ad327 Posted September 30, 2008 Report Share Posted September 30, 2008 I'd be dead chuffed if someone could explain to a novice why the freewheel (on an XTP) is at the bottom bracket rather than the rear hub. Ta,Al Quote Link to comment Share on other sites More sharing options...
Andrex Posted September 30, 2008 Report Share Posted September 30, 2008 I think its for a stronger engagement. Where it is at the back you have the chain to engage it, but at the front the force is directly off the cranks.Someone correct me if I am wrong lol Quote Link to comment Share on other sites More sharing options...
spaceman Posted September 30, 2008 Report Share Posted September 30, 2008 I'm pretty sure someone has posted this recently. Anyway, I may be wrong, but I read that it was something to do with some "weight distribution", since the freewheel is at the BB, meaning centre of the bike, the weight is more centred/neutral. I also think that having the freewheel at the BB means you could engage your chain instantly, reaction time faster. Having it at the hub means you have to engage your chain first (the sag), then engage the hub. Quote Link to comment Share on other sites More sharing options...
Mark W Posted September 30, 2008 Report Share Posted September 30, 2008 The chain is still effectively holding the driveshell of the freewheel though, so it's not really different.Main benefits are that a front freewheel (FFW) setup is generally lighter especially for the weight of your back wheel, it's also usually cheaper - especially for the manufacturer, in comps it's easier to carry a crank arm with a spare freewheel on it around than a spare rear wheel (In case the drivetrain breaks in some way), there are a lot of good and reasonably cheap freewheels around, and so on.EDIT: History wise, I'm guessing it was because back when 18t freewheels were the smallest commonly available size, having an 18t freewheel on the back meant a 24t sprocket on the front (Meaning you'd have to have a huge bashguard to clear it), whereas if you put the freewheel on the front you could run a smaller rear sprocket and have a lighter, more compact setup. I wouldn't really have thought centralising the weight was the main aim, in that between having a freewheel on a freewheel hub at the back (Which was the option when FFW was first around) and a sprocket at the front, and a sprocket on a freewheel hub at the back and a freewheel at the front, there couldn't be much difference? Quote Link to comment Share on other sites More sharing options...
that NBR dude Posted September 30, 2008 Report Share Posted September 30, 2008 EDIT: History wise, I'm guessing it was because back when 18t freewheels were the smallest commonly available size, having an 18t freewheel on the back meant a 24t sprocket on the front (Meaning you'd have to have a huge bashguard to clear it), whereas if you put the freewheel on the front you could run a smaller rear sprocket and have a lighter, more compact setup. I wouldn't really have thought centralising the weight was the main aim, in that between having a freewheel on a freewheel hub at the back (Which was the option when FFW was first around) and a sprocket at the front, and a sprocket on a freewheel hub at the back and a freewheel at the front, there couldn't be much difference?As far as Im aware thats exactly why. I dont think you can get much smaller than a 16tooth as any smaller and it wouldn't be able to thread onto the hub. Quote Link to comment Share on other sites More sharing options...
Muel Posted September 30, 2008 Report Share Posted September 30, 2008 (edited) I'm pretty sure it was originally because they used BMX rear hubs, so if you had a screw-on rear sprocket and a front freewheel the gap between the chain and the stays was smaller, so if you landed on it you had less chance of snapping it.EDIT: It actually lighter overall to have a rear freehub, or it was when I last added it up, which was before the Try-All H hubs came out. Edited September 30, 2008 by Muel Quote Link to comment Share on other sites More sharing options...
Ash-Kennard Posted September 30, 2008 Report Share Posted September 30, 2008 im pretty sure it was so stock riders could change gear without having to pedal... Quote Link to comment Share on other sites More sharing options...
Matthew_Gibson Posted September 30, 2008 Report Share Posted September 30, 2008 im pretty sure it was so stock riders could change gear without having to pedal...that what I was told. By the guys in super cycles. back in the day Quote Link to comment Share on other sites More sharing options...
PaRtZ Posted September 30, 2008 Report Share Posted September 30, 2008 im pretty sure it was so stock riders could change gear without having to pedal...Thats true, but it means you need a stretch of freewheeling i.e. rolling down a hill, rolling up to something which in trials you tend not to get chance to doI thought the main reason was as mark said 18t freewheels being the abundance and allowing smaller gearing. This also gives better clearance on underneath the BB so as you dont catch it.In terms of drive, theres not really any DISADVANTAGE to have a 18t freewheel on the wheel and a 22t? cog on the front. Just means you'll need a bigger bashring too, and more chain Quote Link to comment Share on other sites More sharing options...
Token Posted September 30, 2008 Report Share Posted September 30, 2008 (edited) And clearance...running a 18tooth freewheel upfront gives you more clearance compared to running a 18tooth freewheel at the rear and a 24tooth fixed ring up front.edit: okay i didnt see matty boy has already made this clear :$ Edited September 30, 2008 by Gok Wan Quote Link to comment Share on other sites More sharing options...
Aaron.Tottman Posted October 2, 2008 Report Share Posted October 2, 2008 i was talking to the uk megamo/koxx importer when i was working for halfords and he said''if you rip the ratchet in the back wheel 8time out of 10 you'll need to change the wheel.''''ona trial it's more veasable to carry a spair free-wheel over carrying a spair wheel''''engagment is almost instent when it dose so at the cranks''and you also weight dis' Quote Link to comment Share on other sites More sharing options...
mafu26 Posted October 2, 2008 Report Share Posted October 2, 2008 i remember agggggessssssss ago talking to martin walker and his idea was there was less mass to move when you go for a rolling explosive pedaling move because the chain is already moving therefore you don't have to make the extra effort in order to get the chain moving... bit far fetched! but at the time we were convinced that was the reason until someone told us about being able to run an overall smaller set of cogs for clearence by having the freewheel at front. Quote Link to comment Share on other sites More sharing options...
Marten@ScandinavianTrials Posted October 2, 2008 Report Share Posted October 2, 2008 (edited) However, the smaller cog thing is only valid when using normal freewheels. If using a standard cassette hub on the rear and a threaded sprocket on the cranks you could actually run 15-12 (instead of 18-15). But then again, if chain snappage was an issue before...Some driver hubs, albeit not the best for trials perhaps, take 9 t sprockets...The reason is probably that MODs using BMX-spacing often used normal feewheels, and then as trials specific components started developing the industry kind of got stuck with that idea... (On the whole, the bike industry is as innovative as the dining table industry imho. but then again, as with dining tables - not much to be innovative about.)The weight dist. idea isn't valid in my opinion. My new rear hub is heavier than my old one, despite the old one being a cassette hub and the new one a fixed one. The overall weight of my drivetrain is heavier with the ffw combo than the old one. In theory it could be valid, TryAll H-hubs are lighter than cassette hubs so...Plus, if you were to take out your Texas Instruments calculator and be a bit scientific about it you could easily find that a ffw actually has a tougher job to do than the freewheel on a hub due to gear ratios. And when applying the same to effective poe per crank revolution, the freewheel on the hub wins. 60 poe on the rear is better than 60 on the cranks. If you don't believe me, then don't I know I'm right anyway. 1.2*60=72 whereas 60=60 (duh).1,2 is the ratio of 18/15. Edited October 2, 2008 by Marten@ScandinavianTrials Quote Link to comment Share on other sites More sharing options...
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