Slight tyre difference

[A100man]

I'm about to change the perished Avon roadrider (130/80 r18) on my old FZ750 for a lower profile Michelin pilot activ 130/70 r18. Apart from a slight gearing change am I likely to notice any difference?
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Now: A100, GT250A, XJ598, FZ750

Then: Fizz, RS200, KL250, XJ550, Laverda Alpina, XJ600, FZS600

[jaffa90]

Going from a 104mm side wall tyre to a 91mm side wall tyre will make your bike more rapid
If not declared to your ins com as a modified bike you may be hung drawn and quartered or sent to prison.

[weasley]

Theoretically:

The 12.5% gearing change will lead to a 12.5% reduction in speed for a given engine revs, so you'll need to rev higher to achieve the same road speed. This will also reduce fuel economy, both because the gearing has reduced and because you'll probably ride at higher revs more of the time.

It will lower the rear of the bike by 13mm, which will slacken the steering geometry by increasing the rake and trail. It will reduce ground clearance and maximum lean angle. It will sit more upright on the side stand. Your headlight aim will be too high. All of this might be offset somewhat if you are able to increase the preload on the rear spring (but this might then set your sag at the wrong position).

Acceleration will improve, at the expense of top speed. You may find handling changes, due to the change in profile of the rear tyre and how it drops into and holds a lean angle.

Theoretically.
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Yamaha XJ600 | Yamaha YZF600R Thundercat | KTM 990 SMT | BMW F900XR TE

[stinkwheel]

Remember both of these are bias belt tyres.
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[A100man]

[stinkwheel]

[A100man]

Hmm BT45 up front which i think is the same type.
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Now: A100, GT250A, XJ598, FZ750

Then: Fizz, RS200, KL250, XJ550, Laverda Alpina, XJ600, FZS600

[stinkwheel]

[weasley]

[A100man]

Thanks all - I'll press on with it and let you know how it goes..

Cheers

J
____________________
Now: A100, GT250A, XJ598, FZ750

Then: Fizz, RS200, KL250, XJ550, Laverda Alpina, XJ600, FZS600