Author Topic: Gilles berthoud metal guards  (Read 1947 times)

Ben T

Gilles berthoud metal guards
« on: 28 March, 2021, 06:21:06 pm »
Re GB metal guards, I would like to prevent stress fractures, but also would like to hear of others' experiences of how they have used the provided attachment bracket to attach the guard to the seat stay.

What type of seat stay does it fit? It is like an approx inch diameter disc, with a small cylinder protruding out of it, with a longitudinal bolt hole. But the cylinder isn't tall enough that the inch-diameter disc bit doesn't foul the seat stay, if that makes sense?

So, when I got some about 6 months or so ago I used a custom L-bracket - made out of some 2mm x 15mm steel that I just bent to the right angle.
Thought that would be fine, but it's resulted in a crack / stress fracture. Initially it went a bit rusty like this and cracked its way off the bolt:



So I basically hammerited it, replaced the bottom washer with a larger 'plate' and put it back together. This was fine for a bit, but has now resulted in a crack all the way across:

 


I thought I'd already done the most important thing to prevent stress fractures which is to make sure the guard isn't under stress i.e. being held in position against its natural tendency - i.e. if I remove the seat stay bracket, it stays in the same position, instead of springing into a different position
Other measures I can think of:
don't mount a light on (it's one of those very small dynamo ones intended to be mounted on mudguards)
don't mount mudflap on (it's a GB one)
put an extra stay on (I will have one spare - although this could put stress on the dropout due to the need for a longer bolt to go through both)
use a double bolt attachment like I have on the front one:



But not sure which of the above are most effective/necessary. Thought one of the main benefits of metal mudguards was that they were stronger but if they still crack what's the sodding point!  I'm going to try one more pair cos these do have the advantage of being good looking, very well shaped, and actually pretty quiet and rattle free apart from the 'clonking' due to this issue, but if they crack again I might have to just go back to plastic with one of those 'bridge' affairs and just make do with a seat post mounted light.

LittleWheelsandBig

  • Whimsy Rider
Re: Gilles berthoud metal guards
« Reply #1 on: 28 March, 2021, 06:28:20 pm »
HK’s Trykit has a GB front mudguard. I bolted a cut-down Nylon L-bracket to the fork crown and mudguard. Like https://www.tredz.co.uk/.Flinger-Mudguard-Bridges_122903.htm It has been reliable for several years and has a long RAW mudflap.

GB mudguards are mostly designed for frames with mudguard fittings tucked under the fork crown and brake bridge. The bolts are radial to the hub axle.

Are you talking about a daruma bolt? https://www.velovitality.co.uk/products/fork-daruma-for-mudguard-fitting?variant=954448237 It slides over the brake bolt through the bottom of a steel fork crown. It takes the place of a dedicated fork crown fitting.
Wheel meet again, don't know where, don't know when...

Ben T

Re: Gilles berthoud metal guards
« Reply #2 on: 28 March, 2021, 06:46:08 pm »
HK’s Trykit has a GB front mudguard. I bolted a cut-down nylon L-bracket to the fork crown and mudguard. Like https://www.tredz.co.uk/.Flinger-Mudguard-Bridges_122903.htm It has been reliable for several years and has a long RAW mudflap.

Interesting.  I can see how one of those would fit to the brake bridge, but how did you actually fix it to the guard itself though? Does one of those flinger mudguard bridges actually fit round a GB mudguard as it is even with those thick rolled bits at the edge for the light cable - or are you saying you modified it a bit - did it require drilling the guard?


GB mudguards are mostly designed for frames with mudguard fittings tucked under the fork crown and brake bridge. The bolts are radial to the hub axle.

Are you talking about a daruma bolt? https://www.velovitality.co.uk/products/fork-daruma-for-mudguard-fitting?variant=954448237 It slides over the brake bolt through the bottom of a steel fork crown. It takes the place of a dedicated fork crown fitting.

Yeah, pretty much - that's what you get with them.
I just can't see how that can mount to the rear brake bridge that I've got (even with it being unused by a brake due to having discs)

LittleWheelsandBig

  • Whimsy Rider
Re: Gilles berthoud metal guards
« Reply #3 on: 28 March, 2021, 06:51:02 pm »
I chopped off the curled sides of the bracket and just used a vertical SS bolt to connect the adapted bracket and the mudguard. The bracket was then bolted to the fork crown exactly as for most mudguards. The Nylon bracket gives a touch of flex and doesn’t work-harden or fatigue like bent metal. Leather is generally a better mudguard washer than rubber.

