Disc Brakes

[moon]

My disc brakes have never worked satisfactorily, needing adjusting every few days and now they are causing the front wheel to wobble.

Is there a fix for this, and is it possible to remove the disc break and replace it with the old fashion style brakes?

 

[Lloyd_50cycles]

It all depends what type you have. It sounds like a mechanical disc brake, with a single moving piston. The backing pad is probably coming loose, making them self adjust. This is fixable by removing the bolt that adjusts the backing pad and threadlocking it back in place(a common oversight most manufacturers make). This will stop it working loose.Note; please only use loctite, not sper glue Check nothing is loose, as nothing at all should be wobbling. If you can get a pic on here of your wheel/brakes/fork on here I'll have a look for you as there are several things that make fitting v brakes difficult on disc brake bikes. V brake bosses(mounts ) on the fork, and a v brake specific lever and rim.

 

[flecc]

Not knowing the disc brakes on your bike I can't help there, and in any case it's difficult to diagnose without actually seeing them.

The usual rim V brakes cannot be fitted since they need mounting points on the fork legs, but it's sometimes possible to fit the caliper types which bolt through the top centre of the fork where there's often already a hole for mudguard mounting. The rear one is also sometimes possible.

If you have a look at the link below, the top four are caliper types and the ones below are the V brakes you cannot have. The caliper types come in various drop lengths for different forks, but I'd strongly advise you consult a good independent cycle dealer about doing this modification, rather than attempting it yourself, unless you are absolutely certain of your ability.

Brakes at Wiggle

P.S. Posting crossed with Lloyd's
.

 

[ElephantsGerald]

Moon, since I think you have a Wisper 905SE Sport, your front disc will be a Promax disc of unknown model (at least I can't work it out, although it looks very much like a DSK 400 to me).

Popular opinion on the web seems to indicate that Promax disc are rubbish as far as I can tell. Comments welcome .

I can't say why your brakes are causing you trouble, but one of the reasons why folk seem to think they're rubbish is they're very difficult to adjust correctly (apparently).

If someone could tell me what the actual model number is I might be able to go looking for new brake pads for mine - grr!!

Regards,

Elephants

 

[moon]

Yes its the 905se brakes, I had them adusted at my local bike shop (condor cycles) and the wheel has been wobbling ever since, so much so that the handle bars pull to one side on every wheel revolution.

Does anyone know of the best possible sollution? should I take them back to the bike shop and ask them to sort them out...or is it better that they are reoplaced completely as I really cant rely on them at the moment.

I have some spare brake pads if you want a pair, Doug gave me a supply

 

[ElephantsGerald]

Its a Promax DSK 400

Dick Lai of WEVCO has just confirmed that the front disc on the 905SE Sport is indeed a Promax DSK 400.

I don't know if you've received it as well, but within the last 1/2 hour Doug Gosling @ WEVCO sent me an installation manual for the 905SE Sport, which gives details about adjusting the front disc brakes. If you don't have it, then I suggest you grab a hold of Doug and get him to send you a copy.

It sounds like your local bike shop might have done a duff adjustment. I'd take it back and whinge at them if I were you.

You should be able to get these brakes working properly, they're just a Mini Metro rather than a Rolls Royce of brakes, so you should only be thinking of replacing them if you want better brakes, not because you can't get them working at all!!

I've been in touch with Doug, and he's sending me some spare pads

Regards,

Elephants

 

[moon]

OK, I'll work with my local bike shop to have the brakes adjusted properly and hopefully I wont have to keep adjusting them every 2 days.

Just called them and they immediatley tried to sell me a new disk brake instead of fixing the problem....so I'm not going there again!!!

ho humm.....

 

[Phil the drill]

I had some difficulties getting these disc brakes to work well on my 905se. It is possible to get them to work OK, but they are a pain to adjust and go out of adjustment regularly. One of the problems is that they are supplied without having been properly set up and trued correctly to the disc. They often require careful shimming for this to be achieved, and this was certainly not the case on my bike.
Hopefully a good local bike shop should be able to sort you out, but if you decide to upgrade the disc at some stage the Avid BB7 is a very good, if slightly pricey choice. They are easy to fit, easy to adjust properly and they work very well. A revelation, I would dare to suggest to all who have struggled with their Promax's.

 

[moon]

Ok, thanks Phill, I've booked the bike into Evans Cycles so hopefully they can correct the original installation.

 

[Mussels]

I've found that if the Wisper disk brake is adjusted as close as possible in the workshop then they start to bind when they get warm in use. After adjusting them I then back off another 10 degrees to prevent this happening, otherwise I end up wondering why it's hard work to go downhill.
I also recieved the instructions today so hopefully this will help things.

 

[Wisper Bikes]

Brake Adjustment

Hi

Please email Doug at doug.gosling@wisperbikes.com and he will send you instructions on how to adjust the brakes properly, it is necessary to adjust from both sides to balance them or they will need to be adjusted often.

All the best David

 

[oregon]

Is it possible to replace the Promax brakes with the Avid if you have SKS commuter mudguards fitted? As I read somewhere that mudguards use the fitting that would otherwise be used by Avid disc bakes (calipher).

Sorry if I am not talking sense, I'm still trying to understand how all these things work!

