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Discussion Starter #1
I have not confirmed this yet, but i believe that the 65 profile tyres on the front end of my '01 ZX6R is spensive. I was surfing on the net and found an article or post or summing that went on to say that this dude fitted a 70 profile and dropped (raised?)[:I] the forks 7mm thru the head set!! is this possible? how will it effect the handling?[?]

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The section height of a 120/70 tire is 6 mm greater than that of a 120/65 tire. You can maintain the stock ride height by raising the forks that much through the triple clamps.

The 120/70 tire gives better straight-line stability, grip at lean, and bump absorption, but also slower steering and less feel.

But the 120/70 tire often costs more than the 120/65 tire. For inexpensive tires, check out ronayers.com or swmototires.com.
 

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Actualy Rob Lee it's the other way round. The higher the aspect ratio (height as a percentage of the width) the steaper the tyre becomes. Which gives it a more triangular profile. This allows the tyre to fall into corners which gives the bike faster steering. It also gives more grip in the corner because there is a larger contact patch with the pavement. Think of a triangle standing on one of it's pionts. The draw back is less straight line stability because the tyre is riding on less rubber. A 120/70 is the most common used front profile by racing teams around the world. A 120/60 is the opposite of the 120/70 and a 120/65 is some what of a comprimise.

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both ends up,

Assuming identical compound and construction, a 120/65 tire has a shorter, stiffer sidewall than a 120/70 tire. A stiff sidewall deflects less, aiding steering but offering a smaller contact patch at lean and inferior bump absorption.

Even with identical ride heights, the 120/65 tire provides quicker steering and better feel. The 120/70 tire provides better bump absorption, a larger contact patch, and more grip at lean.

Several folks have tried a 120/70 instead of a 120/65 tire. It does not take long to learn that the 120/70 tire steers slower. For an example, check out this thread.
 

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Discussion Starter #5
Thanx for the input. I undersand the pitfalls - well i guess i should stick to 65's (can get bt010) but i have the option of the 70 in the form of a BT012. decisions decisions . . . . . but it is always nice to try sumthin different, can always get the 010 if the 012 is crappy.

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Rob Lee, I dont disagree with what you have said, but if you change the ride height (front or rear) to compensate for the taller profile tyre, a 70 will always turn quicker and hold a line better than the 60 profile. What I mean by turning quicker is the force it takes to push and pull on the clip-ons to initiate a bike into a turn. What you are doing by changing the profile to a 70 is giving the front end more trail, that's why the bike will turn slower.
By the way, rake can not be affected enough buy the profile of the front tyre to make a difference in the way a bike turns. To change the rake enough to have an effect on a bike you would need to replace the head bearings with angled ones or you could bend the headstock to a new angle in a frame jig. The trail is what you want to look at when it comes to front end steering. Trail can be altered in three ways: rear ride height, deck height, and fork offset.
You could always leave the front brake on slightly when entering a corner for quicker steering. This will give you a shorter trail figure. Remember a bikes geometry is always changeing. Weather your accelerating and braking.

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I went to a 70 from a 65 because thats all I could get my hands on. and to be honest with you I cannot really tell the diff. But again I'm no Bostrom either.
 

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Originally posted by both ends up

Rob Lee, I dont disagree with what you have said, but if you change the ride height (front or rear) to compensate for the taller profile tyre, a 70 will always turn quicker and hold a line better than the 60 profile.
both ends up,

After you adjust the ride height to allow for the higher profile tire, it will still have a taller sidewall. At identical ride heights, given the same compound and construction, the tire with the taller sidewall steers slower.

Check out this thread on r1-forum.com.
 

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Rob Lee, your saying a bike with a 60 front will steer quicker when it's already leant over. That's not what I'm saying. What I'm saying is their is less work to initiate the bike into a corner because the tyre has a more triangular shape with a 70 front profile. This is what quicker steering is. The sidewall has no effect on how the tyre first reacts to a steering input. Here's an example. An '02 R6 uses a 120/60 front, it's trail is 81mm and it has a short wheelbase of 1379mm. An '02 GSX-R 600 uses a 120/70 front, it's trail is 96mm and it has a longer wheelbase of 1400mm. The reason Yamaha went with a 60 profile front is to help it with stability because it has very aggressive geomeretry which can lead to a little headshakeing under heavy acceleration. The reason Suzuki went with a 70 profile front is to help it turn quicker because it's chassis has greater stability.
The only reason Suzuki fit a factory steering damper is because they where smart enough to cover there ass if the ignorant public started to complain about a little headshake. Tip: Remove it.

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Originally posted by both ends up

Rob Lee, your saying a bike with a 60 front will steer quicker when it's already leant over.
both ends up,

No, I am not. You are putting words in my mouth.

