I remember Brant (and Cy I think) mentioning in the past that they felt that Crud Catcher boses in the downtube was a bad idea in such a stressed area of the frame. In the recent thread on the new Shedfire frames it was again mentioned along with mention of frames that had failed due to cracks propagating from the boses. It’s not a big issue for me at present as my 853 Inbred is a fab ride but one day (money allowing) I’ll probably fancy another frame.

I rather fancy the look of the Genesis Altitude frame but, it’s got Crud Catcher boses. At 6′ tall and well over 15 stone I’m a bit of a fat biffer and reckon that any ‘highly stressed’ area of a frame is going to be much more stressed with me on it than a 10 stone whippet racer. So, are Crud Catcher boses really a disaster waiting to happen and should I discount and otherwise great looking frame on these grounds?

if it was to crack around the boss surely they’d have to honour the warranty.

check how long the warranty is.

No.
Two people disagreeing with them does not necessarily mean it’s true…

PJay I’m significantly heavier than you and have been riding a Genesis i0 (fully rigid) for nearly 2 years without any sign of cracking around the bosses. And if it did, I’d be looking at a warranty replacement (depending on lard limits of course 😉 )

Two people disagreeing with them does not necessarily mean it’s true…

To be fair PP, its not just two people is it? Its two highly respected designers of steel framed mountain bikes.

I’ll throw my hat into the ring and say that any boss / hole / stress riser on the underside of the downtube (or any other highly stressed area) is a bad idea. Yes you can thicken up the tube but that seems a little stupid just so you can use 2x M5 bolts and not zip-ties / O-rings.

I would like to point out that this sort of thing is not “opinion” but good engineering design practice…something that is lacking in some bikes.

SSP

Also the first time you crash/stack the bike flat in the car etc, you’ll snap/rip the crud catcher off its bolts if it’s rigidly fixed.

To be fair PP, its not just two people is it? Its two highly respected designers of steel framed mountain bikes.

LOL! Highly respected? By whom?

How many companies put bosses of one sort or another in the underneath of the down tube?
Not everyone no, but there’s a few out there who do it and seem to be able to produce properly designed frames at the same time… (Genesis, Diamond Back & Specialized off the top of my head)

Hey PP: Come back in a year and show me their steel CEN approved framesets – and if they have crud catcher bosses I’ll be amazed.

I used Cy’s wisdom on this to settle an argument a while back, but have since lost the email, but basically his argument was that it was fine to put bosses in provided you beefed up the tubes to maintain strength, and he wasn’t prepared to do that just to do away with zip ties.

Come back in a year and show me their steel CEN approved framesets

Sorry, what’s that mean?
🙂

LOL! Highly respected? By whom?

Other frame designers and builders, the hardest to impress.

Come back in a year and show me their steel CEN approved framesets

PP probably thinks that CEN stands for Can’t Engineer Nothin’

EDIT: Reading PP post above, I claim my £5

SSP

<Drive by abuser> Crud catcher boss yeah? Worried about cracking your frame are ya……job on son</drive by abuser>

I’ll sleep a bit better tonight….

If you can reinforce the area my producing custom tubes, like Pace used to, or you’re using a tube that’s way thicker than needed otherwise, like my seeming indestructible ColumbusOR Dave Yates, than you can probably get away with it, but you’ll end up with a frame that’s heavier than need be just to save people using rubber bands. Rubber bands are good, they do the job, and as Jon points out swing out of the way rather than cutting into your legs or cracking in a crash.

Tell you what Brant, you know how easy I break and bend frames don’t you? Let’s see how my Pitch with 3 holes in it’s downtube underside (and 2 more on top) fairs after a year, bearing in mind it only gets used on the rougher stuff and I’m off to the Lakes soon, and 5 days in the Alps in the Summer. Let’s see if I can break it….

😀
😉

Pitch has custom hyroformed tubes I presume. The downtube will have extra metal near the holes.

[thinks carefully] Hmm, I’ve never broken an alloy bike!

Steel? Tick (4 at least that I can think of, and 2 pairs of forks)
Titanium? Tick
Carbon (Parts)? Tick

And you wonder why I stick to cheap bikes now?

😀

Pitch has custom hyroformed tubes I presume. The downtube will have extra metal near the holes.

Large maufacturer in properly designed bike shocker!!!

😉

Bugger.

