Brake disc bolts

[darrsi]

Has anyone got any views on using stainless steel brake disc bolts on the front wheel at all?
Is it a good or bad idea?
I've had a look about the internet and there seems to be mixed reviews so was wondering if anyone actually has them fitted without any issues?
I've found good 'A4' bolts which are marine grade (ie: salt resistent) so should have good anti rust properties.
I wouldn't use them on the rear as that tends to get much warmer as it's not a semi floating disc unlike the front discs.
Any input appreciated, thanks. 

[bootz76]

its not corrosion you need worry about,its the strenght of the bolts.pro bolt do a kit but its not cheap :eek  i bought new ones from yamaha much much cheaper and i know they are strong enough

[Fazerider]

I would (and do) use A4 s/s bolts on the rear and would feel less comfortable about using them on the front.
Temperature considerations are not the issue: the rear does only a fraction of the work of the fronts so the slightly better conduction to the bolts is not a significant factor.
Shear strength is what matters. Most readily available s/s bolts have a thread that extends all the way up to the head of the bolt whereas the OEM bolts have a plain shank of a depth that matches the disc thickness. So the replacement bolts are effectively a smaller diameter.
Back-of-an-envelope calculations suggest that there is still a big safety margin for the rear, particularly since braking forces there are relatively small compared to the fronts. Even so, and despite the fact that the braking loads are shared across the two front discs, I'd err on the side of caution and stick to OEM bolts at that end.
http://foc-u.co.uk/index.php/topic,2361.msg18102.html

[Ben600]

I use stainless bolts on all of my bikes, I just take the originals to my local engineering supplier, and they match them up. never had an issue.
I use the relevant threadlock where needed, or copper grease on bolts that hold for example the fairing on.


I would say, go for it, just ensure you use a good grade stainless, and use the correct torques

[darrsi]

That's quite an interesting response, similar to other threads i've read, some people think "not a problem" and others are dead against it.
The reason i mentioned the rear was because last year i went to change the rear disc and every bolt was welded tight, the only one i got half way out then snapped and i had to get a new wheel. I don't know what bolts they were but i think a combination of more than likely being overtightened and the disc getting hot/cold throughout the years was the main cause of the fusion.
I read that stainless bolts in alloy are okay as long as they are greased to prevent the welding reaction happening.
I've noticed that the HT steel bolts on the front do tend to be prone to a little rust, and also the allen heads are quite soft, that's why i was considering the stainless ones.
A valid point by 'Fazerider' about the top part of the bolt being wider though, i hadn't thought about that!  :rolleyes 
After reading that old thread you've supplied i'm now having second thoughts. 

[AdieR]

If them plain shank bolts are the same ones as fitted to the R1 / R6, they're what's called "shouldered" screws, as far as I can see the shoulder is primarily for locating the disc (so the disc can't run out of "true" beyond a given tolerance in relation to the wheel) rather than any difference in shear strength values.

As for removing the bolts, a little heat (you don't need to go mad with it) will help; disc bolts tend to be Loctited (for good reason) - the heat will help soften it up.

R6 disc change Performance Upgrades Yamaha YZF-R6 Front Brake Rotor Install about 2 minutes in, and you'll see the "shoulder" quite clearly.

[darrsi]

I tried every trick at the time to get just one bolt out, including the heat treatment, but nothing budged them, i ended up taking my wheel into the engineers at work, they tried all of their tricks as well before finally gaving me the bad news!  :'(
I was only putting a new disc on, "Half hour job....." i foolishly thought to myself........  :rolleyes

[markbubble]

the way iv removed the disc bolts in past is to gently heat the area 1st the with a great fitting socket headed hex head give one good wack with an impact hammer,this has always worked as long as the heads of bolts are in good condition ie not chewed up,as for using stainless bolts i deffo wouldnt as already mentiond you need good strength so dont worry about the non rust stainless,if you want it to look great you could always paint the heads carefully,not perfect but next best thing!

[darrsi]

Seriously, everything was tried with those bolts, and if my machine shop engineers couldn't sort them then they were genuinely fooked!!


I always torque everything up properly but the fella who had the bike before me was a bit of a menace for over tightening things as i gradually found out over time.

[Fazerider]

When I changed my rear disc last year I had similar difficulties undoing the bolts. The screwlock Yamaha used on assembly seems to gain strength with time... I'd had minimal difficulty with the front discs, but have needed to change those every 3 or 4 years so the bolts hadn't had so much time to bond to the hub.


Cooking the rear wheel to about 50ºC softened the compound sufficiently on 4 of the bolts. The last two were really stubborn, I ended up taking U-channels of 3mm scrap steel with a 12mm hole near the end and welding them to the bolt heads. The higher temperature and extra torque I could apply was enough to shift them.





I was a bit concerned that the high temperature could have weakened the alloy, but was able to torque the replacement bolts up OK without the threads stripping so figured that the heat that did reach the alloy was conducted away fast enough to avoid damage.

[darrsi]

Once the bolt snapped i think i'd ordered a 2nd hand wheel within the hour, i'm a bit lost without the bike for transport so had to get a move on in getting it up and running again!