What's the safety rule for metal fender size/clearance?

[lungimsam]

1. How much clearance above tread, all around tire?

2. How much clearance from sides of tire (where the rolled edges envelope sides of tire)?

3. Should I just get the widest fender that will fit on the bike? I am hoping to settle on 32-42mm Compass/GB tires for my Bleriot. I have Hetres on it now, but no fenders yet.

I will have to re-check the latest BQ issue for the fender safety article. I think it said minimum 1.7cm vertical clearance all around tread?

[Goshen Peter]

why are you getting rid of the hetres?

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[lungimsam]

I'm keeping the Hetres.

But I want to try Cypress 32's just to see how they feel in comparison (there is another thread of mine from a month or so ago about ponderings on that, but now I'm talking fenders, not tires.).

If they feel just as good to me, then I might use them since I think they will give me more clearance under the fenders.

On my Sam with P45's and Hetres, it is pretty tight (width-wise), and under the brake bridge and fork crown, even with fenders at max height. No problem though. No rubbing or anything. They roll free and the P45's have worked out nicely with Hetres on my Sam bike. So I'm not complaining. But I'd like a little more clearance between tires and inside of fender under the brake bridge and fork crown.

I don't know how it would be with the Bleriot as I haven't bought fenders for it yet.

[lungimsam]

And by the way...How come Honjo Hammered fenders for 650b prices swing wildly from 80-something$/pair to almost 200$/pair?

Are there different levels of quality among Honjo 650b hammered fenders? Special runs?

[Anton Tutter]

On Tuesday, October 14, 2014 12:23:37 AM UTC-4, lungimsam wrote:

And by the way...How come Honjo Hammered fenders for 650b prices swing wildly from 80-something$/pair to almost 200$/pair?

Are there different levels of quality among Honjo 650b hammered fenders? Special runs?

Be careful when shopping for Honjos.  Some prices won't include the stays or hardware, just the bare fenders. Other prices will include everything needed for a typical installation. For example, Jitensha studios sells Honjo parts a la carte.  The fenders are ~$80 and by the time you add the stays, drawbolts, daruma bolt, sliding bracket, etc, you're up at $140-160.  Then there's also the fluctuating value of the Yen, and newer stock may be priced cheaper than older stock, etc...  Lastly, it could also be a matter of special runs.  I ordered Honjos a la carte from Jitensha, and was pleasantly surprised to find the leading and trailing ends of the fenders to be nicely scalloped like in the old French style. There had been no photos to indicate this. Bonus! 

[Ron Mc]

here's the best safety option for Honjo fenders - tire wipers - Compass sells them.  

You can see them at the bottom of my fenders.  They keep Everything except dust and water out of the fenders - they even scrape mud (within reason).  No sticks, no rocks, no chert - they reject it all.  As far as clearance goes, if you can see air, it's too much, and the fenders won't be able to do their job.  

[Ron Mc]

Anton, I bought my Honjos from Jitensa and even racking up stays and fasteners, the bill was not excessive.  If you totally want to cut the cost, you can go with Tanaka fenders (who I'm guessing makes VO fenders).  

[Brian Campbell]

Are your tire scrapers installed backwards? Can't they be forced under the fender? 

[Ron Mc]

este - Jan Heine's photo

I've deflected sticks, rocks, piles of leaves and twigs, scraped mud - they work great..  Was riding with some friends after a good summer  monsoon ran-off mud all over a paved city greenway that follows a creek bottom across town.  Everyone we saw through the morning said, "oh, your bike is not going to stay that clean for long".  The fact is, all the fenderless muddy people were just getting started, and we had already ridden 18 miles. We did have to stop frequently for my buddy to knock mud out of his fenders, but I had no mud in my fenders - the tire wipers kept it out.  

Obviously, they only work with slick tires.    

[Ron Mc]

should have included this link - http://www.compasscycle.com/tires_wipers_700.html

[Michael Hechmer]

The rule of thumb for metal fenders is tire size plus 18 mm as a minimum.  This allows 4 mm for each rolled edge and 10 mm of clearance.  If you can go somewhat bigger than that, you should.  The added space gives you the option of bigger tires in the future and reduces the chance of something jamming between the tire & fender.  32-42 is  pretty wide range,so I would suggest 60 mm fenders if they will fit.  Honjos are elegant.  VO fenders are also nice.  Bertoud fenders are the sturdiest.  Properly installed they should last a long time, so a few dollars more or less is probably not the best criterium.  

Michael

[Jeffrey Marco]

My rule is if they don't rub, they fit.

