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Avid Bb7.. *new Issue*... Bent Rotor/tri-align Woes


Sponge

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Hey there,

EDIT: thanks guys, i realised all it took was a bit of OOMPH to properly shove the pads into position. Before they just sat in there with the spring, not really properly seated on their 'seats'.

Check my third post in this topic, I've got a new issue, maybe you could help?

Cheers!

Edited by Sponge
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yep yep, all that was completely done correctly as per th BB7 online instructions.

It's done now; I realised that the pads had to be PUSHED damn damn *hard* into the caliper. We're taking gripping the prongs of the pads with pliers and pushing in HARD.

Jese, so a bit of beef-handed-ness was all it took?

Haha..

But on a new note, whilst we're on BB7s.... I've got a rotor which has slight bends here and there... it's new though, and the reason it's bent is because of the Tri-Align system of an Avid, if say you set up the caliper when the pads are rubbing onto a 'bent out' part of the rotor... this is sheer bad luck and bad news and the caliper will align itself to the bend and in turn... after riding about, it will bend the whole rotor ever so slightly to align to the caliper..

^Anyone had problems like this? What was your fix? I've come to the point where I can't even tell what part of the spinning rotor is the true 'straightness'. Last resort, could take off rotor and try bending it here and there whilst using a flat surface as a 'truing stand'?

Edited by Sponge
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Sorry, but that's just really very ignorant and thick-headed.

Simply, when your rotor is slightly bent left and right, and caliper misaligned...riding down a hill like that? that's the worst idea... i don't want my pads to wear at an angle which will cause further problems later on.

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it works in a pinch. otherwise get an adjustable spanner, size it down to the disc and bend the rotor in the opposite dirrection to how it's bent, you really wanna be delicate with it [same as when you do spokes a teeny bit at a time]

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If I had a brake like Hope, then it'd be alright, since they are in a permanent fixed caliper position.

The problem lies in the fact that I use a BB7 where they have the Tri-Align system with the post mount adaptor. Basically, it means there is no 'fixed' caliper position, so right now my caliper is most probably bolted tight in a position to suit the rotor at a bent/slanted position... this'll just worsen the rest of my rotor if I drag it.

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Surely what you're describing is a fooked rotor? Get a new one, set the brake up once and you're away. If I understand what you mean by Avid's 'tri-align' system correctly, all you do is loosen the bolts, pull the lever in and do the bolts up and hey presto, nicely set up brake. Not that I've ever used a BB7 before but that's how my Hayes post mounts worked.

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When you spin the wheel fast, can you actually notice the bend with the naked eye (try shining a torch light between the pads & disc rotor to see how much the rotor bends)and how marginal are we talking about ie; approx less than 0.5mm? Any bend in the disc rotor as marginal as that is hardly worth trying to correct via pad adjustment. As long as rotor spins freely when the pads are open and rubs slightly when you feather the brake, i wouldn't spend the extra time trying to get ultra fine pad adjustment. unless you wanna get the hub and fork disc mount re-faced and use extra fine flat washes when mounting the caliper. Be interesting to know what solutions adam&tartybikes makes of this problem.

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Point is it's a new rotor... used for a few days. It was slightly bent out of the package from Tarty, and I put it on. For some reason the rotor decided to bend even more slightly, left and rotor in tiny tiny tiny increments. I can't exactly tell what the true straight orientation is. It' only shiftin left and right by 1mm or so though.

The tri-align system is the post mount adaptor system where you tighten the bolts. When the rotor is slightly bent in a place, this is the worst system suited for it... since the caliper will align itself to the bend , if you get me? Now, if the caliper is preset slightly angled, thanks to a slight bend in the rotor, this'll mean the whole of the rotor has to get accustomed to the new angled position. Meaning gradual warping, and no real power...

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Arr i know what you mean now where the rotor is not sitting parallel with the pads. i had that problem with my 1st BB7 yrs ago, and i had to get extra fine washers and played around for ages getting the pads to sit as parallel as i could. Even squeezing the brake levers until the was about 1mm of space between the pads and the rotor and then securing the lever in that position with masking tape. also rubbing the washers down a bit to get that extra fine adjustment. It was a pain (in the neck & back) doing it but it worked until about 2 months later when i seriously bent the rotor from a silly stack,bought a new rotor and went that same painstaking process again.

Edited by Rusevelt
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Did you tighten the rotor screws evenly and a little at a time? If you tighten one up completely and then the next you will more likely distort the rotor, try slackening the screws and retightening them in turn. A warped rotor will make the brake feel slightly more spongey but shouldnt otherwise affect performance, if it was warped from new from tarty I would have returned it for a replacement.

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Personally I never trust the hold the brake and do the bolt up method for BB7s. The rotors are quite flexible really ,and I often find that as I tighten the bolts the torque of doing so can twist the caliper.

