Unofficial Royal Enfield Community Forum

Royal Enfield Motorcycles => Bullet with the UCE engine => Topic started by: 1 Thump on January 23, 2010, 11:29:05 pm

Title: C5 Vs G5
Post by: 1 Thump on January 23, 2010, 11:29:05 pm
Is it true that the two models have different tire sizes and sprockets, and as aresult perform differently on the road ?

Is there anything else that the bikes do not share , performance wise, and which bike performs better ( pickup, top speed, mileage etc ).
Title: Re: C5 Vs G5
Post by: t120rbullet on January 24, 2010, 12:14:12 am
The G5 has a 17 tooth gearbox sprocket and 19" tires.
The C5 has an 18 tooth sprocket and 18" tires.

I have ridden both and thought the C5 handled a bit more twitchy as in the steering was a bit more responsive (not a bad thing). I ended up buying the G5 but not because of the handling.
Both bikes handle exceptionally and have their strong and weak points. Either one is a good choice in motorcycles.
CJ
Title: Re: C5 Vs G5
Post by: Geirskogul on January 24, 2010, 02:12:38 am
Best of both worlds with the G5 - UCE engine and a kickstarter.  Do that one.
Title: Re: C5 Vs G5
Post by: hocko on January 24, 2010, 05:24:29 am
I debated long and hard before buying the G5. Reason for that choice ? Simple,  one had a kick start the other didn't.

Cheers  :)
Title: Re: C5 Vs G5
Post by: heindlengineering on January 24, 2010, 01:49:33 pm
We see a lot of customers look at the C5 and then buy the G5.  Personally, I like the looks of the G5 better.  I think that the ride is similar.
Title: Re: C5 Vs G5
Post by: ace.cafe on January 24, 2010, 02:21:33 pm
I think that they need to re-style the side cover area on the G5.
It's the same as the Electra X, and I have never liked those chrome(or even black) "sausage boxes" nor the shape of the side covers.

I realize that they are trying to get more use out of the old Electra X body parts, but I consider it a big styling flaw which doesn't need to be on the new models.
I think they could have done alot  better than that to begin with on the Electra X, and they certainly shouldn't have carried it forward onto  the G5.

There are alot of different ways to style that area that could look alot cooler.

On the C5, I think the 18" wheels were a mistake, and they need to return that to 19" wheels, or at least a 19" wheel on the front.
It was common back in the old days to use a 19" front and 18" rear.
My Ducati 750 bevelhead twins had 19" front and 18" rear, and had a leading-axle fork too, and it handled like it was on rails.
There are enough comments about the C5 feeling "light and twitchy" at higher speeds that the added rotational stability of a 19" wheel would make sense, too.
And the 19" front wheel looks very good on that modified C5 that ScooterBob did.
Other than that, the C5 looks just about perfect for 50s styling, especially with the aftermarket upswept muffler on it.

Overall, both models are very close to being "just right" but could use a little "tweaking" to get them perfect. Not much needed, but a little.
Title: Re: C5 Vs G5
Post by: r80rt on January 24, 2010, 02:22:22 pm
I took one look at the C5 and forgot there were any other motorcycles, I bought it and I've been delighted with it ever since.  ;D Ace is right about the wheels, I will be going to a 19" front soon.
Title: Re: C5 Vs G5
Post by: holodeck on January 24, 2010, 05:25:55 pm
+1 on what ace and r80rt said.
Title: Re: C5 Vs G5
Post by: 1 Thump on January 24, 2010, 06:14:10 pm
On the C5, I think the 18" wheels were a mistake, and they need to return that to 19" wheels, or at least a 19" wheel on the front.
It was common back in the old days to use a 19" front and 18" rear.
My Ducati 750 bevelhead twins had 19" front and 18" rear, and had a leading-axle fork too, and it handled like it was on rails.
There are enough comments about the C5 feeling "light and twitchy" at higher speeds that the added rotational stability of a 19" wheel would make sense, too.
And the 19" front wheel looks very good on that modified C5 that ScooterBob did.