At identical ride heights, given the same compound and construction, the tire with the taller sidewall steers slower. That means that at identical ride heights, given the same compound and construction, the tire with the taller sidewall turns in slower. In other words, the taller tire takes more effort to initiate the turn. The taller tire is more stable, without discrimination. That means it is more stable on the straight and in the corner, including at turn-in.

I have shown a thread on this forum where someone installed a taller tire and found that it turned in slower. I have shown another thread on another forum that supports this argument. If you do not believe me, re-read these threads with an open mind.

You are mistaken, but I will no longer try to correct you. You may have the last word in this thread if you want it.
 

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".....a smaller contact patch at lean...." check your quote at 10:28:34. Your threads are just other people's opinions, dont listen to what they say. Use your own head. Check with a real race team or call a local race team and listening to what they have to say.
Originally posted by Rob Lee

both ends up,

Assuming identical compound and construction, a 120/65 tire has a shorter, stiffer sidewall than a 120/70 tire. A stiff sidewall deflects less, aiding steering but offering a smaller contact patch at lean and inferior bump absorption.

Even with identical ride heights, the 120/65 tire provides quicker steering and better feel. The 120/70 tire provides better bump absorption, a larger contact patch, and more grip at lean.

Several folks have tried a 120/70 instead of a 120/65 tire. It does not take long to learn that the 120/70 tire steers slower. For an example, check out this thread.
www.bothendsup.com
 

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Discussion Starter #12
I scrubbed the type in today, have not noticed any diff yet, will be able to tell tomorrow . . . . . . [8D]

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Discussion Starter #13
Yeah well... I Scrubbed the tyre in on Sat:), took it for a decent ride on Sunday and crapped myself[:0]..... Went into a corner at Approx. 130 kmph - no prob, did not notice anything out of the ordinary, as i gained confidence in the corners i pushed harder until at aprrox 150 kmph it felt like the front wheel was riding over gravel (bumpy)!!! the friggin tyre was not balanced:(!!!!! on top of which the people who put the tyre on scratched my rim:(:(:(:( (they did not take the lead weight off before putting it in the machine[}:)][}:)]:(:(!!!). (before the corners i did not go fast on the straights as the local fuzz are having a speeding blitz - they nabbed a blackbird doing 237 on thier rader thingy and went balistic - they actually blocked off the whole freeway to catch him[:0]!! (didn't know hondas could go that fast:D!))

so. After a few choice words were had:D, I took of the wheel off and went back and made them balance and check the wheel, (they have offered to repair the scratch[^]). Took it for a blast tonight on the concreat(?) freeway - seems mutch better, must try it on tar/asphalt.

So far the tyre is not bad (bt012), will try it in my fav corners on the weekend:D:D:D. Am also going to raise the forks through the headset to see what happens with the handling.


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Discussion Starter #14
I dropped the front forks 12mm through the headset and have found the handling in the turns better but stability in the straights a little suspect, not as good as previously. Had no hint of head shakes or tank slappers on the exits of turns on the gas.

Swapped bikes with a friend, twas a 748. Got complimented on how comfortable and easy the 6R was to ride. the 748 cornering was awesome but on the straights very uncomfortable, akin to riding a plank with wheels. suppose u cant have everything... . . .

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Discussion Starter #15
I've ridden a few different bikes now and although the 6r has good handling its starting to feel a bit loose. ie the bike does not feel tight in the corners. Any suggestions??? (i have not yet changed the compression, rebound etc)

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Hi all,

I have a new 03' and have also changed the front and rear tires for BT012's, 70 profile on the front. I also raised the forks 5mm to compensate.

But, I have to say that the bike seems quite nervous in a straight line, esp. on a bumpy road. I would also like to ask any of you that have changed tyres to the BT012 if they have noticed a slight hestitation on the front when 'tipping' in? It feels as thought the profile of the front tyre at the point of 'tip in' is where the tyre changes curvature, as afterwards once in the corner it feels planted. Strange??? Maybe its the tyre that is not suited to the bike? Have any of you mounted Pirelli Supercorsa's or michellin pilot race?

Second point is the bike seems very rigid on the suspension, esp. the rear. Does anyone have any settings for fast road riding? I am 70kg and at the moment the settings are all standard. On bumpy roads, I am coming out of the seat which is not so good when I am going for it ;)

comments?

Paul.
 

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Hi guys,
I just got the NEW Dunlops 208R's in 120-70-17, and 180-50-17. and I have 98ZX6R. and the bike feels AWESOME!!! now!. much quicker steering, more stable!. I did not adjust anything on the bike. so my 98zx6r with 120-60-17, 170-60-17 stock size, Reacted VERY WELL to the new tires and new sizes. so before you go changing suspension settings and height, just test ride it first. and make adjustments accordingly.

98ZX6R
Muzzy full race exhaust system.
 
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