On Monday, October 13, 2014 11:46:09 PM UTC-4, lungimsam wrote:

[Brian Campbell]

I think that is the rear tire, shot from the non-drive side of the bike. You can see the chain in the backround.

[Eric Norris]

I’ve read Jan’s article and various emails and comments about fender clearance, but I haven’t seen anyone address the possibility that tight fender clearances improve safety by helping to *exclude* objects from being caught between the fender and tire. If I have 1cm of clearance (about a half and inch), then objects (twigs, branches, etc.) that are that size can easily slip between the wheel and fender. Wouldn’t a tighter clearance—say, 1/4 inch—keep a half-inch-size twig/branch out? Personally, I would much rather deal with a 1/4-inch twig than one that is twice the size and much harder to break and therefore much more likely to cause a fender catastrophe.

As Jan mentions in his BQ article, most of the classic randonneur machines had very tight fender clearances. Perhaps this is one reason?

Am I off base here?

—Eric N

[Ron Mc]

Brian, if you search tire savers images, you can see examples of them mounted in both rotation directions.  They work great this way, they eject Everything except dust and water from the fenders, and there is no physical way they could turn under the fender.  

Regards

[John Phillips]

What is the fattest slick these wipers will fit?

Thanks,

John

[Anton Tutter]

Yes, that is on the front of the fender (the trailing edge). That would be preferred to the leading edge (the rear), but the way the tire savers are designed, if on the leading edge and something snags them, the rubber tubes holding the scraper will just give and no jamming into the fender will occur.

[Michael Hechmer]

I think Eric's points are very well worth considering.  The tighter tolerances leave little room for error.  If you load your bike in the back of the car, there is a good chance that the fender will be knocked out of your perfect line.  If you are prepared to live with that tight tolerance then maybe tighter is better.  I will admit that my only experience with sudden failure is having an acorn penetrate my wife's rear fender, which was open to accommodate horizontal drop outs.

michael

[Brian Campbell]

Thanks for the education. I had not seen them installed that way before. Now, are you SURE they are installed correctly :-)?

[Ron Mc]

all I know is they work

[Jan Heine]

Most of the classic French randonneur machines had very generous fender clearances, and that, together with the wide, and thus stiff, fenders, seems to be the reason why there are no reports of fender accidents.

Generally, more clearance is better. At some point, it doesn't look nice, and you get toe overlap problems, though... The idea is that small debris can be accelerated so much that it will collapse a fender - and you want it to go through the fender instead. Large stuff cannot pick up quite so much speed, and so it'll bang against the trailing edge of the fender, and then fall back onto the road.

In most fender accidents I have seen, insufficient (too tight) clearances were at least a contributing factor. Generally speaking, metal fenders seem to be safer than plastic ones. Even the quick release of plastic fenders cannot prevent all accidents... Fender accidents are rare, but if they happen, they can be nasty.

Jan Heine
Editor
Bicycle Quarterly
www.bikequarterly.com

[Anton Tutter]

Not to nitpick, but my engineering background compels me to explain that when looking at fender/wheel dynamics, the trailing edge would be, counterintuitively, the front edge of the fender, not the rear edge.  Aerodynamically, trailing edge refers to the rear of an object going through a wind flow. So it's logical that the nose of a saddle is the leading edge and the rear of the saddle is the trailing edge. But fenders are different because of their relationship to the rotating wheels.  If you look at the fender of a bicycle in motion, the fender is actually moving in the opposite direction of the wheel, RELATIVE to the wheel. Therefore, the rear edge of the fender is the one that is moving toward the oncoming tire tread, toward the "debris flow" that we worry about getting jammed up in the fender, and therefore is the leading edge ("debris flow" is analogous to wind flow in the aerodynamic definitions of leading/trailing edges-- it enters at the rear, and [hopefully] bounces around and exits the front).  So rear fender edge = leading; front fender edge = trailing.  Sorry for the nitpick!

[Jan Heine]

Agreed. I should have written "leading" or "front" edge. Especially when mounting tire wipers, they should go on the trailing (front) edge of the fender, so they don't get sucked into the fender when bigger debris hits them... I apologize for any confusion.

Jan Heine
Bicycle Quarterly
www.bikequarterly.com

[Jan Heine]

Time for one last correction. Debris hits the leading or _rear_ edge of the fender and either must go through or be slow enough that it falls back onto the road without collapsing the fender. Tire wipers are mounted on the trailing or _front_ edge of the fender.

Sorry for the continued confusion - I hope it's correct this time around!

Jan Heine
Editor
Bicycle Quarterly
www.bikequarterly.com