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Disc brakes - avid BB7

19 posts & 8 voices | Started 3 years ago by coylumbridge | Latest reply from coylumbridge

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avid bb7 disc brakes

coylumbridge - Member

I've just fitted Avid BB7 disc brakes (F-185, R-160) with SD7 levers to my mountain bike after taking off the Avid v brakes.
Three questions please:

1 Even after backing off the pads about 4 clicks, there's still a little rubbing of the disc against the pads as the wheels turn - not a lot but I wondered if this was normal (may be wheel/discs etc aren't completely true ?)

2 Any hints on how best to bed the pads in ?

3 Any ideas about how I can make the v-brakes lugs look better ? (I've removed the whole assembly on the rear but have left the bolts in the front as I didn't want a hole into the fork)

Thanks

Posted 3 years ago #
druidh - Member

You can get little "plugs" to replace the holes in the forks. Hope do some in pretty anodized colours, or you can get some cheaper ones from Brand X or DMR

http://www.chainreactioncycles.com/Models.aspx?ModelID=17

Posted 3 years ago #
HTTP404 - Member

http://www.youtube.com/watch?v=x1kezXQVnLY

I back them off on both adjusters and then hone them in clickwise alternatively on each side.

Posted 3 years ago #
coylumbridge - Member

druidh - thanks - I hadn't realised CRC did such a thing - will look out for them coming back into stock

HTTP404 - thanks (I'd used the SRAM youtube video when I was fitting them) - but, could you tell me please - do you mean that you back both pads off completely then dial them in alternately until just before they rub ?

Posted 3 years ago #
HTTP404 - Member

yes. that's pretty much what i do. i also use sd7 levers with the "modulation" adjuster which helps a bit too.

Posted 3 years ago #
coylumbridge - Member

HTTP404 - thanks - I'll have a go at your suggestion as well - I've fitted SD7's but haven't been out to try the adjuster yet

Posted 3 years ago #
AdamM - Member

Strangely enough, the instructions that come with BB7 brakes work pretty well for setting them up! The first trick is to get the caliper in the right place and parallel with the disc, then it's easy to get the pads to clear. If the caliper isn't parallel to the disc you'll find it really difficult to stop it rubbing.

Posted 3 years ago #
coylumbridge - Member

OK - I followed the instructions to the letter and have tried upmteen times but I still can't get the rotors to stop rubbing at certain points as they turn. I've dismantled, fully cleaned and redone everything to no avail. It is light rubbing but I need to back them off at least 4-5 clicks to get to this point; using 2-3 per instructions is no use.

I did notice that I can push the caliper slightly even after doing all the tightening to spec'd torques to alleviate the rubbing.

The instructions state that the rotor bolts should be torqued to 9-10Nm (80 - 90 in-lb) so I used 85 in-lb. However, the rotors have 6.2Nm (55 in-lb) etched on them. Do you think the higher torque could be warping the rotor slightly and should I use 55 in-lb instead or am I clutching at straws ?

Last question - is it OK to have slight rubbing at certain points anyway ? I've done the 1/3 & 2/3 but am a bit worried that having backed off the inboard 4-5 clicks, on pulling the brake levers the outboard pushes the rotor very close to the caliper body.

Any help/advice would be gratefully received.

Thanks

Posted 2 years ago #
teacake - Member

coylumbridge, If your rotors are brand new then it is likely that they are slightly "taco" shaped due to the deep drawing process in which they are made [I think?!]. You can use a shifting spanner or pliers to bend the rotors at the points they rub and that should help.

As far as bedding in goes - just ride them. The key thing is to have a lot of heat, so drag the brakes down a hill whilst pedalling.

I'm on night shift so any questions just fire away!

Posted 2 years ago #
coylumbridge - Member

Thanks teacake - hope the nightshift's going well. Maybe I'm getting worried about nothing. I suspect if I try to bend them I'll do more harm than good - knowing me, I'll overdo it (have already managed to sheer one of the rotor bolts even though I was using the correct torque but think there was a problem with the bolt - had to use a reverse thread remover to get it out and had bought a replacement set just in case).

Posted 2 years ago #
teacake - Member

You did well getting that out! If the rotor bolts are tight then bending the rotor itself shouldn't be a problem. I've managed to exert a lot of force on mine before, with no issues. If the slight rubbing is bothering you enough then give it several bends at the point it rubs.

I all honesty, once you've done a days ride, they'll be a different shape anyway. Keep fiddling with the pad position though as with experimentation you'll learn a lot about how to set them up - and how not to!

The key thing [I believe] with cable discs is to make sure that the rotor is centred in the caliper. A common problem is that the rotor may be very close to the caliper on one side and as the pad wears, the rotor is pushed against the caliper and you'll get a nasty metal on metal warning noise.

Best of luck!
ps, the best BB7 set up guide I've found is on the park website.

Posted 2 years ago #
coylumbridge - Member

Thanks for this teacake. I didn't know about the park website - have just had a look and will have a go with their avid adjustment instructions which are a bit different to those which came wth the BB7s.

Having had a look at others, it looks to me as though the rotor torque setting in the instructions with the BB7s at 9-10Nm (80 - 90 in-lb) is actually too high and should be 6.2Nm (55 in-lb) as etched on the rotors. I'll have a go at resetting the torque on these as well just in case this is making a difference though I suspect not.

Thanks again.

Posted 2 years ago #
trail_rat - Member

torque on the rotor bolts is not the issue...

Like the others i still suspect you do not have the rotor parallel to the pads

back off both sides to the maximum , then get a torch and shine from behind the caliper and look at the rotor relitive to the slot in the caliper , get it lined up in the center and with an even gap all round . at both ends !

Then dial the pads in to just before they touch , using the torch method to check

Failing that . Go see gordo at the bikeshop in colyumbridge if thats where you live

Posted 2 years ago #
coylumbridge - Member

Thanks trail_rat and teacake. I've got a few things to try here so think I should be OK now.

Don't live in coylumbridge - just go up there for holidays and cycling as we love the area. Find Bothy bikes very helpful.

Cheers

Posted 2 years ago #
grumm - Member

If they are only rubbing a bit just ride and they will probably sort themselves out.

Posted 2 years ago #
mikey-simmo - Member

Will Avid BB brakes work with V Brake levers like my missus has on her bike?

Posted 2 years ago #
grumm - Member

I fitted BB7s to the front on my gfs bike with her old v brake levers, they work fine. Might work better with other levers, I dunno.

Posted 2 years ago #
trail_rat - Member

they do work with v brake levers but feel best with an avid lever.

Shimano brake/shifter unit levers feel **** with them

Posted 2 years ago #
coylumbridge - Member

My bike had avid fr-5's which would have been fine. However, got some advice that sd-7's would be even better as they have speed dial (but I've yet to figure out how to use these properly).

Posted 2 years ago #

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