[Closed] DH World Cup mechanicals

Drive trains? Will be SRAM 7sp DH, Shimano Saint or some custom combo of stuff

Singlespeed? Tracks do have a point where pedalling is easier in a lower or better in a higher gear, out of corners etc. and you know it's familiar

Chainless? It's a different mindset and an all or nothing sort of thing, coming into that gap a bit slow just give it a few cranks, oh wait, can I have a dentist

I believe the normal set up is a seven or eight speed close range cassette. The chains are still the standard ten speed jobs, because a wider chain isn't really any stronger. The majority of chain failures you see are out of the start gate, meaning Maximum power,  and probably trying to shift at the same time.

And to be fair, how many chain failures have there been?

Craic

No lower chain guides, no bash rings. Chains getting damaged from rock strikes, chains snapping on the next run during the highest load. That'd be my guess.

Number of punctures is ridiculous, for one reason or another. So many race runs ruined, latest being Luca Shaw in finals, aaron gwin in quali's.

Everyone is snapping their chain on purpose and hoping to get a good run down. After they seen all the attention gwin got a couple years ago, they are after a bit of the same.

Ok not really, but for punctures I heard that the 29er guys are not using the heavier DH casings but instead using the lighter folding tyres to save a bit of weight.

SRAM XO 7 spd DH is massively flawed.

It uses 10 speed spacing, 10 speed chains and has too wide a cassete ratio with too many gears

What they should be running is 8 or 9 speed spaced cassettes, an 8 speed chain and a 5 cassette sprockets fitted bang in the midde of the chainline. (and switch chainring size if needed for optimum earing for the course they're racing). and for the riders/mechanics to work out which gears they actually need. (For most a 11, 12, 14, 16, 18  cassette and a 36T NW ring should work for racing pretty much every DH track in the entire world)

firstly that would allow a shorter chain, way less chainslap. (so little infact that a clutch mech wouldn't actually be required and suspension would not be affected so much) far less extreme chain angles. and less shifting.

Using a current shifter is the main problem here. Everything else is readily available.

the 29er punctures are 100% deserved! think of it as a tax.

Mostly this:

The majority of chain failures you see are out of the start gate, meaning Maximum power,  and probably trying to shift at the same time.

Mostly not this

SRAM XO 7 spd DH is massively flawed

I was about to have a look and see who actually snapped chains and what they were on but mostly that...

Though I'm sure SRAM will be looking for somebody to redesign their massivly flawed groupsets, on the number of runs taken, age of the kit etc. some of that could just be packet failures on a lighter chain etc.

As for punctures shit happens, had my hands on Gregs tyres from Cairns they were a thick casing, not quite full on old schoold dh casings but not that far off.

the 29er punctures are 100% deserved! think of it as a tax.

😂😂😂

The Maxxis DH 29er tyres have a Kevlar bead (and are tubeless compatible) unlike the 26/27.5 versions. Carcass isn’t different from the diddy versions though.

I dunno.  Coincidence?    Roadie sprinters put down oodles of power but you rarely see a snapped chain.

But on the road if you had a weakness in your chain it would probably have exposed itself in the previous 150km

I was wondering this also after Fort William. I haven't snapped a chain in years, last time would have been a good 18+ years ago (although my riding has changed from DH/jumps to xc enduro style stuff).

Im guessing that the effected teams and manufactures have looked into it. Regards 10s spaced cassettes vs 8sp - is there a correlation. Do 10sp gears snap more chains than 8. I wouldn't have thought so.

My guess is it could be that it's due to the quick turn around by mechanics on the wc circuit - the bikes go through hell and require regular breakdowns and build back ups. From memory, most chain snaps ice had have been directly after doing some work on the drive train. (or not dissing any of the mechanics though).

