Why do you rub them down? Does it improve friction? The brakes on my winter/work donkey are terrible and i've been wondering about needing new rims.Originally Posted by Graham Breeze
Even with newly-sandpapered Campagnolo brake blocks.
Why do you rub them down? Does it improve friction? The brakes on my winter/work donkey are terrible and i've been wondering about needing new rims.Even with newly-sandpapered Campagnolo brake blocks.
My rear brake was squealing embarrassingly long and loud. It is due to vibration so sanding the shiny layer of grit/gunge off the block face, cleaning the rims and making sure the block and rim are in good flat contact remedies the shrieking problem. Helps the brakes work better and the rims last longer.
I think Specialised are to stop supplying bikes with rim brakes. I deliberately chose rim brakes on the road bike but my Boardman ADV has disc brakes and for off-road riding that makes sense, much as I dislike them.
I've never heard of sandpapering brake blocks before. Cleaning your rims, yes - I do this after virtually every ride.
With rim brakes some particles of grit/sand/salt (in winter) can get onto the rims and is then forced into the metal of the rim when braking. If you clean the rims regularly then you prevent a build up of contamination, and hopefully prevent a particle from being forced some depth into the rim.
If you don't clean your rims then you can end up with grooves on your rims which reduces your braking area. It also makes the rim wall thinner and will eventually lead to the rims failing when riding the bike. If you have access to a Vernier gauge you can measure the thickness of your rim walls.
In most cases cleaning the rims and fitting new blocks should solve poor brake performance. If the rims have deep grooves I'd change them. Rims are relatively cheap, and it only takes me about an hour a wheel to take off an old rim and build in a new one. Importantly, if you do this you will need to measure the ERD (effective rim diameter) of your existing rims and buy ones the same - otherwise you'll need new spokes and for the cost and effort you may as well have bought a new pair of wheels.
Not just me. I 've just found two videos on youtube recommending it amongst other approaches like cleaning the rims.
When I had rim brakes, I always made sure the rim was clean after a ride and an occasional resurfacing of the block with a bit of Emery paper when changing a wheel is also good idea.
Blocks get bits of hard grit etc embedded in them and freshening them up does them good, leaves a less polished surface and prevents damage to the rim.
However, I'm sure I have posted on here about my wholesale conversion to disk brakes and wouldn't be without them on road or MTB. Rims are fine in the dry but in the wet on a steep descent....!?
I must admit that in all my years of cycling, this issue of grit on brake blocks causing wear on rims has never really entered my consciousness.
A few years ago, when I collected my bike from the local bike shop after a repair, they pointed out that the rim on one wheel was getting dangerously thin. But the rim had done many years of service, so I put it down to normal wear and tear (and I did get it replaced).
As for steep descents in the wet: I have just got used to starting to apply the brakes well before I actually need to slow down!
Oh yes disc brakes stop you better but they look so... clunky.
I don't carry any of those shopping bags under my saddle or elsewhere either
It's a matter of sleekness and style...aesthetics.
I'm sure that my next bike (which could be many years away) will have disc brakes, as it's pretty difficult to get a road bike without them nowadays. In the mean time, I'm very happy with rim brakes.
I'm not sure about how suitable disc brakes are for me, because my total rider plus bike is so light (under 70kg). I haven't used my rear brake since 1994 (and I can remember where), because it will pretty much instantly lock the wheel (I'm still using a single pivot side-pull on the rear, should I need to use it).
The advantage for me with rim brakes is that I can't lock the front wheel, even though I can lift the rear wheel easily with hard braking in dry conditions. Wet weather braking is not as good, but then again I wouldn't want to have massively effective braking in slippery conditions, because with low total weight it doesn't tend to end well. As all contributors have said, keeping your rims and blocks free of contaminants will improve the performance of rim brakes, and this is especially so in the wet.
Of course Brett on his Cinelli F/W just uses brute strength on the pedals to stop on a sixpence -I've heard his front brake is just a dummy.
In the parallel universe of cycling, there is a branch of the sport called fixed gear crit racing. Those of you 'in the know' will know a 'crit' is a criterium - a French word for 'laps around the town' style of races (like Kermesse racing in Belgium and the Netherlands).Of course Brett on his Cinelli F/W just uses brute strength on the pedals to stop on a sixpence -I've heard his front brake is just a dummy.
Fixed gear = fixed wheel in old money, so fixed gear crit races are 'laps around the town' races on fixed wheel bikes. To spice things up a bit more, brakes are banned meaning that all braking is done by applying a back pressure on the moving pedals (which is a lot harder than it sounds). In Italy they have night races under street lighting too, just in case it wasn't dramatic enough already.
When I discovered this, a year or two ago, I realised that this had just the right balance of danger/skill/stupidity to make it suitable for me - but they don't do it in this country, as British Cycling don't want to touch it with a barge-pole.
In the name of research, I did try some fixed gear crit training on the local single track farm track with four 90 degree bends in quick succession. I can therefore report that bringing a bike down from 20mph to 12mph for the bends is relatively easy, but actually stopping the bike completely is very difficult as you require a huge amount of torque at a very low cadence.
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