TOPIC:

Xl ED wrote: Looks pretty good. Where are you going for track days? Cayuga,shannonville?

TMP, Cayuga on May 9th. Maybe Shannonville later in the summer.

loudhvx wrote: Looks good. Using those forks brings the wheel center in line with the fork axis, but the original geometry was designed to have leading axle forks. I think that means more trail (but shorter wheel base). They were pretty twitchy stock. I use a fork brace and a steering damper to reduce the squirrel factor. Any plans to change the steering angle?

Drooz wrote: I'm not sure what this change in geometry will have on the handling. I don't have any plans to change the steering angle at the moment.

Have you given any more thought to the changes in steering geometry. Just to add a bit more to the conversation, by changing the forks to a center-axis style axle as opposed to leading axle, you've reduced the trail. For a given frame, the amount of trail is determined by the axle position on the fork, the diameter of the tire, and the triple clamp offset (the offset between the fork tubes and the pivot bolt).

The stock triple clamps were designed to be used with the leading axle, so they will have very little offset between the pivot and fork tube. If you were to compare the triples from the new forks with the 550 clamps. the different should be very obvious.

How this will impact handling is beyond my expertise, but here are some numbers. The kz1000 has 90mm of trail. Moving the axle back as you did may reduce the trail by maybe an inch or so, say 25mm. If the stock 550 trail is similar to the 1000, this 25mm would be a reduction of about 25%. This seems like it could be significant. The 78 Z1R has 85mm of trail vs. 90mm for the KZ1000. Many sources have commented that this 5mm reduction negatively impacted the Z1R handling.

My impression is that trail changes both how twitchy the bike is (less trail = more twitchy), and how much steering effort is required. If you plan to use clip-ons, somewhat less trail might be nice since you have narrower bars and less leverage. But it may have other handling impacts that I'm not aware of.

Here is a random page talking bout trial: www.seegercycle.com/Rake-and-Trail.aspx

You can adjust the trail, while still using the forks you have, by using a different set of triple clamps. If the clamps that were originally used for the new forks fit into your steering head, that would be one option. Another would be to make custom triple clamps.

dohc wrote: ...you've reduced the trail.

Wait, wait, I think I was confused. I believe loudvhx's comment is correct, in that moving the axle back increases trail.

I still think my other comments stand, but the steering effort would increase with more trail...

dohc wrote:
Have you given any more thought to the changes in steering geometry.

Hey dohc, welcome to the discussion!

In brief, the answer is no, not really. This 550 is a real "budget experiment" so there isn't much room for custom triples or other significant (read, costly!) mods. I have no doubt that the changes to the bike will affect the steering, but not having ridden the bike prior to the modifications, I'll have no way of knowing exactly how different it will feel.

The different forks will certainly change the trail and should make the steering quicker. The smaller 18" wheel will likely add to that. The 'slower', stickier tire will probably offset that some, so where does that leave me? I'm not sure! I guess I'll find out on the 9th of May.

Be sure of this, I'll be taking it pretty easy for a few laps. I'm running superbike bars so leverage will be good, as will my comfort level. We're still working with ride height (rear shock length and fork height in the triples) so that will affect the overall handling as well.

I like a responsive bike! My h2 Triple has had extensive modifications to quicken the steering and sharpen the handling. It works great! I'll take the 550 for it's "shake down" run and let you all know how it turned out! BTW, the track I'm headed to is relatively short, smooth and flat, 11 turns with 2 short straights. A really good place to ride it for the first time.

dohc wrote:

dohc wrote: ...you've reduced the trail.

Wait, wait, I think I was confused. I believe loudvhx's comment is correct, in that moving the axle back increases trail.

I still think my other comments stand, but the steering effort would increase with more trail...

Haha! Ya, you're right! I was thinking the same as you!

The change in forks should increase the trail, not decrease it! The other alterations are as previously stated.

In the end, I think the changes should balance themselves out, but we won't know for certain until May 9th!

Yes, it increases the trail as trail is defined. But I really can't say if it will handle slower or faster overall. All else being equal, more trail should handle slower, but all else is not equal. The wheel base is now shorter.

In case I didn't mention it earlier, the short wheel base of the 81 gpz550 (all later years were longer), had a tendency for the front fender to come into contact with the oil cooler in very extreme stops, especially if the stop is with some bumps. But I assume you will really stiffen the front springs, so hopefully that will offset the clearance lost now that the front wheel is closer to the frame.

I think it will be one of those try it and see what happens... but be careful! Steering damper and fork brace have saved my bacon more than once on that twitchy gpz. And, of course, get all the advice you can from someone riding the same/similar bike on the track, like Corey!

loudhvx wrote: Yes, it increases the trail as trail is defined. But I really can't say if it will handle slower or faster overall. All else being equal, more trail should handle slower, but all else is not equal. The wheel base is now shorter.

In case I didn't mention it earlier, the short wheel base of the 81 gpz550 (all later years were longer), had a tendency for the front fender to come into contact with the oil cooler in very extreme stops, especially if the stop is with some bumps. But I assume you will really stiffen the front springs, so hopefully that will offset the clearance lost now that the front wheel is closer to the frame.

I think it will be one of those try it and see what happens... but be careful! Steering damper and fork brace have saved my bacon more than once on that twitchy gpz. And, of course, get all the advice you can from someone riding the same/similar bike on the track, like Corey!

Yessir, great advice and info as always!

The forks and rear suspension are a fair bit stiffer than stock and there isn't an oil cooler on this model, so no worries damaging that at least.

One week from tomorrow and I'll have some solid info on how it all worked out.

Not that you can do it before track day, but you can add an oil cooler easily by swapping the oil pan with a gpz model. The 81 D1 gpz oil pan should fit without a problem, but I can't remember if the later ones do as well. It's something you may want to consider down the road to keep the motor a little cooler.

Things are quickly coming together. More parts have arrived:

Final assembly by Thursday. Shakedown Saturday at Toronto Motorsports Park.

Should be lots of pics from Saturday.

Drooz wrote: Well, their both 550 pipes. I think I figured out the difference. Feel free to correct me if I'm wrong.

Pipe 1 is the "street" version, to accommodate the retention of the centre stand.

Pipe 2 is the "race" version, no centre stand.

That's correct. That is what I was trying to explain in one of my other posts in this thread about the "race" version pipe. We have the second (rusty) version on our 550. Fits well. I like that Yosh pipe!!! Looking good so far. Hope you get it together for the track day.

BlackZ1R wrote:

Drooz wrote: Well, their both 550 pipes. I think I figured out the difference. Feel free to correct me if I'm wrong.

Pipe 1 is the "street" version, to accommodate the retention of the centre stand.

Pipe 2 is the "race" version, no centre stand.

That's correct. That is what I was trying to explain in one of my other posts in this thread about the "race" version pipe. We have the second (rusty) version on our 550. Fits well. I like that Yosh pipe!!! Looking good so far. Hope you get it together for the track day.

Yessir! My next project is to get that Kerker "race" header fixed if possible. The Yosh pipe fits, but if I get "up to speed", ground clearance might be a problem on the right side.

We'll be at the track on Saturday! I hope the rain in the forecast doesn't show!

Well, got 'er bolted together.

Just a few more details and tidying up to do and we're ready so see if it's going to be "fun" or a "nightmare" on Saturday. (I'm betting on "fun"!)