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 Chains and Sprockets

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majordad0806




PostSubject: Re: Chains and Sprockets   Fri Nov 01, 2013 12:08 pm

From an engineering standpoint I agree.  Big torque monsters would need more surface for the bolts for extra holding power
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rvsixer

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PostSubject: Re: Chains and Sprockets   Fri Nov 01, 2013 5:15 pm

Actually my concern comes not just from the engine torque load, but given the purpose of these bikes more so from the braking/landing induced shear loads.  A few bucks for a proper set of bolts is a no brainer imo, the alternative is possibly being stuck out in the field with a damaged sprocket, bolts, hub, and maybe even a cracked engine case if the chain goes wild.
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majordad0806




PostSubject: Re: Chains and Sprockets   Fri Nov 01, 2013 5:29 pm

I don't disagree. Bolts and nuts are cheap considering what could happen if stranded.
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rsteiger

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PostSubject: Re: Chains and Sprockets   Fri Nov 01, 2013 11:14 pm

If there are shear loads on those sprocket bolts then the joint is not designed right in the first place. The key to not having a joint or bolt failure is not to put the bolt in a shear load scenario.

Most people don't understand how a bolt and good joint design work. A bolt is like a big spring. As you apply more torque to the bolt it applies more clamp load to the joint which is what actually holds the joint together. Generally speaking you like to stress the bolt to roughly 80% of it's failure point. If you go above that you risk elongating the bolt and when that happens it is likely the clamp load drops off.

If the bolt is subjected to shear loads that would mean there is not enough clamp load in the design to prevent the joint from going into shear. If this happens you either need to increase the torque (which may require an increase in bolt size if you are already at the yield point of the bolt) or you need to add more bolts to increase the clamp load.
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beefcakemorris

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PostSubject: Re: Chains and Sprockets   Sun Jul 13, 2014 11:21 pm

Ok guys running a 13/47, but need to so 70 to 75 easier.

Would a 45 or a 46 be better. I don't mind cutting down the chain if I have too.
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YZEtc

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PostSubject: Re: Chains and Sprockets   Mon Jul 14, 2014 12:12 am

If you are looking to reduce engine RPM at 70 to 75 mph.
Trade-off is slower acceleration.
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beefcakemorris

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PostSubject: Re: Chains and Sprockets   Mon Jul 14, 2014 11:32 am

YZEtc wrote:
If you are looking to reduce engine RPM at 70 to 75 mph.
Trade-off is slower acceleration.

Would I be able to make up some of the acceleartion feel, when I put the FMF full exhaust system, programmer, and air box mod?
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Jäger
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PostSubject: Re: Chains and Sprockets   Mon Jul 14, 2014 12:48 pm

beefcakemorris wrote:
Ok guys running a 13/47, but need to so 70 to 75 easier.

Would a 45 or a 46 be better. I don't mind cutting down the chain if I have too.

Adding teeth at the back isn't going to result in cutting down the chain...

You get to a point of diminishing returns.  The force of air resistance is proportional to the square of the velocity, so if you double the speed you quadruple the air resistance.  At 75 mph, you are getting to the limit of what the bike can EFFECTIVELY do, meaning, up hills, in headwinds, etc.  If you want to get to 75 faster, sure, add more teeth at the rear. The fastest would, I suppose, be the gearing where you were hitting 75 mph just a little before banging off the rev limiter.

You might want to consider whether the goal of hitting 75 easier is most important to you, or whether you want gearing that fits your total riding profile best.

I run 14/49; almost what you're running.  The motor sounds and feels like it's in its sweet spot somewhere between 65 and 70 mph with the Heidenau tires I run.  Don't even look at the speedometer; the bike is just in its happy place there.  I do regular three hour slab commutes with that set up.  Yep, it will also do 75+ if I'm really in a hurry, but it also sucks gas like crazy as well - see speed versus resistance above.

You will not bang off the rev limiter with stock gearing, nor with 14/49 - unless going down hill, or with a strong tail wind, or you're really, really tiny.  I found stock gearing lacked a little bit of umph at the top end, particularly when rolling on power to pass at higher speeds, and that's why I went 14/49.  14/50 might be even better, I don't know, but 14/49 works well for a bike being used for actual 50/50 dual sport, not mostly single track/mud/rocks, and not mostly highway ripping.

If you just want to get there as fast as possible, your current 13/47 will give you 90 mph with stock tire sizes and at 10,500 RPM.  You'll be hitting 75 mph at 8500 RPM.  I'd say that's pretty good and you still have some wiggle room at the top if you need a bit more speed while doing 70.  But if you still want to get there faster yet, 13/53 will get you to 80 mph at that 10,500 RPM - that's the easiest and fastest way you're going to get to 70 - 75 mph, but I doubt you'll find the bike feels like it's in its sweet spot if you're doing that for very long.