I have an AVL Electra 2009. Will it help to put 19inch wheel no teh front. How about the gear sprocket.
Title: Re: C5 Vs G5
Post by: ace.cafe on January 24, 2010, 06:19:19 pm
I have an AVL Electra 2009. Will it help to put 19inch wheel no teh front. How about the gear sprocket.

The Electra X models all have 19" wheels on them as standard equipment.
Title: Re: C5 Vs G5
Post by: r80rt on January 24, 2010, 07:49:52 pm
I like the idea of a 18" rear and 19" front, that will allow me to run tires I'm familliar with. A lot of the bikes I've had were set up that way. I'm positive a 19" front will get rid of most if not all ot the light twitchyness.
Title: Re: C5 Vs G5
Post by: ace.cafe on January 24, 2010, 08:23:41 pm
I like the idea of a 18" rear and 19" front, that will allow me to run tires I'm familliar with. A lot of the bikes I've had were set up that way. I'm positive a 19" front will get rid of most if not all ot the light twitchyness.

A larger diameter front wheel/tire will increase trail geometry and improve straight-line stability.
And the larger diameter front wheel improves the gyroscopic stabilization that the wheels provide on a motorcycle
Overall stability should improve.
There probably will be a bit more effort required to get it to turn into a corner.
This is a trade-off, that's probably worth it in this case.

To  check your trail measurement, put the bike on level ground, off the centerstand(have somebody hold it upright),  take a yardstick or tape measure and use it to extend the center axis of the steering head all the way to the ground, on the same angle the fork legs are on, and mark that spot on the ground.  That mark will be forward of the tire contact patch.
Then, drop a plumb line from the center of the axle, and mark that spot on the ground, and  it should be in the center of your tire contact patch.
The measurement between those two marks is your trail measurement
Being that the C5 has a leading-axle fork, the axle will be forward of the bottom of the fork leg, so it will vary from the diagram below. No matter, you just drop the line from wherever the axle is located, and with the C5 it will be on the leading axle flange.


I'd be interested to know what the trail measurement of the C5 is, if you want to measure it for us.


(http://www.thompsonchoppers.com/images/rake_trail.jpg)
Title: Re: C5 Vs G5
Post by: r80rt on January 24, 2010, 08:56:16 pm
Well, I'm home alone so I propped the bike up straight and measured down the fork leg with a yard stick, I had to use a level for a plumb bob but that should work shouldn't it?
 I measured 3 times and came up with a measurement of 4 5/8" when I have help I'll try again.

OK I just saw I should have measured from the steering head, I'' try it again when my lovely assistant comes home.
Title: Re: C5 Vs G5
Post by: ace.cafe on January 24, 2010, 08:59:08 pm
Well, I'm home alone so I propped the bike up straight and measured down the fork leg with a yard stick, I had to use a level for a plumb bob but that should work shouldn't it?
 I measured 3 times and came up with a measurement of 4 5/8" when I have help I'll try again.

Yes, that should be close enough.
4-5/8" trail is plenty of trail, and there should be no problem with the stability of that bike.
But, maybe it likes a little more. Sometimes they are funny like that.

If you wanna see how much a 19" wheel will change it, then roll the front wheel up on a half-inch thick board, and measure it again. That will simulate the larger wheel on there.

Please NOTE:
I changed my  post to show that you use the steering head axis for the measurement, and not the fork leg. I made a mistake in my first writing, and went back and changed it. I didn't account for the offset, when I stated to use the fork leg.
Title: Re: C5 Vs G5
Post by: r80rt on January 24, 2010, 09:11:12 pm
There isn't a stability problem with my bike, I'm really more interested in the 19" for tire selection.  But Scooter Bob says it is a good handling improvement so that's just icing on the cake for me.
Title: Re: C5 Vs G5
Post by: chinoy on January 25, 2010, 05:14:29 am
The G5 is probably an end of line product.
Has RE said they plan to continue making them.

I fell in love with the twin spark.
The seat is so comfortable. The riding position is such a pleasure.
It looks so cool.
The C5 in comparo is Ugly.
Im sorry but a 1950s design is just not appealing to me.

But they didn't have it with a UCE 500 engine in it. In the end HP wins over looks and I paid for the C5.
All you guys buying a bike just for the kicker is absurd. Just ask your dealers to import a crate full of side covers and kickers from India.


