Tire height change..suspension change?

[dcc5266]

Got a 160/60 dunlop qualifier on a post rim. Height difference between old rear, 140/80 or 150/70, and qualifier 160/60 is about 1 inch. So, the dunlop is shorter in the rear than O.E. spec. & Front tire overall dimmension is same O.E. spec. Should I lower the front to compensate for rear tire height difference?

[md86]

In theory , maybe . But really , it's gonna kinda end up being whether or not YOU notice a difference , and if you wanna do something about it . If it feels funny , and not in a good way , fix it . If it feels fine , than it likely is , to YOU . Once you start pushing things to the point where you notice things feeling funny when they hadn't BEFORE , THEN ..... See where this is going ?

[JokerZwild]

I upped to a Avon 160 & wound up lowering the front about an inch or so to suit my tastes. But every rider is different that way. Try it first you may never even notice the difference.

[GregS]

The difference in tire height is about 1/2 inch with the 150/70 and, as you said, a little more than an inch with the 140/80 compared to a 160/60.
If you raise the rear and "lower" the front, you would quicken the steering by making the fork angle more vertical. Did you mean raise the front? If so, you would significantly increase height of the bike. If your tall that might not be an issue. Also I'm not sure on your pre if you could slide the forks down in the triples very much with the bars needing to clamp on to the tubes. And if you raise the front you would restore the rake but the center of gravity would be higher and possibly make the bike "feel" sluggish to lean and stand back up when cornering.

[dcc5266]

The difference in tire height is about 1/2 inch with the 150/70 and, as you said, a little more than an inch with the 140/80 compared to a 160/60.
If you raise the rear and "lower" the front, you would quicken the steering by making the fork angle more vertical. Did you mean raise the front? If so, you would significantly increase height of the bike. If your tall that might not be an issue. Also I'm not sure on your pre if you could slide the forks down in the triples very much with the bars needing to clamp on to the tubes. And if you raise the front you would restore the rake but the center of gravity would be higher and possibly make the bike "feel" sluggish to lean and stand back up when cornering.

With my bike now sitting 1 inch lower in the back because of the 160/60, it has increased the rake. Right? Right. Therefore, the bikes front is now 1 inch above the rear, increasing the angle of the bike from front to back. Should I drop the triple tree to compensate for the increased angle.

Most sport bikes like gsxr's, R6's, etc. benefit from lowering the front just a tad for cornering. Lowering my kat an inch would only put the bike back at the factory spec. angle. Right? I use this bike for hitting the twisties, so I need the best setup that I can get for a katana. The handle bars will not be a problem on a pre to lower, the forks just slide thru.

I'm only about 5'9" tall and about a buck fifty soakin' wet. Can someone shed some light on me?

[JokerZwild]

If you look at the trees on my bike I removed the stock bar risers and added a set of vortex clip-ons allowing me to slide the forks up about 1.5 inches lowering the front end. Yes it made steering more sharp and also assisted in keeping the front end down far better on hard launches! My point is that all riders are looking for "THERE" ideal set up. Trial and error are the only ways your gonna find it! Just be sure that the bike is safe b-4 pushing your settings to the limits. (i.e. Trees are straight and square with no off tracking of the wheels.) Putting on a good set of tires was the best thing I coulda done for my bike. The handling improved 10 fold with that one purchase. How ever it did require a few lil tweaks to maximize the performance once the grip was established. we can all sit here and argue that "our" mods are the best but what it really comes down to is your particular riding styles and prefs. Best of luck with your bike I hope you nail the set up and letter rip!

[dcc5266]

Thanks JokerZ! I appreciate it. I will work on it and try to repost sometime to let everyone know what I found out. What kind of results has everyone else seen? Track and street.

[JokerZwild]

Your more then welcome! All I care about is that you have the common sense to do the right thing and stay alive. Sooooo many dont. Hence the fact that its not the strongest that survive ...but the ones who have the best common sense!!!!!!!

[thetable]

Alright we are talking about less than 2/3 of an inch. I would be very surprised if you can tell the difference there on anything short of a buell I would be very impressed.

[dcc5266]

2/3 of an inch across 2 feet of forks can be a big difference depending on how you ride. Plus, it will probably come out to be more than that depending on how aggressive you are in the corners. I just need some feedback from people that have set this type of suspensions on the SAME bike as mine. Anyone?

[JokerZwild]

Sometimes a bike is like a woman....every inch counts!

[tone]

How are you calculating the differance in tyre height
Has someone actually measured the differance or are they just very poor calculations

I'm thinking on this & have done my own sums but cannot come up with a differance of anywhere nead an inch, please educate

[thetable]

How are you calculating the differance in tyre height
Has someone actually measured the differance or are they just very poor calculations

I'm thinking on this & have done my own sums but cannot come up with a differance of anywhere nead an inch, please educate

I calculated mine based on sidewalk height. 140 x .8 = 112; 160 x .6 = 96. And I'm with you on less than an inch.

@dcc dude your way overthinking the whole thing. The tuna has a really relaxed head angle to begin with. I went from a 150/70 to a 160/60 and noticed no I'll effects. Now on the buell an inch is the difference between death wobble and stupid thing only goes straight.

[dcc5266]

How are you calculating the differance in tyre height
Has someone actually measured the differance or are they just very poor calculations

I'm thinking on this & have done my own sums but cannot come up with a differance of anywhere nead an inch, please educate

First things first..... we are talking about overall diameter. Check these specs for the 160/60..

http://www.dunlopmotorcycle.com/tirecatalog_tire.asp?id=92

This on my bike now. So, Dia. would be 24.86 inches.

Now, this is what the bike was originally equipped with...

Bridgestone 140/80. Check these specs for bridgestone's..

http://www.motorcycle-karttires.com/glamourindex.aspx?productID=3

Dia. would be 25.8 inches.

Therefore 25.8 - 24.86 = 1 inch less in overall diameter. However, the bike is only affected by the difference in Radius, so it would be 1/2 of the difference in overall diameter. So the bike is really only affected by .5" in the rear. Lowering the front by one inch would put the bike .5" lower than factory angle, which would decrease the rake angle and increase responsiveness.

I hope that helps!

[thetable]

Overall height means nothing, half the overall height is what affects the axle height and that is all that can affect geometry.