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Discussion Starter #1
Has anyone done a front end swap from a GPZ 500 with the dual disc front brakes? I know it may be difficult to find one but it seems it would be worth it. The search function didn't turn anything up if I missed it link me to it.
 

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Well it's not worth it GPZ don't stop any better that EX and the front is heaver. Get a EBC FLoating disc and HH sintered pads for a brake that will scare you.

FOG
 

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Discussion Starter #3
Heavier just because of the extra hardware or are the fork tubes a different size or some other reason? Do you have any experience with the GPZ's? Are the brakes the same brand/ equipment as the EX just doubled or are they of a lower quality. I would like to have the confidence and stopping power of a dual disc set up on the EX but I know from working on older bikes newer/bigger doesn't always mean better.

I'll check out the floating disc and HH pads for now and add them to the winter list. Thanks
 

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The GPZs have two discs but they are smaller. Alie sama Tinga.
Condfidence comes from skill, not 2 brake discs.

FOG

fog
 

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FOG said:
Condfidence comes from skill, not 2 brake discs.
snap snap snap
 

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I went down this path and after looking at the coast and having a word with Fog scraped the idea far to much money for very little gain. Change your rotor and fit some sintered pad and spend the rest of the money on up grading you suspension so it can cope better with your better brakes.
 

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Discussion Starter #7
::)

Armchair philosophy.

There is a reason almost every modern sportbike has dual disc brakes up front. The GPZ has the same size brakes as the EX just doubled. 280mm rotors with dual-pistons hydraulic brakes. 36mm fork tubes which is the same as the same year ex and smaller than the 2 gen which have 37mm.

How are they smaller and heavier, short of the weight of the other calipers, rotors and mounts?

The GPZ front forks have more suspension travel than the EX too.

What then is the reasoning behind not using it?
 
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TSwami said:
::)

Armchair philosophy.
::)

Noob.

You're talking to people who have pushed this bike far harder than you will ever be capable of doing so. FOG won championships on his EX500 and knows the bike inside out, probably better than the engineers who designed it. I did some trackdays in the Intermediate group on mine, with the floating rotor conversion, before switching to an SV650.

TSwami said:
There is a reason almost every modern sportbike has dual disc brakes up front.
Sure, there's a reason. Do you know it? Do you know why the EX doesn't?

TSwami said:
The GPZ has the same size brakes as the EX just doubled. 280mm rotors with dual-pistons hydraulic brakes.
Provide a link to the specs that show this.

TSwami said:
36mm fork tubes which is the same as the same year ex and smaller than the 2 gen which have 37mm.
TSwami said:
How are they smaller and heavier, short of the weight of the other calipers, rotors and mounts?
The weight of the other calipers, rotors, and mounts adds... weight. :p

TSwami said:
The GPZ front forks have more suspension travel than the EX too.
Prove it.

TSwami said:
What then is the reasoning behind not using it?
Single works fine with proper brake pads and a floating rotor. Dual is just for aesthetics on this bike.
 

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Discussion Starter #9
Your childishness is only matched by your incompetence.

I have no desire to push it to the limits, its a 500, it's not my track bike. I know FOG knows what he is doing, that is why I want to have a technical discussion about replacing the front end and get some real reasons why not to do it, not listen to you try and sound cool.

The specs are here for a 2003 GPZ http://www.motorcyclespecs.co.za/model/kawasaki/kawasaki_gpz500s 03.htm.
One correction to what I said earlier would be that the forks of 2003 on the EX are 37 which are bigger than the same year GPZ.

The weight is implied, but you are gaining something in return to compensate. I was asking more in regards to superfluous items that may be on the GPZ and not on the EX that affects the weight. As you can see from the specs the GPZ has 160mm of front suspension travel as opposed to the 130mm of the EX. FOG, do you know why this is? I didn't see tube length or spring size. I have no experience with the GPZ at all but I will keep looking.

Aesthetics? Really? I'm sure thats exactly what the engineers are thinking when the put dual discs on.

So lets get back to the task at hand, we'll see what light FOG can shine on this
 

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Well all the technical spec aside the real reason the euro version has dual discs is wait for it Sales.
The euro riders are admadant that a "real " sportbike have dual discs.
Thats about it. As I said before there is no real advantage to them. The unsprung weight penalty more than cancles out any brake preformance gain.

FAct is the way to go fast on an EX is to stay off the brakes. When I was novice I was burnning through pads in a single race weekend. When I finished up my career a set of HH pads would last me all season.

FOG
 

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Did you run through the track pretty much without braking since you were comfortable taking corners faster? Or are the HH pads that much better/longer lasting?
 

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The pads may or may not have lasted longer , But the real reason was I learned to enter the corners faster and push the front tire to slow down. The EX has limited power to square off corners, so the way to go fast is high corner speed. This has limites of course but you can win races by passing going in to a corner a lot faster than trying to power out (High side city).

FOG
 

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Could you elaborate on this concept:
FOG said:
push the front tire to slow down.
?
 