Road sprints are more often than not wound up from (a tow at) 25mph+ to what? 40mph on smooth roads
DH starts are sprints from a standing start to around 25mph on rough ground with suspension chaingrowth loads thrown in for good measure. The two require the chain to deal with quite different loads and cadence ranges. not that it matters all that much. The real problem that is breaking chains in the first 20 meters of DH races is shifting under load prising the chain plate from the pins. not the chain plates snaping from ultimate power.
The real point here regarding chains failing is that it KEEPS HAPPENING. To top ranked DH riders on big budget teams with full time mechanics DURING RACE RUNS. This should not be happening at all. Nevermind keep happening over a prolongued period. Have a look and remind yourself when this phenomenon started happening.

As for XO DH. It doesn't even have a dedicated freehub. it uses a normal 10/11spd XO freehub.
if you were designing a cassette/hub specifically for 7 speed DH use why wouldn't you use a shorter freehub body allowing wider/stronger hub spoke flanges, better spacing and chainline?
Why would you choose a cassette range of 10-12-14-16-18-21-24 when there's absolutley no need for the 24T or 21T sprocket at all in a DH race run anywhere in the world?
The 10T sprocket is there to allow the use of a smaller chainring and better clearance but that jump from 10T to 12T sprocket creates a far greater ratio jump than between any other two gears on any cassette.
If you really need 7 gears for a DH race bike (you don't!) why would you want 2 sprockets you'll never ever use on a race run instead of closer ratios at the top end? ie. 10 - 11 - 12  instead of that pointless 24T?
These points are all massive flaws AFAIC.

The real point here regarding chains failing is that it KEEPS HAPPENING. To top ranked DH riders on big budget teams with full time mechanics DURING RACE RUNS. This should not be happening at all. Nevermind keep happening over a prolongued period. Have a look and remind yourself when this phenomenon started happening.

Are they all using SRAM?, Ho many chains snapped in practice?

These points are all massive flaws AFAIC.

Truly massive!!

To be fair, Geex may have a point - does anyone know why Gwin is on an unknown drivetrain?

He is American? Lets have the chain snapping stats by drivetrain type and race vs quali

most chain snaps ice had have been directly after doing some work on the drive train. (or not dissing any of the mechanics though).

Me too, though I've not had many. You have to feel for the mechanics. They must feel terrible when something goes wrong like that.

Anyone used to race the Dragons? The seeding run was done chainless for a time. It did elicit a few moans if I recall.

Don't they fit a new chain after virtually every run? Or certainly before finals. Human error?

As for XO DH. It doesn’t even have a dedicated freehub. it uses a normal 10/11spd XO freehub.
if you were designing a cassette/hub specifically for 7 speed DH use why wouldn’t you use a shorter freehub

You say that likes it’s a bad thing! We don’t need another free hub design for what is a niche aspect of the sport especially if you need to recoup money by selling it to the OE’s and the public.

Fitting brand new chains before race runs just seems like a bad idea, surely better to stick with low-use but tested stuff, get out of the bathtub. Unless there's damage a day old chain should be a safer bet than a brand new one...

Seems like the 2 main reasons for mechanicals are 1, they put things on that they want to sell rather than necessarily what's the best option and 2, losing reliability can be a good tradeoff for a few extra tenths, especially for people who're not in overall contention- a podium or even top 10 one race is a good trade for a DNF or rubbish result in the next if you're just chasing best results not season points. But I think it's mostly 1.

Aside; the DH maxxis 29ers are light, as someone mentioned they're foldy not wire bead and some people say that's where the weight difference is but if that's true, and there's no downside, why aren't the 650b ones foldy? There's no way it's not a compromise. They work great for me but I am not a world cup pro dh rider like Geex.

Fitting brand new chains before race runs just seems like a bad idea, surely better to stick with low-use but tested stuff, get out of the bathtub. Unless there’s damage a day old chain should be a safer bet than a brand new one…

and again this one is probably more speculation than fact as to what could be happening

I'm on CRC now trying to find Geex's drivetrain for DH, sounds like something I need

Oh I'm not speculating, it's just an often repeated thing that "they fit new chains" and I think it's interesting. I'm sure it'll be true for some but by and large disturbing things that work and fitting brand new parts isn't a good policy.

