nerdy bolt question

Hello everyone.
I'd like some help with bolt sizes please...I would like to replace all the steel bolts on my tourer with titanium ones. This is essentially because I am an unashamed bike tart, plus I love my tourer and I'd like to treat it to some nice bolts. There's also a job lot going on ebay here and here ;)

I'd ask that you overlook the fact that I am a nerdy saddo for a moment and consider the following question: how do I find out the right thread size for an ultra galaxy frame to see if either of these bolts would work? There are M5 and M6 bolts on an ultra I think.


New Member
M5/M6 bolts etc - refers to the external diameter of the threads. To state the obvious, the metric and (bsp) imperial systems are most common for nuts and bolts, although there are a couple of other systems in use - quite common (!!) in the world of high pressure hydraulics, known as "pipe fittings" should you ever want to google it!!!

Now, if you were keen (or desparate) you can get what is an equivalent of "feeler gauges" for threads, which looks like one of those allan-key pen-knives. This has several different sets - for metric, for bsp imperial, also maybe unified, bsf, bsw etc etc.

What I would be tempted to do, if you were looking to check out what bolts are on your bike, might be to buy a thread gauge (which I always type guage btw), but more easily, you could buy a box of nuts, which you could get from an online toolshop, I bought some like these only cheaper - i.e. for a tenner, you should be able to get about 15-20 different nut sizes, which is cheaper than buying in ones from B&Q. I can't recall the company I bought a small box load from - basically because I needed a couple of good sized nuts for some reason... A decent hardware store might sort you out.... might be easier!!
(If you're really desperate I can check my emails at home - I'm sure I have the order confirmation somewhere!!)
Rather than playing with mosschop's nuts you could kill the fun by finding out what stem, mudguard etc is on your bike...from Dawes perhaps - or 'the bike shop'?

You could always play with the nuts in your spare time then - or save them for another thread:tongue:


Cut to the chase here - if the bike is less than about 20 years old then the bolts will be metric (as in M5 etc) and will fit.

However, the idea of Titanium bolts at the sort of cost they are makes little sense to me ..... but then I suppose you'll save soem weight, although getting a haircut before riding would probably save more than the difference in the bolts ;)



Über Member
Those screws on Ebay are 25mm long, that's a lot longer than you need for most bike applications. Either you'll have fun cutting titanium or you'll leave them at that length and no lighter than steel.
If you really want to save weight on a touring bike, there are better ways, maybe worth another thread. First suggestion the titanium rack from Tubus,mmm
Im not sure how much more Kirstie knows than to begin with, or how much Im going to help!!

Arent there just 2 sizes of bolt :

Frame stuff, racks , bottles etc which are M? x length.
Stems, brakes, ders, seatpost clamp etc which are M? x length.

Im interested in this one for the even shallower reason of getting some new bolts that are all the same allen key size!!!

A big bag of stainless jobbies will do me though.


New Member
Generally racks, water bottles etc are M5. Stem, seat post clamp etc are M6. However there's a lot of exceptions to the rule and some very odd sizes out there.
Thanks for your suggestions and advice, and for the predictable innuendos about nuts ;) I have a tubus airy on order, as it happens... and yes, as I said, I LIKE TITANIUM. The poor tourer, whilst it's a lovely solid build, has no bling - ie no carbon or titanium anywhere on it and in my view this should be remedied asap. I don't buy excess shoes or bags or jewellery, I buy titanium and carbon bike bits. Now to some of you boys I'm a dream woman...

Now go on, tell me about nuts! :biggrin:
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