Switching from a 180 to a 190 rear on a 03 636

[kawlreaper]

Hey all -

I had an acquaintance who was selling his Dunlop take-off's pretty cheap. So me, being the poor person that I am, thought it was a chance to save a little cash bought a couple sets.

Well here's the issue. I am riding a 03 636 which used to have 180's on it. The tires that I bought are 190 60's..REALLY TALL. I had my front/rear suspension re-done with race-tech by a shop near me. I knew I had to adjust it for the tire but I didnt know by how much. WELL, I did a trackday at Summit Main and at full acceleration, I got a LOT of front end wobble. Id adjust my dampener but then I couldnt turn the bike..My suspension guy said that I don't have enough trail. So, we took 5mm off the spacer off the rear shock and tried that. It helped but I dont believe not enough. I went to NJMP - Lightning and at the straightaways, I could feel the wobble. Not even to mention I was a little hesitant to hit it...Im leaning forward a lot more to keep pressure on the front but why am I changing the whole bike around for the tire?

SO, here's what Im thinking. Go to a tire that's not as tall at the 60 profile. From what I am understanding, a lot of 600's are running 190-55's or 190-50's. Also, MAYBE getting a real rear shock (Penske ot Ohlins) and going that route.

Is anyone running into this same problem? WHy did I go to a 190? TO SAVE MONEY!! Any recommendations?

 

[Garrison]

Wanna spend money? Get the shock.
Most 600's run 180/55's and they're ideal. The 190/60 shouldn't be that much of a change since those two numbers are in fact a ratio.

 

[kawlreaper]

Garrison;89907 wrote: Wanna spend money? Get the shock.
Most 600's run 180/55's and they're ideal. The 190/60 shouldn't be that much of a change since those two numbers are in fact a ratio.

uh.....NO

Well...Slight or not..Its really screwing with my steering...Im probably just going back to a 180..

 

[dale.b]

Geometry. This is an easy fix. You can still run the 190/60, but you need to sort out the geometry to get rid of the wobble. Leaning forward on the bike won't help. Try removing a couple more mm from the rear until the wobble is gone.

180 x 55 = 99mm tire sidewall
190 x 60 = 114 tire sidewall

114-99= 15mm tire radius increase.

Here's what to do:
1 - Put the bike up on the rear stand. Measure from the rear axle vertically up to a fixed point on the tail. Record the measurement
2 - Put the 5mm shim back in. Measure again from the axle vertically up to the same point. Subtract the first measurement (step 1) from this one. Whats the difference in mm?
3 - You should now be able to calculate how much needs to be removed from the shock spacer. For example if removing 5mm lowered the ride height by 10mm, then you have a 2:1 ratio and 7.5mm would lower the rear by 15mm that the 190/60 tire added.

Of course you are now decreasing your swingarm angle, but that's better than having the front end wobble.

Even though the measurements are exact, the science is not, since every change you make has a ripple effect. In the end it is about how the bike feels with the changes.

 

[unclejesse]

If you do not want to buy a really expensive shock.. Just buy a spacer for your stock one to raise it up a little bit..

Are you planning on racing? then buy a better shock
You can not do much to stock suspension.

Make a few more adjustments to the font end..

How cheap are you? did you mount the front tire yourself without balancing it? Because that could cause front end shake.

 

[kawlreaper]

dale.b;89912 wrote: Geometry. This is an easy fix. You can still run the 190/60, but you need to sort out the geometry to get rid of the wobble. Leaning forward on the bike won't help. Try removing a couple more mm from the rear until the wobble is gone.

180 x 55 = 99mm tire sidewall
190 x 60 = 114 tire sidewall

114-99= 15mm tire radius increase.