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It's just what it sounds like. You must know that if you force a tire to turn, it slips sideways a bit . the harder you turn it the more it slips. you can use this "fact" to assist getting you MC around a corner. As the tire slips sideways. it also slows it's rotation or the bike , just as the brakes would.
Now everybody generates Slip angles (The wedge angle between where a tire is pointed and where it actually goes). You do ,your grandmother does. The diffrence is racers generate bigger ones, when a slip angle becomes visable ,it called a slide. NASCRAP drivers call the the slip angles loose ot tight. depending on whether the front or the read slips more.
So when a tire slips a lot sideways it become a sort of brake, got it? How neat is that ? you can turn and brake at the same time. The faster your going the harder you must turn the more braking force you get. GOT it? Do it too much and you low side.

FOG
 
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Forbin said:
Single works fine with proper brake pads and a floating rotor. Dual is just for aesthetics on this bike.
TSwami said:
Your childishness is only matched by your incompetence.

Aesthetics? Really? I'm sure thats exactly what the engineers are thinking when the put dual discs on.

So lets get back to the task at hand, we'll see what light FOG can shine on this
FOG said:
Well all the technical spec aside the real reason the euro version has dual discs is wait for it Sales.
The euro riders are admadant that a "real " sportbike have dual discs.
@TSwami: You can apologize at any time.
 

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Great info, thanks for asking and thanks for the great answers!!
 

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TSwami said:
::)

Armchair philosophy.

tThere is a reason almost every modern sportbike has dual disc brakes up fron. The GPZ has the same size brakes as the EX just doubled. 280mm rotors with dual-pistons hydraulic brakes. 36mm fork tubes which is the same as the same year ex and smaller than the 2 gen which have 37mm.

How are they smaller and heavier, short of the weight of the other calipers, rotors and mounts?

The GPZ front forks have more suspension travel than the EX too.

What then is the reasoning behind not using it?
Are you having a LAUGH Armchair philosophy i take changing things on my bike very seriously and would have changed to twin rotors if the had have been a gain but like i said in my post i had spoken to fog and took fog at his word your opinion has no weight against THE MASTER FOGS.
You said in your post (There is a reason almost every modern sportbike has dual disc brakes up front) you are right about this but the GPZ IS NOT A MODERN BIKE ?
 

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Buells with the ZTL front brake only run 1 rotor and handle fine.

Guys that run gsxr forks on ex250s removed one of the rotors/calipers to save weight because they get plenty of power from the one that's left.

Have you ever ( in normal road driving conditions ) squeezed the front brake and worried that you wouldn't stop in time? If so you probably started braking too late and any extra stopping power would just throw you over the handlebars anyway.

I've looked at every crazy idea swap-wise for the ex500. I have a cbr rear end in my basement that I could put on but it weighs as much as the stock rear if not heavier. Same with front ends. At this point I'm just trying to go as light as possible, if I even continue with the project. I'm really tempted to switch to an older ex250 as a base and just work a super fuel efficient streetbike. The ex500 I have was pretty much free at this point due to an accident anyway, so it's fun to tinker with.

Anyway.

For aesthetics, yes 2 disks looks more balanced and appealing to the eye. It can also make the bike look more powerful cus "man it needs 2 disks to stop!"

Other than that only negatives.

Basic rule of thumb is "What FOG says goes" not because he's always right or a super hero, but because he had all these same crazy ideas and tested them or saw someone else test them with poor results or just thought it through longer. In the end that's all that matters.

Bob
 

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Bob wrote

"Basic rule of thumb is "What FOG says goes" not because he's always right or a super hero, but because he had all these same crazy ideas and tested them or saw someone else test them with poor results or just thought it through longer. In the end that's all that matters.

Bob"

Yep , at least a partial yep. I did attempt to build a super Modified bike from a EX I stripped every needles piece of metal even torched off the centerstand brackets. Put a Ninja 600 swing arm and 17" wheeland a duel disc 600 front end. Even cut off the seat strut and made a Monocot sheet metal seat.
The thing was a Complete beast . it would not handle worth a ****. The wheels out weighed the chassis by so much they could not be controlled. (too much un sprung weight) I finally gave up on it and sold it to, Rich Alexander. He couldn't ride it either.

Light is good but remember balance rules.

In bike deaign it's a simple matter to calculate the brake surface required. Bike massX velocity = swept area X CF of pad material =
Or simply the weight and speed of the ex does not require and more swept area of brake that one disc provides. If it ain't enoug ,you brake are not in proper condition. (Mostly true)

FOG
 

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Discussion Starter #20
That was all I was looking for.

If I understand the unsprung weight added will affect handling more than it can make up in stopping force. I've read on here that people have problems with the rear tire locking up, so it sounds like the front brakes are engineered to the point or past the traction of the front tire thus more braking power would exceed the traction and be useless. Can I ask this though, if you were racing this bike, which I am not and never will, would there not be a benefit to the heat dissipation you get from a dual disc? or is it too small of a gain?

My comment was directed to the statement that confidence comes from skill not 2 disk brakes. I don't argue with that but that doesn't tell me anything about why 1 is better than 2. I want to know the facts because this is the internet and anyone can say anything here. I take all of my bikes very seriously, thats why I want facts. I have done several front end swaps (even from a disc to drum :eek:) for the better and if you spend 5 minutes in vintage bike world you would hear all sorts of debates about disc vs drum and people giving all sorts of opinions when they don't know what they are talking about. FOG knows everything about these bikes so I was asking for some elaboration. I didn't give my "opinion" I gave facts from a spec sheet and asked for clarification.

Forbin- If you want to contribute something worthwhile and factual to the conversation be my guest but apologies will be witheld until then.
 
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