If you wanted the UCE engine then the only choice in India is the C5.
Initially we all thought that the 18" wheels would be a huge improvement on the handling.
In fact if you do the Trail and have a rough look at the bikes geometry it looks more like a RD than a Bullet. I wont be surprised if the numbers match to the MM.

I guess it all depends on the kind of roads you plan to drive on.
If its a straight road then a 19" conversion makes sense.
If its a twisty road. Then your going to prefer the flick-ablity of the 18" setup.
I dont see the change making any major changes to the setup of the bike.
Your probably going to have more change from the gyroscopic forces than the change in Trail.

The 18" wheels are a blast to ride in the hills.
The bike likes to be thrown around.

Finding rubber in 19" is next to impossible here. You really dont have many choices.

Meet an old Time Physics Professor. RD owners, Bullet owner since before I was born. Owned nearly every model made by RE.. Now plans on buying the C5.
He came to me to discuss his RD build.

He passed a very interesting comment.
The bullets always felt like the swing arm was on a hinge.
I felt like he had nailed the problem I was having on the head.

He is on the faculty of some of the countries top Engineer collages.
And had some interesting ideas to sort out the handling.

In short pick the bike based on the type of roads you plan to use.
Ps: A popular mod Ive seen locally is a 15" rear and a 19" front.
Title: Re: C5 Vs G5
Post by: ace.cafe on January 25, 2010, 02:31:01 pm
The swing arm is on rubber mounts around the pivot shaft.
It was designed that way a long time ago for comfort purposes.
There is some flex in it there.

Racers often use a bronze bushing replacement for it.
However, the rubber mountings are a bitch to get out, and most resort to burning it out with a torch, and then chiseling out the metal rings.

If you put in bronze bushings, then install a zirk fitting for a grease gun, so you can grease them. It will work fine, and no flex in the mounts anymore.

Title: Re: C5 Vs G5
Post by: 1 Thump on January 25, 2010, 07:03:42 pm
Since the rear wheel is spun by the engine, a smaller sprocket, in theory should spin faster. Does that increase acceleration , and add more stress to the engine.
Title: Re: C5 Vs G5
Post by: Geirskogul on January 25, 2010, 08:52:56 pm
No a smaller sprocket reduces acceleration but increases top speed, while keeping top-end stress the same or higher on the engine and increasing stress at lower speeds.

Like a smaller rear sprocket at a particular motorcycle gear increases stress, but also increases speed, it lowers acceleration.
Title: Re: C5 Vs G5
Post by: 1 Thump on January 26, 2010, 12:09:07 am
Seems counter-intutive.

 But I m no gear-head.
Title: Re: C5 Vs G5
Post by: Geirskogul on January 26, 2010, 07:28:43 am
You're forgetting everything about acceleration and gearing.

A smaller sprocket will allow you to go at a higher speed at lower revs, but the engine will have to work just as hard or harder.  Acceleration will decrease based on engine power.


Try accelerating a bicycle to 25mph using your leg power (a fixed amount of HP and Torque) going through the gears sequentially.  Now try to accelerate to 25mph using only gears 2, 4, and 6.  Your acceleration (rate of increasing speed) will be slower due to the limitation of your biological hp and torque (power) factor.

In an engine with infinite power, yes a smaller sprocket will increase acceleration.  When you hit a fixed wall in the total equation, something is compromised.

If what you said was absolutely true, we all would be running 6 tooth front sprockets and 6 tooth rear sprockets, because it would be faster, instead of 18t front and 45t rear.  We need the gearing to compensate for power losses, both at certain RPMs and totally as a whole on the peak ranges.  :)  As you said, you're not a gear-head.
Title: Re: C5 Vs G5
Post by: 1 Thump on February 02, 2010, 11:59:06 pm
I took one look at the C5 and forgot there were any other motorcycles, I bought it and I've been delighted with it ever since.  ;D Ace is right about the wheels, I will be going to a 19" front soon.

