105 Braze on Front Derailleur Support Bolt

photonic69

Dear Forumites.

I have recently installed a 105 5800 groupset on my Giant Defy Aluxx bike. The FD uses a support bolt and plate to fix the position. However, due to the shape/size of the seat tube the support bolt is screwed all the way through with very little thread left on it. Ideally I want to put in a longer bolt.

Anyone know the thread size/pitch of this? Item 7 in the diagram in the link:

https://si.shimano.com/pdfs/ev/EV-FD-5800-3713D.pdf

It uses a 2mm Allen key to wind it in.

Many thanks

lemonenema

have you got a way of measuring the width of the bolt?
these are the most common sizes
M2 2mm
M2.5 2.5mm
M3 3mm
M3.5 3.5mm
M4 4mm
M5 5mm

Id guess its an M3 but without seeing it in person its hard to say. The other thing you could do is take it with you to a local hardware store / B&Q and choose on that is the same width and thread spacing.
Ive got a box full of old bolts and screws for just this sort of situation, very handy.

photonic69

lemonenema wrote:

have you got a way of measuring the width of the bolt?
these are the most common sizes
M2 2mm
M2.5 2.5mm
M3 3mm
M3.5 3.5mm
M4 4mm
M5 5mm

Id guess its an M3 but without seeing it in person its hard to say. The other thing you could do is take it with you to a local hardware store / B&Q and choose on that is the same width and thread spacing.
Ive got a box full of old bolts and screws for just this sort of situation, very handy.

Thanks - tried our local hardware store that usually have everything - except anything suitable in this instance. B&Q - it's not something they would readily stock. I guess I can take it out and measure it as I have some vernier calipers. Is it the outside width of the thread that determines its size? I could probably get something online.

Matthewfalle

have you been to a bicycle shop and asked them?

me-109

I don't expect you will find a long grub screw anywhere, even at a nut and bolt stockist (try yell for any local to you). If there is room to get a bolt head in you may stand a chance. Alternatively see of you can make a thicker support pad or add something between the existing pad and bolt.

timothyw

While it is desirable to fit this bolt you might find that the front derailleur works just fine without it - I set up my 5800 groupset a couple of years ago and had no idea what the plate was for, or that the bolt was even there. It was fine. I'm reasonably sure I put it on a few months later but it didn't make a huge difference.

You also might find it easier to thicken the plate somehow or other - superglue on a little bit of hard plastic or something.

Otherwise you might want to take the opportunity to buy yourself a vernier caliper to measure the existing bolt - I got a cheap digital one from Aldi (or perhaps lidl) a couple of years back and it has proved itself very useful.

Matthewfalle

have you been to a nut/bolt factor? they will have them but you have to know what you are asking for.

lemonenema

does it have to be a grub screw though?
If it does you can make your own if youve got a vice, you can cut the head off the bolt and make a slot in the top with a hacksaw for a flat screwdriver

photonic69

lemonenema wrote:

does it have to be a grub screw though?
If it does you can make your own if youve got a vice, you can cut the head off the bolt and make a slot in the top with a hacksaw for a flat screwdriver

Sounds like a plan, Stan. Like your thinking

Alejandrosdog

Grub screws to your hearts content here

https://www.westfieldfasteners.co.uk/A2 ... _M2.5.html