As a body of experienced riders, have any of you come across any incidents where a stone or foreign body has become lodged under the forks of a low-clearance racebike?
Or where an object has caused an accident by being flipped up by a tyre and stopping the wheel? Is this sort of thing an occasional occurance, or too freakish to worry about?
This relates to a new road mudguard we are developing.
There was someone one here (old forum pre 'incident') who fitted some SKS guards and didn't use the safety dohdahs on the front, so the guard was properly fixed to the crown & bottom of fork. The guard caught and concertinered (sp?) between the crown & tyre resulting in supermanning over the bars and breaking his forks.
Ouch!
/Waves!
I'd err more on the freakish rather than occassional occurance. As to whether it's worth worrying about, only if you want to 
This used to come up quite a lot on the CTC website IIRC. Old boys + old bkes + old style mudguards without a safety release jobby on the stays for front mudguard. I think there was a death.
I did have an incident years ago where a cr@ppy mudguard broke free of the fork crown bracket and rotated with the wheel before jamming the front wheel under the crown and sending me over the bars, still got the scars 20 years later!
It's worth worrying about if you manufacture mudguards!
I have a new design, and don't want to be responsible for anyone's faceplant.
I have built a safety feature into the 'guards, but I worry about situations like in your pics above. Would you hold the manufacturer responsible in the above scenario? Should he have made breakaway stays? And what if the stays entered the wheel after breaking away, and caused the accident anyway?
I know you don't want to copy SKS, but the way their break away is designed I don't think the stays would get stuck in the spokes after breaking away from the lower mount. Something stuck between tyre and guard would force the guard away from the tyre and so the stays would be going away from the fork, which is where they'd need to get stuck to send you over the bars.
I think you need to look into the relevant standards and laws, but I'd imagine if you've taken all reasonable care to ensure that the guard doesn't cause an accident, you would be OK. If you ignored the fact that breakaway stays have been developed by other manufacturers to address a specific potentially dangerous problem, you'd be fooked if someone got injured by it.
I've never heard of an instance where the wheel has been stopped just by something lodged between the tyre and fork with no mudguard crumpling. I would imagine that the tyre would deform sufficiently to allow it to pass through without throwing off the rider.
I'm amazed you actually need stays. Infact I'd put money on the Crud one not having them.
Also a radical new profile that does things involving surface tension to deflect spray rather than just a big gutter?
Many years ago I had an old bike with metal mud guards. Going down a long hill the guard somehow rotated round to get between the wheel and the road. The front brake wasn't much cop on this bike (may well have been a rod pull brake) so I ended up flying down the hill with the back end of the bike sweeping wildly from side to side until the road flattened out.
What you need is a design that doesn't go between the crown and wheel.
If I could figure out how to, I'd put a pic on the site for a singletrac exclusive. Brant's ideas above were all considered, but we have come up with a unique design for a full mudguard set that fits any racebike with more than 4mm clearance under the brake area. Stays yes, but no coathangers involved. weighs 200grams the pair, no metal parts. I just don't want to be responsible for any nasty accidents, so any anecdotal incidents will help us understand the dilemma.
BTW, it DOES go between crown and tyre, to give full protection. And this is where potential problems may occure. If I sell 100,000 sets, and each rider only does 1,000 miles, then there will be problems. I still don't know wether to go ahead with this project.
how about a two pice setup? that way anythign that would normaly clear the fork, will clear the fork?
I'm more worried about sticks in my spokes and rocks getting jammed in the chainstays on mountainbike rides.
And this is where potential problems may occure. If I sell 100,000 sets, and each rider only does 1,000 miles, then there will be problems. I still don't know wether to go ahead with this project.
Are you a limited company yet 
Would you hold the manufacturer responsible in the above scenario?
I'd be taking legal advice rather than asking on a forum!
There are no legal requirements for aftermarket mudguard manufacturers. You just have to research and make value judgments.
Being LTD is no longer a protection against prosecution or financial claims. I am not LTD, as I could not face the extra paperwork.
My boss had a nasty accident a few years back by something jamming between his mudguard and tyre.
I run sks guards on my pompino without the safety stays on the front (as I'm using them on the rear to aid wheel removal) and have them set very close to the tyre. No incidents yet but I guess I should really get hold of some of a couple more safety stay thingies.
I just had a look in CEN 14766
It states
4.10.2 Wheel/tyre assembly – clearance
Alignment of the wheel/tyre assembly in a bicycle shall allow not less than 6 mm clearance between the tyre and any frame or fork element or a mudguard and its attachment bolts."
And also:-
4.12 Mudguards
4.12.1 Requirement
When tested by the method described in the two-stage tests in 4.12.2 and 4.12.3, the mudguard shall not prevent rotation of the wheel nor shall obstruct the steering.
4.12.2 Stage 1: Test method – tangential obstruction
Insert a 12 mm diameter steel rod between the spokes, in contact with the rim and below the mudguard stays as shown in Figure 40, and rotate the wheel to apply a tangentially-upward force of 160 N, against the mudguard stays and maintain this force for 1 min.
Remove the rod and determine whether or not the wheel is free to rotate and whether or not any damage to the mudguard adversely affects the steering.
