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Sport Bike Tire Geometry 101 help please!

44K views 32 replies 15 participants last post by  eidian 
#1 ·
Okay, one thing that I've noticed on the Z1000 is that feels "weird" when I start to lean into a turn. I'm not saying that it feels "heavy" or that it feels unstable--it just feels weird. I read a review of the bike on the internet and the columnist said (direct quote from the article), "Initially, you notice a peculiar transitional sensation as the bike rolls over to the lean angle you’re demanding—perhaps because of an interaction between the very big (190-section) rear tire and the relatively small cross-section (120mm) front tire.". What exactly is he referring to? I totally agree with what he is saying, I just don't know how this is explained in terms of geometry/physics. From the first lean I ever made on the 500R I felt the bike and it seem to lean so easily--the Z1000, it's different. So what gives?

This ends word question 1 from Geometry 101.

A back story for my second question:

I was able to take a freeway off-ramp that I use every day to get to work on the Z1000 yesterday as fast as I wanted to because it was empty. It's a nice cambered, "gentle", 270 degree, uphill, right turn off ramp. When I could, I used to love taking the 500R on it going like 45 when it was empty (it was challenging)--just a little harmless fun before I step into the office. Well yesterday on the Z I took it easy and I was disappointed in myself because I got that "weird" feeling from question 1 and as a result I took the turn slow. The bike handled like it was rails but I just couldn't get myself to go faster and lean harder because I just don't know the bike yet. I estimated that I took the turn at about 25mph...when I was about to straighten out and take off, the speedometer read 45mph. "Huh!?" I thought..., "I must've twisted the throttle a little before I looked down". Well, I showed the bike to my co-worker/friend who rides also and he looked at the rear tire and asked, "What the hell are you doing!? Are you nuts!? You picked up the bike last night and you're already leaning it close to the edge!? Dude, you don't even have 80 miles on the bike--between not knowing the bike and the silicone that's still on the new tires, you're gonna low-side!". I said, "What are you talking about!?...Are you f-ing whacko!? The closest thing that even resembled anything that could be called 'leaning' was the dumb freeway off-ramp that I took earlier...but that was nothing special...". Then I looked at the tire, he was right...I wore off most of the nubs on the right side of the tire and the silicone was rubbed off to almost a consistent 3/8's to 1/2" from the edge. I didn't know what to say; I knew how far I was leaning on the 500R and the tire showed it. I worked that tire to the edge and I knew it because I've rubbed my boot on the ground accidentally because of it--not so with the Z, I can't tell crap. My conclusion is that I guess I did take the off-ramp going 45 mph and I was leaning over a lot more than I thought I was--I just couldn't feel it.

So here's question 2: do wider fat tires make leaning feel different than narrower tires? If you can use the 500R vs Z1000 comparison, that would be awesome.

That concludes question two and my inquiry about tire geometry. Thanks for reading and answering.
 
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#27 ·
I'll second the Woo hoo! Way to go. Have fun. :) I had the same experience when I first started riding the RT. I leaned way over, or at least what I thought was way over, and compared to my meanstreak it was leaned way over, but boy I had a lot of lean left. It just took time to develop confidence and trust in the bike and tires, and even more so, myself. To get to the point where I'm almost dragging my cylinders through a couple favorite off ramps. My riding buddy said I have about an inch left, which is close enough for me. ;-) I like to push to see what my limit is on the bike just so I know how far I can push it if needed when a corner tightens up, or I start to run wide etc. More lean is a good thing, we just have to be willing to use it.
+1.
 
#28 ·
I got to take the off-ramp at a decent speed this morning (as opposed to the crawl that traffic usually creates) and after taking in everyone's comments/advice, the bike is feeling better! I kept in mind everyone's comments about flatter/wider tires and especially bross's comment on how a half inch is still a "lonnnng way to go" and decided to trust the bike. At first I thought the bike was gonna "tip over" like ervins described so I gritted my teeth and told myself to "...use the Force..." and the bike found a sweet spot and just stayed there through the rest of the turn!

I think that I'll learn to just ride with the stock size tires because I like stability; sizing down and getting a higher profile might be a little too much for me. I love leaning in the twisties as much as the rest of you but my old age is telling me to go conservative.