I imagine it will require new rims and tires . Will it also require adjustment in the forks, and fenders.
Title: Re: C5 Vs G5
Post by: r80rt on February 03, 2010, 02:39:24 am
From what I understand the 19" wheel is a pretty easy swap.
Title: Re: C5 Vs G5
Post by: chinoy on February 03, 2010, 07:48:14 am
could somebody who has done the swap define easy ?
My take is it will need
A complete new rim, spokes, hub, rotor, mudgurad.
Because you cant use the 18" hub with a 19" rim the number of spokes are different.
Title: Re: C5 Vs G5
Post by: ace.cafe on February 03, 2010, 02:52:16 pm
could somebody who has done the swap define easy ?
My take is it will need
A complete new rim, spokes, hub, rotor, mudgurad.
Because you cant use the 18" hub with a 19" rim the number of spokes are different.


The number of spokes are the same for the 18" and 19" wheels for the Bullet.
Both have 40 spokes.
Title: Re: C5 Vs G5
Post by: motomataya on February 03, 2010, 04:10:00 pm
I build a lot of wheels for race bikes. If you handed me a C5 wheel and said make it a 19 it would be just under $300. This is without a tire.The hardest part for you is to find someone locally to do this.
Title: Re: C5 Vs G5
Post by: Monty on February 03, 2010, 04:25:39 pm
Sounds like a lot of you don't like the new C5.  For me it is a thing of beauty, but then I like the retro look.  Besides the Kick start, why is it that the C5 is not well received
Title: Re: C5 Vs G5
Post by: Kruiser on February 03, 2010, 05:32:06 pm
Sounds like a lot of you don't like the new C5.  For me it is a thing of beauty, but then I like the retro look.  Besides the Kick start, why is it that the C5 is not well received

I think it is a beautiful looking motorcycle too.
Title: Re: C5 Vs G5
Post by: Anon on February 03, 2010, 07:54:16 pm
Sounds like a lot of you don't like the new C5.  For me it is a thing of beauty, but then I like the retro look.  Besides the Kick start, why is it that the C5 is not well received

No, quite the contrary.  I think the C5 is very well liked by most around here.  There are a few who don't care for the styling, but I think the general consensus is that RE have done a fantastic job and it is a realy beauty!

Eamon
Title: Re: C5 Vs G5
Post by: cyrusb on February 03, 2010, 09:16:04 pm
Bullets produced in Reddich after 1955 had 17 inch wheels front and rear. Go figure?
Title: Re: C5 Vs G5
Post by: r80rt on February 04, 2010, 12:24:16 am
I love my C5, and I don't care about a kicker, wouldn't use it if it were there.
Title: Re: C5 Vs G5
Post by: motomataya on February 04, 2010, 01:20:28 am
The only reason to put a kicker on these is so you can look cool kickstarting them.
Title: Re: C5 Vs G5
Post by: r80rt on February 04, 2010, 01:32:12 am
Yeah, I kick started motorcycles for 40 years because I had no choice, I like the little magic button  ;D
Title: Re: C5 Vs G5
Post by: chinoy on February 09, 2010, 04:46:31 am
Nearly every single UCE owner I know dumps the kick starter.
I did. It saves you over 1 KG in dead weight.

Id give anything to swap out the side cover for one without a kicker hole.

Title: Re: C5 Vs G5
Post by: hocko on February 10, 2010, 10:59:08 pm
Nearly every single UCE owner I know dumps the kick starter.
I did. It saves you over 1 KG in dead weight.

Id give anything to swap out the side cover for one without a kicker hole.


It's probably just me, but on a bike like the enfield what difference is a kg going to make overall, I certainly won't be getting rid of the manual leg any time soon.

Cheers   :)
Title: Re: C5 Vs G5
Post by: ace.cafe on February 10, 2010, 11:33:54 pm
I dunno, maybe it's just my warped mind?
But to me, the starter motor and starter solenoid and extra gears and bigger battery and higher capacity charging system are the "dead weight".
I think all that stuff makes a measly little kickstart lever seem quite lightweight in comparison.
Title: Re: C5 Vs G5
Post by: clubman on February 13, 2010, 10:29:11 am
The only reason to put a kicker on these is so you can look cool kickstarting them.

