Mojo Pro Bike Clinic, Fork Choices with Blake Samson

44 Comments

32 12

Sshredder (Mar 5, 2014 at 10:06)

15 mil axel is plenty strong for dirt jumping? Every one agree with that statement? I would feel safer with a 20 mil.
You run the pressure very high on your DJ fork. no shit.
Bike clinic on what? this is my shiny bike collection?

30 2

madmax650 (Mar 5, 2014 at 10:14)

Let him subliminally sell fox stuff

10 6

pjfisch (Mar 5, 2014 at 10:24)

not a dirt jumper but I'm pretty sure a 15 mil axle would be fine. I have a 20 mil for dh and that holds up just fine. I can't imagine you are putting more pressure on a dj than a full on dh rig.

14 6

ridethree (Mar 5, 2014 at 11:21)

I still can't understand why anyone would want a 15mm axle for any kind of riding

18 0

southshorepirate FL (Mar 5, 2014 at 12:12)

BMX guys mostly run, what, 10mm bolt with a 14 or 17mm internal axle? There are some 20s available, but they seem to not be the norm. A rigid fork may have less torsional flex, but they take more of a beating on harsh landings. Regardless, if you're landing sideways all the time you'll most likely blow a wheel before a 15mm axle fails.

10 1

Ghostt (Mar 5, 2014 at 13:24)

Is it common knowledge 15mm axles are weak? Or break easily? I've never seen or heard of one breaking, so I guess they're alright.

20 0

prestonDH (Mar 5, 2014 at 13:33)

I have $100 for any of you that can actually break a 15mm axle riding...

The only people that a 15mm axle could be a safety issue is pros.

LaXcarp (Mar 5, 2014 at 14:25)

Cool

joalst (Mar 5, 2014 at 15:30)

@Ghostt Yeah I'm with you. Who was the person that started this trend of 15mm being weak? Lol The only time I question an axle is with standard QR on a longer travel trail bike. (Front or rear) I guess I just like the added security of a thru-axle knowing that my wheel won't fall out of the dropout if it loosens a bit

chyu (Mar 5, 2014 at 20:01)

Why cant we have 25mm axle

R-trailking-S (Mar 5, 2014 at 21:06)

Because then we need something beside 6902 rs/similar bearings? (AKA one more custom bike specific bearing).

I like the extra rigidity of 20 mm axles. It really isn't a strength thing. Even BMX race bikes are headed toward 20 mm front hubs and 15/20 mm rear (thru axle and/or bolt).

tdryan242 (Mar 5, 2014 at 21:12)

a 15mm axel would be out of place on a dual crown rig or a super light xc fork. the size of the axel should be proportionately stiff/strong to the rest of the fork. no need to over build one particular part

R-trailking-S (Mar 5, 2014 at 21:18)

But lowered dj forks are probably just as stiff. And Sids do come with 15mm axles. So....

ridethree (Mar 6, 2014 at 1:06)

Seriously, what is the advantage of a 15mm axle?

foghorn1 (Mar 6, 2014 at 20:20)

Here's a reason 20mm is better. When landing less than perfectly, the fork gets stressed. Any place that can flex increases stresses in other places. like when the wheel deflects the axle, the rest of the lowers and the crowns get flexed. More flex = less control, and more chances to break. I'll stick to 20mm thanks.

OldSkoolAK (Mar 7, 2014 at 15:12)

The BMX axles are usually nutted and solid steel, not a hollow Al piece, cam-locked into place. So, no dice there. My personal objection to 15 is that I like the fact I can swap wheels between my DH, DJ, and Trail bikes. This world would be just fine if everyone on 15's ran 20's instead. But you have gram-chasers and ta-frickin da, you have another standard.

ridethree (Mar 8, 2014 at 14:37)

I guess we'll need some 17,5mm axles to get the best of both worlds...

Sshredder (Mar 8, 2014 at 19:23)

Tapered axels .Two different types 20 to 15 and 20 to 17.5

R-trailking-S (Mar 8, 2014 at 20:55)

Yeah, like bigger in the middle so you have to remove the bearings to get the axle out of even the hub.

17 0

preach (Mar 5, 2014 at 13:16)

am I the only one who sets their fork after about 5 minutes of riding and has never touched them again?

demery86 (Mar 6, 2014 at 1:37)

Nope, occassional air pump if I've not ridden it in a month but apart from that fit and forget (marzocchi tho, 8 year old fork now)

15 0

richard01 (Mar 5, 2014 at 10:31)

hows that CTD working out in your 831s, sounds like you need the RC2 cartridge in there.

13 2

nedersotan (Mar 5, 2014 at 11:38)

this is ridiculous it is so bad.

First he says "dirt jumping, especially doing 360's, your wheel wants to go straight, and your fork starts to twist" then a bit later he says " if you're jumping and doing tricks you don't need more than a 15mm [quick release] axle"

So which is it? I'd guess he got it right the first time, the twisting forces of landing tricks probably put the highest torsional loads on a fork, so the jump fork should get the 20mm axle.

Further, the title makes it sound like this is an article describing how to choose a fork. That you should put a jump fork on a jump bike and an all mountain fork on an all mountain bike, does not tell us anything useful.

To fulfill the title it should discuss when to run a 140 mm F32 vs a 140 mm 34 or when to use a160mm 34 vs a 160mm 36, choosing Terralogic vs CTD etc., ie viable options on one bike, not totally incompatable forks on completely different bikes.