Thanks for everyone's help!

One thing that I noticed when I first got my zzr 600. was how stable it was. Coming from the 500r I was really used to the lean angles and the speeds that I took corners while pushing it. The first weekend I had my zzr I had the chance to meet Ervins (great guy by the way) and as I followed him on the road I realized that the feeling of confidence (or the feeling that I could go to a bigger lean angle) was not caused by the bigger tires but by the bike and it's suspension.

The ex 500/500r are great bikes they really are! but one must not forget what they are designed to do. They are budget bikes, entry level bikes, and as I said they do a superb job at that! The z1000 (although I have not ridden it) I m sure it is quite comparable to the zzr 600 in that the suspension is much much better and much newer technology, and the chasis is designed for peak performance. That feeling that you have of not going fast, or not going as fast as you think is because of the suspension.

Slow down for a few hundred miles, and then have the suspension set up for your weight and riding style. Then it will feel like a dream! and I am quite confident that the squirrely/weird feeling will go away then.

Just remeber it is winter and the roads are more slippery!
 
#29 ·
One thing that I noticed when I first got my zzr 600. was how stable it was. Coming from the 500r I was really used to the lean angles and the speeds that I took corners while pushing it. The first weekend I had my zzr I had the chance to meet Ervins (great guy by the way) and as I followed him on the road I realized that the feeling of confidence (or the feeling that I could go to a bigger lean angle) was not caused by the bigger tires but by the bike and it's suspension.

The ex 500/500r are great bikes they really are! but one must not forget what they are designed to do. They are budget bikes, entry level bikes, and as I said they do a superb job at that! The z1000 (although I have not ridden it) I m sure it is quite comparable to the zzr 600 in that the suspension is much much better and much newer technology, and the chasis is designed for peak performance. That feeling that you have of not going fast, or not going as fast as you think is because of the suspension.

Slow down for a few hundred miles, and then have the suspension set up for your weight and riding style. Then it will feel like a dream! and I am quite confident that the squirrely/weird feeling will go away then.

Just remeber it is winter and the roads are more slippery!
Thmaster hit it on the nail...Suspension is soooo important. I had Penske rear shocks and LE re-engineered forks on my 636 and it was awesome...Seriously RIDING ON RAILS. Three important things to faster speeds in turns:

Tires
Brakes
Suspension

All well worth it. All I have left to do is the suspension for the 10R and I will be set. That is next year though.
 
#31 ·
I want to know what you were running for pressures - how much you weigh (personal i know) and how far if any your suspension settings were from stock. Also, how much chicken strip was left on the edge? Not being sarchastic - just want to see if there's a problem that could creep up and bite you no matter what tire you have on.
 
#32 ·
m\?]?factors.

Weight distribution of engine placement in the frame.
Rake and trail.
Triple clamp offset, front fork width.
Wheelbase, wheel diameter,front and rear.

I try to focus on what has shown to work. Like the XR750 HD frame set up.
19 inch front AND rear 31º rake, 4.5 trail, steering neck weldment design.
56 inch wheelbase.

Suzuki has the steepest rake like 23º-25º - a steering damper is mandatory.

One of the best rides i have had was a Ossa TT special designed by Sick (change the s to a D and you will have his first name) Mann. Unfortunately I did not know the rake angle. But I can tell you it was perfect. Absolutely confidence inspiring. You felt in complete control.

Sorry but this computer program would not let me type his real first name.
 
#33 ·
I want to know what you were running for pressures - how much you weigh (personal i know) and how far if any your suspension settings were from stock. Also, how much chicken strip was left on the edge? Not being sarchastic - just want to see if there's a problem that could creep up and bite you no matter what tire you have on.
Well, since I've switched to Conti Road Attacks (180/55 rear from the stock 190/55) and adjusted the fr & rr rebound to 80% stiff, the bike has been perfect. I'm 186 lbs. and with the Conti's I've been running them at 32 lbs. for the front and 36 lbs. for the rear with great results. Here is a pic of the chicken strip after I took the Conti's through the twisties for the first time (I was suprised to see that the date-of-manufacture was chewed-up):

 
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