I think its easiest to put the bike upside down on something fairly bright, like a light grey paving slab, then loosen caliper off, and you should be able to look down between the rotor and pads and see a glimmer of the bright background the bikes sitting on. Then I normally do the bolts up bit by bit whilst holding the caliper so the torque of doing up the bolts can't twist the caliper.

Sometimes I find it easiest to wind the non moving pad in a bit further than I want, then alight caliper up touching this, then wind it back a notch or two. Its always going to take a bit of playing.

If you want to use the auto aligning style method then why not just set it up on a part of the rotor thats not bent? Spin the wheel and using a marker pen move slowly closer to the rotor, as you just get close enough the pen will mark the rotor on its high spots where its bent out, and you can work out which bits are bent and which way. Then just clean the rotor off afterwards.

At the end of the day its never going to align 100% perfectly. The best thing you can do it get it set-up as good as you can then leave it. And the pads will wear to suit its position, the brake will feel stiff and work very well.

Finally, when you put the rotor on the hub did you cross torque the bolts? screwing them all in loosely then tightening the first bolt up medium tight, then doing the one directly opposite it, then going back to the one beside the first bolt and doing that one and its opposite one, and so on, then going round again and doing them all up properly tight? If you tightened them up following round the circle, and didn't do them up in increment,s just loose to full tight this can often cause parts like disk rotors to warp. Its worth a shot to take the rotor off, make sure there's no crap between it and the hub and then doing the bolts up in a cross torquing pattern before writing your rotor off.

Edit: Damn i took so long to post some one beat me to it about the bolts....

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It's done now; I realised that the pads had to be PUSHED damn damn *hard* into the caliper. We're taking gripping the prongs of the pads with pliers and pushing in HARD.

You're doing something very wrong.

The tri-align system is the post mount adaptor system where you tighten the bolts. When the rotor is slightly bent in a place, this is the worst system suited for it... since the caliper will align itself to the bend , if you get me? Now, if the caliper is preset slightly angled, thanks to a slight bend in the rotor, this'll mean the whole of the rotor has to get accustomed to the new angled position. Meaning gradual warping, and no real power...

Rotors do bend a little slightly, the bigger the rotor is the more it's going to bend. It might not be the rotor though, it could be the mount on the hub. When i had some shitty hub i took my rotor off that and put it on a new hub and it was dead straight.

The rotor will not warp if you have you avid set up at a slightly wrong. It just won't. I don't know where you got that from. Reset the avid up again, maybe do it a couple of times until you get it in a good position.

It may help to undo the rotor bolts and put them back on, but i doubt it'll make much of a difference, Adam told me to do that when my rotor was a bit crooked but he said not matter how you do the bolts it'd usually sort it's self out anyway. It didn't work but like i said it was the hub.

Edited by JT!
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Point is it's a new rotor... used for a few days. It was slightly bent out of the package from Tarty, and I put it on. For some reason the rotor decided to bend even more slightly, left and rotor in tiny tiny tiny increments. I can't exactly tell what the true straight orientation is. It' only shiftin left and right by 1mm or so though.

The tri-align system is the post mount adaptor system where you tighten the bolts. When the rotor is slightly bent in a place, this is the worst system suited for it... since the caliper will align itself to the bend , if you get me? Now, if the caliper is preset slightly angled, thanks to a slight bend in the rotor, this'll mean the whole of the rotor has to get accustomed to the new angled position. Meaning gradual warping, and no real power...

http://www.trials-forum.co.uk/forum/index....howtopic=127057

Avid BB7, 160mm rotor, with long Jagwire cable, can be used as front or rear brake. Brand new caliper, brand new SD7 lever, brand new cable. Rotor and pads have been used for 3 days; but hardly even bedded in yet!

40 pounds with FREE postage and packaging (note: on ALL online retaliers, none of them sell the Avid BB7 with the levers or cables; so it'd come to around and maybe even slightly over 65 pounds for a decent spec)

Pictures upon request.

Naughty.

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Haha.... you do realise that I have two Avid BB7s?

One with a short cable that is on my bike (the one in question on this topic),

and the long cable'd one that's sitting unused on a sofa ready to be despatched for anyone who wants to buy it.

:)

If you'd like, I can take pictures of both of them together in the same picture.

;)

I'll appreciate in future if people aren't so quick to judge! I would not sell a brake that I am using, especially not one that is having minor issues. The brake described in my for sale topic is a totally different Avid BB7 I do not use. That's why in the picture I sent you, it had a long cable and the Avid roundagon rotor that came with it. If you check in my 'Baby Pitbull' topic in Bike Pics, you'll see my actual used BB7 on the front of the bike with a Hope Saw rotor, as described in my posts in this topic. Both completely separate brakes, which I understand you might have got confused, but just to clarify they are two different individuals.

Sponge.

Edited by Sponge
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