. My Kona MTB was £250 ex hire, in great condition and fitted with loads of tasty bits, so if you think £100 for discs, levers and calipers and £100 back if you sell your old bike, a second hand one with everything you want already fitted makes a lot of sense.

 

[3narf]

As above, except I would add that disk brakes are a significant upgrade over V's.

I'm a technical snob! V-brakes are cheaper, lighter and simpler, the increase in mechanical advantage over discs is massive, and none of the braking force goes through the spokes, so the wheels can be lighter as well.

I have to concede there are a few practical advantages to discs (as mentioned above), but they are mainly fitted for marketing purposes, imo.

 

[Panter]

I'm a technical snob! V-brakes are cheaper, lighter and simpler, the increase in mechanical advantage over discs is massive, and none of the braking force goes through the spokes, so the wheels can be lighter as well.

I have to concede there are a few practical advantages to discs (as mentioned above), but they are mainly fitted for marketing purposes, imo.

Surely that's the other way round i.e the force goes through the spokes with V's but not with disks?

Either way, disks are far superior

 

[battered]

I can only conclude that 3narf doesn't ride off road or when it's raining and filthy.

(S)he is right though about brake forces, if you thinbk about it a disc brake stops the hub and the rim and tyre carry on turning, or trying to. The spokes take the force. A rim brake stops the rim and the tyre tries to carry on turning, so the force is between the tyre and the rim. The hub isn't aware of any of this, or the spokes. This is why rim brake bikes can have a radially spoked front wheel.

It's academic though, as spokes have to take pedalling forces on rear wheels.

The fact remains that if your rims are covered in mud and/or water then rim brakes don't work. Discs do. In addition, rim braked MTBs need new pads every couple of rides in wet and wintery conditions, and new rims after 2 years. A new disc lasts years and costs an awful lot less than a new rim.

 

[RedBike]

This one?
http://www.specialized.com/us/en/bc/SBCBkModel.jsp?arc=2003&spid=20993

I can't see the left hand side of the frame or forks. The chances are (This needs to be checked!) the frame as a disc mount but your wheels don't. So you would need new wheels.

Also your forks look like they might be 71mm post mount, whereas the Avids/Hope discs will more than likely be 51mm International standard. You can get adaptors, but its all additional cost.

There are possibly 3 dials on the forks with a +/-.

The most likely is a pre-travel. This controls how much the forks sag when you get on the bike. Or effectively how hard the forks feel. You want to set this so the forks sag approximately 1/4 of their travel when you're sitting normally on the bike.

Another dial (normally at the bottom of the legs) is the re-bound. This controls how quickly the forks return back to fully extended. If the rebounds to quick the forks will spring back after a bump uncontrollably, if its too slow the forks wont have return back to normal before you hit the next bump.

Lastly, Some forks have u-turn travel. This means you can increase the travel from say 100mm to 130mm. Your forks are unlikely to have this feature.

 

[3narf]

I can only conclude that 3narf doesn't ride off road or when it's raining and filthy.

If that can be your only conclusion, the process you used is flawed!

 

[Panter]

I can only conclude that 3narf doesn't ride off road or when it's raining and filthy.

(S)he is right though about brake forces, if you thinbk about it a disc brake stops the hub and the rim and tyre carry on turning, or trying to. The spokes take the force. A rim brake stops the rim and the tyre tries to carry on turning, so the force is between the tyre and the rim. The hub isn't aware of any of this, or the spokes. This is why rim brake bikes can have a radially spoked front wheel.

It's academic though, as spokes have to take pedalling forces on rear wheels.

The fact remains that if your rims are covered in mud and/or water then rim brakes don't work. Discs do. In addition, rim braked MTBs need new pads every couple of rides in wet and wintery conditions, and new rims after 2 years. A new disc lasts years and costs an awful lot less than a new rim.

Ah, of course, Doh!

 

[Alun]

Disk brakes for me on a MTB every time, I wore out a set of canti brake pads on one long wet gritty descent of the Mary Townley loop some years ago. They were in good nick at the top, knackered at the bottom, along with my nerves!

 

[battered]

Wasn't that with me Alun? Twas indeed a wet and gnarly descent, in fact a wet and gnarly day out all round.

 

[ColinJ]

Disk brakes for me on a MTB every time, I wore out a set of canti brake pads on one long wet gritty descent of the Mary Townley loop some years ago. They were in good nick at the top, knackered at the bottom, along with my nerves!

I did a similar thing. I tried to get 'just one more ride' out of a pair of brake blocks and my rim paid the price! What can you do when you are flying down a dangerous rocky descent and the last bit of rubber wears away - stop braking? I could hear my poor rim screaming for mercy, but it was a case of sacrificing the rim or me - not a difficult decision!

I really like the Hope C2 disc brakes on my Rock Lobster. The only problem is that they do suffer from overheating. I can back them off with thumb controls but when that isn't enough the brakes can actually lock on until they cool down.

One really scary problem with those Hopes is if I back the brakes off when they get hot and forget to readjust them when they cool down. Suddenly - no brakes!

 

[rob_mcp]

Rock hopper 2003 - Alex forks have oil filled tubes with greased pistons and can be compelely dismantled and rebuilt easily. the adjustment on them is not for length of compression but rebound, and i never found it made any difference really. you need correct fork oil, a micro grease gun and tube of grease. The instructions came with mine but they must be available on the web. however my supply of fork oil far out lasted the forks so think twice before going down the rebuild root, if they are well used they may be ready for replacement.
Disks should not be a problem as the forks and the RH frame should have the mountings, mine had disks from new, but i'm not sure that the vbrake ones had disk hubs - so it may be that the biggest expense without real gain is a new pair of wheels!

Best upgrades i've done to mine, xtr gear cable set, xt front mech (cos the deore one is pants), kmc chain

Most essential upgrades, seat post quick release for a hope one which doesn't slip while you are riding it, hope front skewer as the dodgy specialised one kept coming loose - always an unpleasant thing to discover halfway through a ride!

 

[Greg8]

Thanks for all your replys its given me a lot to think about the wheels would not changing in order to fit disc brakes the rotor bracket and little holes are present.

The bike is the base model really enjoying it at the moment (ask me again after a few wet and cold winter months! ) would like to keep it long term I think I need to invest in a good book or manual re maintenence/ upgrading .Thanks again Greg.