Fox F Forks for example come in:

– 15QR thru-axle system
– 9 mm open drop-out

Is there any major advantage to get a 15mmQR on an XC HT bike? Never really noticed any flex on my 100mm 5mm QR setup?

security of teh axle version

i've got 15mm on sids but i can't tell you whether it is better than 5mm QR as i've never tried it. they are noticeably stiffer than some late 90s sids that i've got but then that's probably more effected by stanchion thickness. 32 new 28 old….

15mm sids? not seen them

hmm. doubt id notice then. never had an issue with qr security so ? Cheers guys 🙂

According to Fox there's another upside to 15mm, in that the left and right fork legs are prevented from as much independent action relative to each other. This will decrease fork stiction (or at least that aspect of stiction which comes from / is worsened by forces not in line with the fork's action). They claim this will lead to a more responsive fork at least in terms of small bump sensitivity. Seems like sound engineering sense to me, and I guess this is especially the case for XC bikes with their inevitable air forks, which often suffer from more initial stiction than coil forks

The 15mm axle is a one-piece affair and so that little nut on the end of the QR axle can move and so means a bit of messing about when fitting. I've used both and much prefer the 15mm axle or 20mm than over normal QR and even if the benefit of a stiffer front end is marginal I still think it's worth it.

After using both, i'd ask if there's any point in QR rather than the other way round.Mine is noticably stiffer than my older TALAS, more secure, and once you've set your desired closing tension then it's quicker for removing and refitting the wheel too.

To answer the original question – probably very little if any noticeable difference on a 100mm fox.

However, I've noticed the benefits to fox stiffening up their forks.
Originally had a 100 float rlc- brilliant, stiff, tracked well etc.
Moved to a 05/06 float 130 rlc – not as good, not as stiff and in my (non Mtb journo lingo) felt vague.
Next iteration 08 van 140 r – much stiffer due to improved lowers etc. Really good fork
just recently 09 float 140 r 15 qr – noticeable difference in stiffness. Very pleased so far.

I think a great deal depends on rider weight. I'm probably hovering at 13 1/2 stone and I think parts ride differently as compared to my 11 stone riding buddies.

You get used to a fork and how it rides, if you never ride stiff forks, QR is fine.

Coming from a pair of pikes to some 100mm QR foxes the foxes are a bit twangy – but still loads better than QR forks of old. Depends how you ride too, if you're ragging the bike you'll notice a flexy fork more.

i've got 15mm on sids

You have some 2011 SIDs already?

If you have a problem with forks feeling wobbly then I can see the point, but I do question the merit on a 100mm XC fork myself.

njee20 – Member

You have some 2011 SIDs already?

no just a totally sh*t memory – 9mm here after checking

coat…

Yup – I guess were only talking a few grams heavier say 90g – hmm – food for thought – cheers guys 🙂

I have some magura durin race forks and with standard 5mm QR I found them to be pretty good tracking with no noticable flex, I fitted some new wheels which use a hadley 9mm bolt through axle, still no flex and no obvious difference. However I fitted a 10mm bolt through axle to the rear of my slightly flexi full suss and it is noticibly stiffer. I guess if your forks feel flexi the 9mm through axle makes a difference so if you find standard QR versions of forks flex then the 20mm or 15mm through axle version of them should be markably stiffer.

15mm is much stiffer, noticed it instantly on 100mm RLC's. That said the fork itself flexes a hell of lot, I thought my headset was knackered.

The thru axle noticeably makes the front end track better and deflect less. Its also more secure.

I put QR15 lowers on my Fox Floats and the difference is amazing! Much stiffer, quicker steering to the point that I nearly put myself in a hedge on the first ride. Considering the stanchions were the same it can only be down to the QR15.

I wouldn't buy a fork without a bolt thru again.

I guess it depends on the fork… Comparing bolt through and QR Revelations and Rebas, I've not found anything to write home about, since they're decently stiff with QR anyway. With F100s or similiar I'd expect it'd make a bigger difference since they're a little more squiggly. But it's just one part of the overall design. The weight difference is pretty minor in any case but with a decently stiff fork I don't think it's needed, myself.