Swapping from mechanical disc to hydraulic

[fatblokish]

My son has today acquired a second-hand bike with a truly woeful mechanical disc brake on the rear. Less effective at braking than rubbing a lollypop stick on the tyre.

The bike is a Scott Sportster P2, V brake on front which works well enough, with a Deore V brake lever controlling a Tektro mech brake on the rear.

What can be done to remedy this? Is swapping the mechanical for a cheapo hydraulic possible?
The bike is well set-up by a friend who is highly competent.

Your thoughts please...

 

[S-Express]

What can be done to remedy this? Is swapping the mechanical for a cheapo hydraulic possible?
The bike is well set-up by a friend who is highly competent.

What caliper is it? There are lots of perfectly good cable operated calipers, but there are also some pretty bad ones.

 

[fatblokish]

Okies,
piccys attached. As a cyclist stuck in the eighties I am very familiar with rim brakes, and know nowt about these new fangled disc jobbys.

Can I keep the existing levers? And the rotor? What bits do I need to buy?

HELP!

 

[bikingdad90]

If you stay mechanical you can get something like a TRP spyre or avid bb5 or 7.

You can also go "hydraulic" but cable actuated you could use TRP HY/RD or Giants own system.

If you go full hydraulic you need to check hose lengths as the system is all one.

 

[fatblokish]

If you stay mechanical you can get something like a TRP spyre or avid bb5 or 7.

You can also go "hydraulic" but cable actuated you could use TRP HY/RD or Giants own system.

If you go full hydraulic you need to check hose lengths as the system is all one.

Whoa! This poses so many questions!
Cheap is good. The bike will be stored outside in all weathers and, sadly, likely to be neglected.

OK, here come the questions...

For a hybrid system, the options you mention are well out of my budget

For a like for like mechanical replacement

1. Will I need to replace the existing brake levers? If so, what do you recommend, again, cheap is good?
2. Will replacing a mechanical system "like for like" with Avid BB5, (being cheaper than BB7) solve the current rubbish braking problem or just perpetuate them?
3. How can I be sure that the new caliper will:
   1. Fit onto the existing bosses (or whatever these new fangled orifices are called)
   2. Suit the rotor?

For a hydraulic system

1. As 1 above
2. As 3 above
3. Can I approximate the cable length needed with a bit of string following the line of the existing cable run or is a more precise measurement needed?
4. Will I need a Disc Brake Caliper Adaptor? If so, what would you recommend?
5. What hydraulic calipers would you recommend?
6. The hydraulic disc brakes shown on wiggle do not seem to be "all in one", i.e. only the calipers are shown. If I establish the hose length using 3 above, is there an option to buy all in one?
7. What else doe this ignoramus need to know? Bleedin 'ell!

thanks, in anticipation...

FB

 

[djb1971]

Avid bb5 plus a pair of speed dial levers. The levers work discs and v. so the levers will match. Levers £13pair, calliper £20ish

Just check the disc size on rear when you buy calliper, mounts are for 160mm/180mm etc.

You may as well change the cable inner and outer too. BB7 mountain have more adjustability and easier to adjust.

 

[djb1971]

get googling for cheap prices

http://www.wiggle.co.uk/avid-speed-dial-7-brake-levers-pair/
http://www.wiggle.co.uk/avid-bb5-mtb-disc-brake-is/

 

[Ajax Bay]

a second-hand bike with a truly woeful mechanical disc brake on the rear. . . . The bike is a Scott Sportster P2, V brake on front which works well enough

What are you worrying about the rear brake for? This bike has a V-brake you're content with on the front. If you put an effective brake on the back it will just lock up on you all the time. If I was going to put a decent disc brake on the bike I'd convert the front (forks and wheel as well), but you've implied the cost of that would put it 'out of scope'. Soldier on.

 

[Pale Rider]

The only sensible upgrade is Shimano hydraulics.

They come complete, pre-bled, so in most applications will bolt straight on.

Hose length can be a consideration, but if you think about it the distance between lever and calliper is roughly the same on most flat bar bikes, there's some slack anyway, so provided you are not over-fussy about the length of the hose loop by the handlebar, there will be no need to alter the length of the hose.

Having said all that, I agree the rear does so little braking it's hardly worth worrying about unless it doesn't function at all.

 

[Venod]

Can you ditch the disc and put a v brake on the back ? will the rim take a brake? is the frame set up to mount a V brake?

 

[S-Express]

If you put an effective brake on the back it will just lock up on you all the time.

Why will it do that?

 

[Ajax Bay]

Because you will be using mainly the front brake to decellerate and the weight on the rear wheel will reduce the harder you brake. So if you also brake hard on the rear it will lock up. If you don't need to brake hard, then you won't be using your rear brake. I'm not saying you don't need a rear brake, I'm saying having a back brake which is much more effective than the fitted front brake is not a good arrangement. If you want better braking, fit a better front brake as the first action.

 

[fatblokish]

[QUOTE 4668129, member: 45"]BB5s are rubbish. Get Shimano hydraulics.[/QUOTE]
summat like this? https://www.sjscycles.co.uk/brakes/...ake-caliper-lever-assembly-with-1700-mm-hose/

or this? https://www.evanscycles.com/shimano-m425-hydraulic-disc-brake-EV291384

or this? http://www.tredz.co.uk/.Shimano-Acera-BR-M395-BL-M425-Disc-Brakes_98140.htm

 

[djb1971]

[QUOTE 4668129, member: 45"]BB5s are rubbish. Get Shimano hydraulics.[/QUOTE]
They're not rubbish if they're set up correctly.

I've ran bb5 and bb7 on various fat bikes without issue, the speed dial levers work well with them.

The op isn't techy enough on discs and swaying him to hydraulic could cause more issues for him.

 

[Jody]

I would recommend shimano hydraulic also. Don't worry about shortening the length as they can be done in 10 minutes without needing a rebleed.