Fitting SKS Bluemels mudguards to Thorn Sherpa

[Fourpanniers]

I seem to have got this completely wrong but am I right in thinking that it is impossible to fit SKS Bluemels mudguards in a straightforward way to a Thorn (Sherpa or otherwise)? The supporting "bridge" on the front mudguard doesn't lie flat and the struts don't angle onto the Thorn half-way fork mount. What's the plan here?

[mickeg]

I was unhappy with the mudguards I fitted to my Nomad over a decade ago, a few months ago fitted the Blumel mudguards (I am in USA, so I call them fenders).

The fender mount on Thorns at the fork crown is facing towards the tire, not the hole through the fork crown that is oriented fore and aft.

Photos attached.

I think I had a metal bracket on the front that is riveted to the fender, many fenders come with a bracket that is intended to fit to a hole through the fork crown.  I removed it by drilling out the rivets.  The rivets get hot from drilling, hot rivets can melt plastic, do it slow so you don't melt anything.  If I recall correctly, there were two rivet holes, one I covered with black electrical tape, used the other to attach the fender to the fork crown.  I put a spacer between the fender and fork crown so that the fender does not rub on the crown and does not get deformed to the shape of the crown.  Instead the fender only touches that spacer. Use as thin a spacer as practical to get the greatest fender clearance between the tire tread and fender.  Or, if you only use narrow tires, perhaps you might want less clearance, in which case a longer spacer may be appropriate.  If you do not have anything to make a spacer, several washers stacked can serve that purpose.  I think there are two threaded holes facing the tire, I only used one.

Metal stays, I bent them just in front of the brackets on the fender to the correct angle.  I cut the lower front stays to a shorter length so my feet do not hit them.  I do not think I cut the upper, but I might have.

I did not use the plastic covers over the ends of the stays that came with the kit, instead I used some other caps that are red.

I assume my fenders look like yours, but I bought mine several years ago and finally installed them this year.  Thus my parts might be slightly different from yours.  The fenders I installed are 65mm wide, that model (26 inch wheel, 65mm wide fender) is no longer made.

I put the fenders on my Sherpa a decade and a half ago, I think it is the same as I described above, but I have not ridden my Sherpa for eight years, it is in storage and would not be convenient for me to look at it at this time.

Thorn often fits the fender stays to racks, not the fork and rear dropout.  But I always fit my fenders to the fork stays and dropouts because I might switch to different racks or remove them altogether.  Do whichever you prefer.

When I cut the stays, I used a hack saw, and filed the end to get rid of any sharp edges.

[Fourpanniers]

Thanks very much for that. I've spoken to Thorn who confirmed that you have to drill out the rivets and bend the stays. I didn't expect this work and I'm not really competent enough to do it (Thorn recommend that it is done by a bike mechanic). My only complaint with Thorn is that they don't indicate this on their webpage - their own mechanic was actually very helpful in describing what had to be done.

[Andyb1]

When I owned the bike before you it came with a set of tatty and cracked Bluemels, but they were quite narrow and were sized for the 35mm tyres it then had.
As Mickeg has said, you have to mount the front mudguard with an M5 bolt vertically upwards into the bridge of the fork with a spacer to get the correct tyre clearance.  A short piece of 6mm fuel line will do the job.  There was a dished penny washer inside the mudguard to spread the load, and personally I would make the hole through the mudguard with a soldering iron rather than drill it and risk cracks.
The same system was used to mount the rear mudguard to each bridge.
I think I fitted plastic screws to close the M5 holes as I did not use mudguards.
Hope this helps!



 

[mickeg]

I think I used some larger diameter washers, but not as big as a coin on each side of the fender to spread the pressure on the plastic fender over the area better.  I typically do that.

I used a drill bit just a hair larger than the rivet diameter, that way I only had to drill off the top of the part of the rivet that had been deformed.  That way, that piece of deformed rivet basically became a tiny little donut ring stuck on my drill bit and I could drive the rivet out from the plastic.  I do not think I had to enlarge the rivet hole for the M5 bolt, but I might have.

This is bringing back memory of how I installed them this past spring.  I think the hardest part was drilling the hole for the seatstay bridge in the right place.  Installed the lower screw on the back that goes into the chainstay bridge and  put some masking tape on the fender, rubbed the tape on that fender on the seatstay bridge forcefully, then I could see where the tape had an impression from that so I knew where to drill.  And I think I got it just right which sometimes does not occur.

I made the mudflaps that I attached to the fender out of plastic from coffee can lids.  Used some short M4 screws to hold those in place.  But I suspect that adding mudflaps is something you are not interested in.

If you are not used to using tools, a bike mechanic may be the best option.  But I have often seen fenders where the bike mechanic cut off stays too short, no excess stay sticks out in case you want to mount larger tires later, so that is a possible hazard.  I always leave a bit of excess stay sticking out as you can see from my photos with the red covers on the tips.

I put my Sherpa fenders on with 50mm tires, but often use 40mm tires.  But I leave the fenders adjusted for 50mm, so there is a sizeable gap between fender and tire.  See photo of my Sherpa.  Oh, just remembered, the Sherpa has fenders from a different brand, these are not SKS fenders.  I have 40mm tires on the Sherpa at the time of photo.