4.12.3 Stage 2: Test method – radial force
Press the mudguard 20 mm from its free end with a 20-mm diameter, flat-ended tool radially towards the tyre with a force of 80 N as shown in Figure 41.
Figure 41 — Mudguard – radial force test
Whilst the force is maintained, rotate the wheel manually in the direction of forward movement of the bicycle and determine whether or not the wheel is free to rotate, and whether or not any damage to the mudguard adversely affects the steering.
But you probably knew this
flint catcher to remove stones before they get caught in mudguard?
simon you got a photo of that? i can;t work out how to set up the rear guards on my pomp.
I run full length sks gaurds on the commuter and had a problem with one once...
I was riding along towards a junction and as i slowed and turned my foot caught the mudgaurd (and i only have a teeny amount of toe overlap on this bike). The mud gaurd edge then caught in a tread on the tyre and proceeded to concertina up into the fork (just like ian munro's pic), thankfully i was going slow so it just stopped me without incident. One thing i was concerned about was the 'release clips' only popped out once it folded right up, so not stopping the accident.
I put it down to my gaurds being too far from the tyre (id set them with room to run cross tyres so i didnt have to fiddle if i wanted to go offroad) so there was space for it to fold up and not force the stay out of the palstic clip. I now run the gaurd nice and close to the tyre so that if it did fold it would deffinatley pop the saftey clips, it does mean i occasionally hear grit etc. hitting the gaurd but its a lot safer now.
And to answer the original post, ive run road bikes with some VERY tight clearances and although you can get grit scraping the underside of the crown youd have to be VERY VERY unlucky for the tyre to pick up a piece big enough to actually stop your tyre, especially at speed.
Rich.
Brant, doesn't that all apply just to OEM?
I have been advised there are no requirements on aftermarket mudguards, as the onus is on the fitter.
Rich above, you are asking for trouble offroading with full mudguards!
If I could figure out how to, I'd put a pic on the site for a singletrac exclusive
What is there to figure out? Publicly hosted pic, use the IMG buttons above the "post" box to enter the location of the pic (usually ends in .jpg)
Would be very interested to see this as never considered mudguards could fit on my roadbike.
Brant, doesn't that all apply just to OEM?
I have been advised there are no requirements on aftermarket mudguards, as the onus is on the fitter.
You can take that opinion, and I'm sure you're correct.
There are industry people taking similar views about steel frames at the moment.
CEN 14766 isn't law in the UK.
HOWEVER - it is the most stringent test standard around, and if you want to carry on getting sleep at night and if ever gets to court, you can stand up and say "well, my XXX exceeds the best standard around by a factor of Y".
Next week I will teach your granny how to suck eggs
Let me email some pics over to you Brant...I havent got yr email, but do you have mine?
I run sks guards on my pompino without the safety stays on the front (as I'm using them on the rear to aid wheel removal) and have them set very close to the tyre. No incidents yet but I guess I should really get hold of some of a couple more safety stay thingies.
Yep, that's why I had no safeties on the front too.
I have now
I've done the mudguard onto close clearance frames thing for a number of years now, using the old Bluemels plastic guards, and fixing them with zipties at the fork end and under the crown. As noted, you need to set them so the guard is very close to the tyre, and put up with a bit of grit rubbing when it's wet.
One thing I would suggest is that you test the guard in temps at or below freezing; one ride was spoiled when I clipped the front mudguard with my foot and in temps of about -1, it snapped off half way up. There also seems to be a set length for guards; too short! This leads to wet feet, so a longer guard would be nice.
For frame fixing, I'd also take into account the idea that you may see people using them on carbon frames, so some proper frame protection to avoid rub marks is important in either the instructions or the package.
Keep them narrow too; 23c tyres don't need a huge gutter style thing.
Can't you just spend some time making a working QR for the raceguard? Mines in the bin after one use as the metal bolt just turns in the plastic housing (funny how that would happen... :p ). I've not found one decent QR mud guard (Topeak Defender too difficult to get tight enough to stop it moving, Cycraguard I'm currently using isn't exactly QR in that you need to take the post out). I can't believe it would take much to do a decent aluminium QR (hinged clamp or something), if it worked I'm sure people would pay a premium over the cheap plastic affairs out there.
As for road bike mudguard incidents, not had one myself using SKS raceblades . Happy enough with the design of the front raceblade TBH but if someone could do a decent full length rear that was stable without needing eyelets I'd be interested.
As Brant says, it's not law but it is best practice. Due diligence by following best practice should mitigate any legal problems under H&S legislation where you usually have to prove you are innocent.
Have a look at some road bike mudguards made by Giant for their Defy road bikes. They are very close clearance, and have a cutaway around the crown and rear brake as there isn't enough clearance for the guard to fit.
They fit really well on my road bike, and I've not had any issues with debris being caught (but I haven't had any issues like that without mudguards either)
I don't think H&S law is relevant - it's product liability he needs to look at.
One thing i was concerned about was the 'release clips' only popped out once it folded right up, so not stopping the accident.
How do you know they wouldn't have stopped you going over the bars?
simon you got a photo of that? i can;t work out how to set up the rear guards on my pomp.
Just found this...
Not a great pic. If I can be bothered I'll take a better one for you.
Yep, that's why I had no safeties on the front too.
I know, and I'm sure I said I'd fit some after your little incident
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