16 inch rims on front and 17 inch rims on back question

[romus]

Hi. I have got 907 swingarm and 17 inch rim to fit as an upgrade from my 16" tyres.
I am wondering if I "really" have to also get a 17 inch front rim?

i.e., if I put a 130/17 -16 tyres on the front 16" rim, bringing the front up to a 17 inch profile and then on the back use 17 inch rims with e.g., a 170/16 -17 tyres will it work just as well as having two 17" rims?

If it would work, it means I can keep using my 16 inch front rim with the new rotors I had put on and existing brakes - at least for a while.

Thanks for any feedback.

Warwick
Paso 906 1990

[ducinthebay]

Hey, its worth a try. Many bikes have different sized wheels front to back, just not a smaller one in front though. I think they did that on some of the GP bikes in the 80's. If anything, it will quicken up your steering a bit. The back wheel is the easier one to change out, and the tire you usually wear out first. Let us know how it works. It will be the 16.5 mod.

Cheers,

[paso750]

Many bikes have different sized wheels front to back, just not a smaller one in front though

i.e. the Ducati F1 had a small front and a bigger rear rim (16" and 18") as did some Honda Fireblades, too. They used 16" front and 17" rear.

G.

[biffo]

hi i have been running a 906 with 16 front and 17 rear for 8 years it works well and is more stable than my 907

[persempre907]

Many bikes have different sized wheels front to back, just not a smaller one in front though

i.e. the Ducati F1 had a small front and a bigger rear rim (16" and 18") as did some Honda Fireblades, too. They used 16" front and 17" rear.

G.

I'd add the first Honda Hornet (which I had got) and many, many bikes...
Ciao

[romus]

hi i have been running a 906 with 16 front and 17 rear for 8 years it works well and is more stable than my 907

What tyres are you using?

[jetboy]

i just shot an email to a guy who is parting his 900ss - if he has a reasonable price for his rear wheel/brakes, as ducinthebay suggests, i might just stick the whole thing on and see how it goes. my 750 is a bit of a frankenbike, it has a an ss swing arm already, so the ss wheel should fit right in. not sure about paso swingarms?

[biffo]

hi romus mich pilot 180 55 17 rear mich pilot 130 70 16 front bike is 944 fuel injected [907motor]with a power commander 86 bhp real goes & copes well hope this is of use

[silverfox]

Your right about the 16s............

My 130/70x16 front (Diablo) is slightly bigger diameter than the 120/60x17 (Diablo) I bought to replace it.

The 16 works fine with a 17 rear (150/60x17 Diablo) and if you bought new discs and are happy with the brakes then there is probably no advantage in changing.

Tony

[romus]

hi romus mich pilot 180 55 17 rear mich pilot 130 70 16 front bike is 944 fuel injected [907motor]with a power commander 86 bhp real goes & copes well hope this is of use

Good to hear.

Do you have any issues of tyre hitting radiator on hard braking?

Some other posters talk about this issue, but anyway my maths has a 120/70 ZR17 closer to the radiator than a 130/70ZR16 by about 6mm if have a 750 or 906 swingarm and 3mm if have 907 swingarm.

According to my maths actually better to not have to extend forks because it would change balance from the original.

----------------------------------------------------------------
For my maths, on a 906 with 907 swingarm (which would drop the back a bit-my guess 3mm) and your tyres, the balance is the same as the original:
78 is original 16" front tyre height and 96 is original 16"rear tyre height
130/70ZR16 [91height], 180/55ZR17 [99height+13rim=112]
Note: 13mm=~half inch height increase of rear 17"wheel.
So, 91-original 78 adds 13mm to front height
So, 112-original 96 adds 16mm to rear height -3mm for 907 longer swingarm (that drops rear a bit) and this is the same balance as the original 906.
----------------------------------------------------------------
For my comparison if I have a 17" rim on the front with a 120/70 ZR17 tyre on.
84 height+13rim=97, which is 6mm more than 130/70ZR16 and would need front forks dropped eg 3mm to even balance out -maybe also to avoid hitting radiator on hard braking.
---------------------------------------------------------------

[ducinthebay]

Be careful of your math. You can not compare different brands or models of tires.

Not all tires are created the same. Even though they may have the same numbers on the side wall, there may be wide variation between different makers, and even different models from the same maker. You need to measure each one of them. Most of the manufacturers supply some of these numbers on their websites, such as diameter and width.

I have seen this on my ST. With the Avon Storm tire on the back, I have only about 10mm of clearance between the tire and the ground with a new tire. When I put on a new Pirelli Strada, there was almost no clearance to the ground. Both tires were sport touring tires and both were 180/55. The Avon actually touched the chain at its widest point, where the Pirelli had 4-5 mm clearance. Very different dimensions, but same purpose tire, and same size.

Anyone have a 'close to new' set of Michelins that they can measure to get the original specs?
Has anyone tried the Avon Azzaro AV 45 - ST 130/80-16 tire? I loved these tires on my ST.(till they stopped making them in my size)
http://www.avon-tyres.co.uk/motorcycle/ ... pecs&id=18
The 130/70 is shorter than the 120/ 80

Cheers,

[romus]

...Not all tires are created the same. Even though they may have the same numbers on the side wall, there may be wide variation between different makers, and even different models from the same maker...

That's interesting - a variation of maybe 5mm in height just because of the brand variations!

Then what seems important is:

1. Which brand/s of 130/70x16 will work without hitting the radiator on hard braking. I then compare other brands to that to check they aren't higher. Eg if biffo's mich pilot 130 70 16 front doesn't hit then that is a starting point.

2. Then, the next step it seems is to plan on experimenting with dropping the forks to fine tune the effect on the balance/geometry when driving. I can use my maths as a starting point for how much I might think I need to drop them.

[biffo]

hi no problems hitting the rad but you have to raise the front mudguard with 10mm spacers

[ducinthebay]

.....Or get a 907/851 fender and brace.

Cheers,

[ducapaso]

hi no problems hitting the rad but you have to raise the front mudguard with 10mm spacers

I think that 10 mm is a bit too high: the front mudguard might touch the side panels!