[Closed] Is it dangerous/Would it be dangerous to .....

Get it heli-coiled at a local engineering company..
Will be stronger than the original thread.

I'd use it without any worries, in fact I have done

Steve Peat's V10 for the WC Downhill in South Africa a few years ago. He ran three Ti bolts on his rear rotor to save weight.

Although you probably use your brakes, where as he doesn't. much.

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I'd do it, but then I did a Dark Peak Ride knowing I'd got a broken front spoke the other day

It'll be reet but if it bothers you tap it out an use an M6 bolt

3 bolts are good enough for some weight weenies / World Cup DH champs...

You'll be fine. Choose a rotor with continuous material between the bolt holes to spread the load evenly to the other bolts.

I know loads of people who only run 3 as above. I've had a few fall out over the years and managed with 5 for an entire month in MOrzine without any problems.

Tom KP

Well I believe that an assortment of world class DHers have used only 3 bolts for race runs, although they probably don't actually use the brakes much...

Helicoil is an easy fix (have done it in the past)

Personally, I'd be happy riding 5 bolts, and just keep an eye on it.

Slightly longer bolt?

Thanks all.

Sadly the thread is fubared all the way through.

Does a helicoil work by drilling to a slightly larger diameter then inserting/bonding in a new threads?

Yes, to do an M5 helicoil you need to drill to 5.2mm, tap the hole with the relevant M5 helicoil tap then thread the insert into the tapped hole..pretty straight forward

or .... you could just get a longer bolt and put a nut on it.
You may well die,but it won't be because of the nut 🙂

I'd just carry on. Well, I might blob in some chemical metal and cut a thread in it just so I can fit a bolt, because otherwise people are bound to notice and helpfully tell you about it 20 times a ride.

Drilling out to M6 would remove more material and mean you have to drill the disc hole too so either helicoil or drop in some chemical metal or epoxy etc and re-tap as suggested.

Helicoil kit is not expensive but be careful drilling if you use a hand held drill http://www.ebay.co.uk/itm/Motamec-Tools-M5-x-0-8mm-Thread-Repair-Recoil-Re-thread-helicoil-insert-Kit-25pc-/230946510684?_trksid=p2054897.l5661

[quote=letmetalktomark ]Sadly the thread is fubared all the way through.

Oh I don't know, I thought there were actually some quite helpful suggestions.

As above, I'd just fill it with some epoxy to make threads (should be able to tap with a bolt if you do it right), then use threadlock to keep the bolt in without needing to tighten too much. That should still take some of the load then if you're really worried about 5 not being enough.

If you're truly afraid you could araldite the bolt in, remember that in use it's resisting shear forces, not tension. But I find WC downhillers leaving three of them out deliberately as fairly compelling evidence that you'd be fine without it, if you remove two more to keep the wheel balanced. 🙂

Just get it welded on to be sure.

I guess the issue with Steve Peat is that he has someone to check all the bolts are tight after each run. Three is fine, but if one comes loose then you're potentially in trouble. Certainly I wouldn't routinely use three because I know I'd forget to check them. But yes, five will be totally fine.

Helicoil is another option. Also, if the disc tabs are small, sometimes you can use a longer bolt and stick a nut on the other side.

EDIT: Waaay too slow

I would have said the braking forces are transferred through the contact faces of the disc and hub and not as shear force through the bolts. They are then acting in tension not in shear. If they were in shear they would actually be bolts (as people keep referring to them) and not machine screws which they are and thus shouldnt be taking shearing forces into the threaded area from the thin disc.

Same as with car wheels and brakes - the bolts provide the clamping force to the wheel hub. The wheel bolts/studs do not take the forces in shear.

That's a good level of pedanticism - I'm learning 🙂

Having thought about it, I think you're right. If the [s]bolts[/s] [i]machine screws[/i] were resisting shear then you might expect them to end up with flats on the thread where it's has been damaged by the disc rotating. I have never seen this.

thread a zip tie through the hole. It the other bolts strip, at least you won't lose your disc

thread a zip tie through the hole. It the other bolts strip, at least you won't lose your disc

i cracked a hope hub using it with 5 bolts....

thomthumb - Member

i cracked a hope hub using it with 5 bolts....

I wouldn't worry about that, lots of people crack Hope hubs using 6 bolts.

I felt sick when I discovered I had only 1.5 bolts holding my rear disc on in the middle of a winter ride. 😯
Tightened the remaining bolts back up and stole two from the front, it was fine.
Im pretty sure I'd taken the disc off to clean it or something and hadn't nipped them back up. 😳

I have been running a pro2 rear in the lakes for 2 years with 5 then 4 bolts (because I am hamfisted). Been fine for everything from weekly rocky descents to the EWS/UK GE.
Im 92kg and use the brakes quite a bit.

Updated to add:
I would be more worried about the rotors than the hub, I did hear an anecdote about someone trying the 3 bolt weight saving trick with a set of the formula discs [url= http://www.chainreactioncycles.com/formula-1-piece-solid-6-bolt-rotor/rp-prod116886?utm_source=Google&utm_medium=Shopping&utm_name=UnitedKingdom&gclid=CjgKEAjwiumdBRDZyvKvqb_6mkUSJABDyYOzORY_b2jhC9IeLjn9QDBKOYTkZQ2259_bGIlpi4YMd_D_BwE&gclsrc=aw.ds ] these ones...[/url] and it all going horribly collapsy.

5 properly tightened rotor [s]bolts[/s] machine screws with a gob of Loctite 242 on each, checked regularly are going to be more secure than the 6 screws without loctite, looked at hardly ever that you're likely to see on a lot of bikes.

I would have said the braking forces are transferred through the contact faces of the disc and hub and not as shear force through the bolts.

That being the case they're barely taking a load at all, on with the araldite. Or playdo, if you're out of araldite.

That's a waste of playdoh.

The big question tht this thread has thrown up is why on earth would a WC downhiller give a crap about the weight of 3 ti bolts on the rear of his hub...

or have I missed the joke somewhere?

marginal gains innit.

On both my xc and 4x bikes I only run 3 ti bolts in each wheel 🙂

tpbiker - Member

The big question tht this thread has thrown up is why on earth would a WC downhiller give a crap about the weight of 3 ti bolts on the rear of his hub...

I think that pic's actually from Canberra, where he won the world champs my 0.05 of a second... And they went to town on that bike- he used a set of enduro wheels with all the paint stripped off, all the seals and grease removed from the bearings... Maybe all that stuff gains you 0.05 of a second or maybe just knowing that you've sweated the details down to the last and the bike is as perfect as it can be.