[PH]

I'm going to suggest you do it yourself and not trust it to a mechanic.  it's a job that pays dividends if you take the time and the one thing a shop mechanic isn't going to do us spend very long on it, that's not because they're not capable, but they know no one is going to accept being billed three hours workshop time to fit guards!
The way Thorn fit guards is not a lot different now to what it was when I bought a Raven in 2004.  If you go to the current nomad 650B  pdf's on the Thorn website, there's some clear photos you can zoom in on.  Maybe on other brochures as well, I haven't looked.
There's the option on the rear guard to fit to rack or dropout, if you choose the dropout there's no bending of stays required, both of mine are attached at the dropout.  You've probably already got this from Thorn, but anyway... The major differences between the way Thorn do it and the Bluemels instructions are:
Direct fitting so you have to drill out the original front bracket and not use the one at the rear.  A bit of tape or sticker will cover any unused holes.
Use spacers to drop the mudguard both front and back, any bit of tube will do, or start with some oversized nuts and washers till you've got the position right.
Thorn don't pass the stay through the mudguard fitting. the angle is wrong, so the spoke needs to by cut precisely where it exits the bolt.   This is a really tidy way of doing it, it leaves nothing protruding to catch and it doesn't need the rubber protection caps that often fail. BUT - it's a one shot cut, you are not leaving any adjustment if you want to extend the guard at a later date, either for more clearance or bigger tyres.  (Replacement stays are available, but they're half the price of new guards)

I put a whole afternoon aside to fit guards.  The way to achieve longevity is for no part to be under stress.  Once I'm happy with the fitting, I'll remove each  screw, one at a time, and the guard should stay in position.  If the guard moves with one screw out, give the stays a gentle squeeze in that direction.  Then add a bit of Loctite when you put the screw back. 
it is a bit of a faff, and yes I could do it in a quarter of the time, but I do it this way and barring accidents, that's it for life (Or as long as I've ever kept a bike anyway)
I also add rubber washers between all the frame attachment points, I'm not sure it's necessary, but it doesn't do any harm and avoids the possibility of scratching paint.
Take your time and it'll be fine, let us know how you get on.

There was a dished penny washer inside the mudguard to spread the load, and personally I would make the hole through the mudguard with a soldering iron rather than drill it and risk cracks.

Good point, I also like to melt the hole rather than drill it, I don't have a soldering iron, so heat up a long bolt.  If not re-using the rivet hole, it's important to get the new one central, or the guard will be forever at a squint.


TO ADD  - The theory of fitting the guards half way up the forks is that they don't then need the safety clips.  If you get something caught under the front guard, as it rotates around that axis the gap opens up.  This isn't the case fitting to the dropout, where the release clips are very much required.

[Fourpanniers]

Well thank you very much everyone - I find all the comments heartening as (a) I'm going away tomorrow and (b) I knew mudguards are fiddly but this problem (with Thorn bikes) was new to me so a bit stressful to say the least. I've fiddled with loads of mudguards over the years but this is the first time that it has been out of my mechanical reach to fit one on! However I'm going to give it a go when I get back, hopefully in calmer mood. I had one more question: why cannot the mudguard be fixed to the (headlight?) eyelet at the front. I know that the bracket is too tall but if this were cut down to allow the mudguard to be raised high, would that not work?

[mickeg]

Earlier this year, for the first time ever while riding I got a stick in the front spokes.  My front fender is a very old (~20 years?) Zefal fender that I am not sure what it is made of.  Looks like plastic, but very stiff, might be fiberglass?  This was on my rando (UK translation - audaxing) bike.

Each stay is connected to the fender in a way that the bracket on the end of the stay will break loose from the fender.  Stick bent the lower stay on the right side with a pretty significant bend in the stay.  Three of the four stays released from the fender, two on the left side and the bent stay on the right.  I think I instantaneously lost two or three km per hour speed and there was a fairly loud noise as the fender hit the tire.  I was at an intersection with heavy traffic, fortunately I stayed upright and rolling, got off the road maybe 50 meters later.

If I did not have a safety breakaway feature on those fenders, I am sure I would have gone over the handlebars and crashed and maybe hit by a car.

First photo I added text and arrows, there are small brackets on the end of each stay and you can see a small cut out on the fender where those stays were before they broke loose.

Second photo, no text, same as first photo.

If you are wondering about the dark color of the grass, it was late March, that would have been covered with snow a few weeks earlier. 

It is a poor photo, I was not thinking about lighting and background conditions, I just wanted to fix it and get on my way again, it probably was only 5 degrees above (C).

My Sherpa lacks those break away things on the front fender.  I have already bought some to add to the Sherpa next time I take it out of storage.

[mickeg]

Fitting the front fender bracket to the fork crown where the light bolt would go through the fork?

On most bikes that hole goes all the way through.  On my Sherpa, it does not go through the back of the fork crown.

It does on my rando bike, first photo, you can see I have a nylock nut there.  But on this bike, I could mount the fender the way I did on my Thorns, under the fork crown.  So, I did.  Thus, you do not see a fender bracket there.