But very uncool if you fail to start them! I've only tried a couple of times, in the privacy of my drive, and no go. It's winter though; I'll have another go later in the year.
Title: Re: C5 Vs G5
Post by: 1 Thump on February 14, 2010, 09:52:57 pm
You're forgetting everything about acceleration and gearing.

A smaller sprocket will allow you to go at a higher speed at lower revs, but the engine will have to work just as hard or harder.  Acceleration will decrease based on engine power.


Try accelerating a bicycle to 25mph using your leg power (a fixed amount of HP and Torque) going through the gears sequentially.  Now try to accelerate to 25mph using only gears 2, 4, and 6.  Your acceleration (rate of increasing speed) will be slower due to the limitation of your biological hp and torque (power) factor.

In an engine with infinite power, yes a smaller sprocket will increase acceleration.  When you hit a fixed wall in the total equation, something is compromised.

If what you said was absolutely true, we all would be running 6 tooth front sprockets and 6 tooth rear sprockets, because it would be faster, instead of 18t front and 45t rear.  We need the gearing to compensate for power losses, both at certain RPMs and totally as a whole on the peak ranges.  :)  As you said, you're not a gear-head.

I read up on gears after this exchange. So if I understand it correctly, if the fifth gear is made smaller, maybe smaller than the countershaft sprocket, like an overdrive gear, thenit is theoretically possible to retain the benefits of acceleration at lower speeds, and a higher cruising speed in 5th gear. Now why has none thought about doing this modification.
Title: Re: C5 Vs G5
Post by: motomataya on February 15, 2010, 12:09:03 am
You have to maintain the proper gear ratio spacing between gears or the ridability will suffer. And making a set of gears is no quick easy thing.
Title: Re: C5 Vs G5
Post by: 1 Thump on February 15, 2010, 04:48:20 pm
True, but u r only changing the 5th gear. The larger countershaft sprockets are commonly used. I think since the bike is primarily made for the indian market, wher eu really cant speed, and is used to haul stuff, it makes sense to emphasise low gear riding.
Title: Re: C5 Vs G5
Post by: motomataya on February 15, 2010, 05:31:21 pm
No Doubt they are geared for India. I think one more tooth on the front sprocket is a good Idea for many people in this country. One thing I forgot is these transmissions use a 1-1 fifth gear. Since is dosn't run through the layshaft there is no way to change fifth gear. Someone correct me if I am wrong.
Title: Re: C5 Vs G5
Post by: 1 Thump on February 15, 2010, 06:22:16 pm
I hope Ace is reading this.
Title: Re: C5 Vs G5
Post by: ace.cafe on February 15, 2010, 06:59:49 pm
I'm reading this now.

I'm afraid that the gearing isn't going to be affecting your cruising speeds as you seem to want.

A taller final drive ratio will help you cruise at a lower rpm than before, but it's still putting out the same hp to make that speed, so you just have a wider throttle position.

Gears aren't magic. They can't make your bike cruise faster. They just change the rpm it cruises at. It still has to make the same hp, has the same(or more) load on the engine, and the engine is limited by a percentage of its total output for cruising.
If we could all make our bikes go faster by a simple gear ratio change, then we'd all be doing 200mph
There's more to it than that.
It might help a little bit with some reduced friction, but it's only minor.

So let's get down to brass tacks.
How fast do you want to cruise on this bike?
Title: Re: C5 Vs G5
Post by: 1 Thump on February 15, 2010, 09:08:01 pm
65 mph will put a big smile on my face. I have put a short exhaust. A 30 mm carb, 20 tooth sprocket and a more open air filter (undetermined yet) are next on the list.

