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Offline DJ

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Re: Re-Gear 39 tooth out back with 16 tooth up front
« Reply #10 on: June 11, 2019, 01:54:06 AM »
*Originally Posted by JMo [+]
You have low[er] gears so you can keep moving at a snails pace without putting your feet down.

Like a trials rider does.

All having [too] tall gears will do is cause you to slip the clutch and potentially stall, or else wheelspin as you try to rev the engine high enough to make enough torque to not stall/burn out the clutch.

Jx


So the key take away here is "really technical terrain". 
Let's check out what kind of RPMs we are talking about here in really technical terrain.
Stock bike with 15/41 sprockets.
At 1mph, a stock cb500x in 1st gear turns 249 rpms at the crank. Stalling.
At 2 mph a stock bike is turning 499 rpm. Stalling.
At 5 mph a stock bike is turning a whopping 1247 rpm. Right at idle speed.  Stalling on anything but flat ground.

Really technical terrain is requiring you to heavily feather the clutch on stock gearing. This is not a technical terrain bike.

Now a bike with 16/39 sprockets:
At 1 mph a modified bike turns 222 rpm. Stalling and still feathering the clutch like a madman.  Insane 27 rpm difference. No effect on low speed riding. Sorry.

At 2mph a modified bike is turning at 445 rpm, a difference of 54 rpms. Still feathering the clutch like mad trying to keep moving.

At 5mph a modified bike turns at 1112 rpm, a difference of 135 rpm.  Still feathering the clutch like mad, why? Because any useful torque isn't available until 2100 rpms.

Check it.
Stock cb500x makes roughly 13 lb ft of torque at 2100 rpms. 2100 rpms!
So if your riding in slow technical terrain , your slipping the clutch regardless of gearing to keep this particular bike outputting usable torque in the rpm range. 27, 54, 135 RPMs will not make a lick of difference, I dont care how good you are! Sorry.

BUT! as you rise in speed you reap the rewards. That 11% reduction in rpms was only worth 135 revolutions at 5mph.  Take it up to 75 and that 11% turns into 643 rpms on the highway. A worthwhile difference and one that will extend the life or your chain, sprockets, engine and you!

Since getting my bike I've put 900 miles on it in a few weeks.  Half has been on dirt and half on the highway.  I have to hit highway to get to the dirt stuff.   It is better on both now. Its more relaxed and enjoyable on the highway. I can actually do 70 without feeling bad for my machine. 1st gear off road is fantastic. I've hit powerline roads, fireroads and a few steep wooded single tracks. Led the way with buddies on a xt250 and KLX250. Every time we ride they are like, I can't believe you took your street bike up that! Dont sweat it, gearing won't hurt or help with this type of bike offroad. It has many other limitations to run up against like suspension, ground clearance and weight before you hit a "gearing wall".

JMO I've watched a ton of your videos, the Rubicon trail was especially impressive. Much respect. 98% of us would not even consider taking a cb500x on that trail. That 98% will benefit from a gear change so please keep in mind the audience on these forums when making recommendations. What's best for you isn't best for the rest!

It would be honored to ride with you someday!

Engine speeds taken off:
https://www.gearingcommander.com/
« Last Edit: June 11, 2019, 01:58:00 AM by DJ »

Online JMo

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Re: Re-Gear 39 tooth out back with 16 tooth up front
« Reply #11 on: June 11, 2019, 07:04:50 AM »
*Originally Posted by DJ [+]

So the key take away here is "really technical terrain". 
Let's check out what kind of RPMs we are talking about here in really technical terrain.
Stock bike with 15/41 sprockets.
At 1mph, a stock cb500x in 1st gear turns 249 rpms at the crank. Stalling.
At 2 mph a stock bike is turning 499 rpm. Stalling.
At 5 mph a stock bike is turning a whopping 1247 rpm. Right at idle speed.  Stalling on anything but flat ground.

Really technical terrain is requiring you to heavily feather the clutch on stock gearing. This is not a technical terrain bike.

Now a bike with 16/39 sprockets:
At 1 mph a modified bike turns 222 rpm. Stalling and still feathering the clutch like a madman.  Insane 27 rpm difference. No effect on low speed riding. Sorry.

At 2mph a modified bike is turning at 445 rpm, a difference of 54 rpms. Still feathering the clutch like mad trying to keep moving.

At 5mph a modified bike turns at 1112 rpm, a difference of 135 rpm.  Still feathering the clutch like mad, why? Because any useful torque isn't available until 2100 rpms.