There are several width variations of the plastic bracket and one of them may fit your mudguard. GB mudguards come in a few widths, so who knows what you have and whether the combination is possible.

A Trykit is an upright tricycle, so the rear mudguard is sitting in the shed.
Wheel meet again, don't know where, don't know when...

Ben T

Re: Gilles berthoud metal guards
« Reply #4 on: 28 March, 2021, 06:57:13 pm »
I chopped off the curled sides of the bracket and just used a vertical SS bolt to connect the adapted bracket and the mudguard. The Nylon bracket gives a touch of flex and doesn’t fatigue. Leather is generally a better mudguard washer than rubber.

Ah ok, yeah I wouldn't have thought they'd go round.

When you say a vertical SS bolt, you mean just one in total - or two, one on each side? cos I suppose although one would probably be enough for the front guard, but there might be enough material in contact with the guard to have one each side.

I'll try using leather for a washer, cheers for that.

I discovered they actually sell this: https://www.sjscycles.co.uk/mudguards/gilles-berthoud-fixing-bracket-set-for-rear-fender-on-brake-bridge/
which backs up my theory that two holes might help spread the load (but I've probably still got some of the same metal I used before left)

LittleWheelsandBig

  • Whimsy Rider
Re: Gilles berthoud metal guards
« Reply #5 on: 28 March, 2021, 07:51:25 pm »
Just one bolt with a modified penny washer. Now you know why folk moan about fitting metal mudguards. There usually is a lot of fiddling needed to get them to fit perfectly. Plastic guards are less hassle/ more forgiving but not as pretty.
Wheel meet again, don't know where, don't know when...

Re: Gilles berthoud metal guards
« Reply #6 on: 28 March, 2021, 08:28:07 pm »
I think the problems arise from the fact that the normal fitting kit is based on a traditional french randonneuse mounting in which the mudguards fasten into the fork steerer, hanging off the front brake bolt and at the back with a vertical bolt (just the one) that went into a rear brake bridge with a vertical, not a horizontal, hole. Traditional french rear brakes  (or at least some of them) actually fastened with a vertical bolt and a sort of U-shaped fitting on the brake. Iremember looking at a Berthoud fitting kit when they still had a paper catalogue over a quarter of a century ago and taking a while to get my head around it. I am still surprised that they should continue with this style of fitting when 99.9% of bikes on the market can no longer use it but there you are, that's errr progress ???

FWIW I think that the last evolution (or dinosaur) of the randonneuse  produced on the acount of the Confrérie of the 650B, the Aubrac (no longer made since the beginning of the year due to a lack of modern bits that fit the concept) still has this form of mudguard fitting. I will see if I can find a photo showing it. The rubber washers are meant to sandwich the guard, damping out the vibration and any noisesome rattles.

Ben T

Re: Gilles berthoud metal guards
« Reply #7 on: 28 March, 2021, 10:06:50 pm »
Just one bolt with a modified penny washer. Now you know why folk moan about fitting metal mudguards. There usually is a lot of fiddling needed to get them to fit perfectly. Plastic guards are less hassle/ more forgiving but not as pretty.

I find them all fiddly, plastic or metal  :)

TimC

  • Old blerk sometimes onabike.
Re: Gilles berthoud metal guards
« Reply #8 on: 30 March, 2021, 03:35:58 am »
I have GB mudguards on my Holdsworth, and the rear mount to the brake bridge is similar to your front mount, with a double bolted L-bracket fitting to the mudguard. That's how it was supplied. I'll see if I can add photos tomorrow.

Re: Gilles berthoud metal guards
« Reply #9 on: 30 March, 2021, 12:40:25 pm »
Richard Hallett did warn me that galvanic corrosion is likely where aluminium is bolted to the steel.  He treats where the stays bolt to eliminate this (not sure with what, but I could ask).  I'm guessing the crack was started by corrosion.

Ben T

Re: Gilles berthoud metal guards
« Reply #10 on: 30 March, 2021, 01:09:09 pm »
Richard Hallett did warn me that galvanic corrosion is likely where aluminium is bolted to the steel.  He treats where the stays bolt to eliminate this (not sure with what, but I could ask).  I'm guessing the crack was started by corrosion.

Yeah - that would make sense cos it does seem to have started by corrosion...but this isn't anywhere near a stay, so not sure which bit is aluminium - the guard is SS, the L bracket is SS and the bolt should be.

