Bridgestone BT-39 sizes?

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Luciano
Posts: 156
Joined: Sat May 10, 2003 1:01 am
Location: Sweden, Malmö

Bridgestone BT-39 sizes?

Post by Luciano »

Hi.
I have a modded cromstrar front rim with size 2.50x17. And the standard NS400 rear rim is 2.5x17.
With this rim combination i culd fit BT-39:
Front 100/80-17 that has a rec. rim at 2.50 (MEAS. RIM 1.85-2.75).
Rear 120/80-17 that has a rec. rim at 2.75 (MEAS. RIM 2.15-3.00)<- Not perfect...?

I also have a VF1000R rear rim and there i can get a 3.50x17 for the rear
With that I could then use:
Rear 130/70-17 that has a rec. rim at 3.50 (MEAS. RIM 3.00 - 4.00)

But in the last option I need to find someone to make the rim swap and so on.

Is there any problem or concern to use a tire that has a recommended rim with at 2.75 but mount it on a 2.50 wide rim? The tire can be used on rims from 2.15 to 3.00... So it should be almost perfect? I do not care if it is 120 or 130 it is like potato or potaos the most important is to get "stickier" choice to use.
Best regards, Luciano
Torque over the whole register.

Channel Hopper
Posts: 1305
Joined: Thu Sep 23, 2004 5:26 pm

Re: Bridgestone BT-39 sizes?

Post by Channel Hopper »

A tyre fitted on a 2.5 rim will inflate quicker to the right pressure than one on a 2.75 rim as there is about 10% less volume inside the cavity.
Less volume means the tyre will heat up quicker and the pressure will change more between cold and hot, so in this case I would adjust the correct psi when the tyre is warm, not cold.

As you probably are aware, the tyre cross section will have a raised profile on the narrower rim but this shouldn't make a difference you can detect, except on the best track curves.

The tyre tread will also last some 10-15% less time overall, but that shouldn't really matter to you.

I would go for the rim swop, what have you got to lose if you are careful ?

Luciano
Posts: 156
Joined: Sat May 10, 2003 1:01 am
Location: Sweden, Malmö

Re: Bridgestone BT-39 sizes?

Post by Luciano »

Yes you are right. I Will go for the rear wheel modification to get 3.5 Wide rim.

I discovered that i could've
100/90-16M/C 54H TL 2.50
OR
100/80-17M/C 52H TL 2.50
The 16 shuld be the better choise?
Best regards, Luciano.
Torque over the whole register.

Luciano
Posts: 156
Joined: Sat May 10, 2003 1:01 am
Location: Sweden, Malmö

Re: Bridgestone BT-39 sizes?

Post by Luciano »

I found for me a new side effect when you go from 16 to 17 inch:
"you will have a wheel rim a tyre that will be at least half an inch higher(one inch bigger rim will be half an inch top and bottom).Also your bike is set to steer properly with its geometry,so now you will be changing this by 12-13mm to high.So you will need to drop your forks through the yokes 12-13mm to bring things back to normal."
http://www.motorcyclenews.com/MCN/commu ... -id=377148

Any other thoughts?
Best regards, Luciano.
Torque over the whole register.

Alastair
Posts: 1796
Joined: Sat May 25, 2002 1:01 am
Location: Glossop U.K.
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Re: Bridgestone BT-39 sizes?

Post by Alastair »

Luciano wrote:I found for me a new side effect when you go from 16 to 17 inch:
"you will have a wheel rim a tyre that will be at least half an inch higher(one inch bigger rim will be half an inch top and bottom).Also your bike is set to steer properly with its geometry,so now you will be changing this by 12-13mm to high.So you will need to drop your forks through the yokes 12-13mm to bring things back to normal."
http://www.motorcyclenews.com/MCN/commu ... -id=377148

Any other thoughts?
Best regards, Luciano.
Go for a lower profile?

Luciano
Posts: 156
Joined: Sat May 10, 2003 1:01 am
Location: Sweden, Malmö

Re: Bridgestone BT-39 sizes?

Post by Luciano »

Yes you have a point :)
OD (mm)
587 for the 16 inch
594 for the 17 inch
It is only (7mm/2) 3.5mm higher in the front due to the 80 profile.

So it is no issue. I have notice that the problem is rather that to get hold of the 16 inch...
Best regards, Luciano.
100/90-16M/C 54H TL 2.50
100/80-17M/C 52H TL 2.50
Torque over the whole register.

Channel Hopper
Posts: 1305
Joined: Thu Sep 23, 2004 5:26 pm

Re: Bridgestone BT-39 sizes?

Post by Channel Hopper »

Luciano wrote: So it is no issue. I have notice that the problem is rather that to get hold of the 16 inch...

Tbh I wouldn't have thought that a problem, not round here at least, owing to a number of bikes in that era having the same front tyre profile as the NS.
(VT250/VF400/500 etc)

We even have a tyre supplier with them in stock

http://www.bits4motorbikes.co.uk/Tyres/ ... TryeID=218

But then I have a couple of spare wheels with good
tyres on.

Luciano
Posts: 156
Joined: Sat May 10, 2003 1:01 am
Location: Sweden, Malmö

Re: Bridgestone BT-39 sizes?

Post by Luciano »

Channel Hopper wrote:Tbh I wouldn't have thought that a problem, not round here at least, owing to a number of bikes in that era having the same front tyre profile as the NS.
(VT250/VF400/500 etc)

We even have a tyre supplier with them in stock

http://www.bits4motorbikes.co.uk/Tyres/ ... TryeID=218

But then I have a couple of spare wheels with good
tyres on.
Yes the BT-45 is not hard to find as in the URL above.

It is the BT-39 in the 16 inch configuration that is harder to find!

Anybody that has a URL to BT-39 in dimension 100/90-16(M/C 54H TL 2.50)?
Best regards, Luciano
Torque over the whole register.

Channel Hopper
Posts: 1305
Joined: Thu Sep 23, 2004 5:26 pm

Re: Bridgestone BT-39 sizes?

Post by Channel Hopper »


Luciano
Posts: 156
Joined: Sat May 10, 2003 1:01 am
Location: Sweden, Malmö

Re: Bridgestone BT-39 sizes?

Post by Luciano »

Channel Hopper wrote:In Japan (of course)
http://j-mart.biz/j-parts/index.php?mai ... ts_id=7025
Thank you.
That is great they ship to Sweden to and the page is in English. I have only found pages in Japanese...
Best regards, Luciano.

Edit: Hm the shipping cost as much as the Tyre it self. I will look into if i can find some locally here.
Torque over the whole register.

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