And you wonder why I stick to cheap bikes now?

Because your clumsy?

Lose weight?

The downtube will have extra metal near the holes.

Large maufacturer in properly designed bike shocker!!!

Large manufacturer in over-designed, over weight bike for skill-less riders non-shocker.

PP, I sugesst before you rubbish engineering principles you read up on them and then take a look at ways around the problem (which there are, as mentioned above) and then weigh up your priorities (cost, function, weight, special tube profiles etc…) when designing a frame.

SSP

Pitch has custom hyroformed tubes I presume. The downtube will have extra metal near the holes.

The Pitch has passed CEN as far as I know.

i thought hydroformed tubes started off life as standard butted tubes, in which case unless someones worked out how to do the butting in 2 dimensions rather than 1 the tubes are no thicker/thinner than they would be on a normal tube? (appart from where they’ve been stretched by hydroforming?)

Is CEN the new ‘bash it till it breaks’ (love that phrase) standard? In which case i guess the law makers had to make it passible for something like the scott scale/yeti ARC etc. So even if the pitch passed is it not more likely to fail based on the harsher riding it’ll experience?

CEN standards, unlike the old ones, has different levels for kids, road, hybrid/trekking and mountain bikes. It also requires that separate parts are tested so someone like Specialized will want to see the CEN certificate for the bars they are buying from the Tiawan Bar Company or whoever.

The old standards required that a bike would pass if tested, now the parts have to be tested before assembly.

Total nightmare to draw up and administer but its only a few years behind!

SSP

Carbon, amusingly, fares really well under the fatigue loading caused by CEN. And if it breaks, you can add another couple of wraps in the problem area, and it’s sorted.

bike for skill-less riders

Bugger off! Skill-less yourself you snobby bastard!

I’ve no idea what processes Specialized use thisisnotaspoon, and I know bugger all about hydroforming myself, but you can vary wall thickness and even put the holes in using hydroforming techniques (thank you google).

Whats the matter Molgrips? rag week? Relax….

SSP

Our cannondale tamdem has bosses under the down tube – may be intended for a bottle cage rather than a crudcatcher as they are low down – 10 yrs ish old and gets some real hammer with no evidence of cracks. ( long fork / jumping etc etc}

For sure its a minor stress raiser but as its round it is not too bad and properly done with reinforcement around the hole it should be as strong as a plain tube.

I suggest its one of those things like fatigue fractures in alloy frames – theoretically should hap[pen but in practice is rare

ive got a a crud catcher on my P7, its been thrashed and not problem, thats the trouble when you read something like that, it will always put doubt in your mind.

load of b*llox i’d say….

I had a cheap alloy frame with crudcatcher bosses.

I did a bunnyhop over a log, upon landing I heard a cracking sound. I stopped to check my frame since I was paranoid about it breaking (I had only just snapped a Marin Nail Trail at the headtube 2 months earlier) I found a crack around half of the circumference of the downtube, right over where the crud catcher hole was.

Thankfully the force wasnt enough to fully snap the frame, but obviously the fact it cracked around the boss hole is enough to prove its a definite weak point in the frame.

ive got a a crud catcher on my P7, its been thrashed and not problem, thats the trouble when you read something like that, it will always put doubt in your mind.

load of b*llox i’d say….

I’ve seen a P7 crashed into a bombhole, the frame was ripped in 2, one of the breaks right through the crud catcher boss.

Yes, that crash would probably have bent something else had those mounts not been a weak point, but I’ll do without them thanks 🙂

I though the whole point about boses on the down tube was nothing to do with tube failure. I though that manufactures shy away from them because in a heavy stack the crud catcher can actually rip the bosses out of the frame??

I think all Brant is suggesting is that for certain materials, putting holes in certain places means that it won’t pass the test that new bikes have to pass. It’s that simple really

I’ve seen a P7 crashed into a bombhole, the frame was ripped in 2, one of the breaks right through the crud catcher boss.

Yes, that crash would probably have bent something else had those mounts not been a weak point, but I’ll do without them thanks [:)]

fair comment…..

i’ll take me chances 😉

I’m not, by the way, saying there’s anything at all wrong with the Genesis frames – it’s just that the act of putting the bosses there is a potential problem waiting to happen. It doesn’t mean it’s going to.

Is this the same as a QR in a fork is a potential problem waiting to happen but it never actually does?