Disk brakes & rims

[RJS]

I've bought some of reohn2 35mm favourite tyres, I'm having some new wheels built, and the rear I'm converting to disk, (7 year old Van Nicholas Amazon) but the front will still be canti's, so what rims would people recommend, hubs I think XT, 32 spoke as I've run 32 for the last 20,000 miles with no problem. For the calliper I was thinking of BB7, but the wheel builder has been using and recommends Shimano, advantages and disadvantages? Lastly what rotor would you recommend?
Cheers, Rob.

[grani]

I have been using TRP Spyres on my commuter for 6 months now and I have been very happy with them. The main difference from the BB7s is that both brake pads move when applying the brakes. I find that they provide plenty of power and the modulation is very good. The only thing I would say is that using good compressionless cables is important.

The 160mm rotors that came with them have been plenty good for my use. When the front one wears out I might change it to one without a pronounced wavy design. The wavy design gives a slight pulsing sensation when braking on the front. I have not felt the same when using the rear brake.

I had a rear wheel built with a 36 hole Halo Spin Doctor hub and Velocity Blunt SL rims. I am only 2 months into using them every day 9 miles each way commute and so far they have done well on very bad roads and some off track. The rims are disc only and a bit wide and I would recommend a minimum of 32mm tyres on them.

[Brucey]

.... When the front one wears out I might change it to one without a pronounced wavy design. The wavy design gives a slight pulsing sensation when braking on the front. I have not felt the same when using the rear brake.....

it is probably a thickness variation in the disc; standard issue in cheap ones. This is commonly felt in the front but not the rear because the fork is springy and can move.

As for rim choice, it depends on the weight and road surface etc.

cheers

[Smut Pedaller]

I've built my disc crosser up with H Plus Son Archetypes and TRP Spyres as well. However I've used a Shimano IceTech rotor up front and swapped out the stock pads for EBC Gold metallic pads.

The Archetypes build up really straight quite easily and the quality of them is fantastic, very true straight off the bat with not too much trueing required during the build. They've held up well for the past 6 months. Also the anodised finish is pretty tough, the lettering seems to be coated on or something, they aren't stickers like with some cheaper rims.

The Spyres are also quite good as they are dual piston, give good modulation and decent power. One of the big advantages over the BB7 series is that they are really low profile which reduces the chance of heel strike and they have no plastic parts which means you won't get a meltdown if you manage to get them super hot. The stock pads are ok, but wear very quickly in muddy conditions. The pad adjusters on them rely on loctite which isn't ideal as they lose their adjustment after a while, so I don't use them.

[grani]

.... When the front one wears out I might change it to one without a pronounced wavy design. The wavy design gives a slight pulsing sensation when braking on the front. I have not felt the same when using the rear brake.....

it is probably a thickness variation in the disc; standard issue in cheap ones. This is commonly felt in the front but not the rear because the fork is springy and can move.

That made me think and I have measured the disc. The thickness varies by approximately 1/100 mm. That is not going to cause the pulsing sensation when braking. It is negligible and you get used to it quickly but I would prefer if it wasn't there at all.

[mattsccm]

I agree with the pulsing using wavy discs. Don't forget that with most cable calipers the inner pad is fixed and it all relies on disc distortion. quality doesn't matter. Expensive wavy's pulse , cheap flat ones don't . Planet x have some Pacenti CL25's on sale at the moment. I am tempted 2 have a pair for spares as I have one set on my disc braked bike already. Very pleased that I didn't pay full price for the first set. Used them with both 25mm and 30mm tyres and would happily go much bigger.

[reohn2]

If you're willing to service them every year or two these are bombproof:- http://www.ebay.co.uk/itm/Shiamno-Deore ... 2ed2ab1b69

I've got Avid CS G2's 160mm rotors on three solos and 203mm on the disc tandem,all with BB7 road calipers,They're the bees knees,they stop PDQ,the pads are cheap,they're easy to set up and adjust and I've put a lot of,sometimes very mucky,miles on these brakes with no problems whatsoever
What more do you want from a brake? :- http://www.chainreactioncycles.com/avid ... -prod67750
Someone mentions plastic parts that can melt,we've not melted anything yet on the tandem which takes far more heat than any solo when braking.We also have friends with the same tandem as ours and they haven't had any meltdown issues on their BB7's either.
It's scaremongering IMO.
Someone up thread mentions heel strike of BB7 calipers,I take 46(11) shoes and use a pair of 47's in winter,without issues,TBH you'd need to be wearing clown shoes to get anywhere near to heel strike
Rims:-
I use DRC ST19 rims on three pair of wheels but DRC have stopped production of rims recently
That said,we Have 40 hole Mavic 719's on the tandem without issues .
I don't think you'd go far wrong with these rims though:- http://www.spacycles.co.uk/products.php ... 0s116p1568

