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When I am descending with my cross country mountain bike my fork is open when I am riding on gravel, dirt roads or more technical sections.

But when I am descending on a smooth / paved road is it better to lock my front fork or should I drive with an open fork ?

When breaking hard in the corners the fork sags when it is open and it feels strange for me on a paved road. I wonder if this brake dive improves braking or if it is detrimental for cornering speed.

3 Answers 3

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I think it should not matter at all, specially if you use a fork that is tuned with the generally advisable sag or less, and if available, other parameters like rebound are tuned properly.

Locking forks where created mainly to eliminate pedal bob when pedaling really hard. Most of the people I ride or have rode with, have no need to lock the fork when pedaling at mid pace on flats or even in not so steep climbs. At least in the forks Iv'e used, rebound control helps against pedal bob. I have a locking fork, but I rarely need to lock it, not even on steep climbs (admittedly, I'm not a fast climber even though I really do enjoy climbing steep hills)

A fork with a lot of sag, specially with a lot of travel, or a fork with too little damping (too fast rebound), can feel dangerous on descents, but I think that if the fork is too soft for smooth roads, then it is useless for aggressive, technical MTB descents. All of this is to say, check that your fork is adjusted properly for your weight and the type of riding you actually do with this bike.

Once your fork is tuned properly, you should do what you feel more comfortable with, that is, adjust your bike and use it's features so you feel safer and ride with more confidence, since that will allow for more ride time enjoying and less time worrying.

If you feel more confident locking your fork on paved descents, then don't doubt about it and use the lock. The only reason I could find not to do it, is if you think you may encounter some unexpected obstacle while going down, but, in that case, my advise is to not go full speed on a road/trail you are not familiar with. Some forks do have such a feature that if they receive a hard enough compressing force while locked, they release the lock either temporarily or until you unlock and re-lock. Look for this information in your fork's user manual.

If you are "new" to MTB, I recommend working on your descending skills, I really think that once having the confidence for technical descents, you shouldn't worry about locking or not on smooth/paved.

I'm sure that MTB being my primary ride discipline, I'm so used to the fork travel and weight shifting that when I'm on paved road, I don't even think about that in particular, I just feel I does not affect me at all and I think It comes down to a very different braking technique. When MTB riding, I apply sharp brake strokes that go almost to full hand strength and then quickly release. In contrast, while in road I apply the brakes gently, in long, slowly modulated strokes that are so less prone to produce sudden brake dive. Besides that, MTB "cornering" and road "cornering" have such different turn radii and happen at such different speed that I don't think they are comparable in terms of technique.

I'm an MTB rider with some experience in Downhill racing and have also done some road riding on rigid fork hybrid bikes, so I can say I have experience in riding with forks ranging from 0 to 200 mm. In my road riding (I don't do road racing) I've been able to keep up with experienced road riders going downhill on paved roads with both, a rigid fork and a non lockable air fork, in the same stretches of road, and I did not feel any problem with the fork compressing when braking.

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It depends on the quality of the road. I have descended with my fork open a few times just because there were so many bumps and holes.

However 99% of the time its definitely better locked on a paved surface.

Brake dive is a significant disadvantage and on a smooth paved roads there are no advantages to offset it.

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    “99% of the time is definitely better locked on a paved surface” – no. About 60% it makes no difference at all on a paved surface – a properly set up bike shouldn't bob on the front whilst normally pedalling in the saddle. On intensive climbs, certainly whenever out of the saddle, locked out is better – but not as dramatically better as people often claim. And on descends, opening definitely can't hurt – brake dive is a complete non-issue in any sensible paved-road scenario. May 20 at 15:44
  • brake dive is an issue every single time you hit the brakes hard. is it a big issue? no, you can compensate for it with lower centre of gravity etc, but it's better not to have to.
    – Andy P
    May 20 at 18:07
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    I don't see what's better about not having to compensate for brake dive. For one thing, you need to be able to do that anyway (unless you never ride terrain that requires a mountainbike in the first place), and practising it also on tarmac can't be a bad thing. But also, even if you don't compensate for it at all, nothing bad happens that wouldn't also happen with a rigid fork – only when going with brake dive into technical terrain it increases the risk of OTB, but not on tarmac. May 20 at 20:48
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It shouldn't really matter. While coasting on a paved road, an open suspension fork doesn't really do anything most of the time. Brake dive isn't a problem unless it's a long-travel fork, you're running it at low pressure, the road is extremely steep and you're descending it in a hunched-over position without dropped saddle, which is a bad idea anyway. If you find this “feels weird” then you should reconsider your fork setup and/or riding technique – I would recommend dropper post for paved descends (improves aero in addition to stability), and when braking in corners you should get in a stable position where you're ready to unclip and extend the inner foot in case you lose grip.
Or else just stop worrying about the sag. (Brake dive is an issue on technical downhill, but there you obviously also need the suspension and riding technique can compensate.)

Riding with the fork open does have the advantage of making you safe against unexpected potholes and the like. I would just make it a habit to always unlock the fork on any descent. (Forgetting to unlock on a technical descend is much worse than forgetting to lock on a climb.)

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  • Well, it doesn't really matter in that the bike is rideable both ways and get you down the hill. It is more a matter of preference. Those with more of a road bike background (like myself) prefer the feel of the road and the quicker response of working from a solid, fork locked foundation when carving turns on a paved decent. When a fork is not locked, braking and weight shift will cause the fork to move which moves the precise line that you carve a turn with. I won't downvote you, because you make some good points, but it won't sway me from locking my fork on a normal paved descent.
    – Ted Hohl
    May 20 at 16:51
  • @TedHohl well, can't argue with personal preference... however, claims about “quicker response” I find rather dubious. Downhill MTBers certainly achieve quick response! A rigid fork feels quicker, because you simply feel more of everything. The feeling can certainly increase the fun factor (I myself like to operate my shocks at higher pressure than recommended for my weight), but it probably means you actually end up going slower. Which may not be a bad thing for safety, though then again I would say the suspension also improves safety due to better grip on rough parts. May 20 at 17:31
  • leftaroundabout - we are talking about pavement here. And excluding very rough, pothole-ridden or heavily patched tarmac, the solid foundation is preferred. You would see road racers using suspension more if your claim included pavement. That said, I have many times wished for a little more suspension on my gravel rig on downhills for sure. But on pavement (what the question was specifically asking about), not so much. If the question was referring to singletrack MTB or downhill I would 100% agree with you. Ride on!
    – Ted Hohl
    May 20 at 22:40

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