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Discussion Starter · #1 ·
I'm a trackday rider and thinking about going up to a 190/55 rear, specifically the Pirelli Super Bike Pro. I'm currently running a 180/55 BT003RS with a 640mm OD and can't find the Pirelli's.

To any of you who's made this change(doesn't have to be with the stated tires), did you adjust your eye to eye shock lenghth or drop your forks any to compensate for the taller tire. If so, how much of a change should I expect to make.

Currently:
Fork tubes: 15mm's from the top of clamp to the top of fork cap
shock: 335mm eye to eye
 

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Discussion Starter · #3 ·
I didn't change anything, and adding a bit of height on the back helps turn in.
Thanks, I found this yesterday from a Dunlop Rep also. If I will need to make an adjustment, will it be best to adjust the front or drop the rear or does it matter.
 

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I'm a trackday rider and thinking about going up to a 190/55 rear, specifically the Pirelli Super Bike Pro. I'm currently running a 180/55 BT003RS with a 640mm OD and can't find the Pirelli's.

To any of you who's made this change(doesn't have to be with the stated tires), did you adjust your eye to eye shock lenghth or drop your forks any to compensate for the taller tire. If so, how much of a change should I expect to make.

Currently:
Fork tubes: 15mm's from the top of clamp to the top of fork cap
shock: 335mm eye to eye

Your #'s don't make sense ...by 640mm od I'm assuming you mean diameter. Even so...that # is quite a bit larger than the # I get with my rim (it has 190 on it and measures 622 mm) .
Once you figure out the right height adjustment just lower the shock length(as Dave Moss says in the above vid.) Something else to consider...if the tire height is significantly taller (mine was) you might need to change gearing to compensate for the taller tire (I went +1 in back).
 

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Discussion Starter · #6 ·
Your #'s don't make sense ...by 640mm od I'm assuming you mean diameter. Even so...that # is quite a bit larger than the # I get with my rim (it has 190 on it and measures 622 mm) .
Once you figure out the right height adjustment just lower the shock length(as Dave Moss says in the above vid.) Something else to consider...if the tire height is significantly taller (mine was) you might need to change gearing to compensate for the taller tire (I went +1 in back).
That isn't my measurement, I got it from Bridgestone's website and understood it as the outside diameter. Also, I take it that their measurement was from a tire mounted and air'd-up. Is that how you got 622mm and what tire is that off of?

What I've concluded is to make the swap and adjust accordingly. Posting here I was hoping to run across somebody that swapped those exact tires giving me tips on what change's to expect. Over the last few trackdays I've been dropping the front seeking a better turn-in. The extra height from the 190 may put me in the sweet-spot.
 

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That isn't my measurement, I got it from Bridgestone's website and understood it as the outside diameter. Also, I take it that their measurement was from a tire mounted and air'd-up. Is that how you got 622mm and what tire is that off of?

What I've concluded is to make the swap and adjust accordingly. Posting here I was hoping to run across somebody that swapped those exact tires giving me tips on what change's to expect. Over the last few trackdays I've been dropping the front seeking a better turn-in. The extra height from the 190 may put me in the sweet-spot.
The 622mm is the diameter (or how tall the tire is) that's why I say your number doesn't make sense...the circumferance will be a much larger number.
I run Pirelli SC's (the pro slicks have a similar profile).
(I have a 10mm shim on the rear shock with the forks flush with triples).
Turn is is great and it's realatively stable too (I don't even run a damper).
 

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ANY tire model or manufacturer change should be correctly measured and the geometry changed to compensate for the differences.

So you should keep notes of the OD of your tires, and the geometry settings on your bike. Then if you change, measure the new tires and adjust accordingly if you want the bike to react as it did before.

If the new rear is say 10mm larger, you will lower the rear 5mm NOT 10 if it's 10mm smaller you raise the rear 5mm it's always half the measurement.
 

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Discussion Starter · #9 ·
ANY tire model or manufacturer change should be correctly measured and the geometry changed to compensate for the differences.

So you should keep notes of the OD of your tires, and the geometry settings on your bike. Then if you change, measure the new tires and adjust accordingly if you want the bike to react as it did before.

If the new rear is say 10mm larger, you will lower the rear 5mm NOT 10 if it's 10mm smaller you raise the rear 5mm it's always half the measurement.
Thanks, is there a formula for converting circumference into diameter.

The 622mm is the diameter (or how tall the tire is) that's why I say your number doesn't make sense...the circumferance will be a much larger number.
I run Pirelli SC's (the pro slicks have a similar profile).
(I have a 10mm shim on the rear shock with the forks flush with triples).
Turn is is great and it's realatively stable too (I don't even run a damper).
I'm sorry, I should'a left the OD off the 640mm's which is the tires diameter.

I don't have a measurement off my BT003 but according to Bridgestones website it's supposed to measure 640mm. I wonder if that measurement was taken with it mounted and air'd-up or unmounted? The 622mm's you got off the SC, is that mounted and air'd up or unmounted? I think the Pro Slicks and the SC's are the same size's.
 

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Discussion Starter · #11 ·
that's mounted/aired up.
I'm creating a file with a list of different tire manufacturer's tire's mounted on a 5.5" and 6" rim's, their circumference and diameter to keep for my record's. I'll post it on this forum as I get new measurement's also.

For now I have:
BT003RS 180/55-17 on a 5.5" rim - 2012mm circ - 640mm dia
and will have after this weekend those measurements on a:
Q2 180/55-17 on a 5.5" rim
Q2 190/55-17 on a 6" rim

My next tire after this weekend's trackday will be the superbike Pro 190/55-17 on a 5.5" rim.

Do you have those measurements on the SC to add to the list and the rim size it's mounted on?
 

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the numbers I posted were for a 190 sc mounted on a 5.5 rim (and it was a used tire with about 3/4 tread)
 

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Discussion Starter · #13 · (Edited)
I went with a 190/55 BT003RS on the rear. The front BT003RS had a few more TD's left on it and I didn't want to switch over to the Pirelli SB Pro Slick's until I have to change the set. I figure by the time I reach the wear bars on the front I'll need a new rear. The odd thing I found was the small difference in DIA going from the 180/55 to the 190/55 on my 5.5" rim. The 180 measure's 640mmDIA and the 190 only measured 643mmDIA.
Not making any changes to the shock length I wanted to ride it to see if any were necessary. The only difference I noiticed was as suspected a tad slower turn-in and better mid corner stability.

My objective with this experiment/personal test, I'm wanting to select the best tire size and geometry for my riding style. I've already installed the Ohlins FPK20 with proper rate springs in the fork's and a TTX36 shock with the proper rate spring on the rear. Hoping to get a better turn-in, I've lowered the front in increments of 3mm to now have 15mm's from the top of the fork cap down to the top of the clamp. I'm not having any problem's with high speed stability but are affraid of any bad effects I'll create with dropping the front too much. Does anyone know the stock tube height on this model'd bike? And where do you have your measurements and how does it handle.
 
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