[Brucey]

. The thickness varies by approximately 1/100 mm. That is not going to cause the pulsing sensation when braking...

don't bet on it. Where disc thickness variation (DTV) specs are published, they are really tiny numbers, often too small to measure accurately without specialist metrology equipment.

In point of fact pulsing from the waviness is easily distinguished from that of thickness variations because the frequency is completely different. The disc waves can make a humming noise at speed but DTV is nearly always a judder when braking from normal speeds.

BTW I have Hope wavy discs and they are fine; they hum in the wet but are otherwise just fine noise/pulsing wise.

Cheap discs can and do judder, often, wavy or not.

Top tip; If you have a suspect bad disc, stick it on the back and use abrasive pads on it for a while; it should improve after some use, often enough to allow it to be returned to front duty.

cheers

[sreten]

Hi,

I'd be converting the front to disk before the rear, your best brake goes on the front.
Campy do a brake set with dual pivot front, single pivot rear, for the same reasons.

Maximum braking on the front is twice that of the rear, half the stopping distance.
Full use of the front renders ther rear barely effectual before it locks up.

rgds, sreten.

[andrewjoseph]

I've put bb7's v on our touring/road bikes and the static pad adjuster shows it has started to soften. I believe it a 20 % + descent on Llynn peninsula between aberdaron and abersoch. The front disks turned straw colour.

My wife was very nervous coming down so probably braked too much.

[grani]

In point of fact pulsing from the waviness is easily distinguished from that of thickness variations because the frequency is completely different. The disc waves can make a humming noise at speed but DTV is nearly always a judder when braking from normal speeds.

Well the discs hum when braking at speed and go into a rhythmic pulsing that corresponds to the wavy shape of the disc when slowing down below about 6 mph. Most of it is noise but there is some slight pulsing sensation in the fork when braking to a virtual standstill.

My theory is that it is a correlation between the stiffness of the fork and variation and possible increase/decrease of braking surface on the disc caused by the wavy pattern.

I would assume that a well designed disc will probably minimize the sensation. I do not consider it a big problem but it feels a bit strange when you are not used to it.

Anyway that is my take on it but I do take your point that variations in thickness can cause a juddering brake. I think that is fairly logical.

[freeflow]

Anyone got any thoughts on the trp hy/rd. These are currently top of my list for a road bike upgrade.

[Brucey]

if it only presents as a judder at very low speeds then it probably is the disc waves that are causing it. I guess some discs are more wavy than others!

cheers

[RJS]

Hi sreten,
yes thanks, I know what you say is true, the reasons I'm only putting a disk on the rear is because the frame was made to take a disk brake calliper, and although I've had a set of steel forks made ready to fit they were only made with canti mounts, as well as heeding the discussion on carbon forks with aluminium steerers I did not want the fork to be stiffer and possibly affect comfort. Thinking towards winter months and wet gritty lanes I thought I might be able to use it as a bit of a drag, although I would generally rather brake release and brake. I'm not too concerned if I have to use two different rims to suit the two brakes, but I wondered if there was a rim that would suit both.
Cheers, Rob.

[Brucey]

I think you can use most rim brake rims in wheels for disc brakes with no worries.

Obviously the ideal rims will vary with the intended use, weight, tyre size etc.

BTW choosing 36 spokes only incurs a 30g weight penalty over 32 spokes but the wheel is a lot stronger, so I'd choose 36 in the rear. A 36 spoke wheel can be both stronger and lighter if it is built using DB spokes in place of PG ones.

Also, you probably know this already but if you fit a front caliper to the rear mounting, you can often run this with no issues (the lateral offset is also different so it doesn't always work...) but with a 140mm disc instead of a 160mm one. If you have power to spare this saves a little weight and makes for a disc that is less easily knocked out of true.

cheers