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Bayman
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VBMWMO #8848
Joined: 01/06/2015
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Hello All, been lurking for a bit.. here's my 1st. question,
Has anyone had experience using a 80 profile metric tire to lower height ... not a major issue but it sits just a tad to high for me as I get on & off in certain terrain. The side stand has a extreme lean also and I have to be mindful of this when setting it, center works fine. I've been running 100/90/19 front and 110/90/18 Spitfires. Considering going with Bridgestone bt45 110/80/18 rear that listed as approx.1 inch lower in diameter and staying with a 90 front. Thinking that little bit may help without changing handling. Thanks, Chris

schrader7032
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VBMWMO #7032
San Antonio, TX
Joined: 10/27/2006
Posts: 6427
What year BMW? Certainly

What year BMW? Certainly lowering the tire profile lowers the bike...I'm glad you mention the side stand because that is why I switched from metric to inch-sized tires on my '78. With the metrics, the bike sat nearly vertical on the side stand. Going back to inch-sized tires gave me my lean angle back.

Changing profile affects handling performance...takes more input to move the bike around as it affects trail. Inch-sized tires were spec'd to a certain year then they switched to metric tires. That's why I ask about the year of the bike.

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Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2

Bayman
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VBMWMO #8848
Joined: 01/06/2015
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Kurt, 79 R100T, sorry that I

Kurt, 79 R100T, sorry that I spaced putting that in,
My issue is the reverse of yours, with the metric spitfires it leans to far over on the side stand, but handles great. Now I'm thinkin the stand may be bent...? Also I was also trying to be a little more flat footed, but not at the cost of losing handling.

schrader7032
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VBMWMO #7032
San Antonio, TX
Joined: 10/27/2006
Posts: 6427
I'm not sure what side stand

I'm not sure what side stand you have on your '79...might be the same as my '78. I assume yours is still stock. I don't think that the original side stand would have leaned that much. So, I would suspect there's something wrong with yours. I do know that they changed the frame attachment later on, maybe in the early '80s that were easily bent. That said, the side stands were really not meant for supporting a lot of weight...I've never sat on my bike while on the side stand. All my side stand has had to support is the weight of the bike.

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Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2

mark_weiss
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Arizona
Joined: 11/17/2013
Posts: 171
I've ridden with a 110/80

I've ridden with a 110/80 rear tire. It works fine. If you would like to preserve the handling, while the change may be barely notable, it is not difficult to lower the front end a matching small amount. Your speedometer will be even farther off than it already is though.

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Mark
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Bayman
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VBMWMO #8848
Joined: 01/06/2015
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Thanks for that Mark, the

Thanks for that Mark, the 110/80 18 is available in the Bt-45 but 100/80 19 front is a rare one. Avon has it in the Roadrider, may go with that combo but will run the 80 rear with the 90 frt. first a while since that spitfire still has some miles left. Not Gonna make this change till next Spring. How did you know my speedo was off....Ha
Chris

mark_weiss
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Arizona
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speedo

Bayman wrote:

How did you know my speedo was off....Ha
Chris

Because you have a BMW!

I have a 2008 Buell which read dead-on when checked with GPS. That is, until Buell released a software update. From then on the speedo read 3 mph fast.

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Mark
qualitycycleservice.com

schrader7032
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VBMWMO #7032
San Antonio, TX
Joined: 10/27/2006
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Speedos read fast right out

Speedos read fast right out of the factory. There was a service bulletin that described how the speedo could be no more than a specific amount too fast. I'm sure the idea was to "protect" the rider...aka BMW...from getting a ticket. If it was slightly fast and you were actually using the speedo readings, you would actually be a bit slow.

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Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2

Bayman
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VBMWMO #8848
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This speedo seems to be

This speedo seems to be around 8- 10mph over but the odo reads dead on when using a measured mile...?

schrader7032
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VBMWMO #7032
San Antonio, TX
Joined: 10/27/2006
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That sounds about right...the

That sounds about right...the odos were generally pretty good. The bulletin said the speed could be no more than 10% times the actual speed plus 2.4 mph. Of course, having the proper relationship between the final drive, speedometer W factor, and rear tire diameter is what's needed to maintain anything close to the proper speed.

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Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2

2valve
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Glen Innes N.S.W Australia
Joined: 04/05/2007
Posts: 173
Hi

Hi Chris. Try a set the Avon Roadrider tires. Have a set on my R90 , they made a huge improvement in the handling department, if this is what your after. They are also correct dimensions for your speedo.

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