@Mindmap a new freehub design is not a requirement. simply a shorter one. These are already available for use with shimano cassettes. and wouldn't have required a re-design for XD

@Northwind Whoever (if anyone) stated new chains are fitted to the bikes for race runs made it up.

So all these snapped chains. There was two at fort william, gwin at leogang, (three years ago) I'm sure there have been more, but it's hardly a massive issue.

Best guess on gwin's unmarked drivetrain is it's a prototype E13 set up. SRAM and box have both denied it's theirs.

So all these snapped chains. There was two at fort william,

3 I think? Gwin, Luca Shaw and Rachel Atherton?

It's relatively rare, but it's there.

Lucia Shaw was a puncture

Ah yes.

@Northwind I’m guessing that the production TLR DH casing 27.5 tyres will be folders too. They’re currently steel beaded and non-TLR?

@geex  not so sure if it is made up you know. I remember speaking to Ben Arnott who was Trek head mechanic (now YT I think) at hafjell in Norway and asked him if they fitted a new chain "like all the time" I think i said.

He said "no not always but we always check them after every run and usually replace"  However yes as a WC Dher you probably know better than us mortals. 🙂

I imagine if you walked up the pits and asked all the mechanics you'd get a different answer from all of them about how often they change chains.

1, they put things on that they want to sell rather than necessarily what’s the best option

hmmm, I've seen Maxxis DHR pretending to be all sorts of brands, In my rigorous scientific studies 'd say the opposite is just as true.

The real problem that is breaking chains in the first 20 meters of DH races is shifting under load prising the chain plate from the pins. not the chain plates snaping from ultimate power.
The real point here regarding chains failing is that it KEEPS HAPPENING. To top ranked DH riders on big budget teams with full time mechanics DURING RACE RUNS. This should not be happening at all.

Pretty straight forwards ... and put like that hardly rocket science.

The exact parts of the chain that has got weaker ...

You say that likes it’s a bad thing! We don’t need another free hub design for what is a niche aspect of the sport

7-8 speed free hubs are hardly new.... SRAM used to use them ... before they introduced another unneeded* standard.

*I guess that's debatable but it is debatable IMHO.

Most specifically in the debate though is why the standard for XC hubs would/should be the same as the standard for DH hubs...

especially if you need to recoup money by selling it to the OE’s and the public.

Well "the public" are probably a bit misguided if they want the same hub for their trail bike as used on a DH bike???  Isn't that like asking why we don't have dual crown forks in 120mm??? (Half genuine... surely the "public" realise their trail bike would be horrible with a 120mm dual crown ??? So why not hubs)

Weren't some of the fastest people through the speed trap at the weekend running with snapped chains? Maybe SS would be better! Certainly suggests that teams aren't really sure what the best technique is for the lower section where pedalling hard didn't seem to do much at all (perhaps due to the loss of energy from leaning the bike side to side and being higher on the bike increasing wind resistance)

Most specifically in the debate though is why the standard for XC hubs would/should be the same as the standard for DH hubs…

Or what problem are you trying to fix?

(Not to go over it and open it up again... XD solved splines, wear and the 11sp minimum which gave is usable wide range 11sp for the last however many years)

Is there an issue with DH freehubs?

Is there actually anything to say the spacing is causing chains to snap?

Is the SRAM gear worse than the Shimano stuff or is it all just guessing here?

As for chainless and tracks, it's a very different mindset with zero margin for error.

The standard for xc hubs isn't the same as the "standard" for DH hubs. Back in the day, xc was 135qr, and DH 150mm bolt through. Now, it's a free for all, everything from specialized using 135×12 to pivots 157×12. Even the length of the freehub varies on some.

The weak point on a chain is where the outside plate joins the pin, and is no different on an eight speed. And again, two last weekend, leogang three..... years ago, anymore? Hardly really worth redesigning an entire drivetrain. I'd say chain failures are probably less than other components, and a lot less than wheel, and a shit load less than tyre.