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Discussion Starter #1
Today i swapped out my old Michelin 190/50 ZR17 2CT for a Michelin 190/55 ZR17 2CT.

I was wondering what peoples input would be on the gearing ratio for this taller tyre.

I am currently running stock 16/42 sprockets.

I mainly use my blade for commuting and pleasure riding however i intend on going to my local track "Castle Combe - UK" for a few track days during the summer.

I will put some pictures up tomorrow :smilebig:

Cheers guys.
 

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Today i swapped out my old Michelin 190/50 ZR17 2CT for a Michelin 190/55 ZR17 2CT.

I was wondering what peoples input would be on the gearing ratio for this taller tyre.

I am currently running stock 16/42 sprockets.

I mainly use my blade for commuting and pleasure riding however i intend on going to my local track "Castle Combe - UK" for a few track days during the summer.

I will put some pictures up tomorrow :smilebig:

Cheers guys.

The 5% in profile is unlikely to make much difference to the gearing.
What is the highest speed you expect to see at that particular circuit on a track day?
Optimal gearing for a particular circuit would start with putting your top speed at peak power in top gear, then fettle from there to suit the corners.
 

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What year/model blade do you have? One important thing to remember is that you have to either correct the speedometer or mentally compensate for the difference constantly. Any time you change the gearing, unless it is front-speed-read, you will change your speedo readout. Since it is a blade, I would assume it has a fair bit of power to begin with (my '02 954 certainly isn't lacking), so a gearing change is completely optional. I left my gearing alone when I replaced my chain and sprockets.

That being said, if you want faster acceleration I would go with one or two teeth up in the rear. If you are looking to really get snappy acceleration and pull it up easily, one down up front and two up in the rear (equal to about 5 up in the rear) will allow you to use the stock chain length (usually) and make for a splendidly more-torquey feel.

I don't think that going from a 50 ratio to a 55 ratio height tyre would require a gearing change by default as it is only a couple cm difference in tyre height.
 

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^^ As always BR beats me to it!!......
 

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Discussion Starter #5
Thanks for the quick replies.

I am unsure of the top speeds will be hitting at castle combe as i have never participated in a rack day there before however i heard riders train here for the Isle of Man TT so i imagine its pretty quick. 130mph maybe?

I have a 2001 929 in blue, red and white Euro colours. Its pretty much stock except a scopion slip on and a K&N filter. I am happy with the performance of the bike but theres always room for quicker acceleration!

I mainly use the bike for commuting to work in the week but then like to throw it around the country roads where i live on the weekends. Unfortunatly i didnt get a chance to test the new tyre with the stock gearing today as i was stuck under my car replacing a couple of CV Boots, bloody messy job.

Im going to see how she feels with stock sprockets before i rush into changing the gearing ratio. But if i do want to improve the acceleration and not make the bike too prone to pulling up it sounds like a 16 up front and 44 on the rear would be good??

Cheers for the help bladeracer and RRDemon.
 

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ive done a couple of track dayz on my 929 fireblade of the same colour at cadwell and snetterton. i have just reduced one tooth on the front sprocket. i was happy with the result its was fine for road riding too. cheaper than replacing the rear, you would have to add about three teeth on the rear for the same result. also have fitted a speed healer to get correct speedo reading. i also have done some santa pod runs aswell and was happy with the results. have'nt tride a 55 profile tyre on the rear yet. so cant comment on that can't imagine it will make much odds. i was thinking of trying castle combe this year too.
 

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^^ hfb hit it right there. One down in the front is equal to about 3 up in the rear. It is usually a little noticeable bump in acceleration without killing top-end or streetability of it. I won't change my gearing on my 954 because the front end already seems to be allergic to pavement with the sudden application of throttle....
 
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