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Just installed my rotors to some brand new hubs and think i fokked up with x-threading on the front hub.
The lock tight on new nuts always makes them feel tight but one bolt went in feeling as normal but wont tighten.
5 bolts tighten to 4nm happily. The other tightens to 3nm but i can feel if i go further the threads will strip.
Now i know the instant knee jerk usual forum response is “do use it. Death face plant etc.”
I think The reality is more thats not going to catastrophically fail and at worst may loosen a bit. 5 other bolts will keep the rotor in place, disc is flush and its turning force not pull force on the bolt so doesnt need high torque.
but the perfectionist in me doesn't like knowing theres a “sub-optimal” part!! And maybe I am wrong and will die a horrible painful death!!
Live with it? Run a longer bolt and put a nut on the back? Helicoil? I know mixed views on helicoils but they hold head gaskets fine.
Rotor bolts are M5 but anyone know the thread pitch too? Helicoil repairs are M5x0.8 so presume M5 rotor bolts are also metric and 0.8?
A longer bolt (Screwfix?) and a locknut would be my quick and cheap solution.
5 bolts will be fine
I thought this was going to be about poor choices in lycra
5 bolts is fine. I ran one like than for years. XC racers used to routinely go down to just 3, for weight saving.
I've never used a torque wrench on rotor bolts. If it feels right I'd go with your gut.
Threadlock it?
Cracking. Thanks chaps. I vaguely recall 3 bolts in racing.
I’ll live with it and just put a little more thread lock on to take up some of the gap and stop it rattling out.
Panic over for now!
Found a longer t25 bolt in the man cave. Enough good thread left to nip up to 4nm without feeling like it’d strip.
Doddy on GMBN says he runs 5 bolts with the 6th a cleat bolt in case he loses one of those. It'll be fine you won't die. Unless you go near a Robin nest.
Be reet.
Some rotors BITD only had 4 bolts (Cannondale maybe?) so it would have been fine. I never bother with a torque wrench just go on feel - well done for using both methods though to avoid a problem!!
A person I know who shall remain nameless was left unsupervised to fit their own rotors when they arrived on a riding holiday.
After leaving them to it for quite a while and finishing building both bikes they were still messing about with the rotors.
Then came the question "why are all the bolts tight but the disc still seems loose?"
Brand new hub that'd been fitted before the holiday now had all six bolts cross threaded. 😮
Managed to remove all the bolts and run a tap through and fitted brand new bolts and it was fine.
I'm not allowed to tell anyone about it though. 🤣
I have hubs with both 4 and 5 bolt fixings for discs so in practice I am sure 5 out of six should be ok but there is no way I could be happy riding a bike with a stripped disc bolt. Helicoils are cheap easy and permanent fix for stripped threads. I would be putting one in
Pretty sure I remember reading that Steve Peat ran 3 bolts. Which is more than enough if you have a mechanic who checks and perhaps re-threadlocks them after each run. Less so if you just chuck the bike in the garage after a ride.
Counterintuitively, the braking force stresses the join between the rotor face and the hub face; there should be no shear forces on the bolts themselves (unless the bolts are all loose). So the torque setting is only really to prevent the bolts from loosening themselves.
But yeah, 5 working bolts is more than enough fine IMHO. IANAMechEngineer.
I've seen 3xTi and 3xAl bolts being used.
And 3x steel.
Funnily enough, never seen 6xAl.
5 of 6 should be fine as long as it's a decent disc (wouldn't fancy it on a 70 gram Ashima though, but thats just me.)
Helicoil? I know mixed views on helicoils but they hold head gaskets fine.
Mixed views? From who. They hold aeroplanes and cars together perfectly adequately and are a standard component across many other industries.
A quick browse on other bike forums where stripped threads and brakes are in the same sentence plus a fair few comments and observations when a disc mount stripped on some carbon forks a few bikes ago. Steel insert in the forks. But even bike shops were saying not to trust helicoil.
Guess they could have been worries about the anount of steel insert to drill at but general consensus was NO.
Subsequently done more reading and I’d most definitely trust then. Not so sure I’d trust myself to do it though which is a different matter!!
Yeah. Thin wall insert, you're unlikely to be able to helicoil that, pretty much anything else on a bike is fair game.
Awaits newspaper article about injured cyclist found with disc rotor embedded in leg. 😀
You’ll be fine with five bolts (I know lots of people who only use 3 because they’re weight weenies).
Not today! Survived 20mls without a noise or grumble so longer bolt and threadlock did the trick.
LBS said they’ve had a few and rechasing threads might work if it gets worse. For now….sleeping fogs lie and only the dog off a leash that nearly killed me. Not the bike 😁😁