What could go wrong? SKS Al Edge surgery.

I have SKS AL Edge mudguards. I’ve generally been pleased with them. However, I have recently been using slightly bigger tyres, and when I put the mudguards on for winter the rear has started to make a banging noise when I drop off a kerb or hit a bumpy patch.

After much investigation I think I’ve discovered what’s happening: The mudguards have three fixing points (I hope the following makes sense) – near the bottom bracket, the bridge, and a pair of struts. The problem is that the distance between the bridge and the struts is too large, so the mudguard can hit the tyre at th top after a bump as it flexes.

My proposed solution is to saw a bit – maybe 12cm or so – of the mudguard off at the front end, drill a new hole and move the whole mudguard forward (again, I hope this make sense. If you were looking at the bike from the side with the front to the left the mudguard would move round a few degrees anti-clockwise).
This would shorten the mudguard and bring the struts closer to the bridge, hopefully providing more stability, less wobble, and stop the banging.

I don’t use this bike for group riding, only for a lonely commute, so I don’t need to worry about splashing anyone behind me, and the length would still be enough to protect my back from the wet.

So, will this work? Or will I have a less effective but equally noisy fender?

Thanks for any suggestions/advice/potential problems.

I had this problem and I just cut the struts down. As the mudguard length stays the same by bringing the guard closer to the wheel at the struts, it pushed it away from the wheel at the top.

Yes it works. 

A very real risk is the mudguard catching the strut end and rolling into itself, jamming the wheel.

Just make gap at the stay end is greater than the bridge.

It’s also worth reinforcing the bridge with zipties because that will fail at some point too.

Yes, should work as the guard will be shorter and stiffer. The closer to vertical the stay is the better in this case.

It’s also worth reinforcing the bridge with zipties because that will fail at some point too.

Reinforcing it internally so that there’s a support under the guard that extends fore+aft of the stay 20mm or more, perhaps made from an offcut of the guard and large washer, helps. Leather washers can take out a bit of the vibration between guard and the SS bridge. They tend to fail at the bridge sooner when rear guards only have one rear stay, causing the flex OP describes.

Thanks everyone so far, especially jam-bo – that’s just how I pictured it.

I’m glad you turned up jameso, the bike is an Arkose 3 so getting the go-aheaf from you is about as official as it can get. I’ve got 40c Nanos on at the moment which work perfectly without fenders but are a teeny bit too big when using them.
I did just buy a new metal clip as the included plastic one failed as you suggest. I like your idea of reinforcement there – although that will bring the guard even closer to the tyre.

Anyway, I’m off top start sawing. Thanks again.

Success!

… well, theoretically. I’ll see how it rides tomorrow. Dropping the back end isn’t making a noise anymore, and the whole thing feels more solid, no discernible wobble at all. I think I’ll have to shorten the struts by a few mm as the rear of the fender is jutting way out, far more than in jam-bo’s pic. Thanks again for the help, STW never lets me down. 

@jameso

Are you still making bikes? The Arkose is the best pounds-for-quality-and-fun bike I’ve ever owned. It’s clearly an early gravel bike as the tyre clearance would be bigger nowadays, and what we called flared bars back then seem hilariously straight now. I still love it though, and it’s my go-to bike when I’m not sure what I’ll be doing. Anyway, I’d be interested in anything with your design input. 

I don’t remember having to cut the stays down but I must have done. Mine are rock solid, to the point I just leave them on all year. 

OP are you running the 46’s?  

I’m wondering if my slightly knobbly 38’s will fit in them or if I need to go a bit wider (I think there’s a 56 as well).  I don’t want clogging.  

I did this on my wife’s bike which wasn’t built to take guards. I didn’t cut the stays down.

I’m using WTB Nanos, 700×40. I used to have Vittoria Revolutions 700×38 and they worked fine. The Nanos fit easily with no fenders, I reckon you’d have room to go up a good few sizes, maybe even the 46s you mention. 

With these mudguards I don’t think you’d get bigger tyres to work, and wider mudguards wouldn’t fit the frame. I had to alter even these guards as they wouldn’t fit by the bottom bracket – the chain stays are too close together, so I had to trim a bit off either side of the front of the fender to make it narrow enough

As I said earlier many recent gravel bikes have much bigger clearance. At first gravel bikes were like tougher road bikes, but they seem to be moving in the direction of road-ier ATBs. Or a bit like what ATBs were like in the ‘90s and early ‘00s. 

Thanks.  I’ve just ordered the wider version of the Al Edges so will see how they work out. 

The Free Ranger has plenty of clearance so I’m hoping they will go in with no/minimal modification. 🤞 

Mine are the 56’s, wouldn’t fit properly in the front arch so split it in two, and used an old SKS L bracket as there was a mount point front and rear.

Some interesting stuff here. I have the 56s on my Camino and has to do a slight bit of bending to get it to fit between the chainstays. The main issue I have is that it creaks all the time. The stays were fixed about halfway down the seatstays but I’ve since moved them down to nearer the “dropout”. I have also bought a metal bridge and the plastic one feels a bit flexy and seems to allow the guard to move a bit

garagedweller, can you update on how you find the SKS Edge 56 fits the free ranger? What size frame do you have?