Disc bolts query.

[milleplod]

When I replaced the front discs on my ST a couple of years ago, like a good boy I also replaced the (expensive) bolts, bobbin (?) things and the spring washers, all sourced from Rainbow BMW. Much to my annoyance, a few of the bolt heads have 'gone off', and look really manky. I've wire brushed them a few times, but the mankiness, inevitably, returns, and they really stand out.

Can I simply remove the offending items one at a time, and replace with a few new ones.......or am I going to have to have the wheel off and replace everything....again?! I'm wondering if taking one bolt out and just sticking a new one in will do something unmentionable to the left-in-situ bobbin and washer. Anyway, if its a case of all-or-nothing, I think it'll be a set of titanium ones this time, as I think they're actually cheaper than a set of OE ones.

Pete

[SP250]

Couple of options Pete
Either replace with new - but make sure they are of the correct shear and tensile strength i.e. don't use SS (I am not sure about the correct grade of titanium).
Or take the old ones out and blast clean them and then paint or plate or zinc passivate or just clear lacquer them.

[milleplod]

Thanks for the reply. Is it 'safe' do you think, to take just one or two out, refurbish and then refit, having left all the other bits and pieces in situ? I think a refurb makes more sense considering its only the odd bolt that looks bad - I'd never thought of using varnish tbh!

Pete

[SP250]

Pete

As no-one can do all 5 at the same time (unless they did it that way at the factory with a 5 head, torque sensing screw-driving machine), I would say it's ok to remove one at a time and clean/refinish it then replace.

Though personally would take all 5 out and dismantle the whole lot and check to see if the rest of the bobbins/thrust and spring washers were servicable.
Do the necessary and then replace all together.
That way you get more of a safety/wear check on the other components and you can thoroughly clean them all before reassembly. Also if you used the later rubberised thrust washers, they may be prone to more wear than the originals (all they did was to quieten down brake squeal).

My R1100S has done 32,000 miles and has only had new pads, the discs and mounting bolts/washers etc. are all still the original ones.

Hope that helps

[milleplod]

Thanks John. I replaced the discs 2/3 years ago as one had a very slight, but very annoying, warp in it - it felt horrible through the lever. The thrust washers are all-metal ones, I've never had any brake noise at all. I think I might clean up the ones that look manky in situ, and find some decent varnish for them, that should do for now, then perhaps replace the lot over the winter.

Thanks again,

Pete

[dave the german]

Dremel with a copper wire brush does a good job - get the brushes that will fit in the middle of the bolt

[Humbug]

You will be fine one at a time as long as the washers are not split.
I have two new sets of bobbins and washers somewhere that you are welcome to from when I replaced the discs on my 12S. I will find them and let you know the reference number of them if any good?

[nab 301]

Can I simply remove the offending items one at a time, and replace with a few new ones.......or am I going to have to have the wheel off and replace everything....again?!
Pete

I guess the bolts use threadlock so it may be necessary to clean out the threads in the wheel before replacing in which case it will probably be easier to remove the wheel.

[dave the german]

The bolts are supposed to be one use stretch bolts - new are £1.50 each. They come of easier with heat too. Is that BMW trying to squeeze more money out of you?

[Pete.]

Single use stretch bolts with wavy washers under the head? Doesn't make sense to me.

[milleplod]

I think they're sold as single-use because they come with BMW-approved threadlock already applied, the super-strong stuff capable of stripping the thread out if you don't apply heat before dismantling! For that reason, I've decided I'm happy reusing the bolts once the locking compound is cleaned off them, and out of the hole they screw into.

Pete

[Pete.]

Now that does make sense. I did the same when I replaced the wavy washers on my first 1100s. I cleaned off all the threadlock and just applied new stuff.

[dave the german]

Bolts2go are selling sets of 10 bolts for £8.99 if you want to replace

[milleplod]

Bolts2go are selling sets of 10 bolts for £8.99 if you want to replace

Thanks for that, a bargain if they're right for the ST. Looking at the parts system, all the models have M8 disc bolts, but there's quite a few different lengths - there's 2 alternatives for the ST. I've mailed bolts2go for more info, in the meantime I think I might have one of my old ones in the garage somewhere so I'll try to find it and see how long it is.

Pete

[milleplod]

Just had a reply. The ones they supply are M8x20 - the parts system says M8x22 or M8x25 for my ST, depending (I think) on which discs are fitted. I've turned the garage upside down but can't find an old bolt to measure, so I might have to resort to taking one off the bike to check.

Pete

Further update....the ones on my bike are 20mm, I got them from James Sherlock, together with the new discs and other fittings, so I've ordered a set for £8.45 including delivery, a bargain!