Brake anchor arm bolts

basketcase · Post by **basketcase** » Tue Feb 13, 2007 7:01 pm

Could someone tell me the size and thread of the bolts holding the mudguard stay/brake anchor arm to the fork slider. My bike is a G2CSR, and now needs three out of the four heli-coiling!
Cheers, basketcase.

Tolly · Post by **Tolly** » Tue Feb 13, 2007 7:21 pm

They should be studs, course thread into the fork. Don't quote me but I think the course thread is whitworth and the other end, for the nut, is cycle thread.

ajscomboman · Post by **ajscomboman** » Tue Feb 13, 2007 8:09 pm

The brake torque arm slider has studs with 5/16th whitworth thread that screws into the slider and a 5/16 cycle thread on the other end to hold the mudguard and torque arm in place. On the other slider the mudgard is held in place with 5/16th whitworth bolts. If you dont use bolts its a devil of a job to remove the mudguard.

Biscuit · Post by **Biscuit** » Tue Feb 13, 2007 8:12 pm

Believe Tolly, under no crcumstances whatsoever use bolts here, never NEVER. The thread in the slider is BSF.

Biscuit · Post by **Biscuit** » Tue Feb 13, 2007 8:15 pm

Sorry Rob, all the bolts and studs in the slider are BSF, they ought to be Whitworth, but there you go. Burman and Lucas are the only ones to use whit.

lawrence · Post by **lawrence** » Tue Feb 13, 2007 10:48 pm

JUST TO MAKE IT QUITE CLEAR, BOLTS ARE POTENTIALLY DISASTROUS HERE. IT MUST BE STUDS!

These act as a fork brace in addition to holding the brake arm. If the fastenings come loose you are in trouble. There is no room for chance.Edited by - lawrence on 13 Feb 2007 10:51:49 PM

basketcase · Post by **basketcase** » Wed Feb 14, 2007 3:18 am

Funny, I was supplied with bolts when I replaced them in stainless. Didn`t seem long enough, now I know why!! Would it be sacrilige(?) to replace with metric STUDS when I have to helicoil the sliders?

Sorry Lawrence but when building up a lightweight from a box of (wrong) bits things are almost always worse than you think.

ajscomboman · Post by **ajscomboman** » Wed Feb 14, 2007 7:22 pm

Alan you're quite correct about BSF not whitworth. That'll teach me to jump in too fast. I will still stand by the fact that only the torque arm slider has studs. My 61 mod 8 has only ever been to bits 2 times in its entire life both times by myself and came with bolts on one side and studs on the torque arm side. If studs are used on both legs its bloody impossible to remove the mudguard. The lightweight and both outfits use the same setup and i've never had any bolts come loose after 17yrs using this method. I do use lock washers under the bolts.

itma · Post by **itma** » Wed Feb 14, 2007 8:14 pm

Sacrilege? yes
Remember you are only the keeper of your bike for now, theres enough confusion as it is, without creating more for a future owner.
Another trouble spot with bolts aside from the fact few can tell the difference between a bolt and a set screw,or why it makes a difference ; is that if the bolt is a fraction too long it`ll break into the slider itself.
Mixing threads is bad practice, but worse to my mind is that it demonstrates a lack of mechanical finesse,
I am none too keen on this fad for stainless steel every where either, as it is possible to get the wrong grade of steel, leading to potential hazard. Stainless steel might not rust, but a lot of it lacks the right kind of stress resistance.Better safe than sorry with fixture like this

TommoT · Post by **TommoT** » Wed Feb 14, 2007 9:42 pm

..I am still missing the technical/mechanical explanation why studs are safer than bolts here? If either work loose it will eventually lead to the loss of brake torque arm fixation, with disastrous results? Is the theory that if a stud/nut is used, only the nut will work loose, leaving the stud in place to provide some degree of fixation? If so, I cannot count the times I have tried to loose a nut, with the result that the stud comes out too! In an ideal world where the stud is always held in place, and only the nut moves, the argument is valid, otherwise it is not? The fact that the mudguard bridge acts as a fork brace, may be valid, but temporary loss of brace effect will not lead to immediate disaster. Please give me the run-down here?