Mudguard bracket issue...

[andyoxon]

I always manage to find some issue when trying to fit new mudguards.   35mm SKS Bluemels - with what looks like adequate clearances, however the fork crown brake bolt is too large a diameter for the mudguard bracket by 1-2mm.  I tried fixing the bracket on frontside of the fork, but this reduces the clearances/not great.

Any ideas?  File the inside edge of the mudguard bracket down with rounded edge file?

PXL_fork1 by ao, on Flickr

[LittleWheelsandBig]

https://www.sjscycles.co.uk/brakes/problem-solvers-sheldon-fender-nuts-10-32-mm-per-pair/

[yoav]

That’s what’s I’ve done. For some reason, mudguard manufacturers haven’t cottoned on to the fact that the bracket has to fit the wider nut of recessed brake bolts rather than the bolt itself, even though it’s been about 30 years since the change from external to recessed nuts.

[andyoxon]

https://www.sjscycles.co.uk/brakes/problem-solvers-sheldon-fender-nuts-10-32-mm-per-pair/

Thanks.  Look good.  Shame they would be 85% of the cost of the mudguards themselves, but oh well.

edit.

[LittleWheelsandBig]

They can be bought as a single nut.
https://www.sjscycles.co.uk/brakes/9-gilles-berthoud-brake-spindle-screw-for-mudguards/

[andyoxon]

Thanks.

It's a shame that my existing miche recessed brake nuts have a threaded hole through the centre, but the SKS brake bolts are very slightly too small a diameter and simply push straight through without engaging the thread.

Anyone know what the diameter of the SKS bolts is (or Miche nut internal thread)?  I guess I could source some inexpensive bolts (instead of SKS) of the right diameter to fit...

[LittleWheelsandBig]

M5 for the mudguard bracket and M6 for the brake bolt is standard.

[andyoxon]

Thanks.   Ok I'm getting this (I think), slowly...  I can see now that with the existing miche fork nut, although it has a right-through internal thread, when tightened up into the fork-brake spindle, it doesn't have enough depth of internal thread for another fixing bolt to go into the back to fix the mudguard.  Hence the Problem Solver nuts have that extra 'collar' / depth space.   

Guess I still need M6 bolts to attach mudguards to the problem solver nuts?

[LittleWheelsandBig]

Yes, M6 to attach the mudguard bracket to the Problem Solver nut.

[andyoxon]

Thanks.  So AFAIUI I need the PS front 13mm nut - rather than 30mm, & 10mm for the rear?

Yes, M6 to attach the mudguard bracket to the Problem Solver nut.

6x10mm OK?

[LittleWheelsandBig]

That should be fine.

I don’t know where my previous M5 comment came from. Brain fart, I guess.

[andyoxon]

Thanks again LWaB.   

[hubner]

Any ideas?  File the inside edge of the mudguard bracket down with rounded edge file?

If the bracket is wide enough, I would try that first.

[BFC]

Making the hole in the bracket fit the oversize bolt is the easiest fix for most people.

Making the hole bigger does present a few pitfalls though - mudguards are generally a pain to work on and the riveted mounting hardware can easily overstress or melt the plastic.

Best to clamp the edge or end of the bracket in a vice and support the mudguard (extra person helps!). Keep a check on the temperature of the bit of metal, especially if using powered tools like small grinding wheels rather than an old fashioned file.

I have modified many of these, and in a few cases made new ones from scratch and fitted them for particularly close fitting set ups with lack of clearance to the underside of the headset.

[hubner]

Yes, well £18.50 for two nuts or £6.50 for one nut versus a bit of filing, take your pick.

[LittleWheelsandBig]

I have tried opening out the bracket slot to fit an Allen nut and it is a pretty crap solution. The thin metal bracket tends to be deformed/ spread by the brake nut as the Allen nut only bears on the bracket via two very small contact areas. Combined with a unicrown fork and rounded edges to the brake nut's contact points leads to the bracket slot tending to spread apart when the nut is appropriately tightened. If you fitted a flat washer (with a really big hole) under the brake nut, it worked ok.

[hubner]

That’s what’s I’ve done. For some reason, mudguard manufacturers haven’t cottoned on to the fact that the bracket has to fit the wider nut of recessed brake bolts rather than the bolt itself, even though it’s been about 30 years since the change from external to recessed nuts.

Maybe mudguard manufacturers recognise that nut fitted caliper brakes are much better than recessed brakes for attaching mudguards. And the bracket can go between the brake and fork crown or seat stay.

And also that a lot of mudguards are fitted to bikes with cantilever/v brakes, which don't need a bracket with a wide slot.

[andyoxon]

Update.  With minimal filing of the mg bracket, I managed to get the recessed front nut to fit through the mg bracket, and it seems ok.  Long mg nose is tricky to adjust/align, as the clearances are bit tight.

But, rear brake/mg and that crappy plastic SKS bracket...  Again, with a bit of filing the recessed nut goes through the bracket, however there's now not enough thread for the short nut to grip the brake spindle/bolt.  I may try and scavenge a thin metal bracket from spare mudguards, otherwise wondering what problem solver nut may work at the rear.  Can I remove the single brake 2-3mm wide steel 'grooved' washer (next to brake caliper on spindle) to release more depth of thread?  Or bad idea?

[LittleWheelsandBig]

You should be able to remove the spacer but the plastic bracket is likely to deform as you tighten the nut because of the small contact area. I am always concerned about that sort of thing in a safety-critical component. Traditionally you need as much engaged thread as the diameter of the bolt for full capacity.

A steel bracket is a much better option.

You need a short (10mm?) Sheldon nut on most brake bridges.

[andyoxon]

Ok thanks, the brake washer/spacer releases enough thread, but I fully agree, what are SKS thinking with this ridiculous plastic component which becomes part of the brake assembly.

[andyoxon]

Found a rear metal bracket* on some removed, ancient bluemels.  The thin bracket has to sit on the brakes side, backwards of the brake bridge, otherwise it prevents (with brake spacer in place) the recessing nut from gripping enough thread. It does grip some thread, with bracket next to recess nut & brake spacer removed, but you can tell it's not much.

Now I know why I haven't put mudguards on this bike, since finishing it back in April.   Anyway should stop a ton of crud coating the front mech, among other things.

All done I think, clearances look OK - though thought I'd cut away the edges at chainstay bridge, as 35mm mg edges curled in slightly towards 28mm tyres on this RRS frame.

PXL_mg by a oxon, on Flickr

*discovered available for £5 Wiggle.  Why don't SKS supply a metal bracket?

[LittleWheelsandBig]

Plastic brackets don’t fail from fatigue and most mudguards in Germany are fitted to bikes that don’t have caliper brakes (V-brakes or disc instead).

[andyoxon]

Plastic brackets don’t fail from fatigue and most mudguards in Germany are fitted to bike that don’t have caliper brakes (V-brakes or disc instead).

Fairynuff. 

[nmcgann]

Plastic brackets don’t fail from fatigue and most mudguards in Germany are fitted to bikes that don’t have caliper brakes (V-brakes or disc instead).

All my metal rear sks brackets have failed over the years, they either crack or chew their way through the mudguard with the vibration.

The most recent plastic one is still going despite being an offence to my engineers eye. I put a thin washer between the rear brake nut and the plastic bracket and that has been fine.