Check it.
Stock cb500x makes roughly 13 lb ft of torque at 2100 rpms. 2100 rpms!
So if your riding in slow technical terrain , your slipping the clutch regardless of gearing to keep this particular bike outputting usable torque in the rpm range. 27, 54, 135 RPMs will not make a lick of difference, I dont care how good you are! Sorry.

BUT! as you rise in speed you reap the rewards. That 11% reduction in rpms was only worth 135 revolutions at 5mph.  Take it up to 75 and that 11% turns into 643 rpms on the highway. A worthwhile difference and one that will extend the life or your chain, sprockets, engine and you!

Since getting my bike I've put 900 miles on it in a few weeks.  Half has been on dirt and half on the highway.  I have to hit highway to get to the dirt stuff.   It is better on both now. Its more relaxed and enjoyable on the highway. I can actually do 70 without feeling bad for my machine. 1st gear off road is fantastic. I've hit powerline roads, fireroads and a few steep wooded single tracks. Led the way with buddies on a xt250 and KLX250. Every time we ride they are like, I can't believe you took your street bike up that! Dont sweat it, gearing won't hurt or help with this type of bike offroad. It has many other limitations to run up against like suspension, ground clearance and weight before you hit a "gearing wall".

JMO I've watched a ton of your videos, the Rubicon trail was especially impressive. Much respect. 98% of us would not even consider taking a cb500x on that trail. That 98% will benefit from a gear change so please keep in mind the audience on these forums when making recommendations. What's best for you isn't best for the rest!

It would be honored to ride with you someday!

Engine speeds taken off:
https://www.gearingcommander.com/

Im not going to argue the toss with you DJ - as I said originally, youve found a set-up that works for you and thats great...

But a bunch of RPM numbers from the internet doesnt equate to how a bike actually rides at lower speeds - changing from 15/41 to 16/39 is a change of just over 12%, so yes you will get an appreciable increase in speed/lowering of RPM at higher revs... but you also loose 12% torque, everywhere - and that is what keeps the bike chugging along off-road in technical terrain, and helps with engine-breaking on steep down hill sections...

To give you an illustration, if youve ever ridden an F700/800GS for example (which has 17/43 gearing), it feels like it hasnt got a first gear compared to the CB500X (on stock 15/41)... similarly changing the front sprocket on the G310GS (another bike on which I covered a lot of miles last year) from stock 16T to 15T made a noticable difference to how well it would lug at low RPM, and going up to 43T (from 41 stock) on the rear made a significant improvement, albeit at the expense of the overall RPMs at top speed of course.

So suggesting that changing to 16/39 doesnt make any difference off-road is simply not true. It might not make much of a difference to the way you personally ride - and as Ive said all along, thats great - but like all things mechanical, if you change the bias of something in one direction, then there are concequences in the opposite (in this instance a reduction in torque) - which may affect some riders more than others.

You dont get ought for nowt as they say.

Jx


It's not a unicorn as such, just a little mule with a bump on it's head... www.CB500Xadventure.com

Offline PIGLET

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Re: Re-Gear 39 tooth out back with 16 tooth up front
« Reply #12 on: June 11, 2019, 07:52:41 AM »
I have done 2000 miles on my 2019 honda cb500x  so now i have a good feel for the bike,
I will change to a 16 tooth on the front first  to see how the bike feels for me but i (think) the 1 tooth up
will be a good thing. (time will tell).

Offline DJ

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Re: Re-Gear 39 tooth out back with 16 tooth up front
« Reply #13 on: June 11, 2019, 03:05:29 PM »
No no no no, I never said it doesn't make a difference off road. OF COURSE IT DOES YOUR CHANGING GEAR RATIOS! I said the difference at such low speed is negligible for 98% of us who ride off road.
Of course it makes a difference. I do believe you are missing my point.
And your right a bunch of numbers doesn't equate to how a bike handles off road, it simply illustrates the small differences at such low speeds and dont forget your slipping the clutch like crazy either way.  A simple point, let's not complicate it.
Being pedantic here but I calculated an engine speed difference of 10.8%.

I'm not sure bringing up other bikes is a good idea. Every bike is different. Different transmission gears, weight, torque curves and such.  I have not doubt that going from a 15t to a 16t on that little 310 made a huge difference.  Not comparable. That's just muddying the water here.

I didn't want this to turn into a debate but I somehow forgot the internet will internet.