In theroy: The Electra can go to 65 mph easily, just not recommended for cruising at the speed because of the added stress on the engine. However, with a larger gear ratio, same (not more) speed can be achieved with less stress on the engine. Thats why they have these larger sprockets to begin with. 
Title: Re: C5 Vs G5
Post by: Anon on February 15, 2010, 09:20:35 pm
I recently had a guy come up to me as I was getting ready to fire up my bike.  He said "Dude, you should get a 3 speed transmission - they're fast!"  I started to explain that gearing determines what rpm you'll be at for a given speed, but can't change your speed unless you're geared badly to begin with.  You need more power and/or less drag to go faster  He responded by starting to lecture me about his friend with a 3 speed whose bike was now "wicked fast" and that "torque is where speed comes from."  He said my 5 speed was adequate, but a 3 speed would make it scream.   ::)  I put on my goggles as he kept talking, said "nice to meet you", and rode away.  It seemed like a conversation that was going to go nowhere...   ::)

Eamon
Title: Re: C5 Vs G5
Post by: 1 Thump on February 15, 2010, 09:46:41 pm
I recently had a guy come up to me as I was getting ready to fire up my bike.  He said "Dude, you should get a 3 speed transmission - they're fast!"  I started to explain that gearing determines what rpm you'll be at for a given speed, but can't change your speed unless you're geared badly to begin with.  You need more power and/or less drag to go faster  He responded by starting to lecture me about his friend with a 3 speed whose bike was now "wicked fast" and that "torque is where speed comes from."  He said my 5 speed was adequate, but a 3 speed would make it scream.   ::)  I put on my goggles as he kept talking, said "nice to meet you", and rode away.  It seemed like a conversation that was going to go nowhere...   ::)

Eamon

I get the sarcasm in your story. I must also agree I am a newbie. And, If you read carefully, I am not talking of doing 100 mph on the bike, just 65, but with a lower stress on the engine, with a 20 inch sprocket.

The overdrive gear was just a theoretical question. 
Title: Re: C5 Vs G5
Post by: Anon on February 15, 2010, 10:22:32 pm
I get the sarcasm in your story. I must also agree I am a newbie. And, If you read carefully, I am not talking of doing 100 mph on the bike, just 65, but with a lower stress on the engine, with a 20 inch sprocket.

The overdrive gear was just a theoretical question. 

Sorry, I wasn't making fun of you at all and hope you didn't think I was.  I was just relating a story  that had an extreme example.  I do think that you need to have a little bit of a power boost along with the gear change in order to have it actually result in less engine stress (like switching to a freer flowing exhaust or a carb change, etc).  Guys like Ace and Vince can say better than me, but a gearing change without added power may lower rpms, but too big a change and it might result in more heat from the motor trying to make that speed with the lower gearing.

Eamon
Title: Re: C5 Vs G5
Post by: ace.cafe on February 15, 2010, 10:42:30 pm
65 mph will put a big smile on my face. I have put a short exhaust. A 30 mm carb, 20 tooth sprocket and a more open air filter (undetermined yet) are next on the list.

In theroy: The Electra can go to 65 mph easily, just not recommended for cruising at the speed because of the added stress on the engine. However, with a larger gear ratio, same (not more) speed can be achieved with less stress on the engine. Thats why they have these larger sprockets to begin with.  

This theory you stated is not correct.
That theory comes under the heading of "no free lunch".

A larger sprocket actually reduces the torque-multiplier, and places more load on the engine at all speeds. The result is more load on the clutch when starting off from a stop, slower acceleration, and wider throttle openings at all road speeds to increase the engine output to make up for the reduction in torque multiplier of the gearing.
Top speed will not be higher, and may likely even be lower because of "over-gearing".
The "cruising rpm" may be a few hundred rpm lower, but the load on the engine is as high, or higher, than with the smaller sprocket, due to loss of torque multiplier in the gear train.

What you have stated here is a very common misconception. I don't fault you for it. Most people don't understand it. It stems from a lack of understanding of the load dynamics involved. Hopefully, you grasped some of what I wrote above.

However, the Electra can cruise at 65mph, but that's about its limit for long term cruising.
It already comes with an 18T sprocket, which is plenty.
It can do what you want, just barely. The larger sprocket isn't going to be "easier on the engine" despite the common misunderstanding about it.

They make larger sprockets for modified engines with higher output levels  to reach higher speeds. They are commonly used for the purpose you specify, but they do not do what people commonly think they do. They trade off a slightly lower rpm for a slightly larger throttle opening. It still takes the same hp to ride at that speed. The result is that the engine is not under any less load,  must put out at least the same output, and it isn't any easier on the engine. The slightly less friction losses from the slightly lower rpms is offset by the higher heat output from the larger throttle opening.