Thanks

 

[the_killjoy]

Touch wood but I have not had any problems with the wisper front brake and the only adjustment I have had to do is the cable.

I don't know if it is just that all the bikes I have had in the past have had poor brakes or that people expect moped quality braking. I find them adaquate but haven't used them in the wet yet.

 

[Mussels]

Is it possible to replace the Promax brakes with the Avid if you have SKS commuter mudguards fitted? As I read somewhere that mudguards use the fitting that would otherwise be used by Avid disc bakes (calipher).

Sorry if I am not talking sense, I'm still trying to understand how all these things work!

Thanks

The disk brake on my Wisper and the front mudguard share the same fitting, just use a longer bolt.

Touch wood but I have not had any problems with the wisper front brake and the only adjustment I have had to do is the cable.

I don't know if it is just that all the bikes I have had in the past have had poor brakes or that people expect moped quality braking. I find them adaquate but haven't used them in the wet yet.

It depends what you need them for I guess, I ride very busy roads and if the brakes don't work well then I'll crash. They don't need to be moped strength as the bike is not as heavy but it still needs to stop just as well, otherwise it's not really safe for the roads.

 

[moon]

The thing is should a £1200 bike be fitted with cheap disc brakes that haven't been installed properly?

 

[frank9755]

The thing is should a £1200 bike be fitted with cheap disc brakes that haven't been installed properly?

No, it shouldn't, but in Wisper's defence, I don't for a second believe they knew the brakes were poor to begin with - rather it has emerged during use. I think new models now have different brakes.

It's not ideal but I think it is an inevitable part of the product development cycle - the penalty for having a new model is that there will be teething problems. The same still happens for cars despite all the investment in quality and much greater production volumes.

Touch wood but I have not had any problems with the wisper front brake and the only adjustment I have had to do is the cable.

I don't know if it is just that all the bikes I have had in the past have had poor brakes or that people expect moped quality braking. I find them adaquate but haven't used them in the wet yet.

The brakes actually work well, even in the wet; it's just that they need to be adjusted too frequently in order to keep them working well.

 

[Phil the drill]

Is it possible to replace the Promax brakes with the Avid if you have SKS commuter mudguards fitted? As I read somewhere that mudguards use the fitting that would otherwise be used by Avid disc bakes (calipher).

Sorry if I am not talking sense, I'm still trying to understand how all these things work!

Thanks

Hi
both the Promax and Avid brakes use the same bolt holes on the forks and yes, one of them is normally used for the SKS mudguards. I have these mudguards on my bike, but got around the problem by making up a small bracket from a thin piece of flat steel, bent in a right angle and drilled on each flat (I can post a picture if this helps). This is very easy to fabricate and allows you to bolt the mudguard fitting on to the threaded fitting on the rear of the fork leg, just above the disc brake on the left side. The right side can be mounted as normal. I prefer this route since I don't like sharing brake fittings with other items, especially for discs where an accurate stable set up is essential.
Hope this helps, Phil

 

[Phil the drill]

I think I'll take your advice on the Avid brakes, Phil. I'm quite sick of the Promax one. It can work well when adjusted but basically it needs adjustment pretty much every ride. Is this the one you fitted, with the 185mm rotor?

Hi Frank,
Basically that is the one I use, except that you want the 160mm rotor version, not the 185mm. 160mm is the size of the original Promax and if you fit the larger rotor then won't be able to get the calipers to fit onto fork legs!
The Avid's come with good set up instructions, and are straightforward to install, using exactly the same bolt holes as the Promax. They have a simple system for truing the caliper to the rotor precisely, without loads of fiddling about with shims (a hateful job!).
One word of warning though, once bedded in properly (which will take a few miles to start with) be careful not to 'slam' the anchors on as hard as you did with the Promax......these ones WILL stop you, pronto!
Cheers, Phil.
See below Frank, went to add to this posting and somehow accidentally double posted! See PS below please.

 

[Phil the drill]

I think I'll take your advice on the Avid brakes, Phil. I'm quite sick of the Promax one. It can work well when adjusted but basically it needs adjustment pretty much every ride. Is this the one you fitted, with the 185mm rotor?

Hi Frank,

Basically that is the one I use, except that you want the 160mm rotor version, not the 185mm. 160mm is the size of the original Promax and if you fit the larger rotor then won't be able to get the calipers to fit onto fork legs!
The Avid's come with good set up instructions, and are straightforward to install, using exactly the same bolt holes as the Promax. They have a simple system for truing the caliper to the rotor precisely, without loads of fiddling about with shims (a hateful job!).
One word of warning though, once bedded in properly (which will take a few miles to start with) be careful not to 'slam' the anchors on as hard as you did with the Promax......these ones WILL stop you, pronto!

Cheers, Phil.

PS Wiggle don't currently list the one you want, their 160mm rotor version is the road version which is not compatible with your levers, you need the MTB version. This is the one you need: Avid BB7 08 MTB Disc Brake with 160mm Rotor | Brakes Disc - Avid | Cycle - Cycle Sports UK - they also seem to be a bit cheaper than Wiggle too!

 

[Howard]

Thanks Phil - I'll be taking your advice on this one too. I have one of the new 905se Sport bikes, and the front brake really is useless!