johngwheeler

I've just bought a new cyclocross bike (Giant TCX), and my first short test ride felt very smooth.

I took it out for a more serious ride this weekend, on admittedly unsuitable terrain which would have been better with an MTB. I had to use the brakes quite a lot, and went over quite a lot of rocky ground - but pretty slowly. I kept it short because I was getting battered by the ride - probably less than 45 minutes.

However, after this ride I started hearing a "rubbing-squeak" in either the frame or the rear wheel. It was hard to tell exactly where it was coming from. Backing spinning the wheel didn't seem to make a noise, but gently move the bike forward with a bit of weight on it did cause something between a squeak and a rubbing noise.

I initially thought the disc brakes were off. Loosening the rear axle and retightening did seem to reduce it a bit, and I can't clearly see the gap on both sides of the rotor. The distance between the rotor and the disc pads seems to be tiny - about a millimetre.

The gap between the rotor and the pads is more obvious on the front wheel, and I think this is OK. I'm concerned that the rear wheel may be offset and gently touching the pad on one side. However, the rotor doesn't seem to get hot after moving for several minutes, so if it is touching, it must be only just.

I tested again today on pavement, and got the sensation that the bike was a bit slower than the first day I tried it. It seems to make a bit of noise on the road, and I'm not sure how much is due to the road tread (which is quite knobbly ), or whether there is some other friction in the system.

Also, the front brake lever now has to be pulled considerably more than the rear one to get the same braking effect, and the brakes make a much less pleasant sound compared to when the bike was new. Is it normal for disk brakes to become a bit rougher sounding with use? (I'm talking cycling 35-40km in total). Is this normal cable-stretch that can be easily adjusted?

I'm a bit concerned that my first serious test ride offroad was too abusive for the bike - it was really MTB territory, but I've never tried this particular trail, and had no idea - it was only about 3-4km and I walked the worst bits. Could using the brakes too heavily when new damage the rotors?

So, are these normal running in symptoms that can be adjusted, or is something more serious going on? I understand that it is normal to need adjustment of a new bike after a few weeks, but I've only had it 2 days!

Maybe I'm being a worry-wart, but it would be good to know.

Thanks!


John

rhenning

It is new and has warranty you paid for so use it. Easy to help if I had the bike here but over the net not possible. I can think of several things that could be causing squeaks but would have to touch the bike to know for sure. Hopefully it is not buyers remorse. Roger

jimc101

define unsuitable terrain
For the squeaking, go ride it for a couple of weeks, and take notes so you can query anything that doesn't work itself out at the first service.

johngwheeler

That's an impressive video, and although that course looks pretty steep and bumpy, the surface I was on was a lot worse. Something like:

Mt.-Balagbags-Rock-Garden.jpg IMG_0514.jpg

This really wasn't very enjoyable, and whilst an experience rider might be able navigate it without damaging their cyclocross bike, it was certainly beyond my level!

But thanks for the advice. I'll ride it a bit on the road, and take it in for its initial service to the LBS where I bought it.

John

johngwheeler

No, not buyer's remorse :-) Just a bit of remorse at myself that maybe I've put something out of whack by biting off more than I could chew on the first ride!

John.

Andrew R Stewart 

Were the brakes bedded in properly before your off road ride? Are the rotors running very straight still?


Disk brakes have so little pad/rotor clearance that a slight rotor wobble of miss centered caliper can and does cause rubbing. But usually not very much actual stopping force happens without also being obvious when looked at.


BTW didn't your shop explain that every bike gets slower the longer you have it ? Andy

johngwheeler

The brake bedding had occurred to me. When I bought another bike with mechanical disc brakes, the shop suggested I don't do sustained braking for the first few 100km, and to "pulse" the brakes on descents rather than riding them, which could apparently caused the pads to "glaze" and become less efficient.

I didn't baby my new bike, and perhaps I should have! I had to apply hard brake pressure on the rocky trail, and although it wasn't very long (3-4km / 45 minutes), I was hanging on to the brakes a lot of the way.

I think the rotors are still straight. I will get the bike shop to look at the pads to see whether I've caused undue wear or thermal glazing in my early test ride.

I hadn't really thought about "running-in" - and maybe I should have!

The LBS didn't tell me about the slow-down effect...perhaps they were waiting for me to discover it myself and then order the $8000 road bikes they sell....

Thanks,

John.

gsa103

Your front brakes need bleeding. Most likely the ride dislodged an air bubble that was in the lever, and pushed it into the line.

Give the rotors a quick wipe with alcohol, and they should quiet down. Probably just some oil or something on the rotor.

As for no hard braking for 100km Whatever shop told you that, never take your disc brake bike there. Brakes are basically ready to go, but benefit from bedding. Normal riding will eventually bed them though.

Bedding in discs is trivial. Drag the brakes while pedalling at a medium effort for 30sec. Then quickly accelerate to 15+ mph and brake hard to almost stopped. Repeat the accelerate and brake 3 times total. After that just ride normal for a few minutes to let them cool.