It might be a litte easier on the rider, because it's less buzzy at a little lower  rpm.
But the engine and the rider are two entirely different things.

The best way to increase cruising speed, or reduce the stress on the engine at the cruising speeds is to reduce the load the bike must overcome to maintain that speed.
And that is done by improving aerodynamics, to reduce wind drag, which is the largest factor of load that the engine must use its power to overcome at those kinds of road speeds.
If you do that, then you truly do have less load, and can then use a taller gear without increasing the stress of the engine, because there's less load to overcome, and the bike can accomplish that at a lower engine rpm more easily, thus you don't need to increase the throttle opening any bigger, and you can use that taller gear to get lower rpms at the same throttle opening as before or maybe even less, because you've cut the load by improving your aerodynamics.

If you want the math, here it is.
(Torque x rpm)/5252 = horsepower.
Lower your rpm, less hp.
.
It takes a certain amount of hp to overcome the resistance loads at speed.
If you lower rpm, you lower hp.
How do you increase the hp back to overcome the load to do that speed?
Increase torque by opening the throttle more.
That's the answer.
Title: Re: C5 Vs G5
Post by: jayprashanth on February 16, 2010, 07:04:18 am
Terrific explanation there, Ace.

Cheers,

Jay
Title: Re: C5 Vs G5
Post by: 1 Thump on February 18, 2010, 06:52:05 pm
The best way to increase cruising speed, or reduce the stress on the engine at the cruising speeds is to reduce the load the bike must overcome to maintain that speed.
And that is done by improving aerodynamics, to reduce wind drag, which is the largest factor of load that the engine must use its power to overcome at those kinds of road speeds.
If you do that, then you truly do have less load, and can then use a taller gear without increasing the stress of the engine, because there's less load to overcome, and the bike can accomplish that at a lower engine rpm more easily, thus you don't need to increase the throttle opening any bigger, and you can use that taller gear to get lower rpms at the same throttle opening as before or maybe even less, because you've cut the load by improving your aerodynamics.


On a low calorie diet and back to the gym. Reduce weight = Less stress on engine; Better shape = Less drag .

 ;)
Title: Re: C5 Vs G5
Post by: Ice on February 20, 2010, 04:41:53 am
Perhaps one of our resident math wizards can prove or disprove this old time wives tale,,

"Every seven pounds you shave of the bike and rider combo is equal to a one HP increase."
Title: Re: C5 Vs G5
Post by: motomataya on February 20, 2010, 03:50:08 pm
It seems to me to be to complex to put a number on. Weight is a detriment on take off, acceleration and hills. Top speed and cruising speed are more about aerodynamics. Of course if you big person your heavy and punch a big hole.
Title: Re: C5 Vs G5
Post by: ace.cafe on February 20, 2010, 04:15:14 pm
Perhaps one of our resident math wizards can prove or disprove this old time wives tale,,

"Every seven pounds you shave of the bike and rider combo is equal to a one HP increase."

This result would be based on a simple power to weight formula.

Let's look at the UCE for example.
The basic bike is about 400 pounds, and let's say we have a 200 pound rider.
That's 600 pounds.
At our latest dyno rating of the UCE, it had about 21 hp at the rear wheel.
That makes this combo have 28.57 pounds for every hp.
You'd need to drop 28.57 pounds off, to gain the equivalent of 1hp on this bike/rider combo.

If you had a fast bike that had 7 pounds for every hp, then if you dropped 7 pounds off, it would equate to about 1 hp. Such a combo might be a 400 pound bike and 230 pound rider, yielding 630 pounds total, and having rwhp of 90hp.
7 pounds for each hp in that case, and the "old wives tale" calculation would hold in that case.
So, it's all related to the power to weight ratio of the bike.

Now, as motomataya mentions above, there are other factors regarding what effects this power to weight situation will have. And he correctly points out that it is most effective in acceleration and hills, but has  less effects on top speeds because of aerodynamics taking a substantial part in the loads at higher speeds.
Title: Re: C5 Vs G5
Post by: Ice on February 20, 2010, 04:56:07 pm
Thank you gentleman.