Got Any DH Questions? Ask Them Here

PB Forum :: Downhill
Got Any DH Questions? Ask Them Here
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Posted: Jun 11, 2021 at 14:07 Quote
Shame Spec stopped doing their Deviant line. Those breathed SUPER well.

Posted: Jun 11, 2021 at 14:25 Quote
Bars are too high when you start to loose mid corner traction as the weigh isn't being push through the front.... fellow praymantis set up.

Posted: Jun 11, 2021 at 15:06 Quote
Nobble wrote:
GAQ wrote:
anybody have a recommendation for a DH helmet with good ventilation for hot weather.
im looking to spend about $300 but the budget is flexible.
are you going to be climbing in it too?

If not, stay away from the Enduro helmets like the programs, and Stage.

Might do a little climbing
But not too much

Posted: Jun 11, 2021 at 16:56 Quote
The best helmet is the one that fits. Try them on. There's really no other answer. But as someone else already stated, if it's pure DH riding then do not get a light Enduro full face. stick with a true DH full face.

Posted: Jun 14, 2021 at 21:06 Quote
Hey guys,

Not really downhill specific... but I was just really curious if there was a good source out there to read about the history of mountain bike standards & sizing. I have the impresión that before “standards” bike and component company’s would build stuff without much collaboration and either the component company would have to adapt to the bikes and vice versa. I remember reading somewhere about shock sizes and the reason that before metric we had all these odd (arbitrary) sizes was because for example a big bike company would design a frame with “X” eye to eye size and “Y” stroke and send in a huge order to a shock supplier for that specific sizing. Then, smaller bike company’s had to make do with that shock size and stroke because it’s what was available and they didn’t have the economical power to order a big enough amount of shocks for a shock company to build them specific shocks for their frames. For example: who came up with steerer tube sizing and why that size; why 31.8mm for handlebar clamps and who (I think 35 was Easton?); who decided to use different hub sizes to what was standard in roadie (I think it started off like that jeje and I think Trek pushed 135 x 12 to 142 and then I think again Trek with Sram pushed in Boost); etc

Thanks!

Posted: Jun 15, 2021 at 10:42 Quote
szot123 wrote:
Hey guys,
Not really downhill specific... but I was just really curious if there was a good source out there to read about the history of mountain bike standards & sizing.
Thanks!
I know sheldonbrown.com and parktool.com have lots of info about bike maintenance and standards. sheldonbrown.com is a website by a bicycle mechanic who died in 2008. His friends kept adding info to it, and kept the nineties look on purpose.

Posted: Jun 15, 2021 at 11:08 Quote
szot123 wrote:
Hey guys,

Not really downhill specific... but I was just really curious if there was a good source out there to read about the history of mountain bike standards & sizing. I have the impresión that before “standards” bike and component company’s would build stuff without much collaboration and either the component company would have to adapt to the bikes and vice versa. I remember reading somewhere about shock sizes and the reason that before metric we had all these odd (arbitrary) sizes was because for example a big bike company would design a frame with “X” eye to eye size and “Y” stroke and send in a huge order to a shock supplier for that specific sizing. Then, smaller bike company’s had to make do with that shock size and stroke because it’s what was available and they didn’t have the economical power to order a big enough amount of shocks for a shock company to build them specific shocks for their frames. For example: who came up with steerer tube sizing and why that size; why 31.8mm for handlebar clamps and who (I think 35 was Easton?); who decided to use different hub sizes to what was standard in roadie (I think it started off like that jeje and I think Trek pushed 135 x 12 to 142 and then I think again Trek with Sram pushed in Boost); etc

Thanks!

A lot of things came about in the 90's through the early 2000's to push past existing issue or to compromise on a better/lighter solution. Tapered came from 1.5 being used for DH/freeride bikes so the "lighter" tapered alternative came about.

Bars had issues at 25mm(1in) so the pushed to 31.8(1.25in) then everyone thought even bigger is better so 35 came about (partially due to being more visually appealing) but they can be too stiff so now we have two standards.

Brake mounting went through a few iterations overtime before getting to the current post mount (Answer/Manitou).

Breaking the old school QR hubs led to DH bikes using through axels and many bikes had proprietary spacing it eventually was narrowed down and adopted for all bikes.

random tab and proprietary chain guide tabs to ISCG then onto ISCG 05

Posted: Jun 19, 2021 at 11:57 Quote
Can anyone give me a rundown on what sizes I should be looking at for different brands? I don't think I'll have the luxury of sitting on a bike before I buy it as I'll likely have to order new or get something used shipped.

I'm 6'3 with a 33"ish inseam, so I have a longer torso. I'm currently riding an XL Mojo HD5 which fits perfectly. Considering a 29er DH rig.

For example, it looks like I would be a large on a Sender but an XL on a Session. I'd do primarily park days and will probably have some race days thrown in. TIA

Posted: Jun 19, 2021 at 12:05 Quote
For your height I’d be looking at the geometry tables for a bike with a reach of 475-500mm

Posted: Jun 19, 2021 at 12:07 Quote
mengler wrote:
Can anyone give me a rundown on what sizes I should be looking at for different brands? I don't think I'll have the luxury of sitting on a bike before I buy it as I'll likely have to order new or get something used shipped.

I'm 6'3 with a 33"ish inseam, so I have a longer torso. I'm currently riding an XL Mojo HD5 which fits perfectly. Considering a 29er DH rig.

For example it looks like I would be a large on a Sender but an XL on a Session. I'd do primarily park days and will probably have some race days thrown in. TIA

Since your current bike fits perfect look for a similar reach. If you have to size down or up for the bike you want, always size up. In my opinion it has always been better for me to go longer rather than shorter (made a very expensive mistake with my Enduro s works)

Posted: Jun 19, 2021 at 15:14 Quote
Thanks guys. Probably gonna pre-order an X-Long Tues 29er tonight.

Posted: Jun 19, 2021 at 16:14 Quote
After riding the 29er DH bike for two years I think they are great for racing but on the bikepark I’m not sure they are as fun as 27.5 or mixed wheel sizes (never tried one mullet DH bike).

Posted: Jun 19, 2021 at 16:23 Quote
norfiril wrote:
After riding the 29er DH bike for two years I think they are great for racing but on the bikepark I’m not sure they are as fun as 27.5 or mixed wheel sizes (never tried one mullet DH bike).

I agree. I tried 29 and it was fast and smooth af but prefer the more playful feel of 27.5. I managed to snag one of the last remaining 2021 27.5 commencal supremes and have no regrets.

Posted: Jun 29, 2021 at 21:11 Quote
norfiril wrote:
After riding the 29er DH bike for two years I think they are great for racing but on the bikepark I’m not sure they are as fun as 27.5 or mixed wheel sizes (never tried one mullet DH bike).
I disagree love 29” wheels


 
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