Tektro Lyra - Boardman CX Comp. Incorrect levers?

[SoloRider]

Hi, I've been having issues with the braking strength on this bike for a couple of months since I bought it. Scouring the internet I find many in a similar position.

Now, before I discard them and get the ubiquitous BB7s on there, I am keen to see if setup would make them acceptable and one thing got my attention from a particular post. Cable pull. Apparently poor performing discs are likely to be because of incorrect levers as much as anything else.

So I download a couple of pdfs from Tektro and sure enough it states clearly:

Warning - Tektro mechanical discs brakes are designed for use with linear pull(v-type) brake levers. Brake levers pulling less than 24mm of cable should not be used...

So, presumably the fitted Sora STi levers do not pull 24mm of cable. If this is the case, are Boardman bikes being negligent by fitting these brakes?

[531colin]

Have I got this wrong?
I think Vee brake levers pull the cable further but with less force.
Road brake levers generate more force but less travel.
So brakes designed for vee levers (low force) should throw you over the bars if used with road levers (high force).....?

.......in reality, I expect your brakes just need setting-up properly.
I did a short tour with a bloke on a Boardman CX bike with discs....it took several roadside sessions for me to get his brakes as good as my rim brakes, but somebody with more experience (of disc brakes) than me could do it quicker.

[SoloRider]

I've absolutely no idea Colin! I think discs are vastly overrated myself though. I had some good hydraulic Shimanos once but I still think that they require so much setting up (wobbly rotors anyone?) that I'd take some good quality Vs and put up with rim wear any day! My road bike rim brakes are also far more effective and easier to set up.

[RickH]

A couple of points

• Tektro/TRP do "road" discs which should work OK with road levers. It all depends what model is fitted as to whether there is a problem in this case.
  
  
• If you don't have much experience with cable discs, it is very tempting to try to adjust the brakes using the barrel adjuster as you would do with rim brakes but, particularly with "road" models where there is very little cable pull, this is potentially dangerous as you can adjust out pretty much all of the braking capability (the reason why barrel adjusters are often omitted). Apart from the taking up of any initial cable slack, adjusting discs should be done using the pad adjusters. Brakes should have specific instructions but a rule of thumb is that the disc should be running roughly in the middle of the slot in the calliper which should be fitted straight and the pads should be adjusted in until they just don't scrape on the disc so the wheel runs freely (you can back the moving pad off very slightly more if you prefer the action but be careful not to go too far). If the brakes need adjusting after use, use the pad adjusters unless you have good reason to believe the cable has got out of adjustment - cable tension should never prevent the arm of the calliper from returning fully to its end stop.

Rick.

[531colin]

That all makes sense to me.
It took me several goes to realise we needed to set the brakes up parallel (etc) to the discs, before we could do anything really useful....then another go because we set then up too tight, and once they got hot they wouldn't let go of the disc......bit of a learning curve!

[SoloRider]

Yeah I think trial and error has confirmed all the things you mention, however I do seem to have rotor wobble which is a bugger to prevent. I get the adjustment just right, then go for a ride to test it and a few pulls on the lever later the rubbing is back! Back brake seems very spongy - cable housing compression?

In short, the 'fit and forget' hype seems vastly overplayed - I seem to spend all my spare time trying to adjust these things. Never had this problem with rim brakes.

Hydraulics are probably a better solution, but I prefer simplicity of tried and tested methods. I think I'll be moving back to a frame that takes V brakes soon!

[reohn2]

If you have linear pull calipers with road pull levers you'll need the pads within a whisker of the rotor to have any kind of effective braking without running out of cable,which will cause rub unless the rotor has zero runout.
If your bike has been fitted with the incompatible caliper to levers ratio it should go back to the shop to be rectified.I'd take a copy of the PDF and inform them of the manufacturing fault.

Rotor wobble/runout can be sorted by using an adjustable spanner on the spokes of the rotor NOT on the braking surface.
FWIW,three bikes on 160mm rotors and one on 203's non have enough runout to cause rubbing with BB7 road calipers and road levers on drops.
I've not felt the need to use compressionless outers on any of my bikes as they stop very well with ordinary coiled outers,the bike fitted with the 203's is a tandem and has the best braking I've every experience on any tandem we've ridden.

[mattsccm]

I suspect that you dial this out.
However I dialled mine into the bin as did many others. Horribly fussy and a pig to set the inner pad. Also mine had a tendency to do what felt like they were going over cam. Squeeze too hard and everything went loose. Back off and they came back to their normal ok ish braking.
Maybe I didn't try hard enough but I put up with them for 2 years of fiddling before ditching them.
Of course its possible that the design has changed since early 11 when I got mine.

[Brucey]

So I download a couple of pdfs from Tektro and sure enough it states clearly:

Warning - Tektro mechanical discs brakes are designed for use with linear pull(v-type) brake levers. Brake levers pulling less than 24mm of cable should not be used...

So, presumably the fitted Sora STi levers do not pull 24mm of cable. If this is the case, are Boardman bikes being negligent by fitting these brakes?

yes, I think so.

cheers

[BE1]

This may or may not be your issue (caliper rotor compatibility) but just in case

http://www.croydoncyclist.co.uk/?s=genesis

[SoloRider]

Thanks BE1, I wish there was a more detailed explanation of what was done though with correct terminology. I'll see if I can work out what he means.