The Bike Show GTR1400 Road Test

[maxtog]

So 55 series rear. Stock size on the front?

That is the theory.  The larger diameter tire will correct speedo error (3.2%) and the profile is more rounded, allowing easier/faster lean.  Sounded interesting, but in my case, I can't afford ANY height increase (in this case, 0.85",22.5mm; which divided by 2 is about 1/4 inch at the center of the bike), so when I switched to the great Mich PR3-GT I kept the 50.

[Poseidon]

That is the theory.  The larger diameter tire will correct speedo error (3.2%) and the profile is more rounded, allowing easier/faster lean.  Sounded interesting, but in my case, I can't afford ANY height increase (in this case, 0.85",22.5mm; which could be almost half an inch at the center of the bike), so when I switched to the great Mich PR3-GT I kept the 50.

Why no height increase? Seems like there would be plenty of room for a taller tire.

[Rubber_Snake]

Why no height increase? Seems like there would be plenty of room for a taller tire.

Max has short legs (As do I).  That’s why, silly! 

[mikeyw64]

That is the theory.  The larger diameter tire will correct speedo error (3.2%) and the profile is more rounded, allowing easier/faster lean.  Sounded interesting, but in my case, I can't afford ANY height increase (in this case, 0.85",22.5mm; which could be almost half an inch at the center of the bike), so when I switched to the great Mich PR3-GT I kept the 50.

Presuming you're referring to the built in factory "error" on the speedo then correcting that will throw your odometer reading off as that is generally calibrated to be accurate


Certainly over here "European law (ECE-R39) says speedometers cannot show speeds less than the actual speed, and they must never show more than the 110 per cent of actual speed plus 4 km/h. So, under those rules, a car could be moving at 100 km/h, but the speedometer could legally display as high as 114 km/h."

[maxtog]

Presuming you're referring to the built in factory "error" on the speedo then correcting that will throw your odometer reading off as that is generally calibrated to be accurate

Here the bikes read about 3% high, which is typical for most vehicles.

[mikeyw64]

Here the bikes read about 3% high, which is typical for most vehicles.

thats what I asked/said

[Rhino]

Here the bikes read about 3% high, which is typical for most vehicles.

Every bike I've ever checked does that (another crazy and annoyed entry). But when I have checked cars, they are much more accurate. At least according to gps.

[just gone]

..... (in this case, 0.85",22.5mm; which could be almost half an inch at the center of the bike)....

That seems high (pun intended), max' did you remember to divide by 2? (since only half of the increased diameter is below the axle) I came up with .375" at the rear axle which would be what?.... 3/16"-1/4" at the pegs?

[maxtog]

That seems high (pun intended), max' did you remember to divide by 2? (since only half of the increased diameter is below the axle) I came up with .375" at the rear axle which would be what?.... 3/16"-1/4" at the pegs?

Sorry, you are correct.  I did realize I made that mistake shortly after posting and meant to correct it and got distracted and forgot.  Yes, it should be divided by two.  So it is about 1/4" at the pegs/legs (if you also properly adjust the front by the same amount so as not to change the handling).  In my case, that is huge.  Most people won't care.

I have corrected the other post.  Thanks

[maxtog]

Max has short legs (As do I).  That’s why, silly!

Exactly.  It won't matter to most people... only those with short legs.  1/4" can make a HUGE difference in such cases.

[Poseidon]

Exactly.  It won't matter to most people... only those with short legs.  1/4" can make a HUGE difference in such cases.

Sorry Max. That thought never crossed my mind. I was thinking maybe you had done some mods that would make clearance an issue. I fall into the "it wouldn't matter" category.

[just gone]

So it is about 1/4" at the pegs/legs (if you also properly adjust the front by the same amount so as not to change the handling).

Wait... WHAT?...... max' you've per-snickered me.

I don't think anyone raises the front end with the 55 series rear tires, in fact I've often thought that most of the reported turn in improvement came from the slightly changed steering geometry from raising the rear.  and...and... If you do raise the front end a corresponding amount at the front, why would the foot peg height increase be any less than the rear axle height increase?

[maxtog]

Sorry Max. That thought never crossed my mind. I was thinking maybe you had done some mods that would make clearance an issue. I fall into the "it wouldn't matter" category.

No prob.  But yes, clearance CAN be an issue too, if the bike was lowered.  It is something to consider.  In my http://www.zggtr.org/index.php?topic=260.0 thread, when I talk about how much the bike can be safely lowered, it is assumed with STOCK tire sizes.  If you put on a larger diameter rear tire, that will increase the probability of the tire hitting the frame.... and that could be very dangerous.

Without lowering the bike, there is plenty of room for a larger (taller) rear tire.

[just gone]

Sorry Max. That thought never crossed my mind.

Dang long legged flat footed show off! 

[maxtog]

Wait... WHAT?...... max' you've per-snickered me.

I don't think anyone raises the front end with the 55 series rear tires, in fact I've often thought that most of the reported turn in improvement came from the slightly changed steering geometry from raising the rear.

That is true.  Most people do not, and I suspect that does have something to do with what some people might like.  But I suspect one of the large changes people notice is from the profile of the tire.  The 55 is more rounded.  I am not going to comment that it is a good idea to slant the bike more forward (by raising the rear and not the front, or lowering the front and not the rear)- I just don't know.  That is why I recommend always keeping the front and the same stock ratio unless you know what you are doing.  I certainly don't 

Oh, and I wouldn't necessary characterize raising the back 11.5mm OR lowering the front by 11.5mm as "slightly" changing the geometry.  According to my friend who knows a lot more than I do about such things, he says that is a pretty significant (moderate) change.

  and...and...If you do raise the front end a corresponding amount at the front, why would the foot peg height increase be any less than the rear axle height increase?

I think we are saying the same thing (but it has been a long day at work)  If you put a larger tire on the rear by, say, 23mm larger diameter,  and do NOT adjust the front, the center of the bike will rise by 1/2 of 1/2 of 23mm which is 5.75mm.  (+11.5 rear, +0 front, = 5.75mm center).  If you do adjust the front, raising it 11.5mm to be neutral/same handling, then it will raise the center of the bike by 1/2 of 23, which is 11.5mm.  (+11.5 rear, +11.5 front, = 11.5mm center).  Whew

[Poseidon]

Dang long legged flat footed show off! 

You forgot bent knee. 

[just gone]

  Whew.

Well there we can agree!. 

I'm sure some engineering type or even a H.S. student that's recently taken trig could tell us exactly what the rake and trail would change to, but I don't know enough about steering geometry to interpret what the numbers really mean. I resisted the 55 series for quite awhile, somewhat worried that there might be some sort of steering instability induced under certain conditions by the changes.  I haven't heard of anybody that's had any such experiences, and lots of users, so with the turn in improvement, ease of using the center stand, more accurate speedometer, and theoretical extra milage, I've switched to become one of the the 55ers.

[gPink]

The main drawback with the 55 is the reduction of the contact patch. I think I'm going back to a 50 series.

[just gone]

You forgot bent knee. 

   

[maxtog]

what the rake and trail would change to, but I don't know enough about steering geometry to interpret what the numbers really mean. I resisted the 55 series for quite awhile, somewhat worried that there might be some sort of steering instability induced under certain conditions by the changes

Well, and if you don't like it, just raise the front 11.5mm!