Just my guess, but I think your bike's gearing is already about as good as it is going to get for what you're looking for.
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beer goggle

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PostSubject: Re: Chains and Sprockets   Tue Feb 10, 2015 5:54 pm

raven1 wrote:
Hi all, just replaced rear sprocket with a Supersprox 48 tooth item but left the 13 tooth front.  My bike is totally off-road use only and the difference is awesome.  Heaps more control, first gear now walks up steep inclines, also help control on the downhill sections.  Instead of running around in basically 2nd gear all the time with standard gearing, now I am using all gears except for maybe 6th.  A must do mod if your bike is only used off-road.  thumb cheers.

I read that most people find the 13/48 combo works well on and off road, however raven states it is only good for off road use. I'm planning on going down the 13/48 route for tarmac & trails. I occasionally ride the freeways and ideally would want to be able to happily cruise at 120kmh +

I guess I'm 90/10 (road/trails) in winter and 50/50 at all other times in the year. What do other 13/48'ers think of this combo?
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Evol

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PostSubject: Re: Chains and Sprockets   Tue Feb 10, 2015 6:21 pm

According to http://www.gearingcommander.com/, the top speed of our bikes with a 13/48 combo would be:

WRR 135 km/h
WRX 130 km/h

I have a 13/48/112 link chain setup waiting to be installed on my WRX before Spring, so I can't say what it actually is like riding with this combo, but I'm looking forward to a bit more "pep"...
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beer goggle

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PostSubject: Re: Chains and Sprockets   Wed Feb 11, 2015 2:35 am

Sounds perfect, will pull the trigger and order tonight. Cheers thumb
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WolfpackFBNS




PostSubject: Re: Chains and Sprockets   Mon Mar 02, 2015 9:40 pm

Just so I have a record of this:
My gearing is 14/48. I just loosened the chain. It was tight as hell when I sat on the bike. I looped a tie down strap around the swing arm and sub-frame to compress the suspension when off the bike so I could make the adjustment. The only weird thing now is that the "hash" marks on the swing arm to make sure the axle/chain is straight seem off. I have a motion pro chain alignment tool and so this is why I think the hash marks are a little off. Anyone else verify this?
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rsteiger

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PostSubject: Re: Chains and Sprockets   Mon Mar 02, 2015 11:26 pm

WolfpackFBNS wrote:
Just so I have a record of this:
My gearing is 14/48. I just loosened the chain. It was tight as hell when I sat on the bike. I looped a tie down strap around the swing arm and sub-frame to compress the suspension when off the bike so I could make the adjustment. The only weird thing now is that the "hash" marks on the swing arm to make sure the axle/chain is straight seem off. I have a motion pro chain alignment tool and so this is why I think the hash marks are a little off. Anyone else verify this?

That is not all that uncommon - manufacturing tolerances. Go by the chain alignment tool (assuming it is not bent).
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gman994




PostSubject: Re: Chains and Sprockets   Sun Mar 08, 2015 9:45 pm

I've read thru this thread several times and still can't come to a decision on sprocket selection. So, not to beat a dead horse, but I am going to ask for opinions/advice on this. I have a 2014 WR250R, no performance mods other than a 12 tooth sprocket on the front. I've had it offroad one time up to this point. The terrain was hilly, muddy, rooty, and some large sandhills mixed in. It didn't take long for me to figure out that these tires were not made for this. I spent more time rubber up than down. So, I decided that before I try this again I need some dirt worthy tires and a gearing arrangement that doesn't require as much clutch finesse. I still plan on riding on the road, but mostly county and State routes. I'm steering towards the Dunlop 606 for the rear, and possibly a 49 tooth rear sprocket. I read where a lot of guys are happy with the 13/48 setup, but are they running the taller 606's ? I figure with the 12/49 selection, the 606's will minus a couple from the rear, but wil still net a ratio of 12/47, which ought to really enhance the offroad ability of the bike. I'm just wanting it to operate in its powerband without having to go real fast to do it when in technical terrain. I really like low end torque, it's controllable, but that isn't this bike's forte. I'm eager for any advice. Thanks.
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Evol

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PostSubject: Re: Chains and Sprockets   Sun Mar 08, 2015 10:51 pm

Keep an eye on your swingarm slider with that 12 tooth front.

http://wr250rforum.forumotion.com/t4825-swingarm-eaten-by-chain


Last edited by Evol on Mon Mar 09, 2015 8:31 am; edited 1 time in total
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gman994