Here's what to do:
1 - Put the bike up on the rear stand. Measure from the rear axle vertically up to a fixed point on the tail. Record the measurement
2 - Put the 5mm shim back in. Measure again from the axle vertically up to the same point. Subtract the first measurement (step 1) from this one. Whats the difference in mm?
3 - You should now be able to calculate how much needs to be removed from the shock spacer. For example if removing 5mm lowered the ride height by 10mm, then you have a 2:1 ratio and 7.5mm would lower the rear by 15mm that the 190/60 tire added.

Of course you are now decreasing your swingarm angle, but that's better than having the front end wobble.

Even though the measurements are exact, the science is not, since every change you make has a ripple effect. In the end it is about how the bike feels with the changes.
Thanks! Im on my last set of 190-60's. And it looks like most of the take off's im seeing are 190-55's. My trackdays are done for this year to see how it feels...I liked the way it dipped in before..Decisions Decisions..


unclejesse;89913 wrote: If you do not want to buy a really expensive shock.. Just buy a spacer for your stock one to raise it up a little bit..

Are you planning on racing? then buy a better shock
You can not do much to stock suspension.

Make a few more adjustments to the font end..

How cheap are you? did you mount the front tire yourself without balancing it? Because that could cause front end shake.

Im cheap but not that cheap. I had them balanced. I usually do track days but Im thinking about racing..A couple of guys are pushing me..

Im not bent on HAVING to use a 190...Just I thought Id save a little money. But If Im going to keep on messing with the response...Ill go back in a heartbeat!

 

[Meat]

What is the problem with just raising the front? I had a similar issue and raised the front but I don't think I raised it enough because I still had a good bit of instability. I just swapped wheels to a different set of tires but would like to know if raising the front (lowering the forks in the triple tree) would work as it is easier to mess with to me.

Thanks,

 

[kawlreaper]

Meat;89919 wrote: What is the problem with just raising the front? I had a similar issue and raised the front but I don't think I raised it enough because I still had a good bit of instability. I just swapped wheels to a different set of tires but would like to know if raising the front (lowering the forks in the triple tree) would work as it is easier to mess with to me.

Thanks,

The forks are flush..Dont have any more adjustment space.

 

[gkotlin]

Garrison;89907 wrote: Wanna spend money? Get the shock.
Most 600's run 180/55's and they're ideal. The 190/60 shouldn't be that much of a change since those two numbers are in fact a ratio.
Just the opposite.

Dale has it correct with his numbers.
180 x 55 = 99mm tire sidewall
190 x 60 = 114 tire sidewall

The 55 and 60 are percentage of sidewall height to tire width. So a theoretical 100/70 means the tire is 70 percent as tall as it is wide. Or 70mm in this example.

unclejesse;89913 wrote: If you do not want to buy a really expensive shock.. Just buy a spacer for your stock one to raise it up a little bit..

You actually need to lower the rear end, not raise it. Or you can raise the front end. But you've said there is no more adjustment.

 

[unclejesse]

gkotlin;90005 wrote:
You actually need to lower the rear end, not raise it. Or you can raise the front end. But you've said there is no more adjustment.

Correct.. :agree:

:banghead::banghead::banghead:

 

[NoBull]

You can go a couple of millimeters higher on the front than flush.

BUT if you're ruining your trackdays are you really saving money? Sometimes you have to put things into perspective.

 

[sobottka]

:agree: :doh:

 

[Wink]

What Greg said.

 

[kawlreaper]

NoBull;90031 wrote: You can go a couple of millimeters higher on the front than flush.

BUT if you're ruining your trackdays are you really saving money? Sometimes you have to put things into perspective.

Exactly.

I am still kinda torn on what I should do..DO you think switching to a 190 55 or should I just go back to a 180?

 

[zangman]

I've been running the 190's on my 636 without issues but I also have the forks resprung and an Ohlins on it. I dropped the forks on teh front to get more turnability back and no other adjustments on the rear. In about a month I'm going to part it so check the classifieds if interested in any of the stuff.

