Pumping brakes

[illmonkey]

I took my bike in for its first services (free 3 month one) and mentioned the brakes are a bit spongy, left them to it.

Come back after 30 mins and its all done. The guy was pumping the brakes like crazy saying to get them stiffer you need to get air, yes AIR, into the brake system. That'd be my hydraulic brakes, right?

Is there any truth to pumping them to build up pressure, I'm not sure I belive it. If not, how do I go about making them actually work?

[colin1976]

Sounds like you need to get them bled to remove the air bubbles. Air in the system is compressable (unlike the hydraulic fluid) - probably what's causing the spongy feel.

[cliff123]

Are they Avid brakes by any chance?

Just had the same thing with my new stumpjumper. Took it back to the shop, and unfortunately the two main mechanics were out for the day. So the fella on the till had a look. Said this was a common thing with Avid brakes. I queried it. He then proceeded to pump the brake very quickly for 30 seconds / minute. Yes it did stiffen the brake up, but after 5 minutes of not using the brake it started to go soft again. (and even with the pumping it was not how I would expect a quality expensive brake to work in my opinion). So, still in doubt that this was truly right, I took the bike to another mechanic at another shop. He bleed the system, and loads of air came out. The brake is now how I expected it. (If you do bleed the brakes yourself, do be careful not to get any fluid on the disks or brake pads).

I've personally been a bit disappointed with the local mechanics. My new bike has xtr and slx gearing on it, but following 2 tune ups by the shop the front derailleur still rubs the chain in top and lowest gears. And when it doesn't it then has trouble changing rings on the front. I've now read up on how to tune and setup the derailleur, and it's now the best so far, but it's still not perfect (still getting chain rub against the derailleur when using the top two gears). Can anyone offer advice on how to get this done perfectly?

Thanks.

[illmonkey]

cliff123 said:

Are they Avid brakes by any chance?

Yep, Avid juicy 5's.

They seem even worse than when I took them in. The brake mount was also only done up finger tight, causing them whole lot to move! Not impressed with the shop at all, and only too it back there because the 'service' was free.

I'll look into bleeding them myself, but would rather get someone to do it, unfortunately that means trying to get it into a car (which is off the road) to take it to a different shop.

[baxb]

Avid's are known for being a bit spongey from new, I bled mine within the first couple of weeks & got load of air out. I would buy an Avid bleed kit & do it yourself, it's pretty easy to use & if you're riding regularly you'll want to bleed them once a year.

If your shop is saying it needs air in the system, personally, I wouldn't trust them to put air in my tyres.

[illmonkey]

baxb said:

Avid's are known for being a bit spongey from new, I bled mine within the first couple of weeks & got load of air out. I would buy an Avid bleed kit & do it yourself, it's pretty easy to use & if you're riding regularly you'll want to bleed them once a year.

If your shop is saying it needs air in the system, personally, I wouldn't trust them to put air in my tyres.

Indeed, I had to stop myself having it out with them. I just walked away.

Thanks for the help everyone, I'll order a kit this week.

[snotrag]

Firstly - you need to find a new bike shop...


Secondly - from experience of two years spent building and fixing bikes which usually used Avid brakes - the factory bleed is generally crap.

We had to rebleed a majority of the brakes at the initial / 6 week service point.

I would presume that they are machine assembled.

Once you get them done properly by a mechanic with the correct kit they feel great.

The kitself is available to buy if you want to do it yourself - worth it if you have mates with them, or use the bike a lot and do your own maintenance.

[markoc]

I've got Juicy Threes on my cannondale and coming from Magura rim brakes they do feel very spongy. They'll be serviced with the bike around Christmas and I've no doubt there is air in the system. In the meantime, the tiny grub screw allen bolt under the blade will improve the feel at the lever, by memory by dialling it inwards. Make sure you get the right one, as I think the other holds the lever blade in. Also if you do it up too much you'll stop the disc spinning freely. Recognise you have J5's but principle should be the same. Firmed mine up nicely.

[mk1fan]

cliff123 said:

I've now read up on how to tune and setup the derailleur, and it's now the best so far, but it's still not perfect (still getting chain rub against the derailleur when using the top two gears). Can anyone offer advice on how to get this done perfectly?

Thanks.

You shouldn't (on modern 9-spd setups) use the cross over gears (largest chainring and largest sprocket / smallest chainring and smallest sprocket) as it puts too much lateral strain on the chain. Setting up the front deraileur needs to be parallel to the outer chain ring and 1-2mm above the teeth. From there adjusting the outer stops and chain tension is all you need to do. It'll never be perfect though.

[cliff123]

mk1fan said:

cliff123 said:

I've now read up on how to tune and setup the derailleur, and it's now the best so far, but it's still not perfect (still getting chain rub against the derailleur when using the top two gears). Can anyone offer advice on how to get this done perfectly?

Thanks.

You shouldn't (on modern 9-spd setups) use the cross over gears (largest chainring and largest sprocket / smallest chainring and smallest sprocket) as it puts too much lateral strain on the chain. Setting up the front deraileur needs to be parallel to the outer chain ring and 1-2mm above the teeth. From there adjusting the outer stops and chain tension is all you need to do. It'll never be perfect though.

Thanks. I appreciate I shouldn't use the opposite gears (front and rear) as a norm, but of course occasionally you do and I'm getting the rub. The front deraileur is currently sitting 8mm above the outer teeth. (that is the outer edge of the deraileur is sitting 8mm above the teeth) so I guess I should try and lower it a bit. Again, something which I would have thought the shop would have got right.

Thanks very much.

[timbo48]

This may help. Latest MBR has workshop advice on how to bleed Avid Elixir, but I imagine it would apply to other brakes in the Avid range.

[illmonkey]

timbo48 said:

This may help. Latest MBR has workshop advice on how to bleed Avid Elixir, but I imagine it would apply to other brakes in the Avid range.

Thanks. I'll go read it in my local shop and practise at home

[RobDickinson]

I had air in my front brake, used to pump it up a bit to get it working, but half the time it'd gone to mush when you needed it.. sorted with a bleed now...

[mk1fan]

Sram have put a video tutorial on You Tube on how to bleed Juicy brakes. Search for Sramtech.

I'd recommend that you double the time spent de-gassing the fluid and bleeding each component. Will become clear once you've seen the video.