PostSubject: Re: Chains and Sprockets   Sun Mar 08, 2015 10:57 pm

Heck, I'll put the 13 back on if the 12 can cause problems. But will the 13/49 with the taller tires get me where I want to be ?
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Evol

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PostSubject: Re: Chains and Sprockets   Sun Mar 08, 2015 11:04 pm

Honestly I don't know.
I have a 13/48 setup sitting around here in my office waiting to be installed on my WRX (on 17's). Until now I've been using the stock 13/42 gearing.
I'm anxious for this snow to go so I can play around on the bike again and try the new gearing.
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gman994




PostSubject: Re: Chains and Sprockets   Sun Mar 08, 2015 11:07 pm

I almost forgot, I was looking at my rim and it does not appear to have rimlocks for the tire, or am I just not looking close enough?
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speersie

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PostSubject: Re: Chains and Sprockets   Mon Mar 09, 2015 12:33 am

gman994 wrote:
I almost forgot, I was looking at my rim and it does not appear to have rimlocks for the tire, or am I just not looking close enough?

Nope you are correct. They do not come with rim locks. I asked the dealer when I got mine serviced for the first time but he didn't seem very interested in pulling the tyres off and putting them back on and told me to wait until I had worn out this set of tyres. He didn't even believe me until I went and showed him. I wish I knew when I first purchased the bike so I could have leaned on him an got them done as part of the deal. Ah well I have some now sitting there to be installed.
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D.triggs




PostSubject: Re: Chains and Sprockets   Tue Mar 31, 2015 9:12 pm

Hey guys I recently bought a 2015 wr250r I love the bike awesome all around bike to mess around on . I can clutch up wheelies in 1-2nd and third if I pogo it real hard . I'd like to be able to do 3rd gear clutch up wheelies as easy as I can woth keeping as Much top end as possible . I am thinking and just dropping one tooth in the front to get a better idea . Has anyone done this ? What are 3rd gear wheelies like with this little mod . And what gears would you recommend for fairly easy clutch up 3rd gear wheelies
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rsteiger

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PostSubject: Re: Chains and Sprockets   Wed Apr 01, 2015 7:36 am

D.triggs wrote:
Hey guys I recently bought a 2015 wr250r I love the bike awesome all around bike to mess around on . I can clutch up wheelies in 1-2nd and third if I pogo it real hard . I'd like to be able to do 3rd gear clutch up wheelies as easy as I can woth keeping as Much top end as possible . I am thinking and just dropping one tooth in the front to get a better idea . Has anyone done this ? What are 3rd gear wheelies like with this little mod . And what gears would you recommend for fairly easy clutch up 3rd gear wheelies

Hell why stop there.. why not 4th and 5th gear wheelies?

Just buy the $12 front sprocket and find out. Personally I don't find much use for wheelies unless I am trying to pivot turn on a tight trail or get over a log/obstacle.

https://www.rockymountainatvmc.com/p/3175/27106/Primary-Drive-XTS-Front-Sprocket?v=10553
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Jens Eskildsen




PostSubject: Re: Chains and Sprockets   Wed Apr 01, 2015 2:23 pm

I have 14-50, clutch-ups in 3rd is no problem. Opened up intake, aftermarked exhaust, no programmer.
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D.triggs




PostSubject: Re: Chains and Sprockets   Wed Apr 01, 2015 7:34 pm

What is your top end with 14/50?
I have a 2015 wr250r lovin it no regrets here
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Jens Eskildsen




PostSubject: Re: Chains and Sprockets   Thu Apr 02, 2015 2:13 am

Theres a lot of top end, but im not sure about the cruising speed if thats what you meen. Im pretty biased because of my lowreving xt600, but have taken a small sprint of interstate (ca 65km times two) on it at 100km/h.

Im adding a 48 rear for an upcoming trip from Denmark to Sweden, where I will put around 1500km on the bike.

But people seem to agree that this bike is a screamer, and can take it.
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Evol

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PostSubject: Re: Chains and Sprockets   Thu Apr 16, 2015 7:51 pm

I rode some highway today with the new 13/48 setup. 
WRX on 17's (Distanzia's).

At 100km/h (62mph), it sounds like it's screaming.
At 123km/h (76mph) it's really screaming.
SpeedoDRD adjusted and GPS confirmed!!!

According to Gearing Commander, I should top out at 127km/h (79mph).

I would NOT get a 13/48 setup if you're planning to hit the highways.


Although it is a LOT more fun at slower speeds with the 13/48 gearing.

Edit: I've ordered a new 42 rear sprocket to go back to stock gearing as I ride at higher speeds more often.


Last edited by Evol on Sun May 03, 2015 8:00 pm; edited 3 times in total
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