 

[JGardy_781]

NoBull;90031 wrote: You can go a couple of millimeters higher on the front than flush

I used to ride the old, pre-N-tec KR106/108 slicks in 125/80 195/65(?) or whatever they were with the rear tire that grew at speed - basically got the same thing you noticed, when not adjusting the bike for the geometry alterations that the tire selection made. I'd get really nasty head shake that would get worse starting at the timing/press tower all the way to the braking zone at end of the main straight at Summit Main. I did what Finn said - raised the front end (tubes down through the triples) to accommodate the tire growth of the old rear tire at speed...

I consulted with those that know more than I, and arrived at the tube tops being 5mm below the flat of the triple clamp on a 2002 GSXR750, from roughly 3mm above with a different set of tires - a pretty substantial change, all things considered. That and a damper with a tightened up low-speed circuit.

/j

 

[alphamale]

I've got a 200 rear NTEC 211 race tire on the rear of my R6.... Slightly slower turn in, but beautiful corner exit. :-D

 

[gkotlin]

JGardy_781;90373 wrote: I used to ride the old, pre-N-tec KR106/108 slicks in 125/80 195/65(?) or whatever they were with the rear tire that grew at speed - basically got the same thing you noticed, when not adjusting the bike for the geometry alterations that the tire selection made. I'd get really nasty head shake that would get worse starting at the timing/press tower all the way to the braking zone at end of the main straight at Summit Main. I did what Finn said - raised the front end (tubes down through the triples) to accommodate the tire growth of the old rear tire at speed...

I consulted with those that know more than I, and arrived at the tube tops being 5mm below the flat of the triple clamp on a 2002 GSXR750, from roughly 3mm above with a different set of tires - a pretty substantial change, all things considered. That and a damper with a tightened up low-speed circuit.

/j

I also swapped to a rear tire that grew at speed. Get it sorted. A damper is crutch not a fix in this case. It will help when you get light head shake. It could save you when you get excessive head shake. But if you get bad head shake because of setup and not occasional track irregularities or randomly, you need to fix the problem. Raise the front end, lower the rear end, but get with someone to sort it out.

 

[Court Jester]

kawlreaper;89902 wrote: Hey all -

I had an acquaintance who was selling his Dunlop take-off's pretty cheap. So me, being the poor person that I am, thought it was a chance to save a little cash bought a couple sets.

Well here's the issue. I am riding a 03 636 which used to have 180's on it. The tires that I bought are 190 60's..REALLY TALL. I had my front/rear suspension re-done with race-tech by a shop near me. I knew I had to adjust it for the tire but I didnt know by how much. WELL, I did a trackday at Summit Main and at full acceleration, I got a LOT of front end wobble. Id adjust my dampener but then I couldnt turn the bike..My suspension guy said that I don't have enough trail. So, we took 5mm off the spacer off the rear shock and tried that. It helped but I dont believe not enough. I went to NJMP - Lightning and at the straightaways, I could feel the wobble. Not even to mention I was a little hesitant to hit it...Im leaning forward a lot more to keep pressure on the front but why am I changing the whole bike around for the tire?

SO, here's what Im thinking. Go to a tire that's not as tall at the 60 profile. From what I am understanding, a lot of 600's are running 190-55's or 190-50's. Also, MAYBE getting a real rear shock (Penske ot Ohlins) and going that route.

Is anyone running into this same problem? WHy did I go to a 190? TO SAVE MONEY!! Any recommendations?

I have a zx6, 636, and an R6 and have ran 180's only once. Outside of that, 190's and 195's do the trick. You'll just have to fiddle with the suspension for a bit to get it dialed in all proper like.

 

[kawlreaper]

Court Jester;90550 wrote: I have a zx6, 636, and an R6 and have ran 180's only once. Outside of that, 190's and 195's do the trick. You'll just have to fiddle with the suspension for a bit to get it dialed in all proper like.

Are you running the 190 60's or 55's? How much tweaking did you have to do? Do you have stock suspension? What about the rear spacer? I took off 5mm. Did you take off any more?