My light touring bike, second photo, I attached the fender behind the fork crown.  In this case instead of a long bolt, I used a piece of threaded rod and nuts to hold that threaded rod tightly to the fork.  And used one of those odd nuts that uses an allen wrench to hold the fork in place.  The nut was from a brake pad.  I did it this way so I could disconnect the fender without loosing the threaded rod in the fork on a tour where I would not have a big choice of tools to work with.  Or I could adjust the light bracket without messing with the fender this way too.

[Andyb1]

Always worth having some sort of front mudguard breakaway when the front mudguard stays bolt to the fork near the axle, but as Paul has said, when the stays bolt higher up the fork they should not cause the front wheel to lock if they rotate upwards (eg due to a stick under the mudguard) as the mudguard should move away from the tyre.

Saying that, I bought some SKS breakaway mounts from SJS and fitted them to the front mudguard stays on the bike that I use on local roads where a muddy stick might well get picked up.

[PH]

Well thank you very much everyone - I find all the comments heartening as (a) I'm going away tomorrow and (b) I knew mudguards are fiddly but this problem (with Thorn bikes) was new to me so a bit stressful to say the least. I've fiddled with loads of mudguards over the years but this is the first time that it has been out of my mechanical reach to fit one on! However I'm going to give it a go when I get back, hopefully in calmer mood. I had one more question: why cannot the mudguard be fixed to the (headlight?) eyelet at the front. I know that the bracket is too tall but if this were cut down to allow the mudguard to be raised high, would that not work?

I don't see it as a problem, it's a little added complexity, for a better result.  The advantage of SKS/Bluemels is that out of the box they're designed for universal fitting.  That doesn't make it the best option, the brackets fatigue and fail, they're prone to rattle, the extending stays can catch... Direct fitting does take longer, but the result is better fitted guards (Thorn are not the only frame builders to incorporate this)
I expect when Thorn build a bike, they don't have any of the faff, they'll have it set up so guards can be pre assembled.  It's the same when you fit Brompton guards, they only fit the one bike so it takes five minutes, 
Fitting the front bracket to the threaded hole on the front of the fork would work, but it isn't as good, there's a twisting force that isn't present with underside mounting, that's exaggerated if you have to drop the guard further than the bracket permits.

[Fourpanniers]

A little update on this but thanks again for the comments. I'm back now from my trip - the weather was kinder than I deserved and my waterproof tent bag took the spray on the back rack. However I did pop into a bike shop en route (really helpful - 99Bikes Totton). They suggested using spacers to extend the bolt in the headlight eyelet so that the bracket doesn't snag on the fork bearing. I thought this was a good temporary solution and by using the fork drop-out eyelets, job done (at least on the front). I was presuming te eyelet is deep enough to hold the mudguard strongly enough as the bolt doesn't go through the crown.

However:    
Fitting the front bracket to the threaded hole on the front of the fork would work, but it isn't as good, there's a twisting force that isn't present with underside mounting, that's exaggerated if you have to drop the guard further than the bracket permits.

I think I'm going to give the proper installation a go now I have time and I know what I'm up against.

[mickeg]

When you put the rear on, bolts go through the fender at both the chainstay bridge and seatstay bridge.  I mentioned in a previous post how I used tape to figure out where to drill the second hole.  A few extra minutes to be careful that the hole is in the correct place is well rewarded.

I had a bigger gap between my tire and chainstay bridge than between the tire and seatstay bridge.  I used a plastic spacer between the fender and the chainstay bridge on mine to make the gap between the tire and the fender more uniform for aesthetics.   First photo shows that spacer, just barely.  Spacer is plastic, I used some yellow nail polish to paint it to match the frame color.  Second photo shows a nice even gap between the fender and tire all the way around, it also shows that I am not sufficiently careful to avoid having my shadow within the photo.

In other words, I was happy to spend some extra time to make it look good.

[in4]

Really interesting to read and of course great photos of your Nomad.
I noticed you used two quick links in your chain. Was that an 'on tour' solution to a problem?

[mickeg]

Really interesting to read and of course great photos of your Nomad.
I noticed you used two quick links in your chain. Was that an 'on tour' solution to a problem?

For riding near home I use a 44T chain ring.  Then my bike is never heavily loaded so I do not need really low gears, and for some shallow downhills I have some higher gears.

Touring, or mountain biking, I use a 36T chainring because then I really need those low gears.

Thus easily adding or subtracting 4 links can come in handy.  That said, I use this bike less often these days, my last two tours were on my titanium touring bike, have not done any mountain biking on the Nomad for a decade.  Thinking back, I have now had the 44T chainring on continuously for about six years.  My last tour on it was in 2019 before Covid.

I took those photos in May this year, I have not liked the fenders I had on that bike, bought some SKS fenders for it a few years ago and finally this past spring put the new fenders on it.  But I am guessing that I have put less than 500 miles on the Nomad this year.  Most of my distance has been either on my rando bike or my light touring bike.  But most rides have been on my "errand" bike, which is a mid 90s rather rusty mountain bike that I use for short trips, like later today when I ride that to the gym, about 2.2km one way.