I will double check the L-bracket and the bolt are steel when I put it back together though, and keep an eye on the stay joints....in terms of treating it I guess you could do worse than with a smear of vaseline

Ben T

Re: Gilles berthoud metal guards
« Reply #11 on: 30 March, 2021, 01:14:06 pm »
Richard Hallett did warn me that galvanic corrosion is likely where aluminium is bolted to the steel.  He treats where the stays bolt to eliminate this (not sure with what, but I could ask).  I'm guessing the crack was started by corrosion.

Yeah - that would make sense cos it does seem to have started by corrosion...but this isn't anywhere near a stay, so not sure which bit is aluminium - the guard is SS, the L bracket is SS and the bolt should be.

I will double check the L-bracket and the bolt are steel when I put it back together though, and keep an eye on the stay joints....in terms of treating it I guess you could do worse than with a smear of vaseline

Oh... I have just found where I ordered the steel for the L-bracket from - https://www.amazon.co.uk/gp/product/B00L24VLXI/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

just noticed it doesn't actually say stainless steel, it could be that it's mild steel and thus prone to corrosion

LittleWheelsandBig

  • Whimsy Rider
Re: Gilles berthoud metal guards
« Reply #12 on: 30 March, 2021, 01:19:15 pm »
Aluminium corrodes preferentially to steel (galvanic table) and so protects the steel when galvanic corrosion occurs. Aluminium isn’t the issue here.
Wheel meet again, don't know where, don't know when...

Ben T

Re: Gilles berthoud metal guards
« Reply #13 on: 30 March, 2021, 01:24:03 pm »
Aluminium corrodes preferentially to steel (galvanic table) and so protects the steel when galvanic corrosion occurs. Aluminium isn’t the issue here.

What about if I'd used a mild, i.e. non-stainless, steel L-bracket. Would that cause the guard to be more likely to corrode than using a stainless steel bracket?
The guard appears to have corroded more than the bracket, even though the bracket has corroded some - but then again the guard is thinner, the bracket is 2mm thick.

LittleWheelsandBig

  • Whimsy Rider
Re: Gilles berthoud metal guards
« Reply #14 on: 30 March, 2021, 01:27:35 pm »
https://www.jlconline.com/how-to/exteriors/separating-galvanic-metals_o

The more noble/ cathodic metal is protected from corrosion by the anodic metal. SS is cathodic in most common environments.

Don’t confuse rust-staining from another metal with ‘proper’ corrosion.
Wheel meet again, don't know where, don't know when...

Ben T

Re: Gilles berthoud metal guards
« Reply #15 on: 30 March, 2021, 01:35:22 pm »
https://www.jlconline.com/how-to/exteriors/separating-galvanic-metals_o

The more noble/ cathodic metal is protected from corrosion by the anodic metal. SS is cathodic in most common environments.

Hmm. I get what you're saying from a scientific perspective..... that would suggest that a mild steel L-bracket would essentially "sacrifice itself" to prevent the guard corroding.
It appears it hasn't sacrificed itself quite enough to prevent the guard corroding though.

It looks a bit like corrosion may have started on the bracket but then "spread" to the guard but maybe that's not a scientifically valid observation.

Unless the bits of corrosion that appear to be on the guard have actually just rubbed off the bracket, and the crack is actually not purely due to corrosion of the actual guard.


Ben T

Re: Gilles berthoud metal guards
« Reply #16 on: 30 March, 2021, 01:37:00 pm »
https://www.jlconline.com/how-to/exteriors/separating-galvanic-metals_o

The more noble/ cathodic metal is protected from corrosion by the anodic metal. SS is cathodic in most common environments.

Don’t confuse rust-staining from another metal with ‘proper’ corrosion.
yes I think rust staining is what it must be.

Re: Gilles berthoud metal guards
« Reply #17 on: 30 March, 2021, 01:38:44 pm »
Why not try PDW? mudguards they are anodized and have plastic stickers to protect the rub areas. 2 winters and can't see any corrosion.

Ben T

Re: Gilles berthoud metal guards
« Reply #18 on: 30 March, 2021, 01:41:00 pm »
Why not try PDW? mudguards they are anodized and have plastic stickers to protect the rub areas. 2 winters and can't see any corrosion.

I did try PDW once but I couldn't stop them rattling horrendously.

If the GB cracks again even with a double-bolted bracket then I might try again - after all fitting skills are increasing all the time  :thumbsup:


Re: Gilles berthoud metal guards
« Reply #19 on: 30 March, 2021, 07:13:34 pm »
Why not try PDW? mudguards they are anodized and have plastic stickers to protect the rub areas. 2 winters and can't see any corrosion.

I did have one crack in half.