Steering geometry questions: Changes to WR in'00?

[Chaindrive]

Off-set...Rake...Trail...?

In '00, something was changed to make the WR/YZ corner tighter. I believe it had to do with the "off-set". Here is my (mis)understanding ? of motorcycle steering geometry, would someone please confirm or set me straight?:

Off-set > If you drew a line across the centerline of the fork caps and then drew a second parallel line across the centerline of the steering stem and then measured the distance between those lines, that is the amount of off-set?

Rake > Like a Harley chopper has lots of "rake"? Is this accomplished by changing the angle of the steering head on the frame or by boring the steering stem holes in the clamps perpendicular, then boring the fork tube holes at a greater angle or some of each?

Trail > If you drew a line straight down the centerline of the fork tubes to the ground, then measured the distance to the center of the tire's contact patch, that is "trail"?

Exactly what did Yamaha change between '99 and '00? Was it just the clamps? Or did they change the angle of the steering head on the frame, too?

If I were to install stock '99 clamps onto an '01 frame, would I end up with '99, '01, or something in between steering geometry?

Should I be looking for a set of '00 or newer clamps?

Thanks in advance!!

[BrandonW]

Hey Chaindrive,

You asked a bunch of good questions there, and I will leave the answers for those who know what they are talking about. I will say that I have a '98 WR, and I bought a '01 top-triple clamp, and it changed my off-set. The handlebars were about 10 mm further towards the front of the bike. I am a taller guy, so I was ok with that, but I had to buy a new bar clamp so my Scott's damper would still fit.

Don't know if I answered any of your ?'s, but I do know that the top triple clamps are different.

Peace out!

[Superbike]

You cant change the offset with out changing both clamps. You just moved the bar position. --Mike

[Hick]

BrandonW,

I didn't think Yamaha has ever changed the offset, are you sure your '98 clamps have less offset than the '01 clamps?? I'm sorta confused by your post because you mention the bar clamps being moved, I believe by 10 mm, they did this in '00. Was the offset different also??

Trail > If you drew a line straight down the centerline of the fork tubes to the ground, then measured the distance to the center of the tire's contact patch, that is "trail"?

Replace "fork tubes" with "steering tube or steering axis" above and that is trail. So offset will affect trail, which is why it affects handling.

I believe the geometry change you are thinking of is the change in wheelbase from '98 to '99 (I think). They shortened the frame just behind the steering tube. There might have been some changes to shock linkage and swingarm that affected the handling but other than that this is all I'm aware of.

Hope this helps. ?

[BrandonW]

Glad I did not try to answer any of his questions. ?

I only changed the top-clamp, so I guess that rules out off-set change. I do know that my bars were further forward, so that must merely be the bar position risers off the top clamp.

I stripped out the bolt holes that clamp my handlebars down (Tried sticking a short piece of rubber inbetween the bars and the clamps to reduce vibrations) and I bought the new top clamp on eBay for $5.00. Got it, tried mounting it, and the Scotts link arm would no longer reach the tower. So, I had to order a new bar clamp. I was guessing that it was a YZ top clamp that I got.

So, Not the Off-Set, but it did move the bar position.

Hope I did not confuse...

[Chaindrive]

Brandon, Hick, Superbike: Thanks for the input. It seems odd that a change like Yamaha made did not receive more play. Maybe it had no noticeable effect on the bike's handling.

I am considering purchasing some aftermarket clamps which "correct" the '98-'99 to the same off-set specs as '00-up. I am also going to be "upgrading" (for other reasons) to an '01 frame. I would like better cornering manners but don't want to wind up with too much of a good thing or unhappy with an expensive set of clamps.

Normally, I would just hold-off on the purchase of new clamps and see how the '01 frame does with the '99 clamps, but it is one of those "move or lose it" deals on the clamps.

[YZ400Court]

In 00 Yamaha did cut 5mm from the frame. No angle changes were made, just pulled the front end in 5mm. Scotts used to make 5mm offset clamps for the older models (I have the set on my 98). And yes, the 00 and later top clamps will fit, but only change the bar position. If you want the bar even further forward you can go to a 250f top clamp and get another 13mm or so. If you are upgrading to an 01 frame there is no need for any more offset in the clamps.