Internet on!

Oh and Piglet you won't regret the gear change!  Best mod so far right next the the rally raid bash plate.  That sucker already saved my bike a handful of times! Going over Kelly humps I drug bottom and I bottomed out on a few rocks, hard hits.  It's easy to forget just how little clearance this bike has.

Offline PIGLET

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Re: Re-Gear 39 tooth out back with 16 tooth up front
« Reply #14 on: June 11, 2019, 03:59:22 PM »
Thanks DJ 95%  for me is on road so the 1 tooth will be a nice change (cheap also) :152: :152: :152:

Offline SilverCycle

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Re: Re-Gear 39 tooth out back with 16 tooth up front
« Reply #15 on: June 11, 2019, 04:15:59 PM »
Just as a matter of interest, how does it work on technical off road with a bigger brother Honda with DCT? Is the system ok automatically dragging the clutch?

I suppose it could even invisibly alternate between 1st and 2nd to let the clutches cool down. Are they wet or dry or neither?

Or is there a lever somewhere marked "L" like on a real 4x4?

Offline Jonathan

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Re: Re-Gear 39 tooth out back with 16 tooth up front
« Reply #16 on: June 11, 2019, 08:27:33 PM »
if you look at bikes designed for really technical terrain ie Trials bikes, the key is Very low gearing, a mahoosive flywheel and ultra low tyre pressures....neither of which is great for general road riding. Racing bikes will routinely change the gearing to suit the type of track they're on (along with ecu mapping, suspension, tyre choice etc.) It's all to do with marginal gains based on the situation...

the stock gearing on the X (including wheel/tyre size) will have been determined during the design stage, to best suit the engine characteristics, based on the X's anticipated usage as a mid-weight A2 friendly general commuter...changing a couple of teeth here and there won't radically alter the nature of the bike, but it obviously suits certain owner's preferences. Maybe there's some scope for switchable mapping, but I've not seen any development in this area

Offline Oyabun

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Re: Re-Gear 39 tooth out back with 16 tooth up front
« Reply #17 on: June 11, 2019, 11:36:50 PM »
*Originally Posted by Jonathan [+]
Maybe there's some scope for switchable mapping, but I've not seen any development in this area
I have switchable maps on one of my X-es, but it's done via a Dynojet Power commander V. We've been trying to get switchable maps on the stock ecu - and while we're able to load new maps on the ecu, we currently cannot have two at the same time and change between those.
Which is a theoretical issue anyway, as one xan only alter fueling, ignition, decel fuel cutoff and rev limit regarding performance on the X (as it has mechanical throttle, no valve timing etc) so not much in regards of drive modes can be developed.
On my bike I have a performance map (no or less fuel cutoff on decel, AFR is 14.2 at part throtthle & 12.8 anywhere above 40% load. The other is a lean cruise with stoich fueling everywhre else, stock decel fuel cutoff and conservative igniton timing.
Sounds like a lot, but in fact the difference is not that difficult significant

Offline SilverCycle

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Re: Re-Gear 39 tooth out back with 16 tooth up front
« Reply #18 on: June 12, 2019, 08:18:22 AM »
Err, Oyabun, if you don't mind, could you refine that post with a bit less abbreviations and an edit? I found it a bit indigestible, but I ought to be able to understand it. With a following wind.

Offline Oyabun

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Re: Re-Gear 39 tooth out back with 16 tooth up front
« Reply #19 on: June 12, 2019, 08:41:23 AM »
Sorry, editing time window is over.
It's gonna be off topic here, this is really an answer to a question about switchable maps.

To summarize in plain language.
We have ECU (Engine Control Unit) reflash (kind of reprogramming the operation parameters, not the entire operation) solution for the oem pre-19 ecus - but the maps are not switchable.
Currently on the fly switchable maps available with external hardware Dynojet Power Commander V.).
AFR means Air Fuel Ratio - where AFR 14.7 (14.7 weight unit of air is mixed with 1 weight unit of fuel) also called stoich, or Lambda 1 is the mixture of lowest emissions. This is where the engines are normally set ro operate. Smaller numbers mean richer, larger ones leaner mixture.
One of my maps is developed for performance with richer mixture, more aggressive ignition timing and no fuel cutoff at deceleration. The other one is an economy - cruise setup with leaner mixtures and conservative ignition timing.
Hope it helps.
« Last Edit: June 12, 2019, 09:11:25 AM by Oyabun »

 


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