DARKSTAR63 (Mar 5, 2014 at 13:44)

The fork gets it's torsional rigidity from it's chassis not axle. This 15mm axle nonsense is played and simply irrelevant.

MrDuck (Mar 6, 2014 at 0:29)

Well the axle definitely does affect the rigidity of the whole package though. Obviously if you try twisting any fork without an axle, it'll be quite easy (even with the overstiffened 40s). Then if you put in a wheel with a QR axle, it'll still be rather flexy, but if you put a wheel with 20mm axle to the same fork (ie Reba, which had both options), the difference is huge. Consequently, the 15mm will be somewhere in between. It'll be closer to 20mm than QR for sure, even just thanks to the way it mounts to the fork (no matter whether it's RS Maxle, that Suntour fancy axle or whatever), it'll stiffen it up, but it'll never be as strong as 20mm (unless you go out of your way sacrificing all the weight saving of 15mm, perhaps using a steel rod

)

DARKSTAR63 (Mar 6, 2014 at 5:24)

I agree that the axle is part of the structure. However I think the difference of 15 and 20mm on a stout chassis is likely minimal at best. Using the Reba as an example, that fork is not very stiff to begin with, and qr vs through axle is a noticeable difference. 15 vs 20 not so much. If we are talking strength, Iv'e not seen anybody break a front axle of any diameter in a long time. I think this is mute. Does the overall package reach the desired strength and stiffness? If yes then does anybody really care if it's 15mm?

nedersotan (Mar 6, 2014 at 19:57)

My point was that his first comment seems to state that dirt jump forks suffer the highest torsional forces of any fork, then later on he states that the 15mm axle is sufficient for Dj, but if want to go big, like on the all mountain bike, forks need 20mm axles.
Further more, the difference between 15 and 20mm axles is quite big. It's not just the small increase in diameter, it's the fact that the 15mm is a qr axle and the 20mm is clamped, creating much higher resistance to twisting.

You are right, there is nothing inherently wrong with a 15mm axle, what's wrong is having a video article claim that it will explain fork choice, then getting something as stupid as combining "in Dj-ing you really twist your fork" with "in DJ-ing you don't need the stiffer axle" in the same video.

The comments are critiquing the video, not wether or not the fork is any good.

bubbaburger911 (Mar 5, 2014 at 11:27)

this was just filler content for pinkbike. it gave me something to click on

goytay (Mar 5, 2014 at 10:27)

yea, not much info.sounds more like a " user preference" thing.

madmax650 (Mar 5, 2014 at 10:36)

Because its a fox advertisement. Duh. His "Fox 831 34 mm DJ fork with 15 mm thru axle" and his "fox 36 RC2 with 20 mm thru axle" are ideal for those specific types of riding due to their axle size. Go buy.

Haha...... I wonder if now having a 20 mm thru axle for your trail bike will be assimilated to a little guy driving around a big ass unnecessarily lifted truck with big ass unnecessary tires?

michibretz (Mar 5, 2014 at 14:50)

no, 20mm is cool too... just not enduro enough... oh... hes not talking enduro?

str8dwn (Mar 5, 2014 at 12:21)

Ah...the buzz of that Profile Elite hub...love mine.

Oh, and have you seen the MSRP for the F831 34mm? $1,000 for a DJ fork? So I can buy 3 Circus forks for the same price?

Give me free forks and I'll rave about them in a video too.

marshall1234 (Mar 5, 2014 at 16:27)

Pretty sure that buzz is from a halo supadrive hub

kingsRunEast (Mar 5, 2014 at 15:16)

"Blake explains the benefits of having a bolt thru axle and why he opts to run the 34mm 831, 15QR fork on his dirt jump bike and the 36mm RC2 with 20mm axle on his freeride bike."

Actually, he doesn't. Everytime PB pretends a video is a technical explanation or comparison and there's zero information conveyed, I just want my 3 minutes back.

oldphatguy (Mar 6, 2014 at 10:45)

In the motorcycle world dirt bikes don't use bigger than a 15mm they only go bigger on street bikes. So unless you plan on doing 150mph on your bike a 15mm axle will be just fine...
scandalon.com/2009/06/motorcycle-front-axle-diameter-chart

reddirtrides (Mar 5, 2014 at 16:50)

I am old school. my first bike (devinci cactis) had a Manitou spider fork. 8mm QR. I dirt jumped and dropped the thing. not worried about even 8mm QR. any stories of those breaking? I wold love to hear them.

j-ron46 (Mar 5, 2014 at 12:15)

Where did he say this was? Longleat? Looks sick!

Antti69 (Mar 5, 2014 at 21:02)

WOW, that was deep.........

graham454 (Mar 6, 2014 at 5:16)

Shut up and ride your bikes

aljoburr FL (Mar 6, 2014 at 11:00)

Funny how standard front bearing is 25mm id but standard axel is 15mm make sense really though?

fastlaneflyer (Mar 6, 2014 at 18:55)

Well, what i usually do is just go ride and not worry about it.

EnduroriderPL (Mar 5, 2014 at 23:25)

"U don't need 20mm axel" - BUT I WANT 20mm axel!

Crakka (Mar 5, 2014 at 21:19)

What brand was the bike?

betsie (Mar 5, 2014 at 11:12)

Freeride bike...this was replaced by all mountain ..... then big mountain...... only saw an enduro bike.