Brake Caliper/Spokes Clashing

steelo

I have a Specialized Rockhopper and riding it last night I noticed that the spokes of the front wheel (Bontrager rim and s/s spokes) was running so close to the inside edge of the caliper that you could hear some spokes striking the caliper. This hasn't happened before and I've never noticed the wheel running so close to the caliper. I checked the wheel and the spokes are all intact, all have a decently high pitch tune, the wheel isn't buckled either.

Has anyone else experienced this before? Are brake calipers designed to run almost against the spokes!?!?

The front brake works perfectly well with the 160mm rotor by the way.

The Rookie

For it to go from not touching to touching, something has changed, only variables are calliper on mounting (adjustable) or axle within hub...if you have cup and cone bearings it's worth checking for play between the axle and hub.

steelo

The wheel has sealed bearing, the caliper hasn't been adjusted for about 3 years as the bike hasn't really been used. I have swapped wheels over so I can only assume that the Bonty wheels have 'wider' spokes but this just seems a bit extreme.

I was hoping someone would say "spokes are usually only 1-2mm away from the calipers".

The Rookie

Cup and cone can be sealed....do you mean Cartridge (which can be sealed or unsealed cartridges and have an extra seal or not anyway).

Spokes are usually close, I'd try moving the calliper out on the mounting by a mm or so, assuming it's not a bearing issue.

steelo

If I move the caliper out then the brake disc won't be aligned. The wheel hub uses sealed bearings, not cup and cone!

The Rookie

FFS Cup and cone can be sealed, as they are on Shimano hubs I presume your trying to say is that you have cartridge bearings (which are usually sealed in themselves but not always and may have an external seal).

Saying the bearing is sealed tells you nothing about the bearing behind the seal!

You can move the calliper out an mm or 2 usually without issue.

steelo

When you say FFS I guess what you're trying to convey is that you are annoyed at my mistaken use of the term 'sealed', for that I apologise.

Yes they are cartridge bearings.

The Rookie

Yes I was annoyed as I'd already clarified it once for you!

I would see if you can move the calliper just enough to clear the spokes, as long as it's 'parallel' you can get away with it being 1mm off centre on the disc.

Any play starting in the bearings can also cause this but cartridge usually fail quite quickly once play starts.

steelo

How do you mean "cup and cone can be sealed, as they are on shimano hubs"? My shimano hubs are cup and cone and they're not sealed. Unless sealed doesn't imply that the grease is sealed in, the grease can easily be blasted away using a hose. Maybe the term sealed is used to describe a different part of the bearing construction. Can someone clarify for me what is meant by the term 'sealed' when it comes to wheel bearings? I'm obviously making a rookie mistake here somewhere!

The Rookie

You can blast the grease out of sealed cartridge bearings in the same way, sealed means has a seal rather than the most basic wheels that have no seal at all.
http://techdocs.shimano.com/media/techd ... 651540.pdf
Note the name of item No7.

cycleclinic

Sounds like the problem has always been there but you have just noticed. I cannot move my caliper by a mm without causing rubbing so don't do that. Get your LBS to check the dish of the wheel it may have always been out a bit.

nicklouse

I would say the wheel has lost tension causing the rim to move towards the caliper side.

Get the wheel dished correctly.

steelo

I'll put the wheel back on the original frame and check the clearance to that brake calliper, if the spokes then contact the calliper on that frame as well I'll know the wheel spokes have lost tension. I rode the bike again last night and it sounds like I've got spokey-dokeys!

The Rookie

It will be obvious, the rim won't be in the middle of the gap between the forks!

steelo

IIRC the wheel is running dead centre, but I'll double check that. It's really got me foxed. I used to ride the bike fairly regularly and never noticed any issues with the wheel, now all of a sudden the spokes are brushing past the calliper.

steelo

As I expected, the wheel is running central on the fork. I took the wheel off and inspected the calliper closely to find the rotor has been running against the calliper body to the extent that there is bare metal showing from where the rotor has worn the painted surface away. It looks like the calliper has taken a knock and the pistons have centralised on the rotor, but way over on the extreme of the outer side. Hence the calliper being so close to the spokes. I've re-aligned the calliper and slotted the wheel back in and all is quiet again!

The Rookie

steelo wrote:

the caliper hasn't been adjusted for about 3 years a

There was your problem, it had and you didn't realise!

steelo

I think it must've been pushed when it was loaded into a car, under the weight of another bike (bad I know), or possibly having things leant against it for a prolonged period of time when in the shed. I definitely didn't knowingly or purposely adjust it to be in that position! No tools have been near the calliper for a good 3 years!