Streetfighter front end dive?

[Squiggles]

Right, this could be a brake or a suspension thing, i couldnt really put it down as one...

Went to check out a streetfightered 87' GSXR750 that a mate is looking at purchasing, its may be a bit lowered in the rear it seems as the sidestand puts it nearly vertical when its down, has mx bars and stock forks, giving it an upright riding position. 18" wheel on the front, 17" on the rear

And heres my description of what i felt

Cruising along at 50 and i start to brake, but the front feels light, like its not really gripping, and the forks are barely diving... i felt like i couldnt brake quickly without sliding the front, resulting in it taking quite a long time to slow down.
However, in the last few metres of braking before coming to a stop i put a bit of weight foward and braked harder and then the forks started to dive a bit (like forks normally dive)

My question, what has actually changed here with this bike?? Do i get this feeling because the front has less weight on it than it did when the bike was stock and that when just riding, the suspension isnt at its err... normal travel? but it reaches this then dives normally under braking....

Not much of a description, but i'd be interested to know peoples thoughts on this and the effect streetfightering has on suspension in general and ways in which such ill effects can be corrected.

[Sketchy_Racer]

the 18" on the front with the small wheel on the back is screwing with the steering geometry.

with the bigger wheel on the front it will raise the front and rake it out giving the odd feeling you have. Or could be a whole bunch of stuff.

[Zapf]

my guess would be the front is harder than the really soft rear. Because the rear is soft, it is not pushing the front down on the road and hence it is not following the surfaces and hence feel like it has no traction.

Because the rear has been doing all the work for so long, it could be a bit tired too.

[TDC]

Right, this could be a brake or a suspension thing, i couldnt really put it down as one...

Went to check out a streetfightered 87' GSXR750 that a mate is looking at purchasing, its may be a bit lowered in the rear it seems as the sidestand puts it nearly vertical when its down, has mx bars and stock forks, giving it an upright riding position. 18" wheel on the front, 17" on the rear

And heres my description of what i felt

Cruising along at 50 and i start to brake, but the front feels light, like its not really gripping, and the forks are barely diving... i felt like i couldnt brake quickly without sliding the front, resulting in it taking quite a long time to slow down.
However, in the last few metres of braking before coming to a stop i put a bit of weight foward and braked harder and then the forks started to dive a bit (like forks normally dive)

My question, what has actually changed here with this bike?? Do i get this feeling because the front has less weight on it than it did when the bike was stock and that when just riding, the suspension isnt at its err... normal travel? but it reaches this then dives normally under braking....

Not much of a description, but i'd be interested to know peoples thoughts on this and the effect streetfightering has on suspension in general and ways in which such ill effects can be corrected.

It sounds like a matter of weight transfer, or should I say lack there of.

When you start to brake there needs to be some weight transfer forward as traction is ultimately a result of the amount of load on the tyre. I'm sure I have explained that badly, ummm, Imagine a piece of cardboard on the floor, grab it and drag it across the floor its easy, get somebody to stand on it, not so easy. What is going on here is the increase in load is making traction.

If the springs / geometry / damper rates resist initial dive there is not enough weight transfer to build enough traction, so you keep braking until the front finally starts to deflect, then you can finally get in to the brakes and stop the thing. From your description if you did a panic stop the wheel would likely lock.

The symptom is quite obvious from you good description of your experience, however the cause will very possibly be not so easy to diagnose. While these street fighters might look very cool to some tastes often the net result is somewhat unpredictable in the real world. It would be nice if the builders of these machines put as much effort in to the dynamics of the machine as they do with the cosmetics etc......

If your friend has his heart set on this machine keep some money aside for a competent suspension technician to make it work as it should.

[Robert Taylor]

It sounds like a matter of weight transfer, or should I say lack there of.

When you start to brake there needs to be some weight transfer forward as traction is ultimately a result of the amount of load on the tyre. I'm sure I have explained that badly, ummm, Imagine a piece of cardboard on the floor, grab it and drag it across the floor its easy, get somebody to stand on it, not so easy. What is going on here is the increase in load is making traction.

If the springs / geometry / damper rates resist initial dive there is not enough weight transfer to build enough traction, so you keep braking until the front finally starts to deflect, then you can finally get in to the brakes and stop the thing. From your description if you did a panic stop the wheel would likely lock.

The symptom is quite obvious from you good description of your experience, however the cause will very possibly be not so easy to diagnose. While these street fighters might look very cool to some tastes often the net result is somewhat unpredictable in the real world. It would be nice if the builders of these machines put as much effort in to the dynamics of the machine as they do with the cosmetics etc......

If your friend has his heart set on this machine keep some money aside for a competent suspension technician to make it work as it should.

I concur entirely with what has been stated here, and emphasising that the geometry is all messed up with not enough loading on the front.

There is a comparison to choppers here, they make them look nice ( and thats a matter of taste ) but they most often have the handling prowess of a supermarket trolley.

[HenryDorsetCase]

Oh, and I felt the effect described above (and locked my front wheel at about 80kph) in my race training day on Saturday.

The drill was practising race braking: So, pick your marker, then squeeze the front brake, increasing lever pressure as the weight transfers forward, and grip the tank with your knees.

I did the classic thing of going along and just grabbing a big bunch of brake which locked the wheel because the tyre had no load other than weight distribution on it. The difference in feel, speed (of deceleration) and comfort under hard braking was amazing.