I have a 2003 Haro V3 mountain bike, and the 8 speed gearshift no longer works.

Additionally, the rim brakes are finicky and I wish to swap to disc brakes. Lastly the front fork is work out and no longer absorbs shock.

So all together I need a new fork and gear shift, and if it’s possible I’d also like to swap to disc brakes.

I’m new to bike modification, and I don’t want to buy any parts that won’t work with my bike.

Here’s a link to all the specs of the bike. The only difference is the seat, pedals, and handle bars have been changed.


  • Here's a link to a question on what's involved in converting to disk brakes bicycles.stackexchange.com/questions/4423/…. replacing the fork, gear shift and going disk will cost more than the bike is worth. A good used bike set up the way you want can be obtained.
    – David D
    Commented Oct 3, 2019 at 18:14
  • To me it looks like the frame and fork already have disk mounts, and the fork is going to be replaced anyway and V-brake levers are compatible with mechanical disks anyway. OP will still need disk-compatible wheels, though.
    – ojs
    Commented Oct 3, 2019 at 18:23
  • 2
    A new fork and wheels (for disks) along with disk brakes is likely to cost more than buying a new bike. Only do it if you have a reason to the bike other than financial.
    – mattnz
    Commented Oct 3, 2019 at 19:27

1 Answer 1


If you really want disc brakes, it's new bike time. If you are replacing the forks, at least half the drivetrain and the wheels (you need disc brake hubs, and if you need to replace hubs then you really need to replace the wheels), then with installation costs you will likely be paying a very significant fraction of a decent new bike. Even a lowish level Altus/Acera/Alivio equipped bike will be better than the Haro just due to how more advanced components have become over the years. Even the lower level Shimano groups have hydraulic disc brakes now.

If you are willing to stay with rim brakes, then replacing the fork and some of the drive train can make sense. When replacing the fork there are two main things you need to deal with:

1) The steerer tube diameter, and whether it tapered and has larger lower bearings. Likely it has a 1 1/8" straight steerer tube.

2) The fork travel and axle to crown distance. The axle to crown distance is important to preserve the steering geometry of the frame, but does not have to be exact.

With the drivetrain you'll need to decide if you want to replace just the rear derailleur and shifter, both front and rear, or the whole thing including the cranks. Shimano Altus/Acera/Alivio grouos are 9 speed, and better groups are 10 speed or more so you'll be replacing the cassette and chain. 9, 10 and 11 speed cassettes will fit on the freehub body of your wheel.

If you go for a 9 speed group then you can probably retain the current crank, but you should determine if the bottom bracket is worn out and needs replacement. If you go for a 10 speed group the current crank really will not work.

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